OVERVIEW OF THE ASHE METAMORPHIC SUITE AND ITS MINERAL RESOURCES

The Ashe Metamorphic Suite (AMS) and correlatives (Tallulah Falls Formation, Lynchburg Group) along with the Alligator Back Metamorphic Suite comprise a SW-NE trending metamorphic terrane stretching from north Georgia through central Virginia. The AMS consists mostly of paragneisses and schists with lesser amounts of interlayered amphibolites, and minor dunite and altered ultramafic bodies. Amphibolites are present throughout the AMS but are significantly more abundant immediately SE and NW of the Grandfather Mountain Window. The AMS is believed to be Neoproterozoic to early Cambrian in age and is intruded by numerous Paleozoic felsic bodies. Most of the AMS was metamorphosed at middle to upper amphibolite-facies conditions, with localized eclogite-facies assemblages along its NW margin.

Most researchers suggest the AMS was deposited in a distal marine environment with the amphibolites being of MORB origin and the dunites representing mantle material. It was deformed and metamorphosed during three Paleozoic orogenic events.

The AMS and its associated intrusives have been exploited for mineral resources, including:

• gneiss and amphibolite as crushed stone,

• vermiculite as insulating material,

• olivine in the dunites as refractories and abrasives,

• muscovite from pegmatites in wallboard compound, electrical, heat insulators, and lampshades,

• feldspar from pegmatites in ceramics and glass manufacture,

• quartz from pegmatites in glass, solar cell, fiber optic cable, and computer chip manufacture,

• emeralds from the boundaries between the pegmatites and enclosing AMS.