川西义敦岛弧中生代典型花岗岩体矿物学、地球化学特征及岩浆来源探讨
发布时间：2018-07-15 11:27
【摘要】：义敦岛弧是位于松潘—甘孜褶皱带和羌塘地体之间的三叠纪火山岛弧。稻城岩体和海子山岩体分别为义敦岛弧上出露的晚三叠世和白垩纪花岗质岩体。结合岩石地球化学,以及偏光显微镜和电子探针(EPMA)、扫描电镜(SEM)对上述岩体进行了系统的矿物学研究,结果表明:两个岩体的主要造岩矿物为斜长石(中长石—更长石),钾长石(正长石)、石英和黑云母(铁叶云母—铁质黑云母),副矿物为锆石、榍石、磁铁矿和磷灰石等;黑云母的成分表明两个岩体的源区均为壳幔混源。稻城岩体属高钾钙碱性系列,具过铝质特征的花岗岩,海子山岩体为高钾钙碱性—钾玄岩系列,同样具过铝质特征。根据锆元素饱和浓度温度计和稀土元素饱和浓度温度计对两个岩体进行了温度限定,稻城岩体岩浆形成的平均上限温度为783℃,海子山岩体岩浆形成时的平均上限温度为844℃。结合前人研究结果,笔者等认为稻城岩体为高分异I型花岗岩,可能为与扬子克拉通有关的晚古元古代至早中元古代的下地壳物质,在甘孜—理塘洋向西俯冲和闭合之后的弧—陆同碰撞背景下,因幔源岩浆的底侵作用而发生部分熔融,同时伴有少量的亏损地幔成分加入,因密度上升至中上—上地壳深度侵位,并且侵位后经历了快速的冷却过程,在侏罗纪之初冷却至300℃以下;海子山岩体为与俯冲有关的造山后伸展环境下形成的白垩纪A2型花岗岩,岩浆来源同样为地壳物质伴有少量地幔物质混合而成,且在地壳中侵位深度较浅,之后经历快速的冷却过程。
[Abstract]:Yidun island arc is a Triassic volcanic island arc between Songpan-Ganzi fold belt and Qiangtang terrane. The Daocheng and Haizishan intrusions are late Triassic and Cretaceous granitic rocks respectively. Combined with rock geochemistry, polarizing microscope and electron probe (EPMA) and scanning electron microscope (SEM), a systematic mineralogical study of the rock mass was carried out. The results show that the major rock-forming minerals of the two bodies are plagioclase (mesopaglitic feldspar), potash feldspar (orthoclase), quartz and biotite (Ironite-ferric biotite), and accessory minerals such as zircon, sphene, magnetite and apatite. The composition of biotite indicates that the source regions of the two rocks are crust-mantle mixing. The Daocheng rock body belongs to the high-potassium calc-alkaline series, with peraluminous characteristics, and the Haizishan rock body is a high-potassium calc-alkaline-potash series, which is also peraluminous. According to zirconium saturation concentration thermometer and rare earth element saturation concentration thermometer, the average upper limit temperature of magma formation is 783 鈩，
本文编号：2123908
[Abstract]:Yidun island arc is a Triassic volcanic island arc between Songpan-Ganzi fold belt and Qiangtang terrane. The Daocheng and Haizishan intrusions are late Triassic and Cretaceous granitic rocks respectively. Combined with rock geochemistry, polarizing microscope and electron probe (EPMA) and scanning electron microscope (SEM), a systematic mineralogical study of the rock mass was carried out. The results show that the major rock-forming minerals of the two bodies are plagioclase (mesopaglitic feldspar), potash feldspar (orthoclase), quartz and biotite (Ironite-ferric biotite), and accessory minerals such as zircon, sphene, magnetite and apatite. The composition of biotite indicates that the source regions of the two rocks are crust-mantle mixing. The Daocheng rock body belongs to the high-potassium calc-alkaline series, with peraluminous characteristics, and the Haizishan rock body is a high-potassium calc-alkaline-potash series, which is also peraluminous. According to zirconium saturation concentration thermometer and rare earth element saturation concentration thermometer, the average upper limit temperature of magma formation is 783 鈩，
本文编号：2123908
本文链接：https://www.wllwen.com/kejilunwen/diqiudizhi/2123908.html
