Structural Petrology of the Ronda Peridotite, SW Spain: Deformation History

Wal, D. van der; Vissers, R. L. M.

doi:10.1093/petrology/37.1.23

Cited by 100 publications

(84 citation statements)

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“…In addition, field observations from different exhumed mantle rock sections, where peridotite-pyroxenite relationships are better visible than in xenoliths, support such a model (e.g. Kornprobst 1966;Bodinier et al 1987Bodinier et al , 1988Van der Wal and Vissers 1996;Tabit et al 1997).…”

Section: Grt / C1 Chonddritementioning

confidence: 93%

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Kaeser

Olker

Kalt

et al. 2008

Contrib Mineral Petrol

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Garnet-bearing and garnet-free pyroxenite xenoliths from Quaternary basanites of Marsabit, northern Kenya, were analysed for microstructures and mineral compositions (major and trace elements) to constrain the thermal and compositional evolution of the lithospheric mantle in this region. Garnet-bearing rocks are amphibolebearing websterite with *5-10 vol% orthopyroxene. Clinopyroxene is LREE-depleted and garnet has high HREE contents, in agreement with an origin as cumulates from basaltic mantle melts. Primary orthopyroxene inclusions in garnet suggest that the parental melts were orthopyroxene-saturated. Rock fabrics vary from weakly to strongly deformed. Thermobarometry indicates extensive decompression and cooling (*970-1,100°C at *2.3-2.6 GPa to *700-800°C at *0.5-1.0 GPa) during deformation, best interpreted as pyroxenite intrusion into thick Paleozoic continental lithosphere subsequently followed by continental rifting (i.e., formation of the Mesozoic Anza Graben). During continental rifting, garnet websterites were decompressed (garnet-to-spinel transition) and experienced the same P-T evolution as their host peridotites. Strongly deformed samples show compositional overlaps with cpx-rich, initially garnet-bearing lherzolite, best explained by partial re-equilibration of peridotite and pyroxenite during deformation and mechanical mingling. In contrast, garnet-free pyroxenites include undeformed, cumulate-like samples, indicating that they are younger than the garnet websterites. Major and trace element compositions of clinopyroxene and calculated equilibrium melts suggest crystallisation from alkaline basaltic melt similar to the host basanite, which suggests formation in the context of alkaline magmatism during the development of the Kenya rift.

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Section: Grt / C1 Chonddritementioning

confidence: 93%

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Kaeser

Olker

Kalt

et al. 2008

Contrib Mineral Petrol

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“…Garnet-bearing mafic rocks mainly occur in the northern part of the complex, garnet-spinel mylonites of Van der Wal and Vissers (1996) (Obata, 1980;Garrido and Bodinier, 1999;Bodinier et al, 2008) (Fig. 1).…”

Section: Geological Backgroundmentioning

confidence: 99%

“…The studied aluminous mafic rock is equivalent to Type II layer of Kornprobst et al (1990) in terms of whole-rock chemical compositions (Morishita et al, 2001(Morishita et al, , 2003. Kornprobst et al (1990) considered that a protolith of the corundum-bearing garnet pyroxenites from the Beni Bousera was originally a Van der Wal and Vissers (1996). Thick lines (partly broken line) are lithological boundaries by Obata (1980 Morishita et al (2001Morishita et al ( , 2003.…”

Section: Geological Backgroundmentioning

confidence: 99%

“…Serpentinized peridotite layer, <2 mm in thickness, is in contact with sublayer (f) whereas the relationships between peridotite and the other side of the mafic layer are not clear. Symplectitic mineral aggregate of orthopyroxene, clinopyroxene and spinel observed in the peridotite layer and interpreted to be after garnet (Obata, 1980;Van der Wal and Vissers, 1996). Modal reactions between the peridotite layer and the sublyaer (f), e.g., the formation of pyroxenite, are not observed.…”

Section: Sample Descriptionsmentioning

confidence: 99%

“…Geochemical gradients in the mafic rock towards to the peridotite layer combined with no modal reactions at the boundary between the peridotite layer and the mafic rock suggest that restricted area of the mafic rock might be chemically modified by the interaction with the peridotite layer. It is, however, noted that the studied sample was probably thinned by deformation since it was collected from the garnet-spinel mylonites of Van der Wal and Vissers (1996). We, therefore, analyzed minerals in the center of each sublayer, except sublayer (f) as described later.…”

