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Geochimica et Cosmochimica Acta 75 (2011) 1621–1641

Rhenium–osmium isotope and platinum-group elements in theXinjie layered intrusion, SW China: Implications forsource mantle composition, mantle evolution, PGE

fractionation and mineralization

Hong Zhong a,⇑, Liang Qi a, Rui-Zhong Hu a, Mei-Fu Zhou b, Ti-Zhong Gou a,Wei-Guang Zhu a, Bing-Guang Liu c, Zhu-Yin Chu c

a State Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, 46 Guanshui Road,

Guiyang 550002, Chinab Department of Earth Sciences, University of Hong Kong, Hong Kong, China

c Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China

Received 5 February 2010; accepted in revised form 4 January 2011; available online 13 January 2011

Abstract

The Xinjie mafic–ultramafic layered intrusion in the Emeishan large igneous province (ELIP) hosts Cu–Ni–platinum groupelement (PGE) sulfide ore layers within the lower part and Fe–Ti–V oxide-bearing horizons within the middle part. The majormagmatic Cu–Ni–PGE sulfide ores and spatially associated cumulate rocks are examined for their PGE contents and Re–Osisotopic systematics. The samples yielded a Re–Os isochron with an age of 262 ± 27 Ma and an initial 187Os/188Os of0.12460 ± 0.00011 (cOs(t) = �0.5 ± 0.1). The age is in good agreement with the previously reported U–Pb zircon age, indicat-ing that the Re–Os system remained closed for most samples since the intrusion emplacement. They have near-chondriticcOs(t) values ranging from �0.7 to �0.2, similar to those of the Lijiang picrites and Song Da komatiites. Exceptionally,two samples from the roof zone and one from upper sequence exhibit radiogenic cOs(t) values (+0.6 to +8.6), showing minorcontamination by the overlying Emeishan basalts.

The PGE-rich ores contain relatively high PGE and small amounts of sulfides (generally less than 2%) and the abundanceof Cu and PGE correlate well with S, implying that the distribution of these elements is controlled by the segregation andaccumulation of a sulfide liquid. Some ore samples are poor in S (mostly

1622 H. Zhong et al. / Geochimica et Cosmochimica Acta 75 (2011) 1621–1641

magma in the ELIP were generated from a plume. This comprised recycled Neoproterozic oceanic lithosphere, includingdepleted peridotite mantle embedded with geochemically enriched domains. The ascending magmas thereafter interacted withminor (possibly

Fig. 1. Simplified geological map of the Xinjie layered intrusion (modified after Zhong et al., 2004). Inset a shows the distribution of thelayered intrusions in the Pan-Xi area (modified after Zhong et al., 2002). Insert b illustrates distribution of major terranes in China and thePan-Xi area (modified after Chung and Jahn, 1995). Abbreviations: NCB = North China block; YZB = Yangtze block; SG = Songpan-Ganze accretionary complex; QT = Qiangtang; LS = Lhasa; HI = Himalayan; TAR = Tarim; MON = Mongolia; QD = Qaidam;WB = West Burma; STM = Shan-Thai-Malay; IC = Indochina.

Re–Os isotope and PGE in Xinjie layered intrusion, SW China 1623

basaltic lava, sills, dikes and small intrusions, occur in thewestern margin of the Yangtze block (Li et al., 2003,2006; Zhou et al., 2006). The basement is overlain by athick sequence (>9 km) of Sinian (610–850 Ma) to Permianstrata composed of clastic, carbonate, and meta-volcanicrocks (SBGMR, 1991).

The ELIP comprises the Emeishan continental floodbasalts and spatially associated intrusions. The Emeishanbasalts are exposed over a rhombic area of�2.5 � 105 km2, with the volcanic succession ranging fromseveral hundred meters to 5 km in thickness. The volcanicrocks consist predominantly of tholeiites and andesitic bas-


alts, with minor flows and tuffs of trachyte and rhyolite inthe uppermost sequence (Chung and Jahn, 1995; Xuet al., 2001; Xiao et al., 2004; Zhang et al., 2006). The bas-alts are divided into high-Ti and low-Ti groups that areconsidered to have been derived from different mantlesources (Xu et al., 2001; Xiao et al., 2004). It is noteworthythat minor picrites associated with the high-Ti basalts havebeen identified in the Pan-Xi and Lijiang areas (Chung andJahn, 1995; Zhang et al., 2006), whereas some komatiiticrocks interbedded with low-Ti olivine basalts were docu-mented in the Song Da region of northern Vietnam (Hanskiet al., 2004). Magnetostratigraphic data and field observa-tions suggest that the bulk of the Emeishan volcanic se-quence formed within 1–2 million years (Huang andOpdyke, 1998; Ali et al., 2002). Recent SHRIMP and TIMSU–Pb dating of zircons from silicic ignimbrite, mafic/ultra-mafic intrusions and diabasic dikes indicate that the ELIPwas voluminously erupted at �260 Ma, consistent withthe end-Guadalupian (end Middle Permian) stratigraphicage (Zhou et al., 2002, 2005; Guo et al., 2004; Zhong andZhu, 2006; He et al., 2007).

The Pan-Xi area is located in the inner zone of the ELIP(Xu et al., 2004), which is considered the impact site of therising plume head (He et al., 2003). The area comprises N–Strending, fault-controlled, massive basalts, numerous spa-tially associated mafic–ultramafic intrusions, granites, andsyenites. The ore-bearing mafic–ultramafic intrusions de-scribed here are exposed along a 300 km-long and 10–30 km-wide belt, constituting the most important metallo-genic district for Fe–Ti–V and Ni–Cu–(PGE) metals in Chi-na. Giant Fe–Ti–V oxide deposits occur in several relativelylarge layered intrusions (13–60 km2), including the Panzhi-hua, Hongge, Baima and Taihe intrusions (Fig. 1; Yao andDu, 1993; Zhong et al., 2002, 2003, 2004, 2005; Zhou et al.,2005, 2008). Ni–Cu–(PGE) sulfide deposits are hosted inthe Limahe, Jinbaoshan and Zhubu intrusions (Wanget al., 2005; Tao et al., 2007, 2008; Zhou et al., 2008). Incontrast, both Fe–Ti–V oxide and Ni–Cu–PGE mineraliza-tion were discovered in the Xinjie layered intrusion (Zhonget al., 2004; Wang et al., 2008).

3. PETROGRAPHY OF THE XINJIE INTRUSION

The �260 Ma Xinjie intrusion (Zhou et al., 2002), is asill-like, 7.5 km long, 1–1.5 km wide, and 1200 m thickultramafic–mafic layered body, which intruded the latePermian Emeishan flood basalts (Fig. 1). Field investiga-tions reveal that the syenitic intrusions always cut the Xinjieintrusion and adjacent Emeishan basalts. The Xinjie ultra-mafic–mafic intrusion exhibits well-developed igneous lay-ering and has been divided into three cycles containing sixlithological zones (A–F, Fig. 2). Overall, the intrusion ismost ultramafic in its lower part and each cycle includesnumerous layers starting with the most ultramafic cyclicunits at the base followed by progressively evolved cyclicunits. Cycle I is about 400 m thick and comprises, fromthe bottom to top, peridotite, plagioclase peridotite, olivineclinopyroxenite, plagioclase clinopyroxenite, gabbro andquartz-bearing gabbro. Cycle II is 190 m thick and mainlyconsists of plagioclase-bearing peridotite, olivine clinopy-

roxenite, gabbro and quartz-bearing gabbro, while CycleIII is greater than 600 m thick, and is dominated by plagio-clase clinopyroxenite, gabbro and quartz diorite. A �20 m-thick fine-grained gabbroic and olivine-gabbroic MarginalUnit is at the base of the intrusion and in contact withthe country rocks (Mao and Sun, 1981), containing up toseveral percent hornfelsed and partially digested inclusionsof the underlying Emeishan basalts. The petrographic fea-tures of the different rock types within each individual cyclehave been described in detail by Zhou (1982) and Zhonget al. (2004).

In the Xinjie intrusion, the Fe–Ti oxide ore layers occurmainly at the top of Cycles I and II, composed of Ti-bear-ing chromite, Ti-bearing chrome-magnetite, magnetite andilmenite (Fig. 2), whereas the stratiform-type PGE mineral-ization is located in the Marginal Unit and the lower part ofthe intrusion where it is associated with disseminated cop-per and nickel sulfides with interbedded thin Ti-bearingchrome-magnetite and Ti-bearing chromite layers (Luo,1981; Zhu et al., 2010). In this study, our samples comefrom borehole ZK411 that intersected Cycle I of the Xinjieintrusion, which comprises a rock package about 380 mthick and includes the main PGE mineralization occur-rences. The location of borehole ZK411 is shown inFig. 1 and the positions of the samples are given in Table1. Four major PGE-enriched sulfide ore layers (PGE Layer1 to Layer 4; Fig. 2) were discovered in borehole ZK411,although an additional layer of PGE mineralization alsooccurs within the uppermost unit of this drill hole. Thedominant PGE-bearing layered sequence has been dividedinto four units (Fig. 2). It should be pointed out that asthe samples were collected primarily to study the PGE min-eralization occurrences, the proportion of mineralized sam-ples is not representative of the core as a whole, as moresamples were taken in mineralized sections. In the followingdiscussion, we will focus on the main Cu–Ni–PGE sulfidemineralization occurrences, which are hosted by plagioclaseperidotite and plagioclase clinopyroxenite in the lower partof Cycle I. These rocks consist of cumulus olivine in modalamounts of up to 50%, titanaugite (15–60%), Ti-bearingchromite and/or chrome-magnetite (5–15%), and intercu-mulus titanaugite (5–40%) and plagioclase (10–30%).

The stratiform PGE mineralization in the Xinjie intru-sion occurs in the form of disseminated PGE-rich sulfides.The sulfide content within the PGE mineralization zoneranges from 0.1% to 1%, and locally, up to 2%. The domi-nant base-metal sulfides (BMS) comprise chalcopyrite (50–60%), pyrrhotite (20–25%), and pentlandite (15–20%). Sper-rylite and Pd–Pt–Bi–Te minerals (merenskyite, moncheite,and michenerite) are present in the PGE-enriched layers.The contents of the Fe–Ti oxides correlated with PGE min-eralization vary from 5% to 15%, and in places, up to 20%.These platinum-group minerals (PGMs) are commonlyassociated with the BMS, or magnetite coexisting withBMS in the PGE mineralization zone (Zhu et al., 2010).

4. ANALYTICAL METHODS

Platinum, Pd, Ir, and Ru were determined by isotopedilution (ID)-ICP-MS using an improved Carius tube tech-

Fig. 2. Variations of Mg#, Cr/FeOT, Cr/TiO2, Cu/Zr, Cu/Pd, Pt, Pd, Pt + Pd, Cu, Ni, S, and Pt/S with depth in the main PGE mineralizationhorizon within the Xinjie intrusion. Stratigraphy of the Xinjie intrusion is modified after Zhong et al. (2004).


nique (Qi et al., 2007). The mono-isotope element Rh wasmeasured by external calibration using a 194Pt spike asthe internal standard (Qi et al., 2004). Ten grams of rockpowder and appropriate amount of enriched isotope spikesolution containing 101Ru, 105Pd, 193Ir, 194Pt were digestedwith �35 ml aqua regia in a 75 ml Carius tube, which wasplaced in a sealed, custom-made, high pressure autoclave

filled with water. The internal pressure of the Carius tubeis balanced by the external pressure produced by the waterwhen heated. Thus, this method not only avoids a possibleexplosion of the Carius tube but also allows for relativelyhigh-temperature (300 �C) digestion, a greater volume ofaqua regia (35 ml) and a larger sample mass (10 g). Afterdigestion at 300 �C for 10 h, the solution was transferred

Table 1Major, trace and highly siderophile element distribution in the cumulates and sulfide ores from the Xinjie intrusion.

