右江盆地卡林型金矿成矿年代学研究进展

Research advances on the geochronology of Carlin-type gold deposits in the Youjiang Basin,southwestern China

右江盆地是全球仅次于美国内华达地区的第二大卡林型金矿床集中分布区。由于成矿时代的不确定性,盆地内卡林型金矿床的成矿动力学背景一直不清。为准确确定这些金矿床的成矿时代,近四十年来国内外矿床学家进行了孜孜不倦的探索,从早期以石英裂变径迹和流体包裹体Rb-Sr等时线法为代表的定年,到中期以硫化物Re-Os等时线法为代表的单矿物溶样法定年,再到最新以热液金红石、独居石和磷灰石U-Th-Pb法为代表的微区原位定年,其定年对象和方法见证了同位素地质年代学的发展历程。现已基本明确,右江盆地主要发育两期卡林型金矿成矿作用,分别为215~200 Ma和155~140 Ma,相当于印支期和燕山期,其动力学背景分别对应于印支-华南-华北地块碰撞后的印支期陆内造山过程以及燕山期软流圈上涌诱发的岩石圈伸展作用。

The Youjiang Basin hosts the world’s second largest Carlin-type gold province after Nevada,USA.However,due partly to the uncertainty of their mineralization age the geodynamic setting of the Carlin-type gold deposits remains unclear.During the past forty years significant efforts have been made to accurately constrain the timing of these gold deposits,ranging from the early dating methods(with low reliability)such as quartz fission track and fluid inclusion Rb-Sr isochron dating,to the midterm dissolution-based bulk analyses of mineral separates such as sulfide Re-Os,to the latest in-situ precise U-Pb dating of hydrothermal U-bearing minerals including rutile,monazite,and apatite.It has now been clearly considered that there existed two episodes of Carlin-type gold mineralization in the Youjiang Basin ca.215200 Ma and 155140 Ma,probably in response,respectively,to the Indosinian post-collisional intracontinental orogeny and the Yanshanian asthenospheric upwelling and lithospheric extension in southern China.