豫西寒武系辛集组含磷层沉积环境及磷酸盐富集机制  

Sedimentary Environment of the Phosphorus-bearing Layers and Its Phosphate Enrichment Mechanism of the Cambrian Xinji Formation,Western Henan

作　　者：贾冰玲 张碧云 汤彬 郑德顺[1] JIA Bingling;ZHANG Biyun;TANG Bin;ZHENG Deshun(Institute of Resources and Environment,Henan Polytechnic University,Jiaozuo,Henan 454000,China)

机构地区：[1]河南理工大学资源环境学院,河南焦作454000

出　　处：《现代地质》2023年第4期858-869,共12页Geoscience

基　　金：国家自然科学基金项目(41872238,42172131)。

摘　　要：寒武纪是全球性磷酸盐沉积的重要时期,华北克拉通南缘寒武系辛集组是北方重要的含磷层位,但含磷地层与沉积环境的联系鲜有提及,磷酸盐的富集模式有待进一步研究。本文选取豫西宝丰地区辛集组中部的典型含磷层段为研究对象,进行野外宏观和室内微观观察,分析其沉积环境,探讨辛集组含磷层的磷质来源和富集机制。结果表明,辛集组磷结核为黑色,不规则扁平盘状,粒径在2 mm至2 cm范围内变化,沿层面分布在细砂岩中。磷结核的主要组成矿物为胶磷矿,具两种形态:(1)隐晶质圆形胶磷矿,内部无结构,部分发育龟裂纹;(2)微晶质鲕状胶磷矿,发育细微纹层。辛集组沉积环境为滨浅海过渡带,磷质来源于大洋深层富磷水以及小壳生物生命活动,经历了同沉积、成岩早期两个阶段,在动荡的浅水中大量沉积。与扬子克拉通寒武纪含磷岩系对比得知,含磷地层具穿时性且磷酸盐沉积发生在沉积间断后;寒武纪磷酸盐初始沉积以生物、化学作用为主,随后由沉积环境与古构造控制含磷地层经历再次富集。辛集组含磷层的研究确定了华北克拉通南缘寒武纪初期磷酸盐富集与沉积环境之间的关系,为磷酸盐大规模沉积的原因丰富了数据资料。The Cambrian is an important period for global phosphate deposition,and the Cambrian Xinji Formation is an important phosphorus-bearing sequence on the southern margin of North China Craton.However,the relationship between the phosphorus-bearing stratigraphy and the sedimentary environment is poorly understood,and the phosphate enrichment mechanism needs to be further studied.Here,we studied the middle Xinji Formation at Baofeng,which contains a typical phosphorus-bearing layer.Field observations and laboratory analyses were conducted to reveal its depositional environment and explore its phosphorus source and enrichment mechanism.The results show that phosphorus nodules from the Xinji Formation are black,irregular flat disk-shaped,with size of 2 to 20 mm,and are distributed in the fine sandstone beds.Collophanite is the main mineral in the nodules.There are two forms:(1)cryptocrystalline rounded colloidal phosphorite with no internal structure and locally cracked;(2)microcrystalline oolitic colloidal phosphorite with fine veins.The depositional environment of the Xinji Formation was likely littoral-shallow marine transition.Phosphorus was likely derived from deep oceanic phosphorus-rich water and small shell biological activities.Formation of the phosphorus nodules was likely dominated by chemical deposition with indirect biological involvement.It has undergone syn-deposition and early diagenesis stages,and large amounts of phosphorus nodules were deposited in turbulent shallow water.Compared with the Cambrian phosphorus-bearing facies in the Yangtze Craton,the phosphate-bearing stratigraphy is clearly diachronic,and phosphate deposition occurred after the sedimentary hiatus.Initial deposition of the Cambrian phosphate was dominated by biological and chemical processes,and then the depositional environment and paleotectonics controlled the phosphorus-bearing stratigraphy and promoted the re-enrichment.We point out the relationship between phosphorus enrichment and the Early Cambrian sedimentary environment in th

关 键 词：华北克拉通南缘 辛集组 含磷层 沉积环境 富集机制 

分 类 号：P534.41[天文地球—古生物学与地层学]