瓮安埃迪卡拉系灯影组叠层石磷块岩形成环境及成矿机制

瓮安地区埃迪卡拉系灯影组叠层石磷块岩是瓮安-福泉磷矿区新发现的含磷层位。磷块岩以典型的叠层石构造为主 要特征，呈透镜状生物礁（藻礁）形式产于灯影组顶部。叠层石磷块岩的矿物组成主要为磷酸盐矿物及碳酸盐矿物；白色 纹层富含磷酸盐矿物，而暗色纹层磷酸盐矿物含量较低，主要为碳酸盐矿物。通过对叠层石磷块岩矿物学及地球化学特征 进行研究，提出灯影组叠层石磷块岩属于潮下带半局限环境叠层石礁，是大量藻类通过生物或生物化学作用，将海水中磷 质富集-沉淀而形成磷质柱状叠层石礁；磷酸盐的矿化主要发生在沉积物-海水界面弱碱性次氧化环境，藻类在磷块岩形成 过程中起重要作用。

Sedimentary Environment and Mineralization Mechanism of the Stromatolitic Phosphorite in the Ediacaran Dengying Formation,Weng'an County of Guizhou Province,China

Stromatolitic phosphorite in the Ediacaran Dengying Formation was initially discovered in Weng′an-Fuquan area of SouthwesternGuizhouProvince,Chinawherephosphateoresarewidelydistributed.Asanewphosphorousstratumofphosphorite,itis characterizeddominantlybytypicalstromatoliticstructures.ThephosphoriteofstromatoliteislocatedatthetopoftheEdiacaran DengyingFormationthatiscomposedoflenticularorganicreef(algalreefofstromatolite).Themajormineralcomponentsofthe stromatoliticphosphoritearephosphatesandcarbonates.Thewhitelaminatedbedsareenrichedinphosphatemineralswhilethedark laminatedbedshavelowercontentsofphosphatemineralsandcontainmainlycarbonateminerals.Analysisofthemineralogicaland geochemicalcharacteristicsindicatesthatstromatoliticphosphoriteintheEdiacaranDengyingFormationisalgalreefofstromatolite thatwasformedinasemi-restrictedsubtidalenvironment.Accordingly,itcouldbeinferredthatthephosphoriccolumnarstromatolitic reefswereformedbyenrichmentinandprecipitationofphosphorusfromtheseawaterwithrichphosphorusduetocomplexbiological orbio-chemicalactionsofalgae.Inaddition,theresultsshowthatthemineralizationofphosphaticmineralsoccurredmainlyatthe sediment-waterinterfaceinweaklyalkalineandsuboxicenvironmentwherealgaehadplayedasignificantrole.