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Title:: In-situ Boron Isotopic Analysis and Its Geological Significance of Tourmalines from Zhongzuo Pegmatite Veins in Quyang Area of Hebei, China

Author(s):: HOU Jiang-long; WANG Deng-hong; LI Jian-kang; WANG Cheng-hui; HUANG Fan; CHEN Zhen-yu; MLR Key Laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037, China

Keywords:: isotope geochemistry; tourmaline; in-situ boron isotope; LA-MC-ICPMS; pegmatite vein; isotope fractionation; magma degassing; Hebei

Abstract:: Tourmalines are discovered in different types of deposits and are often used to investigate diagenesis and mineralization environment. For the significant isotope fractionation, the tourmalines have been widely used in geochemical tracer study of granite, pegmatite and various hydrothermal deposits. On the basis of polarizing microscope identification, the insitu boron isotopic analysis of tourmalines from Zhongzuo pegmatite veins in Quyang area of Hebei was carried out by LA-MC-ICPMS. The results show that δ¹¹B values from Zhongzuo pegmatite veins are -10.5‰--7.3‰, which are located in the variation ranges of peak values of pegmatite; δ¹¹B values from Zhongzuo pegmatite veins are almostly the same to Tanco pegmatites in Manitoba, Canada; according to the field and micropetrography characteristics of tourmalines, the δ¹¹B values from pegmatite with macrograined tourmalines are lower 2‰ than those of pegmatite veins with fine-grained tourmalines, because the former is formed during magma degassing and the latter may be crystallized before boron fractionation; B of tourmaline from Zhongzuo pegmatite veins mainly derives from the exsolution of magma-hydrothermal fluid, and Fe and Mg in the surrounding rock provide necessary sources for the forming of tourmalines.