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Jason Harvey

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Tsuyoshi Komiya

The University of Tokyo

Kristoffer Szilas

University of Copenhagen

Anna Sałacińska

Università degli Studi di Padova

Université Paris Cité

Guochun Zhao 赵国春

The University of Hong Kong

Roberto Visalli

Università di Catania

Miguel Tupinambá

Uerj

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Papers by Jason Harvey

Tectonics of the Isua Supracrustal Belt 1: P‐T‐X‐d Constraints of a Poly‐Metamorphic Terrane

Tectonics, 2021

Models to describe the nature of the Earth's crustal evolution during the Archean vary substantia... more Models to describe the nature of the Earth's crustal evolution during the Archean vary substantially, from horizontal lithospheric motions with subduction-like movement (Abbott et al., 1994), to vertical tectonics defined by sub-/intralithospheric diapirism (Collins, 1989; Sizova et al., 2015), extensive volcanism (Moore & Webb, 2013; Turcotte, 1989), and the formation of a single-plate lithosphere. First-order questions include when and how horizontal lithospheric motion (e.g., subduction) became the dominant process by which Earth's interior cools, deforms, and evolves (Lenardic, 2018). A change in geodynamics between ∼3.2-2.5 Ga is proposed based on the global geochemical and zircon record indicating an increased contribution of reworked crust for magma generation while juvenile mantle additions decreased during that time (e.g., Dhuime et al., 2012; Moyen & Laurent, 2018). A recent review of the existing metamorphic record suggests that Earth has experienced spatial and temporal changes of global crustal thermal gradients probably linked to transitions in the tectonic regime, from stagnant-lid tectonics to mobile-lid plate tectonics (Brown & Johnson, 2018). The main changes occurred at ∼2.5 Ga, ∼1.0 Ga, and 0.72 Ga, Ga which are associated with the widespread appearance of paired metamorphic belts, dominance of high T/P gradients (>775°C/GPa), and increasing abundance of low T/P gradients (<375°C/GPa), respectively. The presence of a distinct bimodality of low and high T/P gradients is indeed a feature commonly associated with plate tectonics (Brown, 2010; Miyashiro, 1961, 1973) and its gradual emergence argues for progressive onset and evolution to horizontal-dominated geodynamics since the Neoarchean (Holder et al., 2019). In stark contrast with these interpretations, multiple subduction-driven events are invoked to explain the origin and evolution of the Eoarchean Isua supracrustal belt (ISB) of southwest Greenland (Figure 1), one of the oldest metamorphic terranes known, which some workers have interpreted to reflect the onset of plate tectonics as

Earth’s earliest phaneritic ultramafic rocks 1: plate tectonic mantle slices or crustal cumulates?

Messengers from the mantle : unravelling the effects of melting and metasomatism in the upper mantle using Re-Os isotope systematics

(Table 4) Re-Os isotope ratios of sulphides from ODP Hole 209-1274A

Neodymium isotopes

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit:

Subduction initiation and volcanic arc origins – geochemical clues from the Izu-Bonin-Mariana system

Geochemistry of highly depleted peridotites of the Mid-Atlantic Ridge

Gallstone disease continues to be one of the leading problems in modern gastroenterology and in m... more Gallstone disease continues to be one of the leading problems in modern gastroenterology and in majority of cases requiring surgical management. This pathology has large impact on Saudi Arabian population and its Health system. Laparoscopic cholecystectomy has become a procedure of choice in current management of acute and chronic cholecystitis. The aim of this surgical audit based study was to analyze current management outcome in selected group of patients, who underwent laparoscopic cholecystectomy procedure in Saudi Arabian province of Al Kharj with relatively large local population. The multiple factors including patient's demographic characteristics, modality and results of investigations, as well as, surgical outcome were analyzed and compared. This study demonstrated satisfactory surgical outcomes in gallstone management in the Prince Sattam Bin Abdulaziz University affiliated hospital, which demonstrated low complications rate and cost effectiveness.

