库车坳陷北部山前带中生界泥岩元素地球化学特征及其沉积环境意义

梁万乐; 李贤庆; 魏强; 李谨; 孙可欣; 和钰凯; 张亚超

库车坳陷北部山前带中生界泥岩元素地球化学特征及其沉积环境意义

Element geochemical characteristics of Mesozoic mudstones in the northern piedmont zone of the Kuqa depression and their implications to sedimentary environments

摘要

摘要: 应用元素地球化学方法,对库车坳陷北部山前带中生界三叠系和侏罗系泥岩的主量元素、微量元素和稀土元素(REE)特征进行了研究,并探讨了其沉积环境意义。结果表明:库车坳陷北部山前带中生界泥岩主要为陆相淡水沉积,稀土元素具有轻稀土富集特征,稀土元素总量反映有机质快速堆积、陆源细碎屑补给速度慢的沉积特征。从三叠纪到侏罗纪古盐度略有上升,古气候以温暖湿润为主,整体处于贫氧—缺氧环境。黄山街组沉积时期温暖湿润的气候与较低的古盐度有利于有机质的形成,贫氧—缺氧环境提供保存条件。至恰克马克组沉积时期古气候开始向干燥炎热转化, 且古盐度较高,影响有机质产量,但缺氧环境更有利于其保存。

Abstract: Bymeansofelementgeochemistry,thecharacteristicsofmajorelements,traceelementsand rareearthelements(REE)forTriassicandJurassicmudstonesfromthenorthernpiedmontzoneinthe Kuqadepressionwerestudiedanddiscussedfortheimplicationsfosedimentryenvironment.TheMesozoicmudstonesfromthenorthernpiedmontzoneintheKuqadepressionaredominentlyterrestrialfreshwatersedimentaryenvironments.REE arecharacterizedbyenrichmentoflightREE,andreflect the
sedimentarycharacteristicsofrapidaccumulationoforganicmatterandslowrechargeofterrigenousfine debris.FromtheTriassictotheJurassic,thepaleosalinityincreasedslightlywhilethepaleoclimatewas mainlyhumid,andthewholewasunderdysoxic-anoxicconditions.Thewarmandhumidpaleoclimate andlowerpaleosalinityduringthedepositionoftheHuangshanjieFormationareconducivetotheproductionoforganicmatterproductivity,andthedysoxic-anoxicconditionprovidespreservationconditions.Thehot-drypaleoclimateenvironmentbegantoappearintheperiodoftheQiakemakeFormation, andthehigherpaleosalinitymaypromotetheformationoforganicmatter,buttheanoxicconditionis moreconducivetoitspreservation.

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