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TitleThe Barika gold-bearing Kuroko-type volcanogenic massive sulfide (VMS) deposit, Sanandaj-Sirjan zone, Iran
AuthorTajeddin, H A; Rastad, E; Yaghoubpour, A; Maghfouri, S; Peter, J MORCID logo; Goldfarb, R; Mohajjel, M
SourceOre Geology Reviews vol. 113, 103081, 2019 p. 1-23,
Alt SeriesNatural Resources Canada, Contribution Series 20190555
Mediapaper; on-line; digital
File formatpdf; html
AreaIran (Islamic Republic of)
Lat/Long WENS 36.1808 36.1989 45.6553 45.6375
Subjectseconomic geology; mineralogy; geochemistry; tectonics; Science and Technology; Nature and Environment; mineral deposits; volcanogenic deposits; sulphide deposits; gold; silver; base metals; lead; zinc; copper; antimony; mineralization; ore mineral genesis; host rocks; tectonic history; metamorphism; deformation; shearing; recrystallization; faulting; greenschist facies; hydrothermal systems; volcanism; veins; mineral assemblages; textures; fluid inclusions; salinity; thermal analyses; isotopic studies; oxygen isotopes; sulphur; Barika Deposit; Sanandaj-Sirjan Zone; Barika Shear Zone; Phanerozoic; Mesozoic; Cretaceous
Illustrationsgeoscientific sketch maps; tables; photographs; schematic sections; plots; ternary diagrams; photomicrographs; geochronological charts; histograms; bar graphs; schematic representations
ProgramTargeted Geoscience Initiative (TGI-5) Volcanogenic massive sulphide ore systems - base metal sources and processes
Released2019 08 21
AbstractThe Barika deposit is the first documented auriferous Kuroko-type volcanogenic massive sulfide (VMS) deposit in Iran. It is hosted in meta-andesites of the Sanandaj-Sirjan metamorphic Zone (SSZ). The mineralization and host rocks have been metamorphosed to lower greenschist facies. The deposit has Au and Ag grades in the stratiform lens averaging 3.5 and 175 g/t, respectively, and contains 2.3 tonnes of Au and 143 tonnes of Ag. The base metal (Pb + Zn + Cu) content of the deposit is low (<1?wt%). The stratiform part of the Barika deposit is approximately 150 m long and up to 20 m thick, and consists of massive to semi-massive sulfides, some of which are banded, which are overlain by barite and siliceous exhalites. The >200 m long and up to 500 m wide stringer zone immediately stratigraphically underlies the stratiform mineralization. Veins within the stringer zone are composed of quartz, pyrite, galena, sphalerite, tetrahedrite-tennantite, and rare chalcopyrite. Stratiform mineralization is composed of pyrite, sphalerite, galena, stibnite, tetrahedrite-tennantite, several Ag-(As-Sb-Pb) sulfosalt minerals (guettardite, ferdowsiite, barikaite, stephanite, pyrargyrite, trechmannite, miargyrite, As-rich andorite, As-rich geocronite, Sb-rich seligmanite and smithite), realgar, and electrum.
Based on mineral assemblages and textures, four mineralization stages are recognized. During stage 1, pyrite, sphalerite, galena, tetrahedrite-tennantite, and stibnite were deposited during synvolcanic hydrothermal activity. During stages 2 and 3, post-mineralization deformation and shearing contemporaneous with regional metamorphism modified most of the primary textures in the stratiform mineralization. Stage 2 mineralization represents Stage 1 mineralization that was remobilized during regional metamorphism, and this mineralization is characterized by gold as submicroscopic inclusions or as 'invisible' gold locked in pyrite, as well as electrum in the barite mineralization. Regional metamorphism and deformation (D1) caused recrystallization of primary mineralization (mainly pyrite) and migration of submicroscopic gold via solution-precipitation creep to the grain boundaries to form microscopic electrum. Stage 3 mineralization is attendant with D2 movement along the Barika shear zone that controlled the overall geometry of the deposit and resulted in the development of ductile-brittle deformation textures and the formation of several Ag(As-Sb-Pb)-rich sulfosalt minerals and electrum. Most of the electrum grains occur together with sulfosalt minerals that fill open spaces formed during shearing. Stage 4 mineralization is marked by the formation of white, barren quartz veins and high-angle normal faults that were developed during D3 extension-related uplift.
Primary two-phase fluid inclusions in quartz of the stringer zone and barite from the stratiform mineralization homogenize between 132° and 283°C (average ~ 200°C). Salinities of the primary fluid inclusions range from 1.4 to 9.6 wt% NaCl eq. The sulfur isotope compositions of sulfide minerals from stratiform and stockwork mineralization in the Barika deposit range from delta-34S -0.8 to +5.6 permille. This relatively narrow range suggests that the sulfur in the sulfide mineralization was derived from the leaching of igneous sulfur from the underlying andesitic rocks, similar to most Japanese Kuroko VMS deposits. Temperatures of formation for Barika sulfides estimated based on sulfur isotope values for coexisting galena-sphalerite (DELTA = 2-4.8 permille) and galena-pyrite (DELTA = -3.3 to -5.4 permille) pairs range from 146 to 293°C, and these are consistent with fluid inclusion homogenization temperatures. The primary mineralizing fluids have a calculated delta-18O value of between +4.3 and +6.3 permille, based on the delta-18O compositions of quartz from the stringer zone and assuming a temperature of 200°C and that isotopic equilibrium was attained.

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