贵州交犁-拉峨汞矿床方解石Sm-Nd同位素年代学

三丹汞矿带位于贵州省南部,是继湘黔汞矿带之外西南大面积低温成矿域内发现的又一重要汞矿带。因此,阐明带内汞矿的成矿物质来源、成矿时代及成矿动力学背景等问题,对深入探讨西南大面积低温成矿域的形成机理有着重要的作用。热液方解石是带内汞矿床的主要脉石矿物之一,作者尝试对三丹汞矿带中段交犁-拉峨汞矿床中的热液方解石进行Sm-Nd同位素测年,获得等时线年龄为(129±20)Ma,MSWD=0.21,εNd=-12.9,说明成矿作用主要发生在燕山晚期。该年龄的报道为深入探讨汞矿床以及西南大面积低温成矿域的形成和演化提供了重要的信息和依据。结合前人研究认为,西南低温成矿作用主要存在两期,早期为145~155 Ma的Sb成矿作用,晚期为120~135 Ma的Sb、Au、Hg、As成矿作用。围岩下奥陶统锅塘组灰岩样品的εNd值为-12.6,与方解石εNd值极为接近,指示该矿床成矿物质可能主要来自奥陶系赋矿海相碳酸盐岩。

Sm Nd Dating of Hydrothermal Calcites from Jiaoli Lae Mercury Deposit,Guizhou Province

San Dan mercury metallogenic belt is one of the most important parts of the large‐scale low‐temperature epithermal metallogenic region in Southwestern China , besides Guizhou - Hunan mercury metallogenic belt .To clarify the source of metallogenetic materials ,mineralization ages ,and geodynamical background is critical for understanding the mineralization mechanism of this region . Considering that the hydrothermal calcite is one of the main gangue minerals of this belt ,Sm Nd geochronology of hydrothermal calcites is used to date Jiaoli Lae mercury deposit in the middle of the belt .An isochron age (129 ± 20 Ma , MSWD = 0 .21 , εNd = - 12 .9 ) has been obtained . This age suggests that the Hg mineralization occurred in Late Yanshanian . This provides some important information and clues to discover the formation and evolution of the mercury deposits and other deposits of the large‐scale low‐temperature epithermal metallogenic region in Southwestern China .Referring to some other previous research ,we conclude that this area underwent two main mineralizing stages ,i .e ., early stage of 145 155 Ma Sb mineralization , and late stage of 120 135 Ma Sb , Au , Hg , As mineralization .The limestone εNd value of wall rocks of the Guotang Formation (Lower Ordovician Series) is - 12 .6 ,which is in good agreement with the εNd of the hydrothermal calcite .This indicates that the ore materials of this mercury deposit probably originated from the ore‐bearing Ordovician carbonatite .