Sample Cyclicunit

Depth(m)

MgO(%)

FeOT(%)

TiO2(%)

Cr(ppm)

Zr(ppm)

Y(ppm)

Cu(ppm)

Ni(ppm)

S(ppm)

Ir(ppb)

Ru(ppb)

Rh(ppb)

Pt(ppb)

Pd(ppb)

HZK411-02 UpperUnit

77.0 24.71 20.42 3.67 2858 100 8.89 283 746 530 3.12 1.87 2.30 306 103

HZK411-04 78.0 26.92 17.60 3.13 2308 87.4 9.93 352 751 560 1.33 1.41 0.38 301 186HZK411-05 78.5 21.23 13.41 3.00 2045 97.9 15.5 243 521 280 0.90 0.92 0.45 263 183HZK411-06a 79.0 19.98 11.16 4.00 1360 98.6 15.9 75 421 100 7.59 6.71 9.60 445 507HZK411-42 129.73 22.23 14.09 5.17 1466 87.6 13.5 971 1192 1900 1.16 1.74 0.08 1.80 9.30HZK411-114 Unit 4 257.8 24.08 14.40 5.33 2272 109 11.7 379 1089 580 0.62 1.79 0.52 10.2 13.2HZK411-129 265.8 26.65 16.80 4.33 2842 92.6 10.7 754 1203 1600 2.64 4.24 1.28 32.8 36.0HZK411-156 278.3 19.09 15.30 5.00 1967 176 16.2 890 936 680 4.60 5.15 4.54 41.0 56.2HZK411-157 278.8 17.17 12.45 5.00 1505 153 18.0 666 753 2500 9.46 7.71 5.72 236 308HZK411-159a 279.5 16.67 10.40 3.27 1216 117 18.3 1428 769 2300 11.6 8.47 6.69 410 410HZK411-161 281.3 15.64 9.98 4.17 1627 125 19.5 1958 771 2300 12.6 10.1 7.32 185 225HZK411-162a 281.9 15.12 9.88 3.10 1345 139 17.5 2071 790 2000 32.6 22.2 57.6 470 944HZK411-163 282.4 14.31 9.59 4.07 1479 132 19.0 1574 653 3900 15.2 9.31 9.51 262 276HZK411-165 283.2 13.86 9.69 4.67 1178 138 19.3 1544 546 3800 9.00 6.04 5.50 347 311HZK411-166a 283.6 14.06 10.13 4.83 746 130 20.1 3415 777 3700 19.5 16.2 11.3 635 291HZK411-167 284.1 13.79 9.71 5.33 768 116 18.1 2937 749 4000 6.58 5.43 3.83 278 169HZK411-170 Unit 3 285.2 16.65 13.78 5.30 3069 129 15.8 921 710 760 2.89 3.70 2.04 141 132HZK411-171 285.8 19.25 13.00 4.83 2147 108 12.3 1157 846 130 3.76 4.33 2.26 123 101HZK411-178 289.7 18.15 11.60 5.33 1911 119 15.0 284 656 150 0.55 0.97 0.30 9.10 7.90HZK411-179 290.2 17.4 10.94 5.30 1589 108 13.7 383 660 280 1.20 1.08 0.98 53.2 53.5HZK411-180 290.8 15.17 8.38 4.17 1621 108 17.4 479 451 340 4.44 2.52 7.27 167 241HZK411-182 291.6 14.17 10.96 4.67 1649 219 16.0 1510 782 1900 1.83 2.89 1.21 45.6 90.0HZK411-183 292.2 14.52 8.61 3.83 1286 110 17.4 479 406 210 4.21 1.65 3.96 160 207HZK411-185 293.0 14.40 9.14 5.75 1168 125 19.6 316 355 160 3.61 1.53 3.08 142 160HZK411-188 294.8 13.41 9.09 5.00 929 115 18.7 278 347 100 5.24 1.87 4.53 108 91.1HZK411-191a 296.2 13.78 9.44 5.00 1132 118 19.0 1367 471 1300 17.0 8.63 12.9 416 525HZK411-193a 297.2 14.31 10.37 5.83 1054 121 16.9 2984 624 1300 30.7 15.8 22.9 707 1023HZK411-194a 297.7 15.29 10.78 4.83 906 95.9 14.6 2351 654 1200 36.6 18.1 36.9 680 1138HZK411-195a 298.2 12.94 9.70 4.25 822 100 15.5 3334 592 3600 19.9 9.47 23.0 547 852HZK411-196a 298.7 15.24 11.45 5.00 1039 88.8 14.3 5226 829 5800 35.9 19.1 46.1 875 1391HZK411-198 299.7 13.08 9.41 4.42 1212 128 19.1 355 357 220 5.47 2.01 5.49 169 192HZK411-199 Unit 2 300.1 15.08 12.48 5.83 1795 106 15.5 464 531 430 4.30 3.08 3.74 134 152HZK411-205 303.2 11.34 9.56 6.33 630 165 17.9 715 417 650 3.36 2.08 4.11 336 190HZK411-206 303.7 12.29 9.86 5.50 709 151 19.2 473 405 370 3.05 1.79 2.94 228 102HZK411-209 305.0 11.42 9.52 4.83 744 157 21.3 553 324 510 8.29 4.64 5.42 298 127HZK411-212a 306.5 12.60 10.20 6.50 1101 140 19.8 332 396 250 15.2 7.39 12.1 1236 566HZK411-215 308.1 12.95 9.79 7.67 1229 141 18.3 660 498 370 5.71 3.56 6.49 314 175HZK411-217a 309.0 12.52 8.48 4.17 1463 157 20.9 1494 579 1400 26.0 15.8 19.1 495 740HZK411-218 Unit 1 309.6 10.31 8.88 5.17 709 242 20.5 574 426 480 6.17 3.69 4.16 115 172HZK411-233 317.0 13.43 10.22 4.58 1119 105 16.9 6339 1395 3700 17.8 20.0 6.68 121 134HZK411-234 317.4 13.98 11.04 5.17 976 129 16.5 3774 872 4300 7.44 6.91 10.3 89.2 138

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to 50 ml centrifuge tube and then used for pre-concentrat-ing PGE by Te-coprecipitation, as described in Qi et al.(2004). The total procedural blanks were lower than0.003 ng/g for Ru, Rh and Ir; 0.020 ng/g for Pd; and0.010 ng/g for Pt. The reference standards, WPR-1,WGB-1 and TDB-1, were simultaneously used for analyti-cal quality control. The results for WPR-1 are in goodagreement with the certified values. The results of Ru,Rh, and Ir for WGB-1 and TDB-1 are lower than the rec-ommended values, but agree well with values reported byMeisel and Moser (2004). The analytical results of the sam-ples are given in Table 1.

Re–Os isotopic compositions of the Xinjie intrusion (Ta-ble 2) were determined at the State Key Laboratory ofLithospheric Evolution, Institute of Geology and Geophys-ics, Chinese Academy of Sciences (IGGCAS). The Cariustube digestion technique is similar to those described byShirey and Walker (1995), which is reported in detail byChu et al. (2009). Approximately 2 g of homogenizedwhole-rock powders and appropriate amounts of a187Re–190Os mixed spike were sealed in an externally cooled(�50 �C), single-use, Pyrex� borosilicate Carius tube, with3 ml of purified concentrated HCl and 6 ml of purified con-centrated HNO3. The Carius tubes were kept at �240 �C inan oven for 48–72 h. Osmium was extracted from the aquaregia solution into CCl4 (Cohen and Waters, 1996) and thenback-extracted into HBr, followed by purification via mic-rodistillation (Birck et al., 1997). Re was separated fromthe matrix and purified by anion exchange chromatographywith about 0.6 ml resin (AG 1 � 8, 100–200 mesh). Thesamples were loaded onto the columns in 0.8 mol/LHNO3, the matrix elements were eluted with 0.8 mol/LHNO3 and 1 mol/L HCl, and then the Re was collectedwith 8 mol/L HNO3. Os isotopic compositions were mea-sured using a GV Isoprobe-T Mass Spectrometer with neg-ative ion mode. Purified Os was loaded onto platinumfilaments and Ba(OH)2 was used as an ion emitter. All sam-ples were run with nine Faraday cups in static mode. TheOs isotopic compositions and Os concentrations were ob-tained in one mass spectrometric run. The measured Os iso-topic ratios were corrected for mass fractionation using192Os/188Os = 3.08271 after interference corrections, oxy-gen corrections and spike subtractions. The isotope dilutionanalyses of Re were conducted on a Neptune MC-ICP-MSusing a secondary electron multiplier in peak-jumpingmode. Mass fractionations for Re were corrected using aRe standard that was run alternately with the samples. To-tal analytical blanks were 2 pg for Re and 3–5 pg for Oswith a 187Os/188Os ratio near 0.150. The reference valuesfor the standard was 185Re/187Re = 0.5975. The in-run pre-cisions for Os isotopic measurements were better than±0.2% (2rm) for all the samples. During the period of mea-surements of our samples, the 187Os/188Os ratio of John-son–Matthey standard of UMD was 0.11380 ± 4 (2r,n = 5). To calculate the age, Re–Os data were regressedusing the ISOPLOT program (Ludwig, 2003) and assumingan error correlation coefficient of 0.9. Error input wasdetermined by multiple analyses of the in-house Os andRe standards to be 0.2% on Os isotopic composition and1% on Re/Os ratio. The errors of two samples (HZK411-

Table 2Re and Os isotopic data for the Xinjie intrusion.

Sample Re (ppb) Os (ppb) 187Re/188Os 187Os/188Os 2r (187Os/188Os)i cOs(t)

HZK411-04 0.838 2.531 1.5983 0.14302 0.00008 0.13611 8.6HZK411-06 0.325 0.694 2.2600 0.14078 0.00031 0.13101 4.6HZK411-129 1.424 7.320 0.9376 0.13009 0.00003 0.12604 0.6HZK411-157 1.372 21.26 0.3110 0.12592 0.00003 0.12458 �0.6HZK411-162 0.689 46.94 0.0707 0.12503 0.00001 0.12472 �0.4HZK411-166 1.458 35.36 0.1986 0.12538 0.00001 0.12452 �0.6HZK411-167 1.123 13.55 0.3992 0.12622 0.00001 0.12449 �0.6HZK411-183 0.719 4.451 0.7780 0.12837 0.00010 0.12501 �0.2HZK411-191 0.892 24.04 0.1789 0.12547 0.00001 0.12470 �0.5HZK411-196 0.798 81.70 0.0471 0.12476 0.00001 0.12455 �0.6HZK411-205 0.274 3.504 0.3774 0.12629 0.00003 0.12465 �0.5HZK411-212 0.337 9.344 0.1737 0.12521 0.00001 0.12446 �0.7HZK411-217 0.658 49.93 0.0635 0.12497 0.00001 0.12470 �0.5HZK411-218 0.671 9.961 0.3246 0.12620 0.00001 0.12480 �0.4HZK411-234 1.302 41.88 0.1498 0.12534 0.00001 0.12469 �0.5HZK411-239 0.579 599.2 0.0047 0.12459 0.00001 0.12457 �0.6HZK411-243 1.304 12.08 0.5203 0.12689 0.00002 0.12464 �0.5HZK411-246 0.400 16.85 0.1142 0.12494 0.00007 0.12444 �0.7


196 and 239) having quite high Os concentrations were as-sumed to be 5% on Re/Os ratio.

