ENCLAVES, SCHLERIEN, AUTOLITHS, XENOLITHS AND DIKES AS CLUES TO STRUCTURE AND PLUTON EXPOSURE LEVEL - THE GREAT FALLS METAGRANITE ON THE CAROLINA SLATE BELT - CHARLOTTE BELT BOUNDARY, SOUTH CAROLINA

Low-grade felsic and mafic rocks of the Carolina Slate Belt (?) and Charlotte Belt metadiorites and metagranites are intruded by the Great Falls Metagranite (GFM). The texture of the granite is mostly hypidiomorphic granular with minor porphyritic and aplitic textures. Quartz veinlets, minor small pegmatites and numerous narrow (0.2-1.5 m. wide) metamorphosed mafic dikes cut the metagranite.

Larger rock exposures frequently display enclaves, mafic blebs, planar mafic layers, autoliths, xenoliths, aplite dikes and schlerien layers. Those features provide a record of the magma composition, flow and crystallization history of the older stoped and disrupted rocks.

Medium-grained magmatic enclaves reveal complex histories and strain as the magma approached solidus. Enclaves are fine-grained relative to the granite and represent altered co-magmatic, injected material. Enclaves and schlerien are partly resorbed.

Mafic-rich blocks often have fairly rectangular shapes and a sharp, intrusive margin with little alteration, thus are xenoliths, granite sometimes cuts through a single xenolith. The metagranite stoped and assimilated or partially assimilated smaller mafic xenoliths, creating wispy ghostly almost indistinct autoliths.

The pluton probably represents the deep-seated portion of an acidic sub-volcanic complex which was possibly a source for rhyolitic and mafic flows in the Carolina Slate Belt. Larger dikes cutting the granite may have been deep seated feeders for mafic flows of the slate belt.

Some rock fragments in metagranite are unrelated to the igneous body itself. These xenoliths are located near their original positions of detachment or those with greater density (mafic) - deeper in the intrusion.

In most exposures, metagranite is deeply eroded and altered to saprolite, outcrops are not sufficient to determine contact or reliable structural relationships.