Pleistocene alkaline rocks of Martin Vaz volcano, South Atlantic: low-degree partial melts of a CO2-metasomatized mantle plume

2018 ◽  
Vol 61 (3) ◽  
pp. 296-313 ◽  
Author(s):  
Anderson C. Santos ◽  
Mauro C. Geraldes ◽  
Wolfgang Siebel ◽  
Julio Mendes ◽  
Everton Bongiolo ◽  
...  
Keyword(s):  
Mantle Plume ◽  
South Atlantic ◽  
Alkaline Rocks ◽  
Low Degree ◽  
Partial Melts ◽  
Metasomatized Mantle

scholarly journals Causes and consequences of asymmetric lateral plume flow during South Atlantic rifting

2020 ◽  
Vol 117 (45) ◽  
pp. 27877-27883
Author(s):  
Jason P. Morgan ◽  
Jorge M. Taramón ◽  
Mario Araujo ◽  
Jörg Hasenclever ◽  
Marta Perez-Gussinye
Keyword(s):  
Mantle Plume ◽  
Numerical Experiments ◽  
Three Dimensional ◽  
South Atlantic ◽  
Continental Lithosphere ◽  
Rifted Margins ◽  
Plume Flow ◽  
Rifted Margin ◽  
Asymmetrically Distributed ◽  
Lateral Variations

Volcanic rifted margins are typically associated with a thick magmatic layer of seaward dipping reflectors and anomalous regional uplift. This is conventionally interpreted as due to melting of an arriving mantle plume head at the onset of rifting. However, seaward dipping reflectors and uplift are sometimes asymmetrically distributed with respect to the subsequent plume track. Here we investigate if these asymmetries are induced by preexisting lateral variations in the thickness of continental lithosphere and/or lithospheric stretching rates, variations that promote lateral sublithospheric flow of plume material below only one arm of the extending rift. Using three-dimensional numerical experiments, we find that South Atlantic rifting is predicted to develop a strong southward asymmetry in its distribution of seaward dipping reflectors and associated anomalous relief with respect to the Tristan Plume that “drove” this volcanic rifted margin, and that the region where plume material drains into the rift should experience long-lived uplift during rifting—both as observed. We conclude that a mantle plume is still needed to source the anomalously hot sublithospheric material that generates a volcanic rifted margin, but lateral along-rift flow from this plume, not a broad starting plume head, is what controls when and where a volcanic rifted margin will form.

scholarly journals High-pressure elastic properties of dolomite melt supporting carbonate-induced melting in deep upper mantle

2020 ◽  
Vol 117 (31) ◽  
pp. 18285-18291
Author(s):  
Man Xu ◽  
Zhicheng Jing ◽  
Suraj K. Bajgain ◽  
Mainak Mookherjee ◽  
James A. Van Orman ◽  
...  
Keyword(s):  
Elastic Properties ◽  
Upper Mantle ◽  
Source Region ◽  
Partial Melt ◽  
Low Degree ◽  
Seismic Detection ◽  
Initial Melting ◽  
Partial Melts ◽  
Dynamics Simulations ◽  
Geochemical Studies

Deeply subducted carbonates likely cause low-degree melting of the upper mantle and thus play an important role in the deep carbon cycle. However, direct seismic detection of carbonate-induced partial melts in the Earth’s interior is hindered by our poor knowledge on the elastic properties of carbonate melts. Here we report the first experimentally determined sound velocity and density data on dolomite melt up to 5.9 GPa and 2046 K by in-situ ultrasonic and sink-float techniques, respectively, as well as first-principles molecular dynamics simulations of dolomite melt up to 16 GPa and 3000 K. Using our new elasticity data, the calculated VP/VSratio of the deep upper mantle (∼180–330 km) with a small amount of carbonate-rich melt provides a natural explanation for the elevated VP/VSratio of the upper mantle from global seismic observations, supporting the pervasive presence of a low-degree carbonate-rich partial melt (∼0.05%) that is consistent with the volatile-induced or redox-regulated initial melting in the upper mantle as argued by petrologic studies. This carbonate-rich partial melt region implies a global average carbon (C) concentration of 80–140 ppm. by weight in the deep upper mantle source region, consistent with the mantle carbon content determined from geochemical studies.

