Iron Isotopes,Sulfur Isotopes And Fluid Inclusions Of The Sandaowanzi Gold Telluride Deposit,Heilongjiang

The Sandaowanzi telluride gold deposit,located in the Great hinggan range metallogenic belt in NE China,is a large epithermal gold deposit of low-sulphidation type.More than 95 percent Au budgets are hosted in gold-silver tellurides,and the wall rock is trachyte andsite of Longjiang Group.It has a total reserve of?25t of Au and an average of 15g/t(the highest grade being up to 20000g/t).Gold-bearing quartz veins or gold lodes trend NW-SE and dip NE.Pyrite is the most common sulfide in the altered volcanic rocks and in the disseminated ores.Iron isotopes and sulfur isotopes have been widely applied to interpret the fluid evolution of the hydrothermal deposit,which may also have significant implications on the research of the Sandaowanzi telluride gold deposit.Fresh pyrite and quartz samples were collected from underground workings in different mining levels(+210m to+50m)of the deposit.Iron and sulfur isotopic characteristics of pyrite samples,combined with the results of fluid inclusions temperature tests of quartz samples,were used to explain the fluid history.The isotopic tests show that?⁵⁷Fe values from-0.27 to 0.98(av.0.33)and?³⁴S values from-0.85 to 0.53,and the range of the homogenization temperature is between 200?to290?.Furthermore,the ³⁴S values of the sulfur isotope of pyrite are near 0,showing the characteristics of mantle sulfur.The above data set shows that the?⁵⁷Fe values and the?³⁴S values are heterogeneous at different levels of the ore body.The?⁵⁷Fe values in level+130m and level+170m were smaller than other those of other levels,and the same to?³⁴S values.A general trend for the positive values is that the highest?⁵⁷Fe value is located at level+130m,but decreases gradually towards deeper and shallower levels.Meanwhile the scale of isotopic compositions in level+130m is large,and the data is spread in level+50m.The temperature is higher in level+170m,according to the temperature tests.According to the results of the tests,we find that the metallogenic process lasted for a long time.Two stages of the isotope fractionation are thus expected:during the early stage,isotopically light iron and sulfur were enriched at level+130m and level+170m,meanwhile the temperature of these levels are higher;during the later stage,isotopically heavy iron and sulfur were enriched at level+130m,meanwhile the temperature at level+130m was low.The result of?⁵⁷Fe and?³⁴S suggest that mineralization started early near the levels+130m and+170m,and ended at the level+130m.During the later stage of the mineralization,the level+130m had an enrichment of ore-forming materials,and the residue was the gold-bearing fluid simultaneously.Along with the evolution,the Au occurred in the ore block in the final stage.All the test data of level+50m show different regulation to those of other levels.Therefore,we suggest that the level+50m was influenced by another hydrothermal solution.