Modeling of lithology induced chemical anomalies in the aquifer systems of the Kazan Trona deposit area, Ankara, Turkey |
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| Authors: | M Zeki Camur Cevat Er Hasan Yazicigil |
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| Institution: | (1) Department of Geological Engineering, Middle East Technical University, 06531 Ankara, Turkey;(2) SRK Consulting and Engineering Inc, Turan Gunes Bulvari, No: 86/3, 06550 Yildiz, Ankara, Turkey |
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| Abstract: | The study was carried out in order to investigate existing hydrogeochemical relationships between groundwater environment
and geological units in the Kazan trona deposit area, Ankara, Turkey. Evaluations indicate that concentrations of alkalinity,
boron, chloride and sodium in the upgradient groundwater of the Eocene sedimentary units gradually increase toward downgradient
by the interactions of saline minerals (searlesite, shortite, northupite and pyrite) present in the secondary structures (microfractures
and irregular voids) at various levels. Inverse modeling calculations suggest that the range of dissolved mass amounts in
millimoles per kilogram of water for searlesite, shortite and northupite minerals are 0.05–28.67, 2.62–24.39 and 0.01–24.19,
respectively, in the aquifer between the upgradient and downgradient locations. The ranges of accompanying calcite and dolomite
precipitations are 4.54–48.71 and 2.16–24.08 mmol per kg of water, respectively. Chemical composition of the groundwater in
the overlying Neogene sedimentary unit includes also higher concentrations of the major ions as measured in groundwater of
the underlying units. However the lack of saline mineral zones in the Neogene unit indicates that upward groundwater mixing
takes place from the underlying aquifer as also suggested by the measured upward gradient. The mixing percentage of the underlying
groundwater as determined from the nested wells ranges from 2.7 to 48.3%, from upgradient to downgradient, respectively. The
unconfined alluvium aquifer overlying the Neogene unit includes relatively dilute groundwater except in two locations, where
high-ion concentrations detected in groundwater of the underlying units are also high in these locations, suggesting upward
groundwater mixing from the underlying aquifer due to upward gradient. However, groundwater input investigations from the
alluvium aquifer to the nearby Ova stream indicate that the detected high concentrations in these locations are diluted or
sorbed by the aquifer material toward downgradient (Ova Stream). |
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| Keywords: | Hydrogeochemistry Inverse modeling Groundwater Trona Kazan Basin |
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