A prospective sector in the Tethyan Metallogenic Belt: Geology and geochronology of mineral deposits in the Biga Peninsula, NW Turkey

Abstract

The Tethyan Metallogenic Belt (TMB), extending from Europe through Anatolia to Iran, is one of the world's major metal producing belts, and consists of many sectors. Mineral deposits of the Biga Peninsula in northwestern Turkey exhibit, in many ways, the characteristics of mineral deposits found throughout the belt. Biga Peninsula tectonically forms the westernmost part of the Sakarya Zone and easternmost part of the Rhodope Zone at the intersection of Gondwana and Laurasia.The Biga Peninsula metallogeny research and exploration project created a GIS inventory of mineral deposits and prospects, and classified them genetically to evaluate the mineral deposit potential using genetic models based on descriptive data. The GIS database, consisting of 128 deposits or prospects, helped to generate new prospects and potential prospects. This field-based study indicated that the Biga Peninsula forms a prime target for gold–copper exploration not only in Turkey but in the world.The current economically significant mineral deposits of the Biga Peninsula were shaped by Cenozoic calc-alkaline magmatism, ranging between 52 and 18Ma, and related to mainly collisional and post-collisional tectonic regime. Epithermal Au–Ag deposits including high-(HS), low-(LS) and intermediate-sulfidation (IS) styles, porphyry Au–Cu–Mo and base-metal skarn systems are economically the most important. Though there are no currently economic examples of some of them in the Biga Peninsula, other deposit types include Carlin-like distal disseminated Au–Ag, orogenic Au, especially listwanite hosted, volcanogenic Mn and U, lateritic (ferricrete) Fe deposits, carbonate replacement (CR) and placers.Several active metal mines, such as Balya, Arapucandere and Koru, are operating in the Biga Peninsula. Kucukdere Au–Ag deposit in Balikesir is the only gold mine in the Biga Peninsula, except for by-product gold produced from base-metal deposits. Results of the study show current total gold endowment of the Biga Peninsula including reserves and/or resources is 9.18Moz gold [284.2t] contained in twelve different deposits. Of these only 6 contain significant gold [>0.3Moz or 10t]. Halilaga porphyry and Agi Dagi and Kirazli HS epithermal systems have an ongoing resource estimate, and Halilaga is a candidate to be one of the largest Cu–Au deposits not only in the Biga Peninsula, but in Turkey. Currently newly discovered Tepeoba is the largest porphyry Cu–Mo–Au deposit with known resources in the Biga Peninsula.Here, the first40Ar/39Ar step-heating age data conducted on some of the major HS epithermal gold deposits and causative intrusives in the Biga Peninsula are reported. Geochronological results from this project, evaluated with previous studies, indicate at least 3 phases of porphyry and 2 phases of high-sulfidation epithermal gold mineralization in the Biga Peninsula. The most important mineralizing phases and related host rocks for gold mineralization range from 38 to 22Ma. The Oligocene is especially important for economic epithermal and porphyry systems in the Biga Peninsula, which is comparable to deposits in the Oligo-Miocene Serbomacedonian-Rhodope metallogenic belt of the Balkan Peninsula in SE Europe.