geochronology of cenozoic rocks in the bodie hills ...geochronology of cenozoic rocks in the bodie...
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U.S. Department of the InteriorU.S. Geological Survey
Data Series 916
Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
Cover. Steeply flow-banded lava dome, trachyandesite of Willow Springs, east of Warm Spring in the Bodie Hills, California.
Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
By Robert J. Fleck, Edward A. du Bray, David A. John, Peter G. Vikre, Michael A. Cosca, Lawrence W. Snee, and Stephen E. Box
Data Series 916
U.S. Department of the InteriorU.S. Geological Survey
U.S. Department of the InteriorSALLY JEWELL, Secretary
U.S. Geological SurveySuzette M. Kimball, Acting Director
U.S. Geological Survey, Reston, Virginia: 2015
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Suggested citation:Fleck, R.J., du Bray, E.A., John, D.A., Vikre, P.G., Cosca, M.A., Snee, L.W., and Box, S.E., 2015, Geochronology of Cenozoic rocks in the Bodie Hills, California and Nevada: U.S. Geological Survey Data Series 916, 26 p., http://dx.doi.org/10.3133/ds916.
ISSN 2327-638X (online)
iii
Appendixes[Available for download at http://pubs.usgs.gov/ds/916/]
1. Analytical results of CO2-laser-fusion and resistance-furnace incremental heating 40Ar/39Ar experiments (Menlo Park lab) for samples of the Bodie Hills volcanic field
2. Analytical results of furnace incremental heating 40Ar/39Ar experiments (Denver lab, Snee) for samples of the Bodie Hills volcanic field
3. Analytical results of CO2-laser incremental heating 40Ar/39Ar experiments (Denver lab, Cosca) for samples of the Bodie Hills volcanic field
Contents
Introduction.....................................................................................................................................................140Ar/39Ar Analytical Methods ........................................................................................................................8K-Ar Analytical Methods ..............................................................................................................................9Data.................................................................................................................................................................. 9Acknowledgments .........................................................................................................................................9References Cited..........................................................................................................................................25
Figures 1. Map showing location of and major physiographic features near the Bodie Hills
volcanic field ..........................................................................................................................7 2. Locations of samples with 40Ar/39Ar age determinations shown on a simplified
geologic map of the Bodie Hills volcanic field, California and Nevada .....................10 3. Locations of samples with K-Ar age determinations shown on a simplified geologic
map of the Bodie Hills volcanic field, California and Nevada ......................................12
Tables 1. Map location numbers for 40Ar/39Ar geochronology samples from the Bodie Hills
volcanic field, California and Nevada ................................................................................2 2. Map location numbers for K-Ar geochronology samples from the Bodie Hills volcanic
field, California and Nevada ................................................................................................5 3. Summary compilation of geochronologic data for samples of the Bodie Hills volcanic
field, California and Nevada ..............................................................................................14
Introduction
The purpose of this report is to present geochronologic data for unaltered volcanic rocks, hydrothermally altered volcanic rocks, and mineral deposits of the Miocene Bodie Hills and Pliocene to Pleistocene Aurora volcanic fields of east-central California and west-central Nevada. Most of the data presented here were derived from samples collected between 2000–13, but some of the geochronologic data, compiled from a variety of sources, pertain to samples collected during prior investigations. New data presented here (tables 1 and 2; Appendixes 1–3) were acquired in three U.S. Geological Survey (USGS) 40Ar/39Ar labs by three different geochronologists: Robert J. Fleck (Menlo Park, CA), Lawrence W. Snee (Denver, CO), and Michael A. Cosca (Denver, CO). Analytical methods and data derived from each of these labs are presented separately.
The middle to late Miocene Bodie Hills volcanic field (BHVF) is a large (>700 km2), long-lived (~9 million years [m.y.]), episodic eruptive complex (John and others, 2012) in the southern segment of the ancestral Cascades arc (du Bray and others, written commun., 2015) north of Mono Lake and east of Bridgeport, California (fig. 1). The field is near the west edge of the Walker Lane and the northwest edge of the Mina deflection where structures related to these shear zones may have localized magmatism. The Walker Lane (fig. 1) is a broad, northwest-striking zone of right-lateral shear that accommodates right-lateral motion between the Pacific and North America plates; the Mina deflection constitutes a 60-km-long right step in the Walker Lane (Faulds and Henry, 2008; Oldow, 1992, 2003; Stewart, 1988). The Bodie Hills volcanic field includes at least 31 volcanic rock units erupted from 21 significant volcanic eruptive centers.
Four trachyandesite stratovolcanoes developed along the margins of the volcanic field and numerous silicic trachyandesite to rhyolite flow dome complexes erupted more centrally. Volcanism in the Bodie Hills volcanic field peaked at two periods, ~15.0 to 12.6 million years before present (Ma) and ~9.9 to 8.0 Ma, which were dominated by emplacement of large stratovolcanoes and large silicic trachyandesite-dacite lava domes, respectively. A final period of small-volume silicic dome emplacement began in the western part of the volcanic field at ~6 Ma and culminated at ~5.5 Ma (John and others, 2012).
Compositions of Bodie Hills volcanic rocks vary from ~50 to 78 weight percent SiO2, although rocks with <55 weight percent SiO2 are rare. Rock compositions form a high-potassium (K) calc-alkaline series with pronounced negative titanium-phosphorus-niobium-tantalum anomalies and high barium/niobium, barium/tantalum, and lanthanum/niobium typical of subduction-related continental margin arcs (Gill, 1981). Most rocks are porphyritic and commonly contain 15–35 volume percent phenocrysts of plagioclase, pyroxene, and hornblende±biotite. Although the oldest eruptive centers have the most mafic compositions, erupted rock compositions oscillated between mafic and intermediate to felsic compositions through time. Following a brief hiatus in volcanism, post subduction rocks of the ~3.9- to 0.1-Ma, bimodal, high-K Aurora volcanic field were erupted onto the Bodie Hills volcanic field. Volcanism in the Bodie Hills volcanic field persisted until 8 Ma without apparent changes in rock composition or style of eruption despite the transition from subduction of the Farallon plate beneath the west coast of North America to establishment of a transform plate margin at ~10 Ma (John and others, 2012).
The eastern and southeastern parts of the Bodie Hills volcanic field and Miocene sedimentary rocks on the southern edge of Fletcher Valley are unconformably overlain by Pliocene to late Pleistocene (~3.9 to 0.1 Ma) rocks of the Aurora volcanic field (Gilbert and others, 1968; Al-Rawi, 1969; Chesterman and Gray, 1975; Kleinhampl and others, 1975; Lange and others, 1993; Lange and Carmichael, 1996; Kingdon and others 2013). The field covers ~325 km2 and includes many well-preserved volcanic centers. These centers consist of monogenetic lava and cinder cones, valley-filling lava flows, shield volcanoes, and lava domes. Compositions of the Aurora volcanic field rocks are bimodally distributed and consist principally of trachyandesite and trachydacite to high-silica rhyolite.
Numerous hydrothermal systems were operative in the Bodie Hills during the Miocene (Vikre and others, in press). Structurally focused hydrothermal systems formed large epithermal gold-silver vein deposits in the Bodie and Aurora mining districts that are temporally and spatially related to intermediate- to silicic-composition dome complexes (John and others, 2012).
Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
By Robert J. Fleck, Edward A. du Bray, David A. John, Peter G. Vikre, Michael A. Cosca, Lawrence W. Snee, and Stephen E. Box
2 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
Map location number
Sample number Latitude Longitude Unit; alteration zone; or mining districtAppendix number
1 098-12B 38.38762 −119.18139 Trachyandesite of Masonic 12 098-12A 38.35923 −119.19917 Eureka Valley Tuff 13 MAS10-72 38.40189 −119.13718 Trachyandesite of Masonic Gulch 14 RW08-1 38.41123 −119.12414 Alteration: Red Wash-East Walker River alteration zone 15 MAS10-73 38.39643 −119.13470 Trachyandesite of Masonic Gulch 16 098-12D 38.39951 −119.11939 Trachyandesite of Masonic 17 MAS10-55 38.41419 −119.10259 Alteration: Red Wash-East Walker River alteration zone 18 098-12E 38.39143 −119.12397 Trachyandesite of Masonic Gulch 19 MAS10-75 38.39169 −119.11549 Trachyandesite of Masonic Gulch 1
10 07-BA-38 38.36049 −119.14502 Andesite of Lakeview Spring 111 MAS07-1A 38.34992 −119.14832 Alteration: Masonic mining district, Chemung mine 112 MAS12-10 #1 38.33716 −119.16013 Alteration: Masonic mining district, Success mine 113 MAS12-10 #2 38.33716 −119.16013 Alteration: Masonic mining district, Success mine 114 MAS10-76 38.38169 −119.11534 Trachyandesite of Masonic, plug 115 MAS09-1A 38.35847 −119.13824 Alteration: Masonic mining district, Red Rock mine 116 12-BA-20 38.33410 −119.15949 Trachyandesite of Masonic 117 MAS09-1 38.35783 −119.13268 Alteration: Masonic mining district, Red Rock mine 118 098-12F 38.37542 −119.11418 Trachyandesite of Masonic 119 MAS07-3 38.35968 −119.12682 Alteration: Masonic mining district, Sarita mine 120 07-BA-40 38.36544 −119.11607 Alteration: Masonic mining district, Pittsburg-Liberty mine 121 088-22A 38.36731 −119.10727 Alteration: Masonic mining district, Maybelle mine 122 10-BA-15 38.34130 −119.11570 Trachyandesite of Masonic 123 10-BA-13 38.35154 −119.10419 Trachyandesite of Masonic 124 088-22B 38.37937 −119.07802 Trachyandesite of Masonic 125 MAS11-2B 38.36064 −119.08681 Alteration: Masonic mining district, Perini mine 126 MAS11-1 38.36041 −119.08369 Alteration: Masonic mining district, Perini mine 127 11-BA-40 38.41155 −119.01907 Trachydacite of Rough Creek 128 09-BA-7 38.33786 −119.08727 Trachyandesite of Masonic 129 12-BA-9 38.33679 −119.07378 Trachydacite of East Canyon 130 08SB038 38.40828 −118.97383 Trachyandesite of Del Monte 131 10-BA-29 38.36466 −119.01452 Trachydacite of Rough Creek 132 10-BA-9 38.35278 −119.02068 Trachyandesite of Masonic, plug 133 6-289-2/45/DD72 38.3729 −118.9993 Eureka Valley Tuff 234 10-BA-62 38.36327 −119.00635 Tephra in sedimentary rocks of Fletcher Valley 135 10-BA-6 38.33375 −119.02470 Trachydacite of Rough Creek 136 10-BA-5 38.33945 −118.99699 Pyroxene rhyolite 137 11-BA-41 38.35057 −118.98085 Trachyandesite of Del Monte 138 11-BA-32 38.33637 −118.97804 Rhyolite of Bodie Creek 139 08SB032 38.34561 −118.95580 Unwelded tuff, Fletcher Basin 140 5-152-9/50/72 38.3548 −118.9261 Hornblende trachydacite 241 5-152-9/56/72 38.3548 −118.9261 Hornblende trachydacite 242 12-BA-3 38.34974 −118.84729 Trachyandesite of Mud Spring Canyon 343 10-BA-69 38.30537 −119.13652 Trachyandesite of Masonic 144 098-13D 38.27655 −119.16062 Trachyandesite of Clark Canyon 145 09-BA-43 38.26358 −119.16825 Trachyandesite of Clark Canyon 146 203195 38.2823 −119.1479 Basaltic andesite of Locomotive Point 347 09-BA-47 38.28409 −119.13821 Rhyolite of Bodie Hills 148 09-BA-42 38.27001 −119.14887 Rhyolite of Big Alkali 1
Table 1. Map location numbers for 40Ar/39Ar geochronology samples from the Bodie Hills volcanic field, California and Nevada.
