古地理学报2018，Vol.20Issue(2)：271-284,14.DOI:10.7605/gdlxb.2018.02.020
新疆阿合奇地区志留系砂岩地球化学特征及大地构造背景
Geochemical characteristics and tectonic history of the Silurian sandstones in Akeqi area, Xinjiang
摘要
Abstract
The South Tianshan Orogenic Belt is located between the Tarim Plate and Yili-Central Tianshan Plate.The tectonic evolution of the South Tianshan Ocean in the Paleozoic has long been debated.Litho-geochemical features of the major and trace elements of the Silurian sandstones from Akeqi area,northwestern margin of the Tarim Plate of Xinjiang,show that Chondrite-normalized REE distribution patterns of the samples are all right skewed,with high (La/Yb) N value,low δEu value,and negative Ce anomaly.The maturity of the sandstones from the Middle to Top Silurian Tataertage Formation is higher than the samples from the Lower Silurian Kepingtage Formation.The provenance and tectonic setting of the sandstones were evaluated using ternary diagrams that highlight their geochemical characteristics.The results suggest that the provenance of the Akeqi area gradually transformed from active provenance to stable provenance.Some sediments from the Kepingtage Formation are sourced from active continental margin and continental island arc,indicating felsic igneous provenance;Sediments from the Tataertage Formation were sourced from quartzite sediment provenance of mature continent.Combined with widely distributed parallel unconformities between the Ordovician and the Lower Silurian,it can be inferred that the Akeqi area was located in an active continental margin,the South Tianshan Ocean subducted southward beneath the Tarim Plate shortly during the Late Ordovician,which provided the active provenance for the study area.From the Early Silurian,as southwards subduction ended,the tectonic setting of Akeqi area transformed from active continental margin to stable passive continental margin.Sediments from active and stable provenances gradually decreased and increased,respectively.During the deposition of Middle to Top Silurian succession,tectonic setting of the Akeqi area completely transformed to stable passive continental margin,so that sediments were exclusively sourced from stable provenances.In conclusion,this study proposes that bidirectional subduction was developed during the evolution of the South Tianshan Ocean within the Paleozoic.关键词
新疆/阿合奇地区/志留系/南天山洋/双向俯冲/活动大陆边缘Key words
Xinjiang/Akeqi area/Silurian/South Tianshan Ocean/bidirectional subduction/active continental margin分类
天文与地球科学引用本文复制引用
陈小双,吕奥,宋贺民,刘磊,杨宝忠,侯红星..新疆阿合奇地区志留系砂岩地球化学特征及大地构造背景[J].古地理学报,2018,20(2):271-284,14.基金项目
中国地质调查局地调协作项目“新疆柯坪地区晚古生代地层综合研究”(编号:2015010038)资助.Financially supported by the Geological Survey Collaboration Projects of China Geological Survey Bureau "Comprehensive Research of Late Paleozoic Strata in Kalpin Region,Xinjiang" (No.2015010038) （编号:2015010038）
