| The Xiekeng Pb-Zn polymetallic ore deposit is located in Youxi County of Fujian Province,Southeast China.After several years of exploration work,the deposit retain Pb metal volume of 41 thousand tons,the average grade is 0.77%;zinc metal content of 358 thousand tons,the average grade of 6.63%;molybdenum metal 9 tons,average grade 0.091%.Comprehensive analysis in aspects of geological characteristics as well as its beneath granite of the Xiekeng mining area are conducted detailed during field and indoor investigations.Meteorological age of the deep granite is further determined by means of the high-precision LA-ICP-MS zircon U-Pb chronology.Relationship between the rock and the mineralization is also probed lithologically and geochemically.Microfacies identifications of polished and thin sections are available in recognitions of the metallogenic epoch,source and mineralization process.These studies are implications for mineralization pattern and prospecting of economic geology.Key promotions are highlighted as following:1)Lead-zinc ore body within the greenschist of Longbeixi Group are occurred as three types respectively of the a:in the greenschist;b:near the contact zone between greenschist and marble;and c:fracture zone and weak layers.2)Molybdenum orebodies mainly occur in the inner and outer contact zones between the granite and Longbeixi Formation.Contact zones rich in quartz veins,joints,plates and fissures nearby the surrounding rocks are of the key structures with special references of ore-bearing spaces.3)The field investigation and mineralographic study indicated that the lead-zinc mineralization in the Xiekeng Pb-Zn polymetallic deposit is controlled by the stratigraphic horizon,and the main ore bodies are mainlybedded and bed-like form,only a few of them are lenticular.The ore bodies which are in conformity with the country rocks in attitude have relatively stable thickness and large extension.The molybdenum mineralization was obviously affected by the hydrothermal activity of the magmatic structure,forming irregular ore-body shapes.The Lead-Zinc ore bodies are mainly distributed in blocked,belt and layer-like form,controlling by the dip of the bed.The molybdenum ore bodies are mainly membranous,vein-fine vein and mesh-vein forms,which was obviously effected by magmatic hydrothermal fluids and structures.Most of the Lead-zinc ores which were affected by variety degrees of metamorphic deformation are characterized by,corrugated structure,oriented deformation structure,recrystallization structure and pressure-dissolving structure,indicating that the lead-zinc ore(main body)was formed before the regional metamorphism(Caledonian).In addition,typical skarn and hydrothermal precipitation mineral combination formed from high temperature to low temperature are common near the contact zone of the Yanshan granite intrusion body.Therefore,the Xiekeng Pb-Zn polymetallic deposit development can be divided into three periods based onthe ore structures,the mineralization and mineral symbiotic relationship:?Mesoproterozoic-Neoproterozoic Volcanic exhalative sedimentation period:During the Mesoproterozoic-Neoproterozoic era,with a background of the rift basin,the source layer was formed by submarine volcanic-sedimentary action,and developed with exhalation,sedimentation and accumulation of mineral-bearing hydrothermal fluids and eventually became the massive sulfide deposits.? Caledonian metamorphic transformation period:Effected by the Caledonian structure and metamorphism,the strata and ore bodies formed during Mesozoic-Neoproterozoic ear were metamorphic and deformed during the period.The ore-forming material was activated,transferred and precipitated,resulting in mineral aggregation,superposition,recrystallization or enrichment and then the new lead-zinc ore body was formed.?Yanshanian magmatic hydrothermal superimposed mineralization period:The granitic magma intrusion and associated magmatic hydrothermal activities in Yanshanian,activated and transferred and superposed lead-zinc ore bodies.The Pb,Zn,Mo and Fe in hydrothermal fluids and reactivated of Pb,Zn migrated upwards from the deep.They were concentrated in the lithology(e.g.,greenschlite,greenschs and marble contact zones)and tectonic favorable places(e.g.,faults and rock foliation),and formed the ore body.Due to the different mineralization temperatures,the ore body became zonal,and the molybdenum ore body(and the magnetite mineralized belt)was formed at contact zone of the rocks and the lower strata of the Longbeixi Group near the zone.The lead-zinc ore body was formed in strata of Longbeixi Group where was a certain distance from the rock.4)The lead-zinc deposit in this area is a massive sulfide deposit formed by submarine volcanic eruption exhalative sedimentation,deformed and modified,and altered by magmatic hydrothermal superposition.The molybdenum deposit is of the magma hydrothermal type. |
PDF Full Text Request