Chemical and Boron Isotopic Composition of Tourmaline in Baotan Tin Deposit, Northern Guangxi, South China

Abstract

Tourmaline is a common mineral in a variety of hydrothermal ore deposits (Slack 1996). Thanks to its wide P-T stability, resistance to weathering, variable composition, common presence of zoning and the dominant mineral host for boron in most crustal rocks, tourmaline not only can preserve a very good record of the composition of the fluid from which it crystallized, but also can trace the direction of fluid evolution (Trumbull et al., 1999, 2008). The Jiuwandashan-Yuanbaoshan area of Nouthern Guangxi is the oldest tin polymetallic region in South China. Tourmaline widely distributed from granite to oreforming hydrothermal vein and part in Sibao Group in this area. In this study, we focus on the chemical and boron isotopic composition of tourmaline in Pingying granite pluton and the related tourmaline type tin deposit in Baotan by Electron Microprobe and in-situ B isotopic analyses using LA-MC-ICP-MS. 2 Geological Setting Baotan tin deposit is located in the JiuwandashanYuanbaoshan region, Northern Guangxi, South China. It is in the western part of the Jiangnan Orogenic Belt, closely to the tectonic suture zone between the Yangtze and Cathaysia Blocks. The deposit is mainly controlled by a series of subparallel, NE-trending fractures and ore veins along its distributions, which are centered in the southeast margin of Pingying granitic pluton. This pluton, which has an outcrop area of ~15 km