The Genesis Of The Two Phases Of Basic Rocks In The Zhesang Gold Deposit In Funing,Yunnan And Its Relationship With Gold Mineralization

Basic rocks are closely related to the genesis of gold deposits.Predecessors' studies on many gold deposits at home and abroad have confirmed that basic rocks are closely related to gold mineralization in terms of time,space location,and ore-forming sources.This paper mainly studies the petrology,zircon U-Pb chronology,and main and trace element geochemical characteristics of basic rocks in the early and late periods of Funing,Yunnan,and the high Ti basic rocks in the same area and Zhe Sangjin in the same area studied by previous studies.The ore rock and ore have done a comparative study to explore the characteristics and genetic mechanism of the source area of the two phases of basic rocks,compare the chemical properties of the two phases of basic rocks,analyze the impact of the two phases of basic rocks on gold mineralization,and establish the area The metallogenic model of Carlin-type gold deposits.This article has mainly obtained the following knowledge: Zircon U-Pb age analysis results show that the early basic rock age is 248±5 Ma;the late basic rock age is 213±5 Ma,which is 215.3±1.9 Ma highly consistent.The results of major element analysis show that the early basic rocks fall in the subalkaline gabbro area in the TAS map,and most of the late basic rocks fall in the alkaline-subalkaline gabbro area;The two phases of basic rocks show different trends in the Huck diagram,indicating that each has undergone a different separation and crystallization process.The distribution pattern of rare earth elements shows that the early basic rocks are enriched in LREE,with a right-leaning trend as a whole,and there is a positive Eu anomaly;in the late basic rocks,the separation of light and heavy rare earths is strong,and the fractionation of light rare earths is more obvious,and the whole is right-leaning.There is an obvious negative Eu anomaly,indicating that it is in a reducing environment.The trace element spider diagram shows that the high field strength elements Nb and Ta and the large ion lithophile elements Rb and Pb in the early basic rocks show slight negative anomalies,and Ba shows positive anomalies,which have the characteristics of oceanic island basalts;late basic rocks The rock has the characteristics of back-arc basin basalt,with obvious Nb and Ta depletion,indicating that the magma has been contaminated by the crust;the relatively low content of Ni and Cr,indicating that significant separation and crystallization occurred during the formation of dikes;The relatively high values of La/Nb and La/Ta indicate that the magma is formed by partial melting of the lithospheric mantle.It can be seen that the two phases of basic rocks were formed in different periods,experienced different degrees of separation crystallization and crustal contamination,and have different mantle sources.The age of the early basic rocks is much greater than the age of gold mineralization.The isotope analysis of fluid inclusions and gold-bearing minerals and the distribution pattern of rare earth elements all indicate that the early basic rocks have little relationship with gold mineralization,while the late basic rocks are in Time,space,and material sources all show a close relationship with gold mineralization.Therefore,this article believes that the early basic rocks have little effect on gold mineralization,and only provide a suitable redox environment for mineralization,while the late basic rocks provide ore-forming materials,which continuously assimilate and mix with the crustal materials during the ascent.It interacts with hydrothermal sulfide to extract gold and other elements,and also provide a certain thermal driving force to activate the migration of minerals,and finally deposit and form minerals in favorable structural positions.