Publisher Correction: Rapid metal pollutant deposition from the volcanic plume of Kīlauea, Hawai’i

Communications Earth & Environment

The original version of this Article contained an error in ref. 26, which was incorrectly describ... more

(Table 2) Geochemical composition of variably altered peridotite from ODP Hole 209-1268A

Geochemisty and Re-Os isotope ratios of peridotites from ODP Hole 209-1274A from the Mid-Atlantic ridge

Shiga toxin-producing Escherichia coli serogroup O26 is an important public health pathogen. Phyl... more Shiga toxin-producing Escherichia coli serogroup O26 is an important public health pathogen. Phylogenetic bacterial lineages in a country can be associated with the level and timing of international imports of live cattle, the main reservoir. We sequenced the genomes of 152 E. coli O26 isolates from New Zealand and compared them with 252 E. coli O26 genomes from 14 other countries. Gene variation among isolates from humans, animals, and food was strongly associated with country of origin and stx toxin profile but not isolation source. Time of origin estimates indicate serogroup O26 sequence type 21 was introduced at least 3 times into New Zealand from the 1920s to the 1980s, whereas nonvirulent O26 sequence type 29 strains were introduced during the early 2000s. New Zealand's remarkably fewer introductions of Shiga toxin-producing Escherichia coli O26 compared with other countries (such as Japan) might be related to patterns of trade in live cattle.

Heterogeneous nickel isotope compositions of the terrestrial mantle - Part 2: Mafic lithologies

Geochimica et Cosmochimica Acta

Rapid metal pollutant deposition from the volcanic plume of Kīlauea, Hawai’i

Communications Earth & Environment

Long-lived basaltic volcanic eruptions are a globally important source of environmentally reactiv... more Long-lived basaltic volcanic eruptions are a globally important source of environmentally reactive, volatile metal pollutant elements such as selenium, cadmium and lead. The 2018 eruption of Kīlauea, Hawai’i produced exceptionally high discharge of metal pollutants, and was an unprecedented opportunity to track them from vent to deposition. Here we show, through geochemical sampling of the plume that volatile metal pollutants were depleted in the plume up to 100 times faster than refractory species, such as magnesium and iron. We propose that this rapid wet deposition of complexes containing reactive and potentially toxic volatile metal pollutants may disproportionately impact localised areas close to the vent. We infer that the relationship between volatility and solubility is an important control on the atmospheric behaviour of elements. We suggest that assessment of hazards from volcanic emissions should account for heterogeneous plume depletion of metal pollutants.

Lightning strikes as a major facilitator of prebiotic phosphorus reduction on early Earth

Nature Communications

When hydrated, phosphides such as the mineral schreibersite, (Fe,Ni)3P, allow for the synthesis o... more When hydrated, phosphides such as the mineral schreibersite, (Fe,Ni)3P, allow for the synthesis of important phosphorus-bearing organic compounds. Such phosphides are common accessory minerals in meteorites; consequently, meteorites are proposed to be a main source of prebiotic reactive phosphorus on early Earth. Here, we propose an alternative source for widespread phosphorus reduction, arguing that lightning strikes on early Earth potentially formed 10–1000 kg of phosphide and 100–10,000 kg of phosphite and hypophosphite annually. Therefore, lightning could have been a significant source of prebiotic, reactive phosphorus which would have been concentrated on landmasses in tropical regions. Lightning strikes could likewise provide a continual source of prebiotic reactive phosphorus independent of meteorite flux on other Earth-like planets, potentially facilitating the emergence of terrestrial life indefinitely.

