Study On The Characteristics Of Metallogenic Fluids Of The Huajian Gold Deposit In Eastern Hebei Province

The Huajian gold deposit is a near-surface,moderate-temperature,hydrothermal vein-type mine lot related to magmatism.It is located on the east side of the contact between Shanhaiguan uplift and Malanyu anticlinorium in the East of Yanshan platform Fold Belt in North China platform.It experienced intense tectono-magmatic activity in Mesozoic Era,including indosinian and Yanshanian orogeny.Based on the systematic study of the geological characteristics,fluid inclusions and stable isotopes of the deposit,the temporal and spatial evolution characteristics and metallogenic mechanism of the ore-forming fluid of the deposit are discussed,which provides a certain theoretical basis for deep prospecting in the area.The geological study of the deposit shows that the ore-forming process of the deposit can be divided into three stages according to the time sequence.The early mineralization was characterized by a large amount of quartz,K-feldspar and a small amount of pyrite.The middle stage of mineralization is characterized by quartz,pyrite,chalcopyrite,Galena and sphalerite.The late mineralization is characterized by the presence of a large number of quartz and calcite.The study of fluid inclusions indicates that the ore-forming fluid of the Huajian gold deposit is a medium-low salinity H2o-nal±CO2 fluid system.The early stage of mineralization is dominated by L-type and L-V type,while the middle stage is dominated by L-V-S type,L-V type and L-type.The late stage of mineralization is mainly L-shaped.The results of microthermometry show that the homogenization temperature of Huajian gold deposit is about 77-403?.The temperature of early mineralization stage is mainly 270-330?,with an average of 318?,and the average salinity is 7.2%Na Clequ.The temperature of main mineralization stage is mainly 230-290?,with an average of 258?,and the average salinity is 6.48%naclequ.The temperature of late mineralization stage is mainly 90-150?,with an average of 119?,and the average salinity is 4.73%naclequ.From the early stage of mineralization to the late stage of mineralization,the temperature and salinity of the ore-forming fluid in Huajian have a downward trend.The homogenization temperature of the deep ore-forming fluid in the main ore-forming stage is mainly 240-290?,with an average of 260?and an average salinity of4.46%Na Clequ;the homogenization temperature of the middle ore-forming fluid is mainly 180-230?,with an average of 207.9?and an average salinity of 3.96%naclequ;the homogenization temperature of the shallow ore-forming fluid is 141-277?,with an average of 183.7?and an average salinity of 3.58%naclequ.From deep to shallow,the temperature and salinity of fluid inclusions in the main ore-forming stage also decrease slightly,and the fluid activity in deep is stronger than that in shallow.The composition of the liquid phase at different depths is mainly H₂O,and a few samples have Raman characteristic peaks of SO₄^2-.The gas phase composition of the inclusions is also mainly H₂O.The hydrogen and oxygen isotopes of fluid inclusions at different depths in the main ore-forming stage are as follows:?^18ois-2.42?8.64‰,?D is-61.98?-102.02‰.It shows that the ore-forming fluid of Huajian is mainly derived from magmatic water and meteoric water.And in the H₂O isotope composition map,from the deep to the shallow,more and more close to the atmospheric rain,indicating that the influence of atmospheric water is increasing.The sulfur isotope results show that the?^34svalues vary slightly,ranging from 3.4 to 6.2‰,with an average of 5.1‰,indicating that it may be mainly from deep magma.?^34Stends to decrease from deep to shallow.Based on the study of deposit geology,fluid inclusion and stable isotope,it is speculated that the ore-forming fluid in the main mineralization stage of Huajian gold deposit may come from the magmatic activity of intermediate-acid Dykes,and that the fluid in the late mineralization stage is a low temperature and low salinity hydrothermal solution,which may be mainly from meteoric water.Therefore,in general,the Huajian gold deposit is the result of the superposition of magmatic activities and meteoric water in different stages of Yanshanian.Figure 18;Tables 10;References 76...