Introduction 3
Map location number
Sample number Latitude Longitude Unit; alteration zone; or mining districtAppendix number
49 088-21A 38.27363 −119.13962 Trachyandesite of Aurora Canyon 150 098-13B 38.26802 −119.13218 Rhyolite of Bodie Hills 151 MC-12-20 38.2701 −119.1261 Hornblende trachyandesite plug 352 088-23F 38.31068 −119.11700 Trachyandesite of Masonic 153 088-23D 38.28113 −119.10206 Trachyandesite of Aurora Canyon 154 088-23A 38.27852 −119.10021 Trachyandesite of Aurora Canyon 155 088-23B 38.27831 −119.09908 Trachyandesite of Aurora Canyon 156 08-BA-62 38.32006 −119.04943 Trachyandesite of Masonic 157 088-25A 38.27322 −119.09077 Trachyandesite of Aurora Canyon 158 09-BA-1 38.31968 −119.04411 Trachyandesite of Cow Camp Creek 359 077-8C 38.27145 −119.07783 Trachyandesite of Aurora Canyon 160 077-8B 38.28334 −119.05617 Trachydacite intrusion 161 088-21B 38.26418 −119.07504 Trachydacite of Potato Peak 162 09-BA-35 38.29048 −119.04642 Trachydacite intrusion 163 09-BA-49 38.26389 −119.04748 Eureka Valley Tuff 164 11-BA-60 38.32693 −118.97204 Rhyolite of Bodie Creek 165 08-BA-65 38.31071 −118.97808 Rhyolite of Bald Peak 166 10-BA-67 38.26200 −118.98300 Rhyolite of Bald Peak 167 AU-10/61/DD61 38.26 −118.981 Eureka Valley Tuff 268 108-11A 38.27826 −118.94807 Rhyolite of Bodie Creek 169 077-9B 38.26971 −118.95063 Rhyolite of Bodie Creek 170 077-9D 38.28562 −118.92803 Rhyolite of Del Monte Canyon 171 AU-6/60/DD61 38.285 −118.928 Rhyolite of Del Monte Canyon 272 077-9C 38.27661 −118.93036 Rhyolite of Del Monte Canyon 173 SAW11-9 38.29036 −118.91657 Alteration: Sawtooth Ridge alteration zone 174 077-9E 38.31905 −118.91003 Trachyandesite of Del Monte 175 10-BA-20 38.31679 −118.91129 Rhyolite of Aurora Creek 176 10-BA-21 38.30315 −118.89740 Rhyolite of Aurora Creek 177 108-10C 38.28052 −118.90623 Trachyandesite of West Brawley Peak 178 108-10A 38.27293 −118.91272 Trachyandesite of Aurora 179 FA1 38.2931 −118.8914 Alteration: Aurora mining district, adularia in Prospectus vein 280 10-BA-27 38.27500 −118.90498 Rhyolite of East Brawley Peak 181 AU-2/59/DD61 38.282 −118.896 Aurora mining district, adularia in Del Monte shaft dump 282 AU-1/58/DD61 38.266 −118.9 Alteration: Aurora mining district, adularia in Esmeralda vein dump 283 00-BA-16 38.2708 −118.8908 Trachyandesite of Aurora 284 MC-12-19 38.31952 −118.78154 Trachyandesite of Borealis 385 39509-10 38.21532 −119.22755 Dacite of Hot Springs Canyon 186 39509-3K 38.20793 −119.22751 Alteration: Cinnabar Canyon-US 395 alteration zone 187 088-24B 38.25504 −119.14115 Trachyandesite of Willow Springs 188 088-24A 38.25278 −119.13951 Rhyolite of Big Alkali 189 PP09-10A1 38.25309 −119.13844 Alteration: Aurora Canyon alteration zone 190 098-13A 38.25754 −119.12788 Rhyolite of Big Alkali 191 CC09-9D1 38.19869 −119.17050 Alteration: Cinnabar Canyon-US 395 alteration zone 192 CC09-9D2 38.19869 −119.17050 Alteration: Cinnabar Canyon-US 395 alteration zone 193 088-24C 38.24786 −119.11208 Trachydacite of Potato Peak 194 12-BA-1 38.18995 −119.16513 Trachydacite of Cinnabar Canyon 195 077-7C 38.19677 −119.15829 Rhyolite of Del Monte Canyon 196 08-BA-46 38.24430 −119.10385 Alteration: Potato Peak alteration zone, Alta Pina mine 1
Table 1.—Continued
4 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
Map location number
Sample number Latitude Longitude Unit; alteration zone; or mining districtAppendix number
97 08-BA-50 38.24816 −119.09663 Rhyolite of Bodie Hills 198 077-7B 38.19178 −119.15240 Trachyandesite of Willow Springs 199 098-13C 38.25072 −119.09223 Trachydacite of Potato Peak 1
100 098-10C 38.24919 −119.09203 Trachydacite of Potato Peak 1101 088-21D 38.24330 −119.09209 Trachydacite of Potato Peak 1102 098-10B 38.25135 −119.08382 Rhyolite of Bodie Hills 1103 088-21C 38.25134 −119.08382 Rhyolite of Bodie Hills 1104 088-24D 38.22678 −119.10376 Trachydacite of Potato Peak 1105 088-21E 38.23457 −119.08582 Trachydacite of Potato Peak 1106 088-24E 38.21809 −119.10188 Trachydacite of Potato Peak 1107 08-BA-61 38.20769 −119.10175 Trachydacite of Potato Peak 1108 088-24F 38.20176 −119.08978 Trachyandesite of Willow Springs 1109 108-12A 38.24252 −119.04825 Trachydacite of Potato Peak 1110 08-BA-68 38.19323 −119.06835 Trachydacite of Potato Peak 1111 108-12B 38.23830 −119.00784 Trachydacite of Potato Peak 1112 08-BA-66 38.18629 −119.05680 Dacite of Silver Hill, debris flow clast 1113 12-BA-17 38.21961 −119.00019 Alteration: Bodie mining district, vein adularia, west of Bodie Bluff 1114 077-7F 38.20252 −119.02630 Dacite of Silver Hill 1115 BOD11-3A 38.21961 −119.00354 Alteration: Bodie mining district, vein adularia, Upper Hobart Tunnel dump 1116 BOD11-3B 38.21961 −119.00354 Alteration: Bodie mining district, vein adularia, Bodie Bluff 1117 077-6C 38.21870 −119.00050 Alteration: Bodie mining district, vein adularia, Bodie Bluff 1118 AU-16/63/DD61 38.215 −119.004 Alteration: Bodie mining district, vein adularia, south of Bodie Bluff 2119 077-6A 38.21490 −119.00370 Alteration: Bodie mining district, vein adularia, south of Bodie Bluff 1120 11-BA-22 38.21257 −119.00402 Alteration: Bodie mining district, vein adularia, south of Bodie Bluff 1121 BOD11-4E 38.21257 −119.00402 Alteration: Bodie mining district, vein adularia, Standard Hill Mine 1122 11-BA-21 38.20370 −119.00919 Alteration: Bodie mining district, vein adularia, Red Cloud mine 1123 AU-17/64/DD61 38.215 −118.997 Alteration: Bodie mining district, vein adularia, south of Bodie Bluff 2124 BOD09-5 38.20424 −119.00755 Alteration: Bodie mining district, vein adularia, Oro mine dump 1125 11-BA-7G 38.20420 −119.00649 Alteration: Bodie mining district, vein adularia, Silver Hill 1126 BOD09-3 38.20138 −119.00575 Alteration: Bodie mining district, vein adularia, Red Cloud Mine 1127 09-BA-28I 38.20151 −119.00360 Alteration or mineralization: Bodie, Red Cloud mine 1128 AU-18/65/DD61 38.201 −119.004 Alteration or mineralization: Bodie, Red Cloud mine 2129 09-BA-26 38.20360 −119.00021 Dacite of Silver Hill 1130 077-7G 38.23439 −118.96671 Trachyandesite of West Brawley Peak 1131 077-6F 38.18809 −119.00854 Dacite of Silver Hill-Sugarloaf plug 1132 077-9A 38.22088 −118.97443 Eureka Valley Tuff 1133 108-12C 38.18925 −118.98343 Dacite of Silver Hill 1134 108-12E 38.20763 −118.96489 Dacite of Silver Hill 1135 FA66 38.2375 −118.9008 Alteration: East Brawley Peak alteration zone, vein alunite 2136 00-BA-26 38.2542 −118.8841 Trachyandesite of Aurora 2137 AUR10-3 38.23752 −118.89919 Alteration: East Brawley Peak alteration zone, vein alunite 1138 077-7A 38.17860 −119.19476 Trachyandesite of Willow Springs 1139 08-BA-51 38.17449 −119.15441 Trachyandesite of Willow Springs 1140 09-BA-22 38.14302 −119.17974 Trachyandesite of Mt. Biedeman 1141 09-BA-23 38.12851 −119.17491 Tuff of Jacks Spring 1142 098-11B 38.12451 −119.17126 Trachydacite of Bridgeport Canyon 1143 098-11A 38.12239 −119.16954 Tuff of Jacks Spring 1
Table 1.—Continued
Introduction 5
Map location number
Sample number Latitude Longitude Unit; alteration zone; or mining districtAppendix number
144 10-BA-46 38.17380 −119.11508 Trachyandesite of Mount Biedeman 1145 10-BA-66 38.17250 −119.10125 Trachydacite of Potato Peak 1146 09SB015A 38.12310 −119.14843 Trachyandesite of Mount Biedeman 1147 098-11E 38.11099 −119.15841 Trachyandesite of Mount Biedeman 1148 077-7D 38.16719 −119.09983 Rhyolite of Bodie Hills 1149 09SB020A 38.13230 −119.13277 Trachydacite of Bridgeport Canyon 1150 108-9A 38.16540 −119.09816 Trachyandesite of Mount Biedeman 1151 108-12F 38.16336 −119.09918 Trachyandesite of Mount Biedeman 1152 MC-12-18 38.15575 −119.07825 Trachyandesite of Mount Biedeman 3153 12-BA-22 38.10151 −119.12400 Trachyandesite of Mount Biedeman 1154 6-181-12/52/DD72 38.1193 −119.1039 Tuff of Jacks Spring 2155 6-181-12/53/DD72 38.1193 −119.1039 Tuff of Jacks Spring 2156 6-215-1/121/72 38.1344 −119.0825 Trachyandesite of Mount Biedeman 2157 119-20B 38.13452 −119.07613 Trachyandesite of Mount Biedeman, plug 1158 09-BA-20 38.15662 −119.04741 Rhyolite of Bodie Hills 1159 10-BA-61 38.14005 −119.01551 Trachyandesite of Mount Biedeman 1160 108-12D 38.17315 −118.97800 Dacite of Silver Hill 1
Map location letter
Sample number Latitude Longitude Unit
A 1071 38.175 −118.832 Pyroxene trachyandesite of Cedar HillB 469 38.179 −118.826 Pyroxene trachyandesite of Cedar HillC 468 38.178 −118.819 Hornblende trachydacite of Cedar HillD 466 38.179 −118.821 Pyroxene trachyandesite of Cedar HillE 465 38.181 −118.823 Pyroxene trachyandesite of Cedar HillF 1069 38.188 −118.850 Hornblende trachydacite of Cedar HillG 139 38.209 −118.880 Hornblende trachydacite of Cedar HillH 199 38.153 −119.008 Hornblende trachydacite of Cedar HillI 144 38.184 −118.894 Trachyandesite of Cedar HillJ 1092A 38.255 −118.810 Rhyolite of Spring PeakK 25 38.261 −118.973 Basaltic trachyandesite of Beauty PeakL 120 38.240 −118.829 Trachyandesite of Mount HicksM 15 38.194 −118.961 Dacite of Silver HillN 414 38.177 −119.193 Trachyandesite of Willow SpringsO 406 38.234 −119.085 Trachydacite of Potato PeakP 507 38.154 −119.089 Rhyolite of Bodie HillsQ 459 38.097 −119.064 Eureka Valley TuffR 31 38.247 −118.990 Eureka Valley TuffS 27 38.247 −118.990 Eureka Valley TuffT W24 38.102 −119.066 Eureka Valley TuffU W25 38.131 −119.181 Eureka Valley TuffV 547 38.255 −118.948 Trachyandesite of West Brawley PeakW USGS(M)-711-67 38.2894 −118.9092 Trachyandesite of Aurora
Table 2. Map location numbers for K-Ar geochronology samples from the Bodie Hills volcanic field, California and Nevada.
Table 1.—Continued
6 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
Map location letter
Sample number Latitude Longitude Unit
X USGS(M)-668-G10 38.2403 −118.8917 Trachyandesite of AuroraY USGS(M)-711-8 38.2681 −118.8917 Trachyandesite of AuroraZ USGS(M)-712-1 38.2522 −118.9175 Trachyandesite of West Brawley PeakAA USGS(M)-710-7 38.2822 −118.9281 Rhyolite of Del Monte CanyonBB USGS(M)-NTS10B 38.3021 −118.8967 Rhyolite of Aurora CreekCC USGS(M)-Baghdad 38.2786 −118.9467 Rhyolite of Bodie CreekDD USGS(M)-670G4 38.2811 −118.8842 Rhyolite of Martinez HillEE USGS(M)-610-1B 38.2778 −118.8586 Rhyodacite of Aurora PeakFF USGS(M)-672-2 38.3128 −118.8825 Trachyandesite of Aurora CraterGG USGS(M)-611-5 38.2578 −118.8558 Trachyandesite south of Aurora PeakHH BH31 38.194 −119.008 Dacite of Silver Hill, plugII 5 38.0978 −119.1475 Trachyandesite of Sinnamon CutJJ 6 38.1256 −119.1697 Basaltic trachyandesite of RancheriaKK 37 38.287 −118.887 Alteration or mineralization: Trachyandesite of AuroraLL CH8Z1 38.288 −118.882 Trachyandesite of AuroraMM USGS(M)-7346-1 38.215 −119.004 Alteration or mineralization: BodieNN USGS(M)-RCD1B 38.201 −119.005 Alteration or mineralization: BodieOO USGS(M)-B270 38.216 −119.004 Alteration or mineralization: BodiePP USGS(M)-BH15 38.201 −119.003 Dacite of Silver HillQQ USGS(M)-S1 38.188 −119.008 Dacite of Silver HillRR USGS(M)-B271 38.215 −119.003 Dacite of Silver HillSS USGS(M)-856-8 38.214 −119.004 Dacite of Silver HillTT USGS(M)-BH17 38.193 −119.012 Dacite of Silver HillUU USGS(M)-7346-3 38.216 −118.981 Hornblende trachydacite of Cedar HillVV USGS(M)-BH32 38.200 −118.995 Dacite of Silver HillWW USGS(M)-856-32 38.209 −118.997 Dacite of Silver HillXX USGS(M)-856-10 38.205 −119.028 Trachydacite of Potato PeakYY USGS(M)-BH26 38.194 −119.003 Dacite of Silver HillZZ USGS(M)-BH16 38.200 −118.999 Dacite of Silver HillAAA USGS(M)-854-1 38.182 −119.003 Dacite of Silver HillBBB USGS(M)-BH29 38.196 −118.958 Dacite of Silver HillCCC USGS(M)-BM2 38.221 −119.057 Trachydacite of Potato PeakDDD USGS(M)-BH9 38.157 −119.116 Trachyandesite of Mount BiedemanEEE USGS(M)-MTB1 38.146 −119.073 Trachyandesite of Mount BiedemanFFF USGS(M)-BH27 38.140 −119.056 Rhyolite of Bodie HillsGGG USGS(M)-BH19A 38.222 −119.172 Trachyandesite of Willow SpringsHHH USGS(M)-BH6 38.1655 −119.1512 Rhyolite of Big AlkaliIII USGS(M)-BH20 38.220 −119.149 Rhyolite of Big AlkaliJJJ 23 38.156 −118.860 Trachybasalt of Cedar HillKKK 158 38.368 −118.812 Trachyandesite of Mud SpringLLL 160 38.357 −118.896 Trachyandesite of Aurora CraterMMM KA2362 38.4408 −118.9725 Hornblende andesiteNNN KA2364 38.4408 −118.9725 Hornblende andesiteOOO KA2368 38.4408 −118.9725 Hornblende andesitePPP KA2379R 38.4133 −118.9417 Aldrich Station Formation, tuffQQQ 742-45 38.0869 −119.1431 Basaltic trachyandesite of RancheriaRRR EL-KA-2 38.3047 −118.7799 Andesite
Table 2.—Continued
Introduction 7
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Lake
Taho
e
Pyra
mid
Lake
Wal
ker
Lake
Mon
oLa
ke
Littl
eW
alke
rCa
lder
a
Long
Valle
yCa
lder
a
figur
e 2
SIERRA NEVADA
38°
40°
120°
118°
025
5075
KIL
OMET
ERS
025
50 M
ILES
Figu
re 1
. M
ap s
how
ing
loca
tion
of a
nd m
ajor
phy
siog
raph
ic fe
atur
es n
ear t
he B
odie
Hill
s vo
lcan
ic fi
eld
(BH)
. Min
a de
flect
ion
(ver
tical
red
line
patte
rn) a
nd o
utlin
e of
the
Wal
ker L
ane
(red
shad
ed a
rea)
mod
ified
from
Fau
lds
and
Henr
y (2
008)
, Bus
by (2
013)
, and
Car
lson
and
oth
ers
(201
3). A
lso
see
John
and
oth
ers,
201
5.
8 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
40Ar/39Ar Analytical MethodsNew 40Ar/39Ar age determinations provide temporal
constraints on volcanic and hydrothermal activity in the Bodie Hills (figs. 2 and 3). Volcanic rocks were dated using either separates of one or more phenocryst mineral (plagioclase, sanidine, biotite, hornblende) or whole-rock aggregates. Ages of hydrothermal alteration were determined using separates of alunite, K-feldspar, or adularia. Where practical, multiple minerals from individual samples were dated to provide abundant confirmation of the results, but also to evaluate and document argon systematics of the different mineral phases nucleated under various magmatic and hydrothermal conditions.
Samples collected for 40Ar/39Ar analysis were crushed and sieved to sizes appropriate for preparation of high-purity separates. Standard magnetic and heavy-liquid separation techniques were used to make mineral separations. Whole-rock samples were prepared by crushing and isolating ~1 mm3 rock fragments from fresh rock that was free of obvious alteration and xenocrysts. Analyzed samples were washed in deionized water. In many cases, final separates were prepared by hand picking individual crystals.
