贵州织金新华戈仲伍组含磷岩系沉积环境对成磷作用的制约  

Constraints of sedimentary environment on phosphorization of phosphorus-bearing rock series in the Xinhua Gezhongwu Formation,Zhijin County,Guizhou Province

作　　者：汪宇航 谢宏[1,2] 张兰 王昌建 卢正浩 白洋 王孟斋 Wang Yuhang;Xie Hong;Zhang Lan;Wang Changjian;Lu Zhenghao;Bai Yang;Wang Mengzhai(College of Resource and Environmental Enginerring,Guizhou University,Guiyang 550025;Key Laboratory of Karst Georesources and Environment of Ministry of Education,Guizhou University,Guiyang 550025,China;School of Earth Sciences,Lanzhou University,Lanzhou 730000,China)

机构地区：[1]贵州大学资源与环境工程学院,贵阳550025 [2]贵州大学喀斯特地质资源与环境教育部重点实验室,贵阳550025 [3]兰州大学地质科学与矿产资源学院,兰州730000

出　　处：《地质科技通报》2023年第6期201-214,共14页Bulletin of Geological Science and Technology

基　　金：国家自然科学基金项目(42062009);贵州省科技计划项目(黔科合基础[2020]1Y158);贵州大学引进人才科研项目(贵大人基合字[2015]第37号)。

摘　　要：贵州织金新华早寒武世超大型富稀土磷矿床属于典型的海相沉积型矿床,长期以来,对其成矿环境及成矿机制的认识尚存在分歧。在重点研究含磷岩系岩(矿)石显微特征的基础上,结合元素地球化学证据,求证了戈仲伍组含磷岩系沉积环境及其形成机制,丰富了扬子陆块同类型矿产的研究资料。该含磷岩系从下到上,矿石结构构造发生了规律性的变化:颗粒稍变细;粒间填隙物由以亮晶白云石胶结物为主变为硅质、胶磷矿等泥晶基质,再变为以亮晶白云石胶结物为主,最后变为泥晶胶磷矿、硅质等;胶结方式由以孔隙式胶结为主转换为孔隙式-基底式胶结,支撑类型由颗粒支撑变化为颗粒-杂基支撑;岩层单层厚度变薄,颜色变深,交错层理变得不发育;反映含磷岩系沉积于强水动力的潮下带,上部沉积水体较下部有所加深、水动力条件稍变弱。含磷岩系显著的Ce负异常(δCe介于0.32~0.39)、较低的Ni/Co比值(0.98~6.07)和V/Cr比值(0.57~12.50),表现出沉积水体具有与现代海洋环境相似的氧化特征;较低的10^(3)·Sr/Ca比值(2.00~3.38)及1/Σ(Al_(2)O_(3)+TiO_(2))比值(0.57~3.45)说明古水深总体较浅,但变化频繁;Fe,Cu,Ba含量分布特点指示下部碳酸盐古生产力比上部高。在各种条件耦合的古环境中,磷块岩经历沉淀-冲搅-颠选-胶结-固结作用最终富集形成。The Early Cambrian superlarge rare earth-rich phosphate deposit in Xinhua,Zhijin County,Guizhou Province,is a typical marine sedimentary deposit.There have long been controversial on the mineralisation environment and mineralisation mechanism.In this paper,the sedimentary environment and formation mechanism of the phosphorus-bearing rock series in the Gezhongwu Formation are verified,through the study of the microscopic characteristics of phosphorus-bearing rock series rocks or ores and the evidence of elemental geochemistry.This study reveal the regular changes in the structure of phosphorite from the bottom up of the phosphorous-bearing rock series:the grain sizes decreasing;the interstitial materials between grains vary from bright dolomite cement to micritic matrix,such as siliceous and collophanite,followed by bright dolomite cement and finally micrite collophanite and siliceous.The cementation mode has mainly converted from pore cementation to pore-based cementation,and the supports change from grain to grain-matrix supports.Moreover,the single layers of the rocks become thinner and darker,and the development of staggered bedding was decreased.These characteristics reflect that the sedimentary environment of the phosphorus-bearing rock series is a subtidal zone with strong hydrodynamic forces,and of the upper section has sedimentary depths higher and hydrodynamic conditions slightly weaker than those of the lower section.The significant negative Ce anomalies(δCe between 0.32-0.39)and low Ni/Co(0.98-6.07)and V/Cr ratios(0.57-12.50)of the phosphorus-bearing rock series show that the sedimentary water had oxidation characteristics similar to those of a modern marine environment.The lower 10^(3)·Sr/Ca(2.00-3.38)and 1/Σ(Al_(2)O_(3)+TiO_(2))ratios(0.57-3.45)indicate that the ancient water depth was generally shallow,but the relative depth changed frequently.The distribution characteristics of Fe,Cu and Ba contents indicate that the palaeoproductivity of carbonate in the lower section is higher than that in the

关 键 词：含磷岩系 沉积结构构造 地球化学 贵州织金 

分 类 号：P619.2[天文地球—矿床学]