Multi-stage evolution of the lithospheric mantle beneath the westernmost Mediterranean: Geochemical constraints from peridotite xenoliths in the eastern Betic Cordillera (SE Spain)

Marchesi, Claudio; Konc, Z.; Garrido, Carlos J.; Bosch, Delphine; Hidas, Károly; Varas-Reus, Maŕia Isabel; Acosta-Vigil, Antonio

doi:10.1016/j.lithos.2016.12.011

Cited by 13 publications

(21 citation statements)

References 74 publications

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“…Deformation pattern and seismic anisotropy signal of mantle xenoliths from the eastern Betics indicate steeply dipping foliation and subhorizontal lineations in the shallow SCLM, which are consistent with WSW tearing of the subducted south Iberian margin lithosphere along the STEP fault (Hidas et al, 2016a). Moreover, in the same volcanic field, wehrlite lithologies are interpreted as an interaction with SiO2understaturated magmas, similar to the alkali basalts that host the mantle xenoliths (Marchesi et al, 2017). The Oran volcanic field is situated on the northern margin of the African plate and its SCLM records processes related to slab edge delamination and asthenospheric mantle upwelling coupled to the rapid westward retreat of the subduction arc system along the Rif-Tell STEP fault, predating the latemost Miocene development of the Betic STEP fault in Southeastern Betics (Booth-Rea et al, 2007;Garcia-Castellanos and Villasenor, 2011;Platt et al, 2013;van Hinsbergen et al, 2014;Chertova et al, 2014a;Chertova et al, 2014b).…”

Section: Introductionsupporting

confidence: 56%

“…The only exception is sample HAM-018, which plots to the right of this field due to its low olivine Mg# (Fig. 7a), similarly to wehrlites from the eastern Betics (e.g., Marchesi et al, 2017), as well as strongly metasomatized peridotites and ultramafic cumulates worldwide (Arai, 1994).…”

Section: Mineral Major Element Compositionmentioning

confidence: 94%

“…Upwelling of hot mantle material coupled to extension potentially eroded the base of the SCLM and resulted in the formation of large amounts of SiO2-undersaturated, high-Mg# alkaline melts at the N-African margin (Duggen et al, 2005;Duggen et al, 2009;Varas-Reus et al, 2017). During influx of such melts in refractory peridotites at mantle conditions (>1000 °C and 1.0 GPa), the first reaction to take place is the dissolution of orthopyroxene and simultaneous crystallization of clinopyroxene and olivine (Shaw, 1999;Shaw et al, 2005;Lambart et al, 2012;Marchesi et al, 2017). Close to melt percolation channels, the interaction between the high-Mg# melts and the harzburgite protolith proceeds until the complete exhaustion of orthopyroxene in the rocks, forming coarse-grained wehrlites (e.g., SOU-003 wehrlite; Fig.…”

Section: Role Of the Step Fault In Melt-rock Interaction In The Shallmentioning

confidence: 99%

“…In terms of modal composition, melt-rock reaction processes that occur at shallow mantle depths result in a lithological variation trending from refractory peridotites towards lherzolites with a high clinopyroxene/orthopyroxene modal ratio, eventually forming wehrlite (e.g., Peslier et al, 2002;Parkinson et al, 2003;Ionov et al, 2005;Soustelle et al, 2009;Lambart et al, 2012;Bodinier and Godard, 2014;Varas-Reus et al, 2016;Marchesi et al, 2017). The microstructure of such olivine-and clinopyroxene-rich SCLM peridotites usually indicates syn-to post-kinematic melt-rock reactions (e.g., Tommasi et al, 2004;Tommasi et al, 2008;Morales and Tommasi, 2011;Zaffarana et al, 2014;Kourim et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Lithosphere tearing along STEP faults and synkinematic formation of lherzolite and wehrlite in the shallow subcontinental mantle

