PETROLOGY AND ECONOMIC MINERAL INVESTIGATION IN BUNER GAH AREA, CHILAS, PAKISTAN

Abstract

The Buner Gah is a N-S trending stream that traverses the Kohistan Island Arc rocks in the Diamir District of Gilgit-Baltistan province of Pakistan. The area of investigation in the Buner Gah lies between latitudes of 35° 17` to 35° 28` N and longitudes 74° 16` to 74° 19` E. The purpose of this study was to investigate economic minerals in rocks and stream sediments and to find out their origin and make the tectonic model for mineralization. The study area represents Chilas complex and the Niat amphibolites of the Kohistan Island arc. The Chilas complex rocks exposed in the area belong to the main gabbronorite association and here only pyroxene-quartz diorite and tonalites are exposed. The rocks of Niat amphibolites contain diorites, tonalites and quartz monzonite. There are marble bodies too which are intruded by felsic aplite dykes. Skarn is formed in the Niat amphibolite belt. The skarn contains apart from carbonate matrix, quartz and diopside. Sulphide mineralization is noticed at one place in altered rock within the Niat amphibolite belt which through atomic absorption spectrometry analysis yield 0.01 ppm gold and 74.25 ppm silver. In the stream samples only a few chalcopyrite and pyrite grains could be observed. The skarn is also devoid of any economic mineralization. There are reports of gold occurrences in the placer sands of the Indus River near Buner Gah, which may indicate that the gold source may not be from the Buner Gah as this valley does not host much hydrothermal mineralization within the rocks.