地质学报2017，Vol.91Issue(12)：2651-2666,16.
东昆仑东段香加南山花岗岩基斜长石成分组成与岩浆演化和混合作用
Components of the Plagioclase of Granitic Batholith in Xiangjiananshan in the Eastern Section of East Kunlun and their Implications for Magma Evolution and Mixing Effect
摘要
Abstract
Granitic batholith in Xiangjiananshan in the eastern East Kunlun Orogenic Belt presents the distinct features of magma mixing.Plagioclase,as a main rock-forming mineral,is an effective tool to study petrogenesis,magma evolution and magma mixing.Petrography and mineral chemistry of plagioclases in host rock and its mMic microgranular enclaves (MMEs) in granitic batholith of Xiangjiananshan were studied through electron microporobe (EMPA).The results show that the plagioclases with oscillatory zonings(39～48,21～36) and plagioclase-bearing minerals(29～45,14～32) in host rock and the plagioclases xenocrystals (41 ～ 49,35 ～ 36,43 ～ 49,31 ～ 47,27 ～ 38) in MMEs have a serial geochemical evolution of anorthite-albite component value (An value),and part of plagioclase core has high An values (59～72) due to late fluid alteration.Most plagioclases in matrix of the MMEs have core-rim structures with An-value discontinuities from core (52,31) to rim (33 ～ 37,25).Minor plagioclases have lower An values (49)in cores due to alteration,with higher An values in cores(55～71)than in rim(46～49).In addition,some plagioclases in the matrix are jigsaw-like patches,with high An(66)in dark areas and low An(33～39)in light area.The plagioclase xenocrystals in MMEs have been divided into two categories according to mineral contents.The "clean" ones without minerals have apparent oscillatory zonings and polysynthetic twins,and a narrow fluctuated range of An-value(41～49,35～36).Whilst the "dirty" ones with minerals have an unsmooth fluctuation of An-values (43～49,31～47,27～38),with higher An-values in some testing points(78)and accretion rim(73)due to alteration.The studies above show that the normal evolutional sequence of plagioclases in the host rock represents the magmatic evolution of the host rocks with the magma evolving from mafie to feslie gradually.After the MMEs entered the host rock,the plagioclases in the MMEs would be eroded and crystallized due to decreasing of temperature,pressure and water saturation.Plagioclases xenocrystals in enclaves,which originated from host rock,vary in composition and structure due to change in temperature and pressure as well as growth at the late stage.The complex oscillatory zonings of plagioclases in granitic batholith of Xiangjiananshan and their MMEs are the results of injection of mantle-derived mafic magma into felsie magma.关键词
东昆仑造山带/花岗岩/斜长石/矿物化学/岩浆演化/岩浆混合Key words
East Kunlun Orogenic Belt (EKOB)/granite/plagioclase/mineral chemistry/magma evolution/magma mixing引用本文复制引用
陈国超,李小兵,裴先治,李瑞保,李佐臣,刘成军,陈有炘,裴磊,王盟,张玉..东昆仑东段香加南山花岗岩基斜长石成分组成与岩浆演化和混合作用[J].地质学报,2017,91(12):2651-2666,16.基金项目
本文为国家自然科学基金项目(编号41472191、41502191、41172186)、中央高校基本科研业务费专项资金项目(310827161002、310827161006)和青海省国土资源厅-中国铝业公司公益性区域地质矿产调查基金项目(编号:200801)的成果. （编号41472191、41502191、41172186）
