Mineralogical, geochemical and isotopic characteristics of Quaternary calcretes in the Adana region, southern Turkey: Implications on their origin


Kaplan M. Y. , EREN M., KADİR S., Kapur S.

CATENA, cilt.101, ss.164-177, 2013 (SCI İndekslerine Giren Dergi) identifier identifier

Özet

Calcretes are widespread, and form as nodular, columnar/tubular, fracture-infill, laminated hardpan and conglomeratic crust in the Adana region. X-ray powder diffractometry (XRD), scanning electron microscopy and energy-dispersive analyses (SEM-EDX) and differential thermal analysis-thermal gravimetry (DTA-TG) reveal that calcretes and their host-rock mudstones are composed predominantly of calcite and smectite, respectively. The other minerals determined in the samples are palygorskite, quartz, and feldspar. Palygorskite is a minor component of the calcretes. The inductively coupled plasma atomic emission spectroscopy (ICP-AES) analyses reveal that the calcrete samples are characterized by high CaO and LOI values whereas the host-rock mudstones contain relatively high values of SiO2, Al2O3, Fe2O3 and MgO. The cross-plots of SiO2-Al2O3, CaO-SiO2, CaO-MgO and CaO-Fe2O3 show positive and negative correlations. Their gradual change is due to the degree of the progressive calcretization causing mudstone replacement. The delta O-18 and delta C-13 values range from -3.8 to -5.7 (mean -4.4) and from -7.7 to -10.0 (mean -8.6)parts per thousand PDB, respectively which are consistent with values of pedogenic calcretes reported in the literature from worldwide sites. The delta O-18 values indicate formation from meteoric water either by replacement or precipitation at estimated temperatures from similar to 21 to 23 degrees C. The delta C-13 values are typical for pedogenic calcretes, reflecting development under the C3-dominated vegetation cover and semiarid or seasonally arid climatic conditions. (c) 2012 Elsevier B.V. All rights reserved.