Zehra Karakaş

Mineralogy, chemistry and origin of halloysite, kaolinite and smectite from Miocene ignimbrites, Konya, Turkey

Ignimbirites are widespread in the south-southwest of Konya. These units are dominated by dissolved and fractured volcanic glass and feldspar, associated with halloysite, kaolinite and smectite. These units exhibit hypocrystalline poryphyritic texture, dominated by interconnected irregular coarse-grained pores in complex networks and cryptocrystalline texture, dominated by independent fine pores. Micromorphological and textural differences create different physico-chemical environments due to the mobility of the elements released by the diagenetical alteration of volcanic glass as well as feldspar. Thus, the largest interconnected pores create permeable pathways, resulting in the mobility of Ca, Na and Mg type mobile elements and, consequently, in the reduced salinity and alkalinity of the environment and in the enrichment of the elements Si and Al, which led to the formation of halloysite and kaolinite. Permeability is reduced and water is very slow flowing or stagnant in fine pores where the mobile elements can not move, which increased salinity and alkalinity, favouring the formation of smectite rather than halloysite and kaolinite.

Mineralogical and genetic relationships between carbonate and sepiolitepalygorskite formations in the neogene lacustrine Konya basin, Turkey

Neogene (Upper Miocene-Pliocene) lacustrine sediments of northern Konya consist of conglomerate, sandstone, marl, mudstone, claystone, clayey limestone, and limestone. Limestones are white, beige-cream colored, fine-grained and contain remnants of plant roots. Brecciation, calcretion, mud cracks, and dissolution voids are common. Claystones are typical with white and green colors. Green claystone cropping out at the lower part of the sequence is alternated with mudstone and sandstone. White claystone alternating with carbonate units appears at the upper part of the sequence. Carbonate units are found as intercalated layers and lenses of conglomerate, sandstone, and mudstone.Calcite, dolomite, feldspar, and quartz minerals are dominant in the study area. They are accompanied by sepiolite, palygorskite, smectite, chlorite, and illite minerals hosted by white colored clayey limestone and claystone. In addition, on the green colored claystones, minerals such as chlorite, smectite, and illite are formed.SEM studies indicate that sepiolite-palygorskite fiber and fiber bundles cover calcite and dolomite. Calcite and dolomite are of hexagonal and rhombic crystal types. These minerals show a meniscus type cement which characterizes a vadose zone.Paragenesis and textural features of the minerals determined in the study area indicate that precipitation should occur due to climate fluctuations ranging from arid, semi-arid, and wet conditions. Changes in climatic conditions does affect the lacustrine water chemistry and precipitation of carbonate and detrital units. Sepiolite and palygorskite form authigenically as a result of the calcretion of carbonate units in alkaline conditions, high Si and Mg activity, and low Al.

The interference of a deep thermal system with a shallow aquifer and health risk assessment: the case of Sandıklı (Afyonkarahisar) Basin, Turkey

A mixture of geothermal waters having high ionic concentration to cold water aquifers is caused to deterioration at irrigation and drinking water quality. The aim of this study is determine spreading and extending of pollution in cold groundwater with the contribution of geothermal waters in the Sandıklı (Afyonkarahisar) basin. Hydrochemical facies of the waters is Ca–Mg–HCO3 and Ca–Mg–HCO3–SO4 in cold waters and Na–Ca–SO4–HCO3 in the geothermal waters, respectively. Ca2+ and HCO3− are dominant ions in cold waters, whereas those in geothermal waters are Na+ and SO42−. Shallow groundwaters have low ionic concentrations, while deep circulation waters have high ionic concentrations. The increases of T, EC, Na+, SO42−, Cl−, B, Al, As, Fe, Mn, Ni, F, U and NO3− parameters were determined in the cold groundwaters as locally due to hydrothermal contribution, water–rock interaction and anthropogenic effects in the Sandıklı basin. As a related to groundwater usage, there are two different risks in the basin, human health risk (drinking water usage) and environmental risk (irrigation water usage). From the results of hazard index, it is verified that As is the main contaminant, and toxic human risk can be caused by ingestion of water in the basin.