Turkish Journal of Earth Sciences






The Çelebi district is well known for its polymetallic Fe-W and Cu vein ores. These ores are hosted by calcic skarn zones, which are broadly classified as \"intrusive around skarn\" type. Both exoskarns (pyroxene-garnet) and endoskarns (epidote-pyroxene) occur in the district. The formation of endoskarns is manifested by complete replacement of plagioclase by epidote and pyroxene; the epidotized granitoids are regarded as incipient and/or early metasomatic products. The abundance of pyroxene in endoskarns tends to increase with plagioclase content and within the groundmass of the granitoids towards exoskarn zones. The increase in pyroxene is also coincident with the formation of anhedral, isotropic brown garnets. The garnet-rich pockets also mark irregular zones and veins of magnetite mineralization. The main magnetite mineralization occurs within the pyroxene-garnet exoskarn as 15 to 20-m-thick pockets and veins within pyroxene-rich zones. The pyroxene crystals are optically zoned and the composition ranges from hedenbergitic (core) to diopsidic (rim). Elemental compositions vary systematically in relation to skarn zones. A decrease in SiO_2 corresponds to an increase in FeO_(T) from granite toward skarn zones. The Çelebi district endoskarns are enriched in CaO, MnO, MgO and FeO_(T), yet depleted in SiO_2, TiO_2, Al_2O_3 and K_2O compared to the Çelebi Granitoid. CaO and FeO_(T) behave comparably in the endoskarns, suggesting that the iron mineralization is coincident with carbonization of prograde assemblages during retrograde alteration.


Çelebi (Kırıkkale), Skarn Zones, Magnetite, Geochemistry of Skarns

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