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

9815032巴顿富铁氧化物（-Cu-Au-REE）热液系统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。 近年来，在澳大利亚奥林匹克大坝（Olympic Dam）巨型存款的发现的刺激下，人们把注意力集中在三种可能的成因上：（1）这些存款基本上是岩浆成因的，是由从地球化学特征独特的岩浆中分离出来的富含氧化物的不混溶熔体形成的;（2）矿床为岩浆源卤水热液型矿床，与斑岩型铜-钼矿床有很大的相似性，（3）矿床为岩浆热驱动的热液矿床，但其成因为明显的地表或近地表高盐度非岩浆卤水。这些假设的意义是重大的。这两种岩浆假说都与特定的岩浆活动类型和构造环境有关。相反，非岩浆流体假说预测与含盐地表水或地下沃茨相关，因此与气候有共同的直接联系。该项目建立在早期工作的基础上，以测试非岩浆流体与岩浆连接的重要性。将结合实地的地球化学、岩石学和理论方法，调查流体的来源、金属的来源以及金属可能或不可能以经济上有意义的数量富集的机制。大多数实地和分析工作将在美国和墨西哥的发生与全球综合太古代到现代的例子相结合。这项研究的一个更广泛的意义是，这些含盐热液系统可能为古代干旱气候提供直接证据。这在没有保存独立记录的情况下可能很重要，例如来自沉积岩的记录。

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.