Southeastern Section - 60th Annual Meeting (23–25 March 2011)

Paper No. 57
Presentation Time: 5:30 PM-8:00 PM


STANDER, Amy1, COLE, Meredith2, DUCKER, E.A.2, CHAMBERS, Benjamin2, CHEATHAM, Rachel2, JOHNSON, K.A. Burke2, CLAYTON, Benjamin2, FLEISHER, Christopher J.2 and SWANSON, Samuel E.2, (1)Geosciences, University of Rhode Island, South Kingston, RI 02881, (2)Geology, University of Georgia, Athens, GA 30602,

Spodumene (Spd)-bearing (ore) granitic pegmatites samples from the Lithium Corporation of America (LCA) Quarry tin-spodumene belt of North Carolina were collected in 1985. The LCA Quarry exposed ore-bearing pegmatites and barren granitoid intrusions (see paper by Cameron et al, this meeting), both hosted by amphibolite (Cameron et al., this meeting). The purpose of this study is to use the mineralogy of the Spd-bearing or Aore@ pegmatites to test for possible relations to the barren granitic rocks.

The Spd-bearing pegmatites are the youngest granitoid intrusions exposed in the LCA quarry. Sills of ore pegmatite occur in the amphibolite and intrude barren granitic rocks. A zone of intrusive breccia occurs along the contact of the Spd and barren pegmatites. The breccia has a Spd-bearing matrix and contains blocks of amphibolite and barren granitic rocks. Spd-bearing pegmatites lack internal zoning and contain coarse-grained Spd (up to 30 cm long) in a fine to coarse-grained matrix of Qtz, Pl, Ksp, Ms, and Be. Spd crystals are fractured and healed by fine-grained Qtz-Fs. Rims of some Spd crystals have a symplectic texture formed by a intergrowth of Spd and Qtz. The mineral assemblage is Pl+ Ksp+Qtz+Spd+Ms+Brl.

Mineral compositions determined by electron microprobe reveal the evolved character of the ore pegmatites. Pl is Na-rich (95.1 to 98.2 mole % Ab). Unexsolved Ksp has grid-iron twins and is somewhat sodic (4.8 to 5.3 mole % Ab). Muscovite contains a modest celadonite component (FeOt+MgO = 2.7 to 3.8 wt %). Halogen content of Ms is low, generally below detection limits). Spd is near end-member composition, while beryl contains 1-2 wt % Na2O.

The mineral assemblages and ages of Spd-bearing pegmatites are similar to the Cherryville quartz monzonite (CQM) (Kish, 1977), a large pluton just to the west of the tin-spodumnene belt. Similar compositions of Ms, Ab, Ksp in ore granites and post-tectonic barren granites suggest a lineage: CQM to barren post-tectonic granite to Spd-bearing pegmatites.