突泉盆地突D2井林西组碎屑岩LA-ICP-MS锆石U-Pb年龄及地质意义  

LA-ICP-MS zircon U-Pb age and its tectonic significance of clastic rocks from Late Permian Linxi Formation in Tuquan Basin,Inner Mogolia

作　　者：张海华[1] 张健[1] 黄欣[1] 于宗延 卞雄飞[1] 苏飞[1] 郑月娟[1] 张德军[1] 孙雷[1] ZHANG Haihua;ZHANG Jian;HUANG Xin;YU Zongyan;BIAN Xiongfei;SU Fei;ZHENG Yuejuan;ZHANG Dejun;SUN Lei(Shenyang Center of Geological Survey,China Geological Survey,Shenyang,Liaoning 110034,China;Team 606,Bureau of Nonferrous Geological Exploration of Jilin Province,Tonghua,Jilin 134002,China)

机构地区：[1]中国地质调查局沈阳地质调查中心,辽宁沈阳110034 [2]吉林省有色金属地质勘查局六〇六队,吉林通化134002

出　　处：《东北石油大学学报》2019年第1期10-21,108,I0001-I0002,共14页Journal of Northeast Petroleum University

基　　金：中国地质调查局项目(DD20190097);中国地质调查局项目(DD20160163)

摘　　要：内蒙古突泉盆地南部突D2井钻遇厚层的暗色泥岩,发现具有晚二叠世特征的孢粉化石。为获取精确的地层同位素年龄,对500.0m井段发育的粉砂岩进行碎屑锆石LA-ICP-MS U-Pb同位素测试分析,得到100颗锆石的谐和—近谐和年龄。结果表明:碎屑锆石按年龄和频率分布特征可以分为5组:245.0～279.0 Ma(12颗,占12%),峰值年龄为263.0 Ma;282.0～346.0Ma(48颗,占48%);355.0～531.0Ma(21颗,占21%);615.0～993.0Ma(6颗,占6%);1.022～2.163Ga(13颗,占13%,207Pb/206Pb年龄)。最小年龄段年龄的加权平均为(261.7±6.2)Ma(MSWD=0.93,12颗),与最小峰值263.0 Ma的年龄吻合,测年样品沉积时间下限为263.0 Ma,沉积时代为晚二叠世,证实突泉盆地存在林西组暗色泥岩,以及大地电磁测深剖面上存在的第二套广泛连续发育的低阻层为林西组。沉积物源具有多样性和复杂性,主体来自东北各地块,同时存在华北板块和西伯利亚板块的物源信息((1.658±0.023)、(1.877±0.016)、(1.891±0.041)、(2.163±0.011)Ga)。林西组沉积时期,华北板块与西伯利亚板块开始俯冲碰撞过程,最终闭合时间在晚二叠世之后。A geologic well TD2 was deployed in the southern part of the Tuquan Basin,and thick layers of dark mudstone were drilled.Sphale fossils of the Late Permian age were found in the mudstone.The LA-ICP-MS U-Pb isotope test was performed on the zircons from the sample TD2 500TWS of siltstone.The harmonic-near harmonics and ages of the 100 zircons were obtained and cited.The 100 detrital zircons can be divided into five groups according to age and frequency distribution characteristics: 245.0~279.0 Ma( n =12,ca.12%) with peak age at 263.0 Ma,282.0~346.0 Ma( n =48,ca.48%),355.0~531.0 Ma( n =21,ca.21%),615.0~993.0 Ma( n =6,ca.6%),1.022~2.163 Ga( n =13,ca.13%, 207 Pb/ 206 Pb age).The weighted average age for the youngest age group is (261.7±6.2) Ma(MSWD=0.93, n =12),which coincided with the minimum peak age of 263.0 Ma.It was speculated that the maximum depositional age of the Linxi Formation is 263.0 Ma.Combined with paleontological fossil data,it indicates that the sedimentary age should be the Late Permian,which confirms the existence of thick layered dark mudstones in the Tuquan Basin.It is also proved that the second set of widely-developed conductive layers on the magnetotelluric survey profile is the Linxi Formation,which is great significance for the deep-seated oil and gas geological exploration in the northeast.The detrital zircon age spectrum value indicates the diversity and complexity of its sediment source,the main body should come from all over the northeast,and there are provenance information of North China plate and Siberian plate((1.658±0.023),(1.877±0.016),(1.891±0.041),(2.163±0.011) Ga),suggesting that the North China plate and the Siberian plate may begin the subduction collision process during the deposition period of the Linxi Formation.The peak age of the youngest group of detrital zircons obtained this time is 263.0 Ma,indicating that the final closing time of the North China plate and the Siberian plate should be after the Late Permian.

关 键 词：突泉盆地 林西组 低阻层 U-PB同位素 晚二叠世 地质意义 

分 类 号：TE121.1[石油与天然气工程—油气勘探] P618.13[天文地球—矿床学]