东昆仑造山带东段南坡洪水川组地质特征、物源属性及构造意义

发布时间：2018-05-07 11:23

本文选题：东昆仑东段南坡 + 洪水川组　；参考：《长安大学》2015年硕士论文

【摘要】：造山带沉积岩,是探讨造山带构造演化一个不可忽视的研究对象。造山带沉积岩物源属性的研究能为造山带研究提供较为连续的构造演化证据。本文通过沉积岩石学、砾岩砾石统计、砂岩碎屑组分统计、岩石地球化学、碎屑锆石同位素年代学等手段,对出露于东昆仑造山带东段南坡下三叠统洪水川组的物源属性进行综合研究,并反演东昆仑南缘古特提斯洋早三叠世俯冲造山演化过程,为东昆仑南缘古特提斯洋演化提供沉积学证据,并取得以下认识和进展。1、东昆仑南坡下三叠统洪水川组由底至顶可分为6段:一段为红绿相间碎屑岩组合,二段为浅灰-灰绿色碎屑岩组合,三段为灰黑-深灰色薄层灰岩组合,四段为灰色-灰黑色灰岩与细碎屑岩组合,五段为深水浊积岩组合,六段为细碎屑岩组合。其中一、二段为扇三角洲沉积体系,三、四段为浅海混积陆棚沉积体系,五段为半深海-深海浊积扇沉积体系,六段为浅海-滨浅海混积陆棚沉积体系。2、砾岩砾石统计结果显示,北带洪水川组a段沉积时水体较浅,南带洪水川组第二段沉积时水体较深,反映沉积盆地北浅南深,物源可能来自北侧。南带洪水川组第二段砾岩源区岩石类型主要为变质岩、花岗岩及脉石英,具隆升基底特征,初步反映源区构造背景为活动大陆边缘。3、砂岩碎屑组分统计显示,洪水川组下部地层(一、二段)砂岩源区构造背景为活动大陆边缘;洪水川组上部地层(四、五、六段)源区构造背景为大陆岛弧。对应的源区分别为隆升的基底和大陆岛弧。4、岩石地球化学特征显示,洪水川组下部地层(一、二段)砂岩源区构造背景为活动大陆边缘,源区岩石类型包括成熟大陆石英岩、花岗岩、花岗闪长岩及长英质火山岩等。洪水川组上部地层(四、五、六段)源区构造背景为大陆岛弧,源区岩石类型包括花岗闪长岩、安山岩、长英质火山岩等。5、洪水川组一段LA-ICP-MS碎屑锆石U-Pb年龄谱显示,其源区为加里东期岩浆弧,但洪水川组下部地层地球化学特征显示其与活动大陆边缘相近,因此推测其物源除岩浆弧外,源区大面积出露有前寒武纪变质岩,因此其物源主要为东昆仑加里东期岩浆弧和前寒武纪变质基底。6、综合上述资料分析洪水川组物源显示,洪水川组下部地层(一、二段)砂岩源区构造背景为活动大陆边缘;洪水川组上部地层(四、五、六段)源区构造背景为大陆岛弧。洪水川组下部地层(一、二段)砂岩源区为东昆仑加里东期岩浆弧与前寒武纪变质基底的混合源区;洪水川组上部地层(四、五、六段)源区主要为东昆仑早印支期陆缘弧与加里东期岩浆弧,含一定比例的的前寒武纪变质基底。洪水川组源区下部地层(一、二段)砂岩源区岩石类型包括石英岩、花岗岩、花岗闪长岩、长英质火山岩等;洪水川组上部地层(四、五、六段)源区岩石类型包括长英质火山岩、花岗闪长岩、安山岩以及石英岩、花岗质片麻岩等。
[Abstract]:Sedimentary rock of orogenic belt is an important research object in structural evolution of orogenic belt. The study of source properties of sedimentary rocks in orogenic belts can provide more continuous evidence of tectonic evolution for the study of orogenic belts. By means of sedimentary petrology, gravel statistics, sandstone clastic component statistics, rock geochemistry, zircon isotopic chronology, etc. The provenance properties of the Lower Triassic Flood Chuan formation on the south slope of the eastern part of the East Kunlun orogenic belt are studied synthetically, and the early Triassic subduction orogenic evolution of the PaleoTriassic in the southern margin of East Kunlun is inversed. It provides sedimentary evidence for paleoTethys ocean evolution in the southern margin of East Kunlun, and obtains the following knowledge and progress. 1. The Lower Triassic Flood Sichuan formation on the southern slope of East Kunlun can be divided into 6 sections: one is the red and green interfacies clastic rock assemblage, the other is the red and green interfacies clastic rock assemblage. The second member is composed of shallow grayish-grey-green clastic rock assemblage, the third member is gray-dark gray thin layer limestone assemblage, the fourth member is gray-black limestone association with fine clastic rock, the fifth member is deep-water turbidite assemblage, and the sixth member is fine clastic assemblage. The first and second member are fan delta sedimentary system, the third and fourth member are shallow sea mixed shelf sedimentary system, and the five member are semi-deep-sea turbidite fan system. The sixth member is a shallow-shore-shallow-sea mixed shelf sedimentary system. The statistical results of gravel and gravel show that the water body of member a of the North Flood Chuan formation is shallow when it is deposited, and that of the second member of the South Flood Chuan formation is deeper than that of the second member of the South Belt, which reflects the shallow and southern depth of the sedimentary basin. The provenance may come from the north side. The source rocks of the second member conglomerate of the southern belt are mainly metamorphic rocks, granite and vein quartz, with uplift basement features. The tectonic setting of the source area is active continental margin .3. the statistical analysis of sandstone clastic components shows that, The tectonic setting of the sandstone-source area in the lower part of the Hongchuan formation is the active continental margin, and the tectonic setting of the upper strata (fourth, fifth, sixth member) of the flood Sichuan formation is the continental island arc. The corresponding source areas are uplift basement and continental island arc. The petrogeochemical characteristics show that the tectonic setting of the sandstone source area is active continental margin, and the source rocks include mature continental quartzite. Granite, granodiorite and felsic volcanic rocks. The tectonic setting of the source area of the upper strata (member 4, 5, 6) is continental island arc. The source rock types include granodiorite, andesite, felsic volcanic rock, etc. The LA-ICP-MS zircon age spectrum of the first member of the Fongchuan formation shows that the source rocks are composed of granodiorite, andesite, feldspar volcanic rock and so on. The source area is Caledonian magmatic arc, but the geochemical characteristics of the lower part of the Flood Chuan formation show that it is close to the active continental margin. Therefore, it is assumed that the provenance of the source area, except for the magmatic arc, is a large area of Precambrian metamorphic rocks. Therefore, its provenance is mainly Caledonian magmatic arc and Precambrian metamorphic basement. The tectonic setting of the source area of the upper strata (member 4, 5, and 6) of the Hunghuanchuan formation is continental island arc. The source area of the sandstone source area in the lower part of the Hongchuan formation is the mixed source of Caledonian magmatic arc and Precambrian metamorphic basement in East Kunlun. (6) the source region is mainly composed of the early Indosinian continental margin arc and Caledonian magmatic arc in East Kunlun with a certain proportion of Precambrian metamorphic basement. The rock types of the sandstone-source area in the source area of the Sungongchuan formation include quartzite, granite, granodiorite, feldspathic volcanic rocks, etc. The source rocks include felsic volcanic rocks, granodiorite, andesite and quartzite, granitic gneiss, etc.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：P548

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