Collaborative Research: Pressure Decrease as a Cause of Quartz and Molybdenite Vein Mineral Precipitation in Magmatic-Hydrothermal Systems

合作研究：压力降低是岩浆热液系统中石英和辉钼矿脉矿物沉淀的原因

• 批准号: 0440324
• 负责人: Scott Wood
• 金额: $ 15.13万
• 依托单位: Regents of the University of Idaho
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-02-01 至 2008-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0440324&HistoricalAwards=false
• 关键词: Collaborative; Research; Pressure; Decrease; Cause

In high temperature geothermal systems, and magmatic hydrothermal systems such as the porphyry copper deposit at Butte, Montana, sharp decreases in pressure from lithostatic toward hydrostatic are a likely process for producing quartz veins. The nearly universal occurrence of molybdenite (MoS2) in such quartz veins that likely form by pressure drop and the scarcity of molybdenite in other vein types suggest that molybdenite, like quartz, precipitates by pressure reduction, as opposed to a decrease in temperature. Previous molybdenite solubility experiments have not addressed the role of pressure, thus we do not know a chemical mechanism that would cause molybdenite to precipitate upon a drop in pressure. For quartz, we know its solubility as a function of pressure, but we do not know the origin of quartz mineral and trace element compositions that distinguish pressure-drop vein quartz from other types of quartz. This research addresses pressure decrease as a key process in magmatic hydrothermal systems in three coordinated sub-projects: (1) experiments in the Wood laboratory (U. Idaho) to explore molybdenite solubility as a function of pressure and temperature, (2) in the Reed laboratory (U. Oregon), determine the SEM-cathodoluminescence textures and related trace element compositions, 18O/16O ratios and fluid inclusion properties in natural vein quartz formed by pressure drop and other processes; and (3) apply numerical modeling methods (program CHILLER) to explore the role of pressure-decrease in magmatic hydrothermal systems. Benefits beyond the research itself include the following: a) graduate students and two undergraduates would be trained in the analytical, experimental, and computational methods involved in modern geochemical research; b) the Reed-Wood research collaboration joins complementary strengths in experimental, analytical and numerical modeling geochemistry that would aid future developments in geochemistry; c) a deeper understanding of magmatic hydrothermal processes is important for mineral exploration and for future energy extraction from high-temperature (400 degrees C), high-yield geothermal systems, such as that now being drilled in Iceland.

在高温地热系统和岩浆热液系统中，例如蒙大拿州的比尤特（Butte）的斑岩铜沉积物（Porphyry Copper）沉积物，从岩性静脉音静电降低的压力急剧降低是产生石英静脉的可能过程。 在这种石英静脉中，钼酸酯（MOS2）几乎普遍发生，这种石英静脉可能是由于压降而形成的，而其他静脉类型中钼酸盐的稀缺性表明，像石英这样的钼酸盐通过减压，与温度降低相反。 以前的钼酸盐溶解度实验尚未解决压力的作用，因此我们不知道一种化学机制会导致钼酸群在压力下降时沉淀。 对于石英，我们知道它的溶解度是压力的函数，但我们不知道将压力脱水石英与其他类型的石英区分开的石英矿物质和微量元素组成的起源。这项研究解决了三个协调的亚项目中岩浆水热系统中的压力下降：（1）木材实验室（美国爱达荷州）进行的实验，以探索钼酸盐溶解度作为压力和温度的函数（2），（2）在REED实验室（U. oregon）中的函数（2），确定属于sem-callimifient的概述，并确定相关的概述概念概念均匀的概述，并构成了18个概念概念，并构成了18个概念概念概念，并构成了18个概念概念，并确定了18个概念的概念，并确定了18个概念的概念，并确定了18个概念概念的概念，并确定18个概念的概念，并确定18次概念。自然静脉石英由压降和其他过程形成； （3）应用数值建模方法（程序冷却器）来探索压力减少酶在岩浆热液系统中的作用。 研究本身以外的好处包括：a）研究生和两名本科生将接受现代地球化学研究涉及的分析，实验和计算方法的培训； b）Reed-Wood Research合作将实验，分析和数值建模地球化学的互补优势加入，这将有助于地球化学的未来发展； c）对岩浆热液过程的更深入的了解对于矿物探索和从高温（400度C），高收益地热系统（例如现在在冰岛钻取的高温地热系统）至关重要。