Akademik Veri Yönetim Sistemi
OFIOLITI, cilt.21, sa.2, ss.125-130, 1996 (SCI-Expanded)
The silicified rocks (listwaenites) cropping out in the vicinity of the Karacakaya village (Sivrihisar-Eskisehir, Turkey) were formed by hydrothermal alteration of serpentinite after the emplacement (if ultrabasic rock. Listwaenites are observed along a fracture line oriented NW-SE and make up a steep topography in the field. The sole constituent of these rocks is quartz. Two distinct types of silicified rocks are determined based on their textural properties. In the first type, the sieve texture is somehow preserved. The second type of silicified serpentinite shows no sign of sieve structure. Opal veins and lenses found in fractures and joints are yellow, green, purple. and white in colors and consist of quartz, tridimite, cristobalite and goethite. MgO, CO2 H2O, Al2O3, CaO Ni and Co were lost: SiO2 total Fe, Na2O and Cr were gained, and MnO, K2O and TiO2 remained immobile during the alteration process of serpentinite. No metal enrichment was observed owing to this process. An and Co were found below detection limits: only in three samples Ag traces were found. Nevertheless, it substantially decreased in the altered rocks. A washing process through alteration probably caused Ni and Co to be removed from the rock.