四川盆地北缘下志留统龙马溪组重晶石发育特征及其地质意义  

Development Characteristics and Geological Significance of Barite in the Longmaxi Formation of the Lower Silurian in the Northern Margin of the Sichuan Basin

作　　者：肖斌 郭东旭 王浩 熊姝臻 富向 赵忠海 李胜 Xiao Bin;Guo Dongxu;Wang Hao;Xiong Shuzhen;Fu Xiang;Zhao Zhonghai;Li Sheng(College of Mining,Liaoning Technical University,Fuxin 123000,Liaoning,China;College of Environmental Science and Engineering,Liaoning Technical University,Fuxin 123000,Liaoning,China;Department of Resources,Liaoning Geology Engineering Vocational College,Dandong 118000,Liaoning,China)

机构地区：[1]辽宁工程技术大学矿业学院,辽宁阜新123000 [2]辽宁工程技术大学环境科学与工程学院,辽宁阜新123000 [3]辽宁地质工程职业学院资源系,辽宁丹东118000

出　　处：《吉林大学学报（地球科学版）》2024年第4期1137-1153,共17页Journal of Jilin University：Earth Science Edition

基　　金：国家自然科学基金项目(52174117,42274129);辽宁省自然科学基金项目(2022-BS-328);辽宁工程技术大学学科创新团队项目(LNTU20TD-14,LNTU20TD-30)。

摘　　要：扬子板块北缘志留系黑色岩系中重晶石-毒重石成矿带的形成构造背景和成矿过程一直受到众多学者的关注。本文选择四川盆地北缘城口月亮坪剖面下志留统龙马溪组泥页岩中的重晶石矿物为研究对象,从岩石学、矿物学入手探讨重晶石发育特征,并结合锶同位素分析重晶石的成因及其反映的地质意义。结果显示:重晶石主要发育成岩作用为主的针状晶体、冷泉作用为主的较大粒径溶蚀状晶体、热液作用为主的树枝状晶体,以及生物作用为主的小粒径椭球体形晶体;重晶石结核以扁椭球体形顺层分布,存在同心分层结构、致密均一结构、龟裂纹充填结构,其成因以成岩作用为主,局部出现后期热液流体充填收缩缝形成的龟裂纹;层状重晶石的^(87)Sr/^(86)Sr值为0.7084,反映其形成过程受到深部幔源(低^(87)Sr/^(86)Sr值)和围岩(高^(87)Sr/^(86)Sr值)的混染作用,推测其成因为深部幔源热液与冷泉(或成岩作用)共同作用的结果。研究认为:四川盆地北缘龙马溪组沉积时期为一个具有拉张构造背景的被动大陆边缘,在北大巴山发育同沉积断裂;在龙马溪组早期四川盆地北部斜坡区受到弱的拉张作用,断裂发育规模不大,形成间歇性小规模的冷泉渗流;在龙马溪组晚期拉张作用增强,断裂加深,产生重晶石黑烟囱,大量含Ba^(2+)和H2S的热液进入海水中并在北大巴山地区形成重晶石矿床。The formation tectonic background and mineralization process of the barite-witherite mineralization belt in the Silurian black rock series on the northern margin of the Yangtze plate have always been the focus of many scholars.This article selects the barite minerals in the mud shale of the Longmaxi Formation in the Lower Silurian of the Yueliangping section at the northern margin of the Sichuan basin as the research object.Starting from petrology and mineralogy,the development characteristics of barite are discussed,and the genesis of barite and its geological significance are analyzed by combining strontium isotopes.The results show that barite mainly develops into acicular shaped crystals dominated by diagenesis,larger particle size dissolution shaped crystals dominated by cold methane seeps,dendritic crystals dominated by hydrothermal processes,and small particle size ellipsoidal crystals dominated by biological processes.The barite nodules are distributed along the layers with oblate ellipsoid shape,with a concentric stratification structure,dense homogeneity structure,and turtle-crack filling structure.The genesis is mainly diagenesis,and local late hydrothermal fluid filling shrinkage cracks form turtle-cracks.The ^(87)Sr/^(86)Sr value of layered barite is 0.7084,indicating that its formation process was influenced by the mixing effect of the deep mantle sources(low ^(87)Sr/^(86)Sr value)and the host rocks(high ^(87)Sr/^(86)Sr value).It is speculated that its formation was the result of the joint action of deep mantle derived hydrothermal fluids and cold methane seeps(or diagenesis).Research suggests that the sedimentary period of the Longmaxi Formation on the northern margin of the Sichuan basin was a passive continental margin with an extensional tectonic background,and synsedimentary faults developed in the North Dabashan.In the early stage of the Longmaxi Formation,the northern slope area of the Sichuan basin was subjected to weak extension,and the scale of fault development was not large,forming inter

关 键 词：黑色岩系 重晶石 锶同位素 冷泉 龙马溪组 四川盆地 钡 

分 类 号：P571[天文地球—矿物学] P578.71[天文地球—地质学]