The Finero phlogopite-peridotite massif: an example of subduction-related metasomatism

Zanetti, Alberto; Mazzucchelli, Maurizio; Rivalenti, Giorgio; Vannucci, R.

doi:10.1007/s004100050472

Cited by 259 publications

(156 citation statements)

References 38 publications

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“…The metasomatized mantle massif, named the PhlogopitePeridotite unit (Ph-Pd; unit names and acronyms according to Siena & Coltorti [3]) by Cawthorn [1], is mainly composed of phlogopite-bearing amphibole harzburgite that contains secondary orthopyroxene, amphibole, phlogopite and clinopyroxene that segregated from metasomatizing melts/fluids. This indicates a pervasive recrystallization at mantle conditions [4,7]. The Finero Mafic Complex is characterized by a great abundance of amphibole (i.e.…”

Section: Introductionmentioning

confidence: 99%

“…It consists of mafic, and subordinately ultramafic, rocks (comprising the following units: the Lay-ered Internal Zone unit, the Amphibole-Peridotite unit and the External Gabbro unit) surrounding a completely metasomatized mantle massif ( Figure 1; [1][2][3][4][5][6][7][8][9] and references therein). The metasomatized mantle massif, named the PhlogopitePeridotite unit (Ph-Pd; unit names and acronyms according to Siena & Coltorti [3]) by Cawthorn [1], is mainly composed of phlogopite-bearing amphibole harzburgite that contains secondary orthopyroxene, amphibole, phlogopite and clinopyroxene that segregated from metasomatizing melts/fluids.…”

Section: Introductionmentioning

confidence: 99%

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Occurrence of phlogopite in the Finero Mafic layered complex

Giovanardi¹,

Mazzucchelli²,

Zanetti

et al. 2014

Open Geosciences

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Phlogopite-bearing lithologies are the main constituent of the Phlogopite-Peridotite unit of the Finero sequence and the result of pervasive migration of metasomatizing melts/fluids. Conversely, the presence of phlogopite within the associated Finero Mafic Complex, a mafic-ultramafic pluton intruded into the metamorphic basement of the Adria plate, is mentioned in literature as rare. Recent detailed fieldwork has evidenced the presence of two distinct phlogopite-rich ultramafic lithologies within the Amphibole-Peridotite unit of the Finero Mafic Complex, where phlogopite is always associated with amphibole. Field and petrographic features of these occurrences, as well as major-and trace-element mineral chemistry, are here presented to i) place constraints on the nature of the parent melt from which they have been generated and ii) to address their relationship with the other lithologies of the Finero Complex. We find that these rocks were formed by late melt migrations along shear zones under high-T conditions. The geochemical affinity of these lithologies is different to the tholeiitic-transitional affinity reported in literature for the Finero Mafic Complex. The enrichment in LREE, Th, U and Sr of the associated amphibole possibly suggests that these phlogopite-bearing lithologies are genetically related to the metasomatic events that have affected the Finero mantle massif.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Occurrence of phlogopite in the Finero Mafic layered complex

Giovanardi¹,

Mazzucchelli²,

Zanetti

et al. 2014

Open Geosciences

Self Cite

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“…This often obliterates the 'primary' composition of pyroxenite (Bodinier et al 1987;Rivalenti et al 1995;Garrido and Bodinier 1999;Zanetti et al 1999;Litasov et al 2000;Liu et al 2005). In the following, we will present a detailed study of two groups of pyroxenite xenoliths from Quaternary basanitic maars, erupted on the Marsabit shield volcano in the context of the Kenya rift magmatism (e.g., Henjes-Kunst and Altherr 1992).…”

Section: Introductionmentioning

confidence: 99%

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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“…Metasomatic rocks can also affect the composition of slab fluids as they may contain mineral assemblages that are able to transport water to great depths in the subduction zone (e.g., Schmidt and Poli, 1998). Several studies have looked at the metasomatic overprint by slab-derived fluids/melts in the mantle wedge above the subducting slab (e.g., Halama et al, 2009;Paquin et al, 2004;Scambelluri et al, 2006;Zanetti et al, 1999), but the metasomatic effects within the lithospheric slab itself have been relatively little studied (e.g., Beinlich et al, 2010;Marschall et al, 2009;Molina et al, 2002). Fluids are important in catalyzing prograde metamorphic transformations, for instance during eclogitization processes (e.g., Austrheim, 1987;Putnis and John, 2010).…”

Section: Introductionmentioning

confidence: 99%

A stable (Li, O) and radiogenic (Sr, Nd) isotope perspective on metasomatic processes in a subducting slab

et al. 2011

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Two distinct types of eclogites from the Raspas Complex (Ecuador), which can be distinguished based on petrography and trace element geochemistry, were analyzed for their stable (Li, O) and radiogenic (Sr, Nd) isotope signature to constrain metasomatic changes due to fluid-overprinting in metabasaltic rocks at high-pressure conditions and to identify fluid sources. MORB-type eclogites are characterized by a relative LREE depletion similar to MORB. High-pressure (HP) minerals from this type of eclogite have highly variable oxygen isotope compositions (garnet: +4.1 to +9.

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The Finero phlogopite-peridotite massif: an example of subduction-related metasomatism

Cited by 259 publications

References 38 publications

Occurrence of phlogopite in the Finero Mafic layered complex

Occurrence of phlogopite in the Finero Mafic layered complex

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

A stable (Li, O) and radiogenic (Sr, Nd) isotope perspective on metasomatic processes in a subducting slab

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