Plagioclase feldspar as an indicator of provenance in sedimentary rocks

TLDR: In this article, a technique utilizing a petrographic microscope with a flat stage for analysis of provenance has been developed, which concentrates feldspar in the medium or coarser sand range by flotation techniques, and then separates this concentrate by means of heavy liquids into potash, albite, oligoclase-andesine, and calcic plagioclase.

Abstract: A technique utilizing a petrographic microscope with a flat stage for analysis of provenance has been developed. Procedure is to concentrate feldspar in the medium or coarser sand range by flotation techniques, then to separate this concentrate by means of heavy liquids into potash feldspar, albite, oligoclase-andesine, and calcic plagioclase. Thin sections of these plagioclase separations are examined for twin characteristics (C-twins, A-twins, and untwinned), and zoning characteristics (progressive, oscillatory, and unzoned). This leads to inferences about the presence of metamorphic, plutonic igneous, or volcanic-hypabyssal rocks in the source area. Only the predominant rock type usually can be detected. An exception to this is volcanic and hypabyssal rocks, which commonly yield pl gioclase with diagnostic properties.