%0 Journal Article
%T Timing and petrogenesis of the Damiao granodiorite, Siziwangqi, Inner Mongolia<br>内蒙古中部四子王旗大庙岩体时代及成因
%A ZHANG YongMei
%A ZHANG HuaFeng
%A LiU WenCan
%A ZHOU ZhiGuang
%A <br>章永梅
%A 张华锋
%A 刘文灿
%A 周志广
%J 岩石学报
%D 2009
%I 
%X A huge volume of Late Paleozoic to Early Mesozoic granitoids is located in the middle part of the Inner Mongolia, which constitutes a giant granitic belt trending EW. As a representative of those intrusions, the Damiao granitoid occurs in the northern portion of the Siziwangqi area, mainly composed of mid-coarse-grained granodiorite with abundant maric microgranular enclaves (MMEs) occurring. The MMEs can provide important clues for genesis and evolvement of granites. Petrological, geochronological, mineralogical results about the MMEs and host granite are presented in this paper. Zircons from the granite give a LA-ICPMS mean U-Pb age of 265±TMa (2σ), and biotite grains from MME yield a Rb-Sr isochron age of 253±5Ma (MSWD =0.85). MMEs generally show ellipsoidal shape, and minerals in microscope are characterized by igneous and disequilibrium texture, which are considered as important evidences for magma mixing. The plagioclase phenocrysts have low composition end member of the anorthite (An) in the coreand rim, compared to that of the mantle, while the contents of MgO in biotite phenocryst core and rim are lower than that of the mantle, both of them show oscillatory zone in the mantle. The resembled oscillatory variations in composition of the plagioclase and biotite phenocrysts from MME indicate that the crystallization environment was changed, due to magma mixing. The major and trace element compositions of the host granite and MEEs also show evidence on their genesis of magma mixing. The Rb/Sr-K/Rb diagram indicates that the MEEs are neither products by mineral fractional crystallization nor biotite accumulation. The Ce/Pb versus Ce and Ba, P_2O_5 versus δEu diagrams together with other trace elements bivariate ratio diagrams, imply that MMEs were generated by magma mixing, evidently consistent with their physical and chemical conditions. Geochemistry of the Damiao granodiorite is different from TTG or subduction-related Adakites. Underplating and magma mixing is a dominated mechanism for generation of the granite. In addition, the mineral chemistry and geochemistry indicate that the Damiao granodiorite is likely to form in syn-collisional environment.
%K Mafic microgranular enclave
%K Granodiorite
%K Magma mixing
%K Siziwangqi
%K Inner Mongolia<br>暗色微粒包体
%K 花岗闪长岩
%K 岩浆混合作用
%K 四子王旗
%K 内蒙古
%U http://www.alljournals.cn/get_abstract_url.aspx?pcid=E62459D214FD64A3C8082E4ED1ABABED5711027BBBDDD35B&cid=621CF755B1A341E5&jid=2013B5467E3054B1614CEC199353FCED&aid=BEC8AD6C5BEBA73778CC8C888B3E90B2&yid=DE12191FBD62783C&vid=C5154311167311FE&iid=59906B3B2830C2C5&sid=BEFEF55A1BF6A334&eid=0A97B65BD82A9CE2&journal_id=1000-0569&journal_name=岩石学报&referenced_num=5&reference_num=106