山东单县地区BIF型铁矿成矿时代——SHRIMP U-Pb锆石定年

Formation Age of BIF Iron Ore Deposit of Shanxian Area in Shandong Province——Constraints from SHRIMP Zircon U-Pb Dating

单县铁矿是近年来在鲁西南地区查明的典型铁矿床之一;该铁矿位于巨厚覆盖层下,其地质特征、地球物理特征、矿床特征和矿体特征等方面均已查明,但成矿时代一直没有精确的定年数据支持。该次研究工作对单县含铁建造中的黑云变粒岩进行锆石SHRIMP U-Pb测年,测年结果显示该含铁建造形成于(2 503±6)Ma、(2 512±6)Ma,属新太古代晚期。通过与鲁西地区相关铁矿地质特征对比研究认为,单县铁矿与苍峄铁矿带、东平-汶上铁矿带的含矿建造相同,其赋矿地层为新太古代泰山岩群山草峪组,均属"苍峄式"沉积变质型铁矿。由于该山草峪组含矿建造在鲁西隆起区内广泛分布,通过对区内地质特征和物探异常的对比进行选区研究,利用单县地区铁矿的勘查经验并选取有效的勘查技术手段,有望在周邻地区的巨厚覆盖层下发现新的铁矿找矿靶区。

Shanxian iron ore deposit is one of the representative iron ore deposits that have been found in the southwest region of Shandong in recent years. The iron ore deposit, buried in very thick covering strata, has been identified of geological characteristics, geophysical characteristics, ore deposits and orebodies characteristics. But its mineralogenetic epoch has not been supported by accurate data. SHRIMP U--Pb dating on zircon of biotite leptynite has been carried out in Shanxian deposit. It is showed that the BIF are 2503±6Ma, 2512±6Ma, which belongs to the era of late Neoarchean. Based on the comparison with the geological characteristics of related iron ore deposits in Luxi area, it is suggested that the Shanxian iron ore has the same iron ore formation with Cangyi iron ore belt and Dongping--Wenshang iron ore belt. The ore --bearing formation is the Shancaoyu Formation of Taishan Group in Neoarchean, and all of these iron ore deposits belong to ＂Cangyi type＂ sedimentary metamorphic iron ore deposit. Because the ore--bearing formation of the Shancaoyu Formation is widely distributed in Western Shandong uplift area, it is expected to find new iron ore prospecting targets in the adjacent thick overburden areas by research on geological features and geophysical anomaly, using exploration experience and selecting effective exploration means.