Liefergebiets - Charakterisierung proterozoischer Goldseifen in Ghana anhand von Fluideinschluß - Untersuchungen.

Abstract

The gold-bearing Tarkwaian conglomerates of the so-called Banket Series in the Ashanti Belt are oligomictic and consist of vein-quartz pebbles within a quartzitic matrix. The matrix consists, besides fine grained quartz, of secondary carbonates, chlorite, muscovite, tourmaline, epidote, actinolite, rutile, altered plagioclase, detrital zircon and opaque minerals. The opaque phases are mostly hematite and magnetite, which occur in about the same proportions. Free particles of gold and pyrite are rare.Fluid inclusion investigations revealed that the quartz-pebbles of the conglomerates contain predominantly CO2-rich fluids, some of which have unusually high densities (up to 1.13 g/cm3). These inclusions were probably trapped in the provenance area of the quartz pebbles. The matrix of the conglomerates is dominanted by H20-CO2-rich inclusions.The Banket Series conglomerates are underlain by the Kawere Series. The conglomerates of this series are polymictic and frequently matrix supported. Furthermore, the quartzitic matrix of the conglomerates contain small amounts of muscovite, plagioclase and epidote. These conglomerates carry no economic gold-contents, which are normally below 50 ppb. Quartzpebbles ofthese conglomerates possess H20- and H20-CO2-rich inclusions.