论文部分内容阅读
对额尔古纳地块新元古代花岗岩进行了锆石LA-ICP-MS U-Pb年代学、岩石地球化学和锆石Hf同位素研究,以便对其新元古代岩浆作用历史与微陆块构造属性给予制约.所测花岗质岩石中锆石的CL图像特征和Th/U比值(0.17~1.46)显示其为岩浆成因.测年结果并结合前人定年结果,可以判定额尔古纳地块上至少存在~929Ma、~887Ma、~850Ma、~819Ma、~792Ma、~764Ma和~738Ma岩浆事件.岩石地球化学特征显示,~887Ma花岗岩为一套后碰撞花岗岩类;而850~737Ma花岗质岩石整体上属于A-型花岗岩,也有部分岩体(漠河、阿木尔、碧水和室韦岩体)显示I-型花岗岩特征.锆石Hf同位素特征反映这些花岗岩的源区既有中-新元古代(TDM2=884~1 563Ma)新增生地壳物质的部分熔融,同时伴有少量古老地壳物质的混染,也有残留的古老中基性下地壳物质的部分熔融.综合研究区新元古代侵入岩的地球化学特征,同时对比新元古代全球构造热事件,认为额尔古纳地块上新元古代岩浆活动记录了Rodinia超大陆形成和演化过程中的地壳响应:927~880Ma的岩浆作用应是Rodinia超大陆汇聚造山的产物;而850~737Ma的岩浆作用应是对Rodinia超大陆快速裂解的记录.通过岩浆事件对比发现,额尔古纳地块与邻近的西伯利亚南缘微陆块(如中蒙古地块和图瓦地块)具有亲缘性,而与塔里木板块和华南板块至少在新元古代岩浆活动上具有一定的相似性,而明显区别于华北板块和西伯利亚板块.
The zircon Neolithic LA-ICP-MS dating of U-Pb, lithogeochemistry and zircon Hf isotopes were studied for the Neoproterozoic granite in the Erguna Block in order to analyze the Neoproterozoic magmatic history and micro-continental block structure The CL images and the Th / U ratio (0.17-1.46) of the zircons in the granitic rocks show that they are magmatic origin.According to the dating results and the predecessors’ dating results, it can be concluded that the Ergun area There are at least ~ 929Ma, ~ 887Ma, ~ 850Ma, ~ 819Ma, ~ 792Ma, ~ 764Ma and ~ 738Ma magmatic events on the blocks. The geochemical characteristics of the rocks show that the ~ 887Ma granitoids are a set of post-collisional granites; while the granites of 850 ~ 737Ma The granitic rocks are generally A-type granites, and some of the rocks (Mohe, Amur, clear water and volcanic rocks) show the characteristics of I-type granites. The Hf isotopic characteristics of zircons reflect that these granites have both source- In ancient times (TDM2 = 884-1 563Ma), some newly-formed crustal materials were partially melted, accompanied by the contamination of a few ancient crustal materials and partial melting of the remnant ancient middle-basic lower crustal materials. Rock geochemical characteristics, while contrasting Neoproterozoic On the global tectono-thermal event, it is considered that the Neoproterozoic magmatism on the Erguna block records the crustal response during the formation and evolution of the Rodinia supercontinent: the magmatic activity of 927-880 Ma should be the product of the convergence orogeny of the Rodinia supercontinent; The magmatic activity of 850-737 Ma should be a record of rapid pyrolysis of the Rodinia supercontinent.Comparing magmatic events, it is found that the Erguna and the adjacent micro-continental blocks in the southern margin of Siberia, such as the middle Mongolia block and Tuwa block, It is related to the Tarim and South China plates at least in the Neoproterozoic magmatism, but distinctly different from the North China plate and Siberia plate.