Major elements were measured by wet chemical analysesat the Center of Analysis and Test, Institute of Geochemis-try, Chinese Academy of Sciences (CATIGCAS), with theanalytical precision better than 5%. Sulfur was analyzedat the CATIGCAS by Leco induction furnace-titration,with the accuracy better than 10%. Trace elements weredetermined using a VG PQ Excell inductively coupled plas-ma mass spectrometer (ICP-MS) at the University of HongKong. The powdered samples (50 mg) were dissolved inhigh-pressure Teflon bombs using HF + HNO3 mixturefor 48 h at �190 �C (Qi et al., 2000). Rh was used as aninternal standard to monitor signal drift during counting.The international standards AMH-1, GBPG-1 and OU-6were used for analytical quality control. The analytical pre-cision is generally better than 5% for trace elements. Thecontents of selected major and trace elements are listed inTable 1. The complete major and trace element dataset ispresented in Electronic Annex.

5. RESULTS

5.1. Variations in major and trace elements

All the studied samples from the Xinjie intrusion arecharacterized by high but variable MgO (10.3–26.9 wt.%),FeOT (8.38–20.4 wt.%) and TiO2 (3.00–7.67 wt.%) contents(Table 1). Variations in Mg-number (Mg#), Cr/FeOT andCr/TiO2 ratios with stratigraphic height are shown for themain PGE mineralized horizon of the Xinjie intrusion inFig. 2. The samples from cyclic Units 1, 3 and 4 displayconsistently increasing trends in Mg# followed by steadilydecreasing trends upwards, whereas those from cyclic Unit2 exhibit a decreasing trend in Mg# upsection. It is interest-ing that abrupt reversals of Mg# occur at the tops of Units1, 2 and 3 (Fig. 2a). The samples from Units 1–4 have var-iable Cr contents of 551–1262 ppm, 630–1795 ppm, 822–

3069 ppm, and 746–2842 ppm, respectively. In contrast,the cumulate rocks and PGE ores from Upper Unit exhibithigh Cr contents (1360–2858 ppm; Table 1). Notably, muchhigher Cr/FeOT and Cr/TiO2 ratios occur immediately be-low the PGE Layers 2, 3 and 4, while those in cyclic Unit 1are relatively constant and low (Fig. 2b and c).

5.2. Variations in chalcophile elements and PGE

As shown in Fig. 2, four major PGE-rich sulfide layersoccur near or at the bottom of each cyclic unit. The Cu,Ni, PGE and sulfur contents of the PGE-enriched layersand their host lithologies vary by two to three orders ofmagnitude (Table 1). Sulfur concentrations are highest inUnit 1 (3300–9700 ppm), with the exception of one sample(480 ppm S) in the uppermost part of this unit. Apart fromone ore sample (HZK411–217) with a S content of1400 ppm, most host rocks and PGE-rich sulfide ores with-in Unit 2 contain significantly less sulfur (250–650 ppm).The PGE ores in Unit 3 have much higher sulfur concentra-tions (1200–5800 ppm) than the cumulate rocks (100–760 ppm), with one exceptional rock sample containing1900 ppm S. The cumulate rocks and PGE-rich sulfide oreswithin Unit 4 are mostly rich in sulfur (1600–4000 ppm) ex-cept two rock samples with 580–680 ppm S. In addition, thesamples from Upper Unit contain significantly lower sulfurfrom 100 to 560 ppm, with the exception of one sample(HZK411-42) having 1900 ppm S.

Copper concentrations exhibit a similar distribution pat-tern as sulfur (Fig. 2), with elevated Cu concentrations inthe PGE-rich sulfide ores and sulfide-enriched cumulaterocks. Apart from two ore samples (HZK411-212 andHZK411-06) having significantly lower Cu contents (332and 75 ppm), the ores from the PGE Layers 1, 3 and 4and one from the PGE Layer 2 (HZK411-217) are charac-terized by high Cu contents between 1367 and 5476 ppm(Table 1; Fig. 2i). In contrast, the S-poor (


mostly 100 ppb; Fig. 2h). Moreover, it is notable thatabundant PGE-enriched rocks (several hundred ppbPt + Pd) and two ore samples (HZK411-06 and HZK411-212) are relatively poor in S (100–760 ppm) and Cu (243–1157 ppm, mostly

Fig. 4. Cr vs. Ir, Ru, Pt, and Pd for the Cr-rich, sulfide-bearing and sulfide-poor samples from the Xinjie intrusion.


shaped PGE patterns, characterized by significant Ni deple-tion, obvious Pd enrichment relative to Cu, and a markedfractionation between Os, Ir and Ru on the one and Rh,Pt and Pd on the other. These samples have Cu/Pd ratios(148–8710) similar to or lower than that of the mantle(1000–10,000; Barnes et al., 1993). In contrast, several sam-ples from Unit 1 (HZK411-233 and HZK411-234), Unit 3(HZK411-171, HZK411-178 and HZK411-182), Unit 4(HZK411-114, HZK411-129, HZK411-156, HZK411-166and HZK411-167) and Upper Unit (HZK411-42) exhibitobvious Pd depletion relative to Cu (Fig. 3), which haveCu/Pd ratios (11,455–104,773) greater than that of themantle. Interestingly, the sharp increases of Cu/Pd ratiosoccur immediately above the PGE Layers 1, 3 and 4(Fig. 2e). It is also noteworthy that most ores and cumulaterocks within Units 1–4 show obviously negative Ru anom-alies (Fig. 3a–d), with the exception of three samples(HZK411-114, HZK129 and HZK411-178).

Throughout the section of the intrusion examined, Ir,Ru, Pt and Pd of the Cr-rich, sulfide-poor and sulfide-bear-ing samples exhibit poor correlations with Cr (Fig. 4a–d).In contrast, the variations in Cu, Pt, Pd, Ir and Ru concen-trations correlate well with S, whereas Ni poorly correlateswith S (Table 1; Fig. 5).

5.3. Re–Os isotope

Re–Os isotope data for the Xinjie intrusion are reportedin Table 2 and plotted on the Re–Os isochron diagram inFig. 6. The Xinjie cumulate rocks and PGE-rich sulfide oresexhibit high but variable Os contents (0.694–81.7 ppb), withsample HZK411-239, at 599 ppb being an exception. Incontrast, Re concentrations are low in the range of 0.274–1.46 ppb. Most samples have near-chondritic initial Os iso-topic compositions, with cOs(t) values (corrected to 259 Ma)ranging from �0.7 to �0.2 and 187Re/188Os ratios varying

from 0.005 to 0.778 (Table 2). Exceptions include the twouppermost samples from the Upper Unit (HZK411-04and HZK411-06) and HZK411-129 from Unit 4 (Table 2)which have slightly higher initial 187Os/188Os (0.1260–0.1361), with radiogenic cOs(t) values (+0.6 to +8.6) andhigher 187Re/188Os ratios (0.938–2.260). All data, exceptfor the three uppermost samples and sample HZK411-183which have slightly elevated 187Re/188Os (0.778–2.260), de-fine an isochron age (MSWD = 0.8) of 262 ± 27 Ma(Fig. 6) that is consistent, within the uncertainty, with theSHRIMP U–Pb zircon age of the Xinjie intrusion(259 ± 3 Ma; Zhou et al., 2002). The calculated initial187Os/188Os of 0.12460 ± 0.00011 (cOs(t) = �0.5 ± 0.1) isapproximately chondritic for Permian and attests to mini-mal crustal contamination.

The high Os and low Re contents and chondritic Oscomponent of the Xinjie intrusion are quite similar to thoseof the Lijiang picrites (Fig. 7;

Fig. 5. Covariations of Cu, Ni, and PGE with sulfur content in the Xinjie intrusion. Cu and PGE exhibit positive correlations with S, whereasNi shows poor correlation with S.


et al., 1999), Stillwater complex (cOs(t) = 2.0–16.4; Horanet al., 2001) and Noril’sk-Talnakh intrusion (cOs(t) = 1.9–71; Walker et al., 1994; Arndt et al., 2003) (Fig. 7), whichhave been proposed to reflect outer core or recycled oceaniccrust contributions (Walker et al., 1994), or crustal assimi-lation processes (McCandless et al., 1999; Horan et al.,2001; Arndt et al., 2003; Tao et al., 2007, 2010).

Fig. 6. 187Re/188Os vs. 187Os/188Os isochron figure for the Xinjieintrusion. Insert includes all the analyzed samples but four sampleshaving slightly radiogenic Os compositions are excluded from ageplotting. Analytical uncertainties are the size of the symbols orsmaller.

Fig. 7. cOs(t) vs. Os concentration for magmatic sulfides showingdata for Cu–Ni–PGE mineralization from the Xinjie (this study),Jinbaoshan (Tao et al., 2007), Limahe (Tao et al., 2010), NT:Noril’sk-Talnakh (Walker et al., 1994; Arndt et al., 2003), Bushveld(McCandless et al., 1999) and Stillwater (Horan et al., 2001)intrusions. Data for the Lijiang picrites, Song Da komatiites andEmeishan basalts (HTB: high-Ti basalt; LTB: low-Ti basalt) arefrom Zhang et al. (2008), Hanski et al. (2004) and Xu et al. (2007).Samples with cOs(t) > +120 are not plotted in this figure for clarity.


6. DISCUSSION

6.1. Estimation of a Xinjie parental melt composition

The parental magma compositions of the Xinjie intru-sion can be obtained using the compositions of the chilledmargins. Previous study has shown that one fine-grainedolivine-bearing gabbro sample (CSXJ26) from the MarginalUnit within the Xinjie intrusion has high MgO (14.6%),FeOT (15.5%), and TiO2 (3.6%) contents (Zhong et al.,2004), This sample is also characterized by the highest Yconcentration of 17 ppm (Fig. 8a), indicating that it containdistinctly more trapped liquid than other samples in theMarginal Unit. Sample CSXJ26 can be then taken as a mix-ture of the primary magma and cumulus olivine. The mostprimitive olivine observed in the Xinjie chilled margins con-tains 84 mol percent Fo (Mao and Sun, 1981). Fig. 8b illus-trates the compositions of the Xinjie parental meltestimated from the method of Chai and Naldrett (1992).The coexisting liquid calculated using the ratio of (FeO/MgO)olivine/(FeO/MgO)liquid = 0.3 (Roeder and Emslie,1970) contains 13.9 wt.% MgO and 15.8 wt.% FeO. The cal-culated MgO content and 17 ppm Y of the initial liquid areapplied to model the fractionating liquid changes usingMELTS (Ghiorso and Sack, 1995). The model line roughlyaccounts for the compositional variations in the high-Ti

Fig. 8. (a) Plot of MgO vs. Zr in the Xinjie chilled margin samplesand Emeishan basalt wall rocks (Zhong et al., 2004); (b) modelingof primary olivine and coexisting liquid composition. Point A is thecomposition of olivine Fo84 for the Xinjie chilled margins (Maoand Sun, 1981). Point B is the compositions of a fine-grainedolivine-bearing gabbro from the Xinjie chilled margins (Zhonget al., 2004). Point C is the estimated compositions of trappedliquid in equilibrium with olivine Fo 84 for the Xinjie intrusion.

