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滇东北镇雄羊场磷矿区下寒武统梅树村组沉积环境及富集成矿机制

Sedimentary environment and enrichment mineralization mechanism of the Lower Cambrian Meishucun Formation in the Yangchang phosphate deposit of Zhenxiong area,Northeastern Yunnan
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摘要 羊场超大型磷矿床是新近勘查发现的大埋深全隐伏浅海相碳酸盐岩型层状磷块岩矿床,赋矿地层为下寒武统梅树村组(?1ms),目前对其沉积环境和富集成矿机制认识薄弱。本文在代表性钻孔岩芯系统观测的基础上,利用沉积(微)相分析、矿物学及矿物化学示踪等手段,重点解析梅树村组各岩性段的岩石矿物(组合)特征、沉积(微)相类型及其时空分布规律,查明沉积环境演化,探究磷质来源、迁移及富集机制,建立其成矿模式。对比分析表明,赋矿地层垂向上表现出海侵-海退序列的近岸潮坪相沉积环境,识别出潮上坪、潮间坪和潮下坪3个亚相6种微相,潮上坪分为潮上滩、潮上灰坪,潮间坪分为潮间灰坪、潮间滩、风暴流,潮下坪发育低能潮下坪;潮间坪中的高能潮间滩是最有利的磷块岩形成环境,长期保持的浅水环境下多期次潮汐、波浪反复作用,利于富磷粒屑的簸选富集与再造,从而形成矿区北西侧矿层富厚、南东侧渐趋薄贫的磷块岩矿床。由此,羊场磷矿床的成矿作用可分为3个阶段:初始堆积沉淀成矿阶段(上升洋流携带的磷质来源)、生物化学凝聚沉淀与加积异化成矿阶段(微生物分解、转化及复合作用驱动的迁移与富集成矿)、簸选富集与再富集成矿阶段(多期次波浪、潮汐作用驱动的沉淀再次富集成矿)。这为矿区及外围地区找矿勘查提供了重要依据。 The Yangchang phosphate deposit is a large-buried shallow marine carbonate stratified phosphorite deposit discovered in the Meishucun Formation(ε1 ms)of the Lower Cambrian recently.The understanding of its sedimentary environment and enrichment mechanism is still limited.Representative borehole cores were selected to carry out systematic sedimentary facies cataloguing.By means of sedimentary(microfacies)analysis,mineralogy and mineral chemistry tracing,the characteristics of rock and mineral(assemblage),sedimentary(microfacies)types,sedimentary environment and spatial and temporal distribution of each lithologic section of the Meishucun Formation are analyzed.We also studied the sedimentary environment evolution,the source,migration and enrich-ment mechanism of phosphorus,and its metallogenic model.The comparative analysis shows that the ore-bearing strata exhibits the nearshore tidal flat facies sedimentary environment with transgression-regressive sequence verti-cally,6 microfacies types in 3 subfacies namely supratidic flat,intertidal flat and subtidal flat are identified.Su-pratidic flat is divided into supratidic flat and supratidic carbonate flat.The intertidal flat is divided into intertidal carbonate flat,intertidal flat and storm current.The subtidal flat developed a low energy subtidal flat.The favora-ble phosphorus formation environment is the high energy intertidal flat in intertidal flat.Repeated action of tides and waves in the shallow water environment for a long time is conducive to the winnowing,enrichment and reconstruc-tion of phosphorous rich particles,thus forming a phosphorous rock deposit with rich and thick beds in the north-west and poor and thin beds in the southeast of the mining area.To sum up,the ore forming process of the Yangchang phosphate deposit can be divided into three stages,namely:①initial accumulation and precipitation mineralization stage(phosphorus source carried by upwelling ocean current);②biochemical deposition and accre-tion mineralization stage(migration and enrichment driven by microbial decomposition,transformation and com-pound);③winnowing enrichment and re-enrichment mineralization stage(precipitation and enrichment driven by multi-stage wave and tidal action).This new points provides an important basis for prospecting and exploration in the mining area and peripheral areas.
作者 米云川 杜斌 夏建峰 王枫 周骞 黄太平 胡清华 MI Yun-chuan;DU Bin;XIA Jian-feng;WANG Feng;ZHOU Qian;HUANG Tai-ping;HU Qing-hua(Yunnan Institute of Geological Survey(Yunnan Institute of Geological Sciences),Kunming 650216,China;Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,Ministry of Natural Resources,Kunming 650051,China;Yunnan Key Laboratory of Sanjiang Metallogeny and Resources Exploration and Utilization,Kunming 650051,China;Faculty of Land Resource Engineering,Kunming University of Science and Technology,Kunming 650093,China)
出处 《岩石矿物学杂志》 CAS CSCD 北大核心 2024年第5期1099-1118,共20页 Acta Petrologica et Mineralogica
基金 云南省地质勘查基金项目(D202001,K202101,Y202301,K202301)。
关键词 梅树村组 羊场背斜 沉积环境演化 成矿机制 磷块岩矿床 羊场磷矿 镇雄地区 滇东北 Meishucun Formation Yangchang anticlinal sedimentary environment evolution metallogenic model phosphorite deposit Yangchang phosphate deposit Zhenxiong area Northeast Yunnan
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