摘要
通过对广西南丹大厂用多金属矿床91号和100号矿体中透长石和石英的常规快中子活化和激光原位^(40)Ar/^(39)Ar法同位素年代学的研究,获得91号矿体块状锡石硫化物矿石中石英的^(40)Ar/^(39)Ar坪年龄为94.52±0.33 Ma,等时线年龄为 95.37±0.45 Ma,反等时线年龄为 94.89±0.16 Ma,透长石的激光^(40)Ar/^(39)Ar等时线年龄为91.4±2.9 Ma;100号矿体石英的坪年龄为 94.56±0.45 Ma,等时线年龄为 93.5±1.2 Ma,反等时线年龄为 93.29±0.16 Ma。这些资料有助于表明大厂锡矿形成于燕山期,在成因上证实后生成因的看法,并且表明产出特征不同的91号矿体与100号矿体是基本同时形成的。结合100号矿体规模巨大但围岩蚀变欠发育的特点,提出了含矿流体进入古溶洞后,由于突然的减压降温而导致成矿物质超常聚集的“失压沸腾”成矿机制。
The Dachang giant tin-polymetal deposit in Nandan, Guangxi, is one of the largest tin deposit all over the world. However, this deposit has long been in debate as to its origin. There are different opinions, one is that the Dachang deposit was formed by replacement of hydrothermal solution originated from Yanshanian granites, the other is that this deposit was formed by submarine exhalation at Devonian. This paper presents some new isotopic geochronology data by 40Ar/39Ar method on quartz and sanidine from massive ores in the No. 91 orebody and the No. 100 orobody. Analytic results show that the No. 91 orebody was formed at 94. 52±0. 33 Ma (plateau age by 40Ar/39Ar method of quartz) or 91. 4±2. 9 Ma (plateau age by 40Ar/39Ar method of feldspar), while the No. 100 orebody was formed at 94. 56±0. 45 Ma (plateau age by 40Ar/39Ar method of quartz), suggesting that both of the No. 91 and the No. 100 orebodies were formed at Late Yanshanian instead of at Devonian. The No. 100 orebody might be formed by filling of ore-materials at a pole-cave located in the reef-limestone. Because the ore-bearing solution lost its high press and lower its temperature suddenly at the cave environment, ores formed concentrately, with solutions disappear quickly and less alteration in the hostrocks.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2004年第1期132-138,共7页
Acta Geologica Sinica
基金
国家重点基础发展规划973项目(编号TG1999043203
TG1999043201)
地质大调查"中国大陆成矿体系"项目(编号K1.3)
关键词
锡多金属矿床
成矿时代
同位素年代学
等时线
giant tin-polymetallic deposit
Dachang, Guangxi
40Ar/39Arage
geochronology
pressure-lost and evaporation
