胶东昌邑地区古元古代二长花岗岩锆石U-Pb定年、Hf同位素组成及其构造岩浆演化意义

发布时间：2018-10-19 19:35

【摘要】：胶东地区位于古元古代胶-辽-吉带的南段,前人对该区的早前寒武纪地质事件进行了较多研究,然而,对古元古代侵入岩则缺乏深入研究。本文在对昌邑地区古元古代二长花岗岩进行了详细野外调查的基础上,通过对其岩石地球化学、锆石U-Pb定年及Hf同位素分析,讨论了花岗岩的成因和形成时代,以及与之相关的粉子山群的沉积时代。本文研究的二长花岗岩具高的全碱含量(K2O+Na2O=6.93%~8.11%),低的Al2O3(9.89%~14.11%),低Mg O(0.01%~0.63%),为偏铝质岩石(铝饱和指数A/CNK为0.99~1.56)。明显亏损Nb、Ta、P、Ti等高场强元素,轻重稀土分馏程度较高。5个样品的锆石LA-MC-ICP-MS和1个SHRIMP定年,形成年龄为2045±8~2187±9 Ma,指示花岗岩形成于古元古代。侵入粉子山群的细粒二长花岗岩的锆石年龄为2080±9Ma,结合前人研究成果,认为粉子山群小宋组的沉积时间限于2.1~2.2 Ga之间。据岩石地球化学和岩浆锆石Hf同位素组成特征表明,二长花岗岩形成于上地壳物质不同程度部分熔融,这得到~2.4 Ga和~2.7 Ga继承锆石存在的支持,较古老地壳物质为新太古代早期TTG岩石。
[Abstract]:The Jiaodong area is located in the southern section of the ancient Jiao Liao-Ji belt of Gu Yuan. The early Precambrian geological events in this area have been studied by predecessors, but the paleoproterozoic intrusive rocks have not been studied in depth. Based on the detailed field investigation of Gu Yuan's ancient monzogranites in Changyi area, the origin and age of the granites are discussed by means of geochemistry, zircon U-Pb dating and Hf isotopic analysis. And the related sedimentary age of the Fangzishan Group. The monzogranites studied in this paper have high total alkali content (K _ 2O Na2O=6.93%~8.11%), low Al2O3 (9.89%) and low Mg O (_ (0.01) 0.63%, which are metaluminous rocks (A/CNK = 0.991.56). The zircon LA-MC-ICP-MS and 1 SHRIMP dating of 5 samples indicate that the granite was formed in ancient Gu Yuan with an age of 2045 卤80.187 卤9 Ma,. The zircon age of the fine-grained monzogranite intruded into the Fangzishan Group is 2080 卤9 Ma. combined with the previous research results, it is considered that the sedimentary time of the Xiaosong formation of the Fangzishan Group is only between 2.1 and 2.2 Ga. According to the characteristics of rock geochemistry and Hf isotopic composition of magmatic zircon, it is shown that the monzonitic granites were formed in different degrees of partial melting of the upper crust material, which is supported by the existence of ~ 2.4 Ga and ~ 2.7 Ga inherited zircon. The older crustal material is the early NeoArchean TTG rock.
【作者单位】：国土资源部金矿成矿过程与资源利用重点实验室山东省金属矿产成矿地质过程与资源利用重点实验室;山东省地质调查院;中国地质调查局天津地质调查中心;中钢集团天津地质研究院有限公司;
【基金】：国家公益性行业性专项(201511029) 国家自然科学基金项目(编号:41672084;41503038;41772076) 中国地质调查局项目(编号:1212011220485;1212010811029;12120114034901)联合资助
【分类号】：P588.121

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