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

摘要

The Samh (Bahkesir) Fe-oxide Cu (±Au) deposit, one of several iron (+Cu ± Au) deposits in western Turkey, is hosted by porphyritic rocks of the multi-phase Samh 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 Samh 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, 0, S) and geochronological (Ar-Ar) data from alteration and magmatic rocks suggest a temporal and genetic link between the multiphase Samh pluton and the hydrothermal system that controls the Fe-oxide-Cu (±Au) mineralization. ~(40)Ar/~(39)Ar geochronology on hornblende and biotite separates of the Samh pluton yielded an age range between 23.20 ± 0.50 and 22.42 ± 0.11 Ma, overlapping with ~(40)Ar/~(39)Ar age of 22.34 ± 0.59 Ma from alteration. The close spatial and temporal associations of Samh 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 8.82 ppm) 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 Samh deposit