Samples whose ages were determined at the U.S. Geological Survey 40Ar/39Ar lab in Menlo Park, CA (Appendix 1) were irradiated in the U.S. Geological Survey TRIGA Reactor Facility in Denver, Colorado; irradiation times were between 10 and 16 hours, although biotite, plagioclase, and sanidine from the rhyolite of Bodie Hills (map location number 102) were also analyzed in both 2-hour and 24-hour irradiations. Plagioclase, biotite, hornblende, and alunite ages were obtained using incremental-heating analysis, that is, incremental extraction of argon at progressively higher temperatures until all gas is released. Incremental heating analyses utilized a low-blank, tantalum and molybdenum, resistance-heated furnace. During heating, all argon gas was released in 8–15 temperature-controlled increments or steps; a few hornblende and potassium feldspar experiments required as many as 18 steps. Ages from incremental-heating experiments were determined by evaluating 40Ar/39Ar age spectra and isochron diagrams. Data for many of the individual sample ages constitute 40Ar/39Ar plateaus, defined as the weighted mean age of contiguous gas fractions representing >50% of the 39Ar released for which no difference can be detected between the ages of any two fractions at the 95% level of confidence (Fleck and others, 1977). Where no plateau was defined, either the 40Ar/39Ar isochron age or the integrated age of all increments was defined as the age of the sample.
Most sanidine and biotite ages determined at the U.S. Geological Survey 40Ar/39Ar lab in Menlo Park, CA were obtained by laser-fusion analysis, whereby grains were fused with a CO2 laser in a single heating step (Appendix 1). One or several grains were used in each analysis, depending on grain size. In all cases, a minimum number of grains were used to permit recognition and elimination of most xenocrystic or
detrital contamination through identification of outliers. The reported age for laser-fusion analyses represents the weighted mean of the replicate analyses, with the inverse variance of propagated, within-run (internal) errors of each used as its weighting factor (Taylor, 1982). Sanidine from the Taylor Creek Rhyolite (TCR-2) was used for calculation of neutron flux in all irradiations up to IRR290 (Appendix 1). Subsequent irradiations (higher IRR numbers in Appendix 1) used Bodie Hills sanidine (098-10B), calibrated to TCR-2, as the flux monitor. Regardless of the monitor mineral used, all ages in Appendix 1 are reported relative to an age of 28.02 Ma for the Fish Canyon Tuff sanidine standard (Renne and others, 1998) with uncertainties estimated at the one-sigma level, unless stated. Decay and abundance constants are those recommended by Steiger and Jäger (1977). Ages were calculated assuming a 40Ar/36Ar ratio of trapped argon equal to the atmospheric value of 295.5.
The 40Ar/39Ar ages reported in Appendix 2, determined in the U.S. Geological Survey 40Ar/39Ar lab in Denver, Colorado by L.W. Snee, are based on analyses of biotite, hornblende, plagioclase, or sanidine phenocrysts; hydrothermal K-feldspar, adularia, or alunite; and one whole rock analysis (Appendix 2). Analyzed materials were packaged in aluminum foil and stacked in quartz glass vials with monitor minerals placed between every second sample and at the top and bottom of each vial. Samples were irradiated in the U.S. Geological Survey’s TRIGA reactor in Denver, Colorado, in irradiation packages DD61, DD72, and DD78. Irradiated samples were heated in temperature steps in a double-vacuum furnace, and the released gasses were cleaned according to procedures described by Snee (2002). Argon isotopic total abundances (40ArT,
39ArT, 38ArT,
37ArT, and 36ArT) were measured on a MAP 215 mass spectrometer on a Faraday collector in volts to five decimal places. Corrected abundances for 40ArR (radiogenic 40Ar), 40ArK (irradiation-produced K-derived 40Ar), 40ArI (initial 40Ar), 39ArK (irradiation-produced K-derived 39Ar), 38ArCl (irradiation-produced Cl-derived 38Ar), 37ArCa (irradiation produced Ca-derived 37Ar, and 36ArI (initial 36Ar) are in volts. All estimated uncertainties in measured voltages are reported in Appendix 2 at one sigma. Voltages may be converted to moles using 1.160×10−12 moles argon per volt signal. The “F” value (40ArR/39ArK) for each temperature step was directly calculated from 40ArR divided by 39ArK. K/Ca was calculated from the expression K/Ca=0.5(39ArK/37ArCa). All isotopic abundances in Appendix 2 have been corrected for mass discrimination. Mass discrimination was determined by calculating the 40Ar/36Ar ratio of aliquots of atmospheric argon pipetted from a fixed pipette on the extraction line; the ratio during these experiments was 298.9, which was corrected to 295.5 to account for mass discrimination. Final isotopic abundances were corrected for all interfering isotopes of argon including atmospheric argon. 37Ar and 39Ar, which are produced during irradiation, are radioactive and their
Acknowledgments 9
abundances were corrected for radioactive decay. Abundances of interfering isotopes from K and Ca were calculated from reactor production ratios determined by irradiating and analyzing pure CaF2 and K2SO4; the K2SO4 was degassed in a vacuum furnace prior to irradiation to release extraneous argon. Corrections for Cl-derived 36Ar were determined using the method of Roddick (1983). Production ratios for these experiments are documented by Snee (2002). Apparent ages of each fraction include the error in J value (0.1 percent), which was calculated from the reproducibility of splits of the argon from several standards. The standards for this experiment were hornblende MMhb-1, using an age of 523.1±2.6 Ma (Samson and Alexander, 1987; Renne and others, 1998), and sanidine FCT1, using an age of 27.84 Ma, as measured in the Denver Argon Laboratory against MMhb-1 (Snee, 2002). Apparent ages were calculated using decay constants of Steiger and Jäger (1977). All apparent age errors are cited at one sigma. Uncertainties associated with apparent ages of individual fractions were calculated using equations of Dalrymple and others (1981). Isochron diagrams were produced for all samples and may be derived by using 40ArI (initial 40Ar) and 36ArI (initial 36Ar). Plateaus were determined according to the method of Fleck and others (1977).
The 40Ar/39Ar ages reported in Appendix 3, determined in the U.S. Geological Survey 40Ar/39Ar lab in Denver, CO by M.A. Cosca, are based on analyses of amphibole (hornblende), plagioclase, and whole rock samples. Samples, together with standards, were irradiated for 20 MW (megawatt) hours in the central thimble position of the USGS TRIGA reactor. Laser fusion of >10 individual Fish Canyon Tuff sanidine crystals (28.201±0.09 Ma; Kuiper and others, 2008) at each closely monitored position within the irradiation package resulted in neutron flux ratios reproducible to ±0.25% (two sigma). Isotopic production ratios and interfering nucleogenic reactions were determined from irradiated CaF2 and KCl salts and zero age K-silicate glass, and for this study the following values were measured: (36Ar/37Ar)Ca=(2.77 ± 0.03)×10−4; (39Ar/37Ar)Ca=(6.54 ± 0.33)×10−4; and (38Ar/39Ar)K=(1.29 ± 0.03)×10−2. Cadmium shielding during irradiation prevented any measurable nucleogenic (40Ar/39Ar)K. The irradiated samples and standards were loaded into numbered positions of a stainless steel planchette, placed into a laser sample chamber with an externally pumped ZnSe window, and evacuated to ultrahigh vacuum conditions in a fully automated stainless steel extraction line designed and built at the USGS in Denver. The samples were incrementally heated using a 25W CO2 laser equipped with a beam homogenizing lens and the liberated gas was expanded and purified by exposure to a cryogenic trap maintained at −140 °C and two hot SAES GP50 getters. Following purification the gas was expanded online into a Thermo Scientific ARGUS VI mass spectrometer (except sample 203195, which was analyzed using a Mass Analyzer Products 215–50 mass spectrometer) in static mode and Ar isotopes were measured by peak jumping using an electron multiplier in analog mode. Data were acquired during 10 measurement cycles and time zero intercepts were determined
by best-fit linear and (or) polynomial regressions to the data. Ages were calculated assuming a 40Ar/36Ar ratio of trapped argon equal to the atmospheric value of 298.56 (Lee and others, 2006) and using decay constants of Steiger and Jäger (1977). Data were corrected for mass discrimination, blanks, radioactive decay, and interfering nucleogenic reactions.
K-Ar Analytical MethodsConventional K-Ar analyses were not carried out as part
of the this study, but previous workers produced considerable K-Ar age data that constitute an important source of stratigraphic information on the Bodie Hills volcanic field and on the timing of mineralization in the Bodie and Aurora mining districts. Many earlier K-Ar analyses were performed in K-Ar laboratories at USGS facilities in Menlo Park and Denver or at University of California laboratories in Berkeley. An appropriate reference for K-Ar techniques used in all three laboratories is found in Dalrymple and Lanphere (1969).
DataAll available geochronology data for Bodie Hills volcanic
field are summarized in table 3. These data are synthesized and interpreted in other publications, including John and others (2012, 2015), Vikre and others (2015) and du Bray and others (written commun., 2015). As described previously, ages reported in Appendixes 1–3 utilized several slightly different ages for the Fish Canyon Tuff sanidine standard as a consequence of these age determinations having been conducted in several different labs, over a period of almost fifteen years, during which the accepted age for the sanidine standard was refined. In order to render ages calculated using different values for the sanidine standard comparable, ages calculated using a sanidine standard age different from 28.02 Ma were recalculated using that value and are summarized in the column titled “Age recalculated for FCT= 28.02” (table 3).
AcknowledgmentsGeologic mapping and sample collection for this study
were conducted as part of the Mineral Systems of the Ancestral and Modern Cenozoic Cascades Arcs Project funded by the U.S. Geological Survey Mineral Resources Program. Technical assistance was provided in Menlo Park laboratories by Dean Miller, Donald Shamp, and James Saburomaru. In Denver, Ross Yeoman and John Lee offered similar assistance. Byron R. Berger (deceased) introduced L.W. Snee to the geology of the Bodie Hills and was instrumental in geochronology sample collection. Constructive reviews by R.D. Taylor and J.N. Aleinikoff are much appreciated and helped clarify data presentation.
10 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
Figu
re 2
. (A
) Loc
atio
ns o
f sam
ples
(sol
id b
lack
circ
les)
with
40Ar
/39Ar
age
det
erm
inat
ions
(tab
le 1
) sho
wn
on a
sim
plifi
ed g
eolo
gic
map
of t
he B
odie
Hill
s vo
lcan
ic fi
eld,
Ca
lifor
nia
and
Nev
ada.
Col
ored
pol
ygon
s po
rtray
ext
ent o
f eru
ptiv
e pr
oduc
ts a
ssoc
iate
d w
ith p
artic
ular
vol
cani
c ce
nter
s w
ithin
the
Bodi
e Hi
lls v
olca
nic
field
(mod
ified
fro
m J
ohn
and
othe
rs, 2
012;
201
5). U
ncol
ored
are
as a
re u
nder
lain
by
eith
er o
lder
bas
emen
t roc
ks, r
ocks
of t
he A
uror
a vo
lcan
ic fi
eld,
or s
urfic
ial d
epos
its. (
B) In
set m
ap
show
ing
loca
tions
of s
ampl
es (s
olid
circ
les)
with
40Ar
/39Ar
age
det
erm
inat
ions
(tab
le 1
) in
dens
ely
sam
pled
Bod
ie m
inin
g di
stric
t.
CALIFORNIA
NEVADA
Mt.
Bied
eman
Pota
toPe
akBo
die
Mou
ntai
n
Mas
onic
Mou
ntai
n
Braw
ley
Peak
s
Beau
tyPe
ak
Auro
raCr
ater
Bald
Pea
k
Mon
o La
ke
Mon
o V
alle
yFlet
cher
Valle
y
Brid
gepo
rt
Bridgeport Valley
Bod
ie
Aur
ora
Rough
Creek
East
Walker
Rive
r
395
Auro
ra
Cany
on Big
Alka
li
Bodie
Creek
167
182
Mas
onic
The
Elbo
w
395
WASSUK RANGE
SWEETWATERMOUNTAINS
Brid
gepo
rtRe
serv
oir
A11
8°45
'11
8°50
'11
8°55
'11
9°00
'11
9°05
'11
9°10
'11
9°15
'
38°2
5'
38°2
0'
38°1
5'
38°1
0'
38°0
5'
98
7
6
5
4
3
2
1
99
98
97
96
95
94
93
91,9
2
90
8988
87
8685
84
83
82
81
80
79
78
77
7675
74
73
7271
70
6968
6766
6564
6362
61
6059
58
57
56
555453
52 5150
49
48
4746
45
44
43
4240
,41
393837
3635
3433
3231
30
2928
27
2625
24
23
22
2120
1918
17
16
15
14
12,1
3
1110
160
159
158
157
156
154,
155
153
152
15115
0
149
147
146
145 14
814
4
14314
214
1
140
139
138
13713
6
135
134
13313
2
131
130
114
113
112
111
110
109
108
107
106
105
104
102,
103
10110
0
Inse
t m
ap
0
2.5
7.5
510
KIL
OMET
ERS
0
42
6 M
ILES
Rhyo
lite
of B
ig A
lkal
i
Trac
hyan
desi
te o
f Will
ow S
prin
gs
Trac
hyda
cite
of P
otat
o Pe
ak
Dac
ite o
f Silv
er H
ill
Trac
hyan
desi
te o
f Mou
nt B
iede
man
Rhyo
lite
of th
e B
odie
Hill
s
Rhyo
lite
of B
ald
Peak
Rhyo
lite
of B
odie
Cre
ek
Trac
hyan
desi
te o
f Aur
ora
Cany
on
Rhyo
lite
of R
ock
Spri
ngs
Cany
on
Trac
hyan
desi
te o
f Del
Mon
te
Trac
hyda
cite
of B
ridg
epor
t Can
yon
Rhyo
lite
of D
el M
onte
Can
yon
Rhyo
lite
of A
uror
a Cr
eek
Trac
hyan
desi
te o
f Wes
t Bra
wle
y Pe
ak
Bas
altic
trac
hyan
desi
te o
f Ran
cher
ia
Trac
hyda
cite
of R
ough
Cre
ek
Trac
hyan
desi
te o
f Aur
ora
Trac
hyan
desi
te o
f Eas
t Can
yon
Trac
hyan
desi
te o
f Mud
Spr
ing
Cany
on
Trac
hyan
desi
te o
f Mas
onic
EXPL
AN
ATIO
N
40A
r/39
Ar s
ampl
e lo
calit
y
!
!!
122 125 129
120,121
119
117
115,116
127
124
126
B
128
123118
Ç
Tailings Pond
Ç
#
#
!
!
!
!
!!
!
!
!
!
!
!
119°00'119°01'
38°13'
38°12'
0 1 KILOMETER
Main road
40Ar/39Ar sample locality
Mine
Bodie Bluff
RED CLOUD MINE
Bodie
Silver Hill
EXPLANATION
Figure 2.—Continued
Figure II 11
12 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
Figu
re 3
. (A
) Loc
atio
ns o
f sam
ples
(sol
id b
lack
circ
les)
with
K-A
r age
det
erm
inat
ions
(tab
le 2
) sho
wn
on a
sim
plifi
ed g
eolo
gic
map
of t
he B
odie
Hill
s vo
lcan
ic fi
eld,
Ca
lifor
nia
and
Nev
ada.