Hidas¹,

Garrido²,

Booth‐Rea³

et al. 2019

Preprint

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Abstract. Subduction-Transform Edge Propagator (STEP) faults are the locus of continual lithospheric tearing at slab edges, resulting in sharp changes in the lithospheric and crustal thickness and triggering lateral and/or near-vertical mantle flow. However, the mechanisms at the lithospheric mantle scale are still poorly understood. Here, we present the microstructural study of olivine-rich lherzolite, harzburgite and wehrlite mantle xenoliths from the Oran volcanic field (Tell Atlas, NW Algeria). This alkali volcanic field occurs along a major STEP fault responsible for the Miocene westward slab retreat in the westernmost Mediterranean. Mantle xenoliths provide a unique opportunity to investigate the microstructures in the mantle section of a STEP fault system. The microstructures of mantle xenoliths show a variable grain size ranging from coarse granular to fine-grained equigranular textures uncorrelated with modal variations. The major element composition of the mantle peridotites provides temperature estimates in a wide range (790–1165 °C) but in general, the coarse-grained and fine-grained peridotites suggest deeper and shallower provenance depth, respectively. Olivine grain size in the fine-grained peridotites depends on the size and volume fraction of the pyroxene grains, which is consistent with pinning of olivine grain growth by pyroxenes as second phase particles. In the coarse-grained peridotites, well-developed olivine crystal preferred orientation (CPO) is characterized by orthorhombic and [100]-fiber symmetries, and orthopyroxene has a coherent CPO with that of olivine, suggesting their coeval deformation by dislocation creep at high-temperature. In the fine-grained microstructures, along with the weakening of the fabric strength, olivine CPO symmetry exhibits a shift towards [010]-fiber and the [010]- and [001]-axes of orthopyroxene are generally distributed subparallel to those of olivine. These data are consistent with deformation of olivine in the presence of low amounts of melts and the precipitation of orthopyroxenes from a melt phase. The bulk CPO of clinopyroxene mimics that of orthopyroxene via a topotaxial relationship of the two pyroxenes. This observation points to a melt-related origin of most clinopyroxenes in the Oran mantle xenoliths. The textural and geochemical record of the peridotites are consistent with interaction of a refractory harzburgite protolith with a high-Mg# melt at depth (resulting in the formation of coarse-grained clinopyroxene-rich lherzolite and wehrlite), and with a low-Mg# evolved melt in the shallow subcontinental lithospheric mantle (forming fine-grained harzburgite). We propose that pervasive melt-peridotite reaction – promoted by lateral and/or near-vertical mantle flow associated with lithospheric tearing – resulted in the synkinematic crystallization of secondary lherzolite and wehrlite and played a key effect on grain size reduction during the operation of the Rif-Tell STEP fault. Melt-rock reaction and secondary formation of lherzolite and wehrlite may be widespread in other STEP fault systems worldwide.

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Section: Introductionsupporting

confidence: 56%

Section: Mineral Major Element Compositionmentioning

confidence: 94%

Section: Role Of the Step Fault In Melt-rock Interaction In The Shallmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Lithosphere tearing along STEP faults and synkinematic formation of lherzolite and wehrlite in the shallow subcontinental mantle

Hidas¹,

Garrido²,

Booth‐Rea³

et al. 2019

Preprint

Self Cite

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“…The present-day Betic-Rif slab morphology is consistent with the evolution of an initially NW-dipping subduction zone situated southeast of the Balearic Islands in the Oligocene that retreated towards the south and later to the west, after approximately 90 • clockwise rotation, during the Miocene to reach its current position beneath the Strait of Gibraltar (e.g., Royden, 1993;Lonergan and White, 1997;Rosenbaum et al, 2002;Spakman and Wortel, 2004;Chertova et al, 2014a, b;van Hinsbergen et al, 2014). Slab tearing and detachment in the southern part of the slab are associated with the rapid westward retreat of the subduction system (e.g., Roure et al, 2012;Abbassene et al, 2016;Chazot et al, 2017) that created a STEP fault parallel to the north African margin (Mauffret et al, 2004;Medaouri et al, 2014;Chertova et al, 2014a, and references therein).…”

