摘要
川南马边地区下寒武统麦地坪组是昆阳式磷矿的重要赋矿层位,磷矿的分布受沉积古环境控制。以马边黄家坪地区麦地坪组含磷地层野外剖面实测及钻孔岩芯观察为基础,对麦地坪组沉积相特征、磷块岩特征、磷矿成因模式进行了详细研究。研究表明:黄家坪地区麦地坪组发育碳酸盐岩潮坪相沉积,可识别出潮上坪、潮间坪和潮下坪3个亚相共计6种微相类型:潮上坪包括潮上滩和潮上云坪微相;潮间坪包括潮汐水道、潮间滩、潮间灰坪;潮下坪则仅发育低能潮下坪,垂向上表现出海退-海侵的沉积演化序列。据此建立了麦地坪组海湾潮坪相沉积模式。磷块岩的富集严格受沉积相带控制,潮间坪内高能水动力的潮间滩和潮汐水道是最有利于磷块岩形成的微相环境,砂砾屑磷块岩是马边地区发育较为广泛的磷块岩类型。磷矿床的成矿模式为上升洋流将富磷海水带入到海湾潮坪环境内,受生物-化学作用使磷以胶体-化学的形式发生凝聚富集,形成半固结—弱固结的磷酸盐沉积物,后遭受水流的冲刷、破碎、搬运、簸选再次发生沉淀,经压实、固结即形成高品位的磷块岩。
The lower Cambrian Maidiping formation in the Mabian area of southern Sichuan is a crucial ore-bearing horizon for Kunyang-style phosphate ores. The sedimentary paleoenvironment controls the distribution of phosphate ore.Based on the field section measurements and borehole core observations of the phosphorus-bearing strata of the Maidiping formation in the Huangjiaping area of Mabian, the characteristics of the sedimentary phases, phosphate massifs, and the mode of phosphate ore genesis of the Maidiping formation were studied in detail. The study shows that the Maidiping formation has developed carbonate tidal flat sedimentary facies, and six micro-phases can be identified in three subphases:supratidal flat, strand flat, and subtidal flat. The supratidal flat includes supratidal beach and supratidal dolomite flat;the strand flat includes tidal channel, intertidal beach, and intertidal limestone flat;the subtidal flat is only developed with the low-energy subtidal flat, showing a sedimentary evolution sequence of sea recession and sea erosion in the vertical direction. Based on the finding, we established the bay –tidal flat depositional model in the Maidiping formation. The sedimentary facies strictly controls the enrichment of phosphorite, and the intertidal beach and tidal channel with high energy hydrodynamics in the strand flat is the most favorable environment for phosphorite formation. The sand–gravel phosphorite is the most widely developed phosphorite type in the Mabian area. The mineralization mode of phosphate deposits is that the rising ocean current brings phosphorus-rich seawater into the tidal flat environment of the bay, and the phosphorus condenses and accumulates in the form of colloid-chemical, by biological and chemical interactions, forming semi-solidified and weakly-solidified phosphate sediments, which are then subjected to water scouring, crushing,transporting, and precipitation again, and then formed into high-grade phosphate masses after compaction and consolidation.
作者
李佐强
陈敏
卢君勇
阳开龙
唐茂林
朱荣涛
LI Zuoqiang;CHEN Min;LU Junyong;YANG Kailong;TANG Maolin;ZHU Rongtao(The 207 Geological Team,Sichuan Bureau of Exploration&Development of Geology&Mineral Resources,Leshan 614000,Sichuan,China;Natural Resources Bureau of Weng'an,Weng'an 550400,Guizhou,China)
出处
《地质力学学报》
CSCD
北大核心
2023年第1期34-47,共14页
Journal of Geomechanics
基金
四川省政府性投资地质勘查项目(DZ202105)。
关键词
马边地区
麦地坪组
沉积相
磷块岩
成矿模式
Mabian area
Maidiping formation
sedimentary facies
phosphorite
metallogenic model
