Geochronology of Hydrothermal Systems Related to Ore Mineralization

本项目将新改进的40Ar/39Ar定年技术应用于大型热液系统的定年问题。最近对40Ar/39Ar方法的改进表明，该技术甚至可以处理最细粒度的材料。该项目将集中在五个研究领域：a)巴拿马Cerro Colorado斑岩铜矿；b)具有Rb-Sr年龄信息的密西西比河谷型（MVT）矿床；c)沉积型微米金矿床，内华达州（Twin creek）；d)西班牙阿尔马登水星区；e)纳米比亚的Tsumeb-Kombat烟囱矿床。已收集了所有五个地点的样本。Cerro Colorado矿床与粗粒矿物有关，这些矿物已经用K-Ar测定了年代，这将为细粒蚀变产物的年龄提供一个很好的测试。MVT矿床已经具有高质量的Rb-Sr年龄，从而为该体系提供了进一步的测试。其余三个地点对存在的年龄进行了排列，但对热液活动的时间却很少有共识。正是通过这些站点，该项目应该提供最大量的新信息。

9526673 Hall This project applies newly refined 40Ar/39Ar dating techniques to the problem of dating large scale hydrothermal systems. Recent improvements in the 40Ar/39Ar method have demonstrated the potential for this technique to handle even the finest-grained material. This project will concentrate on five study areas: a) the Cerro Colorado porphyry copper deposit, Panama; b) Mississippi Valley-type (MVT) deposits with pre-existing Rb-Sr age information; c) sediment-hosted micron gold deposits, Nevada (Twin Creeks); d) the Almaden mercury district, Spain; e) the Tsumeb-Kombat chimney deposits, Namibia. Samples for all five sites have been collected. The Cerro Colorado deposit is associated with coarse-grained minerals which have already been dated using K-Ar, and this will provide a good test for the ages derived from fine-grained alteration products. The MVT deposits have high quality Rb-Sr ages already available, thus providing a further test of the system. The remaining three sites have arrange of existing ages with very little consensus as to the timing of the hydrothermal activity. It is with these sites that the project should provide the greatest amount of new information.