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阿尔金山喀腊大湾地区位于北东向阿尔金走滑断裂北侧与东西向阿尔金北缘断裂所夹持的区域,是区域上红柳沟-拉配泉构造带的中段。该区广泛发育火山-沉积岩系,前人将其确定为中元古代。本文运用锆石SHRIMP U-Pb方法对区内火山-沉积岩系中的中酸性火山岩进行测年,获得477~485Ma的年龄,确认喀腊大湾地区早古生代中酸性岩浆喷发活动的存在。同时根据岩石地球化学研究,显示这套火山岩具有活动大陆边缘(岛弧)构造环境,其岩浆源具有I型及I与S过渡类型特点。结合前人对红柳沟-拉配泉一带的蛇绿混杂岩、高压变质泥岩、榴辉岩、中酸性侵入岩等相关年代资料及构造环境示踪,作者认为喀腊大湾地区中酸性火山岩形成于活动大陆边缘(岛弧)大地构造环境,其时限与蛇绿混杂岩的末期非常接近,代表了洋壳俯冲碰撞过程中形成的同碰撞中酸性火山岩。据此可以将区域上红柳沟-拉配泉一带的构造演化划分为洋壳扩张期(晚元古代末-寒武纪,蛇绿混杂岩年龄510~580Ma,但扩张起始会早一些)、洋壳板块俯冲碰撞期(早奥陶世-中奥陶世早期,中酸性岩浆岩(包括侵入岩和火山岩)年龄为477~488 Ma(部分花岗岩年龄延迟到467Ma左右),以及高压变质岩的退变质年龄479~491Ma),碰撞后伸展期(晚奥陶世—志留纪,蛇绿混杂岩变质基质岩系的变质年龄450~455Ma,代表蛇绿混杂岩最后就位,碰撞—碰撞后S型碱性花岗岩年龄417~431Ma,代表碰撞后伸展构造环境)三个演化阶段。
The area of the Karak-Dawan Bay in the Altun Mountains is located in the north-east part of the Altyn Tagh fault and the northern part of the east-west Altyn Tagh fault. It is also the middle part of the Hongliugou-Laizquan structural zone in the area. The area is widely developed volcano - sedimentary rock series, predecessors identified as Mesoproterozoic. In this paper, zircon SHRIMP U-Pb method was applied to the dating of moderately acidic volcanic rocks in the volcanic-sedimentary rock series in the area, and the age of 477 ~ 485 Ma was obtained to confirm the existence of acid magmatic eruption in the Early Paleozoic in the area of Chawalawan. According to the geochemical study of rocks, it shows that this volcanic rock has active continental margin (island arc) tectonic environment, and its magmatic source has the characteristics of I-type and I-S transitional types. Based on the previous dating and tectonic setting of the ophiolitic melange, high-pressure metamorphic mudstone, eclogite and intermediate-acid intrusive rock in the area of Hongliugou-Laizquan, the author thinks that the formation of intermediate- The tectonic setting on the margin of the active continental margin (island arc) is very close to the end of the ophiolitic mélange, representing the intra-collisional acidic volcanic rocks formed during the submarine collision of the oceanic crust. According to this, the tectonic evolution of Hongliugou-Laizquan area in the area can be divided into the period of oceanic shell expansion (late Proterozoic-Cambrian-ophiolitic melange of 510-580 Ma, but the onset of expansion will be earlier) In the early period of Early Ordovician-Middle Ordovician, the age of intermediate-acidic magmatic rocks (including intrusive rocks and volcanic rocks) is 477-488 Ma (part of the granite age is delayed to about 467Ma), and the high-pressure metamorphic rocks Metamorphic age 479 ~ 491Ma). After the collision, the metamorphic rocks of Late Ordovician-Silurian and ophiolitic metamorphic rocks have a metamorphism age of 450 ~ 455Ma, indicating that the ophiolitic melanges finally took place. After the collision-collision S-type alkaline granite age 417 ~ 431Ma, on behalf of post-collision extensional tectonic environment) three evolution stages.