GEOCHEMICAL PROPERTIES OF DEMİRÖREN/GÜMÜŞHANE QUARTZ PORPHYRY ROCK AND RELATED SKARN- METASOMATISM

Abstract

The aim of this study is to geochemically investigate the skarn/metasomatism (S/M) formations due to granitic rock outcropping in Demirören (Gümüşhane-Türkiye) area. For this purpose, samples were taken from the area for geochemical and fluid inclusion studies and analyzed. It was determined that the development of (S/M) in the field was predominantly developed in Upper Cretaceous volcanic rocks, whereas hydrothermal alteration processes were dominant in Middle-Late Eocene volcanic rocks. When the Upper Cretaceous volcanic rocks exposed to S/M were geochemically evaluated, it was found that they were rocks in the characteristics of basaltic andesite, trachy-andesite, andesite, and were predominantly in the subalkaline calc-alkaline series. While these rocks are not enriched by heavy rare earth elements according to NMORB, it has been determined that they are enriched 10 to 100 times by light rare earth elements. When compared to chondrite, a 10-times enrichment was observed by heavy rare earth elements, and up to 100-times enrichments were detected in rocks outside the (S/M) zone by incompatible elements. In the fluid inclusion studies, it was determined that the fluids in the process of S/M had a salinity of 8.4% to 25.6 NaCl equivalents and homogenization temperatures in the range of 230-370 oC. When geochemical and fluid inclusion data are evaluated together, it was concluded that the skarn/metasomatism formations in the Demirören area have developed within the basalt-andesite belonging to the Upper Cretaceous aged volcano-sedimentary sequence and the pyroclasts of these rocks. The S/M developed in the late phase of quartz porphyry intrusion and/or after its emplacement, relatively high salinity (8.4 to 25.6% NaCl equivalent) and temperatures between 230-370 oC.