Geochemistry, microthermometry, and C and O isotope constraints on the origin of the Duzkoy Fe-Cu skarn deposit (Gumuhane, NE Turkey)


Demir Y. , Bayraktar K.

ARABIAN JOURNAL OF GEOSCIENCES, cilt.13, sa.23, 2020 (SCI İndekslerine Giren Dergi) identifier identifier

  • Yayın Türü: Makale / Tam Makale
  • Cilt numarası: 13 Konu: 23
  • Basım Tarihi: 2020
  • Doi Numarası: 10.1007/s12517-020-06272-z
  • Dergi Adı: ARABIAN JOURNAL OF GEOSCIENCES

Özet

The Fe-Cu-type Duzkoy skarn deposit occurs along the contact between the Lower Cretaceous Berdiga limestone and the Eocene-aged Harit granitoid. The endoskarn zone is characterized by the presence of granular pyroxenes, while garnet, epidote, quartz, and calcite are commonly defined in the exoskarn. Fe-Cu-type skarns were identified according to the mineralogical properties, garnet (Ad(0-8.81)Gr(59.69-78.65)Py(21.35-38.11)) and pyroxene (Hd(0.29-38.64)Di(61.09-99.02)Jo(0.06-1.26)) compositions, and Mn/Fe ratios (in the range of < 0.1 to 3.75) of pyroxenes. The geochemistry of the Harit granitoid is also compatible with Fe-Cu-type skarns according to the high MgO (2.41 wt%) and low K2O (2.05 wt%), as well as Rb-Sc and Rb/Sr-Zr contents. Therefore, the coexistence of both oxide and sulfide phases was found to be closely associated with the geochemical features of the Harit granitoid. Higher homogenization temperatures (Th, up to 483 C) and salinity (up to 44.4 wt% NaCl equ.) of the early-stage fluids correspond to magmatic-dominated fluids. In contrast, the decreasing Th and salinity as low as 168 degrees C and 1.1 wt% NaCl equ., respectively, refer to a mixture of meteoric water through the later stages. The delta C-13 isotopes of skarn calcites (between - 1.62 and 2.77 parts per thousand) are compatible with marine carbonates, while their delta O-18 rates, ranging from 9.04 and 24.5 parts per thousand, are highly depleted. Further depletion of delta O-18 isotopes (down to 3.47 parts per thousand), calculated from the equilibrated fluids with calcites, while delta C-13 isotopes were stable, is indicative of the mixing of magmatic and meteoric waters, and these results comply well with the fluid inclusion data.