Yimengite of K–Ti metasomatic origin in kimberlitic rocks from Venezuela

AbstractThis second recorded occurrence of yimengite, K(Cr, Ti, Fe, Mg, Al)12O19, is in a Precambrian kimberlitic sill in the Guaniamo District of Bolivar Province, Venezuela. The paragenesis is similar to that of the type area in Shandong Province, China, where the mineral is in kimberlite dykes. At both localities the yimengite is a K, Ti-bearing metasomatic product of chromium-rich spinel. In the Venezuela rocks the spinels are of the type occurring both as diamond inclusions and as a component of diamond-related Cr-rich garnet harzburgite mantle xenoliths. Yimengite contains significant amounts of barium (up to 3.4wt.% BaO) and is thus transitional to the recently described mineral hawthorneite, Ba(Cr, Ti, Fe, Mg)12O19. Both members are part of a suite of titanate minerals found in kimberlites and their inclusions which has been described by Haggerty and coworkers; they formed as a result of mantle metasomatism generated by K- and Ba-rich fluids. In Venezuela, metasomatism of this type would appear to be deeper than that usually recorded, namely in the basal lithosphere. The metasomatizing fluids are derived from the underlying, more oxygenated asthenosphere. The host kimberlitic rocks are not significantly enriched in K and Ba, but these elements are concentrated in later micaceous dykes which are conjectured to have been generated within similar metasomatized mantle.

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The trapped fluid phase in upper mantle xenoliths from Victoria, Australia: implications for mantle metasomatism

Contributions to Mineralogy and Petrology ◽

10.1007/bf00371413 ◽

1984 ◽

Vol 88 (1-2) ◽

pp. 72-85 ◽

Cited By ~ 129

Author(s):

T. Andersen ◽

Suzanne Y. O'Reilly ◽

W. L. Griffin

Keyword(s):

Upper Mantle ◽

Fluid Phase ◽

Mantle Metasomatism ◽

Mantle Xenoliths

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Metasomatized mantle xenoliths from Canastra-1 kimberlite, southern edge of the São Francisco Craton

10.7185/gold2021.7152 ◽

2021 ◽

Author(s):

Luisa Braga ◽

Fernanda Gervasoni ◽

Maurizio Mazzucchelli ◽

Tommaso Giovanardi ◽

Eduardo Novais Rodrigues ◽

...

Keyword(s):

Mantle Xenoliths ◽

Metasomatized Mantle

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Nixonite, Na2Ti6O13, a new mineral from a metasomatized mantle garnet pyroxenite from the western Rae Craton, Darby kimberlite field, Canada

American Mineralogist ◽

10.2138/am-2019-7023 ◽

2019 ◽

Vol 104 (9) ◽

pp. 1336-1344

Author(s):

Chiara Anzolini ◽

Fei Wang ◽

Garrett A. Harris ◽

Andrew J. Locock ◽

Dongzhou Zhang ◽

...

Keyword(s):

