The key role of mica during igneous concentration of tantalum

Stepanov, Aleksandr S.; Mavrogenes, John; Meffre, Sébastien; Davidson, Paul

doi:10.1007/s00410-014-1009-3

Cited by 259 publications

(100 citation statements)

References 52 publications

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“…7). The first stage occurred close to the peak metamorphism (5 GPa, 1000°C) [47,48,54,74] and involved diamond formation at moderately oxidized conditions in a system with coexisting hydrous melt and solute-rich CO 2 -bearing fluid. As pressure and temperature decreased subsequently, the fluid contained lesser amounts of solutes and became a CO 2 -bearing aqueous fluid.…”

Section: Discussionmentioning

confidence: 99%

“…The Kumdy-Kol block predominantly consists of schist and gneiss with minor boudins of eclogite and amphibolite, as well as lenses and interlayers of garnet-pyroxene and calc-silicate rocks, and migmatites. [8,47,53,54] Sample 117-3 is foliated gneiss ( Mn and Fe decreasing rimward. The narrow rim is likewise zoned: Ca and Mg decrease while Mn and Fe increase toward the grain margin.…”

Section: Geological Setting and Sample Descriptionmentioning

confidence: 99%

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CO₂‐bearing fluid inclusions associated with diamonds in zircon from the UHP Kokchetav gneisses

Mikhno

Musiyachenko

Shchepetova

et al. 2017

J Raman Spectroscopy

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CO2‐bearing fluid inclusions coexisting with diamonds were identified in zircons from diamondiferous gneiss in the Kokchetav Massif. This discovery provides evidence for the presence of CO2 in UHP fluids and diamond formation in moderately oxidized conditions in the Kokchetav gneiss. Fluid and multiphase solid inclusions coexisting in zircons represent immiscible melt and fluid captured close to the peak metamorphic conditions for the Kokchetav UHP gneiss. Most of CO2‐bearing inclusions are CO2+H2O mixtures except for some cases when they also contain daughter phases (e.g. muscovite, calcite and quartz) tracing the presence of aqueous and solute‐rich fluids at different phases of UHP metamorphism. Decrease of pressure and temperature may have been responsible for the reduction of solutes in the CO2‐bearing fluid. The lack of CO2‐bearing inclusions in garnet porphyroblasts from diamond‐bearing gneiss, as well as the common coexistence of aqueous CO2‐bearing inclusions with calcite, testify that most likely all CO2 in fluid was consumed by the calcite‐forming reaction and hydrous melt was the only remaining growth medium during retrograde metamorphism of the Kokchetav UHPM gneisses. Neither K‐cymrite nor kokchetavite was identified among daughter phases in the hydrous melt inclusions in garnet, which indicates that they hardly could originate in a metapelitic system. Copyright © 2017 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 99%

Section: Geological Setting and Sample Descriptionmentioning

confidence: 99%

CO₂‐bearing fluid inclusions associated with diamonds in zircon from the UHP Kokchetav gneisses

Mikhno

Musiyachenko

Shchepetova

et al. 2017

J Raman Spectroscopy

View full text Add to dashboard Cite

show abstract

“…The high Cs and Sn contents rather reflect an enrichment in samples that interacted with fluids where Sn and Cs were strongly concentrated (e.g., Förster et al, 1999 Shaw (1968). (5) The ratios between twin elements, such as Nb/Ta, may be fractionated during magmato-hydrothermal processes either by muscovite and biotite fractionation (Stepanov et al, 2014) or by fluid-rock interaction (Dostal and Chatterjee, 2000). Here, the Nb/Ta ratios decrease below a value of 5 toward the apical zone (Fig.…”

Section: Hydrothermal Historymentioning

confidence: 94%

Tectonic record, magmatic history and hydrothermal alteration in the Hercynian Guérande leucogranite, Armorican Massif, France

Ballouard

Boulvais

Poujol

et al. 2015

Lithos

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“…Many experimental studies have shown that peraluminous granites are typically formed by melting of biotite + muscovitebearing metapelites (Harris and Massey, 1994;Gardien et al, 1995;Patiño Douce and Harris, 1998). Biotite in the metapelites represents a host for elements such as Li, Rb, Cs, Nb and Ta (Bea et al, 1994;Stepanov et al, 2014). They are also a potentially important source of H 2 O, F and Cl.…”

