Download - Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals
![Page 1: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/1.jpg)
Short Course: U-Pb Geochronology
and Hf Isotope Geochemistry Applied to Detrital Minerals
Funding from NSF (Instrumentation & Facilities)
Help from Thermo Instruments, GV Instruments, Nu Plasma Instruments, New Wave Research & Photon Machines
George GehrelsDepartment of Geosciences
University of ArizonaTucson, AZ 85721
Jeff VervoortSchool of Earth & Environmental Sciences
Washington State UniversityPullman, WA 99164
![Page 2: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/2.jpg)
Outline 1. Basics of U-Th-Pb decay system2. Measurement methods3. Mineral systems & applications4. Complexities for zircon5. Detrital geochronology (plots & analyses) 6. Future opportunities7. Basics of Lu-Hf decay system8. Measurement challenges9. Application to detrital minerals
![Page 3: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/3.jpg)
U-Th-Pb chronometers:
0.0
0.2
0.4
0.6
0.8
1.0
1.2
0 1 2 3 4Age (Ga)
206*
/238
0
10
20
30
40
50
60
70
80
90
0 1 2 3 4Age (Ga)
207*
/235
0.0
0.1
0.1
0.2
0.2
0.3
0.3
0 1 2 3 4Age (Ga)
208*
/232
0.0
5.0
10.0
15.0
20.0
25.0
0 1 2 3 4Age (Ga)
206*
/207
*
Any mineral with U and/or Th is a potential chronometer!
Best if little Pb included during crystallization
Need to know conditions of retention of Pb to understand age
206Pb/238U 207Pb/235U 206Pb/207Pb 208Pb/232Th
![Page 4: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/4.jpg)
Geochronometers &Thermochronometers
Geochronometer:Mineral grows below blocking temp Age records crystallization
Thermochronometer:Mineral grows above blocking temp Age records cooling
![Page 5: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/5.jpg)
Common: Less common:Garnet MonaziteRutile MagnetiteTourmaline IlmeniteZircon Chromite
OlivineDiamond
Heavy minerals in sand:
![Page 6: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/6.jpg)
Why zircon is king….
ZrSiO4
High U concentration (100-1000 ppm) Moderate Th concentration (10-100 ppm) Zr, U, Th tightly held [similar in size (0.8-1.0 Å)
and charge (+4)] Low common Pb during crystallization (ppt) Grows @ 600-1100 ºC, retains Pb to >800°C Common in felsic & intermediate igneous rocks Chemically and mechanically resistant.
![Page 7: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/7.jpg)
Zircon (ZrSiO4)• Birthstone for December• Protects travelers from harm• Increases one's appetite• Induces deep sleep (no nightmares)• Helps one be at peace• Loss of luster warns of danger• Provides wisdom, honor, and riches• Heals mental disturbances• Feeding the zircon gorilla = team building activity!
Brown: heals headachesColorless: clears the auraYellow: attracts loveRed: heals injuries, soothes painsGreen: draws wealthLight blue: stabilizes mind & emotionsPink: assists in astral travel at nightViolet: money magnet
Zircon should be placed in dry sea salt once a month for discharge and recharge…
![Page 8: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/8.jpg)
Zircon: Provenance of modern sediment
![Page 9: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/9.jpg)
Zircon: Provenance of ancient sediment…
![Page 10: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/10.jpg)
Zircon: Provenance of artifacts…
Mano Temper sands
![Page 11: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/11.jpg)
Zircon: Age of Sediment Accumulation
Detrital grains =
Maximum depositional age
Dating volcanic layers
![Page 12: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/12.jpg)
Zircon: Growth history & Thermal history
“Multi-Dating”
![Page 13: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/13.jpg)
Rutile (TiO2)... Low-mod U content (~10-100 ppm) Moderate common Pb (<10% of total Pb),
206/204 < 1,000 Blocking temp = ~380–450 °C Resists mechanical and chemical weathering
Strength with love
Ease transitions Calm, reason,
order Stabilizes
relationships Off-planet
connector
![Page 14: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/14.jpg)
Low-mod U content (~10-100 ppm) Moderate common Pb (<10% of total Pb) Blocking temp = 400-500 °C Multi-dating
Apatite Ca5(PO4)3
Appetite suppression
Discern truth within
Enhances creativity
Unconditional acceptance
Vibrates to the number 9
![Page 15: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/15.jpg)
Very high Th content (1000-10,000 ppm) Moderate U content (100-1000 ppm) Very low common Pb (ppt) Blocking temperature = ~680–750 °C Can tie age to metamorphic reactions mod- to high-grade metamorphism Multi-dating?
Monazite CeLaThPO4
??
![Page 16: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/16.jpg)
Monazite CeLaThPO4
From: Hietpas et al. (2010)
zircon
monazite
![Page 17: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/17.jpg)
Occurs as inclusions in other minerals (e.g., garnet) many potential applications!
Monazite CeLaThPO4
From: http://webhost.bridgew.edu/mkrol/Research-2.html
![Page 18: Short Course: U-Pb Geochronology and Hf Isotope Geochemistry Applied to Detrital Minerals](https://reader036.vdocuments.us/reader036/viewer/2022081420/56815d83550346895dcb9169/html5/thumbnails/18.jpg)
Xenotime YPO4
From: McNaughton et al. (1999)
Moderate U & Th contents (~100 ppm) Moderate to low common Pb (ppt) Blocking temperature = 600-700 °C (?) Peraluminous igneous rocks Diagenetic overgrowths on zircon
depositional ages??