【作者】 刘贤；

【导师】 张成立；

【作者基本信息】 西北大学 ， 矿物学、岩石学、矿床学， 2010， 硕士

【摘要】 鄂尔多斯盆地位于华北板块西部,介于南侧的秦岭-祁连山造山带与北侧的阴山-燕山造山带之间,通常认为其于晚古生代兴蒙海槽闭合与秦岭海槽消减时形成雏形,华北板块与秦岭微板块及西伯利亚板块对接、碰撞,强烈的造山作用及风化剥蚀等过程在鄂尔多斯盆地内留下了良好的沉积记录,成为研究盆地演化乃至盆山关系的关键。碎屑沉积物是记录这些地质过程的良好载体,尤其是作为砂岩主要组分的骨架矿物、稳定性较强的重矿物,以及保留有物源区母岩性质的岩屑等,包含了物源区的大量信息,可以用来综合判别物源区性质,指示物源方向等,是盆地物源分析的基础手段。而碎屑锆石具有极强的稳定性,并且广泛分布于碎屑沉积岩中,对砂岩碎屑锆石开展微区原位U-Pb同位素定年与物源示踪研究,可以准确提取沉积物年龄的信息,结合区域地质概况及周缘山系基底出露情况可以对盆地不同时期的沉积物源区进行示踪。论文通过对鄂尔多斯盆地延长地区上古生界岩心观察、铸体薄片鉴定、粒度分析、碎屑锆石U-Pb定年等分析测试手段,对石千峰组、盒8段、山西组砂岩储层的岩石学特征及轻、重矿物特征、组合及其在纵向、平面上的分布规律、碎屑锆石年代学等进行了系统的研究,讨论了其物源区、源区母岩性质及其对优质储层的影响。结果显示,鄂尔多斯盆地延长地区石千峰组、盒8段、山西组砂岩的轻、重矿物特征及组合分为四个区域：延安-延长为中心区域,砂岩的颗粒较均匀,细粒,成熟度较高,石英含量也很高,变质岩、沉积岩、岩浆岩岩屑均含有,重矿物以含铁矿物+钻石为主；安塞-子长为西北区域,砂岩颗粒为中-粗粒次棱角状,石英含量较高,以火成岩岩屑和变质岩岩屑为主,重矿物主要为含铁矿物+绿泥石+锆石,指示源岩为火成岩和变质岩；绥德-清涧为东北区域,砂岩颗粒为中粒次棱角状,以石英为主,其次是岩屑,几乎不含长石,含变质岩岩屑、火成岩岩屑及沉积岩岩屑,重矿物以绿泥石+含铁矿物+锆石为主,指示源区为沉积岩及变质岩；甘泉向南为南部区域,砂岩以石英为主,长石含量高于以上区域,岩屑以沉积岩和变质岩岩屑为主,少量岩浆岩重矿物以绿泥石+含铁矿物+锆石为主,指示源区主要为变质岩、沉积岩和岩浆岩。结合碎屑锆石年龄分析可知本区物源主要来自北部阴山地块基底岩系中早元古代晚期(2300Ma-1800Ma)孔兹岩带和早元古代早期(2600Ma-2300Ma) TTG片麻岩及海西期岩浆活动产物及少量南部秦岭造山带中秦岭群(1987-2267Ma)和宽坪群(1142-986Ma)深变质岩系及古生代变质岩系和岩浆活动的产物(1000-400Ma),极少量是来自(2500Ma-1900)陇山TTG片麻岩、阴山地块太古代古老变质岩系。陆源碎屑源于物源区的母岩,并构成沉积盆地内砂岩的骨架,砂岩的储集性能与陆源碎屑成分相关,并取决于源区的岩性和风化程度。本区的陆源碎屑物质主要来自于孔兹岩、片麻岩及花岗岩,由于温湿的古气候条件,源区风化作用特别是化学风化作用强烈,不稳定的长石和岩屑物质被改造贻尽,中部区域砂岩石英含量最高,平均孔隙度、渗透率较高,物性较好,是该地区的主要富气区域；而南、北部的长石及岩屑含量稍高,其储集性能相对较弱。更多还原