First petrologic data for Vitória Seamount, Vitória-Trindade Ridge, South Atlantic: a contribution to the Trindade mantle plume evolution

2021 ◽  
Vol 109 ◽  
pp. 103304
Author(s):  
Thais Mothé Maia ◽  
Anderson Costa dos Santos ◽  
Eduardo Reis Vianna Rocha-Júnior ◽  
Claudio de Morisson Valeriano ◽  
Julio Cezar Mendes ◽  
...  
Keyword(s):  
Mantle Plume ◽  
South Atlantic

The Spi Lake Formation of the central Hearne domain, western Churchill Province, Canada: an axial intracratonic continental tholeiite trough above the cogenetic Kaminak dyke swarmGeological Survey of Canada Contribution 20070462.

2008 ◽  
Vol 45 (6) ◽  
pp. 745-767 ◽  
Author(s):  
Hamish A. Sandeman ◽  
James J. Ryan
Keyword(s):  
Dyke Swarm ◽  
Lake Basin ◽  
Low Degree ◽  
Lake Formation ◽  
Mid Ocean Ridge ◽  
Supracrustal Belt ◽  
Partial Melts ◽  
Continental Lithospheric Mantle ◽  
Ocean Ridge ◽  
Hurwitz Group

The Spi Group is a package of plagioclase porphyritic, amygdaloidal basalt flows and sandstone (Spi Lake Formation) conformably overlain by coarse conglomerate and sandstone (Old Boot Formation). These unconformably overlie the Kaminak Lake segment of the Central Hearne supracrustal belt, western Churchill Province. The Spi Group developed in a small, isolated basin (8 km2) and is older than the Paleoproterozoic Hurwitz Group. Our data demonstrate that the basalts of the Spi Lake Formation are genetically related to the ca. 2450 Ma Kaminak dyke swarm, a speculation previously promoted by some workers based on field characteristics alone. They are continental tholeiites with large ion lithophile and light rare-earth element enriched multielement profiles with prominent high field-strength element troughs. The 143Nd/144Nd compositions overlap the contemporaneous chondritic bulk-earth data. All of these are features we infer to have resulted from mixing of melts from dominantly depleted mid-ocean ridge basalt (MORB) mantle with low-degree partial melts of metasomatically enriched sub-continental lithospheric mantle. These composite magmas then underwent clinopyroxene + plagioclase ± olivine fractionation with minor assimilation of local tonalitic middle crust. The Spi Lake basin is <1 km wide, trends 020° parallel to Kaminak dykes but is discordant to the more common 045° to 070° trends of fold keels of the Hurwitz Group. The basin is a graben filled first with basalt and then molassoid sediments, representing the expression of crustal extension associated with Kaminak dyke emplacement. This indicates that the present erosional surface in the region is broadly at the same level as at the time of both Hurwitz and Spi Group deposition.

Rifting, subsidence and continental break-up above a mantle plume in the central South Atlantic

2013 ◽  
Vol 369 (1) ◽  
pp. 185-214 ◽  
Author(s):  
David G. Quirk ◽  
Michael Hertle ◽  
Jon W. Jeppesen ◽  
Madeleine Raven ◽  
Webster Ueipass Mohriak ◽  
...  
Keyword(s):  
Mantle Plume ◽  
South Atlantic ◽  
Break Up ◽  
Central South

Middle Jurassic ultramafic lamprophyre dyke within the Ferrar magmatic province, Pensacola Mountains, Antarctica

2000 ◽  
Vol 64 (1) ◽  
pp. 95-111 ◽  
Author(s):  
P. T. Leat ◽  
T. R. Riley ◽  
B. C. Storey ◽  
S. P. Kelley ◽  
I. L. Millar
Keyword(s):  
Trace Elements ◽  
Mantle Plume ◽  
Lithospheric Mantle ◽  
Liquid Immiscibility ◽  
Radiogenic Isotopes ◽  
Ultramafic Lamprophyre ◽  
Low Degree ◽  
Layered Gabbro ◽  
Partial Fusion ◽  
Incompatible Trace Elements

AbstractAn ultramafic lamprophyre dyke is described from the otherwise tholeiitic Ferrar magmatic province of Antarctica. We report an Ar-Ar age of 183 ± 2.2 Ma for the dyke, indistinguishable from those of the Ferrar tholeiites. However, the dyke has mineralogical and major and trace element compositions, and radiogenic isotopes ratios, very different from the Ferrar tholeiites. The sample consists of olivine and rare clinopyroxene phenocrysts with perovskite and spinel microphenocrysts in a groundmass of amphibole, nepheline and biotite. Carbonatitic globules contain calcite, dolomite, Fe-rich carbonate, nepheline, biotite, orthoclase, pyrite, clinopyroxene, apatite and silicate glass, and were formed by liquid immiscibility. The rock is mildly potassic and classifies as an ouachitite. It is strongly enriched in both moderately and highly incompatible trace elements and is the first high-Ti rock to be described from the Ferrar magmatic province. The rock has similar initial 143Nd/144Nd to OIB, notably Bouvet, Crozet and Réunion, but significantly higher initial 87Sr/86Sr. The lamprophyre magma is interpreted as having been generated by low-degree partial fusion of metasomatized lithospheric mantle as a result of heat conducted from an underlying Jurassic mantle plume. The same mantle plume was probably also responsible for generating one of the world’s largest layered gabbro bodies, the Dufek-Forrestal intrusions.