Emeishan basalt wall rocks of the Xinjie intrusion(Fig. 8a; Zhong et al., 2004), suggesting that the Xinjieparental magma could share a common mantle source withthe nearby high-Ti basalts.

The Xinjie cumulate rocks are also enriched in highlyincompatible lithophile elements (Zhong et al., 2004).Therefore, the mantle source of the Xinjie parental magmashould have unusually high FeO and TiO2 contents andenrichment of highly incompatible elements. The composi-tions are comparable to those of the coeval Lijiang picritesin the ELIP, which are enriched in MgO (12.3–27.0%),FeOT (11.6–17.6%) and TiO2 (1.14–2.36%; Zhang et al.,2006). The Xinjie intrusion also exhibits similar primitivemantle-normalized PGE distribution patterns (Fig. 3) tothose of the Lijiang picrites (Zhang et al., 2005), character-ized by enrichment of Pt and Pd relative to Os, Ir and Ru.Moreover, the near-chondritic initial Os isotope values formost Xinjie samples (Table 2) show no effects of crustalcontamination, similar to those of the Lijiang picrites(Zhang et al., 2008; Fig. 7).

It has been suggested that the high temperature, highmagnesium komatiitic and picritic magmas injected intothe upper crust are the only types of magmas that can formthe major magmatic Ni–Cu–PGE sulfide deposits in theworld, which are generally S-undersaturated due to high de-grees of partial melting or derivation from a S-poor plumesource (Keays, 1995; Arndt et al., 2005). The modeling ofNaldrett (2010) has also shown that only a magma gener-ated by high degree of melting (P15%) would be rich inPGE and Cu, implying that the Xinjie parental magmawas derived through high-degree partial melting of theELIP mantle source. As demonstrated above, the occur-rence of Cu–Ni–PGE and Fe–Ti–V mineralization withinthe Xinjie intrusion thus requires that the parental magmasare not only enriched in Fe and Ti but also in magnesium,incompatible elements and PGE, which have similarities tothe characteristics of the ferropicritic magmas (e.g., Brüg-mann et al., 2000; Hanski et al., 2001).

6.2. PGE behavior during the evolution of the Xinjie magma

The layered series of the Xinjie intrusion are cumulaterocks and as such the minerals they accumulate dominantlycontrol their major and trace element compositions. In theCr-rich, sulfide-poor and sulfide-bearing samples, Ir, Ru, Ptand Pd are negatively correlated with Cr (Fig. 4), showingthat these elements are unlikely to be controlled by chro-mite during crystal fractionation. Instead, the PGE concen-trations exhibit broadly positive correlations with S(Fig. 5), suggesting that disseminated sulfide could be themain collector phase. This is confirmed by the observationthat the Xinjie platinum group minerals (PGMs) are mostlyhosted in the base metal sulfides (Zhu et al., 2010). Notably,the occurrence of significantly higher Cr/FeOT and Cr/TiO2ratios immediately below the PGE Layers 2, 3 and 4(Fig. 2b and c) reflects chromite or Cr-spinel accumulationbefore sulfide deposition.

As pointed out by Li and Naldrett (1999) for the Voi-sey’s Bay intrusion, the Cu/Zr ratio is a good measure ofchalcophile depletion. Most of the analyzed samples (except


HZK411-06) have Cu/Zr ratios higher than 2.0, suggestingthat cumulus sulfides are present almost throughout theexamined package. Meanwhile, the increase of Cu/Zr ratiowith height in Unit 1 reflect increasing sulfide/trapped sili-cate liquid ratios, whereas the Cu/Zr ratios decrease up-ward in Units 3 and 4 imply decreasing sulfide/trappedsilicate liquid ratios. In Unit 2, the Cu/Zr ratios slightly de-crease from the PGE Layer 2, implying insignificant varia-tions in sulfide/trapped liquid ratio. The Cu/Pd ratio isparticularly sensitive to S-saturation because Pd has a muchlarger partition coefficient than Cu (Barnes et al., 1993). Inthe present study, most samples have Cu/Pd ratios close toor lower than that in primitive mantle (Fig. 2e), furtherindicating that they contain varying amounts of cumulussulfides. In contrast, several samples above the PGE Layers1, 3 and 4 having Cu/Pd ratios significantly higher than themantle value, suggesting their crystallization from differen-tiated magma that had experienced prior sulfide liquid seg-regation. The sharp increases in Cu/Pd ratio above thesePGE Layers (Fig. 2e) support the derivation of at leastsome of the PGE within the sulfide-enriched layers fromthe overlying magma.

As shown above, the marked PGE depletion in thecumulate rocks upsection and downsection of the mainPGE-rich layers is lacking in the Xinjie intrusion (Pt + Pdmostly >100 ppb; Fig. 2h). The rocks overlying the Meren-sky Reef within the Bushveld Complex are depleted in PGErelative to Ni and Cu, which is interpreted as a result ofPGE extraction from the overlying magma (Maier andBarnes, 1999; Barnes and Maier, 2002). The absence of con-sistent PGE depletion in most of the Xinjie host rocks indi-cates that they formed in an open magmatic system. It mayoccur in a dynamic conduit system (Li et al., 2000; Evans-Lamswood et al., 2000) due to metal upgrading of earlyformed sulfide melt by continued influx of the later, fresh,sulfide-unsaturated and PGE-undepleted magma (Kerrand Leitch, 2005). Another important observation thatsome PGE-rich ores and PGE-enriched cumulate rocksfrom various units within the Xinjie intrusion are poor inS (

Table 3Modeling of the Ni, Cu and PGE compositions of the sulfides in the Xinjie intrusion.

Ni (%) Os (ppb) Ir (ppb) Ru (ppb) Rh (ppb) Pt (ppb) Pd (ppb) Cu (%)

Parental magmaa 0.025 0.70 0.42 0.30 0.43 10.3 8.2 0.008D sulfide liquid/silicate liquidb 300 35,000 35,000 35,000 35,000 35,000 35,000 1000R = 8000 7.23 4559 2735 1954 2800 67,078 53,402 7.112% sulfide 0.145 91 55 39 56 1342 1068 0.142R = 5000 7.08 3063 1838 1313 1882 45,072 35,882 6.672% sulfide 0.142 61 37 26 38 901 718 0.1330.5% sulfide 0.035 15.3 9.2 6.6 9.4 225 179 0.0330.2% sulfide 0.014 6.1 3.7 2.6 3.8 90 72 0.013R = 1000 5.78 681 409 292 418 10,024 7980 4.000.5% sulfide 0.029 3.4 2.0 1.5 2.1 50 40 0.020

a Ni, Cu and PGE compositions of the parental magma are similar to those of the pyroxene-phyric basalts in the ELIP (Zhang et al., 2005;Zhong et al., 2006).

b Assuming Dsulfide liquid/silicate liquid of 35,000 for the PGE (Peach et al., 1994; Fleet et al., 1999), 1000 for Cu, and 300 for Ni (Francis, 1990).

Fig. 9. Re/Os ratio vs. Os concentration for magmatic sulfides(recalculated 100% sulfide according to Barnes and Lightfoot,2005) in the Xinjie intrusion. Data for the Lijiang picrites and SongDa komatiites are from Zhang et al. (2008) and Hanski et al.(2004). Modeling of the sulfide liquid R factor enrichment processis conducted using Re concentration of 0.15 ppb and Os concen-tration of 0.70 ppb, similar to those of the pyroxene-phyric basaltsin the ELIP (Zhang et al., 2005, 2008) and assuming that DRe is1000 and DOs is 35,000 (similar to Lambert et al., 2000).


fractionation dominated by olivine with minor clinopyrox-ene and Cr-spinel. We therefore take the Ni, Cu and PGEcompositions of the least-contaminated pyroxene-phyricbasalts in the ELIP (Zhang et al., 2005; Zhong et al.,2006) to represent the original composition of the Xinjie sil-icate liquid (Table 3). The Dsulfide liquid/silicate liquid of 35,000for the PGE (Peach et al., 1994; Fleet et al., 1999), 1000 forCu, and 300 for Ni (Francis, 1990) is used for modeling.

The compositions of the whole-rocks in Unit 1 and Unit3 may be modeled as assuming that they contain 0.5% sul-fides at R = 1000 and 2% sulfides at R = 8000, respectively(Fig. 3a and c). Using a sulfide liquid formed in equilibriumwith the melt at R = 5000 and allowing 0.2–2% cumulussulfides (Fig. 3b) it is possible to model the whole-rockcompositions in Unit 2. The compositions of the samplesin Unit 4 are similar to the model compositions containing0.5–2% sulfides at R = 5000. The modeled sulfide contentspresented here are consistent with the petrographic obser-vation for the analyzed samples. Modeling of the sulfide li-quid R factor enrichment process is also conducted usingRe concentration of 0.15 ppb and Os concentration of0.70 ppb and assuming that DRe is 1000 and DOs is 35,000(similar to Lambert et al., 2000). The calculated results(Fig. 9) show that most Cu–Ni sulfides (100% sulfide) inthe Xinjie intrusion correspond to R factors between 1000and 10,000, comparable to those shown in Fig. 3. The mod-erate to high R factors (1000–8000) suggested for the dis-seminated sulfides in the Xinjie PGE ores and silicaterocks indicate that the sulfide droplets interacted with alarge volume of magma in an open-system magmachamber.

As mentioned above, some samples overlying the PGELayers 1, 3 and 4 possess Cu/Pd significantly above mantlelevels and thus are depleted in PGE relative to Cu (Fig. 3).Their compositions can be explained by small amounts ofsulfide extraction, which are estimated from the followingmass balance equation (Barnes et al., 1993; Thériaultet al., 2000): S = 100(Cs/CL � 1)/(D � 1), where Cs, CLand D are the same as the above expression and S repre-sents the amounts of segregated sulfides in weight percent.Assuming that the initial magma had a Cu/Pd value of9800 and Dsulfide liquid/silicate liquid for Cu and Pd are 1000and 35,000, respectively (Table 3), calculations show that

0.0004–0.028% sulfides may have been removed from themagma prior to the formation of these samples.

6.4. Petrogenesis of the PGE-rich sulfides

The much higher Mg#, Cr/FeOT and Cr/TiO2 ratiosimmediately below the PGE Layers 2, 3 and 4 define thesharp geochemical reversals (Fig. 2a–c), providing the clearevidence for an open-system behavior characterized bymagma replenishment episodes in the Xinjie intrusion.Moreover, the marked Cu/Zr ratio decrease from eachPGE ore layer within Units 2, 3 and 4 (Fig. 2d), indicatesthat sulfide accumulated from each new magma pulse. Fur-thermore, the lack of consistent PGE depletion with heightpresented here suggests that the sulfides have segregatedfrom successive surges of fertile magma. Collection of met-als by sulfides formed at moderate to high R factors (1000–8000) occurred widely within these cyclic units, also imply-


ing that the Xinjie PGE mineralization formed in an extre-mely dynamic system. New pulses of magma apparently flo-wed through the Xinjie magma chamber, which wouldinteract with pools of sulfide that had accumulated earlierand transfer chalcophile elements from the magma to thissulfide. The fact that the basalts immediately overlyingthe Xinjie intrusion display significant PGE depletion(Zhong et al., 2006) strengthens the hypothesis, that thesehave been derived from the parental magma that was inequilibrium with the Xinjie PGE-rich sulfides. The Xinjieintrusion shows a close relationship to the N–S-trendingfaults and intruded the Emeishan basalts (Fig. 1), indicatingthat the locus for the sill-like intrusion may have acted as adynamic conduit system for the magmas.