Spectroscopic Analysis ◽

Mantle Xenoliths ◽

New Mineral ◽

Monoclinic Space Group ◽

Calculated Density ◽

Cell Parameters ◽

Garnet Pyroxenite ◽

Mohs Hardness ◽

Kimberlite Field ◽

Metasomatized Mantle

Abstract Nixonite (IMA 2018-133), ideally Na2Ti6O13, is a new mineral found within a heavily metasomatized pyroxenite xenolith from the Darby kimberlite field, beneath the west-central Rae Craton, Canada. It occurs as microcrystalline aggregates, 15 to 40 μm in length. Nixonite is isostructural with jeppeite, K2Ti6O13, with a structure consisting of edge- and corner-shared titanium-centered octahedra that enclose alkali-metal ions. The Mohs hardness is estimated to be between 5 and 6 by comparison to jeppeite, and the calculated density is 3.51(1) g/cm3. Electron microprobe wavelength-dispersive spectroscopic analysis (average of 6 points) yielded: Na2O 6.87, K2O 5.67, CaO 0.57, TiO2 84.99, V2O3 0.31, Cr2O3 0.04, MnO 0.01, Fe2O3 0.26, SrO 0.07, total 98.79 wt%. The empirical formula, based on 13 O atoms, is: (Na1.24K0.67Ca0.06)Σ1.97(Ti5.96V0.023Fe0.018)Σ6.00O13 with minor amounts of Cr and Mn. Nixonite is monoclinic, space group C2/m, with unit-cell parameters a = 15.3632(26) Å, b = 3.7782(7) Å, c = 9.1266(15) Å, β = 99.35(15)°, and V = 522.72(1) Å3, Z = 2. Based on the average of seven integrated multi-grain diffraction images, the strongest diffraction lines are [dobs in Å (I in %) (hkl)]: 3.02 (100) (310), 3.66 (75) (110), 7.57 (73) (200), 6.31 (68) (201), 2.96 (63) (311), 2.96 (63) (203), and 2.71 (62) (402). The five main Raman peaks of nixonite, in order of decreasing intensity, are at 863, 280, 664, 135, and 113 cm–1. Nixonite is named after Peter H. Nixon, a renowned scientist in the field of kimberlites and mantle xenoliths. Nixonite occurs within a pyroxenite xenolith in a kimberlite, in association with rutile, priderite, perovskite, freudenbergite, and ilmenite. This complex Na-K-Ti-rich metasomatic mineral assemblage may have been produced by a fractionated Na-rich kimberlitic melt that infiltrated a mantle-derived garnet pyroxenite and reacted with rutile during kimberlite crystallization.

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Isotopic analyses of clinopyroxene in mantle xenoliths demonstrate the effects of kimberlite melt metasomatism upon the lithospheric mantle

10.5194/egusphere-egu2020-5331 ◽

2020 ◽

Author(s):

Angus Fitzpayne ◽

Andrea Giuliani ◽

Janet Hergt ◽

Jon Woodhead ◽

Roland Maas

Keyword(s):

Trace Element ◽

Lithospheric Mantle ◽

Mantle Metasomatism ◽

Mantle Xenoliths ◽

Isotopic Compositions ◽

Isotopic Analyses ◽

Cretaceous Magmatism

As clinopyroxene is the main host of most lithophile elements in the lithospheric mantle, the trace element and radiogenic isotope systematics of this mineral have frequently been used to characterise mantle metasomatic processes. To further our understanding of mantle metasomatism, both solution-mode Sr-Nd-Hf-Pb and in situ trace element and Sr isotopic data have been acquired for clinopyroxene grains from a suite of peridotite (lherzolites and wehrlites), MARID (Mica-Amphibole-Rutile-Ilmenite-Diopside), and PIC (Phlogopite-Ilmenite-Clinopyroxene) rocks from the Kimberley kimberlites (South Africa). The studied mantle samples can be divided into two groups on the basis of their clinopyroxene trace element compositions, and this subdivision is reinforced by their isotopic ratios. Type 1 clinopyroxene, which comprises PIC, wehrlite, and some sheared lherzolite samples, is characterised by low Sr (~100&#8211;200 ppm) and LREE concentrations, moderate HFSE contents (e.g., ~40&#8211;75 ppm Zr; La/Zr < 0.04), and restricted isotopic compositions (e.g., 87Sr/86Sri = 0.70369&#8211;0.70383; &#949;Ndi = +3.1 to +3.6) resembling those of their host kimberlite magmas. Available trace element partition coefficients can be used to show that Type 1 clinopyroxenes are close to equilibrium with kimberlite melt compositions, supporting a genetic link between kimberlites and these metasomatised lithologies. Thermobarometric estimates for Type 1 samples indicate equilibration depths of 135&#8211;155 km within the lithosphere, thus showing that kimberlite melt metasomatism is prevalent in the deeper part of the lithosphere beneath Kimberley. In contrast, Type 2 clinopyroxenes occur in MARID rocks and coarse granular lherzolites, which derive from shallower depths (<130 km), and have higher Sr (~350&#8211;1000 ppm) and LREE contents, corresponding to higher La/Zr of >~0.05. The isotopic compositions of Type 2 clinopyroxenes are more variable and extend from compositions resembling the &#8220;enriched mantle&#8221; towards those of Type 1 rocks (e.g., &#949;Ndi = -12.7 to -4.4). To constrain the source of these variations, in situ Sr isotope analyses of clinopyroxene were undertaken, including zoned grains in Type 2 samples. MARID and lherzolite clinopyroxene cores display generally radiogenic but variable 87Sr/86Sri values (0.70526&#8211;0.71177), which might be explained by the interaction between peridotite and melts from different enriched sources with the lithospheric mantle. In contrast, the rims of these Type 2 clinopyroxenes trend towards compositions similar to those of the host kimberlite and Type 1 clinopyroxene from PIC and wehrlites. These results are interpreted to represent clinopyroxene overgrowth during late-stage (shortly before/during entrainment) metasomatism by kimberlite magmas. Our study shows that an early, pervasive, alkaline metasomatic event caused MARID and lherzolite genesis in the lithospheric mantle beneath the Kimberley area, which was followed by kimberlite metasomatism during Cretaceous magmatism. This latter event is the time at which discrete PIC, wehrlite, and sheared lherzolite lithologies were formed, and MARID and granular lherzolites were partly modified.

