Fission Track Thermochronology Of The Xincheng Gold Deposit, Northwest Of Jiaodong Peninsula

Jiaodong area is mainly composed of Precambrian metamorphic basement rocks and ultrahigh pressure metamorphic rocks with the intrusion of large scale Mesozoic granites, and it is important endogenous hydrothermal gold concentration area of our country, formed the Jiaojia, Xincheng and Sanshandao and others large or super large gold deposit, its total gold reserves accounted for about a quarter of the whole nation, and the output environment and mineralization dynamics background of gold deposit in Jiaodong is unique in the global. Predecessors have done a lot of research work in the " origin", " migration" and "store" of the Xincheng gold which is biggest gold deposit occurrence in the early Cretaceous granite, this paper base on the of the predecessors’ research results and field work, through the apatite and zircon fission track thermochronology on "change" and" preservation" of the Xincheng gold deposit, and obtained some mainly acknowledges as following:In this study, Ore samples, rock samples with no mineralized alteration, and the distal fresh granite samples have consistent heat history within zircon fission track close temperature range. The main ore-forming period of the Xincheng gold deposit is a little later than 120.7Ma, the intrusion of Guojialing type granite in ore district might provid about 15Ma thermal environment which is over 190 ℃, that might contributed to the extension of duration of gold mineralization, and lead a huge amount of gold enriched in the Xincheng gold deposit to become a super large gold deposit occurs in the early Cretaceous Guojialing type granite.The length and distribution of apatite fission track indicate that the range of cooling rate of the Xincheng gold deposit is monotonous and slower cooling through the sealing temperature range of apatite fission track during the apatite fission track age 10.5±2.0Ma～43.3±3.6Ma.According to comprehensive constraint of thermal history simulation of apatite fission track, zircon fission track age and ore-forming age of gold deposit, the thermal evolution history of gold deposit can be divided into four stages:rapid coolingâ†' the faster coolingâ†'slow coolingâ†'faster cooling.The total exhumation of the gold deposit is about 6±1 km since ca.120 Ma, in consideration of the metallogenic depth of the gold deposit is 6.51-8.28 km, consider that the gold ore body almost is not denudated, there is a great potential for prospecting in deep. In addition, speculate that there may be others large or super large gold deposits occurrence in the early Cretaceous Guojialing granite which similar to the Xincheng hidden under the ground in northwest Jiaodong. Thus, it should do more work in place where similar to the Xincheng gold deposit in geology environment in the later mineral exploration and prospectingin.