JOURNAL OF ASIAN EARTH SCIENCES, vol.40, no.2, pp.550-568, 2011 (SCI-Expanded)
A calcic skarn deposit occurs along the contact zone between Oligo-Miocene Cataldag Granitoid and Mesozoic limestones in Susurluk, northwestern Turkey. The skarn zone with little or no retrograde stage is represented by fluid inclusions with high homogenization temperatures (up to >600 degrees C) and a wide range of salinity (12 to >70 wt.% NaCl). Pluton-derived fluids facilitated occurrence of continuous pro-grade reactions in the country rocks (particularly in the proximal zone) and oxygen isotopic depletion in calc-silicate and calcite minerals. delta O-18 of anhydrous minerals within proximal and distal zones indicate that skarn-forming fluids had a magmatic origin. The delta O-18 values are 5.93-9.08 parts per thousand (mean 6.8 parts per thousand) for garnet, 4.08-9.94 parts per thousand (mean 6.49 parts per thousand) for pyroxene, 4.89-7.927 parts per thousand (mean 6.4 parts per thousand) for wollastonite and 6.65-8.28 parts per thousand (mean 7.5 parts per thousand) for vesuvianite. Temperatures estimated by isotopic compositions of mineral pairs are significantly lower than those measured from the fluid inclusions, indicating that isotopic equilibrium is not preserved between the skarn minerals. delta O-18 and delta O-13 values are systematically depleted from marbles to skarn carbonates. Calc-silicate forming reactions and permeability increase triggered by volatilization and consequent strong infiltration of H2O-rich siliceous fluids into the system promoted fluid-rock interaction causing isotopic resetting and isotopic depletion of silicates (e.g. pyroxene and wollastonite) and skarn calcites. (C) 2010 Elsevier Ltd. All rights reserved.