Geological Characteristics And Prospecting Indicators Of Lalang Gold Deposit In Mengkhan County, Xieng Khouang Province, Laos

The Laos-Vietnam Chuangguang-Changshan copper gold metallogenic belt,with unique geological conditions and rich mineral resources(rich in iron,copper and gold),produces a series of large and medium-sized copper gold deposits such as Sepon and seikai.It has an important position in Southeast Asia.It is a metallog enic belt between the Ailao Mountain and the sulebo and the suture zone of the Ma Jiang suture zone.The Lalang gold deposit,which is located in it,is a large gold deposit discovered in Laos in recent years.On the basis of the detailed field geological survey,the ore controlling factors are analyzed through the alteration of surrounding rock,the existing state of gold,the ore geochemistry and the ore objects,and the genesis of the deposit is discussed.Finally,the geological and geochemical characte ristics are integrated,and the prospecting marks are summarized.The formation and distribution of regional gold deposits are obviously controlled by structures.The fault controls the formation and distribution of ore bearing formation,and the anticline or dome structure controls the distribution of ore field.The secondary fault structure controls the output of the orebody,and the copper gold metallogenic condition is superior.Lalang gold deposit in Laang Lang Kuang gold deposit,located in the Changshan metallogenic belt,is a large gold deposit discovered in Laos in recent years.Because of the large scale of the deposit,it is produced in the granite intrusive body and the sandstone and limestone rock stratum contact alteration zone,and is obviously subject to the control of the ductile shear zone or the thrusting fault.Two long granite porphyry mainly occurs in the mining area,and magmatic activity provides a rich material basis for mineralization and a leading factor in mineralization.The mineralization occurs in the granite intrusive body in contact with the sandstone and limestone rock strata,and is obviously controlled by the ductile shear zone or the thrust fault.The gold deposits are strictly controlled by the fracture zone and the contact zone,and the low temperature hydrothermal alteration is very well developed,mainly silicification,arsenide(ARSENOPYRITE,realgar,Ci Huang),pyrite and antimony.Mineralization,calcization and so on.Gold mineralization is closely related to silicification,pyrite mineralization and arsenopyrite.There are five main mineral assemblages in the mining area:(1)Quartz-pyrite assemblage,(2)quartz-arsenopyrite-pyrite assemblage,(3)pyrite-arsenopyrite combination,(4)quartzite-limonite assemblage,and(5)limonite-antimony assemblage.The large particles of natural gold are symbiotic with quartz veins.The gold bearing materials are mainly carbonate wrapped gold,copper lead zinc sulfide ore wrapped gold,limonite wrapped gold,and pyrite wrapped gold.Carbonation,pyrite mineralization,silicification,copper lead zinc sulfide mineralization are directly related to mineralization and can serve as prospecting indicators.The results of ore spectrum show that Ag,As,Bi,Cd,Mo,Pb,Sb,Zn,In and Ta are obviously enriched,and no obvious combination of high temperature alteration elements such as potash is found.It may be pointed out that the Lalang gold deposit is more likely to be a low-temperature hydrothermal deposit rather than a high temperature porphyry mineralization.The tectonic movement force or expansion belt generated by fault activities is one of the important reasons for the migration of ore-forming hydrothermal fluids.The influence and control of the brittle ductil e shear zone on mineralization are: increasing the diffusion coefficient and permeation flow,providing heat energy,changing the existing state of gold,providing the dynamic metamorphic hydrothermal fluid and the reaction environment of the fluid and roc k.The formation of gold deposits is controlled by the brittle ductile shear zone,which controls the transformation of multiple source fluids.On the basis of the above analysis,the prospecting indicators such as stratigraphy,lithology,sedimentary faci es,tectonics,alteration,geochemistry and outcrop are summarized.