Ancient-depleted and enriched mantle lithosphere domains in northern Madagascar: geochemical and isotopic evidence from spinel-to-plagioclase-bearing ultramafic xenoliths

Rocco, Ivana; Zanetti, A.; Melluso, Leone; Morra, Vincenzo

doi:10.1016/j.chemgeo.2017.05.016

Cited by 15 publications

(7 citation statements)

References 74 publications

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“…If the lithosphere is in thermal equilibrium, a plate that is 80–120 km thick is required to bound the observed elevations. This range of thicknesses lies at the upper end of independent lithospheric thickness estimates (Hoggard et al., 2020; Priestley & M c Kenzie, 2013; Rajaonarison et al., 2020; Rocco et al., 2017, this study). If Malagasy lithosphere is thermally disequilibrated following, say, rapid loss of 50 km of lithospheric mantle from the base of the plate then, for the same range of lithospheric thicknesses, topography would be elevated by several hundred meters with respect to equilibrated lithosphere.…”

Section: Crustal and Lithospheric Templatessupporting

confidence: 57%

“…Lithospheric thickness estimates, a 1 , beneath Madagascar are subject to considerable uncertainty. For example, Rocco et al (2017) infer a local maximum lithospheric thickness of 60 km based upon the absence of garnet-bearing peridotitic xenoliths from magmatic rocks in northern Madagascar. This value is ∼30 km thinner than that calculated by Priestley and M c Kenzie (2013), but in closer agreement with the results of Rajaonarison et al (2020) and Hoggard et al (2020), who calculate thicknesses of <80 km beneath the northern and central highlands.…”

Section: Receiver Function Analysesmentioning

confidence: 99%

“…For example, Rocco et al. (2017) infer a local maximum lithospheric thickness of 60 km based upon the absence of garnet‐bearing peridotitic xenoliths from magmatic rocks in northern Madagascar. This value is ∼30 km thinner than that calculated by Priestley and M c Kenzie (2013), but in closer agreement with the results of Rajaonarison et al.…”

Section: Crustal and Lithospheric Templatesmentioning

confidence: 99%

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Cenozoic Dynamic Topography of Madagascar

Stephenson

White

Carter

et al. 2021

Geochem Geophys Geosyst

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It has been proposed that Oligo‐Miocene regional uplift of Madagascar was generated and is maintained by mantle dynamical processes. Expressions of regional uplift include flat‐lying Upper Cretaceous‐Paleogene marine limestones that crop out at elevations of hundreds of meters along the western seaboard and emergent Quaternary coral‐rich terraces that rim the coastline. Here, we explore the history of subcrustal topographic support through a combined analysis of four sets of observational constraints. First, we exploit published receiver function estimates of crustal thickness and spectral admittance between gravity and topography. An admittance value of ∼+40 ± 10 mGal km−1 at wavelengths >500 km implies that ∼1 km of topography is supported by subcrustal processes. Secondly, new apatite fission‐track and helium measurements from 18 basement samples are inverted, constraining temperature and denudation histories. Results suggest that 0.5–1.6 km of regional uplift occurred after ∼30 Ma. Thirdly, we calculate a history of regional uplift by minimizing the misfit between observed and calculated longitudinal river profiles. Results suggest that topography was generated during Neogene times. Finally, inverse modeling of rare earth element concentrations in Neogene mafic rocks indicates that melting of the asthenospheric source occurred at depths of ≤65 km with potential temperatures of 1300–1370 °C. Melting occurred at higher temperatures beneath Réunion Island and northern Madagascar and at lower temperatures beneath the Comores and southern Madagascar. These inferences are consistent with shear wave velocities obtained from tomographic models. We conclude that Madagascar is underlain by thinned lithospheric mantle and that a thermal anomaly lies within an asthenospheric layer beneath northern Madagascar.

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Section: Crustal and Lithospheric Templatessupporting

confidence: 57%

Section: Receiver Function Analysesmentioning

confidence: 99%

Section: Crustal and Lithospheric Templatesmentioning

confidence: 99%

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Cenozoic Dynamic Topography of Madagascar

Stephenson

White

Carter

et al. 2021

Geochem Geophys Geosyst

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“…Like mantle xenoliths from other locations in British Columbia (e.g., Littlejohn and Greenwood 1974;Greenfield et al, 2013), those from the Tasse property display both Melt pockets and spongy textures in SCLM xenoliths have been reported from many locations around the world (Ionov et al 1995(Ionov et al , 1999(Ionov et al , 2006Bonadiman et al, 2005;Wiechert et al, 1997;Carpenter et al, 2002;Arai and Ishimaru, 2008;Su et al, 2011;Liu et al 2017;Ntaflos et al, 2017;Rocco et al, 2017); however, they have only been rarely documented in mantle xenoliths of the Canadian Cordillera . Studies of melt pockets, veins and spongy texture can provide significant new insights into the melting and metasomatism of the SCLM beneath the Canadian Cordillera (see Ionov et al, 1999Ionov et al, , 2006Wiechert et al, 1997;Shaw and Klügel, 2002;Bonadiman et al, 2005;Shaw et al, 2006;Su et al, 2011;Liu et al, 2017;Rocco et al, 2017). What is the source of the low-silica, alkaline (K-and Na-rich) melts and fluids?…”

Section: Petrogenetic Significance Of the Textures In The Tasse Mantlmentioning

confidence: 97%

“…Spongy cpx textures have been reported in SCLM xenoliths from many locations around the world (e.g., Ionov et al, 1995Ionov et al, , 2006Wiechert et al, 1997;Bonadiman et al, 2005;Liu et al 2017;Rocco et al, 2013Rocco et al, , 2017. The origin of these textures has been attributed to either metasomatic reactions (Shaw et al, 2006;Rocco et al, 2013) or decompressional partial melting (Su et al, 2011).…”

