额尔古纳地块玻乌勒山地区新元古代斜长角闪岩-片麻状花岗岩的成因及其地质意义

发布时间：2018-08-24 08:44

【摘要】：对大兴安岭北段额尔古纳地块东南缘玻乌勒山地区新元古代斜长角闪岩和片麻状花岗岩进行了LA-ICP-MS锆石UPb定年和岩石地球化学分析,讨论额尔古纳地块的演化及其与Rodinia超大陆聚合事件的关系。斜长角闪岩的锆石阴极发光图像显示核边结构,获得核部年龄904±4Ma和边部年龄803~886Ma;片麻状花岗岩的锆石呈自形-半自形,发育岩浆成因的振荡环带,U-Pb年龄为915±3Ma,表明其形成于新元古代。片麻状花岗岩SiO_2=61.85%~67.63%,Mg~#=36.9-47.9,Na_2O+K_2O=4.21%~9.29%,A/CNK=0.89~1.01,属于偏铝质系列。岩石富集轻稀土元素和大离子亲石元素,亏损高场强元素Nb、Ta和Ti,具弱的Eu负异常、低的初始Sr比值和正的ε_(Nd)(t)值,暗示片麻状花岗岩为年轻的初生地壳物质熔融形成。斜长角闪岩贫硅、Mg~#较高,Ni、Cr、Co含量较高,Zr/Hf、Nb/Ta和Th/U值低,具有平坦的稀土元素配分模式,与正常型洋中脊玄武岩相似,具有亏损地幔性质,同时富集大离子亲石元素Rb、Ba、K、Sr和Pb,亏损高场强元素Nb、Ta、Ti等,记录了消减带岩浆作用的信息,表明其为活动大陆边缘经过岛弧岩浆抽提的亏损地幔源区发生重新熔融形成。结合区域上新元古代岩浆事件的纪录,认为额尔古纳地块新元古代早期岩浆事件是Rodinia超大陆聚合事件的响应,后期变质事件可能与Rodinia超大陆裂解有关。
[Abstract]:The LA-ICP-MS zircon UPb dating and petrogeochemical analysis of the Neoproterozoic amphibolite and schneiss granites in the Boulle Mountain area of the southeastern margin of the Ergna block in the northern part of the Daxinganling Mountains have been carried out by means of LA-ICP-MS zircon UPb dating and geochemistry analysis. The evolution of the Erguna massif and its relationship with Rodinia supercontinental aggregation events are discussed. The zircon cathodoluminescence images of the amphibolite show that the nuclear age is 904 卤4Ma and the edge age is 803 ~ 886 Ma. The zircon of the granitic granites appears to be automorphic to semiautomorphism. The U-Pb age of the oscillating ring zone of magma genesis is 915 卤3 Ma. which indicates that it was formed in Neoproterozoic. The granitic granite, SiO_2=61.85%~67.63%,Mg~#=36.9-47.9,Na_2O K _ 2O _ 4. 21, belongs to the metaluminite series. The rocks are enriched with light rare earth elements and large ion lithophile elements, and the depleted high field strength elements Nb,Ta and Ti, have weak Eu negative anomalies, low initial Sr ratios and positive 蔚 _ (Nd) (t) values, implying that the granitic granites are formed by the melting of young primary crustal materials. The amphibolite is rich in silicon and high in mg ~ (+) ~ (2 +). The content of Ni ~ (2 +) Cr ~ (2 +) is higher, and the values of NB / Ta and Th/U are low. The amphibolite has a flat REE distribution pattern, which is similar to the normal type of mid-oceanic ridge basalt, and has the property of depleted mantle. At the same time, the enrichment of the large ion lithophile element Rb,Ba,K,Sr and the Pb, depleted high field strength element Nb,Ta,Ti etc. recorded the information of subduction zone magmatism, indicating that the depleted mantle source extracted by island arc magma from the active continental margin was remelted. Based on the regional records of Neoproterozoic magma events, it is considered that the early Neoproterozoic magmatic events in the Erguna massif are the response of the Rodinia supercontinent aggregation events, and the late metamorphic events may be related to the Rodinia supercontinent fragmentation.
【作者单位】：武警黄金第三支队;
【基金】：中国地质调查局项目《黑龙江1∶5万碧州公社、大乌苏、玻乌勒山、沙兰山幅区域地质矿产调查》(编号:1212011220666)
【分类号】：P534.3;P588.3

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