【摘要】 震旦系陡山沱组沉积期形成的黔中开阳、瓮安富磷矿沉积区,矿石产量大、品位高,是国内外重要的磷矿资源产区。黔中磷矿主要分布于黔中古陆周缘的滨浅海环境中,矿石类型以碎屑状磷块岩为主,间夹原生泥晶磷块岩、生物结构磷块岩和次生土状结构磷块岩。开阳式高品位磷块岩的动态沉积成矿过程通常为"三阶段成矿":第一阶段为初始成磷作用阶段,在新元古代大规模成磷背景下,上升洋流携带深部富磷海水进入滨浅海地区,并通过生物化学作用使磷质聚集并形成原生磷块岩沉积;第二阶段为簸选成矿作用阶段,高能波浪、风暴水流对原生磷块岩持续的破碎、磨蚀、搬运和再沉积过程中,簸选去除了原生沉积物中的陆源细碎屑、砂泥质成分,保留并聚集磷质碎屑颗粒,形成品位较高的碎屑状矿石;第三阶段为淋滤作用阶段,海平面升降变化使之前形成矿石受暴露事件影响,遭受强烈的风化淋滤作用,碎屑状磷矿石内的碳酸盐岩胶结物和白云石条带被淋滤运移,导致矿层发育大量溶蚀孔洞,甚至形成土状磷块岩,矿石品位再次得到大幅度提升。三阶段成矿作用随古地理条件和海平面变化在沉积成岩过程中多期次、动态进行,最终形成工业价值极高的磷矿石。更多还原

【Abstract】 The Kaiyang and Weng’an phosphate-rich depositional district that developed in central Guizhou Province during the depositional period of Sinian Doushantuo Formation has high ore yield and P2 O5 grade and is the phosphorite one of the most important phosphate resources region in the world. The phosphorites deposits of central Guizhou Province developed along the shallow-water margin of Qianzhong Oldland. These phosphatic beds are predominantly composed of reworked clastic phosphorites interbedded by pristine phosphatic marls,biogenetic phosphorite and diagenetic unconsolidated phosphorite. The dynamic sedimentary and mineralization process of the Kaiyang-type high-grade phosphorite could be called three stages mineralization process. The first stage is the pristine phosphogenesis: Upwelling of the bottom waters might have brought P-enriched waters to the shallow photic zone,stimulating the supersaturation of phosphate in seawater through the bio-chemical dynamism and then the precipitation of francolite. The second stage is the winnowing and reworked process: The syndepositional wave-and storm-induced erosion,winnowing and reworking continuously restructured pristine phosphatic facies and removed the lighter terrigenous grains,forming assemblages of economic granular phosphorites. The last stage is the exposing and leaching process: The exposure event caused by the sea-level fall led to weathering and leaching of phosphatic successions,the slightly acidic meteoric water dissolved carbonate minerals and created carbonaterich solutions which travelled through subsurface drainage,resulting in secondary enrichment of phosphate. The three stages mineralization process regulated by the palaeogeography and frequent sea-level changes dynamically and repeatedly worked on the phosphate deposits,finally forming the high-grade and economically significant phosphate ores.更多还原