Study On Geology And Geochemistry Of The Permian Granite In Bolihujing, Inner Mongolia

According to the field geological research and analysis data in door, on the basisof geological characteristics by Permian granite of Bolihujing area in Inner Mongolia,China, by studying the petrochemistry of granite and the geochemistry of major andtrace elements, the genesis of rock mass and structural setting, etc. can be explored.The research results are:1. According to the geochemistry of major elements, the Permian granites ofstudy area show the characteristics by the high alkalinity of potassium and calcium,they are mainly metaluminous~peraluminous.2. The trace elements appear the concentration of large-ion lithophile elementslike Rb, Ba, Th, K and so on. The rare earth elements distribution mode curve shows aLREE pattern which slightly and smoothly leans to the right. The δEu of most rocksappear not obvious or weak negative abnormal characteristics except the δEu ofmuscovite-granite.3. To a certain extent, the biotite-granites of study area have similar traceelement and REE patterns, which may be the results of the comagmatic differentiationand evolution.4. Most of the Permian biotite-granite type (Pγβ1、Pγβ2、Pγβ3) in Bolihujingarea shows the characteristics by high silicon (SiO2=71.45-79.67%), low aluminum(Al2O3=10.59-13.93%), rich alkali (Na2O+K2O=7.3-9.36%), metaluminous-weakaluminous (A/CNK=0.93-1.01), and the strong enrichment of large-ion lithophileelements like Rb, Ba, Th, K. The rare earth elements distribution mode curve shows aright-leaning sea gull type. The geochemistry demonstrates that the Permianbiotite-granite is A-type granite. The muscovite-granite has a low content of SiO2(71.81-72.51%), a high content of aluminum (Al2O3=14.55-15.27%), and theA/CNK=1.06-1.28＞1.1, meaning that it belongs to the aluminous granite with a nottoo deep source magma. The original rock may be sedimentary or metasedimentaryrock. These features indicate that the Permian muscovite-granite in Bolihujing areabelongs to S-type granite. This also coincides with the stratum conditions of the studyarea. The granite is mainly emplaced in a set of shallow metamorphic strata most ofwhose composition is schist of Late Proterozoic. 5. The structural setting discriminant analysis of granite type in Bolihujing areareflects that the biotite-granite has characteristics of syn-collisional granite in this area.And more, the high alkalinity of potassium and calcium of biotite-granite, the regionallarge-scale magma emplacement and strong fold orogenic movement all shows thecharacteristic of syn-collision. The muscovite-granite belongs to volcanic arc granite.To sum up, most granite in study area formed in the syn-collision structural setting,belonging to post-orogenic granite, its formation is closely related to the regionallarge-scale orogenic movement.