Characteristics Of Fluid Inclusions In Heiniudong Section Of Liwu Copper Mine,Jiulong County,Sichuan Province

The Heiniudong section of the Liwu copper mine is located in Yandai Township,Jiulong County,Sichuan Province.The tectonic attributes are a series of metamorphic core complexes on the west side of the Yangtze block,the southeastern margin of the Songpan-Ganzi orogenic belt,the Muli-Jinpingshan arc-shaped nappe tectonic belt and the northwestern trailing edge.The Heiniudong mine section is located in the Jianglang metamorphic core complex.The main exposed strata of the metamorphic core complex are the mesoproterozoic Liwu group?Pt₂l?stacking layer system,and the main exposed rocks are metamorphic basal volcanic rocks and subvolcanic rocks.Jianglang dome structure is a very important structure in the area.Due to the influence of tectonic activities in the area,a series of annular folds and faults are formed around the Jianglang dome structure.These folds and faults provide favorable conditions for the formation of later deposits.In the past few decades,people's research on this area has been deepened,and a series of geological exploration work has been carried out.The regional geological features,mineralization characteristics and ore-bearing properties,wall rock alterations,and rock geochemistry have been deepened.The research has achieved a lot of results.Even so,there are still some controversies in the genetic type of the deposit,the source of ore-forming fluids,and the mechanism of metallogenic migration.This paper mainly starts from the fluid inclusions in the Heiniudong mine section.The microscopic petrographic characteristics of the rock were analyzed by field sampling and combined with previous studies on macroscopic geological features and geochemistry of the deposit.The article mainly measures the homogenization temperature and freezing point of inclusions in the ore bodies such as I₁,I₂,I₃,II₄,and?₃ in the Heiniudong section.Based on the measured data,such as salinity,density,pressure and depth of the inclusions were calculated,and the source of the deposit fluid and the migration mechanism were analyzed,and the ore-forming model was established.The knowledge and achievements of the thesis are as follows:The fluid inclusion types of the Heiniudong section of the Liwu copper mine are mainly pure gas phase fluid inclusions,pure liquid phase fluid inclusions,gas-liquid two-phase fluid inclusions,inclusions of liquid crystal water and liquid inclusions,and liquid CO₂ containing three phases.Inclusions,etc.,in which pure liquid phase fluid inclusions are the most widely distributed,followed by gas-liquid two-phase inclusions.The inclusions are mainly elliptical,lenticular,long and irregular,distributed in groups or isolated,with a diameter between 10 and 50?m.In this paper,the homogenization temperature and freezing point of gas-liquid two-phase inclusions were measured,and the homogenization temperature range was 110.7³59.6°C.The temperature was mainly concentrated at 151.7³59.6°C,and the average value was225.01°C.There were two concentration intervals of 151.7?²27.9°C and231.2³59.6°C.The freezing point range is-0.7^-20.8°C.The calculated salinity range is 1.22²2.91wt%,most of which is concentrated between 6.01²0.67wt%,and the average salinity is 12.48wt%.According to the salinity formula,the density of ore-forming fluids ranges from 0.7606 to 1.007g/cm³.According to the calculation mode,the density range is 0.6659¹.0703g/cm³,and the density variation range is larger.The ore-forming pressure is 307.34×10⁵⁹87.04×10⁵Pa.The ore-forming depth is 1.02³.29km,and the average depth is 1.92km.It is a shallow mineral deposit.Due to the large variation range of salinity and density of the ore-forming fluids,combined with previous studies on hydrogen,oxygen isotope,S,Si,Pb and other elements in the study area,it is believed that the water in the ore-forming fluid has multiple sources,including atmospheric precipitation,magma water,metamorphic water and sea water.A series of basic rock types formed by the marine volcanic eruption in the western margin of the Yangtze plate in the middle proterozoic,providing primitive ore-forming materials for the formation of deposits in the area,and a series of strong tectonic movements and magma activity during the Indosinian-Yanshanian period,which provides a heat source and a tolerance space for the formation and enrichment of the deposit.Therefore,combined with the genetic information of fluid inclusions in the paper,it is believed that the genetic type of the Heiniudong section of the Liwu copper mine is a metamorphic deposit related to marine volcanic eruptions and regional tectonic activities.