沉积与特提斯地质2025，Vol.45Issue(1)：134-151,18.DOI:10.19826/j.cnki.1009-3850.2024.12010
龙门山构造带早寒武世毛家山锰矿床Ⅲ号矿体含矿岩系沉积环境与锰成矿机制
The depositional environment and manganese mineralization mechanism of the ore-bearing rock series from the No.Ⅲ ore body of the early Cambrian Maojiashan manganese deposit,Longmenshan tectonic belt
摘要
Abstract
Addressing the scientific question of the unclear mechanism of manganese enrichment and precipitation in the early Cambrian manganese deposits of the Longmenshan tectonic belt,this paper focuses on the No.Ⅲ ore body of the Maojiashan manganese deposit in this belt as the research object.Based on detailed field geological surveys and thin-section identification,a systematic total organic carbon(TOC)and elemental geochemical test was conducted to preliminarily explore the source of manganese,depositional environment,and enrichment mechanism.The study shows:(1)The ore-bearing rock series from the No.Ⅲ ore body of the Maojiashan manganese deposit belongs to the fifth member of the lower Cambrian Qiujiahe Formation,primarily composed of manganese ore layers(No.Ⅲ manganese ore body),pyrite layers,manganese-bearing siliceous dolostone,carbonaceous mudstone,siliceous rock,and dolostone.The manganese ore layer is composed of centimeter-to millimeter-scale multi-cycle manganese-rich sulfide layers and manganese-rich carbonate layers.The main ore minerals are alabandite and kutnahorite,and the main gangue minerals are pyrite framboids and quartz,with a small amount of organic matter.(2)The CIA value of the ore-bearing rock series mainly ranges from 65 to 85,indicating moderate continental weathering conditions,favorable for the migration of terrigenous manganese.However,there is a negative correlation between Al2O3 and MnO,suggesting that continental weathering is likely not the main source of manganese.In the(Cu+Co+Ni)×10-Fe-Mn,(Zr+Y+Ce)×100-(Cu+Ni)×15-(Fe+Mn)/4,Ce/Ce* vs.(Y/Ho)PAAS,Ce/Ce* vs.Nd,and Fe/Ti vs.Al/(Al+Fe+Mn)discriminant diagrams,the data pertaining to rocks and ores of the ore-bearing rock series are mainly plotted on the hydrothermal origin area or the aqueous-hydrothermal mixed area,indicating that manganese is likely derived from submarine hydrothermal input.(3)The size of pyrite framboids,as well as redox indicators such as the EFMo/EFU ratio,V/Cr ratio,and V/(V+Ni)ratio,indicate that the ore-bearing rock series formed in a bottom water environment with fluctuating suboxic-anoxic-sulfidic conditions;paleoceanic productivity indicators P and Cd indicate high paleoproductivity;TOC vs.Mo and Mo vs.Cd diagrams show that the ore-bearing rock series mainly formed in a weakly restricted upwelling environment.(4)The mechanism of manganese enrichment and precipitation is likely controlled by microbial-induced mineralization and bacterial sulfate reduction(BSR).关键词
毛家山锰矿床/早寒武世/物源分析/沉积环境/沉淀机制Key words
Maojiashan manganese deposit/early Cambrian/source of ore-forming minerals/sedimentary environment/precipitation mechanism分类
天文与地球科学引用本文复制引用
万平益,刘清强,程文斌,蔡姬敏,吴春章,陈浩,郎兴海,王川,叶小春,彭建华..龙门山构造带早寒武世毛家山锰矿床Ⅲ号矿体含矿岩系沉积环境与锰成矿机制[J].沉积与特提斯地质,2025,45(1):134-151,18.基金项目
四川省地质矿产勘查开发局局专项项目(SCDZ-KJXM202407) （SCDZ-KJXM202407）
四川省政府性投资地质勘查项目(DZ202312) （DZ202312）
中国科技部"十四五"国家重点研发计划(2022YFC2905002-4) （2022YFC2905002-4）
国家自然科学基金委员会重点项目(42230311) （42230311）
自然资源部新一轮找矿突破战略行动科技支撑项目(ZKKJ202427) （ZKKJ202427）
四川省自然科学基金重点项目(2024NSFSC1954) （2024NSFSC1954）
