University of Twente Student Theses


Geochemical and spectral characterization of hydrothermal alteration facies at the epithermal gold mineralization at Rodalquilar, Spain

Chororoka, Kamina (2012) Geochemical and spectral characterization of hydrothermal alteration facies at the epithermal gold mineralization at Rodalquilar, Spain.

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Abstract:Epithermal gold deposits are a type of lode mineral deposits consisting of economic concentrations of Au ± Ag and base metals. These deposits form in a variety of host rocks from ascending hydrothermal fluids, primarily by replacement and/or by open-space filling. The present study aims to test whether direct field data of major and trace elements can be used in combination with mineralogical IR information for the exploration of the epithermal gold deposits. 89 rock-samples were available for portable XRF and ASD spectral measurements, these samples were collected in 2004 along two perpendicular traverses by ITC students over the Rodalquilar epithermal gold deposit. Rodalquilar Gold Mine forms part of the Cabo de Gata National Park area which is located close to the coast in the Almeria Province in the south-eastern part of Spain. The total area covered in this study is approximately 56 km2.Fine rock powder samples for XRF analysis, were prepared by grinding the samples using a Tema disk mill and a mullite hand mortar. Rocks in the study area range in compositions from andesite to rhyolites. Element concentrations of major and trace elements together with mineralogical information were used to study the lithological differences and alteration style/intensity on the study area. Positive correlations between SiO2, Al2O3, TiO2, Zr, and Sr are observed which is linked to the lithological association, also a positive correlation is observed between As and S which is associated with mineralization. The portable XRF results show that Zr and Ti are the most suitable elements to discriminate andesites and rhyolites lithologies. The Silicification and Hashigushi Indices calculated from the whole rock geochemistry, proved to be most effective in delineating argillic-advanced argillic alteration styles for the epithermal deposits. Spectral NIR detectable parameters such as kaolinite crystallinity and mineral chemistry (Al-OH position and depth) indicate the potential application of reflectance spectroscopy in the characterizing alteration and elements associations within the Rodalquilar study area. Kaolinite crystallinity shows a special pattern, whereby the highly altered mineralized areas are characterized by low value of the crystallinity index and the least altered, peripheral zone is characterized by high values of this index. It is shown also that the central part, which is the highly mineralized part of the study area, is dominated by higher depth of the Al-OH absorption feature at 2200nm as compared to the surrounding area The overall results indicate that by using data obtained with a portable XRF and a NIR field spectrometer, it is possible to differentiate between lithologies, different alteration styles and intensities. In addition the Zr- Ti relationship can be used to characterize different volcanic lithologies in an epithermal gold environment. setting like Rodalquilar.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
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