Col
ored
pol
ygon
s po
rtray
ext
ent o
f eru
ptiv
e pr
oduc
ts a
ssoc
iate
d w
ith p
artic
ular
vol
cani
c ce
nter
s w
ithin
the
Bodi
e Hi
lls v
olca
nic
field
(mod
ified
from
Jo
hn a
nd o
ther
s, 2
012;
201
5). (
B) In
set m
ap s
how
ing
loca
tions
of s
ampl
es (s
olid
circ
les)
with
K-A
r age
det
erm
inat
ions
(tab
le 2
) in
dens
ely
sam
pled
Bod
ie m
inin
g di
stric
t.
Inse
t m
apM
118°
45'
118°
50'
118°
55'
119°
00'
119°
05'
119°
10'
119°
15'
38°2
5'
38°2
0'
38°1
5'
38°1
0'
38°0
5'
CALIFORNIA
NEVADAM
t. Bi
edem
an
Pota
toPe
akBo
die
Mou
ntai
n
Mas
onic
Mou
ntai
n
Braw
ley
Peak
s
Beau
tyPe
ak
Auro
raCr
ater
Bald
Pea
k
Mon
o La
ke
Bod
ie
Rough
Creek
East
Walker
Rive
r
395
Auro
ra
Cany
on Big
Alka
li
Bodie
Creek
167
182
Mas
onic
The
Elbo
w
395
Aur
ora
WASSUK RANGE
Flet
cher
Valle
y
Brid
gepo
rtRe
serv
oir
SWEETWATERMOUNTAINS
A
Mon
o V
alle
y
Bridgeport Valley
II QQ
Q
JJU
MM
M,N
NN
,OO
O
PPP
LLL
KKK
RR
RFF
EEKK
LL DD
Y
BBW
AAC
C
K
N
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H
GG
GIII
DD
DPO
CC
C
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OMET
ERS
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ILES
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gepo
rt
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lite
of B
ig A
lkal
i
Trac
hyan
desi
te o
f Will
ow S
prin
gs
Trac
hyda
cite
of P
otat
o Pe
ak
Dac
ite o
f Silv
er H
ill
Trac
hyan
desi
te o
f Mou
nt B
iede
man
Rhyo
lite
of th
e B
odie
Hill
s
Rhyo
lite
of B
ald
Peak
Rhyo
lite
of B
odie
Cre
ek
Trac
hyan
desi
te o
f Aur
ora
Cany
on
Rhyo
lite
of R
ock
Spri
ngs
Cany
on
Trac
hyan
desi
te o
f Del
Mon
te
Trac
hyda
cite
of B
ridg
epor
t Can
yon
Rhyo
lite
of D
el M
onte
Can
yon
Rhyo
lite
of A
uror
a Cr
eek
Trac
hyan
desi
te o
f Wes
t Bra
wle
y Pe
ak
Bas
altic
trac
hyan
desi
te o
f Ran
cher
ia
Trac
hyda
cite
of R
ough
Cre
ek
Trac
hyan
desi
te o
f Aur
ora
Trac
hyan
desi
te o
f Eas
t Can
yon
Trac
hyan
desi
te o
f Mud
Spr
ing
Cany
on
Trac
hyan
desi
te o
f Mas
onic
EXPL
AN
ATIO
N
40A
r/39
Ar s
ampl
e lo
calit
y
#
#
Ç
RED CLOUD MINE
Tailings Pond
119°01'
38°13'
38°12'
119°
1 KILOMETER0
B
HH
TT
YY
VVZZ
PPNN
WW
RR
OO
MM
SS
Bodie Bluff
Bodie
Silver Hill
!
Main road
K-Ar sample locality
Mine
EXPLANATION
Ç
Figure 3.—Continued
Figure III 13
14 Geochronology of Cenozoic Rocks in the Bodie Hills, California and NevadaTa
ble
3.
Sum
mar
y co
mpi
latio
n of
geo
chro
nolo
gic
data
for s
ampl
es o
f the
Bod
ie H
ills
volc
anic
fiel
d, C
alifo
rnia
and
Nev
ada.
Sam
ple
num
ber
Lab_
no.
Latit
ude
Long
itude
Uni
tA
ge, M
aEr
ror,
Ma
Met
hod
Sour
ce1
Min
eral
Dec
ay
cons
tant
2
Reca
lcul
ated
ag
e,
usin
g ne
w
deca
y co
nsta
nts
Age
re
calc
ulat
ed
for F
CT=2
8.02
M
a
Sum
mar
y ag
e
158
—38
.368
−118
.812
Trac
hyan
desit
e of M
ud S
prin
g0.
110.
08K
-Ar
8G
roun
dmas
sne
w—
—0.
11
EL-K
A-6
—38
.363
5−1
18.8
169
Trac
hyan
desit
e of M
ud S
prin
g0.
040.
04A
r-Ar3
13G
roun
dmas
s—
—0.
040.
04U
SGS(
M)-6
72-2
—38
.312
8−1
18.8
825
Trac
hyan
desit
e of A
uror
a Cr
ater
0.25
0.05
K-A
r2
Who
le ro
ckol
d*0.
26—
0.26
160
—38
.357
−118
.896
Trac
hyan
desit
e of A
uror
a Cr
ater
0.47
0.19
K-A
r8
Gro
undm
ass
new
——
0.47
EL-K
A-9
—38
.363
0−1
18.8
461
Trac
hyan
desit
e 21.
320.
08A
r-Ar3
13G
roun
dmas
s—
—1.
331.
33EL
-KA
-2—
38.3
047
−118
.779
9A
ndes
ite1.
440.
06K
-Ar
13W
hole
rock
new
——
1.44
EL-K
A-7
—38
.330
6−1
18.7
901
And
esite
1.6
0.02
Ar-A
r313
Gro
undm
ass
——
1.6
1.6
120
KA
-208
938
.240
−118
.829
Trac
hyan
desit
e of M
ount
H
icks
1.6
0.1
K-A
r1
Who
le ro
ckol
d*1.
6—
1.6
09-B
A-1
—38
.319
68−1
19.0
4411
Trac
hyan
desit
e of C
ow C
amp
Cree
k2.
000.
04A
r-Ar4
14W
hole
rock
——
1.99
1.99
USG
S(M
)-611
-5—
38.2
578
−118
.855
8Tr
achy
ande
site s
outh
of
Aur
ora P
eak
2.2
0.1
K-A
r2
Who
le ro
ckol
d*2.
3—
2.3
USG
S(M
)-611
-5—
38.2
578
−118
.855
8Tr
achy
ande
site s
outh
of
Aur
ora P
eak
2.5
0.2
K-A
r2
Hor
nble
nde
old*
2.6
—2.
6
USG
S(M
)-670
G4
—38
.281
1−1
18.8
842
Rhyo
lite o
f Mar
tinez
Hill
2.5
0.1
K-A
r2
Biot
iteol
d*2.
6—
2.6
23—
38.1
56−1
18.8
60Tr
achy
basa
lt of
Ced
ar H
ill2.
600.
06K
-Ar
8G
roun
dmas
sne
w—
—2.
60U
SGS(
M)-6
10-1
B—
38.2
778
−118
.858
6Tr
achy
daci
te o
f Aur
ora P
eak
2.5
0.2
K-A
r2
Biot
iteol
d*2.
6—
2.6
USG
S(M
)-610
-1B
—38
.277
8−1
18.8
586
Trac
hyda
cite
of A
uror
a Pea
k2.
70.
2K
-Ar
2H
ornb
lend
eol
d*2.
8—
2.8
1071
KA
-199
938
.175
−118
.832
Pyro
xene
trac
hyan
desit
e of
Ceda
r Hill
6 1.0
0.1
K-A
r1
Plag
iocl
ase
old*
6 1.0
—6 1
.0
469
KA
-200
338
.179
−118
.826
Pyro
xene
trac
hyan
desit
e of
Ceda
r Hill
2.7
0.8
K-A
r1
Plag
iocl
ase
old*
2.8
—2.
8
466
KA
-191
238
.179
−118
.821
Pyro
xene
trac
hyan
desit
e of
Ceda
r Hill
2.7
0.2
K-A
r1
Biot
iteol
d*2.
8—
2.8
465
KA
-185
738
.181
−118
.823
Pyro
xene
trac
hyan
desit
e of
Ceda
r Hill
6 6.2
2.5
K-A
r1
Plag
iocl
ase
old*
6 6.4
—6 6
.4
25K
A-2
086
38.2
61−1
18.9
73Ba
salti
c tra
chya
ndes
ite o
f Be
auty
Pea
k2.
80.
1K
-Ar
1W
hole
rock
old*
2.9
—2.
9
468
KA
-185
938
.178
−118
.819
Hor
nble
nde t
rach
ydac
ite o
f Ce
dar H
ill2.
80.
4K
-Ar
1Pl
agio
clas
eol
d*2.
9—
2.9
1069
KA
-200
238
.188
−118
.850
Hor
nble
nde t
rach
ydac
ite o
f Ce
dar H
ill2.
50.
3K
-Ar
1Pl
agio
clas
eol
d*2.
6—
2.6
1069
KA
-200
438
.188
−118
.850
Hor
nble
nde t
rach
ydac
ite o
f Ce
dar H
ill2.
50.
1K
-Ar
1Bi
otite
old*
2.6
—2.
6
[Ent
ries i
n th
e “S
umm
ary
age”
col
umn
repr
esen
t a re
capi
tula
tion
of K
-Ar a
ges,
reca
lcul
ated
usi
ng th
e de
cay
cons
tant
s of S
teig
er a
nd a
nd Jä
ger (
1977
), an
d 40
Ar/39
Ar a
ges,
calc
ulat
ed a
ssum
ing
a Fi
sh C
anyo
n Tu
ff ag
e of
28.
02 M
a]
Sam
ple
num
ber
Lab_
no.
Latit
ude
Long
itude
Uni
tA
ge, M
aEr
ror,
Ma
Met
hod
Sour
ce1
Min
eral
Dec
ay
cons
tant
2
Reca
lcul
ated
ag
e,
usin
g ne
w
deca
y co
nsta
nts
Age
re
calc
ulat
ed
for F
CT=2
8.02
M
a
Sum
mar
y ag
e
139
KA
-198
438
.209
−118
.880
Hor
nble
nde t
rach
ydac
ite o
f Ce
dar H
ill3.
40.
3K
-Ar
1Bi
otite
old*
3.5
—3.
5
139
KA
-198
4R38
.209
−118
.880
Hor
nble
nde t
rach
ydac
ite o
f Ce
dar H
ill3.
10.
3K
-Ar
1Bi
otite
old*
3.2
—3.
2
139
KA
-199
338
.209
−118
.880
Hor
nble
nde t
rach
ydac
ite o
f Ce
dar H
ill2.
31.
6K
-Ar
1Pl
agio
clas
eol
d*2.
4—
2.4
199
KA
-198
038
.153
−119
.008
Hor
nble
nde t
rach
ydac
ite o
f Ce
dar H
ill3.
20.
7K
-Ar
1Pl
agio
clas
eol
d*3.
3—
3.3
USG
S(M
)-734
6-3
—38
.216
−118
.981
Hor
nble
nde t
rach
ydac
ite o
f Ce
dar H
ill2.
70.
1K
-Ar
6W
hole
rock
old*
2.8
—2.
8
5-15
2-9/
50/7
2—
38.3
548
−118
.926
1H
ornb
lend
e tra
chyd
acite
3.04
0.03
Ar-A
r39
Who
le ro
ck—
—3.
063.
065-
152-
9/56
/72
—38
.354
8−1
18.9
261
Hor
nble
nde t
rach
ydac
ite3.
530.
18A
r-Ar3
9Pl
agio
clas
e—
—3.
553.
5514
4K
A-2
076
38.1
84−1
18.8
94Tr
achy
ande
site o
f Ced
ar H
ill3.
60.
4K
-Ar
1Pl
agio
clas
eol
d*3.
7—
3.7
1092
AK
A-2
066
38.2
55−1
18.8
10Rh
yolit
e of S
prin
g Pe
ak3.
60.
1K
-Ar
1Sa
nidi
neol
d*3.
7—
3.7
2031
95—
38.2
823
−119
.147
9Ba
salti
c and
esite
of
Loco
mot
ive P
oint
3.9
0.06
Ar-A
r414
Gro
undm
ass
——
3.87
3.87
USG
S(M
)-BH
6—
38.1
655
−119
.151
2Rh
yolit
e of B
ig A
lkal
i5.
70.
2K
-Ar
6Bi
otite
old*
5.9
—5.
9U
SGS(
M)-B
H20
—38
.220
−119
.149
Rhyo
lite o
f Big
Alk
ali
5.2
0.3
K-A
r6
Biot
iteol
d*5.
3—
5.3
USG
S(M
)-BH
20—
38.2
20−1
19.1
49Rh
yolit
e of B
ig A
lkal
i5.
40.
6K
-Ar
6H
ornb
lend
eol
d*5.
5—
5.5
077-
7C—
38.1
9677
−119
.158
29Rh
yolit
e of B
ig A
lkal
i5.
478
0.02
4A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
5.47
808
8-24
A—
38.2
5278
−119
.139
51Rh
yolit
e of B
ig A
lkal
i6.
201
0.02
6A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
6.20
109
8-13
A—
38.2
5754
−119
.127
88Rh
yolit
e of B
ig A
lkal
i6.
173
0.02
8A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
6.17
309
-BA
-42
—38
.270
01−1
19.1
4887
Rhyo
lite o
f Big
Alk
ali
5.45
50.
025
Ar-A
r7
Biot
iteFC
T=28
.02
——
5.45
539
509-
10—
38.2
153
−119
.227
55D
acite
of H
ot S
prin
gs C
anyo
n8.
070
0.01
7A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
8.07
041
4K
A-1
973
38.1
77−1
19.1
93Tr
achy
ande
site o
f Will
ow
Sprin
gs7.
80.
2K
-Ar
1Pl
agio
clas
eol
d*8.
0—
8.0
USG
S(M
)-BH
19A
—38
.222
−119
.172
Trac
hyan
desit
e of W
illow
Sp
rings
8.0
0.2
K-A
r6
Biot
iteol
d*8.
2—
8.2
077-
7A—
38.1
7860
−119
.194
76Tr
achy
ande
site o
f Will
ow
Sprin
gs8.
004
0.03
7A
r-Ar
7Bi
otite
FCT=
28.0
2—
—8.
004
077-
7A—
38.1
7860
−119
.194
76Tr
achy
ande
site o
f Will
ow
Sprin
gs8.
051
0.01
9A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
8.05
1
077-
7B—
38.1
9178
−119
.152
40Tr
achy
ande
site o
f Will
ow
Sprin
gs8.
122
0.02
9A
r-Ar
7Bi
otite
FCT=
28.0
2—
—8.
122
077-
7B—
38.1
9178
−119
.152
40Tr
achy
ande
site o
f Will
ow
Sprin
gs8.
