High‐Temperature Strain Localization and the Nucleation of Oceanic Core Complexes (16.5°N, Mid‐Atlantic Ridge)

Casini, Leonardo; Maino, M.; Sanfilippo, Alessio; Ildefonse, Benoı̂t; Dick, H. J.

doi:10.1029/2021jb022215

Cited by 10 publications

(3 citation statements)

References 73 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, deformation processes might localize transient but significant thermal perturbations in narrow mylonitic/cataclastic shear zones. Long-term frictional-viscous deformation, in fact, accounts for moderate heating that results into localized thermal anomalies up to 150 C (Burg & Gerya, 2005;Casini et al, 2021;Casini & Maino, 2018;Maino et al, 2015Maino et al, , 2020. However, due to the difficulty to trace the shear heating signature and fluid pathways in high-grade rocks, further investigations are required to test the applicability of this mechanism.…”

Section: Heat Sources For M2mentioning

confidence: 99%

HTLP metamorphism and fluid‐fluxed melting during multistage anatexis of continental crust (N Sardinia, Italy)

Casini

Maino

Langone

et al. 2022

Journal Metamorphic Geology

Self Cite

View full text Add to dashboard Cite

The Variscan high‐grade metamorphic basement of northern Sardinia and southern Corsica record lower Carboniferous anatexis related to post‐collisional decompression of the orogen. Migmatites exposed in the Punta Bianca locality (Italy) consist of quartz + biotite + plagioclase + K‐feldspar orthogneisses, garnet and cordierite‐bearing diatexite and metatexites, derived from metasediments. Field evidence, petrographic observations, ELA‐ICP‐MS zircon and monazite dating and pseudosection modelling suggest that anatexis was apparently episodic involving two main stages of partial melting. Using pseudosection modelling, we infer that the first stage of partial melting is in the upper amphibolite facies (~0.45 GPa at ~740°C). Cordierite overgrowths replacing sillimanite, combined with the composition of plagioclase and K‐feldspar, suggest decompression followed cooling below the solidus at low pressures of ~0.3 GPa. The age of the first anatectic event is not precisely constrained because of extensive resetting of the isotopic systems during the second melting stage, yet few zircons preserve a lower Carboniferous age which is consistent with the regional dataset. This lower Carboniferous migmatitic fabric is offset by a network of pseudotachylyte‐bearing faults suggestive of cooling to greenschist facies conditions. Garnet/cordierite‐bearing diatexites incorporate fragments of pseudotachylite‐bearing orthogneiss and metatexites. Pseudosection modelling indicates nearly isobaric re‐heating up to ~750°C, followed by further cooling below the solidus. The inferred P–T path is consistent with decompression and cooling of the Variscan crust through post‐collisional extension and collapse of the thickened orogenic crust, followed by nearly isobaric re‐heating at low pressures (~0.3 GPa) yielding to a second melting stage under LP‐HT conditions. U/Th‐Pb monazite ages for diatexite migmatites indicate an upper bound of 310–316 Ma for the second melting stage, suggesting that the second melting stage is coincident with the regional phase of crustal shearing. The cause of the high geothermal gradient required for re‐heating during the second melting stage is unknown but likely requires some heat source that was probably related to dissipation of mechanical work within crustal‐scale shear zones. According to this interpretation, some upper Carboniferous peraluminous granite precursors of the Corsica–Sardinia Batholith could be the outcome rather than the cause of the late‐Variscan high‐T metamorphism.

show abstract

Section: Heat Sources For M2mentioning

confidence: 99%

HTLP metamorphism and fluid‐fluxed melting during multistage anatexis of continental crust (N Sardinia, Italy)

Casini

Maino

Langone

et al. 2022

Journal Metamorphic Geology

Self Cite

View full text Add to dashboard Cite

show abstract

“…Continuous dynamic recrystallization and grain-size reduction created higher porosity pathways for melt percolation (Mehl & Hirth, 2008;Taufner et al, 2020), in turn leading to significant local rheological weakening associated with enhanced melt ingress along grain boundaries. The presence of melt would then favour strain localization (Sanfilippo et al, 2019;Gardner et al, 2020;Casini et al, 2021).…”

Section: Crystal Plastic Deformation In Presence Of Melt: Interstitia...mentioning

confidence: 99%

Brown Amphibole as Tracer of Tectono-Magmatic Evolution of the Atlantis Bank Oceanic Core Complex (IODP Hole U1473A)

