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对大兴安岭中部济沁河林场地区晶洞二长花岗岩进行了锆石U-Pb同位素年代学及地球化学研究,并对其成岩时代、成因及构造意义进行讨论.从阴极发光图像上来看,该晶洞二长花岗中锆石具有典型岩浆成因的振荡生长环带,高Th/U比值也印证了其岩浆成因.LA-ICP-MS锆石U-Pb定年结果显示,岩体形成于113.1~115.1 Ma的早白垩世晚期.二长花岗岩具有高硅、富碱的特征,Eu异常较小,弱过铝质,富集U、Th,强烈亏损P和Ti,微量元素中富集Rb、Th、La、Zr、Hf,而亏损Ba、Sr、P、Ti.上述特征表明晶洞花岗岩是高分异的I型花岗岩,其形成于华北板块、西伯利亚板块、北美板块和古太平洋板块四者汇聚之后的后碰撞伸展构造环境.
The zircon U-Pb isotopic geochronology and geochemistry of the Jingtong gneissic granite in the Jiuxinhe forest farm area in the central part of the Greater Xing’an Mountains were discussed, and its diagenetic age, genesis and tectonic significance were discussed.From the cathodoluminescence image, The zircons from the Dongchangchang granitoid have typical magmatic origin, and the high Th / U ratio also confirms the magmatic origin.The zircon U-Pb dating of LA-ICP-MS shows that the rock mass formed at 113.1 ~ The late Early Cretaceous of 115.1 Ma shows that the monzonitic granite is characterized by high silicon and alkali-rich. Eu is less anomalous and weakly peraluminous, enriched in U and Th, strongly depleted in P and Ti, enriched in trace elements such as Rb, Th , La, Zr, Hf, and depletion of Ba, Sr, P, Ti. The above characteristics indicate that the granodiorite is a high-grade I-type granite that formed in the convergence of the North China plate, the Siberia plate, the North America plate and the Paleo- Pacific plate After the collision extended structural environment.