贵州开阳以东震旦系陡山沱组磷矿富磷机制与“三位一体”预测找矿重大突破

Enrichment mechanism of phosphorite deposits and significant breakthrough in“Triunity Model”for ore prospecting in the Sinian Doushantuo Formation of eastern Kaiyang region,Guizhou Province

贵州开阳以东磷矿整装勘查区位处扬子陆块东南边缘,是中国富磷矿最集中分布区。通过对开阳磷矿沉积学、岩石学、地层学和古地理学综合研究认为,开阳地区磷矿成矿受黔中古陆长期剥蚀夷平形成的无障壁海岸的海滩环境控制,高品位磷块岩矿石岩相组合特征、矿物学特征和沉积规律指示了开阳磷矿动态“三阶段成矿作用”过程(即原始生物—化学成磷作用、波浪簸选(机械)成矿作用和暴露淋滤成矿作用),波浪簸选成矿作用是形成厚度大、品位高富磷矿床的主导因素。按照“三位一体”成矿地质理论,确定了以沿黔中古陆北缘开阔海滩相层状展布的磷矿体展布特征,建立了区域成矿模式和地质找矿预测模型,并圈定临滨带为富磷矿重点预测靶区,开展找矿预测。通过产—学—研联合攻关,实现了磷矿理论创新,突破了该区原有磷矿找矿理论瓶颈,成矿范围从250km^2增至1000km^2,预测资源量从0.9442×10^8t增至13×10^8t。通过部分区块的工程验证,获得估算磷矿资源量(推断量+预测量)5.4892×10^8t,尤其新增富磷矿3.57×10^8t,取得中国富磷矿找矿重大突破。

Package exploration area in the eastern Kaiyang region is located at the southeastern margin of the Yangtze block,which is the concentrated distribution area of high-grade phosphorite deposits in China.The comprehensive studies of sedimentology,petrology,stratigraphy and palaeogeography in Doushantuo phosphorite ore-bed of the Kaiyang region show that the phosphorite deposits were controlled by the open shallow coastal sedimentary environment formed by denudation and deplanation of the Central Guizhou Oldland.Phosphorite lithofacies associations,mineralogical features and sedimentary structures indicate that the phosphorites had experienced“three stages of mineralization process”in the Kaiyang region:The first pristine bio-chemical phosphogenesis stage,the second winnowing and reworking stage and the last exposure and leaching stage.The winnowing and reworking processes are the key mechanism to the formation of the thick and high-grade phosphorite.According to the“Triunity Model”metallogenic theory,the research team confirmed the bedded distribution along the open phosphatic shore in the north of the Qianzhong Oldland,constructed the metallogenic model and ore prospecting model,and determined that the shoreface is the major target area of high-grade phosphorite ore.The research team have achieved the innovation of phosphorite metallogenic theory and broke through the bottleneck of phosphorite deposits exploration by cooperating of industry-university-research,and the metallogenic range was expand from 250km2 to 1000km2 and quantity of predicted resources increased from 94.42megatons to 1.3 giga-tons.The prospection verification in the part of areas estimated the ore resources of phosphorite deposits(Inferred and predicted resources)of 548.92 megatons,especially the newly added high-grade phosphorites 357 megatons,achieving significant breakthrough of ore prediction of high-grade phosphorites in China.