Ferrando

Tribuzio

Lissenberg

et al. 2022

Journal of Petrology

View full text Add to dashboard Cite

Brown amphibole is a minor but common mineral component in lower oceanic crust. It is generally interpreted as products of migrating SiO2 and H2O-rich fluids or melts, which can be either residual melts from advanced magmatic differentiation of Mid-Ocean Ridge Basalt (MORB), or hydrothermal fluids including a seawater component. Within the lower oceanic crust exhumed at the Atlantis Bank Oceanic Core Complex (OCC), along the ultraslow Southwest Indian Ridge, brown amphibole is ubiquitous in all lithologies from olivine- to oxide-gabbros and diorites, including both undeformed and plastically deformed varieties. We here show the results of a systematic petrological study conceived to unravel the nature of the H2O-rich component recorded in brown amphiboles and document: (i) the evolution of migrating melts during the magmatic stage and (ii) different extents of melt-bearing deformation events recorded throughout the entire crustal transect. The low Cl contents and the light over heavy Rare Earth Elements (LREE/HREE) ratios and high Ti contents in brown amphiboles, indicate they crystallized from melts with a magmatic hydrous component. Consistently, their δ18O values are in equilibrium with MORB composition, except for diorite amphiboles that possibly record the local assimilation of altered minerals. In undeformed olivine gabbros, interstitial pargasite crystallized at hypersolidus conditions (~1000°C) from the melt residual after late stages of MORB differentiation. We speculate that before the olivine gabbro crystal mush reached fully solid state, some aliquots of residual melts were extracted and accumulated within discrete intervals. There, ferrobasaltic melts differentiated through the early crystallization of Fe-Ti oxides and clinopyroxene as liquidus phases, ultimately forming the oxide gabbros. This process promoted rapid Si enrichment and depletion in Fe, Ti, V in the residual melt, later extracted to form the crosscutting diorite veins. The mylonitic olivine gabbros record high-temperature plastic deformation (~900°C ± 50°C) under hypersolidus conditions, involving melts residual from previous crystallization of the gabbroic rock. Further solid-state plastic deformation led to substantial grain-size reduction and, consequently, to an increase in porosity. This created pathways for subsequent melt focussing, which likely represent late-stage differentiated melts migrating throughout the lower crustal section. This study shows that brown amphibole in the Atlantis Bank lower oceanic crust is the crystallization product of melts residual from advanced magmatic differentiation, which are also locally involved in the plastic deformation events during crustal accretion.

show abstract

“…Moreover, for comparison, it is important to include papers on oceanic crust formed in other tectonic settings. Collectively, this focus on the origin and evolution of oceanic crust and the underlying, uppermost mantle accounts for 23 of the papers in this Special Issue (Allard et al, 2021;Belgrano et al, 2021;Boulanger et al, 2021;Carbotte et al, 2021;Carter et al, 2022;Casini et al, 2021;Crotteau et al, 2021;Ferrando et al, 2021;France et al, 2021;Garbe-Schönberg et al, 2022;Grambling et al, 2022;Greenberger et al, 2021;Hatakeyama et al, 2021;Klaessens et al, 2021;Koepke et al, 2022;Kourim et al, 2022;Mock, Neave, et al, 2021;Müller et al, 2022;VanTongeren et al, 2021;Weber et al, 2021;Xu et al, 2021;Zhang et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Preface: Special Issue on Ophiolites and Oceanic Lithosphere

et al. 2023

View full text Add to dashboard Cite

With this Preface, we provide background information, a scientific overview of topics, and an annotated bibliography of the 63 papers published in the Journal of Geophysical Research (JGR) Special Issue on “Ophiolites and Oceanic Lithosphere, with a Focus on the Samail Ophiolite,” collected online at https://agupubs.onlinelibrary.wiley.com/doi/toc/10.1002/(ISSN)2169-9356.SAMAIL1. Topics covered in the Special Issue include formation and alteration of igneous ocean crust at submarine spreading centers, subduction zone mass transfer at the leading edge of the mantle wedge, the tectonic emplacement and evolution of ophiolites, processes of alteration and weathering of tectonically exhumed mantle peridotite, and the subsurface biosphere in the peridotite weathering environment. The bibliography, in the form of a supplementary Excel spreadsheet with links to each paper, is organized by topic, but can be sorted by first author, order of publication, specific Oman Drilling Project boreholes, and other factors.

show abstract

High‐Temperature Strain Localization and the Nucleation of Oceanic Core Complexes (16.5°N, Mid‐Atlantic Ridge)

Cited by 10 publications

References 73 publications

HTLP metamorphism and fluid‐fluxed melting during multistage anatexis of continental crust (N Sardinia, Italy)

HTLP metamorphism and fluid‐fluxed melting during multistage anatexis of continental crust (N Sardinia, Italy)

Brown Amphibole as Tracer of Tectono-Magmatic Evolution of the Atlantis Bank Oceanic Core Complex (IODP Hole U1473A)

Preface: Special Issue on Ophiolites and Oceanic Lithosphere

Contact Info

Product

Resources

About