Polymetallic, sulphide ore deposits and associated volcanic rocks from, the harsit river area, N. E. Turkey

摘要: The Pontid magmatic arc developed during the late Cretaceous and early Tertiary as a result of northward subduction Tethyan ocean- floor beneath "Pontian Land", due to relative northwards movement Anatolia. Two volcanic cycles, both basalt-andesite-dacite-rhyodacite sequences, can be distinguished in northern Harsit river area. Basic members Upper Lower Volcanic Cycle include tholeiitic basalts andesitic lavas. They are overlain by dacite Only waning stage this cycle, rhyolites, tuffs breccias, contain abundant pyroclastics. This is closely related mineralisation constitutes host-rock horizon. its associated show spatial association with regional fault pattern. Tertiary, shows evidence explosive vulcanicity Series. Dacites rhyodacites locally again faulting. Both major trace element chemistries two cycles Udemonstrate clear separation into lower an upper calc-alkaline cycle. rocks similar chemistry volcanics from island arcs other areas. origin magma ascribed melting "dry" amphibolite formed metamorphism oceanic crust subduction. Fractional crystallisation has led development Cycle. thought have later process when was joined biotite or phlogopite. produced relatively "wet" which suppressed plagioclase fractionation until prevented enrichment iron residual melts. volatiles may promoted some Iherzolite overlying subducted slab. A "high-level" fractional yielded Massive, polymetallic final phase characterised sequence quartz-pyrite and/or sphalerite chalcopyrite stockwork ore massive containing galena, sphalerite, chalcopyrite, barite sulphosalts. is, turn, horizon dominant, succeeded hematitic manganiferous sediments. deposits, their mode occurrence, mineralogy morphology bear close resemblance Kuroko deposits found Miocene, tholeiitic, felsic Japan. lack for derivation fluids igneous activity era, unmineralised nature differentiates restrict mineralising episode short period felsic, volcanism. responsible ore-bodies metal-rich that separated solidification silicate magma. ascending solutions interacted with.-sea water. resulted exchange Co, Ni, Se, Mg, Ca, Na K, decrease temperature salinity, increase oxidation state pH initial composition fluids. Lithogeochemical analysis wall-rock alteration patterns hanging wall used conjunction detailed stratigraphical structural provide directional vectors determine proximity bodies.