Sargipali galenas: Unusual lead-isotope data from eastern India

Abstract

Abstract. The Sargipali sulphide deposit, hosted by a sequence of metasediments of the Precambrian Gangpur Series, represents the stratiform and stratabound Pb-Cu mineralization. Lead-isotope analyses obtained from six galena samples of different forms and stratigraphical levels, yielded a model Pb age of 1665 Ma, which predates the episodes of deformation and metamorphism (~850 Ma) as well as syn-to late-tectonic magmatism. The model Pb age, on the contrary, shows a relationship to the closing phase of the Gangpur sedimentation (1700 Ma) in a shallow-water marine environment. The notable paucity of the interlayered volcanic rock in the deposit and its Pb-rich nature possibly point to its being the sedimentary exhalative (SEDEX) type. Documentary evidence for the Pb component from the geological environment of the "upper continental crust" is revealed by an exceptionally high/~(= 23sU/2~ and the slightly above average W(= 132Th/238U) values. These indicate that the source rock was initially rich in U-Th-Pb concentration. For the Sargipali ore Pb, the parent is assumed to be late Archean-lower Proterozoic soda granite.

Of gold masks, bronze mirrors and brass bracelets: Analyses of metallic artefacts from Samdzong, Upper Mustang, Nepal 450–650 CE

“…Unfortunately, nothing is available specifically for Mustang or Nepal although a few studies with published data are available for the neighbouring regions and East Asia. We have therefore had to compile data for metal artefacts, slag, rocks and ores, to obtain some broad regional signatures (Bhutta and Quareshi, 1997;Brill et al, 1997;Chiaradia al., 2006;Craddock et al, 2015;Ericson and Shirahata, 1985;Mabuchi et al, 1985;Pavlova and Borisenko, 2009;Pryce et al, 2014;Shah et al, 2010;Srinivasan, 1999;Vishwakarma and Ulabhaje, 1991;Li et al, 2009;Chang and Zhu, 2002). Interestingly, the results (Fig.…”