敦化盆地土门子组砂岩地球化学特征及其地质意义

来源期刊:中南大学学报(自然科学版)2015年第3期

论文作者:刘招君 徐进军 孟庆涛 胡菲 孙平昌 程丽娟 宋宇

文章页码:1006 - 1016

关键词:敦化盆地;土门子组;沉积地球化学;物源属性;大地构造背景;物源分析

Key words:Dunhua Basin; Tumenzi Formation; sedimentary geochemistry; provenance attribute; geotectonic background; analysis of provenance

摘    要:为研究敦化盆地新近系土门子组砂岩的源岩属性和源区大地构造背景,对其进行系统取样,并通过地球化学和镜下研究分析。研究结果表明:土门子组砂岩稀土元素具有轻稀土富集(w(LREE)为51.00~278.31 μg/g),重稀土平坦(w(HREE)为14.27~79.38 μg/g),较明显的Eu(平均w(δEu)为0.84)负异常等特征,而微量元素没有显著的均一化,表明土门子组源岩未经沉积再循环作用,属于短距离搬运堆积,且源岩主要为来自上地壳的长英质岩。结合砂岩地球化学特征与砂岩Dickinson图解及区域地质的研究判断认为,土门子组砂岩具有多个物源,其源区主要形成于印支运动晚期活动大陆边缘构造背景下的再旋回造山源区和基底隆起区,源岩主要来自于晚三叠世~早中侏罗世的长英质火山岩和侵入岩,而少量可能来自于晚二叠世的变质岩和残余白垩纪及古近纪的沉积岩。

Abstract: The Dunhua Basin is located in the middle of Dun Mi fracture belts, and the Neogene mainly develops the Tumenzi Formation. Systematic sampling was made and sandstone of the Tumenzi Formation in the Dunhua Basin was analyzed. The results show that the rare earth elements of sandstone possess characteristics as follows: light rare earth elements enrichment (w(LREE) is 51.00-278.31 μg/g), height rare elements flat (w(HREE) is 14.27-79.38 μg/g) and more obviously negative europium anomalies (average w(δEu) is 0.84). However, the race elements have no remarkable homogenization. All indicate that the source rocks of sandstone were carried and accumulated in short distance which mainly came from felsic rocks of the upper crust without experiencing deposition and recycling. Through the judgment combined with the geochemical characteristic, Dincksion diagram of sandstone and the study of regional geology, sandstone of the Tumenzi Formation has several provenances, and source region majorly was formed in the recycled orogeny and basement uplifted provenances under the tectonic background of active continental margin at the end of the indo-china movement. Source rocks mostly came from felsic volcanic rocks and intrusive rocks during the late Triassic to early-middle Jurassic, with a little probably from metamorphic of the Late Permian and sedimentary rocks of the residual Cretaceous and Paleogene.

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