The Hammett Grove Meta-igneous Suite; A possible ophiolite in the northwestern South Carolina Piedmont

Abstract

The Hammett Grove Meta-igneous Suite, here named formally, is composed of altered ultramafite (soapstone and serpentinite), metapyroxenite, metagabbro, and metabasalt lithodemes. It is interpreted to represent a dismembered ophiolite that may have formed as fore-arc basement to the Carolina arc terrane. This amphibolite-facies and retrograde greenschist-facies suite of metamorphosed, comagmatic igneous rocks crops out in the Piedmont of northwestern South Carolina near the eastern edge of the Inner Piedmont belt. The northeasternmost part of the suite lies within the Kings Mountain shear zone, which constitutes the Inner Piedmont belt-Kings Mountain belt boundary. The suite is interpreted as a thrust slice or klippe derived from the Kings Mountain belt, implying that the boundary is-at least in part-an overthrust. As ophiolites occurring in ancient orogenic terranes are often related to fundamental boundary tectonics, it is proposed that the Inner Piedmont-Kings Mountain belt boundary represents a terrane suture and marks an accretionary event. Thrusting of the Hammett Grove Suite over rocks of the Inner Piedmont resulted either from orthogonal terrane accretion or from transpression related to wrench faulting.

The Carolina Terrane in northwestern South Carolina: Insights into the development of an evolving island arc

“…Two and possibly three zoned intrusive complexes have been recognized west of the Bald Rock granite in northwestern South Carolina: the Wildcat Branch complex of Horkowitz (1984) and the Mean Crossroads complex of Dennis (1988); the 238 A. J. Dennis and J. W. Shervais Hammett Grove Metaigneous Suite of Mittwede (1989) may represent portions of a zoned complex disrupted and emplaced by late Paleozoic transpressive motion. The Wildcat Branch and Mean Crossroads complexes are crudely zoned from mafic-rich cores to more felsic, dioritic rims.…”

Talc resources of the conterminous United States

“…Deposits, not yet developed in 1990, probably formed by prograde, followed by retrograde, metamorphism of harzburgite and lherzolite. Mittwede ( 1989) concludes that the Hammett Grove Meta-Igneous Suite is a thrust slice of ophiolite and that its presence itnplies that the nearby Kings Mountain shear zone which fonns the Inner Piedn1ont-Kings Mountain belt boundary marks an accretionary suture. Mittwede ( 1989) provides additional structural detail and chemical analyses.…”