Original paper

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

Kadir, Selahattin; Karakaş, Zehra


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.


alterationfeldsparhalloysiteignimbritekaolinitesmectiteturkeyvolcanic glass