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Angouran |
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Iran |
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Zn Pb Ag
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Super Porphyry Cu and Au
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The Angouran Zn-(Pb-Ag) deposit is located in Zanjan Province, NW Iran and falls within the central Sanandaj-Sirjan Zone of the Zagros orogenic belt (#Location: 36° 37' 29"N, 47° 24' 19"E).
The deposit is hosted by a metamorphic core complex that is unconformably overlain by a Neogene volcanic and evaporite-bearing marine to continental sedimentary sequence.
The ore body exhibits a vertical zonation typical of supergene overprinting, with i). an underlying Zn-rich, hypogene, sulphide, and mixed sulphide-carbonate ore, and ii). supergene ore towards the top. The deposit formed at a lithological boundary which comprises a thrust contact between footwall schists and hangingwall marble. The host marble has been thrust onto a thick pile of Burdigalian ignimbrites cut by10 Ma basaltic dykes. A 10 km long carbonate travertine tongue overlies the Cenozoic volcanic rocks and contains dispersed metal anomalies including Zn. The field relationships and geology suggest that the hypogene mineralization is younger than 10 Ma, and point to a genetic link between the formation of the Zn carbonate ores, travertine deposition and the geothermal activity that continues in the district to the present.
The hypogene deposit, which has been oxidised to form a significant non-sulphide orebody, mainly in the form of the Zn carbonate smithsonite, is located at the crest of an open anticline at the contact between Neoproterozoic to Cambrian footwall micaschists and hanging wall marbles.
The fine-grained primary sulphide ore is massive, replacive, often brecciated, post-metamorphic and dominated by Fe-poor sphalerite, with minor galena, pyrite, anhydrite, quartz, muscovite, dolomite, and rare calcite.
Mineralisation is interpretted to have taken place during two successive stages, with the zinc being derived from a pre-existing sulphide accumulation. A first, main stage of Zn carbonates (stage I carbonate ore) is associated with both preexisting and subordinate newly formed sulphides, whereas the second stage is characterised by supergene carbonates (Zn and minor Pb) coexisting with oxides and hydroxides (stage II carbonate ore). Smithsonite coprecipited with galena, pyrite and arsenopyrite, in the absence of Fe- and Mn-oxides/hydroxides and of any discernible oxidation or dissolution of the sphalerite-rich primary sulphide ore.
Hypogene formation of stage I carbonate ore at Angouran from low-temperature hydrothermal fluids (Isotope analysis of sphalerite suggests homogenisation temperatures of 180 to 70°C) is suggested, probably mobilised during the waning stages of Tertiary-Quaternary volcanic activity in an environment characterised by abundant travertine systems throughout the whole region. Isotope analysis also suggest that that the sulphide ore formed by the interaction of modified, strongly evaporated Miocene seawater and the lithotypes of an exhumed metamorphic core complex.
Conversely, stage II carbonate ore is unambiguously related to supergene weathering, as evidenced by the absence of sulphides, and the presence of Fe-Mn-oxides and arsenates.
Ar-Ar determinations on muscovite from mineralised and unaltered footwall mica schists suggest a rapid Mid-Miocene exhumation of the metamorphic basement at approximately 20 Ma providing an upper age constraint on the oxide mineralisation.
Proved and estimated resources amount to:
sulphide ore - 4 Mt @ 39% Zn, 3% Pb, 110 g/t Ag, and
oxide carbonate ores - 17.3 Mt @ 28.1% Zn, 4.4% Pb (Daliran, 2009).
The most recent source geological information used to prepare this decription was dated: 2005.
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Angouran
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Selected References:
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Boni M, Gilg H A, Balassone G, Schneider J, Allen C and Moore F, 2007 - Hypogene Zn carbonate ores in the Angouran deposit, NW Iran : in Mineralium Deposita v42 pp 799-820
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Daliran F, Pride K, Walther J, Berner Z A and Bakker R J, 2013 - The Angouran Zn (Pb) deposit, NW Iran: Evidence for a two stage, hypogene zinc sulfide–zinc carbonate mineralization: in Ore Geology Reviews v.53 pp. 373-402
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Gilg H A, Boni M, Balassone G, Allen C A, Banks D and Moore F, 2005 - Marble-hosted sulfide ores in the Angouran Zn-(Pb–Ag) deposit, NW Iran: interaction of sedimentary brines with a metamorphic core complex: in Mineralium Deposita v41 pp 1432-1866
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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