沉积学报2024，Vol.42Issue(2)：502-520,19.DOI:10.14027/j.issn.1000-0550.2023.009
呼伦贝尔巴彦塔拉砂砾石剖面沉积物组成和锆石U-Pb年龄
Sediment Composition and Zircon U-Pb Age of the Bayan Tara Gravel Profile in Hulun Buir,China:Indications for sedimentary environments and regional magmatic tectonic events
摘要
Abstract
[Objective]The study of the sedimentology,geochemistry and zircon U-Pb dating of sand-gravel sedi-ments is highly significant for determining stratigraphic division,river system evolution,mountain tectonic uplift his-tory and regional tectono-magmatic events.However,little is understood regarding the Hulun Buir Bayan Tara sand-gravel profile,which has restricted its stratigraphic division and in-depth understanding of the regional surface pro-cess.[Methods]For this reason,analyses of the sedimentology,heavy mineral,geochemical(macronutrients,trace and rare earth elements)and zircon U-Pb chronology were performed on this section to determine the chemical weathering characteristics and sedimentary cycles,as well as the material sources,and to explore the stratigraphic delineation attribution as well as the tectonic context and indications of regional magmatic-tectonic events.This has provided a new basis for discussion of areas of sedimentary environment and stratigraphic division and correlation.[Results]The following results were obtained.(1)The gravels are poorly sorted and rounded,and have undergone a non-weak degree of weathering,with quartzaceous material(61.2%)and tuff(34.9%)dominating the gravel compo-sition,followed by terrigenous clastics(2.6%)and rhyolite(1.3%).The heavy mineral composition is clearly domi-nated by white titanium(32.54%)and ilmenite(33.01%),followed by magnetite(12.11%),zircon-tourmaline-rutile(ZTR)(6.53%),hematite(5.47%)and anatase(1.34%),with less than 1%chlorite,rutile and garnet.There are very few,if any,unstable minerals in the sediments,indicating that they have undergone strong chemical weathering.Combined with geochemical characteristics and geomorphological evidence,the comprehensive analysis shows that the maturity of the sediment in the Bayan Tara sand-gravel profile is low,and is the product of the first weathering cycle,with moderate chemical weathering after accumulation.Comparison with the age spectrum of detri-tal zircons in the northern section of the Greater Khingan Mountains indicates that this is the provenance area.(2)Combined with macro-and micro-perspectives(heavy minerals and geochemical indicators,etc.),it is considered that the sediments of the Bayan Tala sand-gravel profile are alluvial-proluvial deposits formed in a warm,dry oxidizing environment.Combined with the new research findings,various methods(sedimentology,mineral petrology and geochronology)were integrated and analyzed and compared with the standard sections of the Baitushan Forma-tion in Longjiang county and Ping'an town at the eastern foot of the Greater Khingan Mountains.This indicated that the stratigraphic units are part of the Baitushan Group.(3)The discriminant diagram of the tectonic background indi-cates a passive continental margin,which is consistent with the fact that the Greater Khingan Mountains are located within the tectonic plate and their structure is relatively stable.Peak U-Pb ages of clastic zircons at 100-200 Ma and 250-350 Ma record multi-stage magmatic tectonic events triggered by the closure of the Paleo-Asian Ocean and subduction and retrogression of the Paleo-Pacific Ocean in the northern segment of the Greater Khingan Mountains.[Conclusions]The study provides new evidence for division and further categorization of Quaternary strata and for reconstructing regional surface processes in the Greater Khingan Mountains during the early Pleistocene.关键词
锆石U-Pb测年/地球化学/地层划分/沉积环境/白土山组/大兴安岭Key words
zircon U-Pb age/geochemistry/stratigraphic division/sedimentary environment/Baitushan Formation/Greater Khingan Mountains分类
天文与地球科学引用本文复制引用
时蕴琳,谢远云,康春国,迟云平,魏振宇,吴鹏,孙磊,汪烨辉..呼伦贝尔巴彦塔拉砂砾石剖面沉积物组成和锆石U-Pb年龄[J].沉积学报,2024,42(2):502-520,19.基金项目
国家自然科学基金项目(42171006,41871013) National Natural Science Foundation of China,No.42171006,41871013 （42171006,41871013）
