Makale 2020-2029 yılları

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Browsing Makale 2020-2029 yılları by All Authors "Abdelnasser, Amr"

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    Fluid inclusion and Pb-O isotope constraints on the genesis of the Jurassic Karaburun VMS deposit (Central Pontides, Türkiye)
    (SAPIENZA, 2026-03-13) Çavdar, Buğra; Günay, Kurtuluş; Mutlu, Hali̇m; Çantay, Eren; Ekebaş-Çavdar, Eli̇f; Çi̇ftçi̇,Emi̇n; Abdelnasser, Amr
    The Jurassic Karaburun deposit of the Central Pontides represents one of the largest known volcanogenic massive sulphide (VMS) systems in Türkiye, comprising ~125 Mt of ore with average grade 1.16 wt% Cu, 0.25 wt% Zn, and 0.05 wt% Co. Mineralization is hosted by low-grade greenschist-facies rocks of the Çangaldağ Metamorphic Complex (CMC), where volcaniclastic and detrital successions interlayered with deep-marine sediments are intruded by mafic dikes and sills. Ore occurs mainly as stratiform, sheet-like to tabular bodies, expressed by disseminated, banded, pyritic clastic, semi-massive, and massive sulphide textures. To constrain ore-fluid evolution and metal provenance, we investigate primary fluid inclusions in ore-stage quartz and combined microthermometry with quartz δ18O and massive-sulphide Pb isotopes. Two-phase inclusions yield eutectic temperatures of −26 to −11 °C and lack clathrate formation, indicating a dominant H2O-NaCl system. Homogenization temperatures of 178-301 °C, corrected for ~160 bar hydrostatic pressure, imply trapping at 223±25 °C; ice-melting temperatures correspond to 1.4-11.1 wt% NaCl equiv. (mean 6.5 wt%). Moderately elevated salinity and the absence of boiling features support seawater-derived fluids modified by subseafloor circulation, with limited magmatic input. Quartz δ18O values (11.79 ‰ to 14.40 ‰ VSMOW) require isotopically evolved fluids, giving δ18O(fluid) of ~3-6‰ at FI-constrained temperatures. Pb isotope ratios (208Pb/204Pb=37.463-37.751; 207Pb/204Pb=15.424-15.503; 206Pb/204Pb=18.079-18.431) are weakly radiogenic and narrowly variable, consistent with a predominately mantle-derived Pb source. Collectively, these constraints indicate formation in a Jurassic ensimatic arcback- arc basin undergoing rifting, with chiefly seawater hydrothermal fluids modestly overprinted by magmatic volatiles.