Monazite U-Th-Pb Ages of the Qinnan Gold Deposit, Xiaoqinling District: Implications for Regional Metallogenesis and Tectonic Setting
详细信息
- 责任者：Qiang Shanfeng (Land and Resource Bureau ; Lingbao 472500 ; China) ; Bi Shijian
- 刊名：Earth Science
- 出版年：2013
- 卷期：38(1)
- 页码：p.43-56
- issnNo：ISSN1000-2383
- isbnNo：CN42-1233/P
摘要
Two contrasting models have been proposed to explain the large-scale gold mineralization in the Xiaoqinling gold district,which is the second largest gold producer in China.The first model advocates that gold deposits in the Xiaoqinling district formed in the Triassic in relation to continental collision of the Qinling Orogen,whereas the second indicates that gold mineralization occurred in the Early Cretaceous and was genetically related to lithospheric thinning of the North China Craton.In this paper,we present high precision monazite U-Th-Pb ages of the Qinnan gold deposit in the north metallogenic belt of the Xiaoqinling district,by laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS).Petrographic observations show the monazite occurs as euhedral grains and invariably intergrown with quartz and pyrite,suggesting that monazites are of hydrothermal origin and precipitate with gold-bearing minerals coevally.In the 206Pb/238U-207Pb/235U and 206Pb/238U-208Pb/232Th diagrams,all of the 13analyses are concordant or nearly concordant,with weighted mean 206Pb/238U and 208Pb/232Th ages of 120.9±0.9Ma(MSWD=1.0)and 122.6±1.9Ma(MSWD=2.6),respectively.These ages are reproducible with existing geochronological data for major gold deposits in the Xiaoqinling district,demonstrating that the U-Th-Pb isotopes of the monazite have remained closed since its precipitation,and thus the U-Th-Pb ages can be reliably interpreted as the mineralizing age of the Qinnan gold deposit.A synthesis of available age constraints suggests that gold mineralization throughout the Xiaoqinling district occurred with a relatively short time interval in the Early Cretaceous and was likely related to the lithospheric thinning of the North China Craton at that time.