Pyroxenites and megacrysts from Vitim picrite-basalts (Russia): Polybaric fractionation of rising melts in the mantle?

Ashchepkov, Igor; André, Luc; Downes, Hilary; Belyatsky, B. V.

doi:10.1016/j.jseaes.2011.03.004

Cited by 54 publications

(41 citation statements)

References 110 publications

(194 reference statements)

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“…15B), the degree of melting must be w0.05e0.1%, and the Gar/Cpx ratio of the parental rocks should be rather high (1e2) (Fig. 2, Supplement 3) which corresponds to harzburgites, because lherzolitic clinopyroxenes should have asymmetric belllike patterns (Ashchepkov et al, 2011). Such characteristics of the studied regions are also shown by some mantle clinopyroxenes from the Alakit field (Ashchepkov et al, 2004).…”

Section: Geochemistry Of Minerals and Parental Melts As The Signs Of mentioning

confidence: 65%

“…Deeper in the range from 5.0 to 3.5 GPa, the joint PT estimates for garnets and ilmenites indicate the presence of metasomatic ilmenite peridotites, judging by the agreement of calculations of Fe # in Ol equilibrated with ilmenites and garnets. The low-Cr ilmenites fix proto-kimberlitic magma chambers or dense channels at this level created during protokimberlite magma ascent, similar to the processes of megacryst growth in alkali basalts (Ashchepkov et al, 2011). The lower sub-lens in 6.5e5 GPa interval is composed mostly of pyroxenites or wehrlite type with Ca-rich garnets.…”

Section: Ptxf(o 2 ) Conditions Beneath Kharamai Field and Prianabariementioning

confidence: 70%

“…The first (Gr1) is characterized by round patterns with the domination of HREE and smooth decrease of LREE. For the second group (Gr2) the significant hump in MREE with the center near Sm is probably the sign of pyroxenite assemblage (Ashchepkov et al, 2011) (see discussion). For the third group (Gr3) lower HREE and the small minimum in Dy-Er is common and a sign of harzburgitic garnets (and some pyroxenes).…”

Section: Variations Of the Trace Elements In Mineralsmentioning

confidence: 90%

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Comparison of mantle lithosphere beneath early Triassic kimberlite fields in Siberian craton reconstructed from deep-seated xenocrysts

Ashchepkov

Kuligin

Vladykin

et al. 2016

Geoscience Frontiers

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a b s t r a c tMantle xenocrysts from early Triassic kimberlite pipes from Kharamai, Ary-Mastakh and Kuranakh fields in the Anabar shield of Siberia revealing similar compositional trends were studied to estimate the superplume influence on the subcratonic lithosphere mantle (SCLM). Pressure-temperature (PT) reconstructions using monomineral thermobarometry for 5 phases show division of the SCLM beneath the Kharamai field into 6 units: pyroxenitic Fe-rich (1e2 GPa) and Mg-rich (2e3 GPa) layers; middle with two levels of Gar-Sp pyroxenites at w3 and 4e5 GPa; Gar-duniteeharzburgites w4.5e6.5 GPa subjected to Ilm-Px vein metasomatism; and a Mg-rich dunite lower part. In the Anabar shield (Ary-Mastakh, Dyuken and Kuranakh fields) mantle lithosphere is composed of three large units divided into two parts: upper part with amphiboles and phlogopite; two levels of pyroxenites and eclogites at 3 and 4 GPa, and a lower part composed of refertilized dunites. Diagrams showing P-Fe # Gar clusters for garnets and omphacites illustrate the differences between SCLM of these localities. Differences of Triassic SCLM from Devonian SCLM are in simple layering; abundance of Na-Cr-amphiboles and metasomatism in the upper SCLM part, thick pyroxenite-eclogite layer and lower part depletion, heated from SCLM base to 5.0 GPa.Kharamai mantle clinopyroxenes represent three geochemical types: (1) harzburgitic with inclined linear REE, HFSE troughs and elevated Th, U; (2) lherzolitic or pyroxenitic with round TRE patterns and decreasing incompatible elements; (3) eclogitic with Eu troughs, Pb peak and high LILE content. Calculated parental melts for garnets with humped REE patterns suggest dissolution of former Cpx and depression means Cpx and garnets extraction. Clinopyroxenes from Ary-Mastakh fields show less inclined REE patterns with HMREE troughs and an increase of incompatible elements. Clinopyroxenes from Kuranakh field show flatter spoon-like REE patterns and peaks in Ba, U, Pb and Sr, similar to those in ophiolitic harzburgites. The PT diagrams for the mantle sections show high temperature gradients in the uppermost SCLM accompanied by an increase of P-Fe # Ol upward and slightly reduced thickness of the mantle keel of the Siberian craton, resulting from the influence of the PermianeTriassic superplume, but with no signs of delamination.Ó 2015, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/ licenses/by-nc-nd/4.0/).

