青海省循化道帏地区变质火山岩地质特征及构造属性研究
发布时间：2019-02-21 20:07
【摘要】：青海省循化道帷地区物质组成和地壳结构十分复杂,构造演化历史悠久,存在多条NWW向、NW-NNW向断裂,其中在南部发育的金库街-多支坝斜冲断层(区域上称为隆务河-大夏河断裂),构成了北侧祁连造山带中化隆微地块和拉脊山构造带与南侧西秦岭造山带北缘构造带之间的分界断裂。本文选取青海省循化地区出露的不同变质程度的火山岩为研究对象,通过野外地质调查和岩石学、矿物学、岩石地球化学及同位素年代学等方面的综合研究,获得如下成果和认识:(1)青海省循化地区出露的化隆岩群主要由斜长角闪岩和少量变粒岩组成,其变质程度可达中低角闪岩相,通过角闪石-斜长石变质温压计,获得其变质温度约达691~772℃,变质压力约0.39~0.64GPa。化隆岩群岩石地球化学数据反映,斜长角闪岩原岩为玄武岩,变粒岩原岩为安山岩,该套变质火山岩形成环境为弧后盆地环境。从化隆岩群斜长角闪岩中获得锆石U-Pb年龄指示化隆岩群形成年龄为(1852±18)Ma,确定其原岩形成时代为古元古代。(2)在青海省循化地区北侧出露的深沟组主要为变安山岩夹变玄武岩组合。该套变玄武岩主要由富集地幔分离结晶形成,变安山岩可能由地壳部分熔融形成,该套变火山岩形成于裂谷环境。获得变玄武岩锆石U-Pb年龄为(503.1±6.6)Ma,指示深沟组形成于中寒武世。这些特征指示了拉脊山构造带在中寒武世处于裂谷早期阶段。(3)在青海省循化地区北东侧出露的晚寒武世六道沟组主要为变玄武岩夹变安山岩组合。该套变火山岩组合具有E-MORB特征,其形成环境为裂谷环境。其变玄武岩野外产出具有变余枕状构造,且其由富集地幔分离结晶的岩石成因,暗示在拉脊山构造带在晚寒武世处于裂谷晚期阶段。(4)拉脊山构造带地区自早中寒武世以来,在南祁连洋向北俯冲消减、板片回转的地球动力学背景下,中祁连地块可能受到软流圈地幔上涌并引起大陆拉张裂解,形成了裂谷型中基性火山岩组合。在持续的俯冲作用下,南祁连洋部分洋壳岩块及洋岛/海山岩块逐一向北拼贴于中祁连地块,由于俯冲持续的应力挤压导致拉脊山大陆裂谷关闭。
[Abstract]:The material composition and crustal structure of the Xunhua Daozhang area in Qinghai Province are very complex, and the tectonic evolution has a long history. There are many NWW directions and NW-NNW trending faults. Among them, the Jinku Street-Multi-branch Dam oblique thrust fault (known in the region as the Longwu River-Daxia River fault) developed in the south, It constitutes the boundary faults between the middle Hualong microblock and the Lachinshan tectonic belt in the northern Qilian orogenic belt and the northern tectonic belt of the west Qinling orogenic belt in the south. In this paper, the volcanic rocks of different metamorphic degrees in Xunhua area of Qinghai Province are selected as the research objects, and through field geological investigation and comprehensive study of petrology, mineralogy, petrogeochemistry and isotopic chronology, etc. The main results are as follows: (1) the exposed Hualong rock group in Xunhua area of Qinghai Province is mainly composed of amphibolite and a small amount of metamorphic rocks, the metamorphism of which can reach the medium and low amphibolite facies, and the metamorphic temperature and pressure meter of amphibolite-plagioclase metamorphic, The metamorphic temperature is 691 ~ 772 鈩，
本文编号：2427852
[Abstract]:The material composition and crustal structure of the Xunhua Daozhang area in Qinghai Province are very complex, and the tectonic evolution has a long history. There are many NWW directions and NW-NNW trending faults. Among them, the Jinku Street-Multi-branch Dam oblique thrust fault (known in the region as the Longwu River-Daxia River fault) developed in the south, It constitutes the boundary faults between the middle Hualong microblock and the Lachinshan tectonic belt in the northern Qilian orogenic belt and the northern tectonic belt of the west Qinling orogenic belt in the south. In this paper, the volcanic rocks of different metamorphic degrees in Xunhua area of Qinghai Province are selected as the research objects, and through field geological investigation and comprehensive study of petrology, mineralogy, petrogeochemistry and isotopic chronology, etc. The main results are as follows: (1) the exposed Hualong rock group in Xunhua area of Qinghai Province is mainly composed of amphibolite and a small amount of metamorphic rocks, the metamorphism of which can reach the medium and low amphibolite facies, and the metamorphic temperature and pressure meter of amphibolite-plagioclase metamorphic, The metamorphic temperature is 691 ~ 772 鈩，
本文编号：2427852
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