Geochronology and thermochronometry of the Jiapigou gold belt, northeastern China: New evidence for multiple episodes of mineralization

摘要

The Jiapigou gold belt, one of the most important gold-producing districts in China, is located in the northern margin of the North China Craton. In this belt, auriferous quartz vein types of gold deposits dominantly exist besides a few disseminated types of ore deposits. Though some research papers have been published about this belt, the mineralization ages of the gold deposits within this region are still controversial. This work uses zircon U-Pb, fission-track and ~(40)Ar/~(39)Ar dating methods to probe the timings and numbers of episodes of gold mineralization in the Jiapigou gold belt. The zircon U-Pb ages can be divided into four groups: 166-170 Ma, 208 Ma, 228.9-230.0 Ma and 2342-2536 Ma. The fission-track ages on zircons from ores show three groups of ages: 86-106 Ma, 120-138 Ma and 153-155 Ma. The ~(40)Ar/~(39)Ar ages on biotite and K-feldspar coincide with the ages mentioned above. A total of five age groups have first been revealed: 230.0-228.9 Ma, ～208 Ma, 170-153 Ma, 138-120 Ma and 106-88 Ma. Because the samples come from mineralized and altered rocks, or because the zircons belong to hydro-thermal type, the five age groups could indicate five episodes of gold mineralization with the three middle age groups being most plausible. It is the multiple episodes of mineralization that resulted in the occurrence of large-scale gold deposits in the Jiapigou belt. Remarkably, the ages of tectonic-magmatic events coincide well with the dated mineralization periods. Therefore, each episode of mineralization was closely related to regional plate activities in different epochs.