Geological-geophysical-geochemical Characteristics And Prospecting Direction Of One Gold Deposit,in Hainan,China

Through the synthetic studies both in field and laboratory,combining petrology,mineralogy,element geochemistry,stable isotope and fluid inclusion,I have a deeper understand of the source of minerogenic substances and the characteristics of metallogenic fluids.Then I summarize the geological characteristics and mineralization regularity,determine the ore prospecting direction of Ding'an gold deposit.1.The strata emerging in this area are mainly clastic rocks of Lumuwan formation in the early Cretaceous: the main rocks consist of(gravel)feldspathic quartzarenite greywacke,pelitic siltstone,mudstone and so on.Because of the large porosity and calcareous layer,the loose sedimentary strata are easy to loosen and form interlayer fractures.The ore-forming hydrothermal fluid migrates and precipitates along these fissures,making the occurrence of ore bodies nearly the same as the stratum.So this gold deposit can be attributed to interlayer gliding fracture zone controlling structure type.Therefore,the long axis direction of geochemical anomalies and geophysical anomalies is also consistent with the trend of the stratum.2.The quartz diorite intruded into the Lumuwan formation in the early Cretaceous in this area,with gold veins in its margin and interior.The range of concealed rocks are delineated by magnetic anomalies,which are coincident with the geochemical anomalies of ore-forming elements,and the sulfur isotope data show that the ore-forming materials of gold mainly come from deep magma.Therefore,the quartz diorite is closely related to gold mineralization in time,space and origin.It not only provides the source of ore-forming materials,but also provides the source of heat and power for mineralization.3.Petrography,homogenization temperature,freezing temperature,salinity and density of the fluid inclusions in the gold quartz vein have been studied in detail,finding that the inclusions are isolated primary liquid-rich inclusions,small amount of CO2-three-phase inclusions and vapour-rich inclusions.The ore-forming fluid has the characteristics of medium-low temperature(homogenization temperature between 113.9 to 323.9°),low salinity(average 2.97 wt%NaCl)and medium density(average 0.90 g/cm3).Thus,the metallogenic pressure of the gold deposit is 80.16 ~ 235.45 × 105 Pa,and the metallogenic depth is 0.27 ~ 0.78 km.Therefore,this gold deposit is an epithermal deposit.4.Two prospecting targets are delineated by combining with the existing geological,geophysical and geochemical data in this area.