内蒙古西乌旗石匠山A型花岗岩位于贺根山缝合带内,侵位于早石炭世迪彦庙-白音布拉格蛇绿岩带和下二叠统寿山沟组与大石寨组中,岩性为二长花岗岩.石匠山A型花岗岩富硅(SiO2=74.18%~77.16%)、富钾(K2O=4.31%~5.07%)、富碱(Na2O+K2O=8.44%~9.16%),贫Al2O3、CaO、MgO、TiO2、P2O5、Sr、Ba、Eu、Ti和P,具有较高的Ga/Al(3.98~6.09)、(Na2O+K2O)/CaO、K2O/MgO、TFeO/MgO、Rb/Nb、Y/Nb、Sc/Nb值,稀土元素配分曲线为典型的海鸥式分布,δEu为0.01~0.19,负Eu异常显著,明显不同于I、S和M型花岗岩,为典型的铝质A型花岗岩.在地球化学分类判别图解上,石匠山A型花岗岩显示A2型后造山铝质花岗岩特征,反映其形成于后造山伸展环境.LA-ICP-MS锆石U-Pb测年结果表明,该花岗岩的侵位年龄为159.8±1.3Ma、143.1±1.3Ma、136.20±0.69Ma,即形成时代为晚侏罗世—早白垩世,揭示贺根山缝合带在晚侏罗世—早白垩世为后造山伸展阶段.%Lying along the Hegenshan collisional orogenic suture zone in Xi Ujimqin Banner of Inner Mongolia,the Shijiangshan A-type granite intruded into Early Carboniferous Diyanmiao-Baiyinbulage ophiolite as well as Early Permian Shoushangou Formation and Dashizhai Formation, and consists mainly of monzogranites. The granite is geochemically characterized by high SiO2(74.18%~77.16%),K2O(4.31%~5.07%),high absolute alkali values(Na2O+K2O=8.44%~9.16%),low Al2O3,CaO,MgO,TiO2,P2O5,Sr,Ba, Eu, Ti, P values, and higher Ga/Al (3.98~6.09), (Na2O+K2O)/CaO, K2O/MgO, TFeO/MgO, Rb/Nb, Y/Nb, Sc/Nb ratios. It is characterized by typical flat or slight right-inclined gull-wing shaped REE distribution patterns with obvious negative Eu anomalies (δEu=0.01~0.19). The Shijiangshan monzogranite exhibits typical geochemical characteristics of A-type granite, being significantly different from I,S and M type granites in geochemistry.According to the chemical subdivision diagrams of the A-type granitoids,the Shijiangshan A-type granite belongs to aluminous A2-type granitoid,formed and emplaced in a post-orogenic extension setting.LA-ICP-MS zircon U-Pb dating shows that the ages of the granite are 159.8±1.3Ma, 143.1±1.3Ma and 136.20±0.69Ma, suggesting that it was produced during Late Jurassic to Early Cretaceous and that the Hegenshan suture zone was at the post orogenic extension stage in the Late Jurassic-Early Cretaceous period.
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