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Spatial and temporal evolution of fluids in hydrothermal ore deposits

Magmatic-hydrothermal systems typically have vertical extents of several hundred<br />meters and their geochemical characteristics (e.g. mineral assemblages) vary considerably<br />over that vertical extent. As a consequence the expression in outcrop varies depending on<br />the level of erosion. Therefore understanding the geochemical zonation of magmatic-hydrothermal<br />ore deposits opens the possibility to detect deep magmatic-hydrothermal<br />systems, and to assess qualitatively the degree of erosion that has taken place in the area<br />and at which level the mineralization may occur. This dissertation presents the<br />characterization of two shallow hydrothermal systems and their potential relations with<br />deeper magmatic-hydrothermal systems. In addition, this dissertation develops the<br />equations to directly interpret thermometric data from the fluid inclusion type dominant in<br />one of those deposits (fluid inclusions that homogenize by halite disappearance).<br />Red Mountain, AZ is a porphyry copper system with a well-preserved lithocap<br />providing an ideal candidate to characterize the shallow expression of porphyry copper<br />systems in the southwestern US. The distribution of fluid inclusions, alteration mineralogy<br />and grade indicate that the intrusive responsible for the mineralization was only partially<br />intercepted during the exploration program and that one single magmatic event was likely<br />responsible for the mineralization detected. Fluid inclusion types and clay minerals are<br />systematically distributed within the deposit. The fluid responsible for the shallow<br />hypogene mineralization was a low pH-intermediate temperature-low density fluid while a<br />high salinity fluid was responsible for deep mineralization.<br />Wutong is a Pb-Zn-Ag deposit in the Nanling belt (southeast China). The combination<br />of fluid inclusion and mineral thermometry indicates that the Wutong deposit formed at<br />relatively low pressures. The age and isotopic composition of the mineralization indicates<br />that the deposit formed during the Cretaceous from crustal derived fluids. The occurrence<br />of a shallow magmatic-hydrothermal system of Cretaceous age in this region suggests that<br />Cretaceous intrusions, despite not outcropping very commonly in this particular region may<br />occur at deeper levels. / Ph. D.

Identiferoai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/50960
Date10 June 2013
CreatorsLecumberri Sanchez, Pilar
ContributorsGeosciences, Bodnar, Robert J., Newton, Maury Claiborne, Kamilli, Robert Joseph, Lowell, Robert P., Westman, Erik C.
PublisherVirginia Tech
Source SetsVirginia Tech Theses and Dissertation
Detected LanguageEnglish
TypeDissertation
FormatETD, application/pdf, application/pdf
RightsIn Copyright, http://rightsstatements.org/vocab/InC/1.0/

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