A region of migmatitic felsic paragneiss and pelitic schist containing concordant pods of serpentinite, talc schist, talc-amphibole schist, amphibolite, and metagabbro- here called the Burks Mountain complex-occurs in the southeastern limb of the Kiokee antiform, an Alleghanian D3 structure in the eastern Piedmont of Georgia and South Carolina. A similar region of migmatitic felsic paragneiss containing small pods of metamorphosed mafic and ultramafic rocks, which occurs in the northwestern limb of the Kiokee antiform, is inferred to be a continuation of the Burks Mountain complex across the crest of the antiform. The composition of the felsic paragneiss and pelitic schist of the Burks Mountain complex suggests derivation from graywacke and shale, respectively. Relict textures preserved in mafic and ultramafic rocks of the complex, along with preliminary whole-rock geochemistry, indicate derivation from ultramafic tectonite (harzburgite), olivine-pyroxene cumulate (wehrlite, olivine pyroxenite), pyroxene-plagioclase cumulate (gabbro, anorthositic gabbro), and mafic volcanic rock. These protoliths suggest an origin as part of a cumulate mafic and ultramafic intrusive and extrusive complex with some associated mantle tectonite. The complex was disrupted prior to or during amphibolite facies regional metamorphism. The mechanism of disruption is not clear. Possible modes of origin include accumulation as an olistostrome, accumulation in a subduction-related accretionary complex, and formation as extreme boudinage during a regional deformation event. The crystalline rocks in the core of the Kiokee belt (including the Burks Mountain complex) are contained in the footwall of a major ductile shear zone (the Modoc zone) that experienced oblique, down to the north-northeast displacement during the early part of the Alleghanian orogeny. Prior to the Alleghanian orogeny, the Burks Mountain complex was located beneath rocks of the Carolina slate belt that are presently exposed north of the Modoc zone. The Burks Mountain complex may have been derived from a unit within the Carolina slate belt or from a Precambrian basement(?) unit beneath the Carolina slate belt. Alternatively, in view of a unique lithostratigraphy, the Burks Mountain complex may be included in a terrane, exotic with respect to both North America and the Carolina slate belt, which was tectonically incorporated into the Appalachians prior to the Alleghanian orogeny.
|Original language||English (US)|
|Number of pages||12|
|Journal||Special Paper of the Geological Society of America|
|Publication status||Published - Jan 1 1989|
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