Petrochemical Studies of Fe-Oxide (-Cu-Au-REE) Hydrothermal Systems

9815032富含氧化铁（-Cu-Au-REE）的热液系统在几个世纪以来一直具有重要的经济意义，其起源也一直是个谜。最近，在澳大利亚发现了巨大的奥林匹克大坝矿床的刺激下，研究工作集中在三种可能的起源上：(1)这些矿床基本上是岩浆，由从地球化学上独特的岩浆中分离出来的不混溶的富含氧化物的熔体形成；(2)矿床为热液型，由岩浆源卤水形成，大致类似于斑岩型铜钼矿床；(3)矿床为岩浆热液驱动的热液型矿床，但由独特的高盐度地表或近地表非岩浆卤水形成。这些假设的含义是重要的。两种岩浆假说都暗示了与特定类型的岩浆活动和构造环境的相关性。相反，非岩浆流体假说预测了与含盐地表水或地下水的相关性，因此与气候有直接联系。该项目建立在早期工作的基础上，测试了非岩浆流体与岩浆连接的重要性。将结合现场地球化学、岩石学和理论方法来研究流体的来源、金属的来源，以及金属可能或不可能集中到具有经济意义的大量的机制。大多数实地和分析工作将结合太古宙到现代例证的全球综合，在美国和墨西哥进行。这项研究的一个更广泛的含义是，这些含盐热液系统可能为古代干旱气候提供直接证据。在没有保存独立记录的地方，例如沉积岩，这可能很重要。

9815032BartonFe-oxide(-Cu-Au-REE)-rich hydrothermal systems have been of economic importance for centuries,and enigmatic in their origin for nearly as long. Recent work, stimulated by the discovery of the giant Olympic Dam deposit in Australia, has focused on three possible origins: (1) these deposits are fundamentally magmatic, formed by an immiscible oxide-rich melt separated from geochemically distinctive magmas; (2) the deposits are hydrothermal, formed from magmatic-sourced brines and can be considered as broadly analogous to porphyry Cu-Mo type deposits, and (3) the deposits are hydrothermal driven by magmatic heat, but generated from distinctive high-salinity surface or near surface, non-magmatic brines. The implications of these hypotheses are significant. Both magmatic hypotheses imply a correlation with particular types of magmatism and tectonic environments. In contrast the non-magmatic fluid hypothesis predicts a correlation with saline surface or ground waters thus a common direct link to the climate. This project builds on earlier work to test the importance of non-magmatic fluids versus the magmatic connection. A combination of field-based geochemical, petrological and theoretical approaches will be used to investigate the sources of fluids, the sources of metals, and the mechanisms whereby the metals may or may not be concentrated in economically significant quantities. Most field and analytical work will be done on U.S. and Mexican occurrences in combination with a global synthesis of Archean to Modern examples. One of the broader implications of this research is that these saline hydrothermal systems may provide direct evidence for ancient arid climates. This could be important where an independent record, for example from sedimentary rocks, is not preserved.