Dating of copper mineralization in Jingbian deposit and its prospecting significance in Luzong basin, Anhui Province.
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摘要: 庐枞盆地是长江中下游多金属成矿带中一个重要的多金属矿集区,盆地内发育有多个不同规模的脉状铜矿床。目前对这些脉状铜矿床的成矿时代和构造背景等方面的研究工作还较少。本文以盆地中目前最具代表性的井边铜矿床为研究对象,分别对矿床中的安山斑岩次火山岩体和主成矿阶段石英中流体包裹体采用了LA-ICP-MS锆石U-Pb同位素定年和Ar-Ar同位素定年,获得了安山斑岩LA-ICP-MS锆石U-Pb年龄为133.2±1.7Ma,石英流体包裹体Ar-Ar等时线年龄为133.3±8.3Ma,反等时线年龄为133.3±8.2Ma。这一结果与实际的矿床地质特征和区内岩浆岩已有的同位素年代学数据完全吻合,因而井边铜矿床的形成时代为早白垩世,与盆地中砖桥旋回侵入岩浆活动有关。这一矿化事件与长江中下游地区第二期(135~127 Ma)大规模成岩成矿作用相对应,并对应于区域拉张的构造背景。通过本次研究工作,不仅为深入理解庐枞盆地内铜矿化的规律提供了资料,同时也为该区的下一步铜矿找矿工作提供了依据。Abstract: Luzong basin is one of the most important metallogenic district in the mineralization belt of the Middle and Lower Reaches of the Yangtze River area, where occurs many vein-type copper deposits with various scales. Nevertheless, little research work has been done on the timing and tectonic setting of these deposits. In this paper we present the LA-ICP-MS zircon U-Pb dating results of andesite porphyry and fluid inclusions Ar-Ar dating results of quartz from Jingbian vein-type copper deposit. LA-ICP-MS zircon U-Pb dating yield the age of 133.2±1.7Ma, and fluid inclusions in quartz yield an isochronal age of 133.3±8.3Ma and an inverse isochronal age of 133.3±8.2Ma respectively. These results coincident with the geological characteristics of deposits and the available highly precise dating of related magmatic rocks. So the Jingbian vein-type copper deposit took place in Early Cretaceous and related to the intrusive activity of Zhuanqiao Formation. This mineralization event in Luzong basin were consistent with the second period (135~127Ma) magmatic and metallogenic activity in the Middle and Lower Reaches of the Yangtze River area, and corresponding to an extension tectonic environment. This contribution is not only providing evidence for a comprehensive understanding the magnetism and mineralization of the Luzong basin, but also shows the prospecting potential to find cooper deposit in this area.
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