Chemical and boron isotopic compositions of tourmaline at the Dachang Sn-polymetallic ore district in South China: Constraints on the origin and evolution of hydrothermal fluids

The Dachang Sn-polymetallic ore district in South China is the second largest tin world with a reserve of over one million tonnes. Zn-Cu skarn and stratiform, massive, vein Sn-Pb-Zn ores are all present this district. This has led to debate as whether Sn orebodies were formed by Cretaceous magmatic-hydrothermal replacement or Devonian submarine exhalative-hydrothermal sedimentation. Here, we systematic investigation major, trace element, boron isotopic compositions different types tourmaline Tourmaline disseminated Longxianggai granite pegmatite veins belongs schorl series high contents Li, Zn, Ga. ?11B value primary magma estimated be about ?13‰, close global average (?11‰) for S-type granites. from quartz-tourmaline similar chemical composition magmatic likely hydrothermal fluids exsolved evolved granitic melt. initial also calculated ?13‰. Tourmalines sulfide Lamo deposit have higher Mg/(Mg+Fe) lower Na/(Na+Ca) ratios Be, Ge, Sr, than tourmaline. These patterns reflect input elements derived host limestone. values between ?13 ?10‰, suggesting related granite. stratiform Changpo-Tongkeng extremely Mg-rich mostly belong dravite series. They Sc, V, Cr, show positive Eu anomalies. these B- Sn-rich ?15 that origin. most same source, but may interacted volcanic rocks.