60 Appalachian Petrology: A Session to Honor the Career of Dr. Robert J. Tracy (Posters)

Sunday, 22 March 2020
8:00 AM - 12:00 PM
Grand Ballroom A–D

GEOCHEMISTRY OF ANTHOPHYLLITE - GARNET - TALC SCHISTS FROM THE LITTLE PINE GARNET MINE, NORTH CAROLINA: TECTONIC IMPLICATIONS FOR THE MARS HILL TERRANE AND GRENVILLE BASEMENT

Paper number: 60-1
Program: Theme Sessions
Time: 8:00 AM – 12:00 PM

Authors

Abstract

The Little Pine Garnet Mine (LPGM), located between the Mars Hill and Grenville basement terranes in the Western Blue Ridge province of the Appalachian Mountain Belt has outcrops of anthophyllite – chlorite – biotite ± garnet ± staurolite schists (group I), garnet – biotite – anthophyllite gneisses (group II), and talc- chlorite – garnet ± anthophyllite ± gedrite schists (group III), interbedded with quartzofeldspathic mica gneisses. These mineral assemblages are characteristic of protoliths enriched in Mg, but with significant amounts of Al, making them rather unusual. Geochemical analysis of these rocks reveals that groups I & III were mostly E-MORBs affected by hydrothermal alteration, whereas group II rocks were likely shales. None of the rocks analyzed have any subduction zone signatures characteristic of boninites or High Mg andesites. Isocon diagrams show that the LPGM schists and gneisses were depleted in Si, Ca, Na, Sr, Ba, Ni, V, and Sc, but enriched in Mg, Fe, La, and Ce relative to E-MORBs. Petrographic group I, containing fine-grained garnet showed slight losses in Y and Yb, whereas petrographic group III with very coarse grained garnet showed significant gains of these elements. These results suggest that the E-MORBs were affected by hydrothermal alteration on the seafloor, which in turn suggests the existence of a small ocean basin between the Mars Hill terrane and Laurentia.

Geological Society of America Abstracts with Programs. Vol. 52, No. 2

doi: 10.1130/abs/2020SE-344149

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