宝兴岩体位于华北板块北缘陆缘活动带东段,岩性为花岗闪长岩,LA-ICP-MS锆石206Pb/238U年龄加权平均值为235.0±1.3Ma,属于中三叠世.岩石的K2O/Na2O平均值为1.07,属高钾钙碱性系列;富集大离子亲石元素,亏损高场强元素,具有活动陆缘钙碱性岩系特征;稀土元素总量平均值为147×10-6,稀土元素配分曲线右倾,属具中等负Eu异常的轻稀土元素富集、重稀土元素亏损型.通过岩石学、岩石地球化学及年代学研究,结合邻区构造演化研究,认为中三叠世研究区在伸展作用下岩石圈进行拆沉,从而形成大规模的岩浆活动.%Located on the northern margin of North China Block, the Baoxing rock mass is mainly composed of granodiorite. Ac-cording to LA-ICP-MS zircon U-Pb dating, it was formed in Middle Triassic, with the 206Pb/238U age of 235.0±1.3Ma. The aver-age K2O/Na2O ratio is 1.07, indicating that the rocks belong to high-K calc-alkaline series. The rocks are enriched in LILE and de-pleted in HFSE, showing typical features of calc-alkaline series on an active continental margin. The average total amount of REE is 147×10-6, and the curve exhibits obvious right-inclined feature on REE distribution pattern, suggesting that the rocks are of the type of LREE enrichment and HREE depletion with medium negative Eu anomaly. According to the petrology, geochemistry and geo-chronology in combination with the tectonic evolution research on adjacent areas, lithospheric delamination occurred under the ex-tension in the study area, and then caused a large-scale magmatic activity in the Middle Triassic.
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