新疆西准噶尔谢米斯台地区火山岩地层

发布时间：2018-03-24 03:18

本文选题：西准噶尔　切入点：谢米斯台　出处：《中国地质大学(北京)》2015年硕士论文

【摘要】：传统上,新疆西准噶尔谢米斯台地区的火山岩地层被归属为泥盆系-石炭系。这种归属主要依据区域地层对比,缺乏确定性的科学依据。本文报道了该区火山岩地层的两条剖面,并对区内出露的主要火山岩类型进行了详细描述。根据火山岩地层中岩石的不整合接触关系、岩石组合及蚀变特征将其分为两套不同时代的火山岩。在此基础上,提供了代表性火山岩的锆石U-Pb测年结果。提出谢米斯台火山岩的时代(423.6-394.1Ma)属于晚志留世-早泥盆世而不是中晚泥盆纪-石炭纪。晚志留世火山岩主要为安山岩和英安岩,夹少量火山凝灰岩和蚀变砂岩。下泥盆统的组成岩石主要为安山质-英安质火山碎屑岩,夹有大量砂砾岩。该区地层的产状总体南倾构成一个单斜。此外探讨了该区火山岩地层的大地构造归属及其时空联系性,认为谢米斯台火山岩是东哈萨克斯坦博什库尔-成吉斯早古生代岩浆弧向东的延伸,可与东西两侧的火山岩地层构成一个连续的晚志留世-早泥盆世火山岩带。谢米斯台古生代火山岩的Si O2含量多数56%,其Al2O3含量较高,多数具有高钾钙碱性、准铝质-过铝质的特点。在主量元素哈克图解中Ti O2、Al2O、Ca O、Mg O、TFe O和P2O5都与Si O2呈现负相关的趋势。火山岩的LREE相对于HREE略显富集,Eu无明显负异常。微量元素Rb、K等大离子亲石元素为正异常,高场强元素Nb、Ta、P和Ti的负异常以及构造判别图解都显示该地区火山岩来源于俯冲环境。结合已报道的火山岩年龄(435Ma-391Ma),认为谢米斯台地区主体为博什库尔-成吉斯早古生代岩浆弧向东的延伸部分,同时又复合有少量扎尔玛-萨吾尔晚古生代岩浆弧。谢米斯台地区火山岩源于大洋岩石圈向下俯冲,脱水产生的富集大离子亲石元素的流体以及洋壳熔融产生的中酸性熔体进入地幔楔造成地幔部分熔融,岩浆在上升的过程中由于同化混染或地壳熔融而加入大陆地壳的物质并经历一定的岩浆结晶分异作用而成。岩浆起源深度约为8km-33km,并且晚古生代的火山岩岩浆起源深度略深于早古生代岩浆。
[Abstract]:Traditionally, the volcanic strata in the West Junggar, Xinjiang, are classified as Devonian Carboniferous. This attribution is mainly based on regional stratigraphic correlation. This paper reports two sections of volcanic strata in this area and describes in detail the main types of volcanic rocks exposed in this area. The rock assemblages and alteration features divide them into two sets of volcanic rocks of different ages. The zircon U-Pb dating results of typical volcanic rocks are provided. It is suggested that the age of Shermisi volcanic rocks (423.6-394.1 Ma) belongs to late Silurian and early Devonian rather than middle and late Devonian to Carboniferous. The late Silurian volcanic rocks are mainly andesite and dolomite. A small amount of volcanic tuff and altered sandstone. The rocks of the Lower Devonian are mainly composed of Anshanian and Anshanian volcanic clastic rocks. The occurrence of strata in this area is generally southward inclined to form a monocline. In addition, the geotectonic attribution and space-time connection of volcanic strata in this area are discussed. It is considered that the shemis platform volcanic rock is an extension of the early Paleozoic magmatic arc eastward from Boshkul to Chungis in East Kazakhstan. A continuous late Silurian to early Devonian volcanic rock belt can be formed from the volcanic strata on both sides of the east and west. The Sio 2 content of the Cenozoic volcanic rocks of the Shermisi platform is 56%, its Al2O3 content is relatively high, and most of them have high potassium calc alkalinity. The characteristics of quasi-aluminite-peraluminite. In the Huck diagram of the principal element, TIO _ 2AL _ 2O _ 2, Ca, O, O, Fe, O _ (TO) and P2O5 are negatively correlated with Sio _ 2. The LREE of volcanic rocks is slightly less negative than that of HREE in enrichment of EU, and the trace element RB _ (K) is larger than that of Fe _ (2) O _ (2) O _ (2) O _ (2) O _ (2) O _ 2. The child lithophile element is positive anomaly, The negative anomalies of the high field strength elements NbPand Ti, as well as the tectonic discriminant diagrams, show that the volcanic rocks in this area originated from the subduction environment. Combined with the reported volcanic age of 435 Ma-391Ma, it is considered that the main body of the Shemis platform is Boshkur-early Genghis Paleo. The eastward extension of the Cenozoic magmatic arc, At the same time, there are a small amount of late Paleozoic magmatic arcs in Zarma-Savour. The volcanic rocks in the Shemistai area originated from the downward subduction of the oceanic lithosphere. Fluids enriched in large ion lithophile elements from dehydration and intermediate-acid melts from ocean crust melting into the mantle wedge lead to partial mantle melting. In the process of magma rising, the materials added to the continental crust due to assimilation or crustal melting are formed by certain magmatic crystallization differentiation. The origin depth of magma is about 8km-33km, and the magmatic origin of late Paleozoic volcanic rocks is about 8km-33km. The depth is slightly deeper than the early Paleozoic magma.
【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

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