政和—大埔断裂带内基性—超基性岩成因及构造属性研究

发布时间：2018-09-04 19:31

【摘要】：NE-SW向政和-大埔断裂带是华夏板块内部一条重要的断裂带,该带内出露大量基性-超基性岩,前人对于该带内基性-超基性岩的认识一直以来存在争议。本论文主要针对该断裂带政和-建瓯段基性-超基性岩开展锆石U-Pb年代学及地球化学分析,意在厘清基性-超基性岩成因及构造属性,并以此探讨华夏板块新元古代—早古生代构造演化。通过以上研究,本文取得以下主要认识:锆石U-Pb定年显示,政和-大埔断裂带内基性岩大多形成于新元古代,其中水吉镇双峰式火山岩角闪斜长片岩原岩形成年龄分别为812±7 Ma,政和斜长角闪片岩原岩形成时代725±22 Ma。地球化学特征表明迪口镇角闪片岩原岩岩浆来源于富集型地幔,政和斜长角闪岩岩浆来源于相对亏损的地幔,构造判别图解上前者为板内玄武岩,后者具有N-MORB特征。电子探针数据表明洋后角闪石岩主要为浅闪石,Re-Os同位素和Sr-Nd同位素特征显示洋后角闪石岩原岩为岩浆成因,岩浆来源于富集型地幔,而马面山蛇纹岩和北历蛇纹石化橄榄岩为大陆岩石圈残余地幔橄榄岩。综和上述特征政和—大埔断裂带内基性岩形成于新元古代拉张构造环境,而超镁铁质岩石有的为岩浆成因,有的为残余的地幔橄榄岩,但其是否为蛇绿岩套还需做进一步研究。沿政和-大埔断裂带内也出露一些中生代的基性岩。锆石U-Pb定年显示东游镇斜长角闪片岩原岩形成年龄为221±1 Ma。Sr-Nd同位素表明东游镇斜长角闪片岩岩浆来源于富集型地幔,构造判别图解上岩石属于板内拉斑玄武岩。
[Abstract]:The NE-SW Xiangzheng-Tai Po fault zone is an important fault zone in the Huaxia plate, in which a large number of basic-ultrabasic rocks are exposed. In this paper, zircon U-Pb geochronology and geochemistry analysis are carried out for the basic-ultrabasic rocks of Zhenghe and Jianou member of the fault zone, in order to clarify the genesis and tectonic attributes of basic-ultrabasic rocks. The tectonic evolution of Neoproterozoic-early Paleozoic in the Huaxia plate is discussed. Based on the above study, the main conclusions are as follows: the zircon U-Pb dating shows that most of the basic rocks in the Zhenghe-Tai Po fault zone were formed in the Neoproterozoic. The age of formation of the amphibolite schist in Shuiji town is 812 卤7 Ma, and 725 卤22 Ma., respectively. The geochemical characteristics indicate that the magma of Dikouzhen hornblende schist originates from the enriched mantle, the Zhenghe and plagioclase amphibolite magma from the relatively depleted mantle. The former belongs to intraplate basalt and the latter is characterized by N-MORB. The electron microprobe data show that the post-oceanic hornblende is mainly composed of shallow-amphibole Re-Os isotopic and Sr-Nd isotopic features, indicating that the post-oceanic hornblende originates from magma, and the magma originates from the enriched mantle. The Mamanshan ophiolite and the northern serpentine peridotite are residual mantle peridotite in the continental lithosphere. The basic rocks in the Zhenghe-Tai Po fault zone were formed in the Neoproterozoic extensional tectonic environment, while the ultramafic rocks were either magmatic or residual mantle peridotite, but whether they are ophiolite suites should be further studied. Some Mesozoic basic rocks were also exposed along the Zhenghe-Tai Po fault zone. The zircon U-Pb dating shows that the age of formation of the amphibole schist is 221 卤1 Ma.Sr-Nd isotope, indicating that the magma of Dongyou Zhen clinopodiorite schist originated from the enriched mantle, and the tectonic discrimination diagram shows that the rocks belong to intraplate tholeiite basalt.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P588.12;P542

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