070
0.02
1A
r-Ar
7H
ornb
lend
eFC
T=28
.02
——
8.07
0
077-
7B—
38.1
9178
−119
.152
40Tr
achy
ande
site o
f Will
ow
Sprin
gs8.
139
0.02
4A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
8.13
9
088-
24B
—38
.255
04−1
19.1
4115
Trac
hyan
desit
e of W
illow
Sp
rings
8.57
50.
022
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
575
Tabl
e 3.
—Co
ntin
ued
Table III 15
16 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
Sam
ple
num
ber
Lab_
no.
Latit
ude
Long
itude
Uni
tA
ge, M
aEr
ror,
Ma
Met
hod
Sour
ce1
Min
eral
Dec
ay
cons
tant
2
Reca
lcul
ated
ag
e,
usin
g ne
w
deca
y co
nsta
nts
Age
re
calc
ulat
ed
for F
CT=2
8.02
M
a
Sum
mar
y ag
e
088-
24F
—38
.201
76−1
19.0
8978
Trac
hyan
desit
e of W
illow
Sp
rings
8.15
50.
019
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
155
08-B
A-5
1—
38.1
7449
−119
.154
41Tr
achy
ande
site o
f Will
ow
Sprin
gs8.
305
0.01
7A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
8.30
5
12-B
A-1
—38
.189
95−1
19.1
6512
Trac
hyda
cite
of C
inna
bar
Cany
on8.
548
0.02
8A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
8.54
8
406
KA
-199
038
.234
−119
.085
Trac
hyda
cite
of P
otat
o Pe
ak8.
40.
2K
-Ar
1Pl
agio
clas
eol
d*8.
6—
8.6
USG
S(M
)-856
-10
—38
.205
−119
.028
Trac
hyda
cite
of P
otat
o Pe
ak8.
90.
2K
-Ar
6Bi
otite
old*
9.1
—9.
1U
SGS(
M)-8
56-1
0—
38.2
05−1
19.0
28Tr
achy
daci
te o
f Pot
ato
Peak
9.0
0.2
K-A
r6
Hor
nble
nde
old*
9.2
—9.
2U
SGS(
M)-B
M2
—38
.221
−119
.057
Trac
hyda
cite
of P
otat
o Pe
ak9.
10.
1K
-Ar
6Bi
otite
old*
9.3
—9.
308
8-21
B Ru
n 2
—38
.264
18−1
19.0
7504
Trac
hyda
cite
of P
otat
o Pe
ak8.
927
0.01
0A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
8.92
708
8-21
D—
38.2
4330
−119
.092
09Tr
achy
daci
te o
f Pot
ato
Peak
8.96
40.
027
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
964
088-
21E
—38
.234
57−1
19.0
8582
Trac
hyda
cite
of P
otat
o Pe
ak8.
863
0.05
0A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
8.86
308
8-24
C—
38.2
4786
−119
.112
08Tr
achy
daci
te o
f Pot
ato
Peak
8.99
60.
025
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
996
088-
24D
—38
.226
78−1
19.1
0376
Trac
hyda
cite
of P
otat
o Pe
ak9.
056
0.04
5A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
9.05
608
8-24
E—
38.2
1809
−119
.101
88Tr
achy
daci
te o
f Pot
ato
Peak
8.92
60.
025
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
926
08-B
A-6
8—
38.1
9323
−119
.068
35Tr
achy
daci
te o
f Pot
ato
Peak
8.99
0.02
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
9909
8-10
C—
38.2
4919
−119
.092
03Tr
achy
daci
te o
f Pot
ato
Peak
8.98
20.
023
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
982
098-
13C
—38
.250
72−1
19.0
9223
Trac
hyda
cite
of P
otat
o Pe
ak8.
998
0.02
1A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
8.99
810
8-12
A—
38.2
4252
−119
.048
25Tr
achy
daci
te o
f Pot
ato
Peak
8.96
30.
016
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
963
108-
12B
—38
.238
30−1
19.0
0784
Trac
hyda
cite
of P
otat
o Pe
ak9.
032
0.02
2A
r-Ar
7Bi
otite
FCT=
28.0
2—
—9.
032
10-B
A-6
6—
38.1
7250
−119
.101
25Tr
achy
daci
te o
f Pot
ato
Peak
8.74
90.
019
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
749
10-B
A-6
6—
38.1
7250
−119
.101
25Tr
achy
daci
te o
f Pot
ato
Peak
8.73
50.
015
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—8.
735
15K
A-1
972
38.1
94−1
18.9
61D
acite
of S
ilver
Hill
8.9
0.2
K-A
r1
Plag
iocl
ase
old*
9.1
—9.
1U
SGS(
M)-B
H15
—38
.201
−119
.003
Dac
ite o
f Silv
er H
ill8.
60.
4K
-Ar
6H
ornb
lend
eol
d*8.
8—
8.8
USG
S(M
)-BH
15—
38.2
01−1
19.0
03D
acite
of S
ilver
Hill
8.7
0.2
K-A
r6
Biot
iteol
d*8.
9—
8.9
USG
S(M
)-S1
—38
.188
−119
.008
Dac
ite o
f Silv
er H
ill8.
50.
4K
-Ar
6W
hole
rock
old*
8.7
—8.
7U
SGS(
M)-S
1—
38.1
88−1
19.0
08D
acite
of S
ilver
Hill
8.3
0.4
K-A
r6
Plag
iocl
ase
old*
8.5
—8.
5U
SGS(
M)-S
1—
38.1
88−1
19.0
08D
acite
of S
ilver
Hill
8.9
0.4
K-A
r6
Plag
iocl
ase
old*
9.1
—9.
1U
SGS(
M)-B
271
—38
.215
−119
.003
Dac
ite o
f Silv
er H
ill8.
40.
2K
-Ar
6H
ornb
lend
eol
d*8.
6—
8.6
USG
S(M
)-B27
1—
38.2
15−1
19.0
03D
acite
of S
ilver
Hill
8.5
0.3
K-A
r6
Plag
iocl
ase
old*
8.7
—8.
7U
SGS(
M)-8
56-8
—38
.214
−119
.004
Dac
ite o
f Silv
er H
ill8.
20.
2K
-Ar
6W
hole
rock
old*
8.4
—8.
4U
SGS(
M)-8
56-8
—38
.214
−119
.004
Dac
ite o
f Silv
er H
ill9.
20.
5K
-Ar
6H
ornb
lend
eol
d*9.
4—
9.4
USG
S(M
)-BH
17—
38.1
93−1
19.0
12D
acite
of S
ilver
Hill
9.2
0.5
K-A
r6
Hor
nble
nde
old*
9.4
—9.
4U
SGS(
M)-B
H32
—38
.200
−118
.995
Dac
ite o
f Silv
er H
ill8.
80.
2K
-Ar
6Bi
otite
old*
9.0
—9.
0U
SGS(
M)-8
56-3
2—
38.2
09−1
18.9
97D
acite
of S
ilver
Hill
8.9
0.3
K-A
r6
Biot
iteol
d*9.
1—
9.1
USG
S(M
)-BH
26—
38.1
94−1
19.0
03D
acite
of S
ilver
Hill
9.1
0.5
K-A
r6
Hor
nble
nde
old*
9.3
—9.
3U
SGS(
M)-B
H16
—38
.200
−118
.999
Dac
ite o
f Silv
er H
ill9.
40.
2K
-Ar
6Bi
otite
old*
9.7
—9.
7U
SGS(
M)-8
54-1
—38
.182
−119
.003
Dac
ite o
f Silv
er H
ill8.
70.
2K
-Ar
6Bi
otite
old*
8.9
—8.
9
Tabl
e 3.
—Co
ntin
ued
Sam
ple
num
ber
Lab_
no.
Latit
ude
Long
itude
Uni
tA
ge, M
aEr
ror,
Ma
Met
hod
Sour
ce1
Min
eral
Dec
ay
cons
tant
2
Reca
lcul
ated
ag
e,
usin
g ne
w
deca
y co
nsta
nts
Age
re
calc
ulat
ed
for F
CT=2
8.02
M
a
Sum
mar
y ag
e
USG
S(M
)-BH
29—
38.1
96−1
18.9
58D
acite
of S
ilver
Hill
8.7
0.2
K-A
r6
Biot
iteol
d*8.
9—
8.9
077-
7F—
38.2
0252
−119
.026
30D
acite
of S
ilver
Hill
8.92
80.
024
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
928
09-B
A-2
6—
38.2
0360
−119
.000
21D
acite
of S
ilver
Hill
9.13
20.
020
Ar-A
r7
Biot
iteFC
T=28
.02
——
9.13
210
8-12
C—
38.1
8925
−118
.983
43D
acite
of S
ilver
Hill
9.08
90.
014
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—9.
089
108-
12D
—38
.173
15−1
18.9
7800
Dac
ite o
f Silv
er H
ill9.
018
0.01
4A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
9.01
810
8-12
E—
38.2
0763
−118
.964
89D
acite
of S
ilver
Hill
9.14
00.
020
Ar-A
r7
Plag
iocl
ase o
r Bi
otite
FCT=
28.0
2—
—9.
140
08-B
A-6
6—
38.1
8629
−119
.056
80D
acite
of S
ilver
Hill
deb
ris
flow
clas
t9.
064
0.02
4A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
9.06
4
BH31
—38
.194
−119
.008
Dac
ite o
f Silv
er H
ill, p
lug
8.6
0.4
K-A
r3
Seric
ite-c
hlor
iteol
d*8.
8—
8.8
077-
6F—
38.1
8809
−119
.008
54D
acite
of S
ilver
Hill
-Su
garlo
af p
lug
9.08
60.
028
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—9.
086
459
KA
-190
738
.097
−119
.064
Eure
ka V
alle
y Tu
ff9.
80.
2K
-Ar
1Bi
otite
old*
10.1
—10
.131
KA
-190
938
.247
−118
.990
Eure
ka V
alle
y Tu
ff9.
50.
3K
-Ar
1Bi
otite
old*
9.8
—9.
827
KA
-190
838
.247
−118
.990
Eure
ka V
alle
y Tu
ff9.
60.
3K
-Ar
1Bi
otite
old*
9.9
—9.
9W
24—
38.1
02−1
19.0
66Eu
reka
Val
ley
Tuff
9.19
0.28
K-A
r1
Biot
iteol
d*9.
4—
9.4
W25
—38
.131
−119
.181
Eure
ka V
alle
y Tu
ff9.
350.
37K
-Ar
1Bi
otite
old*
9.6
—9.
6W
25—
38.1
31−1
19.1
81Eu
reka
Val
ley
Tuff
9.01
0.27
K-A
r1
Biot
iteol
d*9.
2—
9.2
077-
9A—
38.2
2088
−118
.974
43Eu
reka
Val
ley
Tuff
9.40
10.
023
Ar-A
r7
Biot
iteFC
T=28
.02
——
9.40
107
7-9A
—38
.220
88−1
18.9
7443
Eure
ka V
alle
y Tu
ff9.
383
0.02
6A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
9.38
309
8-12
A—
38.3
5923
−119
.199
17Eu
reka
Val
ley
Tuff
9.45
0.04
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—9.
4509
-BA
-49
—38
.263
89−1
19.0
4748
Eure
ka V
alle
y Tu
ff9.
267
0.01
9A
r-Ar
7Bi
otite
FCT=
28.0
2—
—9.
267
AU
-10/
61/D
D61
—38
.260
−118
.981
Eure
ka V
alle
y Tu
ff9.
200.
04A
r-Ar3
9Bi
otite
——
9.26
9.26
6-28
9-2
—38
.372
9−1
18.9
993
Eure
ka V
alle
y Tu
ff9.
300.
29A
r-Ar3
9Bi
otite
——
9.36
9.36
USG
S(M
)-BH
9—
38.1
57−1
19.1
16Tr
achy
ande
site o
f Mou
nt
Bied
eman
9.3
0.3
K-A
r6
Who
le ro
ckol
d*9.
5—
9.5
USG
S(M
)-MTB
1—
38.1
46−1
19.0
73Tr
achy
ande
site o
f Mou
nt
Bied
eman
9.5
0.2
K-A
r6
Hor
nble
nde
old*
9.8
—9.
8
098-
11E
—38
.110
99−1
19.1
5841
Trac
hyan
desit
e of M
ount
Bi
edem
an9.
019
0.02
8A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
9.01
9
09-B
A-2
2—
38.1
4302
−119
.179
74Tr
achy
ande
site o
f Mou
nt
Bied
eman
9.02
20.
024
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—9.
022
09SB
015A
—38
.123
10−1
19.1
4843
Trac
hyan
desit
e of M
ount
Bi
edem
an8.
890
0.06
4A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
8.89
0
108-
12F
—38
.163
36−1
19.0
9918
Trac
hyan
desit
e of M
ount
Bi
edem
an9.
987
0.01
5A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
9.98
7
108-
9A—
38.1
6540
−119
.098
16Tr
achy
ande
site o
f Mou
nt
Bied
eman
9.94
70.
019
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—9.
947
10-B
A-4
6—
38.1
7380
−119
.115
08Tr
achy
ande
site o
f Mou
nt
Bied
eman
8.77
90.
013
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
779
Tabl
e 3.
—Co
ntin
ued
Table III 17
18 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
Sam
ple
num
ber
Lab_
no.
Latit
ude
Long
itude
Uni
tA
ge, M
aEr
ror,
Ma
Met
hod
Sour
ce1
Min
eral
Dec
ay
cons
tant
2
Reca
lcul
ated
ag
e,
usin
g ne
w
deca
y co
nsta
nts
Age
re
calc
ulat
ed
for F
CT=2
8.02
M
a
Sum
mar
y ag
e
10-B
A-6
1—
38.1
4005
−119
.015
51Tr
achy
ande
site o
f Mou
nt
Bied
eman
10.0
180.
164
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—10
.018
12-B
A-2
2—
38.1
0155
−119
.123
95Tr
achy
ande
site o
f Mou
nt
Bied
eman
8.93
30.
042
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—8.
933
6-21
5-1/
121/
72—
38.1
344
−119
.082
5Tr
achy
ande
site o
f Mou
nt
Bied
eman
9.18
0.08
Ar-A
r39
Hor
nble
nde
——
9.24
9.24
MC-
12-1
8—
38.1
5575
−119
.078
25Tr
achy
ande
site o
f Mou
nt
Bied
eman
9.24
0.09
Ar-A
r414
Hor
nble
nde
——
9.18
9.18
119-
20B
—38
.134
52−1
19.0
7613
Trac
hyan
desit
e of M
ount
Bi
edem
an, p
lug
9.07
30.
033
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—9.
073
08-B
A-6
5—
38.3
1071
−118
.978
08Rh
yolit
e of B
ald
Peak
9.68
20.
013
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—9.
682
10-B
A-6
7—
38.2
6203
−118
.983
03Rh
yolit
e of B
ald
Peak
9.65
20.
016
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—9.
652
507
KA
-199
838
.154
−119
.089
Rhyo
lite o
f Bod
ie H
ills
9.5
0.3
K-A
r1
Plag
iocl
ase
old*
9.8
—9.
850
7K
A-2
049
38.1
54−1
19.0
89Rh
yolit
e of B
odie
Hill
s9.
