Scapolite compositional change in a metamorphic gradient and its bearing on the identification of meta-evaporite sequences

Kwak, T. A. P.

doi:10.1017/s0016756800036657

Cited by 33 publications

(12 citation statements)

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“…The common occurrence of scapolite in the Northern Norrbotten Ore Province is suggested to reflect the occurrence of former evaporites within the stratigraphic record of the Kiruna Greenstones , in agreement with other studies suggesting that scapolite-rich metasedimentary units are commonly reflecting former evaporite-bearing strata (Ramsay and Davidson, 1970;Kwak, 1977;Ortega-Gutierrez, 1984). Strong, regional scapolite alteration, with no obvious relation to ores, is developed at two stratigraphic levels within the Kiruna Greenstones (Martinsson, 1997;2004a,b).…”

Section: Figure 19supporting

confidence: 86%

Metallogeny of the Northern Norrbotten Ore Province, northern Fennoscandian Shield with emphasis on IOCG and apatite-iron ore deposits

Martinsson

Billström

Broman

et al. 2016

Ore Geology Reviews

105

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The Northern Norrbotten Ore Province in northernmost Sweden includes the type localities for Kirunatype apatite iron deposits and has been the focus for intense exploration and research related to Fe oxide-Cu-Au mineralisation during the last decades. Several different types of Fe-oxide and Cu-Au±Fe oxide mineralisation occur in the region and include: stratiform Cu±Zn±Pb±Fe oxide type, iron formations (including BIF´s), Kirunatype apatite iron ore, and epigenetic Cu±Au±Fe oxide type which may be further subdivided into different styles of mineralisation, some of them with typical IOCG (Iron Oxide-Copper-Gold) characteristics. Generally, the formation of Fe oxide±Cu±Au mineralisation is directly or indirectly dated between ~2.1 and 1.75 Ga, thus spanning about 350 m.y. of geological evolution.The current paper will present in more detail the characteristics of certain key deposits, and aims to put the global concepts of Fe-oxide Cu-Au mineralisations into a regional context. The focus will be on iron deposits and various types of deposits containing Fe-oxides and Cu-sulphides in different proportions which generally have some characteristics in common with the IOCG style. In particular, ore fluid characteristics (magmatic versus non-magmatic) and new geochronological data are used to link the ore-forming processes with the overall crustal evolution to generate a metallogenetic model. Rift bounded shallow marine basins developed at ~2.1-2.0 Ga following a long period of extensional tectonics within the Greenstone-dominated, 2.5-2.0 Ga Karelian craton. The ~1.9-1.8 Ga Svecofennian Orogen is characterised by subduction and accretion from the southwest. An initial emplacement of calc-alkaline magmas into ~1.9 Ga continental arcs led to the formation of the Haparanda Suite and the Porphyrite Group volcanic rocks. Following this early stage of magmatic activity, and separated from it by the earliest deformation and metamorphism, more alkali-rich magmas of the Perthite Monzonite Suite and the Kiirunavaara Group volcanic rocks were formed at ~1.88 Ga. Subsequently, partial melting of the middle crust produced large volumes of ~1.85 and 1.8 Ga S-type granites in conjunction with subduction related A-/I-type magmatism and associated deformation and metamorphism. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTIn our metallogenetic model the ore formation is considered to relate to the geological evolution as follows. Iron formations and a few stratiform sulphide deposits were deposited in relation to exhalative processes in rift bounded marine basins. The iron formations may be sub-divided into BIF-(banded iron formations) andMg-rich types, and at several locations these types grade into each other. There is no direct age evidence to constrain the deposition of iron formations, but stable isotope data and stratigraphic correlations suggest a formation within the 2.1-2.0 Ga age range. The major Kiruna-type ores formed from an iron-rich magma (generally with a hydrothermal over-print) and are restricted to areas occup...

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Section: Figure 19supporting

confidence: 86%

Metallogeny of the Northern Norrbotten Ore Province, northern Fennoscandian Shield with emphasis on IOCG and apatite-iron ore deposits

Martinsson

Billström

Broman

et al. 2016

Ore Geology Reviews

105

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“…These include metamorphism of evaporite-bearing sedimentary rock units (e.g., Rich, 1979;Mora and Valley, 1989;Oliver et al, 1992;Giuliani et al, 1995). Indeed, the presence of subordinate scapolite in marble interlayered with metapelite in the western metamorphic complex of the Muteh area is likely evidence of metaevaporites (Kwak, 1977;Moine et al, 1981;Faryad, 2002). A further possible source of saline fluids coexisting with CO 2 -rich fluids are magmatic intrusions (e.g., Nabelek and Ternes, 1997;Baker, 2002) emplaced at various stages during the evolution of the Sanandaj-Sirjan zone.…”

Section: Discussion Of the Fluid Inclusion Datamentioning

confidence: 99%

Eocene Gold Ore Formation at Muteh, Sanandaj-Sirjan Tectonic Zone, Western Iran: A Result of Late-Stage Extension and Exhumation of Metamorphic Basement Rocks within the Zagros Orogen