【Abstract】 Ordos Basin locate in western North China Block, betweem Qinling-Qilian orogen and Yinshan-Yanshan orogen in the north and south respectively. It is considered formed along with the closure of Xinmeng ocean and subduction of Qinling ocean in late paleozoic. Voluminous sedimentary materials were transited into the ambient basins and deposited there during the process of continent-continent collision, extrud orogeny and erosion between North China Plate and Qinling block, siberia plate in Ordos Basin, it can provide powerful evidence for exploring orogenic process.Clastic sediments is the excellent carrier for these orogenic process, transporting rocks can lose or change minerals, but a lot of information from sources can be brong to destination. Heavy minerals of sandstones can judge source area lithology because of higher stability; matrix minerals can indicate provenance direction because they are the major mineral components; debris can be used to sure characteristics of parent rocks because it keep characteristics of parent rocks. Detrital zircons is of extremely stability, and it distribute of detrital sedimentary widely. It construct age spectrum of detrital zircons in the Shiqianfeng, He 8 and Shanxi Formation of the Low Permian, Upper Paleozoic in Ordos basin, and research on chronology and characteristics of parent rocks in provenance tracing, using techniques of LA-ICPMS in situ U-Pb isotopic dating and trace element analysis of detrital zircons, accompanied with comparative study on petrology of skeleton and heavy minerals and their assemblages in the sandstones.Through observing the drilled rocks, elevating the casted rock slice, analyzing grain size, and by detrital zircon U-Pb dating and other analysis and measurement methods on Upper Paleozoic Yanchang zone in the Ordos Basin, this paper has done the folowing systematic researchs on the lithology characteristics, characteristics and composition of the light and heavy minerals and these minerals distribution in the vertical and horizontal dereciton, detrital zircon geochronology and other researches for Shi qianfeng Group, He 8 section, Shanxi Group sandstone reservoir,discussing of its provenance, source rock properties and the impact of the reservoir.The result of the research showing that, the characteristics and composite of the light and heavy minerals in the Shi qianfeng Group, He 8 section, Shanxi Group of upper Paleozoic Yanchang zone in the Ordos Basin were divided into three source directional zones. The first is the Middle zone of Yan’an-Yanchang, the grains of the sandstone is steady and fine, with high maturity and high content of quartzes, the debris concludes metamorphic, sedimentary,igneous debris, and the heavy minerals contain zircon and ion minerals mainly. The second zone is the Northwest zone of Ansai-Zichang, the Sandstone particles is middle-coarse and sub-angular, the quartz content is high, almost no feldspar existed, and the mainly heavy minerals are iron minerals, chlorite and zircons, indicating that it originated from igneous and metamorphic lithic debris. The third zone is the Northeast zone of Suide-Qingjian, the sandstone particles is middle and sub-angular, the sandstone grain contains mostly quartz and with little feldspar, and metamorphic, sedimentary, igneous debris and no more feldspar, the heavy minerals are mainly iron minerals, chlorite and zircons, indicating its source is sedimental and metamorphic rocks. From the Ganquan to its south is the southern zone, the sandstone grain is mainly quartz,and the content of the feldspar is higher than the other zones, and the debris is manly sediment and metamorphic rocks. The little igneous rocks contains mainly heavy minerals of iron minerals, chlorite and zircons, indicating that its source is metamorphic, sedimentary, igneous rocks..It’s can be concluded that the provenance is mainly from the early or meso proterozoic khondalite belt and early proterozoic TTG gneiss in the substrate rocks of north Yinshan mountain land mass early or meso proterozoic, hercynian rocks, metamorphic in the southern Qinlin orogenic belt, paleozoic metamorphic rocks and magmatic results by the chronology of detrital zircons. The rest is from archaeozoic metamorphic rocks in Yinshan land mass and Longshan TTG gneiss.The terrigenous clasolite is from the provenance bed rock. It forms the sand matrix of sedimentary basin. The reservoir properties of sand are related with the composition of the terrigenous clasolite, and depend on the lithology and rate of decay. The terrigenous clasolite is from the khondalite, gneiss and granite. Because of the warm and moist paleoclimate the unstable feldspar and clasolite.Because the warm and wet peoclimate, the weathering especially the chemical weathering is very strong,and the unstable feldspar and debris were completely chaged.The grains of sandstone of middle zone is almost quartz, the average porosity and permeability is high, and the prosperity is good, which is main gas area, and in the north and south region,the feldspar and debris is higher than the middle region, the prosperity of the reservoir is weak. This is significant to the theory and practices to prospect the favorable exploring region and promote the exploration of the gas in the Ordos basin.更多还原