30.
3K
-Ar
1Bi
otite
old*
9.5
—9.
5U
SGS(
M)-B
H27
—38
.140
−119
.056
Rhyo
lite o
f Bod
ie H
ills
9.1
0.2
K-A
r6
Biot
iteol
d*9.
3—
9.3
077-
7D—
38.1
6719
−119
.099
83Rh
yolit
e of B
odie
Hill
s9.
858
0.02
7A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
9.85
807
7-7D
—38
.167
19−1
19.0
9983
Rhyo
lite o
f Bod
ie H
ills
9.86
00.
013
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—9.
860
088-
21C
—38
.251
34−1
19.0
8382
Rhyo
lite o
f Bod
ie H
ills
9.77
60.
017
Ar-A
r7
Biot
iteFC
T=28
.02
——
9.77
608
8-21
C—
38.2
5134
−119
.083
82Rh
yolit
e of B
odie
Hill
s9.
893
0.02
5A
r-Ar
7Bi
otite
FCT=
28.0
2—
—9.
893
088-
21C
—38
.251
34−1
19.0
8382
Rhyo
lite o
f Bod
ie H
ills
9.80
00.
020
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—9.
800
088-
21C
—38
.251
34−1
19.0
8382
Rhyo
lite o
f Bod
ie H
ills
9.80
60.
018
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—9.
806
088-
21C
—38
.251
34−1
19.0
8382
Rhyo
lite o
f Bod
ie H
ills
9.74
00.
023
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—9.
740
088-
21C
—38
.251
34−1
19.0
8382
Rhyo
lite o
f Bod
ie H
ills
9.76
60.
020
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—9.
766
088-
21C
—38
.251
34−1
19.0
8382
Rhyo
lite o
f Bod
ie H
ills
9.77
00.
009
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—9.
770
088-
21C
—38
.251
34−1
19.0
8382
Rhyo
lite o
f Bod
ie H
ills
9.77
40.
008
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—9.
774
08-B
A-5
0—
38.2
4816
−119
.096
63Rh
yolit
e of B
odie
Hill
s9.
757
0.01
3A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
9.75
709
8-10
B —
38.2
5135
−119
.083
82Rh
yolit
e of B
odie
Hill
s9.
819
0.01
3A
r-Ar
7Bi
otite
FCT=
28.0
2—
—9.
819
098-
10B
—38
.251
35−1
19.0
8382
Rhyo
lite o
f Bod
ie H
ills
9.78
60.
022
Ar-A
r7
Biot
iteFC
T=28
.02
——
9.78
609
8-10
B (B
Hb)
—38
.251
35−1
19.0
8382
Rhyo
lite o
f Bod
ie H
ills
9.81
90.
017
Ar-A
r7
Biot
iteFC
T=28
.02
——
9.81
909
8-10
B —
38.2
5135
−119
.083
82Rh
yolit
e of B
odie
Hill
s9.
778
0.03
1A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
9.77
809
8-10
B—
38.2
5135
−119
.083
82Rh
yolit
e of B
odie
Hill
s9.
748
0.02
1A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
9.74
809
8-10
B—
38.2
5135
−119
.083
82Rh
yolit
e of B
odie
Hill
s9.
779
0.00
5A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
9.77
909
8-10
B—
38.2
5135
−119
.083
82Rh
yolit
e of B
odie
Hill
s9.
756
0.00
2A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
9.75
609
8-13
B—
38.2
6802
−119
.132
18Rh
yolit
e of B
odie
Hill
s9.
813
0.02
7A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
9.81
309
-BA
-20
—38
.156
62−1
19.0
4741
Rhyo
lite o
f Bod
ie H
ills
9.60
90.
013
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—9.
609
09-B
A-4
7—
38.2
8409
−119
.138
21Rh
yolit
e of B
odie
Hill
s9.
877
0.01
2A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
9.87
7U
SGS(
M)-B
aghd
ad—
38.2
786
−118
.946
7Rh
yolit
e of B
odie
Cre
ek9.
90.
3K
-Ar
2Sa
nidi
neol
d*10
.2—
10.2
USG
S(M
)-Bag
hdad
—38
.278
6−1
18.9
467
Rhyo
lite o
f Bod
ie C
reek
10.2
0.4
K-A
r2
Plag
iocl
ase
old*
10.5
—10
.507
7-9B
—38
.269
71−1
18.9
5063
Rhyo
lite o
f Bod
ie C
reek
10.1
630.
029
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—10
.163
Tabl
e 3.
—Co
ntin
ued
Sam
ple
num
ber
Lab_
no.
Latit
ude
Long
itude
Uni
tA
ge, M
aEr
ror,
Ma
Met
hod
Sour
ce1
Min
eral
Dec
ay
cons
tant
2
Reca
lcul
ated
ag
e,
usin
g ne
w
deca
y co
nsta
nts
Age
re
calc
ulat
ed
for F
CT=2
8.02
M
a
Sum
mar
y ag
e
108-
11A
—38
.278
26−1
18.9
4807
Rhyo
lite o
f Bod
ie C
reek
9.89
00.
008
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—9.
890
11-B
A-3
2—
38.3
364
−118
.978
04Rh
yolit
e of B
odie
Cre
ek10
.127
0.01
3A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
10.1
2711
-BA
-60
—38
.326
93−1
18.9
7204
Rhyo
lite o
f Bod
ie C
reek
11.3
350.
138
Ar-A
r7
Feld
spar
FCT=
28.0
2—
—11
.335
077-
8C—
38.2
7145
−119
.077
83Tr
achy
ande
site o
f Aur
ora
Cany
on10
.460
0.02
0A
r-Ar
7Bi
otite
FCT=
28.0
2—
—10
.460
077-
8C#2
—38
.271
45−1
19.0
7783
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.4
810.
025
Ar-A
r7
Biot
iteFC
T=28
.02
——
10.4
81
077-
8C R
un 1
—38
.271
45−1
19.0
7783
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.4
270.
028
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—10
.427
077-
8C R
un 2
—38
.271
45−1
19.0
7783
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.4
260.
030
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—10
.426
077-
8C—
38.2
7145
−119
.077
83Tr
achy
ande
site o
f Aur
ora
Cany
on10
.444
0.01
4A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
10.4
44
077-
8C R
un 2
—38
.271
45−1
19.0
7783
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.4
640.
015
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—10
.464
077-
8C R
un 3
—38
.271
45−1
19.0
7783
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.4
580.
016
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—10
.458
088-
21A
—38
.273
63−1
19.1
3962
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.3
580.
025
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—10
.358
088-
23A
—38
.278
52−1
19.1
0021
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.5
830.
032
Ar-A
r7
Biot
iteFC
T=28
.02
——
10.5
83
088-
23A
—38
.278
52−1
19.1
0021
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.2
750.
109
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—10
.275
088-
23B
—38
.278
31−1
19.0
9908
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.5
340.
052
Ar-A
r7
Biot
iteFC
T=28
.02
——
10.5
34
088-
23B
—38
.278
31−1
19.0
9908
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.3
180.
023
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—10
.318
088-
23D
—38
.281
13−1
19.1
0206
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.4
630.
047
Ar-A
r7
Biot
iteFC
T=28
.02
——
10.4
63
088-
23D
—38
.281
13−1
19.1
0206
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.2
650.
052
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—10
.265
088-
25A
—38
.273
22−1
19.0
9077
Trac
hyan
desit
e of A
uror
a Ca
nyon
10.4
250.
026
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—10
.425
10-B
A-6
2—
38.3
6327
−119
.006
35Te
phra
in se
dim
enta
ry ro
cks
of F
letc
her V
alle
y10
.464
0.04
1A
r-Ar
7Bi
otite
FCT=
28.0
2—
—10
.464
10-B
A-6
2—
38.3
6327
−119
.006
35Fl
etch
er V
alle
y se
dim
ents
10.5
820.
023
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—10
.582
077-
9E—
38.3
1905
−118
.910
03Tr
achy
ande
site o
f Del
Mon
te10
.949
0.02
5A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
10.9
4908
SB03
8—
38.4
0828
−118
.973
83Tr
achy
ande
site o
f Del
Mon
te10
.982
0.05
0A
r-Ar
7Bi
otite
FCT=
28.0
2—
—10
.982
11-B
A-4
1—
38.3
5057
−118
.980
85Tr
achy
ande
site o
f Del
Mon
te10
.942
0.02
4A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
10.9
4209
8-11
B—
38.1
2451
−119
.171
26Tr
achy
daci
te o
f Brid
gepo
rt Ca
nyon
11.0
670.
022
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—11
.067
Tabl
e 3.
—Co
ntin
ued
Table III 19
20 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
Sam
ple
num
ber
Lab_
no.
Latit
ude
Long
itude
Uni
tA
ge, M
aEr
ror,
Ma
Met
hod
Sour
ce1
Min
eral
Dec
ay
cons
tant
2
Reca
lcul
ated
ag
e,
usin
g ne
w
deca
y co
nsta
nts
Age
re
calc
ulat
ed
for F
CT=2
8.02
M
a
Sum
mar
y ag
e
09SB
020A
—38
.132
30−1
19.1
3277
Trac
hyda
cite
of B
ridge
port
Cany
on11
.080
0.01
9A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
11.0
80
08SB
032
—38
.345
61−1
18.9
5580
Unw
elde
d tu
ff in
sedi
men
tary
ro
cks o
f Fle
tche
r Val
ley
10.9
180.
043
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—10
.918
10-B
A-5
—38
.339
45−1
18.9
9699
Pyro
xene
rhyo
lite
11.1
530.
011
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—11
.153
10-B
A-2
7—
38.2
7500
−118
.904
98Rh
yolit
e of E
ast B
raw
ley
Peak
11.1
790.
016
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—11
.179
USG
S(M
)-NTS
10B
—38
.302
1−1
18.8
967
Rhyo
lite o
f Aur
ora C
reek
10.9
0.2
K-A
r2
Biot
iteol
d*11
.2—
—U
SGS(
M)-N
TS10
B—
38.3
021
−118
.896
7Rh
yolit
e of A
uror
a Cre
ek11
.00.
2K
-Ar
2Sa
nidi
neol
d*11
.3—
—10
-BA
-20
—38
.316
79−1
18.9
1129
Rhyo
lite o
f Aur
ora C
reek
11.1
770.
013
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—11
.177
10-B
A-2
1—
38.3
0315
−118
.897
40Rh
yolit
e of A
uror
a Cre
ek11
.181
0.02
2A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
11.1
8107
7-9D
—38
.285
62−1
18.9
2803
Rhyo
lite o
f Del
Mon
te
Cany
on11
.200
0.03
2A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
11.2
00
077-
9D—
38.2
8562
−118
.928
03Rh
yolit
e of D
el M
onte
Ca
nyon
11.1
390.
020
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—11
.139
AU
-6/6
0/D
D61
—38
.285
−118
.928
Rhyo
lite o
f Del
Mon
te
Cany
on11
.21
0.03
Ar-A
r39
Biot
ite—
—11
.28
11.2
8
USG
S(M
)-710
-7—
38.2
822
−118
.928
1Rh
yolit
e of D
el M
onte
Ca
nyon
?11
.20.
2K
-Ar
2Bi
otite
old*
11.5
—11
.5
077-
9C—
38.2
7661
−118
.930
36Rh
yolit
e of D
el M
onte
Ca
nyon
11.2
580.
142
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—11
.258
077-
9C—
38.2
7661
−118
.930
36Rh
yolit
e of D
el M
onte
Ca
nyon
11.2
200.
017
Ar-A
r7
Sani
dine
FCT=
28.0
2—
—11
.220
077-
8B—
38.2
8334
−119
.056
17Tr
achy
daci
te in
trusio
n11
.153
0.02
8A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
11.1
5309
-BA
-35
—38
.290
48−1
19.0
4642
Trac
hyda
cite
intru
sion
11.2
690.
034
Ar-A
r7
Biot
iteFC
T=28
.02
——
11.2
6909
8-13
D—
38.2
7655
−119
.160
62Tr
achy
ande
site o
f Cla
rk
Cany
on11
.341
0.01
7A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
11.3
41
09-B
A-4
3—
38.2
6358
−119
.168
25Tr
achy
ande
site o
f Cla
rk
Cany
on11
.268
0.11
2A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
11.2
68
KA
2379
R—
38.4
133
−118
.941
7Tu
ff in
Ald
rich
Stat
ion
Form
a-tio
n11
.40
0.54
K-A
r11
Biot
iteol
d*11
.70
—11
.70
547
KA
-204
838
.255
−118
.948
Trac
hyan
desit
e of W
est B
raw
-le
y Pe
ak12
.50.
2K
-Ar
1Pl
agio
clas
eol
d*12
.8—
12.8
USG
S(M
)-712
-1—
38.2
522
−118
.917
5Tr
achy
ande
site o
f Wes
t Bra
w-
ley
Peak
11.2
0.2
K-A
r2
Biot
iteol
d*11
.5—
11.5
USG
S(M
)-712
-1—
38.2
522
−118
.917
5Tr
achy
ande
site o
f Wes
t Bra
w-
ley
Peak
10.9
0.3
K-A
r2
Plag
iocl
ase
old*
11.2
—11
.2
USG
S(M
)-712
-1—
38.2
522
−118
.917
5Tr
achy
ande
site o
f Wes
t Bra
w-
ley
Peak
11.6
0.3
K-A
r2
Hor
nble
nde
old*
11.9
—11
.9
077-
7G—
38.2
3439
−118
.966
71Tr
achy
ande
site o
f Wes
t Bra
w-
ley
Peak
11.3
230.
032
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—11
.323
Tabl
e 3.
—Co
ntin
ued
Sam
ple
num
ber
Lab_
no.
Latit
ude
Long
itude
Uni
tA
ge, M
aEr
ror,
Ma
Met
hod
Sour
ce1
Min
eral
Dec
ay
cons
tant
2
Reca
lcul
ated
ag
e,
usin
g ne
w
deca
y co
nsta
nts
Age
re
calc
ulat
ed
for F
CT=2
8.02
M
a
Sum
mar
y ag
e
108-
10C
—38
.280
52−1
18.9
0623
Trac
hyan
desit
e of W
est B
raw
-le
y Pe
ak11
.514
0.01
9A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
11.5
14
6—
38.1
256
−119
.169
7Ba
salti
c tra
chya
ndes
ite o
f Ra
nche
ria11
.30.
9K
-Ar
4W
hole
rock
old*
11.6
—11
.6
742-
45—
38.0
869
−119
.143
1Ba
salti
c tra
chya
ndes
ite o
f Ra
nche
ria11
.70.
5K
-Ar
12W
hole
rock
new
——
11.7
MC-
12-2
0—
38.2
7010
−119
.126
10H
ornb
lend
e tra
chya
ndes
ite
intru
sion
11.9
0.20
Ar-A
r414
Hor
nble
nde
——
11.8
211
.82
098-
11A
—38
.122
39−1
19.1
6954
Tuff
of Ja
cks S
prin
g12
.069
0.01
5A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
12.0
6909
-BA
-23
—38
.128
51−1
19.1
7491
Tuff
of Ja
cks S
prin
g12
.044
0.01
5A
r-Ar
7Sa
nidi
neFC
T=28
.02
——
12.0
446-
181-
12/5
2/D
D72
—38
.119
3−1
19.1
039
Tuff
of Ja
cks S
prin
g11
.87
0.16
Ar-A
r39
Sani
dine
——
11.9
511
.95
6-18
1-12
/53/
DD
72—
38.1
193
−119
.103
9Tu
ff of
Jack
s Spr
ing
11.9
00.
