Geological Characteristics Of The Shayikenbulake Pegmatite Beryllium Ore Deposit In Altai,Xinjiang

Altai,one of the most important rare metal provinces,contains several large or medium rare metal deposits.Shayikenbulake Deposit is one newly discovered beryllium deposit in Altai province.Orebodies occur at biotite-quartz schist as the steep veins in Upper Habahe Subgroup,Middle-Lower Ordovician.Albitization and Chloritization can be distinguished clearly.Based on the study of lithology,mineralogy and geochemistry of the Shayikenbulake beryllium deposit,some conclusions can be drawn:(1)The orebodies occur in biotite-quartz schist,Upper Habahe Subgroup,Middle-Lower Ordovician.Beryl is the main ore mineral.Therefore,feldspar,mica,quartz,as well as less-common garnet,tourmaline are the gangue minerals.(2)The I pegmatite vein of the deposit shows three distinct mineral belts,(a)margin zone(a transitional mineral zone between wall rock and pegmatite),(b)outer zone(white granulated sugar and brown garnet with beryl fine-grained muscovite quartz albite subzones,gray medium-grained graphic texture of the subzones,gray medium-fine-grained muscovite quartz albite containing beryl graphic texture subzones)and(c)quartz core.(3)The geochemical differences in feldspar and mica in pegmatite and wall rock indicate an inherited relationship of their chemical compositions.It may be speculated that the pegmatite is the product derived from the migmatization of the lower Habahe Subgroup.(4)The fluid inclusions suggest a medium-high temperature and medium-low salinity ore-forming environment,with wide ranges in homogenization temperature(180°-400°C)and salinity(3.5?22.4%NaCl eq.,mainly 4-12%).The lower fluid density(quartz 0.51?1.03 g/cm3,beryl 0.74?1.05 g/cm3)indicates a mixture of meteoric water in the ore-forming fluid.(5)By fluid inclusion study,ore-forming fluid pressure ranges from 205.2?762.1 MPa(average 452.8 MPa),and indicates a depth of 0.76?2.83 km(average 1.68 km).(6)The pegmatite belongs to metamorphic-hydrothermal type.