In the sulfide collection model, the mixing of the residentmagma and a new injection of magma has been invoked toexplain sulfide-enriched horizons in layered intrusions(Campbell et al., 1983; Naldrett et al., 1986; Barnes andMaier, 2002). In the case of the Xinjie samples, the abovediscussion indicates that the PGE Layer 1 was generatedby the normal accumulation of PGE-rich sulfides, whereasthe PGE Layers 2, 3 and 4 were formed by multiple re-charges of magma and resultant sulfide segregation. Irvine(1977) demonstrated that the mixing of a new liquid withthe resident magma can initiate the precipitation of exten-sive stratiform chromite and/or sulfide enrichments in largelayered intrusions. In the Xinjie intrusion, several thin Ti-bearing chromite and Cr-bearing magnetite layers occurimmediately below the PGE Layers 2, 3 and 4, consistentwith their much higher Cr/FeOT and Cr/TiO2. We thereforesuggest that a fresh injection of magma mixed vigorouslywith the resident magma in the Xinjie chamber, leadingto the crystallization of Cr-spinel and slightly decreasingFeO in the melt. Subsequently, relatively abundant magne-tite and ilmenite grains formed by early crystallization fromthe magma (Wang et al., 2008), which significantly removedFeO from the melt. This process resulted in a significant de-crease in the solubility of sulfide in the ferropicritic melts(Haughton et al., 1974) and thus caused separation of sul-fide which thereafter scavenged Cu, Ni and PGE from thesilicate magma. The sulfide droplets settled and accumu-lated at specific stratigraphic horizons to form the PGEore layers in the Xinjie intrusion. Subsequent reaction ofthe sulfides with new magma gave rise to the high R-factorsmentioned above. As a result, multiple layers of the Xinjiemineralized rocks can be explained by periodic magma re-charge and mixing. Every replenishment event fed fromthe bottom stirred up the previously accumulated sulfideliquids, and the entrapped sulfides equilibrated with thenew hybrid composition of the silicate magma (Li et al.,2009). Some of the Xinjie samples have lost S, which couldhave happened when the cumulus pile was reheated by afresh injection of magma. Consequently, successive batchesof magma passing through the Xinjie chamber dissolvedFeS, leaving the residual sulfide progressively more en-riched in Ni, Cu and PGE.

In summary, PGE Layer 1 originated from the accumu-lation of PGE-rich sulfides, whereas PGE Layers 2–4formed from mixing between evolved and primitive ferropi-critic magmas, all of which had experienced multiple mag-

ma replenishment events. The locus for the Xinjieintrusion acted as a magma conduit that processed suffi-cient amounts of silicate liquid, thus providing a potentialmechanism for concentrating PGE in the disseminatedsulfides.

6.5. The Xinjie and ELIP mantle source in a global context

The above demonstration links the generation of thePGE-rich disseminated sulfides to the evolution of theparental ferropicritic magmas, suggesting that the plume-derived ferropicritic magmas produced not only the Cu–Ni–PGE mineralization but also the Fe–Ti–V oxide ore-bearing layers in the Xinjie intrusion. The Re–Os age ofthe Xinjie intrusion is in good agreement with the data re-ported from the zircon U–Pb isotope system, implying thatthe Re–Os system remained closed for most samples afterthe intrusion emplacement. Three samples from UpperUnit have slightly radiogenic cOs(t) values (+0.6 to +8.6),suggesting that they were subjected to minor contaminationwith the overlying basalts. Previous studies have also indi-cated that the floor and roof rocks in the Xinjie intrusionwere slightly contaminated by the Emeishan basalts of thecontact zone (Zhong et al., 2004; Zhang et al., 2009), as evi-denced by the Sr–Nd–O isotopic compositions as well assome trace elemental ratios (e.g., Rb/La and Ba/Th). TheXinjie mafic–ultramafic rocks have initial Os isotope ratiosthat are within error of the initial ratios for the Lijiang pi-crites (Zhang et al., 2008) and Song Da komatiites (Hanskiet al., 2004) in the ELIP, suggesting that the intrusion pre-serves the primary Os isotope characteristics of plume-de-rived magmas. A rather constant initial 187Os/188Os in theXinjie samples throughout the dominant sequence and aslightly subchondritic cOs(t) of �0.5 ± 0.1 imply that theEmeishan plume source evolved with a long-term nearlychondritic Re/Os ratio.

In order to trace the 187Os/188Os isotopic evolution ofthe mantle over geological time, a compilation of initialOs isotopic compositions for ancient plume-derived komat-iites and picrites, along with the data of this study, is pre-sented in Fig. 10 to reflect those of contemporary mantlereservoirs. Data for most Archean and Paleoproterozoickomatiites including 3.46-Ga Pilbara komatiites (Bennettet al., 2002), 2.88-Ga Ruth Well komatiites (Meisel et al.,2001), 2.72-Ga Alexo and Pyke Hill komatiites (Gangopad-hyay and Walker, 2003; Puchtel et al., 2004), 2.70-Ga Kam-balda komatiites (Foster et al., 1996), and 2.43-Ga Vetrenykomatiites (Puchtel et al., 2001a) indicate roughly chon-dritic Os isotopic compositions and their derivation frommantle sources that evolved with time-integrated near-chondritic Re/Os ratios. However, the 2.8-Ga Kostomuk-sha komatiites (Puchtel et al., 2001b), 2.7-Ga Belingwekomatiites (Walker and Nisbet, 2002), and 1.98-Ga Pech-enga ferropicrites (Walker et al., 1997) exhibit high positivecOs(t), implying that they were derived from a mantle sourcewith a long-term suprachondritic Re/Os ratio and requiredthe ancient incorporation of the outer core material (Walk-er et al., 1995). Additionally, the 2.7-Ga Boston Creekkomatiites have subchondritic Os isotopic compositionsthat were suggested to be derived from subcontinental

Fig. 10. Initial cOs vs. age (in Ga) for presumed plume-derivedkomatiites, picrites and Xinjie intrusion. The horizontal dashed linerepresents the evolution of the chondritic average. Abbreviations:RW: Ruth Well; Bos: Boston Creek; Kam: Kambalda; Ale: Alexo;PH: Pyke Hill; Vet: Vetreny; Gor: Gorgona; Cur: Curacao. Shownfor comparison is the range of compositions that have beenreported for modern ocean island basalts (OIBs; compiled byWalker et al., 1997). See text for references.


lithospheric mantle (Walker and Stone, 2001). It is notablethat radiogenic Os signatures of the 1.1-Ga Keweenawanpicrites were inferred to originate from mantle containingrecycled oceanic crust from late Archean subduction (Shi-rey, 1997).

In contrast, the database for Phanerozoic picrites andkomatiites yielded an increasing complex picture of mantleevolution. For example, the 260-Ma picrites (Zhang et al.,2008), komatiites (Hanski et al., 2004) and Xinjie mafic–ultramafic intrusion (this study) in the ELIP indicate aslightly subchondritic Os isotopic composition, of whichrespective source will be discussed later. The 250-Ma Sibe-rian picrites however have suprachondritic cOs(t), consistentwith their derivation from a mantle plume that experiencedcore–mantle interaction (Horan et al., 1995; Walker et al.,1995). Moreover, the 89-Ma Gorgona komatiites show alarge range in cOs(t) (Walker et al., 1999; Brandon et al.,2003), whereas the contemporaneous Curacao picrites havevery uniform initial cOs values (Walker et al., 1999). The Osisotopic results indicate a heterogeneous plume, comprisingone Os reservoir with a composition very similar to thechondritic average and one with long-term enriched Re/Os. The 187Os and 186Os-enriched component for the Gorg-ona and Curacao komatiites and picrites would require amechanism that could transfer Os from the outer core tothe lower mantle (Walker et al., 1999; Brandon et al.,2003). In comparison, it was proposed that the 60-Ma WestGreenland and Baffin Island picrites, that were derivedfrom the onset of the proto-Iceland plume with chondriticto slightly suprachondritic Os isotopic compositions(Schaefer et al., 2000; Dale et al., 2009), reflect the mixingof depleted MORB mantle, recycled oceanic crust and high3He/4He primitive mantle. The large variations in187Os/188Os ratios for the picrites from the Hawaiian volca-nic centers require long-term differences in the Re/Os ratiosof the source regions. Lassiter and Hauri (1998) attributedthe 187Os/188Os variations to the addition of recycled oce-

anic mafic crust and/or sediments in the Hawaiian plumesource, whereas Brandon et al. (1999) proposed thatcore–mantle interaction could account for some of the187Os enrichment observed in some volcanic centers. The30-Ma Ethiopian picrites have unradiogenic but broadlychondritic Os isotopic compositions, implying that theywere generated during the initial turbulent ascent of theAfar plume head form pyroxene rich veins in a peridotitematrix (Rogers et al., 2010). As shown above, the featureof the dataset indicates that Os isotopic heterogeneity inplume-related materials is present as early as 2.7 Ga. Themechanism for long-term Os isotopic heterogeneity of var-ious plume sources will not be elucidated until better under-standings of the Earth differentiation, mantle dynamics, Re(Pt) and Os behavior during melting are achieved and thereis a better knowledge of high-pressure, high-temperaturepartitioning between mantle silicates and metal.

Previous studies have shown that the Lijiang picrites,Song Da komatiites and uncontaminated Xinjie rocks hadpositive initial eNd values (+1.0 to +7.5; Hanski et al.,2004; Zhang et al., 2008, 2009), implying that their mantlesources recorded a long-term depletion in LREE after previ-ous episodes of melt extraction. This is true for the LREE-depleted Song Da komatiites as well as the LREE-enrichedLijiang picrites and Xinjie samples, although the lattershould also have experienced a subsequent LREE enrich-ment event. The suggestion reconciles with Re depletion in-ferred from the slightly subchondritic Os isotopiccompositions of the Lijiang picrites, Xinjie rocks and someSong Da komatiites. Hanski et al. (2004) proposed thatthe Song Da komatiitic rocks had been subjected to 1–2%contamination with Proterozoic crust, which would have re-duced the extent of the Re depletion. The mantle Re–Os sys-tematics are much less sensitive to extraction of low-degreemelts than the Sm–Nd systematics due to the less incompat-ible behavior of Re compared to Nd (Puchtel et al., 2004),consistent with the effect of prior melting events on theSm/Nd and Re/Os ratios in the ELIP source. The dominant,slightly subchondritic Os isotopic component for the ELIPis similar to that of the depleted mantle source of midoceanridge basalts (DMM; Walker et al., 2002). However, Herz-berg and O’Hara (1998) considered that it was difficult toenvision a mechanism for heating the DMM to sufficienttemperatures at the 3–4 GPa pressure necessary to generatethe komatiites and picrites, particularly on the scale of thevolumes estimated for the LIPs. The Os isotopic composi-tions of the Emeishan plume source could also be recycledoceanic lithosphere that experienced a similar depletion his-tory as the DMM. It has been speculated that the depletedoceanic lithosphere that descended to the core–mantle inter-face could then subsequently have become entrained in anascending plume (Kerr et al., 1995).

