Petrology and chemistry of meta-igneous rocks in the Albemarle area, North Carolina slate belt

Abstract

The rocks are volcaniclastics, flows, and sills of a calcalkaline suite of early Paleozoic and possibly late Precambrian age, ranging from rhyolite to basalt. Glass was originally a major constituent of the units of felsic to intermediate composition. Low-rank metamorphism caused mineral assemblages that are apparently in the quartz-albite-muscovite-biotite chlorite subfacies of the Abukuma-type greenschist facies. Quartz and albite are nearly ubiquitous, and K-feldspar is near-maximum microcline. Chlorite, actinolite, and epidote are major constituents of the intermediate to mafic units. Devitrified felsic metatuffs interbedded with argillite are similar chemically to quartz keratophyres, whereas the metarhyolites are only slightly more sodic than normal calc-alkaline rhyolites which suggests that the metatuffs underwent metasomatism after deposition. Semi-quantitative and whole-rock analyses were performed.