The Conductive Cooling of Planetesimals With Temperature‐Dependent Properties

Journal of Geophysical Research: Planets

Planetesimals are small rocky or icy bodies of a few to a few hundred kilometers in diameter that... more Planetesimals are small rocky or icy bodies of a few to a few hundred kilometers in diameter that formed by collisional coagulation in the protoplanetary disk, and are considered the building blocks of larger planetary bodies . These early planetesimals are hypothesized to be the primary parent bodies of meteorites while the remnants of disrupted planetesimals, preserved as asteroids, are termed the secondary parent bodies . Planetesimals experienced varied thermal histories: differentiated meteorites displaying igneous textures are sourced from planetesimals that underwent melting and segregation of a metallic core and silicate mantle , while

Late Cadomian rifting of the NW Gondwana margin and the reworking of Precambrian crust – evidence from bimodal magmatism in the early Paleozoic Moroccan Meseta

International Geology Review

ABSTRACT The Meseta Goaïda magmatism, which occurs as gabbro, dolerite and rhyolitic intrusions i... more ABSTRACT The Meseta Goaïda magmatism, which occurs as gabbro, dolerite and rhyolitic intrusions in the Neoproterozoic basement and Cambrian platform sedimentary series of the Moroccan Hercynian orogen, has been ascribed to the Variscan orogenesis in the late Palaeozoic. Here, we provide new LA–ICP-MS U-Pb zircon ages – ranging from c. 519 Ma to c. 479 Ma – of this magmatism that reveal, for the first time in the Moroccan Central Meseta, the existence of early Cambrian to early Ordovician bimodal magmatism. Inherited zircons in these magmatic rocks yield dates that range from c. 1.2 to 1.0 Ga and c. 0.63 to 0.50 Ga. This inheritance suggests provenance from Precambrian crustal sources in the Cadomian‒Pan-African of the NW margin of the West African Craton, which is buried beneath the currently exposed Paleozoic Moroccan Meseta. The affinity of this early Palaeozoic magmatism is mainly tholeiite to transitional for the mafic rocks and high-K calc-alkaline for the silicic rocks. The Cambrian–Ordovician age and varying parental magma signature – as shown by trace element and Sr-Nd-Pb isotopic data from this magmatism and its Neoproterozoic granitoid basement rocks – indicate that the Moroccan Meseta early-Paleozoic magmatism might be associated with the weakening of the continental lithosphere during the early stages of rifting during the Cambrian–Ordovician along the NW Gondwana margin. This is supported by the presence of inherited zircons derived from reworking of the Precambrian crust in the early-Palaeozoic magmas.

Heterogeneous nickel isotopic compositions in the terrestrial mantle – Part 1

Geochimica et Cosmochimica Acta

High precision nickel stable isotopic compositions (d 60/58 Ni) are reported for 22 peridotite xe... more High precision nickel stable isotopic compositions (d 60/58 Ni) are reported for 22 peridotite xenoliths from the USA (Kilbourne Hole, New Mexico), Tanzania, and Cameroon. For a subset of these, d 60/58 Ni is also reported for their constituent mineral separates (olivine, orthopyroxene, clinopyroxene, and spinel). Bulk peridotites show significant heterogeneity in Ni isotopic composition, ranging from +0.02‰ to +0.26‰. Unmetasomatised fertile peridotites from three localities, define an average d 60/58 Ni of +0.19±0.09‰ (n = 18). This value is comparable to previous estimates for the d 60/58 Ni of the bulk silicate earth (BSE), but is unlikely to be representative, given observed heterogeneity, presented here and elsewhere. Samples with reaction rims and interstitial glass (interpreted as petrographic indications of minor metasomatism) were excluded from this average; their Ni isotopic compositions extend to lighter values, spanning nearly the entire range observed in peridotite worldwide. Dunites (n = 2) are lighter in d 60/58 Ni than lherzolites and harzburgites from the same location, and pyroxenites (n = 5) range from +0.16‰ to as light as À0.38‰. The d 60/58 Ni in the Kilbourne Hole xenoliths correlate negatively with bulk-rock Fe concentration and positively with 143 Nd/ 144 Nd, providing evidence that light d 60/58 Ni is associated with mantle fertility and enrichment. The trend between d 60/58 Ni and Fe concentration in bulk rocks appears to be global, replicated across the peridotites in this work from other localities, and in literature data. The inter-mineral fractionations are small; the maximum difference between heaviest and lightest phase is 0.12‰. This provides evidence that bulk rock d 60/58 Ni variation does not result from differences in modal mineralogy, fractional crystallization or degrees of partial melting. The d 60/58 Ni fractionation appears to be an equilibrium effect and usually is in the decreasing order spinel > olivine = orthopyroxene > clinopyroxene. However, the fractionation between clinopyroxene and orthopyroxene varies in magnitude and sign, and is correlated with pyroxene Si/Fe positively, and Fe/Mg negatively. The magnitude of inter-pyroxene fractionation also correlates with other pyroxene compositional ratios (e.g. La/Sm clinopyroxene ); as well as bulk rock d 60/58 Ni, and [U]. These data provide evidence that Ni isotopes fractionate at the bulk rock and mineral scale in response to mantle enrichment processes, possibly related to recycling of isotopically light subducted components.