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Rhenium–osmium isotopes in pervasively metasomatized mantle xenoliths from the Bohemian Massif and implications for the reliability of Os model ages

Chemical Geology ◽

10.1016/j.chemgeo.2016.03.020 ◽

2016 ◽

Vol 430 ◽

pp. 90-107 ◽

Cited By ~ 7

Author(s):

Yulia V. Kochergina ◽

Lukáš Ackerman ◽

Vojtěch Erban ◽

Magdalena Matusiak-Małek ◽

Jacek Puziewicz ◽

...

Keyword(s):

Bohemian Massif ◽

Mantle Xenoliths ◽

Osmium Isotopes ◽

Metasomatized Mantle

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Mathiasite-loveringite and priderite in mantle xenoliths from the Alto Paranaíba Igneous Province, Brazil: genesis and constraints on mantle metasomatism

Open Geosciences ◽

10.2478/s13533-012-0197-5 ◽

2014 ◽

Vol 6 (4) ◽

Cited By ~ 4

Author(s):

Vidyã Almeida ◽

Valdecir Janasi ◽

Darcy Svisero ◽

Felix Nannini

Keyword(s):

Mantle Metasomatism ◽

Mantle Xenoliths ◽

Southeastern Brazil ◽

Chemical Zoning ◽

Ti Oxides ◽

Peridotite Xenoliths ◽

Mantle Enrichment ◽

Alkaline Intrusion ◽

Igneous Province ◽

Mineral Assemblages

AbstractAlkali-bearing Ti oxides were identified in mantle xenoliths enclosed in kimberlite-like rocks from Limeira 1 alkaline intrusion from the Alto Paranaíba Igneous Province, southeastern Brazil. The metasomatic mineral assemblages include mathiasite-loveringite and priderite associated with clinopyroxene, phlogopite, ilmenite and rutile. Mathiasite-loveringite (55–60 wt.% TiO2; 5.2–6.7 wt.% ZrO2) occurs in peridotite xenoliths rimming chromite (∼50 wt.% Cr2O3) and subordinate ilmenite (12–13.4 wt.% MgO) in double reaction rim coronas. Priderite (Ba/(K+Ba)< 0.05) occurs in phlogopite-rich xenoliths as lamellae within Mg-ilmenite (8.4–9.8 wt.% MgO) or as intergrowths in rutile crystals that may be included in sagenitic phlogopite. Mathiasite-loveringite was formed by reaction of peridotite primary minerals with alkaline melts. The priderite was formed by reaction of peridotite minerals with ultrapotassic melts. Disequilibrium textures and chemical zoning of associated minerals suggest that the metasomatic reactions responsible for the formation of the alkali-bearing Ti oxides took place shortly prior the entrainment of the xenoliths in the host magma, and is not connected to old (Proterozoic) mantle enrichment events.

