Petrology, Trace Element and Sr, Nd, Hf Isotope Geochemistry of the North Lanzo Peridotite Massif (Western Alps, Italy)

Guarnieri, Luisa; Nakamura, Eizo; Piccardo, Giuseppe; Sakaguchi, Chie; Shimizu, Nobumichi; Vannucci, R.; Zanetti, A.

doi:10.1093/petrology/egs049

Cited by 33 publications

(20 citation statements)

References 106 publications

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“…Snow et al (2000) studied Os isotopic and highly siderophile element (HSE) concentration characteristics in some samples of the Suvero peridotites, producing results consistent with a Proterozoic melting age. Most of the North Lanzo peridotites (Bodinier et al 1991;Guarnieri et al 2012) with 147 Sm/ 144 Nd in excess of 0.23-0.25 (i.e. the typical values of a DM source) and highly depleted isotopic compositions have calculated model ages in the range 2.1 Ga -800 Ma, confirming the 2.5-0.8 Ga time span reported in previous studies.…”

Section: Structural and Magmatic Evolution Of The Ligurian Tethys Frosupporting

confidence: 85%

“…The onset of passive continental extension in the Europe -Adria system and subsequent asthenosphere decompression partial melting are constrained by: (4) Mesozoic (Triassic -Jurassic) extension that was already underway during Triassic times as evidenced by the geochronological data obtained from extensional shear zones within the External Ligurides peridotites (220 + 13 and 186.0 + 1.8 Ma Lu -Hf isochrons on pyroxenites: Montanini et al 2006) and from the Malenco peridotites (225 Ma amphibole 40 Ar/ 39 Ar ages: Müntener & Hermann 2001); (5) Triassic-Liassic magmatism with OIB geochemical signatures that were probably inherited during the course of extension or start of exhumation (e.g. Guarnieri et al 2012); and (6) local Middle Jurassic melt impregnation at shallow, plagioclase-facies, lithospheric levels (e.g. Guarnieri et al 2012).…”

Section: Pre-rifting Events Recorded In Subcontinental Lithosphere Ofmentioning

confidence: 96%

“…These ages have been regarded as minimum ages of isolation from the convective asthenosphere and accretion to the lithosphere. It is also worth pointing out that at North Lanzo some peridotites show alkaline OIB (ocean island basalt) signatures and in a 176 Hf/ 177 Hf v. 176 Lu/ 177 Hf plot are aligned along an errorchron with a slope corresponding to an age of 259 (+25) Ma (Guarnieri et al 2012). This approximately 260 Ma errorchron has been interpreted as a record of interaction and rejuvenation of the North Lanzo mantle by relatively young alkaline melts that percolated into the mantle lithosphere before or during the onset of passive extension and exhumation (Guarnieri et al 2012).…”

Section: Structural and Magmatic Evolution Of The Ligurian Tethys Fromentioning

confidence: 99%

“…It is also worth pointing out that at North Lanzo some peridotites show alkaline OIB (ocean island basalt) signatures and in a 176 Hf/ 177 Hf v. 176 Lu/ 177 Hf plot are aligned along an errorchron with a slope corresponding to an age of 259 (+25) Ma (Guarnieri et al 2012). This approximately 260 Ma errorchron has been interpreted as a record of interaction and rejuvenation of the North Lanzo mantle by relatively young alkaline melts that percolated into the mantle lithosphere before or during the onset of passive extension and exhumation (Guarnieri et al 2012). If this is the case, then the early formation and percolation of alkaline melts through the mantle lithosphere could indicate that the onset of lithosphere extension occurred during the Middle-Upper Permian.…”

Section: Structural and Magmatic Evolution Of The Ligurian Tethys Fromentioning

confidence: 99%

“…Guarnieri et al 2012); and (6) local Middle Jurassic melt impregnation at shallow, plagioclase-facies, lithospheric levels (e.g. Guarnieri et al 2012).…”

Section: Pre-rifting Events Recorded In Subcontinental Lithosphere Ofmentioning

confidence: 99%

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Passive rifting and continental splitting in the Jurassic Ligurian Tethys: the mantle perspective

