30 years of P-T-t paths:What we’ve learned about

orogenesis

Frank S. SpearRensselaer Polytechnic Institute

(1977)

Tauern Window, Austria

(Selverstone et al, 1984)

P-T paths from zoned garnet

Tauern Window,Austria

(Selverstone et al, 1984)

Ernst, 1976

P-T paths and nappe tectonics - New Hampshire Spear et al. (2007)

Trace element thermobarometry

•Ti-in-quartz (Titaniq)

•Y in garnet

BF-17A - Western New Hampshire

Y zoning in garnet

4341 ppm - inner core

5346 ppm - outer core

29 ppm - rim

TM-730 - Strafford Dome, Central Vermont

Y concentration in garnet + xenotime assemblages

Tectonic loading at rates in excess of 8 cm/year

Diffusion studies: Rates of tectonic processes

•Ti-in-quartz (Titaniq)

•Mn in garnet

79-149d (New Hampshire: kyanite zone)

Grt

Ky St

Grt

79-149d (New Hampshire: kyanite zone)

Grt

CL image

79-149d (New Hampshire: kyanite zone) CL image

Grt

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79-149D Orfordville, NH: kyanite zone CL image

GrtQtz

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Peak T/Duration

550C/1.2 m.y.

575C/0.6 m.y.

600C/0.3 m.y.

TM-730 - Central VT. Staurolite-Kyanite zone

TM-730

Mn zoning

TM-730 - Mn diffusion modeling

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0.25 m.y.

2.5 m.y.

10 cm/year

10 cm/year