Geochemistry, mineralogy, and petrology of the sulfide mineralization and associated rocks in the area around Besham and Dir, northern Pakistan

The Himalayan mountain range is a geological manifestation of the collision of northward-moving Indo-Pakistan plate with the Asiatic plate. Kohistan arc terrane is sandwiched between these two plates. Proterozoic base metal (Zn-Pb) mineralization in the rocks of the Indo-Pakistan plate occurs along its northern margin in an area around Besham. Reaction skarn, due to metamorphism, has played an important role in the formation of various skarn minerals. The mineralogy, petrology and geochemistry of various ore bodies, their lead isotopic ratios, absence of volcanic rocks, and lack of footwall hydrothermal alteration favor a sediment hosted submarine exhalative-type origin for the Besham ore bodies.; Within the northwestern portion of the Kohistan arc terrane, the Dir metavolcanic sequence constitutes a northeast southwest trending belt. This sequence is dominantly composed of basaltic-andesite and andesite with subordinate basalt, high-Mg basalt, dacite, rhyolite, and pyroclastic breccia. Phase assemblages and chemistry suggest greenschist facies metamorphism with epidote-amphibolite facies conditions attained locally. Whole rock major, trace element, and rare earth element compositions of the sequence suggest a calc-alkaline affinity. Least squares modeling of the major oxides shows that the Dir volcanics series evolved from a high-Mg basalt parent liquid.; Copper mineralization in the Dir area is related to hydrothermal activity which is mainly confined to the metavolcanic sequence within the Kohistan arc terrane. Copper mineralization occurs in four different forms: (1) within quartz veins, (2) along foliation planes, (3) in disseminated form, and (4) as supergene enrichment. The whole rock major and trace element data suggest that the hydrothermal activity is responsible for chemical changes within the mineralized metavolcanics. The oxygen isotopic composition suggests the involvement of heavy ore forming fluids in the alteration and copper mineralization in these volcanics. Thallium has been correlated with K, Rb, Sr and Ba in both mineralized and unmineralized rocks. It is found as a useful pathfinder element for hydrothermal copper mineralization.