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An ultramafic schist body near Walhalla, South Carolina, contains abundant chlorite, tremolite, and olivine. The olivine is of metamorphic origin and typically occurs as centimeter-sized, sieve-textured porphyroblasts. Accessory minerals include anthophyllite, serpentine, dolomite, ilmenite, and pyrite. Bulk chemical analyses indicate that the ultramafic rocks contain 39.5 ± 1.5 wt percent SiO2, generally about 30 wt percent MgO, and AI2O3 in excess of 5 wt percent.

Texturally, mineralogically, and chemically, the Walhalla ultramafic body is very similar to ultramafic schist bodies at Clemson and Seneca, South Carolina. All three bodies occur in the Inner Piedmont belt and were subjected to middle amphibolite facies metamorphism. The peak metamorphic assemblage, chlorite + tremolite + olivine ± anthophyllite, is common to the three localities. The occurrence of dolomite in many samples indicates that the fluid phase present during prograde metamorphism contained CO2. The ultramafic rocks were affected by a retrograde metamorphic event (lower amphibolite facies?), as evidenced by late-stage growth of serpentine or talc. Development of a mosaic equigranular olivine texture, and microfolding of chlorite laths, are localized features that also originated after the peak of prograde metamorphism.

Although regional metamorphism effected a thorough recrystallization of the ultramafic protolith, it may have been principally isochemical. If so, the ultramafic protolith was itself relatively aluminous, with a general chemical affinity to plagioclase (or spinel or garnet) peridotite. Possibly, the bodies represent dismembered ultramafic cumulates torn from an ophiolite sequence. However, rare-earth element (REE) abundances are higher, and the chondrite-normalized patterns are flatter in the Piedmont ultramafic rocks than in corresponding ophiolitic cumulates.

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