【作者】 林孝先；

【导师】 侯中健；

【作者基本信息】 成都理工大学 ， 地质学， 2011， 硕士

【摘要】 从十九世纪七十年代开始至今,很少有系统探讨、阐述陆源碎屑岩盆地物源分析方法的专著或者文章出现。该论文选取鄂尔多斯盆地北部下二叠统山西组为研究对象,以沉积学、沉积地球化学、层序地层学、构造地质学、大陆动力学、矿物学与岩石学等学科为理论基础,对物源分析方法分类方案、技术流程,常用物源分析方法的特征、对物源的指示意义等进行了介绍、应用和探讨,总结和提出了陆源碎屑岩盆地综合物源分析思想,并获得了研究区的综合物源信息。在大量区域地质资料的基础上,厘定了研究区内造山带和盆地的构造演化,以及二者的耦合和响应关系。山西期,研究区为北隆南坳的构造格局,故北部的造山带或隆起可能为研究区提供物源。而现今研究区内的贺兰山、桌子山、吕梁山等造山带,其造山期大致是在燕山构造旋回,而在山西期,还位于水平面之下,正在接受沉积,不对研究区提供物源。强调了反剖面、造山带等问题在陆源碎屑岩盆地物源分析中的前提性和重要性,并以此为基础,提出了陆源碎屑岩盆地物源分析方法的分类方案。该分类方案中,将陆源碎屑岩盆地物源分析方法分为造山带特征分析和碎屑岩盆地分析两大部分。在造山带特征分析中,又分为反剖面分析和母岩分析两个方面;在碎屑岩盆地分析中,又分为沉积学、地球化学、地球物理分析方法三个方面,具体的沉积学分析方法包括砂岩碎屑组分分析、重矿物分析、岩屑分析、古流向分析、剖面层序结构分析、砾岩组分分析、砂体分散体系分析、碎屑颗粒结构分析、阴极发光成因分析等九种方法,地球化学分析方法包括常量元素分析、微量元素分析、稀土元素分析、同位素分析等四种方法,地球物理分析方法包括布格重力异常分析、地震及测井分析等两种方法。以该陆源碎屑岩盆地物源分析方法分类方案为基础,分别对研究区山西组进行了逐项的物源分析研究。通过反剖面分析、母岩岩石类型分析、砂岩单碎屑分析、单岩屑分析、砾岩组分分析、阴极发光成因分析、稀土元素源岩分析、锆石U-Pb同位素测年分析等,表明了研究区的母岩主要是其西北部阿拉善地区、北部阴山造山带中太古界、元古界的各类变火山-沉积岩组成的多套古老变质岩系,以及苏右旗-林西构造带的上古生界火山岩等。又通过砂岩多碎屑分析,常量、微量分析,以及稀土元素构造背景分析,显示在山西期研究区的物源区具有发育碰撞造山带的被动大陆边缘和发育沟-弧-盆体系的活动大陆边缘等复杂的、混合的构造环境,这与同时期研究区北部的阴山造山带、苏右旗-林西构造带等的构造环境相一致。再通过重矿物分析、岩屑组合类型分析、砂体分散体系分析、剖面层序结构分析、碎屑颗粒结构分析、古流向分析、稀土元素配分模式图及特征参数分析、布格重力异常分析、地震及测井分析等,说明研究区在山西期确实具有北高南低的古地形,且至少具有三大古水流砂体沉积体系,其分别对应西北部阿拉善地区和北部阴山造山带西段、阴山造山带中西段、阴山造山带中段和苏右旗-林西构造带等三个物源分区。通过研究,该文提出了陆源碎屑岩盆地单因素、多因素分析的综合物源分析思想,总结出了一套较为系统的适合类似于鄂尔多斯盆地的陆源碎屑岩盆地的综合物源分析思路和方法。并依次为指导,对研究区各单因素物源分析方法及其成果进行了综合物源分析,其成果图显示,研究区可分出了三个区域:Ⅰ区,其物源主要为阿拉善地区和阴山造山带西段的太古界、元古界的变火山-沉积岩组成的古老变质岩系等,现今位置大概在阿拉善盟和狼山山脉等地区;Ⅱ区,其物源主要为阴山造山带中西段的太古界、元古界的变火山-沉积岩组成的古老变质岩系,同时还受到Ⅲ区阴山造山带中段和苏右旗-林西构造带等物源的影响,现今位置大概在色尔腾山、乌拉山山脉等地区;Ⅲ区,其物源主要为阴山造山带中段的太古界、元古界的变火山-沉积岩组成的古老变质岩系,以及苏右旗-林西构造带的上古生界火山岩等,现今的大概位置在大青山山脉以及苏右旗-林西等地区。该文中的陆源碎屑岩盆地综合物源分析思想和方法在鄂尔多斯盆地北部下二叠统山西组的成功应用,不仅说明了陆源碎屑岩盆地综合物源分析的正确性与可行性,还对物源分析理论、方法的完善,鄂尔多斯盆地沉积盆地分析工作的进一步开展,以及相似地区的物源分析工作起到积极作用。更多还原