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Section: Geochemistry Of Minerals and Parental Melts As The Signs Of mentioning

confidence: 65%

Section: Ptxf(o 2 ) Conditions Beneath Kharamai Field and Prianabariementioning

confidence: 70%

Section: Variations Of the Trace Elements In Mineralsmentioning

confidence: 90%

See 1 more Smart Citation

Comparison of mantle lithosphere beneath early Triassic kimberlite fields in Siberian craton reconstructed from deep-seated xenocrysts

Ashchepkov

Kuligin

Vladykin

et al. 2016

Geoscience Frontiers

Self Cite

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“…It was suggested that the high-temperature garnet-bearing rocks result from repeated affection of basaltic melts on the ambient upper mantle material. From the AFC calculations, it was also inferred that megacrysts and shallow xenoliths crystalized during the rise of basaltic liquids to the surface Ashchepkov et al, 2011). From these observations,…”

Section: Components Of Mantle Sourcesmentioning

confidence: 89%

“…Т>1000°C), and (3) analytical data for trace-element concentrations in minerals are of high quality. The trace element concentrations were defined in xenoliths from picrobasalts and basanites of the Vitim Plateau Glaser et al, 1999;Ashchepkov and Andre, 2002;Ashchepkov et al, 2003Ashchepkov et al, , 2011. Additional trace-element data on Ta, Th, U concentrations in amphibole were taken for xenoliths from basalts of the SW Tian Shan (Zheng et al, 2006).…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Mid-Miocene thermal impact on the lithosphere by sub-lithospheric convective mantle material: Transition from high- to moderate-Mg magmatism beneath Vitim Plateau, Siberia

Chuvashova

Rasskazov

Yasnygina

2017

Geoscience Frontiers

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Magma Storage at Ocean Islands

Barker

Rydeblad

Silva

2021

Geophysical Monograph Series

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The Cape Verde archipelago is a group of Ocean Islands in the Central Atlantic that forms two chains of islands trending Northwest and Southwest. Several of the islands are considered to be volcanically active, with frequent eruptions on Fogo. We examine the mineral chemistry and thermobarometry of the southern islands; Santiago, Fogo and Brava together with the Cadamosto Seamount. Our objective is to explore the magmatic storage system and implications for volcanic eruptions and associated hazards at Cape Verde. The volcanic rocks at Cape Verde are alkaline and dominantly mafic, whereas the island of Brava and the Cadamosto Seamount are unusually felsic. Clinopyroxene compositions range from 60 to 90 Mg# at Santiago and Fogo. In contrast, at Brava and the Cadamosto Seamount the clinopyroxene compositions are 5 to 75 Mg#. Mineral chemistry and zonation records fractional crystallization, recharge, aggregation of crystals, magma mixing and variations in thermal conditions of the magma at temperatures from 925 to 1250ºC. Magma storage depths at Santiago, Fogo, Brava and the Cadamosto Seamount are between 12 and 40 km, forming deep sub-Moho magma storage zones. Transient magma storage in the crust is suggested by fluid inclusion re-equilibration and pre-eruption seismicity. A global compilation of magma storage at Ocean Islands suggests deep magma storage is a common feature and volcanic eruptions are often associated with rapid magma ascent through the crust. Shallow magma storage is more variable and likely reflects local variations in crustal structure, sediment supply and tectonics. Petrological constraints on the magma plumbing system at Cape Verde and elsewhere are vital to integrate with deformation models and seismicity in order to improve understanding and mitigation of the volcanic hazards.

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Pyroxenites and megacrysts from Vitim picrite-basalts (Russia): Polybaric fractionation of rising melts in the mantle?

Cited by 54 publications

References 110 publications

Comparison of mantle lithosphere beneath early Triassic kimberlite fields in Siberian craton reconstructed from deep-seated xenocrysts

Comparison of mantle lithosphere beneath early Triassic kimberlite fields in Siberian craton reconstructed from deep-seated xenocrysts

Mid-Miocene thermal impact on the lithosphere by sub-lithospheric convective mantle material: Transition from high- to moderate-Mg magmatism beneath Vitim Plateau, Siberia

Magma Storage at Ocean Islands

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