Potential for ruby mineralization in upper Kaghan, NW Himalaya
Abstract
The Precambrian to Early Paleozoic basement of the upper Kaghan has a cover of metamorphosed sedimentary and volcanic-rocks of Late Paleozoic-? Early Triassic age. About 3 km NE of Naran, the cover rocks contain a few tens of meters thick marbles containing thin (mostly cm) micaceous bands one of which hosts tiny (up to a millimeter) grains of pinkish red corundum. The occurrence of the ruby corundum is similar to the Hunza and Azad Kashmir ruby deposits, thereby necessitating further search in the area.
The marbles consist of calcite ± muscovite ± biotite ± quartz ± pyrite. The micaceous bands consist of the two micas + pyrite + opaque oxide ± calcite ± rutile ± quartz ± plagioclase ± chlorite ± garnet. Microprobe analyses are Presented for the common phases. Petrography and Preliminary geothermobarometry suggest that the marbles were metamorphosed at 450-500oC, 6 kbar, followed by a lower temperature (280oC) overprinting of chlorite-epidote grade during retrogression. Considerable inter- and intra-granular variations in the Cr content of green mica and ruby suggest a lack of mobility of Cr during metamorphism. The abundance of micaceous minerals and pyrite, and local occurrence of garnet and corundum suggest that the thin bands associated with the marbles were highly aluminous and iron-rich (?lateritic), and that reducing environments Prevailed during their digenesis.
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