Section: Geologic Setting and Sampling Strategymentioning

confidence: 99%

Lithosphere tearing along STEP faults and synkinematic formation of lherzolite and wehrlite in the shallow subcontinental mantle

et al. 2019

Self Cite

View full text Add to dashboard Cite

Abstract. Subduction-transform edge propagator (STEP) faults are the locus of continual lithospheric tearing at slab edges, resulting in sharp changes in the lithospheric and crustal thickness and triggering lateral and/or near-vertical mantle flow. However, the mechanisms at the lithospheric mantle scale are still poorly understood. Here, we present the microstructural study of olivine-rich lherzolite, harzburgite and wehrlite mantle xenoliths from the Oran volcanic field (Tell Atlas, northwest Algeria). This alkali volcanic field occurs along a major STEP fault responsible for the Miocene westward slab retreat in the westernmost Mediterranean. Mantle xenoliths provide a unique opportunity to investigate the microstructures in the mantle section of a STEP fault system. The microstructures of mantle xenoliths show a variable grain size ranging from coarse granular to fine-grained equigranular textures uncorrelated with lithology. The major element composition of the mantle peridotites provides temperature estimates in a wide range (790–1165 ∘C) but in general, the coarse-grained and fine-grained peridotites suggest deeper and shallower provenance depth, respectively. Olivine grain size in the fine-grained peridotites depends on the size and volume fraction of the pyroxene grains, which is consistent with pinning of olivine grain growth by pyroxenes as second-phase particles. In the coarse-grained peridotites, well-developed olivine crystal-preferred orientation (CPO) is characterized by orthorhombic and [100]-fiber symmetries, and orthopyroxene has a coherent CPO with that of olivine, suggesting their coeval deformation by dislocation creep at high temperature. In the fine-grained microstructures, along with the weakening of the fabric strength, olivine CPO symmetry exhibits a shift towards [010] fiber and the [010] and [001] axes of orthopyroxene are generally distributed subparallel to those of olivine. These data are consistent with deformation of olivine in the presence of low amounts of melts and the precipitation of orthopyroxenes from a melt phase. The bulk CPO of clinopyroxene mimics that of orthopyroxene via a topotaxial relationship of the two pyroxenes. This observation points to a melt-related origin of most clinopyroxenes in the Oran mantle xenoliths. The textural and geochemical record of the peridotites are consistent with interaction of a refractory harzburgite protolith with a high-Mg no. melt at depth (resulting in the formation of coarse-grained clinopyroxene-rich lherzolite and wehrlite) and with a low-Mg no. evolved melt in the shallow subcontinental lithospheric mantle (forming fine-grained harzburgite). We propose that pervasive melt–peridotite reaction – promoted by lateral and/or near-vertical mantle flow associated with lithospheric tearing – resulted in the synkinematic crystallization of secondary lherzolite and wehrlite and had a key effect on grain size reduction during the operation of the Tell–Rif STEP fault. Melt–rock reaction and secondary formation of lherzolite and wehrlite may be widespread in other STEP fault systems worldwide.

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Mesozoic and Cenozoic Magmatism in the Betics

Gómez-Pugnaire

Sánchez‐Vizcaíno

Fernández-Soler

et al. 2019

The Geology of Iberia: A Geodynamic Approach

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Multi-stage evolution of the lithospheric mantle beneath the westernmost Mediterranean: Geochemical constraints from peridotite xenoliths in the eastern Betic Cordillera (SE Spain)

Cited by 13 publications

References 74 publications

Lithosphere tearing along STEP faults and synkinematic formation of lherzolite and wehrlite in the shallow subcontinental mantle

Lithosphere tearing along STEP faults and synkinematic formation of lherzolite and wehrlite in the shallow subcontinental mantle

Lithosphere tearing along STEP faults and synkinematic formation of lherzolite and wehrlite in the shallow subcontinental mantle

Mesozoic and Cenozoic Magmatism in the Betics

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