LA-MC-ICPMS in-situ boron isotope analyses of tourmalines from the Shangbao granites (southern Hunan Province) and its geological significance
GUO Hai-feng;XIA Xiao-ping;WEI Gang-jian;WANG Qiang;ZHAO Zhen-hua;HUANG Xiao-long;ZHANG Hai-xiang;YUAN Chao;LI Wu-xian;State Key Laboratory of Isotope Geochemistry,Guangzhou Institute of Geochemistry, Chinese Academy of Sciences;University of Chinese Academy of Sciences;
LA-MC-ICPMS tourmaline in-situ boron(B) isotope analysis method, which is very efficient and economic, was newly established in recent few years. The LA-MC-ICPMS tourmaline in-situ B isotope analyses for the Shangbao tourmaline-bearing two mica granites exhibit that these tourmalines have very constant11B/10B ratios(3.9908 3.9979) and δ11B values(Mean=( 12.86±0.19)‰). Combined with regional geological data and other previous boron isotope data, we infer that the B element of the Shangbao granites was probably derived from sedimentary rocks, and a possible source was the Carboniferous or Permian sedimentary strata which is near to the Shangbao pluton, or sedimentary materials which were deeply buried in the crust. During Late Cretaceous, as the whole South China Block was under an extensional setting, the underplating mantle-derived magmas heated the overlying sedimentary materials, resulting in their partial melting and the generation of strongly peraluminous magmas. The tourmaline crystallized during the late stage of the evolution of these magmas.