| Abstract |
Kizildere Geothermal Field is located on the easternmost of the Büyük Menderes Graben, Western Turkey. This graben and several other grabens, which have been developed almost parallel to each other, are located at the easternmost of Aegean Extensional System. Among the several liquid dominated reservoirs hosted in fractured sedimentary and metamorphic rocks, this study focused on the reservoir in mica-schist units with secondary permeability. The REE mobility has been investigated considering mineralogy and geochemical composition of reservoir rock, in this high-enthalpy geothermal field. Drill cutting samples are collected as depth-dependently throughout a geothermal well. XRD analysis of the samples has been conducted to determine the mineralogical composition. REE compositions of the same samples have been determined using ICP-OES technique. This data evaluated along with the well-log data to assess the relations between mineralogy and REE composition within the scope of this study. Our data suggest that the samples can be divided into two groups as altered rocks caused by hydrothermal effects from fault zones, and unaltered rocks from outside of the fault zones. These grouping has been based on alteration mineralogy, and well-log data such as mud loss and temperature changes detected during drilling. According to XRD analysis, the major constituents of the samples are quartz, albite, muscovites, and chlorite. Illite, kaolinite, dickite, calcite, dolomite, and ankerite accompany to this primary mineralogy at the fault zones. REE compositions have been tested statistically to reveal the differences between these two groups are whether meaningful. PAAS-normalized REE results indicate that samples represent fault zones have not shown completely different patterns from out of the fault zone samples. The altered samples that secondary minerals identified in it, however, show meaningful negative Ce anomalies and lower normalization values. In the first sight, these can be indicated REE addition to the system with hydrothermal fluids. REE is retained mainly by secondary minerals in rocks and sorption on mineral surfaces. Although differences between two groups cannot be followed on (La/Lu)n, (La/Sm)n, and (Gd/Lu)n ratios, according to the result of the Mann-Whitney U test results, ∑REE differs between two groups statistically. It can be said that the difference of ∑LREE between two groups caused the regarding difference rather than the difference of ∑HREE. |