Ultramafic rocks at the Isua supracrustal belt and East Pilbara Terrane are crustal cumulates, not slices of early mantle

Eoarchean tectono-metamorphic signatures recorded on the Isua Supracrustal Belt

Effects of melting, subduction-related metasomatism, and sub-solidus equilibration on the distribution of water contents in the mantle beneath the Rio Grande Rift

Geochimica et Cosmochimica Acta

The distribution of water in the upper mantle plays a crucial role in the Earth's deep water cycl... more The distribution of water in the upper mantle plays a crucial role in the Earth's deep water cycle, magmatism, and plate tectonics. To better constrain how these large-scale geochemical systems operate, peridotite and pyroxenite mantle xenoliths from Kilbourne Hole (KH) and Rio Puerco (RP) along the Rio Grande Rift (NM, USA) were analyzed for water contents, and major and trace element compositions. These xenoliths sample a lithosphere whose composition was influenced by subduction and rifting, and can be used to examine the effects of melting, metasomatism, and sub-solidus equilibration on the behavior of water. The KH peridotites have 252-447 ppm H2O in clinopyroxene (Cpx) and 73-174 ppm H2O in orthopyroxene (Opx) and can be divided into two groups. Group 1, representing the majority of KH xenoliths, has flat to depleted light rare earth element (LREE) patterns in Cpx and bulk-rock when normalized to primitive mantle (PM). The trace element and water contents of Group 1 KH 1962

Old magma and a new, intrusive trigger: using diffusion chronometry to understand the rapid-onset Calbuco eruption, April 2015 (Southern Chile)

Contributions to Mineralogy and Petrology

In April 2015, an unpredicted rapid-onset eruption occurred at Calbuco Volcano, Southern Andes of... more In April 2015, an unpredicted rapid-onset eruption occurred at Calbuco Volcano, Southern Andes of Chile. This event consisted of two, sub-Plinian eruptions separated by a few hours. By analysis of Fe-Ti exchange between ilmenite and titanomagnetite crystals in samples of erupted material, we determine timescales of pre-eruptive heating experienced at the partially solidified chamber base and constrain the magma residence time for the bulk of the carrier magma. Analysis of the Fe-Ti oxide pairs from a sample retrieved from a pyroclastic density current deposit (Cal-160) shows that it was affected by a significant heating event (recording 70-220 °C of heating), while other collected samples did not record this late heating. This sample is interpreted to represent a piece of crystal mush located at the bottom of a prolate, ellipsoidal mush reservoir, mobilised < 4 days before the eruption by a triggering pulse of mafic magma considerably hotter than the typical magmatic temperature of the reservoir. Another two fall deposit samples (lapillus, Cal-149Tb and Cal-155) of the eruption are interpreted to represent resident, eruptible magmas that did not interact with any magma recharge immediately prior to or during the eruption. We infer that these magmas had been at eruption temperature for some years based on their extensively equilibrated Fe-Ti oxides. Communicated by Mark S Ghiorso.

