新疆东准噶尔卡拉麦里蛇绿岩带两侧地层沉积特征对比

Comparison of Sedimentary Characteristics on Both Sides of Karamaili Ophiolite Belt in Eastern Junggar, Xinjiang

卡拉麦里蛇绿岩带位于中国新疆准噶尔盆地的东北缘,此处蛇绿岩带所代表的古洋盆的形成和闭合时代一直是学术界所争论的问题之一,查明卡拉麦里蛇绿岩带所代表的古洋盆的形成和闭合时间,是新疆东准噶尔演化历史的关键性的地质问题之一。本文总结归纳前人对于此地沉积地层的研究,通过对蛇绿岩带两侧早古生代地层的结构构造、接触关系、生物化石及主要岩石组合等沉积–构造特征进行归纳研究和对比分析,探讨区域内沉积特征及不整合关系,以此确定卡拉麦里蛇绿岩带所代表的古洋盆闭合时代。卡拉麦里南北区域,自下而上,从志留系至石炭系地层为整合接触,连续沉积,沉积物主要以火山碎屑岩为主,沉积物粒度表现为由粗变细再变粗的特征,表现为先海进再海退的沉积环境,并含有丰富的动植物化石。因此可以确定研究区的沉积相表现为:浅海–滨浅海–陆相。在卡拉麦里蛇绿岩带南北两侧地区的早古生代地层中,由底至顶,广泛存在几组角度不整合。这些古生代的区域性不整合构造对应的是卡拉麦里古生代洋盆的闭合:陆–陆碰撞造山事件。卡拉麦里蛇绿岩带所代表的洋盆在志留系以前已经闭合。

The Karamaili ophiolite belt is located on the northeastern margin of the Junggar Basin in Xinjiang, China. The formation and closure age of the ancient ocean basin represented by the ophiolite belt has always been one of the academic issues. The formation and closing time of the ancient ocean basin represented by the greenstone belt is one of the key geological issues in the evolution history of eastern Junggar in Xinjiang. This article summarizes previous studies on the sedimentary strata in this area. Through the structure and structure of the Early Paleozoic strata on both sides of the ophiolite belt, the structure, contact relationship, biological fossils and main rock assemblages and other sedimentary characteristics are summarized and compared. The sedimentary characteristics and unconformity relationships in the region are discussed to determine the closure age of the paleo-oceanic basin represented by the Kalamaili ophiolite belt. In the north-south area of Karamaili, from bottom to top, the Silurian to Carboniferous strata are in integrated contact and continuous deposition. The sediments are mainly volcanic clastic rocks, and the grain size of the sediments changes from coarse to fine and then coarse. It is characterized by a sedimentary environment that advances first and then retreats, and is rich in fossils of animals and plants. Therefore, it can be determined that the sedimentary facies of the study area are as follows: shallow sea-coastal shallow sea-land facies. In the early Paleozoic strata on the north and south sides of the Karamaili ophiolite belt, from bottom to top, the following angular unconformities are widespread. These Paleozoic regional unconformities correspond to the closure of the Karamaili Paleozoic ocean basin: a land-continent collision orogenic event. The ocean basin represented by the Karamaili ophiolite belt was closed before the Silurian.