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    Wyświetlanie 1-7 z 7
    Tytuł:
    Geochemistry and Tectonic Environments of Aphibolites Bethampudi Anorthosite Complex, Khammam Schist Belt, Telangana, India
    Autorzy:
    Brahmaiah, T.
    Ravi, Ch.
    Basha, U. Imran
    Prasad, K. S. Sai
    Tematy:
    E-MORB and Subduction zone
    Geochemistry and Tectonic Environments
    MORB
    N-MORB
    Tholeiitic
    Pokaż więcej
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Powiązania:
    https://bibliotekanauki.pl/articles/1075430.pdf  Link otwiera się w nowym oknie
    Opis:
    The Bethampudi anorthosite complex is essentially a leucograbbro (gabboric anorthosite and anorthositic gabbro), anorthosites, amphibolites, and pegmatite occur as concordant or discordent bodies. This work involves detailed geological geochemical investigations of amphibolites so as to reveal their possible protolith. The field relaltions, major, trace and rare earth element compositions of ampbibolites suggest that they are petrogenetically related to anorthosites by fractional crystallisation. Protoliths of the amphibolites show a tholeiitic signature that prevails over the sub-alkaline nature and E-MORB affinities. They were generated from a depleted mantle surface with the influence of a subduction and within-plate components.
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Geochemistry and tectonic setting of the Chah-Bazargan sub-volcanic mafic dykes, south Sanandaj–Sirjan Zone (SSZ), Iran
    Autorzy:
    Fazlnia, A.
    Tematy:
    alkali sub-volcanic mafic dykes
    Chah-Bazargan intrusions
    phlogopite-spinel
    lherzolite
    subduction zone
    Neotethys
    Pokaż więcej
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Powiązania:
    https://bibliotekanauki.pl/articles/2059776.pdf  Link otwiera się w nowym oknie
    Opis:
    The Chah-Bazargan sub-volcanic mafic dykes (trachybasalt and basaltic trachyandesite) are located in the south of the Sanandaj–Sirjan Zone (SSZ), Iran. The dyke mineralogy mostly comprises amphibole, clinopyroxene, olivine, orthopyroxene, and plagioclase as phenocrysts and fine-grained plagioclase and some ferromagnesian minerals in the matrix. The rocks are alkaline and shoshonitic in composition. The mafic melts relate to Neotethys subduction activity beneath the southern SSZ in the ~Eocene–Miocene interval. Markedly positive Ba, U, K, Pb, and Sr and negative HFSE (high field strength elements: Nb, Ta, Zr, Hf, P, and Ti) anomalies demonstrate this subduction. The sub-volcanic mafic dykes were produced from a metasomatized upper lithospheric mantle wedge at a depth consistent with the stability field of phlogopite-spinel (or -spinel/garnet) lherzolite. Geochemical studies on the basis of the rare earth elements (REE) and HFSE, and large ion lithophile elements (LILE) display that the mantle wedge underwent degrees of partial melting averaging between 5 and 15% to form the Chah-Bazargan sub-volcanic mafic dykes. It is possible that the chemical composition of the rocks was changed due to fractional crystallization and crustal contamination during emplacement.
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Geochemical and tectonic significance of the Arbat alkali gabbro-monzonite-syenite intrusions, Urumieh-Dokhtar Magmatic Arc, Iran
    Autorzy:
    Fazlnia, Abdolnaser
    Tematy:
    gabbro-monzonite-syenite complex
    geochemistry
    collisional zone
    Neotethys subduction
    Pokaż więcej
    Wydawca:
    Państwowy Instytut Geologiczny – Państwowy Instytut Badawczy
    Powiązania:
    https://bibliotekanauki.pl/articles/2058601.pdf  Link otwiera się w nowym oknie
    Opis:
    The Oligocene Arbat alkali intrusions of the Eastern Miandoab are located in the northwestern part of Iran and belong to the Urumieh-Dokhtar Magmatic Arc (UDMA). The intrusions show a ring structure with gabbro-monzogabbro-monzodiorite (mafic units) on the edges, with monzonite-monzosyenite-syenite (felsic units) gradually going towards the central parts. The textures in different rock types are cumulate, granular and laminated. The high values of (La/Sm)n and (La/Yb)n, contents of K, Rb and Cs (positive anomalies normalized on the basis of the primitive mantle), low concentrations of Hf, Nb, Zr and Ta (negative anomalies), and the changes in Th/Nb, Th/Ta, La/Nb and Ce/Pb ratios along with the geochemical and tectonic setting evidence exhibit a subduction-modified mantle origin for the formation of these rocks. Accordingly, the intrusions were formed between the Central Iran and the Arabian plates as a result of the partial melting of a mantle wedge at a syn-collision or post-collision arc-related environment. Our data suggested that, after the end of the oblique Neotethys subduction and during/after the continental collision, the break-off or rollback of the Neotethys slab beneath western Iran, in the Oligocene, might have occurred. Such a process led to the change in the geothermal gradient of the mantle wedge because of the subduction fluids, transtension, pressure reduction along the SE-trending lateral depth strike-slip fault zones in the upper part of the mantle wedge, decompression partial melting at the mantle, and the resulting formation of a mafic potassium-rich melt. The mafic magma was injected into crustal magma chambers; probably, the fractional crystaliization and partial contamination occurred with crustal components, forming the intermediate and felsic rocks in the intrusions. Geochemical evidence related to the variations in the ratios of Th/Yb, Ta/Yb, Rb/Y, and Nb/Y and Harker variation diagrams along with the spider diagrams confirmed fractional crystallization and partial FC (fractional crystallization) and AFC (assimilation and fractional crystallization) in the intrusions.
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-7 z 7

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