西藏改则热那错东早白垩世火山岩岩石地球化学特征及大地构造意义

发布时间：2018-02-24 00:17

本文关键词： 班公湖-怒江热那错火山岩岩石地球化学 U-Pb测年　出处：《中国地质大学(北京)》2015年硕士论文　论文类型：学位论文

【摘要】：火山岩作为地球内部岩浆活动的产物,不仅能够反映出岩浆活动的特点,还能使我们清楚认识板块构造演化历程。前人已对班公湖-怒江构造带进行了较为详细的研究。由于其特殊大地构造位置及意义,一直以来都是国内外研究的焦点。由于近年来在班怒缝合带上发现多例超大型含金斑岩铜矿,使得对该缝合带的研究不仅具有构造意义,同时还有较大的经济意义。早白垩世岩浆活动为成矿提供了物源,因此研究早白垩世岩浆活动对于总结该缝合带的成矿规律有重要意义。研究区位于藏北高原中部,构造位置位于班公湖-怒江缝合带北侧。通过对研究区内热那错东火山岩的岩性、分布及火山机构的详细野外地质调查,结合火山岩剖面、室内岩石化学、地球化学及地质年代测定,论文取得主要成果和认识如下:研究认为热那错东火山岩分布层位单一,均位于美日切错组,岩性以玄武岩为主,并伴有安山岩、流纹岩及火山角砾岩,研究区岩浆最初时主要以基性玄武岩作为主体,伴随着岩浆活动,从熔体中分离出斜长石等矿物,使岩浆最终转化为酸性。热那错火山岩年龄值为111.7Ma左右,为早白垩世。研究区火山岩地球化学特征显示为俯冲消减作用的钙碱性弧火山岩。研究区内的火山岩所具有的特征表明研究区火山岩的构造环境为洋壳俯冲消减,无陆陆碰撞。在早白垩世,南羌塘陆块边缘为增生型大陆边缘,班公湖-怒江洋盆于早白垩世末期俯冲消减。
[Abstract]:Volcanic rock, as a product of magmatic activity in the interior of the earth, can not only reflect the characteristics of magmatic activity, It can also help us to understand clearly the evolution of plate tectonics. The Bangonghu-Nujiang tectonic belt has been studied in detail by predecessors. Because of its special tectonic location and significance, It has always been the focus of research at home and abroad. Due to the discovery of a number of super-large gold porphyry copper deposits in the Bannu suture zone in recent years, the study of the suture zone is not only of tectonic significance. The study of early Cretaceous magma activity is of great significance in summarizing the metallogenic regularity of the suture zone. The study area is located in the middle of the Tibetan Plateau. The tectonic location is located on the northern side of Bangong Lake-Nujiang suture belt. Through the detailed field geological investigation of the lithology, distribution and volcanic mechanism of the volcanic rocks in the eastern part of the study area, combined with the volcanic rock profile, the interior petrochemistry, The main achievements and understandings of geochemistry and geochronology are as follows: it is considered that the volcanic rocks in the eastern part of Rinaco are all located in the United States and Japan, and the lithology is dominated by basalt and accompanied by andesite. Rhyolite and volcanic breccia, magma in the study area was mainly dominated by basalt at first, accompanied by magmatic activity, plagioclase and other minerals were separated from the melt. The magma is finally converted to acid. The age value of the Rynagh volcanic rocks is about 111.7 Ma. The geochemical characteristics of volcanic rocks in the study area show subduction subduction calc-alkaline arc volcanic rocks. The characteristics of volcanic rocks in the study area indicate that the tectonic environment of the volcanic rocks in the study area is subduction of oceanic crust. In the early Cretaceous, the margin of the southern Qiangtang block was an accretive continental margin, and the Bangong Lake-Nujiang ocean basin subducted and subducted at the end of the early Cretaceous.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P588.14;P618.41

【参考文献】