14A
r-Ar3
9Sa
nidi
ne—
—11
.98
11.9
8K
A23
62—
38.4
408
−118
.972
5H
ornb
lend
e and
esite
12.1
10.
39K
-Ar
11Pl
agio
clas
eol
d12
.43
—12
.43
KA
2364
—38
.440
8−1
18.9
725
Hor
nble
nde a
ndes
ite12
.07
0.50
K-A
r11
Hor
nble
nde
old
12.3
9—
12.3
9K
A23
68—
38.4
408
−118
.972
5H
ornb
lend
e and
esite
12.3
30.
31K
-Ar
11Bi
otite
old
12.6
6—
12.6
610
-BA
-29
—38
.364
66−1
19.0
1452
Trac
hyda
cite
of R
ough
Cre
ek11
.675
0.01
6A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
11.6
7510
-BA
-6—
38.3
3375
−119
.024
70Tr
achy
daci
te o
f Rou
gh C
reek
12.9
450.
020
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—12
.945
11-B
A-4
0—
38.4
1155
−119
.019
07Tr
achy
daci
te o
f Rou
gh C
reek
12.8
040.
023
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—12
.804
07-B
A-3
8—
38.3
6049
−119
.145
02A
ndes
ite o
f Lak
evie
w S
prin
g12
.930
0.03
3A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
12.9
30U
SGS(
M)-7
11-6
7—
38.2
894
−118
.909
2Tr
achy
ande
site o
f Aur
ora
13.5
0.3
K-A
r2
Hor
nble
nde
old*
13.9
—13
.9U
SGS(
M)-6
68-G
10—
38.2
403
−118
.891
7Tr
achy
ande
site o
f Aur
ora
14.4
0.3
K-A
r2
Hor
nble
nde
old*
14.8
—U
SGS(
M)-7
11-8
—38
.268
1−1
18.8
917
Trac
hyan
desit
e of A
uror
a15
.40.
3K
-Ar
2Pl
agio
clas
eol
d*15
.8—
15.8
CH8Z
1—
38.2
88−1
18.8
82Tr
achy
ande
site o
f Aur
ora
10.9
0.3
K-A
r5
Who
le ro
ckne
w—
—10
.910
8-10
A—
38.2
7293
−118
.912
72Tr
achy
ande
site o
f Aur
ora
12.5
800.
024
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—12
.580
00-B
A-1
6—
38.2
708
−118
.890
8Tr
achy
ande
site o
f Aur
ora
13.0
50.
44A
r-Ar3
9H
ornb
lend
e—
—13
.13
13.1
300
-BA
-26
—38
.254
2−1
18.8
841
Trac
hyan
desit
e of A
uror
a13
.05
0.08
Ar-A
r39
Hor
nble
nde
——
13.1
313
.13
098-
12E
—38
.391
43−1
19.1
2397
Trac
hyan
desit
e of M
ason
ic
Gul
ch13
.441
0.02
6A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
13.4
41
MA
S10-
72—
38.4
0189
−119
.137
18Tr
achy
ande
site o
f Mas
onic
G
ulch
13.4
850.
017
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—13
.485
MA
S10-
73—
38.3
9643
−119
.134
70Tr
achy
ande
site o
f Mas
onic
G
ulch
13.4
670.
016
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—13
.467
MA
S10-
75—
38.3
9169
−119
.115
49Tr
achy
ande
site o
f Mas
onic
G
ulch
<13.
497
0.02
4A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
<13.
497
12-B
A-9
—38
.336
81−1
19.0
7377
Trac
hyda
cite
of E
ast C
anyo
n13
.782
0.02
5A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
13.7
825
—38
.097
8−1
19.1
475
Trac
hyan
desit
e of S
inna
mon
Cu
t13
.30.
4K
-Ar
4H
ornb
lend
eol
d*13
.7—
13.7
12-B
A-3
—38
.349
74−1
18.8
4729
Trac
hyan
desit
e of M
ud S
prin
g Ca
nyon
13.9
60.
11A
r-Ar4
14Pl
agio
clas
e—
—13
.87
13.8
7
10-B
A-9
—38
.352
78−1
19.0
2068
Trac
hyan
desit
e of M
ason
ic,
plug
14.9
980.
019
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—14
.998
Tabl
e 3.
—Co
ntin
ued
Table III 21
22 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
Sam
ple
num
ber
Lab_
no.
Latit
ude
Long
itude
Uni
tA
ge, M
aEr
ror,
Ma
Met
hod
Sour
ce1
Min
eral
Dec
ay
cons
tant
2
Reca
lcul
ated
ag
e,
usin
g ne
w
deca
y co
nsta
nts
Age
re
calc
ulat
ed
for F
CT=2
8.02
M
a
Sum
mar
y ag
e
MA
S10-
76—
38.3
8169
−119
.115
34Tr
achy
ande
site o
f Mas
onic
, pl
ug14
.190
0.02
1A
r-Ar
7H
ornb
lend
eFC
T=28
.02
——
14.1
90
088-
22B
—38
.379
37−1
19.0
7802
Trac
hyan
desit
e of M
ason
ic14
.067
0.08
1A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
14.0
6708
8-23
F—
38.3
1068
−119
.117
00Tr
achy
ande
site o
f Mas
onic
14.1
930.
039
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—14
.193
08-B
A-6
2—
38.3
2006
−119
.049
43Tr
achy
ande
site o
f Mas
onic
14.1
310.
030
Ar-A
r7
Plag
iocl
ase
FCT=
28.0
2—
—14
.131
098-
12B
—38
.387
62−1
19.1
8139
Trac
hyan
desit
e of M
ason
ic14
.715
0.02
5A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
14.7
1509
8-12
D—
38.3
9951
−119
.119
39Tr
achy
ande
site o
f Mas
onic
<14.
800.
02A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
<14.
8009
8-12
F—
38.3
7542
−119
.114
18Tr
achy
ande
site o
f Mas
onic
14.0
940.
017
Ar-A
r7
Hor
nble
nde
FCT=
28.0
2—
—14
.094
09-B
A-7
—38
.337
86−1
19.0
8727
Trac
hyan
desit
e of M
ason
ic14
.674
0.02
5A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
14.6
7410
-BA
-13
—38
.351
54−1
19.1
0419
Trac
hyan
desit
e of M
ason
ic14
.410
0.01
6A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
14.4
1010
-BA
-15
—38
.341
30−1
19.1
1570
Trac
hyan
desit
e of M
ason
ic14
.141
0.01
7A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
14.1
4110
-BA
-69
—38
.305
37−1
19.1
3652
Trac
hyan
desit
e of M
ason
ic14
.107
0.01
4A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
14.1
0712
-BA
-20
—38
.334
10−1
19.1
5949
Trac
hyan
desit
e of M
ason
ic14
.136
0.02
0A
r-Ar
7Pl
agio
clas
eFC
T=28
.02
——
14.1
36M
C-12
-19
—38
.319
52−1
18.7
8154
Trac
hyan
desit
e of B
orea
lis16
.06
0.10
Ar-A
r414
Hor
nble
nde
——
15.9
615
.96
FA1
—38
.293
1−1
18.8
914
Alte
ratio
n: A
uror
a 10
.04
0.03
Ar-A
r310
Adu
laria
——
10.1
010
.10
FA66
—38
.237
5−1
18.9
008
Alte
ratio
n: E
ast B
raw
ley
Peak
al
tera
tion
zone
12
.34
0.04
Ar-A
r310
Alu
nite
——
12.4
212
.42
PP09
-10A
1—
38.2
5309
−119
.138
44A
ltera
tion:
Aur
ora C
anyo
n al
tera
tion
zone
10.8
650.
065
Ar-A
r7
Alu
nite
FCT=
28.0
2—
—10
.865
USG
S(M
)-734
6-1
—38
.215
−119
.004
Alte
ratio
n: B
odie
, Sta
ndar
d H
ill7.
20.
1K
-Ar
6A
dula
riaol
d*7.
4—
7.4
USG
S(M
)-734
6-1
—38
.215
−119
.004
Alte
ratio
n: B
odie
, Sta
ndar
d H
ill7.
00.
1K
-Ar
6A
dula
riaol
d*7.
2—
7.2
USG
S(M
)-RCD
1B—
38.2
01−1
19.0
05A
ltera
tion:
Bod
ie, R
ed C
loud
m
ine
7.7
0.1
K-A
r6
Adu
laria
old*
7.9
—7.
9
USG
S(M
)-B27
0—
38.2
16−1
19.0
04A
ltera
tion:
Bod
ie, S
tand
ard
Hill
8.0
0.2
K-A
r6
Adu
laria
old*
8.2
—8.
2
077-
6A—
38.2
149
−119
.003
7A
ltera
tion:
Bod
ie, s
outh
of
Bodi
e Blu
ff8.
286
0.02
4A
r-Ar
7A
dula
riaFC
T=28
.02
——
8.28
6
077-
6C—
38.2
187
−119
.000
5A
ltera
tion:
Bod
ie, B
odie
Blu
ff7.
179
0.41
7A
r-Ar
7A
dula
riaFC
T=28
.02
——
7.17
911
-BA
-7G
—38
.204
20−1
19.0
0649
Alte
ratio
n: B
odie
, Silv
er H
ill8.
217
0.01
2A
r-Ar
7A
dula
riaFC
T=28
.02
——
8.21
711
-BA
-21
—38
.203
70−1
19.0
0919
Alte
ratio
n: B
odie
, Red
Clo
ud
min
e8.
124
0.00
6A
r-Ar
7A
dula
riaFC
T=28
.02
——
8.12
4
BOD
09-5
—38
.204
30−1
19.0
0660
Alte
ratio
n: B
odie
, Oro
min
e du
mp
8.47
30.
007
Ar-A
r7
Adu
laria
FCT=
28.0
2—
—8.
473
BOD
09-3
—38
.201
46−1
19.0
048
Alte
ratio
n: B
odie
, Red
Clo
ud
min
e8.
628
0.01
4A
r-Ar
7A
dula
riaFC
T=28
.02
——
8.62
8
09-B
A-2
8I—
38.2
015
−119
.003
6A
ltera
tion:
Bod
ie, R
ed C
loud
m
ine
8.85
20.
013
Ar-A
r7
Adu
laria
FCT=
28.0
2—
—8.
852
11-B
A-2
2—
38.2
1257
−119
.004
02A
ltera
tion:
Bod
ie, s
outh
of
Bodi
e Blu
ff8.
498
0.00
5A
r-Ar
7A
dula
riaFC
T=28
.02
——
8.49
8
Tabl
e 3.
—Co
ntin
ued
Sam
ple
num
ber
Lab_
no.
Latit
ude
Long
itude
Uni
tA
ge, M
aEr
ror,
Ma
Met
hod
Sour
ce1
Min
eral
Dec
ay
cons
tant
2
Reca
lcul
ated
ag
e,
usin
g ne
w
deca
y co
nsta
nts
Age
re
calc
ulat
ed
for F
CT=2
8.02
M
a
Sum
mar
y ag
e
AU
-18/
65/D
D61
—38
.201
−119
.004
Alte
ratio
n: B
odie
, Red
Clo
ud
min
e8.
410.
02A
r-Ar3
9A
dula
ria—
—8.
468.
46
AU
-17/
64/D
D61
—38
.215
−118
.997
Alte
ratio
n: B
odie
, sou
th o
f Bo
die B
luff
8.23
0.04
Ar-A
r39
Adu
laria
——
8.28
8.28
AU
-16/
63/D
D61
—38
.215
−119
.004
Alte
ratio
n: B
odie
, sou
th o
f Bo
die B
luff
8.33
0.02
Ar-A
r39
Adu
laria
——
8.38
8.38
SAW
11-9
—39
.290
36−1
18.9
1657
Alte
ratio
n: S
awto
oth
alte
ra-
tion
zone
11
.105
0.01
1A
r-Ar
7A
luni
teFC
T=28
.02
——
11.1
05
3950
9-3K
—38
.207
93−1
19.2
2751
Alte
ratio
n: H
wy
395
alte
ratio
n zo
ne8.
169
0.01
3A
r-Ar
7A
luni
teFC
T=28
.02
——
8.16
9
08-B
A-4
6—
38.2
4430
−119
.103
85A
ltera
tion:
Pot
ato
Peak
alte
ra-
tion
zone
, Alta
Pin
a min
e10
.769
0.03
4A
r-Ar
7A
luni
teFC
T=28
.02
——
10.7
69
MA
S09-
1—
38.3
5783
−119
.132
68A
ltera
tion:
Mas
onic
, Red
Ro
ck m
ine
13.2
690.
144
Ar-A
r7
Alu
nite
FCT=
28.0
2—
—13
.269
MA
S09-
1A—
38.3
5847
−119
.138
24A
ltera
tion:
Mas
onic
, Red
Ro
ck m
ine
13.4
710.
038
Ar-A
r7
Alu
nite
FCT=
28.0
2—
—13
.471
MA
S07-
1A—
38.3
4992
−119
.148
32A
ltera
tion:
Mas
onic
, Ch
emun
g m
ine
13.3
860.
068
Ar-A
r7
Alu
nite
FCT=
28.0
2—
—13
.386
088-
22A
—38
.367
31−1
19.1
0727
Alte
ratio
n: M
ason
ic,
May
belle
min
e13
.018
0.06
1A
r-Ar
7A
luni
teFC
T=28
.02
——
13.0
18
07-B
A-4
0—
38.3
6544
−119
.116
07A
ltera
tion:
Mas
onic
, Pi
ttsbu
rg-L
iber
ty m
ine
13.0
270.
049
Ar-A
r7
Alu
nite
FCT=
28.0
2—
—13
.027
MA
S10-
55—
38.4
1419
−119
.102
59A
ltera
tion:
Mas
onic
, Red
was
h al
tera
tion
zone
13.2
70.
02A
r-Ar
7A
luni
teFC
T=28
.02
——
13.2
7
RW08
-1—
38.4
1123
−119
.124
14A
ltera
tion:
Mas
onic
, Red
was
h al
tera
tion
zone
13.3
380.
035
Ar-A
r7
Alu
nite
FCT=
28.0
2—
—13
.338
MA
S07-
3—
38.3
5968
−119
.126
82A
ltera
tion:
Mas
onic
, Sar
ita
min
e13
.253
0.05
1A
r-Ar
7A
luni
teFC
T=28
.02
——
13.2
53
CC09
-9D
1—
38.1
9869
−119
.170
50A
ltera
tion:
Cin
naba
r Can
yon
alte
ratio
n zo
ne8.
824
0.29
4A
r-Ar
7A
luni
teFC
T=28
.02
——
8.82
4
CC09
-9D
2—
38.1
9869
−119
.170
50A
ltera
tion:
Cin
naba
r Can
yon
alte
ratio
n zo
ne8.
