Major and trace elements of abyssal peridotites: evidence for melt refertilization beneath the ultraslow-spreading Southwest Indian Ridge (53° E segment)

Chen, Ling; Chu, Fong‐Fong; Zhu, Jinghan; Dong, Yanhui; X, Yu; Li, Zhenggang; Tang, Leiwen

doi:10.1080/00206814.2015.1029014

Cited by 23 publications

(18 citation statements)

References 85 publications

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“…The MREE concentrations are similar or higher than the LREE ones, which is characteristic of stealth metasomatism usually indicating interactions with relatively large volumes of melt or fluids [ O'Reilly and Griffin , ]. This is supported by the occurrence of band‐like small‐size Cpx aggregates in sample 21V‐S16‐TVG4 (Figure h) and other peridotites from the same sampling location; they are interpreted as microchannels [ Chen et al ., ]. We infer that such process probably occurs at the base of the lithosphere below the ridge axis where melts aggregate and percolate through the thermal boundary layer (TBL).…”

Section: Discussionmentioning

confidence: 99%

Origins of water content variations in the suboceanic upper mantle: Insight from Southwest Indian Ridge abyssal peridotites

Li¹,

Soustelle

Zhang

et al. 2017

Geochem Geophys Geosyst

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To investigate the origin of heterogeneous water distribution in the suboceanic lithospheric mantle, we performed a detailed petrological and geochemical analysis of abyssal peridotites collected from two localities (53°E and 63.5°E) on the Southwest Indian Ridge. These serpentinized peridotites display primary olivine‐orthopyroxene‐clinopyroxene‐spinel assemblage and record equilibrium temperature of 1150–1200°C and around 1000°C for the 53°E and 63.5°E locations, respectively. The rocks were thus equilibrated in the spinel stability field prior to their exhumation to the seafloor. Our FTIR analyses show variable water contents in orthopyroxene ranging from 24 to 262 wt ppm H2O. Orthopyroxene in the 63.5°E peridotites is characterized by homogeneous and high water content (>200 ppm), whereas orthopyroxene in the 53°E peridotites displays a wider range of water contents (24–246 ppm). We first demonstrate that differences in equilibrium conditions (i.e., pressure and temperature) and mineral chemistry and serpentinization cannot explain the water content variations. Melting modeling show that a fractional melting in both garnet and spinel stability fields is needed to explain the MREE and HREE concentrations in clinopyroxene. Enrichment in LREE, high water contents, and high H2O/Ce, however, require a postmelting rehydration event such as metasomatism. Based on petrographic evidence and investigation of chemical heterogeneities at segment/dredge scale, we suggest that this event involves a metasomatic agent enriched in water and incompatible elements. We infer that the small‐scale heterogeneities in water and trace elements may result either from successive infiltration of various amounts of melt/fluids as described in the formation of oceanic core complex or from spatial heterogeneities of melt infiltration as observed in peridotite massifs.

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Section: Discussionmentioning

confidence: 99%

Origins of water content variations in the suboceanic upper mantle: Insight from Southwest Indian Ridge abyssal peridotites

Li¹,

Soustelle

Zhang

et al. 2017

Geochem Geophys Geosyst

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“…The peridotites also have positive anomalies for Zr and Sr relative to their neighboring elements. The enriched Rb, Sr, Ba and Zr show systematic variations with serpentinization, which could be attributed to the addition from seawater (Chen et al, 2015). The Dragon Bone peridotites also have a wide range of heavy REE abundances (< 0.3 to >1.0 x chondrite), and an even more extreme range for light REE (e.g., La = 0.02 to 0.45 x chondrite), and are significantly lower than the depleted MORB mantle (DMM) of Salters and Stracke (2004) (Fig.…”

Section: Peridotite Trace Elementsmentioning

confidence: 97%

Melt extraction and mantle source at a Southwest Indian Ridge Dragon Bone amagmatic segment on the Marion Rise

Gao

Dick

Liu

et al. 2016

Lithos

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This paper works on the trace and major element compositions of spatially associated basalts and peridotites from the Dragon Bone amagmatic ridge segment at the eastern flank of the Marion Platform on the ultraslow spreading Southwest Indian Ridge. The rare earth element compositions of basalts do not match the pre-alteration Dragon Bone peridotite compositions, but can be modelled by about 5 to 10% non-modal batch equilibrium melting from a DMM source. The Dragon Bone peridotites are clinopyroxene-poor harzburgite with average spinel Cr# ~27.7. The spinel Cr# indicates a moderate degree of melting. However, CaO and Al 2 O 3 of the peridotites are lower than other abyssal peridotites at the same Mg# and extent of melting. This requires a pyroxene-poor initial mantle source composition compared to either hypothetical primitive upper mantle or depleted MORB mantle sources. We suggest a hydrous melting of the initial Dragon Bone mantle source, as wet melting depletes pyroxene faster than dry. According to the rare earth element patterns, the Dragon Bone peridotites are divided into two groups. Heavy REE in Group 1 are extremely fractionated from middle REE, which can be modelled by ~7% fractional melting in the garnet stability field and another ~12.5 to 13.5% in the spinel stability field from depleted and primitive upper mantle sources, respectively. Heavy REE in Group 2 are slightly fractionated from middle REE, which can be modelled by ~15 to 20% fractional melting in the spinel stability field from a depleted mantle source. Both Groups show similar melting degree to other abyssal peridotites. If all the melt extraction occurred at the middle oceanic ridge where the peridotites were dredged, a normal ~6km thick oceanic crust is expected at the Dragon Bone segment. However, the Dragon Bone peridotites are exposed in an amagmatic ridge segment where only scattered pillow basalts lie on a partially serpentinized mantle pavement. Thus their depletion requires an earlier melting occurred at other place. Considering the hydrous melting of the initial Dragon Bone mantle source, we suggest the earlier melting event occurred in an arc terrain, prior to or during the closure of the Mozambique Ocean in the Neproterozoic, and the subsequent assembly of Gondwana. Then, the Al 2 O 3

