Olivine-hosted melt inclusions in Pliocene–Quaternary lavas from the Qorveh–Bijar volcanic belt, western Iran: implications for source lithology and cooling history

Silicate melt inclusions (SMIs) are small droplets of magma that become trapped in minerals during crystal growth. SMIs in olivine crystals can provide critical information on the range of melt compositions and processes that occur during melt generation, evolution, transport, and eruption. The Pliocene–Quaternary volcanic rocks in the Qorveh–Bijar volcanic belt of western Iran show porphyritic and microlithic textures, with olivine and clinopyroxene being the dominant minerals. Magnesian olivines in these volcanic rocks contain primary SMIs. The composition and characteristic of olivine-hosted SMI of these rocks are investigated to constrain the source lithology for mafic volcanism. Bulk compositions of the SMIs overlap those of their host rocks and extend to higher CaO/Al2O3 values. The estimated entrapment pressures and temperatures of the studied SMIs are 9.1–10.3 kbar and 1220–1355°C. The calculated mafic parental melt contains 42.36 wt.% SiO2, low total alkalis (3.22 wt.%), and high MgO (16.1 wt.%). Exploratory calculations using pMELTS show that this parental composition underwent variable degrees of fractional crystallization, as reflected by the variable compositions of the SMIs. Several lines of evidence including pyroxene xenocrysts and high FeO/MnO, FC3MS (FeO/CaO–3*MgO/SiO2), and Zn/Fe ratios (14–21), suggest that a metasomatized pyroxenitic source contributed to the genesis of the parental melt. Amphibole in the SMIs indicates a high volatile content in the parental melt, which we conclude was generated from a metasomatized lithospheric mantle source. The pyroxenite source also contained garnet. Our geochemical results lead us to propose a new petrogenetic model. Specifically, we infer that a dense and unstable portion of the lithosphere underwent localized laminar detachment and downward flow, i.e. lithospheric drip. This drip underwent volatile-enhanced partial melting during descent through the underlying hot asthenosphere and generated the studied volcanic rocks.

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Work Title Olivine-hosted melt inclusions in Pliocene–Quaternary lavas from the Qorveh–Bijar volcanic belt, western Iran: implications for source lithology and cooling history
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Open Access
Creators
  1. Nafiseh Salehi
  2. Ashraf Torkian
  3. Tanya Furman
Keyword
  1. Silicate melt inclusions
  2. Drip magmatism
  3. Basanitic rocks
  4. Olivine
  5. Fractional crystallization
  6. Qorveh-Bijar
  7. Kurdistan
  8. Iran
License In Copyright (Rights Reserved)
Work Type Article
Publisher
  1. International Geology Review
Publication Date January 29, 2019
Publisher Identifier (DOI)
  1. https://doi.org/10.1080/00206814.2018.1564890
Deposited July 21, 2022

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  • Added 2019_Nafis_Olivine_melt_inclusions.pdf
  • Added Creator Nafiseh Salehi
  • Added Creator Ashraf Torkian
  • Added Creator Tanya Furman
  • Published
  • Updated Work Title, Keyword, Subtitle, and 1 more Show Changes
    Work Title
    • Olivine-hosted melt inclusions in Pliocene–Quaternary lavas from the Qorveh–Bijar volcanic belt, western Iran
    • Olivine-hosted melt inclusions in Pliocene–Quaternary lavas from the Qorveh–Bijar volcanic belt, western Iran: implications for source lithology and cooling history
    Keyword
    • Silicate melt inclusions, Drip magmatism, Basanitic rocks, Olivine, Fractional crystallization, Qorveh-Bijar, Kurdistan, Iran
    Subtitle
    • implications for source lithology and cooling history
    Publication Date
    • 2020-09-21
    • 2019-01-29
  • Updated