鄂尔多斯盆地西南部上三叠统延长组碎屑锆石U-Pb定年及其物源意义

发布时间：2018-02-25 22:21

本文关键词： 碎屑锆石U-Pb定年重矿物物源分析长段鄂尔多斯盆地西南部　出处：《地质学报》2017年11期 　论文类型：期刊论文

【摘要】：由于构造位置的特殊性和勘探开发工作的局限性,鄂尔多斯盆地西南部上三叠统延长组6段的物源分析一直存在较大的分歧。本文选取鄂尔多斯盆地西南部里78井、庄33井、演40井以及lm水河地区上三叠统长6段砂岩为研究对象,运用LA-ICP-MS U-Pb方法对样品中的碎屑锆石进行了年代学研究。结果表明,4个样品都存在250~350 Ma、400~660 Ma、920~1200 Ma、1750~1950 Ma和2200~2600 Ma 5个基本相近的年龄区间,与之对应的峰值年龄主要集中在284~330 Ma、430~460 Ma、950~1000 Ma、1850~1915 Ma以及2250~2450Ma。通过与邻区碎屑锆石年龄分布特征对比并结合重矿物资料,对研究区长6段物源的方向、母岩时代及岩性进行了系统全面的分析,认为研究区物源具有多方向、多时期、多岩石类型的特点,主要来自于盆地西南缘、南缘分布的北秦岭西段、北祁连东段及西秦岭的加里东期岩浆岩、晋宁期岩体和位于盆地东北部的古元古代孔兹岩系,盆地西北缘阿拉善地块的华力西期岩浆岩、鄂尔多斯地块东南部的变质基底也提供了部分物源。这一研究结果将有助于进行原盆沉积环境的恢复和指导下一步油气勘探的部署。
[Abstract]:Due to the particularity of structural location and the limitation of exploration and development work, there has been a great disagreement in the analysis of provenance in the sixth member of the Upper Triassic Yanchang formation in the southwest of Ordos Basin. In this paper, we select well Li78 and well Zhuang33 in the southwest of Ordos Basin. Yan40 well and Upper Triassic Chang 6 sandstone in Lm Shuihe area are studied. The LA-ICP-MS U-Pb method was used to study the zircon dating in the samples. The results show that there are five basic similar age ranges of 250 ~ 350 Ma ~ (350) Ma ~ (400) ~ (600) Ma ~ (60) ~ (60) Ma ~ (920) ~ 1 200 Ma ~ (1 750) Ma ~ (175) ~ (50) Ma and 2 200 ~ (2 600) Ma ~ (2 600) Ma in the four samples. The corresponding peak age is mainly concentrated at 284An 330 Ma, 430 Ma, 460 Ma, 950 Ma, 1000 Ma, 1850 Ma, 1915 Ma, and 2250 Ma, 2450 Ma, respectively. By comparing with the age distribution characteristics of clastic zircons in the adjacent area and combining with heavy mineral data, the direction of the source of the Chang 6 member in the study area is discussed. Based on the systematic and comprehensive analysis of the parent rock age and lithology, it is considered that the study area has the characteristics of multi-direction, multi-period and multi-rock types, mainly from the western part of the North Qinling Mountains, which is distributed in the southwestern margin of the basin and the southern margin of the basin. Caledonian magmatic rocks in the eastern part of North Qilian and the West Qinling Mountains, Jinning rock bodies and Paleoproterozoic Kongzi rocks in the northeast of the basin, and the Variscan magmatic rocks in the Alashan block in the northwestern margin of the basin. The metamorphic basement in the southeast of the Ordos block also provides some provenance, which will be helpful for the restoration of the sedimentary environment of the probasin and the deployment of oil and gas exploration in the next step.
【作者单位】：中国石油大学油气资源与探测国家重点实验室;中国石油大学地球科学学院;山东科技大学地球科学与工程学院;
【基金】：海外及港澳学者合作研究基金(编号41428201)资助的成果
【分类号】：P534.51;P618.13

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