Section: Sources Of Pegmatitesmentioning

confidence: 99%

Petrogenesis of rare-metal pegmatites in high-grade metamorphic terranes: a case study from the Lewisian Gneiss Complex of north-west Scotland

Shaw

Goodenough

Horstwood³

et al. 2016

Applied Earth Science

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a b s t r a c tMany rare metals used today are derived from granitic pegmatites, but debate continues about the origin of these rocks. It is clear that some pegmatites represent the most highly fractionated products of a parental granite body, whilst others have formed by anatexis of local crust. However, the importance of these two processes in the formation of rare-metal pegmatites is not always evident.The Lewisian Gneiss Complex of NW Scotland comprises Archaean meta-igneous gneisses which were highly reworked during accretional and collisional events in the Palaeoproterozoic (Laxfordian orogeny). Crustal thickening and subsequent decompression led to melting and the formation of abundant granitic and pegmatitic sheets in many parts of the Lewisian Gneiss Complex. This paper presents new petrological, geochemical and age data for those pegmatites and shows that, whilst the majority are barren biotite-magnetite granitic pegmatites, a few muscovite-garnet (rare-metal) pegmatites are present. These are mainly intruded into a belt of Palaeoproterozoic metasedimentary and meta-igneous rocks known as the Harris Granulite Belt.The rare-metal pegmatites are distinct in their mineralogy, containing garnet and muscovite, with local tourmaline and a range of accessory minerals including columbite and tantalite. In contrast, the biotitemagnetite pegmatites have biotite and magnetite as their main mafic components. The rare-metal pegmatites are also distinguished by their bulk-rock and mineral chemistry, including a more peraluminous character and enrichments in Rb, Li, Cs, Be, Nb and Ta. New U-Pb ages (c. 1690-1710 Ma) suggest that these rare-metal pegmatites are within the age range of nearby biotite-magnetite pegmatites, indicating that similar genetic processes could have been responsible for their formation.The peraluminous nature of the rare-metal pegmatites strongly points towards a metasedimentary source. Notably, within the Lewisian Gneiss Complex, such pegmatites are only found in areas where a metasedimentary source is available. The evidence thus points towards all the Laxfordian pegmatites being formed by a process of crustal anatexis, with the formation of rare-metal pegmatites being largely controlled by source composition rather than solely by genetic process. This is in keeping with previous studies that have also challenged the widely accepted model that all rare-metal pegmatites are formed by fractionation from a parental granite, and raises questions about the origin of other mineralised pegmatites worldwide.

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The key role of mica during igneous concentration of tantalum

Cited by 259 publications

References 52 publications

CO₂‐bearing fluid inclusions associated with diamonds in zircon from the UHP Kokchetav gneisses

CO₂‐bearing fluid inclusions associated with diamonds in zircon from the UHP Kokchetav gneisses

Tectonic record, magmatic history and hydrothermal alteration in the Hercynian Guérande leucogranite, Armorican Massif, France

Petrogenesis of rare-metal pegmatites in high-grade metamorphic terranes: a case study from the Lewisian Gneiss Complex of north-west Scotland

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The key role of mica during igneous concentration of tantalum

Cited by 259 publications

References 52 publications

CO2‐bearing fluid inclusions associated with diamonds in zircon from the UHP Kokchetav gneisses

CO2‐bearing fluid inclusions associated with diamonds in zircon from the UHP Kokchetav gneisses

Tectonic record, magmatic history and hydrothermal alteration in the Hercynian Guérande leucogranite, Armorican Massif, France

Petrogenesis of rare-metal pegmatites in high-grade metamorphic terranes: a case study from the Lewisian Gneiss Complex of north-west Scotland

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Product

Resources

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CO₂‐bearing fluid inclusions associated with diamonds in zircon from the UHP Kokchetav gneisses

CO₂‐bearing fluid inclusions associated with diamonds in zircon from the UHP Kokchetav gneisses