682
0.02
0A
r-Ar
7A
luni
teFC
T=28
.02
——
8.68
2
MA
S11-
1A—
38.3
6041
−119
.083
69A
ltera
tion:
Mas
onic
, Per
ini
min
e12
.956
0.02
0A
r-Ar
7A
luni
teFC
T=28
.02
——
12.9
56
MA
S11-
2B—
38.3
6064
−119
.086
81A
ltera
tion:
Mas
onic
, Per
ini
min
e12
.960
0.01
4A
r-Ar
7A
luni
teFC
T=28
.02
——
12.9
60
AU
R10-
3—
38.2
3752
−118
.899
19A
ltera
tion:
Eas
t Bra
wle
y Pe
ak
alte
ratio
n zo
ne
11.9
540.
016
Ar-A
r7
Alu
nite
FCT=
28.0
2—
—11
.954
BOD
11-4
E—
38.2
1257
−119
.004
02A
ltera
tion:
Bod
ie, S
tand
ard
Hill
min
e8.
425
0.00
3A
r-Ar
7A
dula
riaFC
T=28
.02
——
8.42
5
Tabl
e 3.
—Co
ntin
ued
Table III 23
24 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
Sam
ple
num
ber
Lab_
no.
Latit
ude
Long
itude
Uni
tA
ge, M
aEr
ror,
Ma
Met
hod
Sour
ce1
Min
eral
Dec
ay
cons
tant
2
Reca
lcul
ated
ag
e,
usin
g ne
w
deca
y co
nsta
nts
Age
re
calc
ulat
ed
for F
CT=2
8.02
M
a
Sum
mar
y ag
e
MA
S12-
10 (#
1)—
38.3
3716
−119
.160
13A
ltera
tion:
Mas
onic
, Suc
cess
m
ine
13.3
980.
081
Ar-A
r7
Alu
nite
FCT=
28.0
2—
—13
.398
MA
S12-
10 (#
2)—
38.3
3716
−119
.160
13A
ltera
tion:
Mas
onic
, Suc
cess
m
ine
13.6
380.
077
Ar-A
r7
Alu
nite
FCT=
28.0
2—
—13
.638
37—
38.2
87−1
18.8
87A
ltere
d tra
chya
ndes
ite o
f A
uror
a10
.30.
2K
-Ar
4A
dula
riaol
d*10
.6—
10.6
AU
-1/5
8/D
D61
—38
.266
−118
.900
Alte
ratio
n: A
uror
a, Es
mer
alda
ve
in10
.63
0.05
Ar-A
r59
K-fe
ldsp
ar—
—10
.70
10.7
0
AU
-2/5
9/D
D61
—38
.282
−118
.896
Alte
ratio
n: A
uror
a, D
el M
onte
sh
aft
10.2
80.
05A
r-Ar5
9K
-feld
spar
——
10.3
510
.35
BOD
11-3
A—
38.2
1961
−119
.003
54A
ltera
tion:
Bod
ie, U
pper
H
obar
t Tun
nel
8.19
40.
005
Ar-A
r7
Adu
laria
FCT=
28.0
2—
—8.
194
BOD
11-3
B—
38.2
1961
−119
.003
54A
ltera
tion:
Bod
ie B
luff,
In
clin
e vei
n8.
542
0.02
5A
r-Ar
7A
dula
riaFC
T=28
.02
——
8.54
2
12-B
A-1
7—
38.2
1961
−119
.000
19A
ltera
tion:
Bod
ie B
luff,
wes
t sid
e8.
357
0.02
8A
r-Ar
7A
dula
riaFC
T=28
.02
——
8.35
7
1 Sou
rces
: 1, G
ilber
t and
oth
ers (
1968
); 2,
Silb
erm
an a
nd M
cKee
(197
2); 3
, Silb
erm
an a
nd o
ther
s (19
72);
4, K
lein
ham
pl a
nd o
ther
s (19
75);
5, M
orto
n an
d ot
hers
(197
7); 6
, Silb
erm
an a
nd C
hest
erm
an (1
972)
; 7,
R.J
Flec
k, th
is re
port;
8, L
ange
and
oth
ers (
1993
); 9,
L.W
. Sne
e, th
is re
port;
10,
Bre
it, (2
000)
; 11,
Gilb
ert a
nd R
eyno
lds (
1973
); 12
, Mar
vin
and
Dob
son
(197
9); 1
3, R
ehei
s and
oth
ers (
2002
); 14
, M.A
. Cos
ca, t
his
repo
rt.2 O
ld*:
All
ages
with
this
not
atio
n ad
just
ed in
“R
ecal
cula
ted
age”
col
umn
to a
ccou
nt fo
r new
dec
ay c
onst
ants
of S
teig
er a
nd Jä
ger (
1977
).3 A
ge in
itial
ly c
alcu
late
d fo
r Fis
h C
anyo
n tu
ff=27
.84
Ma.
4 Age
initi
ally
cal
cula
ted
for F
ish
Can
yon
Tuff=
28.2
01 M
a.5 A
ge in
itial
ly c
alcu
late
d fo
r Fis
h C
anyo
n tu
ff=27
.84
Ma;
isoc
hron
age
.6 L
ikel
y an
inac
cura
te a
ge.
Tabl
e 3.
—Co
ntin
ued
References Cited 25
References Cited
Al-Rawi, Y.T., 1969, Cenozoic history of the northern part of Mono Basin, California and Nevada: Berkeley, University of California, Ph.D. dissertation, 163 p.
Breit, F.J., Jr., 2000, Structural and temporal relationships and geochemical characteristics of the East Brawley Peak acid-sulfate prospect and the adjacent Aurora adularia-sericite system: Reno, University of Nevada, M.S. thesis, 215 p.
Busby, C.J., 2013, Birth of a plate boundary at ca. 12 Ma in the Ancestral Cascades arc, Walker Lane belt of California and Nevada: Geosphere, v. 9, p. 1147–1160.
Carlson, C.W., Pluhar, C.J., Glen, J.M.G., and Farner, M.J., 2013, Kinematics of the west-central Walker Lane—Spatially and temporally variable rotations evident in the late Miocene Stanislaus Group: Geosphere, v. 9, p. 1530–1551.
Chesterman, C.W., and Gray, C.H., Jr., 1975, Geology of the Bodie 15-minute quadrangle, Mono County, California: California Division of Mines and Geology, Map Sheet 21, scale 1:48,000.
Dalrymple, G.B., Alexander, B.C., Lanphere, M.A., and Kraker, G.P, 1981, Irradiation of samples for 40Ar/39Ar dating using the Geological Survey TRIGA reactor: U.S. Geological Survey Professional Paper 1176, 55 p.
Dalrymple, G.B., and Lanphere, M.A., 1969, Potassium-argon dating—principles, techniques and applications to geochronology: San Francisco, Freeman, 258 p.
du Bray, E.A., John, D.A., and Cousens, B.L., 2014, Petrologic, tectonic, and metallogenic evolution of the southern segment of the ancestral Cascades magmatic arc, California and Nevada: Geosphere, v. 10, p. 1–39.
Faulds, J.E., and Henry, C.D., 2008, Tectonic influences on the spatial and temporal evolution of the Walker Lane—An incipient transform fault along the evolving Pacific – North American plate boundary, in Spencer, J.E., and Titley, S.R., eds., Ores and orogenesis: Circum-Pacific tectonics, geologic evolution, and ore deposits: Arizona Geological Society Digest 22, p. 437–470.
Fleck, R.J., Hagstrum, J.T., Calvert, A.T., and Evarts, R.C., 2014, 40Ar/39Ar geochronology, paleomagnetism, and evolu-tion of the Boring volcanic field, Oregon and Washington, USA: Geosphere, v. 10, no. 6, p. 1283–1314, doi:10.1130/GES00985.1
Fleck, R.J., Sutter, J.H., and Elliot, D.H., 1977, Interpretation of discordant 40Ar/39Ar age-spectra of Mesozoic tholeiites from Antarctica: Geochimica et Cosmochimica Acta, v. 41, p. 15–32.
Gilbert, C.M., Christiansen, M.N., Al-Rawi, Yehya, and Lajoie, K.R., 1968, Structural and volcanic history of Mono Basin, California-Nevada, in Coats, R.R., Hay, R.L., and Anderson, C.A., eds., Studies in Volcanology: Geological Society of America Memoir 116, p. 275–329.
Gilbert, C.M., and Reynolds, M.W., 1973, Character and chronology of basin development, western margin of the Basin and Range Province: Geological Society of America Bulletin, v. 84, p. 2489–2510.
Gill, J., 1981, Orogenic andesites and plate tectonics: New York, Springer-Verlag, 390 p.
John, D.A., du Bray, E.A., Box, S.E., Vikre, P.G., Rytuba, J.J., Fleck, R.J., and Moring, B.C., 2015, Geologic map of the Bodie Hills, California and Nevada: U.S. Geological Survey Scientific Investigations Map 3318, 64 p., 2 sheets, scale 1:50,000, http://dx.doi.org/10.3133/sim3318.
John, D.A., du Bray, E.A., Fleck, R.J., Vikre, P.G., Box, S.E., and Moring, B.C., 2012, Miocene magmatism in the Bodie Hills volcanic field, California and Nevada—A long-lived eruptive center in the southern segment of the ancestral Cascades arc: Geosphere, v. 8, p. 44–97.
Kingdon, S., Cousens, B., John, D.A., and du Bray, E.A., 2013, Pliocene to late Pleistocene magmatism in the Aurora Volcanic Field, Nevada and California, USA [abs.]: Eos Transactions AGU V13G-2700.
Kleinhampl, F.J., Davis, W.E., Silberman, M.L., Chesterman, C.W., Chapman, R.H., and Gray, C.H., Jr., 1975, Aeromagnetic and limited gravity studies and generalized geology of the Bodie Hills region, Nevada and California: U.S. Geological Survey Bulletin 1384, 38 p.
Kuiper, K.F., Deino, A., Hilgen, F.J., Krijgsman, W., Renne, P.R., and Wijbrans, J.R., 2008, Synchronizing rock clocks of Earth history: Science, v. 320, p. 500–504.
Lange, R.A., and Carmichael, I.S.E., 1996, The Aurora volcanic field, California-Nevada—Oxygen fugacity constraints on the development of andesitic magma: Contributions to Mineralogy and Petrology, v. 125, p. 167–185.
Lange, R.A., Carmichael, I.S.E., and Renne, Paul, 1993, Potassic volcanism near Mono Basin, California—Evidence for high water and oxygen fugacities inherited from subduction: Geology, v. 21, p. 949–952.
Lee, J.-Y., Marti, K., Severinghaus, J.P., Kawamura, K., Yoo, H.-S., Lee, J.B., and Kim, J.S., 2006, A redetermination of the isotopic abundances of atmospheric Ar: Geochimica et Cosmochimica Acta, v. 70, p. 4507–4512.
Marvin, R.F., and Dobson, S.W., 1979, Radiometric ages; compilation B, U.S. Geological Survey: Isochron/West, no. 26, p. 3–30.
26 Geochronology of Cenozoic Rocks in the Bodie Hills, California and Nevada
McIntyre, G.A., Brooks, C., Compston, W., Turek, A., 1966, The statistical assessment of Rb-Sr isochrons: Journal of Geophysical Research, v. 71, p. 5459–5468.
Morton, J.L., Silberman, M.L., Bonham, H.F., Jr., Garside, L.J., and Noble, D.C., 1977, K-Ar ages of volcanic rocks, plutonic rocks, and ore deposits in Nevada and eastern California; determinations run under the USGS-NBMG Cooperative Program: Isochron/West, no. 20, p. 19–29.
Oldow, J.S., 1992, Late Cenozoic displacement partitioning in the northwestern Great Basin, in Craig, S.D., ed., Structure, tectonics, and mineralization of the Walker Lane; Walker Lane Symposium, proceedings volume: Reno, Nevada, Geological Society of Nevada, p. 17–52.
Oldow, J.S., 2003, Active transtensional boundary zone between the western Great Basin and Sierra Nevada block, western U.S. Cordillera: Geology, v. 31, p. 1033–1036.
Reheis, M.C, Stine, Scott, and Sarna-Wojcicki, A.M., 2002, Drainage reversals in Mono Basin during the late Pliocene and Pleistocene: Geological Society of America Bulletin, v. 114, p. 991–1006.
Renne, P.R., Swisher, C.C., Deino, A.L., Karner, D.B., Owens, T.L., and DePaolo, D.J., 1998, Intercalibration of standards, absolute ages and uncertainties in 40Ar/39Ar dating: Chemical Geology, v. 145, p. 117–152.
Roddick, J.C., 1983, High precision intercalibration of 40Ar/39Ar standards: Geochimica et Cosmochimica Acta, v. 47, p. 887–898.
Samson, S.D., and Alexander, E.G., 1987, Calibration of interlaboratory 40Ar/39Ar dating standard MMhb-1: Isotope Geoscience, v. 66, p. 27–34.
Silberman, M.L., and Chesterman, C.W., 1972, K-Ar age of volcanism and mineralization, Bodie mining district and Bodie Hills volcanic field, Mono County, California: Isochron/West, no. 3, p. 13–22.
Silberman, M.L., Chesterman, C.W., Kleinhampl, F.J., and Gray, C.H., Jr., 1972, K-Ar ages of volcanic rocks and gold-bearing quartz-adularia veins in the Bodie mining district, Mono County; California: Economic Geology, v. 67, p. 597–604.
Silberman, M.L., and McKee, E.H., 1972, A summary of radiometric age determinations on Tertiary volcanic rocks from Nevada and eastern California—part II, western Nevada: Isochron/West, no. 4, p. 7–28.
Snee, L.W., 2002, Argon thermochronology of mineral deposits—A review of analytical methods, formulations, and selected applications: U.S. Geological Survey Bulletin 2194, 39 p.
Steiger, R.H., and Jäger, E., 1977, Subcommission on geochronology—Convention on the use of decay constants in geo- and cosmochronology: Earth and Planetary Science Letters, v. 36, p. 359–362.
Stewart, J.H., 1988, Tectonics of the Walker Lane belt, western Great Basin—Mesozoic and Cenozoic deformation in a zone of shear, in Ernst, W.G., ed., Metamorphism and crustal evolution of the western United States: Englewood Cliffs, N. J., Prentice Hall, p. 681–713.
Taylor, J.R., 1982, An introduction to error analysis—The study of uncertainties in physical measurements: Mill Valley, California, University Science Books, 270 p.
Vikre, P.G., John, D.A., du Bray, E.A., and Fleck, R.J., in press, Gold-silver mining districts and alteration zones in the Miocene Bodie Hills volcanic field, California and Nevada: U.S. Geological Survey Scientific Investigations Report SIR–2015–5012, available at http://dx.doi.org/10.3133/sir20155012.
Menlo Park Publishing Service Centers, California Manuscript approved for publication January 23, 2015Edited by Sarah NagorsenDesign and Layout by Cory Hurd
Fleck and others—G
eochronology of Cenozoic Rocks in the Bodie H
ills, California and Nevada—
Data Series 916
ISSN 2327-638X (online)http://dx.doi.org/10.3133/ds916