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THE PHYSICAL CHARACTERISTICS OF PERIDOTITE AND AMPHIBOLITE BASED SOILS FROM KAHRAMANMARAS, SE ANATOLIA-TURKEY

Zekeriya KARA

Abstract

There is a close relationship between the soil characteristics and the parent material. Especially in arid and semi-arid regions where climate and vegetation cover are limited, soil properties are controlled by the parent material. Rock units which have different mineralogical, petrographical and geochemical features representing different parts of the ophiolitic sequence are widely seen in the vicinity of Kahramanmara? province. The ophiolite in the north of Kahramanmara? is generally represented by oceanic crustal sections, while the section in the south is represented mostly by sub-ophiolitic metamorphic rocks and mantle tectonites. The tectonites are represented by strongly serpentinized peridotites (harzburgite and lherzolite), where as the metamorphic sole rocks are made up of amphibolite and amphibole-schist. The rate of influence from their parent material is highly important for the soils formed on these units. In this study, the physical characteristics of soils formed on two different parent materials from south of Kahramanmara? were investigated. Soil samples were taken from 0-30 cm depth. Analysis of the unit Bulk Density (BD), water aggregate stability (WAS), dispersion ratio (DR), field capacity (FC), permanent wilting point (PWP), liquid limit (LL), plastic limit (PL), coefficient of linear extensibility (COLE) and organic matter (OM) were performed on the samples. The results obtained for the peridotite parent material were as follows: BD 1.37, WAS 57.49, FC 31%, PWP 18%, LL 56.61%, PL 31.52%, COLE 0.07 and OM 1.77%, while BD 2.16, WAS 40.14%, FC 21.9%, PWP 10.2%, LL 30.67%, PL 17.88%, COLE 0.04 and OM % 1.25 were obtained in the soil formed on the amphibolite parent material. In the statistical evaluation of the obtained data (according to the t test), LL, PL, BD, FC, PWP, DR and OM values were found to be different at the level of p <0,05. Peridotite type rocks lose their initial properties easily in a temperature of about 500 0C and in an aqueous environment by an alteration in the form of serpentinization which includes the transformations in the olivine and pyroxenes that they contain. The sub-ophiolitic metamorphic rocks in the study area are mainly represented by amphibolites were relatively less affected from the alteration than the peridotites. One of the most important factors affecting the alteration strength of minerals is the linking nature between tetrahedras forming silicates. Olivines and pyroxenes in the peridotitic rocks are known as neso and single-chain silicates respectively, and have the weakest tetrahedra connection in all the silicate groups, whereas the amphibole group minerals are known as double-chain silicates with stronger bond link than neso and chain silicates. These internal structural features of the minerals forming the different parts of the ophiolite unit are closely related to alteration causing significant differences in the physical characteristics of the soils formed on amphibolitic and peridotitic rocks representing the lower level of the ophiolite suite in the Kahramanmara? region.

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DOI resolver: doi.org/10.5593/sgem2018/3.2/s13.081

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