F Mousivand; E Rastad; M.H Emami; J Peter; M Solomon
Abstract
The Bavanat (Jian) pelitic-mafic- / Besshi-type Cu-Zn-Ag volcanogenic massive sulfide deposit locates in the Bavanat area, South Sanandaj-Sirjan zone. Mineralization occurs as two stratigraphic ore horizons discontinuously within the Surian metamorphosed volcano-sedimentary complex through more than ...
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The Bavanat (Jian) pelitic-mafic- / Besshi-type Cu-Zn-Ag volcanogenic massive sulfide deposit locates in the Bavanat area, South Sanandaj-Sirjan zone. Mineralization occurs as two stratigraphic ore horizons discontinuously within the Surian metamorphosed volcano-sedimentary complex through more than 35 km in the area. Stratigraphicaly, from footwall toward hangingwall, four ore facieses were distinguished within the Bavanat (Jian) orebodies including: 1) vein-veinlets or stringer, 2) vent complex, 3) bedded-banded, and 4) hydrothermal-exhalative sediments. The ores have various primary and secondary textures and structures, although most of the primary ones were obscured during metamorphism and deformation. The relict primary textures include massive, semi-massive, banded, brecciated, disseminated and vein-veinlet ores. In the stringer and specially in the vent complex facies, chalcopyrite replaced pyrite indicating influx of a hot copper-rich fluid into the pyrite-rich massive ores during zone refining process. Also, a metal and mineralogical zonation is obsereved in the Bavanat deposit. The major wall rock alterations in the Bavanat deposit from center to margins are silicic, quartz-chlorite, chloritic, chlorite-carbonate and chlorite-sericite, which show zonal pattern. Based on electron microprobe studies, chlorite is of iron-rich type. The abundant pyrrhotite in the Bavanat deposit might be due to low oxygen and sulfur fogacity, and occurrence of abundant chlinochlor in the alteration zones may indicate low pH (between 4.3 and 5.3) conditions for the ore-forming fluids. The high amounts of Cu and Zn, and low amounts of Pb, along with fluid inclusion studies results indicate high temprature (300-350 °C) for the ore fluids. Based on this study, the ore fluids responsibe for formation of the Bavanat deposit were hot, reduced and acidic, which entered into a confined marine basins, followed by ore deposition.
F Mousivand; E Rastad; M.H Emami; J.M Peter
Abstract
Various types of volcanogenic massive sulfide (VMS) deposits occurred within the northern and southern parts of the Sanandaj-Sirjan zone (SSZ). The most important VMS deposits of the south SSZ includes the Bavanat Cu-Zn-Ag (pelitic mafic- or Besshi-type), Sargaz Cu-Zn (bimodal mafic- or Noranda-type), ...
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Various types of volcanogenic massive sulfide (VMS) deposits occurred within the northern and southern parts of the Sanandaj-Sirjan zone (SSZ). The most important VMS deposits of the south SSZ includes the Bavanat Cu-Zn-Ag (pelitic mafic- or Besshi-type), Sargaz Cu-Zn (bimodal mafic- or Noranda-type), and Chahgaz Zn-Pb-Cu (silicicalstic felsic-or Bathurst-type) deposits, and the north SSZ hosts the Barika gold-rich (bimodal felsic- or Kuroko-type) VMS deposit. Comparison of the VMS deposits, and investigating of possible relationship between formation of these deposits and tectono-magmatic processes within the SSZ indicate formation of all the deposits within intra-arc rift basins related to subduction of the Neo-Tethyan oceanic crust beneath the Iranian plate during Mesozoic period. Main reasons for formation of the different VMS types within the SSZ might be due to evolution of magma nature and intra-arc rift basins. Comparison between the deposits in many aspects including host and associated rock types and ore mineral paragenesis indicate clear differences between the Bavanat and Sargaz deposits and the Chahgaz deposit. It is inferred that the differences could be due to variations in magma compositions, i.e., felsic in the Chahgaz, and mafic in the Bavanat and Sargaz host sequences. Indeed, development of the intra-arc rifting was at early/nascent stage in the Bavanat and Sargaz regions and at mature stage in the Chahgaz area.The SSZ (particularly the southern part) due to hosting various VMS type deposits and involving the known largest and majority VMS deposits in Iran is the most attractive structural zone for VMS exploration.
F. Mousivand; E. Rastad; M. H. Emami; J. M. Peter; M. Solomon
Abstract
Zn-Pb-Cu mineralization in the Chahgaz area, located 60 km south of Shahre Babak, occurs within a Middle Jurassic metamorphosed bimodal volcano-sedimentary sequence in the South Sanandaj-Sirjan zone. Mineralization occurs associated with exhalites within units 1and 2 of the host sequence as numerous ...
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Zn-Pb-Cu mineralization in the Chahgaz area, located 60 km south of Shahre Babak, occurs within a Middle Jurassic metamorphosed bimodal volcano-sedimentary sequence in the South Sanandaj-Sirjan zone. Mineralization occurs associated with exhalites within units 1and 2 of the host sequence as numerous occurrences, and within unit 3 as Chahgaz deposit and some occurrences hosted by meta-rhyolitic tuff, meta-rhyolite, and meta-pelites, as predominantly stratiform, tabular and sheeted-like orebodies at specific stratigraphic horizons. Ore textures include massive, semi-massive, banded, laminated, disseminated and vein-veinlets. Ore minerals are predominantly pyrite, sphalerite, galena, chalcopyrite, tetrahedrite, arsenopyrite, and minor bornite and pyrrhotite, and gangue minerals include dominantly sericite, quartz, chlorite and barite. Wallrock alteration is dominated by sericitic and chloritic and minor carbonatic and silicic types. Altered host rocks have been foliated due to metamorphism and deformation, and along with the associated ores have been folded and faulted and show cataclastic, triple junctions, pressure shadows, crenulations, and boudinage features. Based on geological, mineralogical, geochemical and alteration studies, it is inferred that Zn-Pb-Cu mineralization in the Chahgaz area has occurred as volcanogenic massive sulfide (VMS)-type in an arc rift basin, and has subsequently been metamorphosed under greenschist facies conditions during the Late Cimmerian and Laramid orogenies and younger events. This mineralization, in comparison with similar deposits in the world, has the most similarities with those deposits of siliciclastic felsic-type in the Bathurst Mining Camp, Canada, and Iberian Pyrite Belt in Spain and Portugal; and it is the first recognition of this type in Iran.