【摘要】 内蒙古乌兰浩特地区出露的2条花岗斑岩带分布在与嫩江—八里罕断裂相关的左行走滑剪切带内。通过LA-ICP-MS锆石U-Pb年代学研究,确定该花岗斑岩的形成时代为124.99±0.99 Ma,属于早白垩世晚期。地球化学特征表明,该花岗斑岩SiO₂含量为70.56%～78.34%,（Na₂O+K₂O）为7.10%～8.99%,铝饱和指数A/CNK为0.94～1.20,富硅、碱,属于准铝质-过铝质花岗岩。花岗斑岩稀土元素总量中等,轻、重稀土元素分馏明显（（La/Yb）_N=9.49～14.71）,Eu负异常较强（δEu=0.33～0.73）,相对富集大离子亲石元素Rb、Ba和高场强元素Th、U,Sr、Nb、Ti相对亏损,呈明显负异常,属于高分异I型花岗岩。嫩江—八里罕断裂在早白垩世晚期曾发生短暂的伸展作用。更多还原

【Abstract】 Two granitic porphyry belts outcropped in the Ulanhot area, Inner Mongolia, occur mainly in the sinistral strike-slip shear zone related to the Nenjiang-Balihan fault. LA-ICP-MS zircon U-Pb dating shows that granitic porphyry formed at 124.99±0.99 Ma, which belongs to the late Early Cretaceous. Geochemical characteristics show that the granitic porphyry has SiO₂content of 70.56%～78.34% and（Na₂O+K₂O）content of 7.10%～8.99%, with A/CNK ratio of 0.94～1.20, and enrichment in Si and alkaline suggests that it belongs to subluminous-peraluminous granite. Granitic porphyry is characterized by medium REE contents, distinct fractionation of LREE and HREE（（La/Yb）_N=9.49～14.71）, strong negative Eu anomaly（δEu=0.33～0.73）, relative enrichment of large ion lithophile elements（Rb and Ba） and of high field strength-elements（Th and U）, but relative depletion of Sr, Nb and Ti, with distinct negative anomaly, suggesting that it belongs to highly fractionated I-type granite. It can be concluded in this study that the Nenjiang-Balihan fault in the Ulanhot area experienced a short-period extension in the late Early Cretaceous.更多还原