A Quantitative Method for Measuring Temperature-time Histories in Hydrothermal Magmatic Ore Systems

2010年，美国生产了价值超过8亿美元的钼氧化物，随着全球经济的复苏，作为高级钢合金剂的钼的需求可能会增加。世界上大部分的钼储量都包含在斑岩型铜（±钼）和斑岩型钼（±铜）矿床中。虽然斑岩钼矿床在体积上往往比斑岩铜系统小，但由于它们的矿石品位较高，仍然是钼的重要来源。了解斑岩型钼矿沉积对准确预测找矿时空分布具有重要意义。研究了与伴生岩浆作用相关的钼矿化时间和持续时间。该研究将有助于深入了解斑岩钼矿系统中矿石品位、蚀变地球化学和岩浆-热液结构的复杂变化。详细的铀/铅锆石（±钛铁矿）和氩/氩黑云母（±角闪石）定年将获得与美国西部斑岩钼矿床有关的深部岩体。此外，还将确定经济上重要矿床石英脉中辉钼矿的铼锇日期和流体俘获温度。这些数据将用于建立矿床的精确温度-时间历史和岩浆系统热成熟过程中的矿化时间。这些资料将有助于加强钼的勘探工作，钼是一种越来越有价值的国际商品。本文的研究结果将有助于我们更好地理解斑岩的成矿作用，并根据有关均质岩体增量组合的新假设，进一步发展铼锇组合地质年代学和流体包裹体测温作为一种广泛适用的热年代学工具。

In 2010, the United States produced over $800 million of molybdenum oxide, and the demand for molybdenum as an alloying agent in high-grade steel will likely increase as global economies recover. The majority of the world's molybdenum reserves are contained within porphyry copper (±molybdenum) and porphyry molybdenum (±copper) deposits. Although porphyry molybdenum deposits are often volumetrically smaller than porphyry copper systems, they are still a significant source of molybdenum owing to higher ore grades. Understanding porphyry molybdenum deposition is important for accurate predictions of spatial and temporal ore distribution during exploration. The timing and duration of molybdenum mineralization relative to associated magmatism will be investigated. The study will lend insight into the complex variations of ore grade, alteration geochemistry, and magmatic-hydrothermal textures observed within porphyry molybdenum ore systems.Detailed uranium/lead zircon (±titanite) and argon/argon biotite (±hornblende) dating of plutonic rocks associated with porphyry molybdenum deposits in the western US will be obtained. In addition, rhenium/osmium molybdenite dates, and fluid trapping temperatures for molybdenite in quartz veins from economically important deposits will be determined. These data will be used to establish precise temperature-time histories of the deposits and the timing of mineralization within the thermal maturation of the magma system. This information should be useful in enhancing exploration for molybdenum - an increasingly valuable international commodity. The results of this work should 1) enable better understanding of porphyry mineralization in light of new hypotheses regarding the incremental assembly of homogeneous plutons, and 2) further development of combined rhenium/osmium geochronology and fluid inclusion thermometry as a broadly applicable thermochronologic tool.