Chemistry of inner piedmont metamorphic rocks hosting a stratiform tin occurrence near Forest City, NC

Conference · Tue Jan 01 00:00:00 EST 1985 · Geol. Soc. Am., Abstr. Programs; (United States)

OSTI ID:6317073

Moore, W J; Rowe, Jr, W D; Eckert, J R

Concordant, leucocratic lenses in regionally persistent upper amphibolite-grade biotite-amphibole gneiss have been identified by Carr and others (1984) as the bedrock source of alluvial cassiterite in the Inner Piedmont Belt of North and South Carolina. The lenses are composed of quartz, microcline, and dravitic tourmaline plus minor biotite, muscovite, and spessartine garnet; most are barren. Partial major-element analyses of drillcore samples from the gneiss suggest a protolith intermediate in composition between graywacke and arkose. Sill-like, two-mica granitoid bodies interlayered with the metasediments are corundum-normative and are granodioritic in composition. Variation plots of selected trace-element abundances discriminate effectively among (1) biotite-amphibole gneiss enriched in Mn, Zn, and V; (2) granitoids enriched in Ba, Sr, and Zr; and (3) laminated gneisses below the tin zone containing elevated levels of Ni and Cr that suggest an addition of mafic (volcanic.) material to the protolith. Lithium contents are as high as 860 ppm in 5 of 9 gneiss samples and in all 4 granitoids are 3-10 times the average abundance in common igneous and sedimentary rocks; biotite and amphibole are the probably host minerals. Lithium-charged fluids generated during metamorphism may have aided local partial melting and remobilization of tin dispersed (as detrital cassiterite.) in the sedimentary protolith. Li may prove useful in locating other stratiform tin occurrences in metamorphic terranes and in understanding processes of localization. Carr, R.S., III, and others, 1984.

• Research Organization: Geological Survey, Reston, VA (USA)
• OSTI ID: 6317073
• Report Number(s): CONF-8510489-
• Journal Information: Geol. Soc. Am., Abstr. Programs; (United States), Vol. 17; Conference: 98. annual meeting of the Geological Society of America, Orlando, FL, USA, 28 Oct 1985
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
METAMORPHIC ROCKS
CHEMICAL COMPOSITION
MINERALOGY
TIN ORES
NORTH CAROLINA
MINERALIZATION
BARIUM COMPOUNDS
DRILL CORES
GARNETS
GEOCHEMISTRY
LITHIUM COMPOUNDS
MICA
QUARTZ
STRONTIUM COMPOUNDS
ALKALI METAL COMPOUNDS
ALKALINE EARTH METAL COMPOUNDS
CHALCOGENIDES
CHEMISTRY
FEDERAL REGION IV
MINERALS
NORTH AMERICA
ORES
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
ROCKS
SILICATES
SILICON COMPOUNDS
SILICON OXIDES
USA
580400* - Geochemistry- (-1989)