沂水南小尧金矿锆石U—Pb同位素特征及其地质意义

沂水南小尧金矿产于沂沐断裂带汞丹山凸起上，赋矿围岩为古元古代花岗岩。通过对南小尧金矿矿石中的锆石采用LA—CPMS法进行单颗粒锆石微区U—Pb同位素年龄测定，获得锆石谐和年龄（2438±13）Ma的结果，为赋矿围岩的形成年龄；而下交点（116±20）Ma大致为金矿的形成年龄。结合南小尧金矿石中钾长石矿物K—Ar年龄为（94．29±1．38）Ma的结果分析。本区金矿的形成时代应在早白垩世中-晚期。

U- Pb Isotopic Geo- chronological Characteristics and Implications of Zircon in Nanxiaoyao Gold Deposit in Yishui

Nanxiaoyao gold deposit in Yishui county locates in Gongdanshan uplift in Yishu fault belt. Its ore - bearing country rocks are Paleoproterozoic granite. There has always been many controversy to their forming age. In this study, by using LA- CPMS method and single grain zircon U- Pb micro- dating, it is gained that the concordant age of zircon is 2438 ± 13Ma and the age of the lower intersection point is 116 ± 20Ma. From analysis on regional ore - forming condition, it is regarded that the age of upper intersection point is the forming age of its country rocks. Combining with K - Ar age of 94.29 ± 1.38Ma of potassic feldspar in Nanxiaoyao gold deposit, it is regarded that the lower intersection point age can represent the gold - forming age. The forming time of the gold deposits in this area should be in early and late period of Cretaceous era.