Combining the above arguments, a simple model to con-sider for generating the ELIP is the derivation of a meltfrom a plume that consisted of recycled deep portion ofoceanic peridotitic lithosphere. Previous studies have sug-gested subduction of oceanic lithosphere underneath theYangtze Block during Neoproterzoic time (e.g., Zhouet al., 2006). It might be expected that the komatiites andpicrites with near-chondritic Os isotopic compositions were


derived from the recycled deep portion of oceanic litho-sphere. Moreover, the melts that produced the Lijiang pi-crites and Xinjie rocks have been termed ferropicritic,which are also enriched in LREEs, TiO2, Zr and manyother incompatible trace elements (Zhong et al., 2004;Zhang et al., 2006). These characteristics require the exis-tence of geochemically enriched domains as dikes or veinsin the depleted peridotite mantle (e.g., Niu and O’Hara,2003; Regelous et al., 2003). Thus, relatively small degreemelts from the heterogeneous mantle may contain a largerproportion of the more readily fusible component, whichcarries the enriched chemical and isotopic signatures forthe ferropicritic magmas. In contrast, the komatiites inthe ELIP could have been generated from a greater degreeof melting of incompatible trace element depleted, refrac-tory mantle components. However, even samples with con-siderable degree of ‘re-fertilization’ by metasomatic meltsdo not show correspondingly enriched Ti concentrations(Hellebrand et al., 2002). The TiO2 contents of most OIBare too high to be generated from any plausible peridotiticsources, which can be explained by the addition of smallamounts (generally less than 10%) of recycled mafic crust(Prytulak and Elliott, 2007). We therefore propose thatthe ferropicritic magmas in the ELIP were generated froma plume, possibly containing a substantial portion of recy-cled lithosphere. The plume-derived magmas thereafterinteracted with a relatively small amount of subducted/al-tered oceanic crust (probably


APPENDIX A. SUPPLEMENTARY DATA

Supplementary data associated with this article can befound, in the online version, at doi:10.1016/j.gca.2011.01.009.

REFERENCES

Ali J. R., Thompson G. M., Song X. Y. and Wang Y. (2002)Emeishan basalts (SW China) and the ‘end-Guadalupian’ crisis:magnetobiostratigraphic constraints. J. Geol. Soc. 159, 21–29.

Arndt N. T., Czamanske G., Walker R. J., Chauvel C. andFedorenko V. (2003) Geochemistry and origin of the intrusivehosts of the Noril’sk-Talnakh Cu–Ni–PGE sulfide deposits.Econ. Geol. 98, 495–515.

Arndt N. T., Lesher C. M. and Czamanske G. K. (2005) Mantle-derived magmas and magmatic Ni–Cu–(PGE) deposits. InEconomic Geology 100th Anniversary Volume (eds. J. W.Hedenquist, J. F. H. Thompson, R. J. Goldfarb and J. P.Richards). pp. 5–23.

Barnes S.-J. and Lightfoot P. C. (2005) Formation of magmaticnickel-sulfide ore deposits and processes affecting their copperand platinum-group element contents. In Economic Geology100th Anniversary Volume (eds. J. W. Hedenquist, J. F. H.Thompson, R. J. Goldfarb and J. P. Richards). pp. 179–213.7

Barnes S.-J. and Maier W. D. (1999) The fractionation of Ni, Cuand the noble metals in silicate and sulphide liquids. Geol.Assoc. Can. Short Course Notes 13, 69–106.

Barnes S.-J. and Maier W. D. (2002) Platinum-group elements andmicrostructures of normal Merensky Reef from Impala plati-num mines, Bushveld Complex. J. Petrol. 43, 103–128.

Barnes S.-J., Couture J.-F., Sawyer E. W. and Bouchaib C. (1993)Nickel–copper occurrences in the Belleterre–Angliers Belt of thePontiac Subprovince and the use of Cu–Pd ratios in interpretingplatinum-group element distributions. Econ. Geol. 88, 1402–1418.

Barnes S.-J., Zientek M. L. and Severson M. J. (1997) Ni, Cu, Auand platinum-group element contents of sulphides associatedwith intraplate magmatism: a synthesis. Can. J. Earth Sci. 34,337–351.

Bennett V. C., Nutman A. P. and Esat T. M. (2002) Constraints onmantle evolution from 187Os/188Os isotopic compositions ofArchean ultramfic rocks from southern West Greenland(3.8 Ga) and Western Australia (3.46 Ga). Geochim. Cosmo-chim. Acta 66, 2615–2630.

Birck J. L., Roy-Barman M. and Capmas F. (1997) Re–Os isotopicmeasurements at the femtomole level in natural samples.Geostand. Newslett. 20, 19–27.

Brandon A. D., Norman M. D., Walker R. J. and Morgan J. W.(1999) 186Os–187Os systematics of Hawaiian picrites. EarthPlanet. Sci. Lett. 174, 25–42.

Brandon A. D., Walker R. J., Puchtel I. S., Becker H., HumayunM. and Revillon S. (2003) 186Os–187Os systematics of GorgonaIsland komatiites: implications for early growth of the innercore. Earth Planet. Sci. Lett. 206, 411–426.

Brügmann G. E., Hanski E. J., Naldrett A. J. and Smolkin V. F.(2000) Sulphide segregation in ferropicrites from the PechengaComplex, Kola Peninsula. Russia J. Petrol. 41, 1721–1742.

Campbell I. H. and Naldrett A. J. (1979) The influence ofsilicate:sulfide ratios on the geochemistry of magmatic sulfides.Econ. Geol. 74, 1503–1506.

Campbell I. H., Naldrett A. J. and Barnes S. J. (1983) A model forthe origin of the platinum-rich sulfide horizons in the Bushveldand Stillwater complexes. J. Petrol. 24, 133–165.

Capobianco C. J. and Drake M. J. (1990) Partitioning ofruthenium, rhodium, and palladium between spinel and silicatemelt and implications for platinum group element fractionationtrends. Geochim. Cosmochim. Acta 54, 869–874.

Chai G. and Naldrett A. J. (1992) The Jinchuan ultramaficintrusion: cumulate of a high-Mg basaltic magma. J. Petrol. 33,277–303.

Chazey W. J. and Neal C. R. (2005) Platinum-group elementconstraints on source composition and magma evolution of theKerguelen Plateau using basalts from ODP Leg 183. Geochim.Cosmochim. Acta 69, 4685–4701.

Chu Z. Y., Wu F. Y., Walker R. J., Rudnick R. L., Pitcher L.,Puchtel I. S., Yang Y. H. and Wilde S. A. (2009) Temporalevolution of lithospheric mantle beneath the eastern NorthChina Craton. J. Petrol. 50, 1857–1898.

Chung S. L. and Jahn B. M. (1995) Plume–lithosphere interactionin generation of the Emeishan flood basalts at the Permian–Triassic boundary. Geology 23, 889–892.

Cohen A. S. and Waters F. G. (1996) Separation of osmium fromgeological materials by solvent extraction for analysis by TIMS.Anal. Chim. Acta 332, 269–275.

Dale C. W., Gannoun A., Burton K. W., Argles T. W. andParkinson I. J. (2007) Rhenium–osmium isotope and elementalbehaviour during subduction of oceanic crust and the implica-tions for mantle recycling. Earth Planet. Sci. Lett. 253, 211–225.

Dale C. W., Pearson D. G., Starkey N. A., Stuart F. M., Ellam R.M., Larsen L. M., Fitton J. G. and Macpherson C. G. (2009)Osmium isotopes in Baffin Island and West Greenland picrites:implications for the 187Os/188Os composition of the convectingmantle and the nature of high 3He/4He mantle. Earth Planet.Sci. Lett. 278, 267–277.

Day J. M. D., Pearson D. G. and Hulbert L. J. (2008) Rhenium–osmium isotope and platinum-group element constraints on theorigin and evolution of the 1.27 Ga Muskox layered intrusion.J. Petrol. 49, 1255–1295.

Eales H. V. and Cawthorn R. G. (1996) The Bushveld Complex. InLayered Intrusions (ed. R. G. Cawthorn). Elsevier, Amsterdam,pp. 181–230.

Ernst R. E., Buchan K. L. and Campbell I. H. (2005) Frontiers inlarge igneous province research. Lithos 79, 271–297.

Evans-Lamswood D. M., Butt D. P., Jackson R. S., Lee D. V.,Muggridge M. G. and Wheeler R. I. (2000) Physical controlsassociated with the distribution of sulfides in the Voisey’s BayNi–Cu–Co deposits, Labrador. Econ. Geol. 95, 749–769.

Fleet M. E., Crocket J. H., Liu M. and Stone W. E. (1999)Laboratory partitioning of platinum-group elements (PGE) andgold with application to magmatic-PGE deposits. Lithos 47,127–142.

Foster J. G., Lambert D. D., Frick L. R. and Maas R. (1996) Re–Os isotopic evidence for genesis of Archean nickel ores fromuncontaminated komatiites. Nature 382, 703–706.

Francis R. D. (1990) Sulfide globules in mid-ocean ridge basalts(MORB), and the effect of oxygen abundance in Fe–S–O liquidson the ability of those liquids to partition metals from MORBand komatiite magmas. Chem. Geol. 85, 199–213.

Gangopadhyay A. and Walker R. J. (2003) Re–Os systematics ofthe ca. 2.7-Ga komatiites from Alexo, Ontario, Canada. Chem.Geol. 196, 147–162.

Ghiorso M. S. and Sack R. O. (1995) Chemical mass transfer inmagmatic processes. IV. A revised and internally consistentthermodynamic model for the interpolation and extrapolationof liquid–solid equilibria in magmatic systems at elevatedtemperatures and pressures. Contrib. Mineral. Petrol. 119, 197–212.

Guo F., Fan W. M., Wang Y. J. and Li C. W. (2004) When did theEmeishan mantle plume activity start? Geochronological and

http://dx.doi.org/10.1016/j.gca.2011.01.009http://dx.doi.org/10.1016/j.gca.2011.01.009


geochemical evidence from ultrmafic–mafic dikes in southwest-ern China. Int. Geol. Rev. 46, 226–234.

Hannah J. L. and Stein H. J. (2002) Re–Os model for the origin ofsulfide deposits in anorthosite-associated intrusive complexes.Econ. Geol. 97, 371–383.

Hanski E., Huhma H., Rastas P. and Kamenetsky V. S. (2001) ThePalaeoproterozoic komatiite-picrite association of FinnishLapland. J. Petrol. 42, 855–876.

Hanski E., Walker R. J., Huhma H., Polyakov G. V., Balykin P.A., Hoa T. T. and Phuong N. T. (2004) Origin of the Permian–Triassic komatiites, northwestern Vietnam. Contrib. Mineral.Petrol. 147, 453–469.

Haughton D. R., Roedder P. L. and Skinner B. J. (1974) Solubilityof sulfur in mafic magmas. Econ. Geol. 69, 451–467.

