Porphyry Cu mineralizations related with the small Tertiary volcanic intrusions in the Bučim ore deposit, Eastern Macedonia

Abstract

The paper presents data about geology, geochemistry, structure, genesis and specific features of the Bucim, porphyry Cu deposit with active mining in Macedonia. The porphyry mineralization (0.3 % Cu, 0.3-0.5 ppm Au) is spatially and temporarily associated with Tertiary subvolcanic intrusions of latitic and latitic-andesitic composition. The intrusions took place during Oligo-Miocene time (24 to 27 Ma), a period of intensive tectono-magmatic and ore-forming processes.. The latest results of this study to an array of major ore (hypogen) minerals such chalcopyrite, pyrite, magnetite, hematite, cubanite, valleriite, native Au and bornite and secondary enrichment zone minerals (within Cukar ore body) chalcocite, covellite, tenorite, native Cu, malachite, azurite etc added minerals such calaverite, krennerite, electrum, petzite and bismuth±selenium minerals (bismuthinite, galenobismutite, krupkaite, friedrichite, emplectite, cosalite, laitakarite and native bismuth). Variations of the δ34S values for the whole Bucim ore deposit ranged from +0.2 ‰ to +2.5 ‰ while δ13C‰ and δ18O‰ isotope values ranged from -10.8 to -3.8‰ and from +14.0 to +22.7 ‰, respectively. In regards to fluid inclusions it was confirmed that beside dominated gas-liquid, two-phase inclusions, there are also three-phase fluid inclusions (gas + liquid + solid phase). Also, recent Sr and Nd isotope ratios (87Sr/86Sr 0.70666-0.70741 and 143Nd/144Nd 0.512487–0.512489) indicated slight contamination of the magmatic products by continental crust material, due to a partial melting of the deep parts of continental crust underthrusted by collision of continental blocks. In direction were results from the REE data, manifested through high contents of large ion lithophile elements (LILE), high Ba/Nb ratio (116.72-190.72) and depletion in high field strength elements (HFSE) and Europium negative anomaly (0.68893-0.91251).