大别造山带宿松群锆石U-Pb年龄和Nd同位素组成：物源和地壳演化

发布时间：2018-04-24 11:54

本文选题：宿松群 + 新元古代　；参考：《中国科学技术大学》2015年硕士论文

【摘要】：宿松群位于扬子板块北缘大别山南麓地区,北面与南大别低温榴辉岩带毗邻被太湖马庙断裂带所分割,南面以襄樊-广济断裂带为界。宿松群形成于新元古代大致时间为750Ma前后,跟825～740Ma罗迪尼亚超大陆裂解在扬子板块引发的陆内裂谷作用有关,期间伴随弧后盆地的形成,并经历后期的沉积作用。宿松群岩石类型复杂总的来说主要由变沉积岩和变岩浆岩两大类岩石组成,其物源组成比较复杂。本次研究选取了宿松变质地体的片岩、片麻岩、变花岗岩和变基性岩样品,对其进行了锆石U-Pb定年,锆石REE,全岩主微量元素和全岩Nd同位素组成的分析。对片岩JH-13-02碎屑锆石U-Pb年龄范围在2836Ma到1532Ma,主要集中在2500Ma附近,片岩JH-13-03碎屑锆石U-Pb年龄范围在2424Ma到1069Ma,主要集中在2000Ma附近。变花岗岩JH-13-05加权平均年龄为754±15Ma,片麻岩JH-13-06年龄主要集中在767±18Ma,所有样品的锆石Th/U大于0.1可见到清晰的岩浆振荡环带显示典型的岩浆锆石成因特征,锆石亏损LREE富集HREE,并且具有不同程度Ce的正异常和Eu的负异常。全岩主量元素特征；片岩具有较高的A1203和Na K含量,片岩SiO2含量57.2%-77.1%。变基性岩SiO2含量在45.6%-50.8%。全岩REE特征显示富集LREE亏损HREE,片岩和片麻岩具有Eu的不同程度负异常,变基性岩LREE和HREE分异较低不具有Eu的异常。片岩和片麻岩微量元素特征；富集大离子亲石元素Rh、Th、Ba亏损Nb、Sr元素。变基性岩也富集大离子亲石元素,Nb、Sr亏损不明显。片岩和片麻岩的初始εNd值变化在-12.0至-2.8之间,Nd模式年龄TDM为1.6-3.1Ga,变基性岩初始εNd值变化在-9.3到1.9,TDM范围是1.6到2.1Ga。相比海州群云母片岩初始εNd值-2.8到-8.8,TDM为2.1-2.4Ga较为单一的沉积物源,宿松群物源复杂。
[Abstract]:Susong Group is located at the southern foot of Dabie Mountain on the northern margin of the Yangtze Plate. It is adjacent to the southern Dabie cryogenic eclogite belt by the Mamiao fault zone of Taihu Lake and is bounded by the Xiangfan-Guangji fault zone in the south. The Suzong group was formed in the Neoproterozoic around 750Ma, which is related to the intracontinental rift caused by the breakup of the 825~740Ma Rodinia supercontinent in the Yangtze plate, which was accompanied by the formation of the back-arc basin and experienced late sedimentation. The complex rock types of Suzong Group are mainly composed of two types of rocks: metamorphic and metamorphic rocks, and their provenance composition is quite complex. In this study, samples of schist, gneiss, metamorphic granite and metamorphic rocks from the Suzong metamorphic terrane were selected and their zircon U-Pb dating, zircon REE, main trace elements and ND isotopic compositions of the whole rock were analyzed. For schist JH-13-02 zircon, the U-Pb age range is from 2836Ma to 1532 Ma, mainly in the vicinity of 2500Ma, and the U-Pb age range of schist JH-13-03 detrital zircon is from 2424Ma to 1069 Ma, mainly in the vicinity of 2000Ma. The JH-13-05 weighted average age of metamorphic granite is 754 卤15Ma.The JH-13-06 age of gneiss is mainly 767 卤18Ma.The zircon Th/U of all samples is greater than 0.1.A clear magmatic oscillation ring shows typical magmatic zircon genesis. Zircon depleted LREE enriches HREE and has positive and negative ce anomalies to varying degrees. The schist has a high content of A1203 and Na K, while the SiO2 content of schist is 57.2-77.1. The SiO2 content of the altered basic rock is between 45.6 and 50.8. The REE characteristics of the whole rock show that the enrichment of LREE depleted hree, the schist and gneiss have negative EU anomalies to varying degrees, and the lower differentiation of LREE and HREE in metamorphic rocks does not have EU anomalies. The microelement characteristics of schist and gneiss are characterized by the enrichment of large ion lithophile element Rhnb Th Ba and depletion of NB + Sr element. Metamorphic rocks are also enriched in large ion lithophile elements, and the depletion of NB ~ (2 +) Sr is not obvious. The initial 蔚 ND values of schist and gneiss vary from -12.0 to -2.8 TDM is 1.6-3.1Ga. the initial 蔚 ND values of basic rocks range from -9.3 to 1.9 ~ 1.1Ga. Compared with the initial 蔚 ND values from -2.8 to -8.8 of mica schist in Haizhou Group, TDM is a single sediment source of 2.1-2.4Ga, and the provenance of Susong Group is complex.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P597;P313

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