Study On Paragenetic Association Of Minerals In Malipo Emerald Deposit From Yunnan Province

The emerald deposit lies in the northern part of the Laojunshan-Song Chay metamorphic core complex in Malipo,Yunnan province.The geological environment here is so complex that emerald has multiple genesis.Research from the deposit's geologic characteristics,according to the systematic researches on the field survey,rock sheets observation,trace elements analysis and cathodoluminescence images,the author focused on studying mineral intergrowth association with emerald formed in different pegmatite veins and conjecturing ore-forming order of mineral.Emerald mineralization is hosted by northeast-southwest-trending pegmatite veins(80?330°?15°?30°)or northwest-southeast-trending crustal faults and shear zones(190?250°?20?30°).Pegmatite veins shows the mineral zonation: rock-biotite-quartz-potassium feldspar/ albite-emerald.The main rock types are granulite,granofels and mica schist.Common mineral assemblages: potassium feldspar+ muscovite + tourmaline+ emerald,quartz+ emerald+ muscovite,quartz+ potassium feldspar+ emerald+ biotite+ muscovite+ tourmaline,albite+ emerald+ biotite.Muscovite and tourmaline can be absent.Accessory mineral are arsenopyrite,pyrite,apatite,sphene,calcite,fluorite.In pegmatite veins,the content of Cr,V was low in emerald from albite veins,thus the color is light.Content of V are similar in emerald from potassium feldspar veins,felsic veins and quartz veins,emerald's crystallinity is better in felsic veins than that in potassium feldspar and quartz veins.Emerald shows better color and crystal form which has same content of V and higher content of Cr in shear zones.The quality of emerald and existence of muscovite and tourmaline have positive correlation.According to the content of Ba in potassium feldspar from rock and veins,we can conjecture ore-forming order of emerald veins;biotite with high content of V is magnesian and of mantle-crust mixing type in emerald veins.The paragenetic mineral with emerald are potassium feldspar(microcline),quartz and albite.Emerald has the characteristics of multi-stages.In pegmatite veins,the ore forming order of mineral maybe biotite,tourmaline,emerald and muscovite.Apatite and sphene formed at early stage of magmatic differentiation.According to the order of mineral crystallization and element evolution,we can conjecture ore forming order of emerald veins:potassium feldspar-quartz veins? potassium feldspar feldspar veins? albite-quartz veins? albite veins? quartz veins.