海南岛抱伦金矿床成矿后断裂活动及找矿方向探讨

Post-mineralization Fault Activities and Implications in Ore Prospecting of the Baolun Gold Deposit, Hainan Island

抱伦金矿是大型以含金石英脉为主的金矿床,赋矿围岩是下志留统陀烈组浅变质碎屑岩,矿脉走向为北北西向。北东走向的F_2断层将各条矿化带分成北段和南段。在F_2断层两盘很大范围内,北西盘是陀烈组下段岩石,南东盘是陀烈组中段岩石。在巷道中见到多条伴生的切错含金石英脉的小型北东向左行扭动断层。据此认为F_2断层是大断距左行扭动的成矿后断层;南矿区开采的矿化带与其北侧的4号矿化带北段不是同一条矿化带;各条矿化带的南段相对于它们的北段有较大断距的左行错移。由此得出本矿区的构造格架是:被成矿后北东向断层切断并大断距左行错移的多条北北西向矿化带。在此新的构造概念下,对抱伦金矿的进一步找矿方向提出了四个推断,涉及寻找1号矿化带南段、北区疑4号带、其他一些矿化带南段和F_2断层两盘陀烈组下段和中段界线。

The Baolun gold deposit is a large-size quartz vein type Au deposit hosted in a suite of low-grade metamorphosed clastic rocks of the lower Silurian Tuolie Formation. The deposit comprises a series of NNW-trending ore veins. The NE-trending fault F2 traverses the deposit, and divides every major auriferous veins into northern and southern segments. The NW and SE sides of the F2 fault are mostly the lower and middle parts of the Tuolie Formation respectively. In the mining tunnel, numerous sinistral small-scale NE-trending faults crosscut the auriferous quartz veins. Therefore, it is clear that the F2 fault is a post-mineralization large-scale strike-slip fault which cut all of auriferous veins with a left-lateral movement. As a result, the No.4 mineralized zones in the northern parts and southern parts of the mining area could not be a continuous ore zone as was previously believed. The structural framework of the mining area is characterized by a number of NNW-trending mineralized zones that cut and significantly displaced by a NE-trending post-mineralization fault. Under such tectonic regime, four target areas are proposed for further exploration:(1) the southern part of the No.1 mineralized zone,(2) the northern part of the suspicious No.4 mineralized zone,(3) the southern segments of the other mineralized zones, and(4) the boundaries between the lower and the middle members of the Tuolie Formation in the either sides of F2 fault.