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。
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.