Mineral-melt-fluid composition of carbonate-bearing cumulate xenoliths in Tertiary alkali basalts of southern Slovakia

2007 ◽  
Vol 71 (1) ◽  
pp. 63-79 ◽  
Author(s):  
V. Hurai ◽  
M. Huraiová ◽  
P. Konečný ◽  
R. Thomas
Keyword(s):  
Partial Melting ◽  
Central Europe ◽  
Melt Inclusions ◽  
Fluid Composition ◽  
Alkali Basalts ◽  
Mantle Mineral ◽  
Low Degree ◽  
Multiphase Fluid ◽  
Textural Evidence ◽  
Metasomatized Mantle

AbstractTwo types of carbonatic cumulate xenoliths occur in alkali basalts of the northern part of the Carpatho-Pannonian region, Central Europe. One is dominated by Ca-Fe-Mg carbonates with randomly distributed bisulphide globules (Fe1+xS2, x = 0–0.1), Mg-Al spinel, augite, rhönite, Ni-Co-rich chalcopyrite, and a Fe(Ni,Fe)2S4 phase. The second, carbonatic pyroxenite xenolith type, is composed of diopside, subordinate fluorapatite, interstitial Fe-Mg carbonates, and accessory K-pargasite, F-Al-rich ferroan phlogopite, Mg-Al spinel, albite and K-feldspar. All accessory minerals occur in ultrapotassic dacite-trachydacite glass in primary silicate melt inclusions in diopside, together with calcio-carbonatite and CO2-N2-CO inclusions. Textural evidence is provided for multiphase fluid-melt immiscibility in both xenolith types. The carbonatic pyroxenite type is inferred to have accumulated from differentiated, volatile-rich, ultrapotassic magma derived by a very low-degree partial melting of strongly metasomatized mantle. Mineral indicators point to a genetic link between the carbonatite xenolith with olivine-fractionated, silica-undersaturated alkalic basalt ponded at the mantle-crust boundary.

scholarly journals Petrography and Geochemistry of the Leucocratic Rocks in the Ophiolites from the Pollino Massif (Southern Italy)

Minerals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1264
Author(s):  
Giovanna Rizzo ◽  
Roberto Buccione ◽  
Michele Paternoster ◽  
Salvatore Laurita ◽  
Luigi Bloise ◽  
...  
Keyword(s):  
Trace Elements ◽  
Southern Italy ◽  
Major And Trace Elements ◽  
Western Alps ◽  
Geodynamic Evolution ◽  
Ophiolitic Rocks ◽  
Partial Melts ◽  
First Time ◽  
Northern Alps ◽  
Metasomatized Mantle

In the Tethyan realm, leucocratic rocks were recognized as dikes and layers outcropping in the ophiolitic rocks of the Western Alps, in Corsica, and in the Northern Apennines. Several authors have suggested that the origin of leucocratic rocks is associated with partial melting of cumulate gabbro. Major and trace elements composition and paragenesis provided information about the leucocratic rocks genetic processes. This research aims at disclosing, for the first time, the petrographical and geochemical features of Timpa delle Murge leucocratic rocks, Pollino Massif (southern Italy), in order to discuss their origin and geodynamic significance through a comparison with other Tethyan leucocratic rocks. These rocks are characterized by high amounts of silica with moderate alumina and iron-magnesium contents showing higher potassium contents than plagiogranites, due to plagioclase alteration to sericite. Plagioclase fractionation reflects negative Eu anomalies indicating its derivation from gabbroic crystal mushes. The chondrite normalized REEs patterns suggest the participation of partial melts derived from a metasomatized mantle in a subduction environment. The results reveal some similarities in composition with other Tethyan leucocratic rocks, especially those concerning Corsica and the Northern Alps. These new data provide further clues on the origin of these leucocratic rocks and the Tethyan area geodynamic evolution.

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