He B., Xu Y. G., Chung S. L., Xiao L. and Wang Y. (2003)Sedimentary evidence for a rapid crustal doming prior to theeruption of the Emeishan flood basalts. Earth Planet. Sci. Lett.213, 389–405.

He B., Xu Y. G., Huang X. L., Luo Z. Y., Shi Y. R., Yang Q. J.and Yu S. Y. (2007) Age and duration of the Emeishan floodvolcanism, SW China: geochemistry and SHRIMP zircon U–Pbdating of silicic ignimbrites, post-volcanic Xuanwei Formationand clay tuff at the Chaotian section. Earth Planet. Sci. Lett.255, 306–323.

Hellebrand E., Snow J. E., Hoppe P. and Hofmann A. W. (2002)Garnet-field melting and late-stage refertilization in ‘residual’abyssal peridotites from the central Indian ridge. J. Petrol. 43,2305–2338.

Herzberg C. and O’Hara M. J. (1998) Phase equilibrium con-straints on the origin of basalts, picrites, and komatiites. EarthSci. Rev. 44, 39–79.

Horan M. F., Walker R. J., Fedorenko V. A. and Czamanske G.K. (1995) Os and Nd isotopic constraints on the temporal andspatial evolution of Siberian flood basalt sources. Geochim.Cosmochim. Acta 59, 5159–5168.

Horan M. F., Morgan J. W., Walker R. J. and Cooper R. W.(2001) Re–Os isotopic constraints on magma mixing in theperidotite zone of the Stillwater complex, Montana, USA.Contrib. Mineral. Petrol. 141, 446–457.

Huang K. N. and Opdyke N. D. (1998) Magnetostratigraphicinvestigations on an Emeishan basalt section in westernGuizhou province, China. Earth Planet. Sci. Lett. 163,1–14.

Irvine T. N. (1977) Origin of chromitite layers in the Muskoxintrusion and other stratiform intrusions: a new interpretation.Geology 5, 273–277.

Keays R. R. (1995) The role of komatiitic and picritic magmatismand S-saturation in the formation of the ore deposits. Lithos 34,1–18.

Kerr A. and Leitch A. M. (2005) Self-destructive sulfide segrega-tion systems and the formation of high-grade magmatic oredeposits. Econ. Geol. 100, 311–332.

Kerr A. C., Saunders A. D., Tarney J., Berry N. H. and Hards V.L. (1995) Depleted mantle-plume geochemical signatures: noparadox for plume theories. Geology 23, 843–846.

Lambert D. D., Frick L. R., Foster J. G., Li C. S. and Naldrett A.J. (2000) Re–Os isotope systematics of the Voisey’s Bay Ni–Cu–Co magmatic sulfide system, Labrador, Canada: II. Implica-tions for parental magma chemistry, ore genesis, and metalredistribution. Econ. Geol. 95, 867–888.

Lassiter J. C. and Hauri E. H. (1998) Osmium-isotope variations inHawaiian lavas: evidence for recycled oceanic lithosphere in theHawaiian plume. Earth Planet. Sci. Lett. 164, 483–496.

Li C. and Naldrett A. J. (1999) Geology and petrology of theVoisey’s Bay intrusion: reaction of olivine with sulfide andsilicate liquids. Lithos 47, 1–31.

Li C., Lightfoot P. C., Amelin Y. and Naldrett A. J. (2000)Contrasting petrological and geochemical relationships in theVoisey’s Bay and Mushuau intrusions, Labrador, Canada:implications for ore genesis. Econ. Geol. 95, 771–799.

Li Z. X., Li X. H., Kinny P. D., Wang J., Zhang S. and Zhou H.(2003) Geochronology of Neoproterozoic syn-rift magmatismin the Yangtze Craton, South China and correlations with othercontinents: evidence for a mantle superplume that broke upRodinia. Precamb. Res. 122, 85–109.

Li X. H., Li Z. X., Sinclair J. A., Li W. X. and Carter G. (2006)Revisiting the “Yanbian Terrane”: implications for Neoprote-rozoic tectonic evolution of the western Yangtze Block, SouthChina. Precamb. Res. 151, 14–30.

Li C., Ripley E. M. and Naldrett A. J. (2009) A new genetic modelfor the giant Ni–Cu–PGE sulfide deposits associated with theSiberian flood basalts. Econ. Geol. 104, 291–301.

Ludwig K. R. (2003) Isoplot 3.00 User’s Manual: A Geochrono-logical Toolkit for Microsoft Excel, Berkley GeochronologicalCenter, Special Publication No. 4, Rev. May 30, 70p.

Luo Y. N. (1981) The characteristics of Ti-chromite mineralizationin Xinjie layered ultramafic–mafic intrusion in Panzhihua area,China. Geochimica 10(1), 66–74 (in Chinese).

Maier W. D. and Barnes S.-J. (1999) Platinum-group elements insilicate rocks of the Lower, Critical and Main Zones at Unionsection, western Bushveld Complex. J. Petrol. 40, 1647–1671.

Mao Y. S. and Sun S. H. (1981) Petrological characteristics andorigin of layered basic–ultrabasic intrusion in Xinjie, Miyi,Sichuan Province. Mineral Rocks (6), 29–40 (in Chinese withEnglish abstract).

McCandless T. E., Ruiz J., Adair B. I. and Freydier C. (1999) Re–Os isotope and Pd/Ru variations in chromitites from theCritical Zone, Bushveld Complex, South Africa. Geochim.Cosmochim. Acta 63, 911–923.

Meisel T. and Moser J. (2004) Reference materials for geochemicalPGE analysis: new analytical data for Ru, Rh, Pd, Os, Ir, Ptand Re by isotope dilution ICP-MS in 11 geological referencematerials. Chem. Geol. 208, 319–338.

Meisel T., Moser J. and Wegscheider W. (2001) Recognizingheterogeneous distribution of platinum group elements (PGE)in geological materials by means of the Re–Os isotope system.Fresen. J. Anal. Chem. 370, 566–572.

Morgan J. W., Stein H. J., Hannah J. L., Markey R. J. andWiszniewska J. (2000) Re–Os study of Fe–Ti–V oxide and Fe–Cu–Ni sulfide deposits, Suwalki anorthosite massif, northeastPoland. Miner. Deposita 35, 391–401.

Naldrett A. J. (2010) Secular variation of magmatic sulfide depositsand their source magmas. Econ. Geol. 105, 669–688.

Naldrett A. J. and Lehmann J. (1988) Spinel non-stoichiometry asthe explanation for Ni-, Cu-, and PGE-enriched sulphides inchromitites. In Geo-platinum 87 (eds. H. M. Prichard, P. J.Potts, J. F. W. Bowles and S. J. Cribb). Elsevier, pp, pp. 93–110.

Naldrett A. J., Gasparini E. C., Barnes S. J., von Gruenewaldt G.and Sharpe M. R. (1986) The upper critical zone of theBushveld Complex and the origin of Merensky-type ores. Econ.Geol. 81, 1105–1117.

Naldrett A. J., Wilson A. H., Kinnaird J. and Chunnett G. (2009)PGE tenor and metal ratios within and below the MerenskyReef, Bushveld Complex: implications for its genesis. J. Petrol.50, 625–659.

Niu Y. and O’Hara M. J. (2003) Origin of ocean island basalts: anew perspective from petrology, geochemistry, and mineralphysics considerations. J. Geophys. Res. 108, 2209. doi:10.1029/2002JB002048.

O’Driscoll B., Day J. M. D., Daly J. S., Walker R. J. andMcDonough W. F. (2009) Rhenium–osmium isotopes and

http://dx.doi.org/10.1029/2002JB002048http://dx.doi.org/10.1029/2002JB002048


platinum-group elements in the Rum Layered Suite, Scotland:implications for Cr-spinel seam formation and the compositionof the Iceland mantle anomaly. Earth Planet. Sci. Lett. 286, 41–51.

Pang K. N., Zhou M. F., Lindsley D., Zhao D. G. and Malpas J.(2008) Origin of Fe–Ti oxide ores in mafic intrusion: evidencefrom the Panzhihua intrusion, SW China. J. Petrol. 49, 295–313.

Peach C. L., Mathez E. A., Keays R. R. and Reeves S. J. (1994)Experimentally determined sulfide–silicate melt partition coef-ficients for iridium and palladium. Chem. Geol. 117, 361–377.

Philipp H., Eckhardt J. D. and Puchelt H. (2001) Platinum-groupelements (PGE) in basalts of the seaward-dipping reflectorsequence, SE Greenland coast. J. Petrol. 42, 407–432.

Prytulak J. and Elliott T. (2007) TiO2 enrichment in ocean islandbasalts. Earth Planet. Sci. Lett. 263, 388–403.

Puchtel I. S. and Humayun M. (2001) Platinum group elementfractionation in a komatiitic basalt lava lake. Geochim.Cosmochim. Acta 65, 2979–2993.

Puchtel I. S., Brügmann G. E. and Hofmann A. W. (2001a) 187Os-enriched domain in an Archean mantle plume: evidence from2.8 Ga komatiites of the Kostomuksha greenstone belt, NWBaltic Shield. Earth Planet. Sci. Lett. 186, 513–526.

Puchtel I. S., Brügmann G. E., Hofmann A. W., Kulikov V. S. andKulikova V. V. (2001b) Os isotopic systematics of komatiiticbasalts from the Vetreny belt, Baltic Shield: evidence for achondritic source of the 2.45 Ga plume. Contrib. Mineral.Petrol. 140, 588–599.

Puchtel I. S., Brandon A. D. and Humayun M. (2004) Precise Pt–Re–Os isotope systematics of the mantle from 2.7-Ga komat-iites. Earth Planet. Sci. Lett. 224, 157–174.

Qi L., Hu J. and Grégoire D. C. (2000) Determination of traceelements in granites by inductively coupled plasma massspectrometry. Talanta 51, 507–513.

Qi L., Zhou M. F. and Wang C. Y. (2004) Determination of lowconcentrations of platinum group elements in geologicalsamples by ID-ICP-MS. J. Anal. At. Spetrom. 19, 1335–1339.

Qi L., Zhou M. F., Wang C. Y. and Sun M. (2007) Evaluation ofthe determination of Re and PGEs abundances of geologicalsamples by ICP-MS coupled with a modified Carius tubedigestion at different temperatures. Geochem. J. 41, 407–414.

Qi L., Wang C. Y. and Zhou M. F. (2008) Controls on the PGEdistribution of Permian Emeishan alkaline and peralkalinevolcanic rocks in Longzhoushan, Sichuan Province, SW China.Lithos 106, 222–236.

Regelous M., Hofmann A. W., Abouchami W. and Galer S. J. G.(2003) Geochemistry of lavas from the Emperor Seamounts,and the geochemical evolution of Hawaiian magmatism from85 to 42 Ma. J. Petrol. 44, 113–140.

Righter K. and Downs R. T. (2001) The crystal structures ofsynthetic Re- and PGE-bearing magnesioferrite spinels: impli-cations for impacts, accretion and the mantle. Geophys. Res.Lett. 28, 619–622.

Roeder P. and Emslie R. F. (1970) Olivine-liquid equilibrium.Contrib. Mineral. Petrol. 29, 275–282.

