| 大兴安岭南部扎赉特旗团发村晚古生代沉积岩源区和时代限定 |
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| 引用本文：王铭乾,王涛,贾建亮,王宗起,白玉岭,蔡芃睿,吴彦佳.2020.大兴安岭南部扎赉特旗团发村晚古生代沉积岩源区和时代限定[J].地球学报,41(1):49-64. |
| DOI：10.3975/cagsb.2019.110601 |
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| 基金项目:中国地质调查局地质调查项目(编号: DD20189613; DD2019005);国家自然科学基金项目(编号: 41772233; 41772114) |
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| 中文摘要:大兴安岭南部扎赉特旗地区分布着一套晚古生代地层, 由砂岩、粉砂岩和泥岩组成, 由于缺乏古生物化石和年代学证据, 前人依据地层对比将其定为晚二叠世林西组。本次工作在详细地野外地质调查基础上, 运用锆石LA-ICP-MS U-Pb测年技术, 对三个砂岩样品(样品号: 18TF-01、18YSL-04和18XBL-01)中的碎屑锆石进行了测定, 共获得219颗碎屑锆石U-Pb年龄值, 其主要分布在243~269 Ma, 273~298 Ma, 305~339 Ma, 350~377 Ma, 445~507 Ma和754~1053 Ma六个年龄区间。其中获得最年轻的一组锆石的谐和年龄为245 Ma, 并结合区域上侵入该地层花岗岩的年龄, 限定其沉积时代可能为中三叠世。根据碎屑锆石的年龄值特征反映出该地层具有多物源供给的特点, 其中年龄为243~269 Ma的碎屑物质源区主要来自于古亚洲洋闭合及碰撞造山相关的岛弧花岗岩类; 年龄为273~298 Ma主要来自于大石寨组火山岩; 年龄为305~339 Ma可能主要来自于格根敖包组火山岩; 350~377 Ma的碎屑锆石可能源于北部大民山组火山岩; 年龄为754~1053 Ma的碎屑锆石与漠河杂岩、兴华渡口群及佳木斯微陆块中元古代的岩浆事件有关; 较古老~1800 Ma的碎屑锆石可能来自于古亚洲洋中微陆块或结晶基底。砂岩中锆石的形成年龄与地层沉积年龄较为相近, 显示出汇聚背景下的特征。因此, 综合砂岩物质组成、锆石年龄特征及弧-盆之间时空关系, 显示中三叠世该地区可能形成于汇聚背景下的弧前盆地。 |
| 中文关键词:大兴安岭南部 物源 碎屑锆石U-Pb年代学 LA-ICP-MS 中三叠世 中亚造山带 |
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| Constraints of the Provenance and Deposition Time of the Late Paleozoic Sedimentary Rocks in Tuanfa Village, Jalaid Banner, Southern Da Hinggan Mountains |
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| Abstract:A group of Late Paleozoic strata, composed of sandstone, siltstone and mudstone, is distributed in the Jalaid Banner area in southern Da Hinggan Mountains. Due to lack of paleontological fossils and chronological evidence, the previous researchers assigned it to Late Permian Linxi Formation based on stratigraphic correlation. In this study, LA-ICP-MS was used to determine the zircon U-Pb isotopes in sandstone. The detrital zircon dating results of three sandstone samples (18TF-01, 18YSL-04 and 18XBL-01) show that the ages of 219 zircon samples are mainly distributed in six ranges, i.e., 243~269 Ma, 273~298 Ma, 305~339 Ma, 350~377 Ma, 445~507 Ma and 754~1053 Ma. The weighted mean age of the youngest group zircons is 245 Ma. Combined with the age of intrusive granite, the authors hold that the maximum sedimentary age of the formation is Middle Triassic. The ages reflect the multi-source supply characteristics of the strata: 243~269 Ma detrital zircon mainly came from the volcanic activity related to the closure and collisional orogeny of the southwestern part of the Asian-Asian Ocean; 273~298 Ma detrital zircon came from the Dashizhai Formation volcanic rocks; 305~339 Ma zircon is consistent with the volcanic rocks of the Gegenyubao Formation volcanic rocks in formation time; the 350~ 377 Ma detrital zircon has the same age as the volcanic rocks in northern Damingshan Formation; the 754~ 1053 Ma detrital zircon was derived from the Proterozoic magmatism in the Mohe complex, the Xinghuadukou Group and the Jiamusi micro-blocks; the older ~1800 Ma zircon age is consistent with the age of the paleo-continental basement in the Paleo-Asian Ocean. In the sandstone samples, the crystallization age of zircon is similar to that of stratigraphic sedimentary age, implying a background of convergence. Combined with sandstone material composition, zircon age characteristics and the positional relationship between the arc and the basin, the authors hold that the strata were formed in a pre-arc basin under the convergence background during the Middle Triassic. |
| keywords:southern Da Hinggan Mountains source analysis detrital zircon U-Pb geochronology LA-ICP-MS Middle Triassic Central Asian orogenic belt |
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