湘南荷花坪锡多金属矿床地质特征及辉钼矿Re-Os测年

Geological characteristics and Re_Os dating of molybdenites in Hehuaping tin-polymetallic deposit, southern Hunan Province

荷花坪锡多金属矿是近年来在湘南地区王仙岭岩体南东接触带新发现的一个具大型规模的矿床,主要由含锡矽卡岩和锡石_硫化物两类矿石组成。文章在研究和介绍矿床地质特征的基础上,对早期形成的矽卡岩矿石中的5个辉钼矿样品进行了Re_Os年龄测定,获得矽卡岩期成矿年龄为(224.0±1.9)Ma(n=5,MSWD=0.54),表明早期成矿作用发生在印支期,这是首次在南岭地区确认存在中生代早期锡矿化作用。晚期锡石_硫化物成矿作用中,燕山晚期的花岗斑岩脉被卷入其中,表明区内还存在燕山晚期的第二次叠加成矿作用。

The Hehuaping tin-polymetallic deposit, a large tin ore field newly discovered in Southern Hunan, consists of skarn and cassiterite-sulfide ores. At present, the controlled reserves amount to about 110 700 tons of tin, 10 000 tons of bismuth, 50 000 tons of lead, and 10 000 tons of zinc. With the advance of the exploration work, four ore bodies have been explored, which are located in the southeast portion of Wangxianling Indosinian granite pluton and hosted in granite, granite porphyry, and Devonian limestone and sandstone, respectively. Re-Os dating of molybdenites yields model ages between （223.3 ± 2.9） and （225.2 ± 2.7） Ma and an isochron age of （224.0±1.9） Ma for the skarn ore related to Wangxianling granite, indicating that W-Sn mineralization in southern Hunan also took place in Indosinian period. The zircon SHRIMP U-Pb dating of the late granite porphyry is （142 ± 3） Ma. The granite porphyry has been partly mineralized and altered, and contains tin ore bodies. All this implies that there existed late mineralization of Yanshanian period in Hehuaping area. The early mineralization is supposed to correspond to underplating of the basic magma.