AN INVESTIGATION ON ISOTOPE COMPOSITIONS IN THE GOLD DEPOSITS OF BAOTOU-BAIYUNEBE DISTRICTS, INNER MONGOLIA
Xu Yanjun Lin Erwei(JilinPetroleum Exploration Headauarters) (Test Centre)
An isotopic study was carried out on three gold deposits located in the northern edge of North China Plate, which cut through high, middle and low-grade metamorphic rock areas. All the deposits have an anomalous lead composition,and define a line with different slope on a plot of 207Pb/204Pb vs. 206Pb/204Pb diagram,and the rock or k-feldspar leads plot near or on these lines.The ores lead composition can be interpreted by a mixing model. A K-Ar age of 281.5 Ma and a median Rb-Sr age of 295.6 Ma was given by the hydrothermal minerals from Shibaqinhao deposits, and the age of granite occurred in other two deposits give a similar age.If we suppose the mineralization happened during Late Paleozoic, the ore Pb-Pb mixing line suggests an age similar to zircon U-Pb age of the metamorphic parentage rocks in different deposits.The isotope compositions indicate that the metallic components in hydrothermal fluids were derived from both metamorphic and granitic rocks. Acc ording to lead mixing model, the authors calculated the Pb mixing proportion in gold deposits in metamorphic rock and granite.
【CateGory Index】： P597.2