刘扬, 史永升,苏嘉豪,等. 鄂尔多斯南缘铜川地区中三叠统物源和构造环境分析[J].河南理工大学学报(自然科学版)，doi:10.16186/j.cnki.1673-9787. 2025060009.

LIU Y, SHI Y S, SU J H, et al． Analysis of provenance and tectonic setting of the Middle Triassic series in the Tongchuan Area at the southern margin of the Ordos Basin [J]. Journal of Henan Polytechnic University( Natural Science) ， doi: 10.16186/j.cnki.1673-9787. 2025060009.

鄂尔多斯南缘铜川地区中三叠统物源和构造环境分析(网络首发)

刘扬1,2，史永升3，苏嘉豪1,2，刘浩1,2，赵海波1,2，孙娇鹏4

1.中煤科工集团沈阳研究院有限公司，辽宁 沈抚示范区 113122；2.重庆市地质矿产勘查开发局107地质队，重庆 401120；3. 煤矿灾害防控全国重点实验室，辽宁 沈抚示范区 113122；4.西北大学 地质学系大陆演化与早期生命全国重点实验室，陕西 西安 710069

摘要: 目的 秦岭何时隆升以及鄂尔多斯南缘三叠纪晚期物源和构造环境长期存在争议。三叠纪，鄂尔多斯盆地介于古亚洲洋和勉略洋之间，发育的厚层河湖相沉积记录了丰富的洋盆闭合、陆缘构造隆升信息。方法 以铜川漆水河剖面延长组长9段为研究对象，基于详细的野外地质资料，结合砂岩岩石学、锆石微量元素地球化学和U-Pb年代学数据，开展鄂尔多斯南缘铜川地区中三叠统物源和构造环境分析。结果 结果表明，长9段以浅湖相发育为主要特点，古水流优势方向为自北向南向。薄片镜下鉴定显示，砂岩骨架矿物平均含量石英/长石/岩屑=33/47/11，属于石英长石细砂岩；岩屑以沉积岩岩屑为主（平均8%，主要为砂岩和碳酸盐岩），其次为变质岩岩屑（平均1%，主要为多晶石英）和岩浆岩岩屑（平均2%，主要为酸性喷出岩）。迪根森图解判别指示物源来源于岩浆弧和古老基底的混合。碎屑锆石年龄分为两群，前寒武纪年龄分布在1 800 Ma ~2 000 Ma和2 300 Ma~2 600 Ma，古生代年龄为480 Ma ~200 Ma，存在430 Ma和270 Ma两个峰值，同时，缺少1 600~500 Ma年龄。铜川地区长9段物源来自北部内蒙古岩浆弧，而非南部秦岭。锆石微量元素判别显示，长9段沉积于弧相关构造环境。地壳厚度重建揭示，三叠纪中晚期内蒙古岩浆弧存在快速隆升。结论 结合已有地质资料，认为中三叠世秦岭造山带东段并未大面积隆升，或者隆升幅度不大、并未影响鄂尔多斯南缘沉积，而北侧的岩浆弧快速隆升、并向盆地内部输送了大量碎屑物质。

关键词: 鄂尔多斯南缘；中三叠世；长9段；物源分析；内蒙古岩浆弧隆升

doi: 10.16186/j.cnki.1673-9787. 2025060009

基金项目: 国家自然科学基金资助项目（42372253，42072260）

收稿日期：2025-06-05

修回日期：2025-08-13

网络首发日期：2026-01-22

Analysis of provenance and tectonic setting of the Middle Triassic series in the Tongchuan Area at the southern margin of the Ordos Basin (Online)

Liu Yang1,2，Shi Yongsheng3，Su Jiahao1,2， Liu Hao1,2， Zhao Haibo1,2，Sun Jiaopeng4

1. Shenyang Research Institute Co., Ltd., China Coal Technology and Engineering Group , Shenyang-Fushun Demonstration Zone 113122，Liaoning，China; 2. No.107 Geological Team, Chongqing Bureau of Geological and Mineral Resource Exploration and Development , Chongqing 401120, China; 3. National Key Laboratory of Coal Mine Disaster Prevention and Control, Shenyang-Fushun Demonstration Zone 113122，Liaoning，China; 4. National Key Laboratory of Continental Evolution and Early Life, Department of Geology, Northwest University, Xi’an 710069, Shaanxi，China

Abstract: Objectives When was the Qinling Orogen uplifted during Triassic, a pivotal issue that was directly related to the changing in provenance and tectonic setting of the southern Ordos, remains controversial. During the Triassic, the Ordos Basin of the western North China Block bridged the Paleo-Asian Ocean to the north and the Paleo-Tethys Mianlue Ocean to the south (present coordinates). Thick accumulation of fluvial-lacustrine sediments within the Ordos Basin recorded detailed evolution clues of the ocean closure and resulted continental margin tectonic uplift. Methods We conducted field geological investigation in sedimentology on the Chang 9 member of the Yanchang Formation at the Qishui River section in Tongchuan, as well as sandstone petrology, zircon geochemistry and U-Pb geochronology. Results Field based sedimentological study revealed that the Chang 9 Member is composed of delta facies, with paleoflow direction mostly towards the south. Petrologic observations show that the Chang 9 Member sandstones display averaged Q/F/Lt ratio of 33/47/11, being clarified to as lithic arkose. Lithic fragments are predominantly sedimentary lithic fragments (averaging 8%, primarily composed of sandstone and carbonate rocks), followed by a few of metamorphic lithic fragments (averaging 1%, dominated by polycrystalline quartz) and magmatic lithic fragments (averaging 2%, mainly acidic volcanic rocks). Provenance discriminations based on the Dickinson discriminations indicate a mixed source involving detritus from magmatic arcs and ancient basement terrains. Detrital zircon ages are categized into 2 distinct groups, an older Precambrian constitution concentrated into two distinct groups of 1800~2000 Ma and 2300~2600 Ma as well as a younger Paleozoic one of 480~200 Ma, of which 2 age peaks at 430 Ma and 270 Ma can be defined, along with paucity of 1600~500 Ma age components. New data including paleocurrent, sandstone petrology, and detrital zircon ages refer to a sediment derivation from the Neimenggu continental arc to the north, rather than a southerly provenance from the Qinling. Zircon trace element data for Triassic detrital zircons further pinpoint that the Chang 9 Member was deposited in an arc associated tectonic setting. Crustal thickness reconstruction results indicate that the Neimenggu continental arc rapidly thickened and uplifted during Middle Triassic. Conclusions In combination with known geologic data, we propose that the eastern Qinling has not yet been intensely uplifted until ca. 240 Ma during the deposition of the Chang 9 Member, in contrast to the continental arc in the north that has been intensely uplifted and fed a large volume of detrital materials to the interior Ordos Basin.

Key words: Southern Ordos; Middle Triassic; Chang 9 Member; provenance study; uplift of the Neimenggu continental arc