Magmatic evolution characteristics of Xiangshan volcanic-intrusive complex from the Gan-Hang Belt:Studies on the mineral chemistry of plagioclase and biotite
ZHAO Mian;YANG ShuiYuan;ZUO RenGuang;ZHAO KuiDong;JIANG YaoHui;LING HongFei;CHEN PeiRong;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences;Collaborative Innovation Center for Exploration of Strategic Mineral Resources,Faculty of Earth Resources,China University of Geosciences;State Key Laboratory for Mineral Deposits Research,School of Earth Sciences and Engineering,Nanjing University;
Biotite and plagioclase can be the indicator of magma evolution. We analyze the chemical compositions of these minerals which crystallized from the Xiangshan volcanic-intrusive complex in the Gan-Hang Belt,SE China,through EPMA method. The study shows that the plagioclase from the porphyroclastic rhyolitic lava,granitic porphyry and quartz monzonite porphyry is andesine without zoning structure. The magnesio-biotite and ferri-biotite which are found in quartz monzonite porphyry are similar to that in the mafic microgranular enclaves( MMEs) in the classification diagram for biotite. But the biotite from porphyroclastic rhyolitic lava and granitic porphyry has lower Mg content than the biotite from quartz monzonite porphyry. Combined the characteristics of biotite and plagioclase with former research data,it shows that the porphyroclastic rhyolitic lava and granitic porphyry were derived from crustal material,without significant addition of mantle-derived magma. The higher Mg contents of biotite from quartz monzonite porphyry indicate an involvement of mantle-derived magma,and the crust-mantle mixing occurred before the crystallization of biotite.