Geology, geochemistry, and geochronology of Fe-oxide Cu (± Au) mineralization associated with Şamlı pluton, western Turkey

Abstract

The Şamlı (Balıkesir) Fe-oxide Cu (±Au) deposit, one of several iron (+Cu±Au) deposits in western Turkey, is hosted by porphyritic rocks of the multi-phase Şamlı pluton and metapelitic–metadiabasic rocks of Karakaya Complex. Two successive mineralization events are recognized in the area as; i) early magnetite and sulfide and ii) late hematite–goethite-native copper (±Au). Alteration associated with the mineralization in Şamlı is characterized by four distinct mineralogical assemblages. They are, in chronological order of formation, (1) plagioclase–early pyroxene (±scapolite), (2) garnet–late pyroxene, (3) chlorite–epidote, and (4) chalcedony–calcite alteration. Geochemical, isotopic (Sr, Nd, O, S) and geochronological (Ar–Ar) data from alteration and magmatic rocks suggest a temporal and genetic link between the multiphase Şamlı pluton and the hydrothermal system that controls the Fe-oxide-Cu (±Au) mineralization. 40Ar/39Ar geochronology on hornblende and biotite separates of the Şamlı pluton yielded an age range between 23.20±0.50 and 22.42±0.11Ma, overlapping with 40Ar/39Ar age of 22.34±0.59Ma from alteration.The close spatial and temporal associations of Şamlı mineralization with porphyritic intrusions, pervasive Ca-rich alteration (calcic plagioclase, andraditic garnet, diopsidic pyroxene, scapolite, and epidote) are considered as common features akin to calcic assemblages in typical IOCG deposits. Besides abundant low-Ti (≤0.5%) magnetite/hematite, high Cu–moderate Au (up to 8.82ppm) association, structural control and lithologic controls of mineralization, low S-sulfide content (chalcopyrite>pyrite) in the deposit; and the derivation of causative magma from subduction-modified subcontinental lithospheric mantle under a transpressional to transtensional regime, are collectively considered as the features in favor of IOCG-type mineralization for the Şamlı deposit.