Rogers N. W., Davies M. K., Parkinson I. J. and Yirgu G. (2010)Osmium isotopes and Fe/Mn ratios in Ti-rich picritic basaltsfrom the Ethiopian flood basalt province. No evidence fromcore contribution to the Afar plume. Earth Planet. Sci. Lett.296, 413–422.

SBGMR (Sichuan Bureau of Geology and Mineral Resources)(1991) Regional Geology of Sichuan province. Geological Pub-lishing House, Beijing. 680pp (in Chinese).

Schaefer B. F., Parkinson I. J. and Hawkesworth C. J. (2000) Deepmantle plume osmium isotope signature from West GreenlandTertiary picrites. Earth Planet. Sci. Lett. 175, 105–118.

Shirey S. B. (1997) Re–Os compositions of mid-continent riftsystem picrites: implications for plume–lithosphere interactionand enriched mantle sources. Can. J. Earth Sci. 34, 489–503.

Shirey S. B. and Walker R. J. (1995) Carius tube digestions for low-blank rhenium–osmium analysis. Anal. Chem. 67, 2136–2141.

Song X. Y., Zhou M. F., Cao Z. M., Sun M. and Wang Y. L.(2003) Ni–Cu–(PGE) magmatic sulfide deposits in the Yan-gliuping area, Permian Emeishan igneous province, SW China.Miner. Deposita 38, 831–843.

Tao Y., Li C., Hu R. Z., Ripley E. M., Du A. D. and Zhong H.(2007) Petrogenesis of the Pt–Pd mineralized Jinbaoshanultramafic intrusion in the Permian Emeishan large igneousprovince, SW China. Contrib. Mineral. Petrol. 153, 321–337.

Tao Y., Li C., Song X. Y. and Ripley E. M. (2008) Mineralogical,petrological and geochemical studies of the Limahe mafic–ultramafic intrusion and associated Ni–Cu sulfide ores, SWChina. Miner. Deposita 43, 849–872.

Tao Y., Li C., Hu R. Z., Qi L., Qu W. J. and Du A. D. (2010) Re–Os isotopic constraints on the genesis of the Limahe Ni–Cudeposit in the Emeishan large igneous province, SW China.Lithos 119, 137–146.

Thériault R. D., Barnes S.-J. and Severson M. J. (2000) Origin of Cu–Ni–PGE sulfide mineralization in the Partridge River intrusion,Duluth Complex, Minnesota. Econ. Geol. 95, 929–943.

Vogel D. C., Keays R. R., James R. S. and Reeves S. J. (1999) Thegeochemistry and petrogenesis of the Agnew intrusion, Canada:a product of S-undersaturated, high-Al and low-Ti tholeiiticmagmas. J. Petrol. 40, 423–450.

Walker R. J. and Nisbet E. (2002) 187Os isotopic constraints onArchean mantle dynamics. Geochim. Cosmochim. Acta 66,3317–3325.

Walker R. J. and Stone W. R. (2001) Os isotope constraints on theorigin of the 2.7 Ga Boston Creek flow, Ontario, Canada.Chem. Geol. 175, 567–579.

Walker R. J., Morgan J. W., Horan M. F., Czamanske G. K.,Krogstad E. J., Fedorenko V. A. and Kunilov V. E. (1994) Re–Os isotopic evidence for an enriched-mantle source for theNoril’sk-type, ore-bearing intrusions, Siberia. Geochim. Cos-mochim. Acta 58, 4179–4197.

Walker R. J., Morgan J. W. and Horan M. F. (1995) 187Osenrichment in some mantle plume sources: evidence for core–mantle interaction? Science 269, 819–822.

Walker R. J., Morgan J. W., Hanski E. J. and Smolkin V. (1997)Re–Os systematics of Early Proterozoic ferropicrites, PechengaComplex, NW Russia: evidence for ancient 187Os-enrichedplumes. Geochim. Cosmochim. Acta 61, 3145–3160.

Walker R. J., Storey M., Kerr A., Tarney J. and Arndt N. T. (1999)Implications of 187Os heterogeneities in mantle plumes: evi-dence from Gorgona Island and Curacao. Geochim. Cosmo-chim. Acta 63, 713–728.

Walker R. J., Prichard H. M., Ishiwatari A. and Pimentel M.(2002) The osmium isotopic compositions of the convectingupper mantle deduced from ophiolite chromitites. Geochim.Cosmochim. Acta 66, 329–345.

Wang C. Y., Zhou M. F. and Zhao D. G. (2005) Mineral chemistryof chromite from the Permian Jinbaoshan Pt–Pd–sulphide-bearing ultramafic intrusion in SW China with petrogeneticimplications. Lithos 83, 47–66.

Wang C. Y., Zhou M. F. and Keays R. R. (2006) Geochemicalconstraints on the origin of the Permian Baimazhai mafic–ultramafic intrusion, SW China. Contrib. Mineral. Petrol. 152,309–321.

Wang C. Y., Zhou M. F. and Zhao D. G. (2008) Fe–Ti–Cr oxidesfrom the Permian Xinjie mafic–ultramafic layered intrusion inthe Emeishan large igneous province, SW China: crystallizationfrom Fe- and Ti-rich basalt magmas. Lithos 102, 198–217.


Xiao L., Xu Y. G., Mei H. J., Zheng Y. F., He B. and Pirajno F.(2004) Distinct mantle sources of low-Ti and high-Ti basaltsfrom the western Emeishan large igneous province, SW China:implications for plume–lithosphere interaction. Earth Planet.Sci. Lett. 228, 525–546.

Xu Y. G., Chung S. L., Jahn B. M. and Wu G. Y. (2001) Petrologicand geochemical constraints on the petrogenesis of Permian–Triassic Emeishan flood basalts in southwestern China. Lithos58, 145–168.

Xu Y. G., He B., Chung S. L., Menzies M. A. and Frey F. A.(2004) Geologic, geochemical, and geophysical consequences ofplume involvement in the Emeishan flood-basalt province.Geology 32, 917–920.

Xu J. F., Suzuki K., Xu Y. G., Mei H. J. and Li J. (2007) Os, Pb,and Nd isotope geochemistry of the Permian Emeishancontinental flood basalts: insights into the source of a largeigneous province. Geochim. Cosmochim. Acta 71, 2104–2119.

Yao P. H., Wang K. N., Du C. L., Lin Z. T. and Song X. (1993)Records of China’s Iron Ore Deposits. Metallurgic IndustryPress, Beijing. pp. 633–649 (in Chinese with English abstract).

Zhang Z. C., Mao J. W., Mahoney J. J., Wang F. S. and Qu W. J.(2005) Platinum group elements in the Emeishan large province,SW China: implications for mantle source. Geochem. J. 39, 371–382.

Zhang Z. C., Mahoney J. J., Mao J. W. and Wang F. S. (2006)Geochemistry of picritic and associated flows of the westernEmeishan flood basalt province, China. J. Petrol. 47, 1997–2019.

Zhang Z. C., Zhi X. C., Chen L., Saunders A. D. and Reichow M.K. (2008) Re–Os isotopic compositions of picrites from theEmeishan flood basalt province, China. Earth Planet. Sci. Lett.276, 30–39.

Zhang Z. C., Mao J. W., Saunders A. D., Ai Y., Li Y. and Zhao L.(2009) Petrogenetic modeling of three mafic–ultramafic layeredintrusion in the Emeishan large igneous province, SW China,based on isotopic and bulk chemical constraints. Lithos 113,369–392.

Zhong H. and Zhu W. G. (2006) Geochronology of layered maficintrusions from the Pan-Xi area in the Emeishan large igneousprovince, SW China. Miner. Deposita 41, 599–606.

Zhong H., Zhou X. H., Zhou M. F., Sun M. and Liu B. G. (2002)Platinum-group element geochemistry of the Hongge Fe–V–Tideposit in the Pan-Xi area, southwestern China. Miner.Deposita 37, 226–239.

Zhong H., Yao Y., Hu S. F., Zhou X. H., Liu B. G., Sun M., ZhouM. F. and Viljoen M. J. (2003) Trace-element and Sr–Nd

isotopic geochemistry of the PGE-bearing Hongge layeredintrusion, southwestern China. Int. Geol. Rev. 45, 371–382.

Zhong H., Yao Y., Prevec S. A., Wilson A. H., Viljoen M. J.,Viljoen R. P., Liu B. G. and Luo Y. N. (2004) Trace-elementand Sr–Nd isotopic geochemistry of the PGE-bearing Xinjielayered intrusion in SW China. Chem. Geol. 203, 237–252.

Zhong H., Hu R. Z., Wilson A. H. and Zhu W. G. (2005) Reviewof the link between the Hongge layered intrusion and Emeishanflood basalts, southwest China. Int. Geol. Rev. 47, 971–985.

Zhong H., Zhu W. G., Qi L., Zhou M. F., Song X. Y. and ZhangY. (2006) Platinum-group element (PGE) geochemistry of theEmeishan basalts in the Pan-Xi area, SW China. Chin. Sci. Bull.51, 845–854.

Zhou C. L. (1982) Petrological characteristics and genesis of theXinjie basic/ultrabasic layered intrusion in Miyi. J. ChengduColleg. Geol. (2), 5–12 (in Chinese).

Zhou M. F., Malpas J., Song X. Y., Robinson P. T., Sun M.,Kennedy A. K., Lesher C. M. and Keays R. R. (2002) Atemporal link between the Emeishan large igneous province(SW China) and the end-Guadalupian mass extinction. EarthPlanet. Sci. Lett. 196, 113–122.

Zhou M. F., Robinson P. T., Lesher C. M., Keays R. R., Zhang C.J. and Malpas J. (2005) Geochemistry, petrogenesis andmetallogenesis of the Panzhihua gabbroic layered intrusionand associated Fe–Ti–V oxide deposits, Sichuan province, SWChina. J. Petrol. 46, 2253–2280.

Zhou M. F., Ma Y. X., Yan D. P., Xia X. P., Zhao J. H. and SunM. (2006) The Yanbian terrane (southern Sichuan Province,SW China): a Neoproterozoic arc assemblage in the westernmargin of the Yangtze Block. Precamb. Res. 144, 19–38.

Zhou M. F., Arndt N. T., Malpas J., Wang C. Y. and Kennedy A.K. (2008) Two magma series and associated ore deposit types inthe Permian Emeishan large igneous province, SW China.Lithos 103, 352–368.

Zhu W. G., Zhong H., Hu R. Z., Liu B. G., He D. F., Song X. Y.and Deng H. L. (2010) Platinum-group minerals and telluridesfrom the PGE-bearing Xinjie layered intrusion in the EmeishanLarge Igneous Province, SW China. Miner. Petrol. 98, 167–180.

Associate editor: Edward M. Ripley

Rhenium–osmium isotope and platinum-group elements in the Xinjie layered intrusion, SW China: Implications for source mantle composition, mantle evolution, PGE fractionation and mineralizationIntroductionGeological backgroundPetrography of the Xinjie intrusionAnalytical methodsResultsVariations in major and trace elementsVariations in chalcophile elements and PGERe–Os isotope

DiscussionEstimation of a Xinjie parental melt compositionPGE behavior during the evolution of the Xinjie magmaModeling of the role of cumulus sulfidesPetrogenesis of the PGE-rich sulfidesThe Xinjie and ELIP mantle source in a global context

ConclusionsAcknowledgmentsSupplementary dataReferences

rheniumâ€“osmium isotope and platinum-group elements in the …courses/c590/2017/zhong...

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