C–O Stable Isotope Geochemistry of Carbonate Minerals in the Nonsulfide Zinc Deposits of the Middle East: A Review

Abstract

Zinc nonsulfides are well represented in the Middle East, with occurrences in Turkey, Iran, and Yemen. Their genesis can be constrained by using carbon and oxygen isotope systematics applied to carbonate minerals. The δ 13 C ratios of smithsonite and hydrozincite in Iran and Turkey are comprised in the typical interval of supergene Zn carbonates (−0.4 and −7.1 V-PDB). The oxygen isotope geochemistry is more complex. Oxygen isotope compositions of smithsonite of the Hakkari deposit (Turkey) (δ 18 O from 24.2 to 25.6 V-SMOW) point to precipitation temperatures between~4 and~18 • C, corresponding to a normal weathering environment at these latitudes, whereas δ 18 O of smithsonite from other Middle East deposits (Angouran in Iran, Jabali in Yemen) point to the precipitation from low-to medium-temperature hydrothermal fluids. The C-O isotopic compositions of hydrozincite from the Mehdi Abad, Irankuh, and Chah-Talkh deposits can be only partially compared with those of smithsonite, because the oxygen isotopes fractionation equation for hydrozincite-water is not known. A comparison between the geochemical characteristics of all Zn-nonsulfide ores in the Middle East indicates that, even though several mineral deposits are derived from supergene weathering processes, other ones have been deposited from fluids associated with magmatic activity (Angouran, Iran) or with hydrothermal systems (Jabali, Yemen). This suggests that it is not possible to apply a common interpretative model to the genesis of all nonsulfide deposits in the Middle East.

Depositional Conditions of Cretaceous Ironstones Deposit in the Chulym-Yenisey Basin (Western Siberia)

“…The stable carbon and oxygen isotope ratios were obtained on seven carbonate-bearing rock samples of the studied area. Powdered samples were reacted with phosphoric acid at 70 • C using a Gasbench II connected to a Thermo Finnigan Five Plus mass spectrometer (Thermo Fisher Scientific, Waltham, MA, United States) [61]. Carbon and oxygen isotope values are reported per mil relative to V-PDB (NBS19 and LSVEC, respectively).…”