Section: Origin Of the Spongy Cpx Texturementioning

confidence: 99%

Petrology and geochemistry of the Tasse mantle xenoliths of the Canadian Cordillera: A record of Archean to Quaternary mantle growth, metasomatism, removal, and melting

et al. 2018

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Mantle xenoliths hosted by the Quaternary Tasse alkaline basalts in the Canadian Cordillera, southeastern British Columbia, are mostly spinel lherzolite originating from subcontinental lithospheric mantle. The xenoliths contain abundant feldspar veins, melt pockets and spongy clinopyroxene, recording extensive alkaline metasomatism and partial melting. Feldspar occurs as veins and interstitial crystal in melt pockets. Melt pockets occur mainly at triple junctions, along grain boundaries, and consist mainly of olivine, cpx, opx and spinel surrounded by interstitial feldspar. The Nd, Sr and Pb isotopic compositions of the xenoliths indicate that their sources are characterized by variable mixtures of depleted MORB mantle and EM1 and EM2 mantle components. Large variations in eNd values (-8.2 to +9.6) and Nd depleted mantle model ages (TDM = 66 to 3380 Ma) are consistent with multiple sources and melt extraction events, and long-term (>3300 Ma) isolation of some source regions from the convecting mantle. Samples with Archean and Paleoproterozoic Nd model ages are interpreted as either have been derived from relict Laurentian mantle pieces beneath the Cordillera or have been eroded from the root of the Laurentian craton to the east and transported to the base of the Cordilleran lithosphere by edge-driven convection currents. The oxygen isotope compositions of the xenoliths (average d 18 O = +5.1±0.5‰) are similar to those of depleted mantle. The average d 18 O values of olivine (+5.0±0.2‰), opx (+5.9±0.6‰), cpx (+6.0±0.6‰) and spinel (+4.5±0.2‰) are similar to mantle values. Large fractionations for olivine-opx, olivine-cpx and opx-cpx pairs, however, reflect disequilibrium stemming from metasomatism and partial melting. Whole-rock trace element, Nd, Sr, Pb and O isotope compositions of the xenoliths and host alkaline basalts indicate different mantle sources for these two suites of rocks. The xenoliths were derived from shallow lithospheric sources, whereas the alkaline basalts originated from a deeper asthenospheric mantle source.

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Alkaline rocks of the Bobaomby volcanic field point to a petrogenetic link between Comoros and northern Madagascar lithosphere

Cucciniello

Grifa

de’Gennaro

et al. 2022

Int J Earth Sci (Geol Rundsch)

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The Bobaomby volcanic field (10–11 Ma) is the northernmost volcanic area of Madagascar, and is a monogenetic volcanic field comprising outcrops of lava flows, dykes, scoria cones, tuff rings and plugs, widely scattered over an area of roughly 500 km2. The volcanic rocks range in composition from nephelinite, basanite and tephrite, through tephritic phonolite, to F- and Cl-rich peralkaline phonolite (MgO from 13 to 0.01 wt%), and the serial affinity varies from sodic to potassic. A few mica-amphibole-rich lamprophyric dykes have tephritic composition and ultrapotassic affinity. The mafic lavas host intrusive xenoliths with evident cumulate features (wehrlites, composite olivine gabbros s.l., amphibole clinopyroxenites and “kaersutitites”), as well as various types of mantle-derived xenoliths and xenocrysts in the most primitive rocks. The very wide compositional variations of the observed phases (olivine, clinopyroxene, amphibole, oxides, feldspars, feldspathoids, apatite, titanite, aenigmatite and other accessories) in lavas, dykes and cognate xenoliths are fully consistent with the variable degree of differentiation of the host lavas/dykes, and pointing out to limited open-system or polybaric crystallization. The mafic lavas have marked enrichment in incompatible elements and light rare-earth element (LREE) (e.g., Lan/Ybn = 19–27), whereas concave REE patterns are found in the peralkaline phonolites, as a result of removal of accessory titanite starting from tephritic phonolite magmas. The gabbroic/ultramafic xenoliths are interpreted as crustal cumulates of basanitic and tephritic magmas. Several liquid lines of descent in the basanites and tephrites are evident from the trace-element distribution, and from the differing geochemistry of the evolved rocks. The isotopic compositions reach extreme values (e.g., 206Pb/204Pb = 20.065 in the ultrapotassic lamprophyre) when compared to the rest of the Cenozoic/Recent Madagascan volcanic rocks, but similar to those of the Comoros archipelago, suggesting analogies of mantle sources and enrichment processes in the lithosphere of this volcanic archipelago. The origin of the Bobaomby mafic rocks is compatible from a derivation from low degree partial melting of an incompatible element-enriched peridotite source (possibly located in the lowermost lithospheric mantle) rich in volatile-rich phases (pargasite, locally also phlogopite and possibly carbonates), matching the sources of other Cenozoic volcanic areas throughout Madagascar, and perhaps Comoros.

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Ancient-depleted and enriched mantle lithosphere domains in northern Madagascar: geochemical and isotopic evidence from spinel-to-plagioclase-bearing ultramafic xenoliths

Cited by 15 publications

References 74 publications

Cenozoic Dynamic Topography of Madagascar

Cenozoic Dynamic Topography of Madagascar

Petrology and geochemistry of the Tasse mantle xenoliths of the Canadian Cordillera: A record of Archean to Quaternary mantle growth, metasomatism, removal, and melting

Alkaline rocks of the Bobaomby volcanic field point to a petrogenetic link between Comoros and northern Madagascar lithosphere

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