黔西古陆相沉积型稀土资源成矿特征与潜力^*

Mineralization characteristics and resource potential of ancient terrestrial sedimentary rare earth in western Guizhou Province,China

摘要

贵州西部(黔西)稀土含矿岩系广泛出露于峨眉山玄武岩组(P_2-3em)与上覆上二叠统宣威组(P₃x)/龙潭组(P₃l)接触不整合界面上,地理分布在赫章—六盘水—盘州一线以西。沉积环境整体属于陆相冲积平原相,稀土矿主要形成于物源补给充分的陆相山前湖泊相环境。矿体主要产于含矿岩系中部高岭石伊利石层段,矿体厚0.55~2.83m,平均厚1.42m;稀土含量一般在0.19%~0.50%之间,平均在0.37%以上,具有轻稀土富集、重稀土亏损的特点,且富含高价值关键稀土元素镨、钕、铽、镝。稀土资源主要经历了峨眉山玄武岩喷溢物源形成阶段、风化淋滤初始富集阶段、搬运沉积成矿阶段、间歇性暴露淋滤再富集阶段4个成矿阶段过程。矿床形成受古地理、沉积环境、物源补给等条件复合限制,古陆湖沼相是稀土元素富集成矿的优势相区,是下一步该类型稀土找矿潜力所在地。

Abstract

The rare earth ore-bearing rock series in western Guizhou Province are widely exposed at the unconformity interface between the Emeishan Basalt Formation(P_2-3em)and the overlying Permian Xuanwei Formation(P₃x)/Longtan Formation(P₃l),geographically distributed west of the Hezhang-Liupanshui-Panzhou line. The overrall sedimentary environment belongs to the terrestrial alluvial plain facies,and rare earth deposits are mainly formed in the terrestrial mountain-front lake facies environment with sufficient material supply. The ore body is primarily located in the middle of the kaolinite-illite layer of the ore-bearing rock series,with a thickness of 0.55 to 2.83 meters and an average thickness of 1.42 meters;The rare earth content is generally between 0.19% and 0.50%,with an average of exceeding 0.37%. It has the characteristics of light rare earth enrichment and heavy rare earth depletion,and is rich in high-value key rare earth elements praseodymium,neodymium,terbium,and dysprosium. Rare earth resources have mainly gone through four mineralization stages: the formation stage of Emeishan basalt ejecta source,the initial enrichment stage of weathering and leaching,the transport and deposition mineralization stage,and the intermittent exposure and leaching re enrichment stage. The formation of mineral deposits is limited by a combination of paleogeography,sedimentary environment,and source supply conditions. The paleoland lacustrine facies is the advantageous facies area for rare earth element enrichment and mineralization,and is the next potential area for rare earth exploration of this type.

关键词

黔西 / 古陆相 / 沉积型稀土 / 成矿规律 / 成矿特征 / 资源潜力

Key words

western Guizhou Province / ancient terrestrial facies / sedimentary rare earth elements / mineralization law / mineralization characteristics / resource potential

基金资助

*贵州省科技厅重大科技工程项目—贵州稀土、钡、氟等特色资源成矿规律与找矿预测研究(黔科合找矿战略[2022]ZD004)项目资助