Moritz¹,

Ghazban²,

Singer³

2006

Economic Geology

124

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A multidisciplinary study including field geology, microstructure analysis, 40Ar/39Ar dating, and fluid inclusion microthermometry and Raman spectrometry has been carried out on the Muteh gold deposit located in a greenschist to amphibolite facies metamorphic rock complex of the Sanandaj-Sirjan tectonic zone, Zagros orogen, Iran. The Muteh gold deposit has been previously interpreted as genetically related to Precambrian granitic intrusions, as an exhalative hot-spring deposit related to Paleozoic rhyolitic-acidic tuffs, and to local metamorphic processes. Host rocks of the gold deposit are predominantly schist and gneiss, and subsidiary amphibolite and quartzite, and are intruded by leucogranites. In the vicinity of the gold deposit, the metamorphic and granitic rocks display a subhorizontal mylonitic foliation, containing a northeast-oriented stretching lineation. Field investigations in one of the producing open pits show that the gold orebodies are controlled by northwest-oriented normal faults and joints, dipping to the northeast and the southwest, and crosscutting the ductile fabric of the host rocks. Both the ductile fabric of the host rocks and the gold ore-controlling brittle structures are interpreted to have formed within a single, continuous extensional event, which started with ductile deformation and gradually changed into brittle deformation. Hydrothermal alteration associated with ore formation consists of quartz, muscovite, pyrite, dolomite-ankerite, and albite, which crosscuts the ductile fabric and overprints the metamorphic minerals of the host rocks. Pyrite is the dominant opaque mineral and is the major phase associated with gold. Chalcopyrite, marcasite, bismuth, galena, sphalerite, and pyrrhotite are subsidiary to rare phases. 40Ar/39Ar incremental-heating and in situ laser-ablation age data reveal a coherent sequence of cooling and hydrothermal events in the metamorphic complex hosting the Muteh gold deposit. Muscovite samples from the alteration zone and from one quartz vein from the orebodies yield 40Ar/39Ar ages between 55.7 and 38.5 Ma and show that gold mineralization is the youngest among the different dated events. This Eocene age is consistent with the young structural setting of the gold orebodies revealing an emplacement along northwestoriented normal faults, which can be correlated with Tertiary extensional tectonic events reported by previous field investigations. The data also indicate that gold ore formation is coeval with magmatism in the adjacent Tertiary Urumieh-Dokhtar magmatic belt and with intrusive activity within the Sanandaj-Sirjan zone, with a 40Ar/39Ar age of 54 Ma near Muteh according to our study. The remaining 40Ar/39Ar data reveal a Cretaceous to early Tertiary metamorphic, magmatic, and deformation history of the complex hosting the Muteh gold deposit. The fluid inclusion study showed that distinct fluids were present during the regional geologic evolution predating ore formation and later Eocene gold ore formation. Early regional fluids consist of an H2O-CO2...

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“…Therefore, a Cl-rich fluid is likely to have mobilised Zn, because the fluidrock fractionation factor is maximised by chlorocomplexes over other complexing ligands by virtue of their longer (and therefore weaker) bonds. The presence of saline fluids during metamorphism is also supported by Kwak (1977) and Hammerli et al (2013) who found evidence for circulation of a saline fluid with a major bittern brine component during metamorphism in the Kanmantoo Group. By contrast, we expect sulphur bearing species in the fluid had a trivial role in Zn or Pb transport, as S contents of all samples irrespective of metamorphic grades are consistently low (<50 μg g −1 ).…”

Section: Discussionmentioning

confidence: 66%

Zn and Pb mobility during metamorphism of sedimentary rocks and potential implications for some base metal deposits

et al. 2015

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Comprehension of the genesis of Pb-Zn ore systems is currently limited by a poor understanding of where these metals are sourced from. Our study of metal mobility during regional metamorphism in the Mt. Lofty Ranges, South Australia, demonstrates that in staurolite-absent siliciclastic metasedimentary rocks, biotite contains >80 % of the bulk rock Zn, as well as a considerable proportion of the total Pb. Fluid flow through these metasedimentary rocks led to a continuous depletion of Pb and Zn on a mineral and bulk rock scale during prograde regional metamorphism. We calculate that ∼80 % of the bulk rock Zn and ∼50 % of the bulk rock Pb were mobilised, mainly through reactions involving biotite. These reactions led to a calculated Pb and Zn Bloss^of ∼2.7 and 27 Mt, respectively, in the high-grade metamorphic zone. Halogen contents of apatite and biotite and bulk rock Zn isotope data provide evidence that Cl-rich metamorphic fluids were important for metal transport. Hence, fluid flow accompanying prograde metamorphism of typical sedimentary rocks can mobilise base metals to the degree required to potentially supply significant Pb-Zn ore systems.

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Scapolite compositional change in a metamorphic gradient and its bearing on the identification of meta-evaporite sequences

Cited by 33 publications

References 12 publications

Metallogeny of the Northern Norrbotten Ore Province, northern Fennoscandian Shield with emphasis on IOCG and apatite-iron ore deposits

Metallogeny of the Northern Norrbotten Ore Province, northern Fennoscandian Shield with emphasis on IOCG and apatite-iron ore deposits

Eocene Gold Ore Formation at Muteh, Sanandaj-Sirjan Tectonic Zone, Western Iran: A Result of Late-Stage Extension and Exhumation of Metamorphic Basement Rocks within the Zagros Orogen

Zn and Pb mobility during metamorphism of sedimentary rocks and potential implications for some base metal deposits

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