Primary geochemistry and secondary dispersion from gold prospects in Karakoram and Hindu kush, northern Pakistan.

This project is aimed at finding the best methods for geochemical exploration in the fast eroding lofty mountains of northern Pakistan and includes studies of parts of the Khoistan and Karakoram tectonic terranes. In the Chitral area (Karakoram terrane), three interlinked studies were undertaken to determine the primary concentration of elements, their dispersion into drainages and the regional distribution of trace metals within drainages. Panned concentrates are most effective in detecting the mineralization due to the dominance of clastic dispersion and the insolubility of many metallic minerals in the cold alkaline river waters. The regional survey reveals that Chitral has a high potential for mineralization and many valleys contain polymetallic anomalies. The rock geochemistry of the low grade gold prospect in the Shoghor area demonstrates the concentration of As, Sb and Ag along faults and in iron rich siliceous carbonate units and the secondary clastic enrichment of gold in the siliceous carbonates. In the Kohistan terrane, studies consisted of an orientation study in the Bagrot valley, a regional survey of the Gilgit area and an experimental investigation of the stability of the uraninite- pyrite- gold assemblage. The Bagrot study demonstrates that panned concentrates are the best medium for mineral exploration because of the coarse grained nature of the gold and the dominance of clastic dispersion. The regional panned concentrate survey of the Gilgit area demonstrates that this part of Kohistan has a high mineral potential, particularly for precious metals. The gold- pyrite- uraninite assemblage in the rivers around Gilgit, particularly the Indus, is very similar to that from the Archean Witwatersrand basin and has been proposed as a modern analogue. Gold and pyrite are derived from the Chalt volcanics and quartz veins near the Northern Suture while the origin of the uraninite is unknown, presumably from the Karakoram batholith or pegmatites.