Lead isotope signature of the Proterozoic sediment-hosted base metal deposits at the margin of the Indian plate in Besham area, northern Pakistan
Abstract
Proterozoic base metal deposits in the rocks of the Indian plate occur along its northern margin at the Pazang and Lahor properties near Besham. These are stratiform exhalative type deposits which are highly deformed and regionally metamorphosed. Lead isotope studies were carried out on these deposits. Lead isotope ratios yield model ages of 2120-2199 Ma (Proterozoic)for both the Pazang and Lahor deposits. The assumed minimum age of mineralization is 2077 Ma, as suggested by the secondary isochron. These deposits are more primitive in terms of age and have lower g values relative to the well known sediment-hosted deposits elsewhere in the world. The non-radiogenic isotopic composition and the homogeneity of the ore lead in both Pazang and Lahor ores suggest a well-mixed common source and similar processes for the formation of these ores.
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