【Abstract】 This article has done some provenance analyses of the Lower Permian Shanxi Formation in northern Ordos Basin, obtains its synthetic information of provenance, and put forward a classification scheme, a synthetic thought, a systematic method of provenance analysis in the terrigenous clastic rock basin.Provenance analysis methods are divided into orogenic belt and basin analyses. The orogenic belt analyses are divided into reverse profile analyses and parent rocks analyses. The basin analyses are divided into sedimentological, geochemical and geophysical analyses.Then the sedimentological analyses are divided into sandstone fragment components, heavy minerals, rock debris, paleocurrent direction, profile sequence structure, conglomerate components, sand body dispersion system, clastic grain structure and cathodoluminescence analyses. The geochemical analyses are divided into major elements, trace elements, rare earth elements and isotope analyses. The geophysical analyses are divided into bouguer gravity anomaly and seism and well logging analyses.The synthetic thought of provenance analysis in the terrigenous clastic rock basin includes univariate and multivariate analysis thought.There is a suggested method and work flow. Firstly, the reverse profile problems have to be solved. Secondly, the studies should be divided into defining the rough provenance direction and subarea, estimating tectonic setting, analyzing parent rocks and dating rocks and stratums of orogenic belt and basin to carry out. Thirdly, using univariate and multivariate analysis of sedimentology, geochemistry and geophysics contrast the conclusions of the before step.Finally, the result map of synthetic information of provenance should be drawn.Based on the synthetic thought of provenance analysis of terrigenous clastic rock basin, there are some conclusions of univariate provenance analyses and a result map of synthetic information of provenance of the Lower Permian Shanxi Formation in northern Ordos Basin.The result map shows three subareas in Shanxi Stage in northern Ordos Basin.The provenance of west subarea is the ancient metamorphic series of the Archean and Proterozoic in the Alxa areas and the west section of Yinshan orogenic belt, which is specifically in the Alxa League and Langshan mountain nowadays. The provenance of middle subarea is the ancient metamorphic series of the Archean and Proterozoic in the middle-west section of Yinshan orogenic belt, which is specifically in the Seertengshan mountain and Daqingshan mountain nowadays, and is also influenced by the provenance of east subarea. The provenance of east subarea is the ancient metamorphic series of the Archean and Proterozoic in the middle section of Yinshan orogenic belt and volcanic rocks of the Upper Paleozoic in the Sonid Right Banner-Linxi tectonic belt, which is specifically in the Daqingshan mountain and Sonid Right Banner-Linxi areas nowadays.The synthetic thought and method of provenance analysis of terrigenous clastic rock basin are successed in the Lower Permian Shanxi Formation, northern Ordos Basin, which not only shows their correctness and practicability, but also is good for the improvement of provenance analysis, the study of sedimentary basin in Ordos Basin and the same study of provenance analysis in the other terrigenous clastic rock basins.更多还原