Fluid inclusion and Pb-O isotope constraints on the genesis of the Jurassic Karaburun VMS deposit (Central Pontides, Türkiye)
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Date
2026-03-13
Journal Title
Journal ISSN
Volume Title
Publisher
SAPIENZA
Abstract
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.
Description
Keywords
Central Pontides, Karaburun VMS, pelitic-mafic type, Pb-O isotope geochemistry, fluid inclusion