1Dokuz Eylü l Ü niversitesi, Jeoloji Mü hendisliǧ i Bö lü mü , Buca, İzmir, Turkey 2 Hacettepe Ü niversitesi, Jeoloji Mü hendisliǧ i Bö lü mü , Beytepe, Ankara, TurkeyThe Mihalıççık region (Eskişehir) in NW Turkey includes an ophiolitic assemblage with a serpentinite-matrix mélange. The serpentinites of this mélange host silica-carbonate metasomatites which were previously named as listvenites. Our mineralogical and geochemical studies revealed that these alteration assemblages represent members of the listvenitic series, mainly the carbonate rocks, silica-carbonate rocks and birbirites, rather than true listvenites (sensu stricto). Tectonic activity and lithology are principal factors that control the formation of these assemblages. Carbonatization and silicification of the serpentinite hostrock is generated by CO 2 , SiO 2 -rich H 2 O hydrothermal fluid which includes As, Ba, Sb and Sr. Low precious metal (Au, Ag) contents of the alteration assemblages indicate lack of these metals in the fluid. Primary assemblages of the alteration are carbonate rocks that are followed by silica-carbonate rocks and birbirites, respectively. Petrographic studies and chemical analyses suggested an alkaline and moderate to high temperature (350-4008C) fluid with low oxygen and sulphur fugacity for the carbonatization of the serpentinites. The low temperature phases observed in the subsequent silicification indicated that the fluid cooled during progressive alteration. The increasing Fe-oxide content and sulphur phases also suggested increasing oxygen and sulphur fugacity during this secondary process and silica-carbonate rock formation. The occurrence of birbirites is considered as a result of reactivation of tectonic features. These rocks are classified in two sub-groups; the Group 1 birbirites show analogous rare earth element (REE) trends with the serpentinite host-rock, and the Group 2 birbirites simulate the REE trends of the nearby tectonic granitoid slices. The unorthodox REE trend of Group 2 birbirites is interpreted to have resulted from a mobilization process triggered by the weathering solutions rather than being products of enrichment by the higher temperature hydrothermal activity. Copyright # 2006 John Wiley & Sons, Ltd. One of the important concerns of mineral research and exploration are the alteration products that are valuable indicators for exploration geologists. Hydrothermal/metasomatic alteration products, that is metasomatites, are naturally related to the mineralogy of the host rocks and the fluid nature. Infiltration of hydrothermal fluids in ultramafic terrains results in significant and a wide spectrum of metasomatites which are documented by several authors (e.g. Rose 1837Rose , 1842Murchison et al. 1845;Lodochnikov 1936; Borodayevskiy and Borodayevskiy GEOLOGICAL JOURNAL Geol. J. 41: 557-580 (2006) Copyright # 2006 John Wiley & Sons, Ltd. 1947Bok 1956;Ploshko 1963; Allakhverdiev 1965, 1971;Shcherban 1967;Shcherban and Borovikova 1969;Abovian 1978;Kuleshevich 1984;Ivan et al. 1985;Buisson and Le...

Suitability of the Ağla-Köyceğiz dunites for manufacturing olivine bricks was assessed by addition of the Kümaş fine sintered magnesia in 10, 20, 30 and 40% proportions. The average value of MgO for Ağla dunites is around of 46wt.%. Magnesium sulphate was used as a chemical binder and gets good resistance to the mixes before firing. High Fe 2 O 3 content of the Ağla dunites help to sintering process. Addition of the sintered magnesia and magnesium sulphate to the mixes increases MgO/SiO 2 ratio. Phase composition, bulk density and cold crushing results at 1625ºC show that these mixes are not mature ceramic.