Dating of the Dachang Superlarge Tin-polymetallic Deposit in Guangxi and Its Implication for the Genesis of the No.100 Orebody

• Published in: 地质学报(英文版) Vol. 78; no. 2; pp. 452 - 458
• Main Authors: WANG Denghong, CHEN Yuchuan, CHEN Wen, SANG Haiqing, LI Huaqin, LU Yuanfa, CHEN Kaili, LIN Zhimao
• Format: Journal Article
• Language: English
• Published: Institute of Mineral Resources, Chinese Academy of Geological Sciences, Beijing 100037%Chinese Academy of Geological Sciences, Beijing 100037%Institute of Geology, Chinese Academy of Geological Sciences, Beijing 100037%Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100010%Yichang Institute of Geology and Mineral Resources, Yichang, Hubei 443003%Guangxi Bureau of Geology and Mineral Resources, Nanning, Guangxi 530023 2004
• Subjects: geochronology; pressure release and evaporation; Guangxi; superlarge Sn-polymetal deposit; Dachang
• ISSN: 1000-9515; 1755-6724
• DOI: 10.3321/j.issn:1000-9515.2004.02.017

P5; The Dachang superlarge Sn-polymetal deposit in Guangxi, China, is one of the largest tin deposit all over the world. However, this deposit has long been in debate as to its origin. One of the opinions is that the Dachang deposit was formed by replacement of hydrothermal solution originating from Yanshanian granites, and the other is that this deposit was formed by submarine exhalation in the Devonian. This paper presents some new isotopic geochronology data obtained with the 40Ar-39Ar method for quartz and sanidine from massive ore in the No. 91 and No. 100 orebodies. Analytic results show that the No. 91 orebody was formed at 94.52±0.33 Ma (the plateau age obtained with the 40Ar-39Ar methodfor quartz) or 91.4±2.9 Ma (the plateau age obtained with the 40Ar-39Ar method for feldspar), while the No. 100 orebody was formed at 94.56±0.45 Ma (the plateau age obtained with the 40Ar-39Ar method for quartz), suggesting that both the No. 91and the No. 100 orebodies were formed at the Late Yanshanian instead of the Devonian. The No. 100 orebody might be formed by filling of ore materials into caves in Devonian reef limestone. Because the ore-bearing solution released its pressure and lowered its temperature suddenly in a cave environment, ore minerals were formed concentratedly while water and other materials such as CO2 evaporated quickly, resulting less alteration of host rocks.