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“…comprising an ultramafic core and more evolved mafic shells (Abdallah, Ali, & Obeid, 2018;Dong et al, 2017;Eyuboglu et al, 2010;Habtoor, Ahmed, & Harbi, 2016;Tseng et al, 2009;L. Yuan, Zhang, Yang, Lu, & Chen, 2017) The ultramafic rocks considered as depleted residues of mantle melting are characterized by chondrite-normalized REE patterns with prominent LREE depletion and flat or enriched HREE (Chen et al, 2015). However, in contrast to this, some samples of the serpentinized dunites, dunites, and pyroxenite in our study show mild LREE enrichment over MREE and HREE ( Figure 6).…”

Section: Zircon Lu-hf Isotopesmentioning

confidence: 52%

“…The ultramafic rocks considered as depleted residues of mantle melting are characterized by chondrite‐normalized REE patterns with prominent LREE depletion and flat or enriched HREE (Chen et al, ). However, in contrast to this, some samples of the serpentinized dunites, dunites, and pyroxenite in our study show mild LREE enrichment over MREE and HREE (Figure ).…”

Section: Discussionmentioning

confidence: 99%

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Evolution of a Mesoarchean suprasubduction zone mantle wedge in the Dharwar Craton, southern India: Evidence from petrology, geochemistry, zircon U–Pb geochronology, and Lu–Hf isotopes

et al. 2019

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Petrological, geochemical, and zircon U–Pb geochronological features of Archean ultramafic–mafic complexes formed in subduction‐related settings provide significant insights into mantle source and geodynamic processes associated with subduction–accretion‐collision events in the early Earth. Here, we investigate a suite of serpentinized dunite, dunite, pyroxenite, and clinopyroxenite from an ultramafic complex along the collisional suture between the Western Dharwar Craton (WDC) and the Central Dharwar Craton (CDC) in southern India. We present petrology, mineral chemistry, zircon U–Pb geochronology, rare earth element (REE), Lu–Hf isotopes, and whole‐rock geochemistry including major, trace element, and platinum‐group element (PGE) data with a view to investigate the magmatic and metasomatic processes in the subduction zone. Mineral chemistry data from chromite associated with the serpentinised ultramafic rocks show distinct characteristics of arc‐related melt. Zircon U–Pb data from the ultramafic suite define different age populations, with the oldest ages at 2.9 Ga, and the dominant age population showing a range of 2.8–2.6 Ga. The early Paleoproterozoic (ca. 2.4 Ga) metamorphic age is considered to mark the timing of collision of the two WDC and CDC. Zircon REE patterns suggest the involvement continental crust components in the magma source. Zircon Lu–Hf analysis yields both positive and negative εHf(t) values from −3.9 to 1.5 with Hf‐depleted model ages (TDM) of 3,041–3,366 Ma for serpentinised dunite and −0.2–2.0 and 2,833–2,995 Ma for pyroxenite, suggesting that the magma was sourced from depleted mantle and was contaminated with the ancient continental crust. Geochemical data show low MgO/SiO2 values and elevated Al2O3/TiO2 ratios, implying subduction‐related setting. The serpentinized dunites and dunites show mild LREE enrichment over HREE, with relatively higher abundance of LILE (Ba, Sr) and depletion in HFSE (Nb, Zr), suggesting fluid–rock interaction, melt impregnation, and refertilization processes. The PGE data suggest olivine, chromite, and sulphide fractionations associated with subduction processes. Our study on the Mesoarchean to Neoarchean ultramafic complex provides important insights to reconstruct the history of the crust–mantle interaction in an Archean suprasubduction zone mantle wedge.

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Major and trace elements of abyssal peridotites: evidence for melt refertilization beneath the ultraslow-spreading Southwest Indian Ridge (53° E segment)

Cited by 23 publications

References 85 publications

Origins of water content variations in the suboceanic upper mantle: Insight from Southwest Indian Ridge abyssal peridotites

Origins of water content variations in the suboceanic upper mantle: Insight from Southwest Indian Ridge abyssal peridotites

Melt extraction and mantle source at a Southwest Indian Ridge Dragon Bone amagmatic segment on the Marion Rise

Evolution of a Mesoarchean suprasubduction zone mantle wedge in the Dharwar Craton, southern India: Evidence from petrology, geochemistry, zircon U–Pb geochronology, and Lu–Hf isotopes

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