Türkiye Jeoloji Bülteni

A New Fe-Oxide-Cu-Au (Olympic Dam Type) Perspective To Skarn Type Iron Oxide Mineralization In Sivas-Divriği Region

Abstract: The Fe-oxide-Cu-Au deposits are characterized by large masses of Ti-poor Fe oxides related to petvasivealteration processes such as magnetite or hematite. Besides, they are characterized by pervasive sodic and potassicalteration, and higher abundances of REE compared to porphyry and skam types. This study deals with thecomparison of the Fe-oxide-Cu-Au deposits with those of Fe-oxide mineralizations in Divriği region. In doing so,well-known alkaline metasomatism, mineralogy, late stage sulfide mineralization, tectonic setting of plutonic rocksand structural control characteristics unique to Fe-oxide-Cu-Au deposits were used.The authors of this paper initiated the studies in recognition of Fe-oxide-Cu-Au deposit type in Turkey. This studyshows that A -B-kafa mineralizations at Divriği (Sivas) occur in metasomatic plutonic rocks that were experienced anextensive and pervasive alkaline metasomatism. The early stage of metasomatism is related to sodic-calcic alteration.This stage is followed by a late and/or shallower potassic alteration. Products of potassic alteration superimpose theproducts of sodic-calcic alteration. Therefore, the alteration products and style of mineralization suggest-that thedeposits long known as pyrometasomatic, felst calc-skarn and skam might be of Fe-oxide-Cu-Au type. The A-kafamineralizations occur as massive magnetite mineralizations hosted by a K-feldspar and phlogopite-rich zonesuperimposing scapolite-garnet zone. B-kafa mineralizations consist of martitized magnetite, limonitizcıtion,silicification, and sulfide mineralizations, and are regarded as late-stage alteration products. These are observed in astructurally controlled and funnel shaped settings that might be regarded as breccia pipes or diatremes. The granitoidsclose to brecciated zone is characterized by extensive serialization. Colloform barite formations develop particularlyalong contacts between brecciated limestone and sericitized rocks.Although, the examples of the similar deposit types have not been recognized yet in Turkey, pervasive alkalinemetasomatism and relationships between mineralizing events and alkaline metasomatism, the oxide and sulfidemineralogy, morphology and distribution of the iron oxide deposits in and around the Divriği (Sivas) suggest that itshows characteristics similar to Fe-oxide-Cu-Au deposits. Therefore, they could be re-defined as Fe-oxide-Cu-Autype mineralizations on the basis of alteration pattern and mineralization styles. It is also proposed that these depositshave gold and copper potential, and the exploration programs should be re-designed so as to investigate this potential.