University of Twente Student Theses


Surface Mineralogical-Geochemical Characteristics of the Palai-Islica Epithermal-Au Deposit (SW Spain)

Belay, Ashebir Sewale (2010) Surface Mineralogical-Geochemical Characteristics of the Palai-Islica Epithermal-Au Deposit (SW Spain).

[img] PDF
Abstract:Epithermal deposits are near Earth surface deposits that are formed under low to moderate temperature pressure condition of hydrothermal processes. They are commonly classified into two types based on oxidation of sulfide that can determined by inferred specific characteristics but it shows a wide range of characteristics. The objective of this research is to characterize epithermal deposits using surface mineralogical and its geochemical characteristic in a case study at Palai-Isilica SE Spain, with sub objectives are; to map and characterize different alteration minerals, to identify the relationship between concentration of potassium with different alteration minerals using gamma-ray data, to identify and model the relationship between within multi-variant geochemical elements and with alteration minerals and to see how using compositional data analysis improves analyzing correlation within geochemical elements as compared to normal (classical) statistics. 178soil samples and 108 ground gamma-ray spectrometry survey stations using GR320 were collected. We used ASD spectrometry to identify type of mineral in soil samples. Seven elements (As, Cu, Pb, Zn, Sb Mn, & Fe) were analysed by ICP-OES analytical instrument from soil samples. Box plots, correlation matrix analysis, principal component analysis and interpolation of point data to identify these relationships were used. Illite is the dominating mineral among the identified minerals in the study area (illite, montmorillonite, halloysite gypsum, jarosite alunite and palygorskite), Only some clay minerals; illite, montmorillonite and halloysite could be mapped from Hymap imagery. The sulphate minerals (gypsum, jarosite and alunite) appear in micro veins within the clay minerals. That can indicate two stages of hydrothermal alteration. Gama-ray potassium shows a good contrast between epithermal alteration minerals and other type of alteration minerals but it does not show much contrast within zones of the epithermal alteration minerals. The spatial extent of some mineral is too limited to be measured by gamma-ray spectrometry and the numbers of samples for each type of mineral do not proper comparison. Both “normal” and compositional data analysis was used for the analysis of relationship between elements. ‘Normal’ statistical analysis leads a spurious result due to data closure. Compositional data analysis highly improves the relationship analyses between elements. Bivariant correlation matrix analysis between elements shows a significant correlation between As & Sb, Pb & Zn, Zn & Mn, and Mn & Fe. The component loading of principal component analysis also suggests there is a strong element association between As & Sb, Pb & Zn, and Zn&Mn, and also single loadings of Cu and Fe. This loading indicates different stages of mineralization took place in the study area. The relationship analysis between concentrations of elements and alteration minerals does not show a clear pattern. This is because of; the limitation that the numbers of samples for each type of mineral not comparable or sometimes iinsufficent, mixing of minerals in soil samples and the fact that mineral identification using ASD spectral measurements is not sufficiently complete (only dominant minerals are detected) for such a relationship analysis.
Item Type:Essay (Master)
Faculty:ITC: Faculty of Geo-information Science and Earth Observation
Programme:Geoinformation Science and Earth Observation MSc (75014)
Link to this item:
Export this item as:BibTeX
HTML Citation
Reference Manager


Repository Staff Only: item control page