Zoning and Age of Micron Gold Deposits

这里提出的研究涉及沉积物赋存的微米金(SHMG)矿床，这是大盆地中最大的化石热液系统(图1)，也是美国最重要的黄金来源。该项目将集中于以下方面：1)矿床规模分带；它可以提供关于SHMG成矿流体来源的信息，以及它们形成的温度、压力和地壳深度。2)这些矿床的年龄，这将阐明它们与岩浆热和水的关系，以及大盆地的构造演化。大部分研究将在新发现的Post SHMG矿床上进行，该矿床深度超过2500英尺。并含有大量未因风化和氧化而叠印的矿石。分区研究将包括矿物学、流体包裹体和稳定同位素测量。放射性年龄测量将使用实验真空石英管/总脱气40Ar-39Ar方法来分析不到1 mg的蚀变矿物分离，这些年龄将通过对矿前和矿后岩脉中的火成岩和蚀变矿物的常规40Ar-39Ar年龄测定进行核对，这些矿物是Post矿化的载体。我们的结果可以给出SHMG矿床的深度分带分类，可用于勘查和区域构造研究。

The research proposed here concerns sediment-hosted micron gold (SHMG) deposits, which are the largest fossil hydrothermal systems in the Great Basin (Fig. 1) and the most important sources of gold in the U.S. The project will focus on determination of: 1) deposit-scale zoning, which could provide information on the source of SHMG mineralizing fluids, as well as the temperature, pressure and crustal depth at which they formed. 2) the age of these deposits, which will clarify their relation to both magmatic heat and water, and the tectonic evolution of the Great Basin. Most of the study will be carried out on the newly discovered Post SHMG deposit, which extends to depths of over 2500 ft. and contains large volumes of ore that have not been overprinted by weathering and oxidation. Zoning studies will include mineralogical, fluid inclusion and stable isotopic measurements. Radiometric age measurements will use an experimental evacuated quartz tube/total degassing 40Ar-39Ar method to analyse less 1 mg of alteration mineral separates and these ages will be checked by conventional 40Ar-39Ar age determinations on igneous and alteration minerals in pre- and post-ore dikes, which bracket mineralization at Post. Our results could yield a depth-zoning classification for SHMG deposits, which could be used both in exploration and in regional tectonic studies.