南岭湘南吴家坪锡矿成岩成矿时代研究

    Diagenetic and mineralization chronology study of the Wujiaping tin ore deposit in Nanling Range

    • 摘要: 南岭吴家坪锡矿为湖南大义山地区近年新发现的具有中型以上远景规模的云英岩型矿床,矿体呈脉状产于大义山复式花岗岩体内部,受NE向断裂控制。为确定其成岩、成矿时代,总结大义山地区成矿规律,指导区域找矿及勘查工作,对赋矿围岩中粗粒斑状黑云母二长花岗岩(PM21-19)、中细粒斑状黑云母二长花岗岩(PM21-27)进行了LA−ICP−MS锆石U−Pb定年研究。测年结果表明,其成岩年龄为157.1 ± 1.1 Ma(MSWD = 0.55)和153.7 ± 1.2 Ma(MSWD = 0.55),属燕山早期。同时,获得云英岩型锡矿石中石英Rb−Sr等时线年龄为148.1±2.1 Ma(MSWD = 0.52)。结合区域资料认为,吴家坪锡矿成岩成矿时代为燕山早期,属南岭地区中生代成岩成矿高峰期(160 ~ 150 Ma)的产物。

       

      Abstract: Wujiaping tin ore deposit is a greisen-type deposit with medium-sized prospect scale newly discovered in Dayishan area in recent years. The orebody occurs as a vein in the Dayishan compound granite body and is controlled by NE-trending faults. In order to determine its diagenetic and metallogenic age, summarize the metallogenic regularity in Dayishan area, and guide regional prospecting and exploration, the LA-ICP-MS zircon U−Pb dating of medium-coarse grained porphyritic biotite monzonitic granite (PM21-19) and medium-fine grained porphyry biotite monzonitic granite (PM21-27) in ore-bearing surrounding rocks was studied. The diagenetic ages of 157.1 ± 1.1 Ma (MSWD=0.55) and 153.7 ± 1.2 Ma (MSWD=0.55) are obtained, which belong to the early Yanshanian period. At the same time, the Rb−Sr isochron age of quartz in the greisen-type tin ore is 148.1 ± 2.1 Ma (MSWD = 0.52). Combined with the regional data, the diagenetic and metallogenic age of Wujiaping tin ore deposit is the early Yanshanian period, which belongs to the peak of Mesozoic diagenesis and mineralization(160~150 Ma) in Nanling region.

       

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