Piccardo¹

2014

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Based on present knowledge of mantle peridotites from the Ligurian Tethys ophiolites, this paper presents new ideas and a new model for passive rifting to ocean spreading in the slowultraslow rifting Europe-Adria realm. Relevant points include: (i) the positive feedback between deformation and melt percolation during passive magmatic rifting; (ii) the positive feedback between natural evidence and experimental data on the behaviour of the mantle lithosphere during passive rifting; (iii) the significance of hidden magmatism and the associated melt thermal advection; (iv) the role of the wedge-shaped weakened and softened axial zone; and (v) the evidence of a transition from passive to active rifting in the Ligurian Tethys.Passive rifting induced passive asthenospheric upwelling and the onset of partial melting. Fractional melts migrated through the mantle lithosphere and stagnated at shallow levels (the hidden magmatism). Melt thermal advection heated the mantle lithosphere to temperatures (T ) of ≥1200 8C and formed a wedge-shaped axial zone of rheological softened/weakened mantle peridotites that served as the future locus of continental break-up. The hotter/deeper asthenosphere ascended within this axial zone, underwent partial melting and formed aggregated mid-ocean ridge basalts (MORBs) that migrated within dunite channels to form olivine gabbro intrusions and basaltic lava flows. Rifting evolved from passive to active, and the actively upwelling asthenosphere established a ridge-type system and thermal regime.

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Section: Structural and Magmatic Evolution Of The Ligurian Tethys Frosupporting

confidence: 85%

Section: Pre-rifting Events Recorded In Subcontinental Lithosphere Ofmentioning

confidence: 96%

Section: Structural and Magmatic Evolution Of The Ligurian Tethys Fromentioning

confidence: 99%

Section: Structural and Magmatic Evolution Of The Ligurian Tethys Fromentioning

confidence: 99%

“…Guarnieri et al 2012); and (6) local Middle Jurassic melt impregnation at shallow, plagioclase-facies, lithospheric levels (e.g. Guarnieri et al 2012).…”

Section: Pre-rifting Events Recorded In Subcontinental Lithosphere Ofmentioning

confidence: 99%

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Passive rifting and continental splitting in the Jurassic Ligurian Tethys: the mantle perspective

Piccardo¹

2014

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Evidence for ancient fractional melting, cryptic refertilization and rapid exhumation of Tethyan mantle (Civrari Ophiolite, NW Italy)

McCarthy

Müntener

2019

Contrib Mineral Petrol

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Western Tethyan peridotites exposed in the European Alps show limited amounts of partial melting and mostly fertile compositions. Here we investigate the Civrari Ophiolite (northwestern Italy), which is composed of depleted spinel-harzburgites and serpentinites associated with MOR-type gabbros and basalts. The ultramafic rocks are unique amongst western Tethyan peridotites, showing homogeneous residual compositions after ~ 15% near-fractional melting, lack of pervasive melt percolation and mineral compositions that indicate high-temperature equilibration ≥ 1200 °C. Clinopyroxene chemistry records some of the lowest abundances of Na 2 O, Ce, and Zr/Hf amongst abyssal peridotites worldwide, suggesting that most abyssal peridotites have been affected by variable degrees of melt retention upon melting or cryptic melt percolation. Locally, cryptic MORB-like melt migration in Civrari peridotites produced orthopyroxene + plagioclase intergrowth around reacted clinopyroxene. These clinopyroxene preserve micron-scale chemical zoning indicating rapid cooling after melt crystallization. 143 Nd/ 144 Nd isotopic data indicate that Civrari mantle rocks, gabbros, and basalts are not in isotopic equilibrium. Civrari spinel-peridotites represent a highly radiogenic endmember amongst Western Tethys depleted spinel-peridotites, which together form a partial melting errochron of 273 Ma ± 24 Ma. Ancient near-fractional melting and cryptic melt–rock reaction cause variations in radiogenic εNd and εHf, leading to isotopic heterogeneity of Western Tethys mantle rocks. Such inherited signatures in mantle rocks are most likely to be preserved along (ultra-)slow-spreading systems and ocean–continent transition zones. Electronic supplementary material The online version of this article (10.1007/s00410-019-1603-5) contains supplementary material, which is available to authorized users.

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A 400 Ma-long Nd-Hf isotopic evolution of melt-modified garnet-pyroxenites in an ancient subcontinental lithosphere (Lanzo North ophiolite, Western Alps)

Sanfilippo

Borghini

Guarnieri³

et al. 2022

Chemical Geology

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Petrology, Trace Element and Sr, Nd, Hf Isotope Geochemistry of the North Lanzo Peridotite Massif (Western Alps, Italy)

Cited by 33 publications

References 106 publications

Passive rifting and continental splitting in the Jurassic Ligurian Tethys: the mantle perspective

Passive rifting and continental splitting in the Jurassic Ligurian Tethys: the mantle perspective

Evidence for ancient fractional melting, cryptic refertilization and rapid exhumation of Tethyan mantle (Civrari Ophiolite, NW Italy)

A 400 Ma-long Nd-Hf isotopic evolution of melt-modified garnet-pyroxenites in an ancient subcontinental lithosphere (Lanzo North ophiolite, Western Alps)

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