祁连地块西段硫磺矿北花岗闪长岩的岩石成因及其地质意义:年代学、地球化学及Hf同位素证据

发布时间：2018-12-13 04:34

【摘要】：祁连地区与Rodinia超大陆汇聚有关的新元古代岩浆活动越来越受到地质学者的关注和研究.对硫磺矿北花岗闪长岩体进行了锆石LA-ICP-MS U-Pb定年,结果显示岩体锆石U-Pb年龄加权平均值为926±4Ma,表明其形成时代新元古代早期.花岗闪长岩的SiO_2为59.47%~62.96%,P2O5为0.12%~0.14%,铝饱和指数(A/CNK)为1.01~1.15,主要为一套弱过铝质的高钾钙碱型系列,具I型花岗岩的特征.稀土元素总量在118.80×10-6~253.07×10-6之间,(La/Yb)N为7.87~16.17,明显富集轻稀土,具有中等-强Eu负异常(δEu=0.33~0.68),稀土元素配分图呈右倾型特征;微量元素上具有富集大离子亲石元素和不相容元素(Rb、Th和U),亏损高场强元素Nb、Ta、Ti、Sr和P的特征;Nb/Ta、La/Nb、Nb/U及Sm/Nd比值整体反映花岗闪长岩壳源特点;硫磺矿北花岗闪长岩体εHf(t)主要在0~7之间,二阶段地壳模式年龄主要在1 247~1 801Ma之间.结合区域新元古代岩浆活动认为硫磺矿北花岗闪长岩体形成于活动大陆边缘,而硫磺矿北花岗闪长岩为中元古代增生的年轻地壳部分熔融的产物,经历一定程度分离结晶,可能也有古老地壳部分熔融成分参与该岩体形成.同时,该时期岩浆活动可能为祁连地块在中新元古代时期对全球Rodinia超大陆聚合事件的响应,进一步为祁连地块属性提供可信研究资料.
[Abstract]:Neoproterozoic magmatic activity related to Rodinia supercontinent convergence in Qilian area has been paid more and more attention to by geologists. The zircon LA-ICP-MS U-Pb dating of the granodiorite in the north of sulfur ore deposit is carried out. The results show that the weighted mean value of zircon U-Pb age is 926 卤4 Ma. which indicates that it was formed in the early Neoproterozoic. The SiO_2 of granodiorite is 59.47 and P _ 2O _ 5 is 0.12 and 0.14, and the aluminum saturation index (A/CNK) is 1.01 ~ 1.15, which is mainly a set of weak peraluminous high-potassium calc-alkali series, characterized by I-type granite. The total amount of rare earth elements is between 118.80 脳 10 ~ (-6) and 253.07 脳 10 ~ (-6), and (La/Yb) N is 7.87 ~ (16. 17). The rare earth elements are obviously enriched in light rare earth elements, with moderate to strong Eu negative anomaly (未 Eu=0.33~0.68), and the REE distribution pattern is right-tilted. The trace elements are characterized by enrichment of large ion lithophile elements and incompatible elements (Rb,Th and U), depleted high field strength elements Nb,Ta,Ti,Sr and P). The ratios of Nb/Ta,La/Nb,Nb/U and Sm/Nd reflect the characteristics of granodiorite crust, the 蔚 Hf (t) of the northern granodiorite is between 0 and 7, and the age of the two-stage crustal model is between 1 247 and 1 801Ma. Combined with the regional Neoproterozoic magmatic activity, the northern granodiorite of sulfur ore was formed on the active continental margin, while the north granodiorite of sulfur ore was the product of partial melting of the young crust of Mesoproterozoic accretion, and experienced some degree of separation and crystallization. It may also be that some melting elements of the ancient crust are involved in the formation of the rock mass. At the same time, the magmatic activity in this period may be the response of Qilian massif to the global Rodinia supercontinent aggregation event during the Meso-Neoproterozoic period, and further provide credible research data for the attributes of the Qilian block.
【作者单位】：成都理工大学沉积地质研究院;油气藏地质及开发工程国家重点实验室;
【基金】：冈底斯-喜马拉雅铜矿资源基地调查项目(No.DD20160015) 中国地质调查项目(No.12120113033004) 高等学校博士学科点专项科研基金资助项目(No.20125122110010)
【分类号】：P588.12

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