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Phlogopite in mantle xenoliths and kimberlite from the Grib pipe, Arkhangelsk province, Russia: Evidence for multi-stage mantle metasomatism and origin of phlogopite in kimberlite

Geoscience Frontiers ◽

10.1016/j.gsf.2018.12.006 ◽

2019 ◽

Vol 10 (5) ◽

pp. 1941-1959 ◽

Cited By ~ 6

Author(s):

A.V. Kargin ◽

L.V. Sazonova ◽

A.A. Nosova ◽

N.M. Lebedeva ◽

Yu.A. Kostitsyn ◽

...

Keyword(s):

Mantle Metasomatism ◽

Mantle Xenoliths ◽

Grib Pipe ◽

Multi Stage

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First assessment of the noble gas and CO2 isotopic composition of fluid inclusions hosted in mantle xenoliths from El Hierro (Canary Islands)

10.5194/egusphere-egu21-12817 ◽

2021 ◽

Author(s):

Andres Sandoval Velasquez ◽

Andrea Luca Rizzo ◽

Alessandro Aiuppa ◽

Maria Luce Frezzotti ◽

Samantha Remigi ◽

...

Keyword(s):

Isotopic Composition ◽

Oceanic Crust ◽

Canary Islands ◽

Fluid Inclusions ◽

Upper Mantle ◽

Noble Gas ◽

Mantle Metasomatism ◽

Mantle Xenoliths ◽

Local Source ◽

El Hierro

Studying the isotopic composition of fluids trapped in mantle xenoliths opens avenues to understanding the origin and cycling of volatiles in the Earth&#8217;s upper mantle. Here, we present the first isotopic results for noble gases and CO2 in fluid inclusions (FI) trapped in mantle xenoliths from El Hierro the youngest island of the Canarian archipelago. Our results are based on 6 mantle xenolith samples (3 Spinel-lherzolites and 3 Spinel-harzburgites) collected from the El Julan cliff valley (Oglialoro et al., 2017), from which we hand-picked crystals of Ol, Opx, and Cpx. Isotopic determinations were performed at the INGV (Sezione di Palermo) noble gas and stable isotopes laboratories, following the preparation methods and analytical procedures described in Rizzo et al. (2018 and references therein).The Ne-Ar isotopic compositions reveal the presence of an atmospheric component in the FI. Most of the samples exhibit 4He/20Ne ratios > 60, 20Ne/22Ne ratios between 9.84 and 10.49, 21Ne/22Ne ratios from 0.0295 to 0.0330, and 40Ar/36Ar > 800, suggesting mixing between MORB-like mantle fluids and an air-derived component. We argue this latter may (at least in part) derive from upper mantle recycling of atmospheric fluids via paleo-subduction event(s). Excluding samples possibly affected by diffusive fractionation processes, the average Rc/Ra ratio (3He/4He ratio corrected for atmospheric contamination) measured in El Hierro xenoliths is ~7.45 + 0.26 Ra, within the MORB range (8 + 1 Ra; Graham, 2002). The He homogeneous signature of these xenoliths agrees well with the 3He/4He compositions previously reported in lava phenocrysts and cumulates (Day and Hilton, 2011) and is slightly below the maximum ratios measured in groundwater samples during the 2012 volcanic unrest (~8.2 Ra; Padron et al., 2013). All these pieces of evidence argue against a primordial source involved in the local lithospheric mantle. Putting these data in the context of previous literature results for FI and surface gases in the Canary Islands (La Palma, La Gomera, Tenerife, Gran Canaria, and Lanzarote), we identify an eastward 3He/4He decreasing trend that parallels a corresponding increase of the oceanic crust thickness. In addition to the mantle heterogeneity, we propose that part of the 3He/4He east-to-west variation along the archipelago is caused by the variable thickness of the oceanic crust (and hence, different interactions with 4He-rich crustal fluids during emplacement).The FI &#948;13C(CO2) isotopic composition ranges from -2.38 to -1.23&#8240; in pyroxenes and -0.2 to +2.0&#8240; in olivine. These unusually positive &#948;13C compositions support the existence of a recycled crustal carbon component in the local source mantle, likely pointing to mantle metasomatism (Oglialoro et al., 2017) from fluids carrying carbon from subducted sediments and/or altered oceanic crust (AOC).

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