摘要
贵州威宁地区宣威组底部稀土含矿岩系的成因类型一直有较大争议.在野外实地调查的基础上,运用矿物学、岩相古地理与地球化学等手段进行了系统性研究.结果显示,区内二叠系宣威组底部稀土含矿岩系广泛分布,连续性好,含矿段厚度为2~16 m,并伴生有铌、锆、镓等元素;稀土氧化物平均品位0.15%,最高可达1.60%.主量、微量和稀土元素分析表明威宁地区稀土含矿岩系中含有来自玄武岩及火山灰的典型矿物,稀土配分模式与玄武岩相比具有继承性,研究区化学风化作用较强、成分成熟度较高代表其经过长距离搬运,遭受了改造;峨眉山玄武岩为该稀土层提供了主要物质来源,稀土层受源岩成分的控制,经历了沉积分选及再循环作用,还遭受了来自上地壳的中酸性岩浆物质源区的混染.其成因机制可能为在晚二叠世炎热、潮湿、强风化的环境中,玄武岩经过风化剥蚀后,搬运至沉积基底低洼处的三角洲平原亚相中的洪泛平原微相环境,与火山灰一同沉积沉淀,在风化和淋滤作用下稀土等元素以离子形式被解析出来,从而被吸附性强的高岭石等黏土矿物吸附于表面,或进入矿物晶格,形成富稀土层.
The genetic types of the rare earth ore-bearing rocks at the bottom of Xuanwei Formation in Weining area, Guizhou Province are controversial. In order to clarify the genetic mechanism and concentration regularity, through field investigation combined with mineralogy, lithofacies paleogeographic features and geochemistry, systematic research has been carried out. The results show that the rare earth ore-bearing rocks at the bottom of the Xuanwei Formation of Permian are widely distributed with good continuity and the thickness of ore-bearing sections varies from 2 to 16 m, and associated with niobium, zirconium, gallium and other elements. The average grade of rare earth oxide element is 0.15%, and the highest grade is up to 1.6%. The analyses of major, trace and rare earth elements shows that the rare earth ore-bearing rocks in Weining area contain typical minerals from basalt and volcanic ash, the rare earth element distribution patterns are inherited from basalt. The chemical weathering in the study area is stronger, and the higher maturity of the ingredients means that it has been transformed after being transported for a long distance. The Emeishan basalt provides the main material source for the rare earth layer. The rare earth layer is controlled by the composition of the source rock, has undergone sedimentary separation and recycling, and has suffered from the mixing of intermediate-acid magmatic material source region from the upper crust.The genetic mechanism is suggested as that the basalt was weathered and denuded in the hot, humid and strongly weathered environment during the Late Permian, after weathering and denudation, the basalt was transported to the flood plain microfacies in the delta plain subfacies between the volcanic depressions,and deposited with the volcanic ash. Under weathering and leaching, the rare earth elements were resolved as ions, and then they were adsorbed on the surface of clay minerals such as kaolinite with strong adsorption ability, or entered into the crystal lattice to form the rare-earth rich layer.
作者
田恩源
龚大兴
赖杨
邱小龙
谢华
田康志
Tian Enyuan;Gong Daxing;Lai Yang;Qiu Xiaolong;Xie Hua;Tian Kangzhi(Institute of Multipurpose Utilization of Mineral Resources,Chinese Academy of Geological Sciences,Chengdu 610041,China;Technology Innovation Center of Rare Earth Resources Development and Utilization,China Geological Survey,Chengdu 610041,China;113 Geological Team of Guizhou Geology and Mineral Bureau,Liupanshui 553000,China;Sichuan Institute of Nuclear Industry Geology,Chengdu 610052,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu 610059,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2021年第8期2711-2731,共21页
Earth Science
基金
中国地质调查局地质调查项目(No.DD20189507-01)。
关键词
威宁
稀土
沉积型
岩相古地理
成矿模式
成因机制
Weining
rare earth element
sedimentary
lithofacies paleogeography
metallogenic model
genetic mechanism
