玛湖凹陷下二叠统风城组碱湖沉积时限厘定  

Controlled Depositional Age of An Alkaline Lake in Lower Permian Fengcheng Formation,Mahu Sag

作　　者：唐文斌[1] 尤新才[2] 张元元[3] 李卉[2] 郭召杰[3] 何文军[2] 李威 唐勇[2] 雷冬 TANG WenBin;YOU XinCai;ZHANG YuanYuan;LI Hui;GUO ZhaoJie;HE WenJun;LI Wei;TANG Yong;LEI Dong(State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation&Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China;Exploration and Development Research Institute,Xinjiang Oilfield Company,PetroChina,Karamay,Xinjiang 834000,China;Key Laboratory of Orogenic Belts and Crustal Evolution of the Ministry of Education,School of Earth and Space Sciences,Peking University,Beijing 100871,China)

机构地区：[1]油气藏地质及开发工程全国重点实验室/成都理工大学沉积地质研究院,成都610059 [2]中国石油新疆油田公司勘探开发研究院,新疆克拉玛依834000 [3]北京大学地球与空间科学学院造山带和地壳演化教育部重点实验室,北京100871

出　　处：《沉积学报》2024年第5期1568-1577,共10页Acta Sedimentologica Sinica

基　　金：国家自然科学基金项目(42090021,42202188)。

摘　　要：【目的】早二叠世的准噶尔盆地是古亚洲洋闭合之后形成的一个陆内继承性断陷盆地。同断陷阶段,在准噶尔盆地西北缘玛湖凹陷充填了最重要的烃源岩层系——下二叠统风城组碱湖烃源岩,但是尚不明确其沉积年龄。【方法】通过扫描电镜和能谱分析对一件凝灰质岩屑砂岩开展了详细的岩石学分析。【结果与结论】该样品包含大量的凝灰岩岩屑和火山玻璃(52%)、中—酸性岩浆岩岩屑(38%),以及少量石英、长石和角闪石矿物(10%),报道的最年轻五颗碎屑锆石年龄平均值及最年轻年龄图谱一致,年龄为282±4 Ma,指示早二叠世的同沉积火山活动是主要物源区,西准噶尔山系和中拐—陆梁凸起是次要物源区。结合碱湖沉积底部和顶部报道的两件凝灰岩样品锆石U-Pb结果,最年轻的五颗碎屑锆石平均年龄分别为284±4 Ma和279±4 Ma。从底部到顶部年龄逐渐变年轻,是同断陷阶段幕式火山喷发的同沉积记录,表明下二叠统风城组碱湖的沉积年龄为284-279?Ma。[Objective]In the Early Permian,Junggar Basin was an intracontinental successive rift basin formed after the closure of the Paleo-Asian Ocean.During the syn-rifting stage,the most important source rock,the Lower Permian Fengcheng Formation alkaline lake source rock,filled in the Mahu Sag on the northwestern margin of the Junggar Basin,but the exact depositional age remains unclear.[Methods]A detailed petrological analysis of a piece of tuffaceous lithic sandstone was conducted by scanning electron microscopy and energy dispersive analysis.[Results and Conclusions]It showed that the sample contained a large amount of tuffaceous clasts and volcanic glass(52%),intermediate-felsic lithic clasts(38%),and a small amount of quartz,feldspar,and hornblende minerals(10%).The published LA-ICP-MS zircon U-Pb dating of this sample shows that the average age of the five youngest detrital zircons and the youngest age peak are consistent,with an age of 282±4 Ma,suggesting that the Early Permian syn-sedimentary volcanic rocks are the major source area,and the mountains in west Junggar and the ZhongguaiLuliang uplifts also have been source areas.Combined with the published zircon U-Pb results of two tuffaceous samples at the bottom and top of the alkaline lake deposition,the average ages of the five youngest detrital zircons were 284±4 and 279±4 Ma,respectively.The age gradually becomes younger from the bottom to top,which is the syn-sedimentary record of episodic volcanic eruptions in the syn-rift stage of the basin,indicating that the sedimentary age of the Lower Permian Fengcheng Formation alkaline lake is 284-279 Ma.

关 键 词：风城组 沉积年龄 锆石U-PB测年 碱湖 下二叠统 玛湖凹陷 

分 类 号：P512.2[天文地球—地质学]