Section: Chemical Compositions Of Garnet and Clinopyroxenementioning

confidence: 99%

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Constraints on the evolutionary history of aluminous mafic rocks in the Ronda peridotite massif (Spain) from trace-element compositions of clinopyroxene and garnet

et al. 2009

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Multiple trace-element compositions of clinopyroxene and garnet in aluminous mafic layers (±corundum and/or sapphirine) alternating with peridotites from the Ronda massif, Spain, were determined by an ArF 193 nm excimer laser system coupled with a quadrupole ICP-MS. The studied aluminous mafic rock is divided into several sublayers based on the modal mineral variations. Trace-element compositions of minerals vary between sublayers. Primitive mantle-normalized trace-element distribution patterns have more significant positive Eu anomaly for both garnet and clinopyroxene in the corundum-bearing sublayers than for those in the other sublayers whereas corundum-bearing sublayers contain more abundant secondary plagioclase than corundum-free sublayers. These geochemical signatures of the corundum-bearing sublayers intercalated with corundum-free sublayers were acquired as plagioclase-rich portions of gabbroic layered sequence originated at the lower crustal to the uppermost mantle sections rather than selective accumulation of metamorphic plagioclase due to deformation during the late stage of exhumation of the massif. Partition coefficients of trace elements between clinopyroxene and garnet show systematic variations with respect to major element composition, indicating local attainment of chemical equilibrium. The trace element compositions of clinopyroxene and garnet were equilibrated with secondary metamorphic plagioclase, i.e., at granulite-facies conditions, because plagioclase is required for the geochemical balance in Sr and Eu contents of the whole-rock trace element compositions. Positive Eu anomaly of clinopyroxene (±garnet) is also found in mantle-derived aluminous eclogitic xenoliths and eclogitic mineral inclusions in diamond captured in kimberlites, and is thus a useful indicator to explore recycled crustal components in the mantle.

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Origin and consequences of western Mediterranean subduction, rollback, and slab segmentation

2014

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The western Mediterranean recorded subduction rollback, slab segmentation and separation.Here we address the questions of what caused Oligocene rollback initiation, and how its subsequent evolution split up an originally coherent fore arc into circum-southwest Mediterranean segments. We kinematically reconstruct western Mediterranean geology from subduction initiation to present, using Atlantic plate reconstructions as boundary condition. We test possible reconstructions against remnants of subducted lithosphere imaged by seismic tomography. Transform motion between Africa and Iberia (including the Baleares) between~120 and 85 Ma was followed by up to 150 km convergence until 30 Ma. Subduction likely initiated along the transform fault that accommodated pre-85 Ma translation. By thẽ 30 Ma inception of rollback, up to 150 km of convergence had formed a small slab below the Baleares. Iberia was disconnected from Sardinia/Calabria through the North Balearic Transform Zone (NBTZ). Subduction below Sardinia/Calabria was slightly faster than below the Baleares, the difference being accommodated in the Pyrenees. A moving triple junction at the trench-NBTZ intersection formed a subduction transform edge propagator fault between the Baleares and Calabria slab segments. Calabria rolled back eastward, whereas the Baleares slab underwent radial (SW-S-SE) rollback. After Kabylides-Africa collision, the western slab segment retreated toward Gibraltar, here reconstructed as the maximum rollback end-member model, and a Kabylides slab detached from Africa. Opening of a slab window below the NBTZ allowed asthenospheric rise to the base of the fore arc creating high-temperature metamorphism. Western Mediterranean rollback commenced only after sufficient slab-pull was created from 100 to 150 km of slow, forced subduction before~30 Ma.

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Structural Petrology of the Ronda Peridotite, SW Spain: Deformation History

Cited by 100 publications

References 0 publications

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Pyroxenite xenoliths from Marsabit (Northern Kenya): evidence for different magmatic events in the lithospheric mantle and interaction between peridotite and pyroxenite

Constraints on the evolutionary history of aluminous mafic rocks in the Ronda peridotite massif (Spain) from trace-element compositions of clinopyroxene and garnet

Origin and consequences of western Mediterranean subduction, rollback, and slab segmentation

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