Thermobarometry of metapelites in the Coast shear zone at Mussel Inlet

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Thermobarometry of metapelites in the Coast shear
zone at Mussel Inlet

• Dave Pearson

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2-7.5 kbar, 325C
8.2 kbar, 620-710C
8.21 kbar, 515-650C
8.5-11.3 kbar, 570-700C
6.4 kbar, 600-705C
61 kbar, 60050C

• Mostly GASP barometry, garnet-biotite thermometry
• Ages generally inferred from U-Pb pluton ages

6.31 kbar, 68550C

• Previous P-T-t work
• Generally 3 metamorphic episodes recognized
  gt101 Ma, 90-80 Ma, and 75-60 Ma

61 kbar
4-4.5 kbar
6.3 kbar
10.2 kbar
5.60.4 kbar, 71030C
8.1 1 kbar, 600C
6.4 kbar, 525 ºC
90-60 Ma
5.60.5 kbar, 56020C
7.41.5 kbar, 75050 ºC
70-60 Ma
5.41.5 kbar, 72630 ºC
90 Ma
6.30.8 kbar, 68030 ºC
gt101 Ma
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2-7.5 kbar, 325C
8.2 kbar, 620-710C
8.21 kbar, 515-650C
8.5-11.3 kbar, 570-700C
6.4 kbar, 600-705C
61 kbar, 60050C

• Rusmore et al. (2005) show continuous
  metamorphism from 90-60 Ma in Central Gneiss near
  Douglas Channel

6.31 kbar, 68550C
61 kbar

• Previous P-T-t work (cont.)
• West of CSZ, pressures generally increase toward
  the east

4-4.5 kbar
6.3 kbar
10.2 kbar
5.60.4 kbar, 71030C
8.1 1 kbar, 600C
6.4 kbar, 525 ºC
90-60 Ma
5.60.5 kbar, 56020C
7.41.5 kbar, 75050 ºC
70-60 Ma
5.41.5 kbar, 72630 ºC
90 Ma
6.30.8 kbar, 68030 ºC
gt101 Ma
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My preliminary results from Mussell Inlet

• So far, 2 samples from Mussell Inlet GJP-48
  and GJP-49
• These samples consist of Qtzbtplagsillksparm
  s
• More P-Ts to come
• I will also do Sm-Nd garnet-whole rock dating of
  these and more samples

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5.60.4 kbar, 71030C
My preliminary results
6.4 kbar, 525 ºC
8.1 1 kbar, 600C

• In Mussell Inlet, probably within CSZ
• Sillimanite-bearing metapelites (Yukon-Tanana
  protolith), with relict kyanite in some samples
• For barometry (GASP), used Holland and Powell
  (1995) data set calibrations
• For thermometry (grt-bt), took average of 7
  different calibrations

5.41.5 kbar, 72630 ºC
5.60.5 kbar, 56020C
7.41.5 kbar, 75050 ºC
6.30.8 kbar, 68030 ºC
GJP-49 5.030.29 kbar, 66030oC
GJP-48 4.730.24 kbar, 64010oC
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5.60.4 kbar, 71030C
2-7.5 kbar, 325C
8.2 kbar, 620-710C
8.21 kbar, 515-650C
6.4 kbar, 600-705C
8.5-11.3 kbar, 570-700C
61 kbar, 60050C
61 kbar
4-4.5 kbar
6.3 kbar
10.2 kbar
8.1 1 kbar, 600C
6.4 kbar, 525 ºC
90-60 Ma
5.60.5 kbar, 56020C
7.41.5 kbar, 75050 ºC
70-60 Ma
5.41.5 kbar, 72630 ºC
90 Ma
6.30.8 kbar, 68030 ºC
GJP-49 5.030.29 kbar, 66030oC
gt101 Ma
GJP-48 4.730.24 kbar, 64010oC
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P-T-t references

• Crawford et al., 1979, Crawford et al., 1987,
  Stowell, 1989, Himmelberg et al., 1991, 1994,
  Himmelberg et al., 1995, Taylor et al., 1996,
  1997 Stowell and Goldberg, 1997, Klepeis et al.,
  1998, Lindline, 1999, Stowell and Crawford, 2000,
  Stowell et al., 2001, Rusmore et al., 2005