Tectonics of the Isua Supracrustal Belt 1: P‐T‐X‐d Constraints of a Poly‐Metamorphic Terrane

Tectonics, 2021

Models to describe the nature of the Earth's crustal evolution during the Archean vary substantia... more Models to describe the nature of the Earth's crustal evolution during the Archean vary substantially, from horizontal lithospheric motions with subduction-like movement (Abbott et al., 1994), to vertical tectonics defined by sub-/intralithospheric diapirism (Collins, 1989; Sizova et al., 2015), extensive volcanism (Moore & Webb, 2013; Turcotte, 1989), and the formation of a single-plate lithosphere. First-order questions include when and how horizontal lithospheric motion (e.g., subduction) became the dominant process by which Earth's interior cools, deforms, and evolves (Lenardic, 2018). A change in geodynamics between ∼3.2-2.5 Ga is proposed based on the global geochemical and zircon record indicating an increased contribution of reworked crust for magma generation while juvenile mantle additions decreased during that time (e.g., Dhuime et al., 2012; Moyen & Laurent, 2018). A recent review of the existing metamorphic record suggests that Earth has experienced spatial and temporal changes of global crustal thermal gradients probably linked to transitions in the tectonic regime, from stagnant-lid tectonics to mobile-lid plate tectonics (Brown & Johnson, 2018). The main changes occurred at ∼2.5 Ga, ∼1.0 Ga, and 0.72 Ga, Ga which are associated with the widespread appearance of paired metamorphic belts, dominance of high T/P gradients (>775°C/GPa), and increasing abundance of low T/P gradients (<375°C/GPa), respectively. The presence of a distinct bimodality of low and high T/P gradients is indeed a feature commonly associated with plate tectonics (Brown, 2010; Miyashiro, 1961, 1973) and its gradual emergence argues for progressive onset and evolution to horizontal-dominated geodynamics since the Neoarchean (Holder et al., 2019). In stark contrast with these interpretations, multiple subduction-driven events are invoked to explain the origin and evolution of the Eoarchean Isua supracrustal belt (ISB) of southwest Greenland (Figure 1), one of the oldest metamorphic terranes known, which some workers have interpreted to reflect the onset of plate tectonics as

Earth’s earliest phaneritic ultramafic rocks 1: plate tectonic mantle slices or crustal cumulates?

Messengers from the mantle : unravelling the effects of melting and metasomatism in the upper mantle using Re-Os isotope systematics

(Table 4) Re-Os isotope ratios of sulphides from ODP Hole 209-1274A

Neodymium isotopes

This article appeared in a journal published by Elsevier. The attached copy is furnished to the a... more This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit:

Subduction initiation and volcanic arc origins – geochemical clues from the Izu-Bonin-Mariana system

Geochemistry of highly depleted peridotites of the Mid-Atlantic Ridge

Gallstone disease continues to be one of the leading problems in modern gastroenterology and in m... more Gallstone disease continues to be one of the leading problems in modern gastroenterology and in majority of cases requiring surgical management. This pathology has large impact on Saudi Arabian population and its Health system. Laparoscopic cholecystectomy has become a procedure of choice in current management of acute and chronic cholecystitis. The aim of this surgical audit based study was to analyze current management outcome in selected group of patients, who underwent laparoscopic cholecystectomy procedure in Saudi Arabian province of Al Kharj with relatively large local population. The multiple factors including patient's demographic characteristics, modality and results of investigations, as well as, surgical outcome were analyzed and compared. This study demonstrated satisfactory surgical outcomes in gallstone management in the Prince Sattam Bin Abdulaziz University affiliated hospital, which demonstrated low complications rate and cost effectiveness.

Publisher Correction: Rapid metal pollutant deposition from the volcanic plume of Kīlauea, Hawai’i

Communications Earth & Environment

The original version of this Article contained an error in ref. 26, which was incorrectly describ... more

(Table 2) Geochemical composition of variably altered peridotite from ODP Hole 209-1268A

Geochemisty and Re-Os isotope ratios of peridotites from ODP Hole 209-1274A from the Mid-Atlantic ridge

Shiga toxin-producing Escherichia coli serogroup O26 is an important public health pathogen. Phyl... more Shiga toxin-producing Escherichia coli serogroup O26 is an important public health pathogen. Phylogenetic bacterial lineages in a country can be associated with the level and timing of international imports of live cattle, the main reservoir. We sequenced the genomes of 152 E. coli O26 isolates from New Zealand and compared them with 252 E. coli O26 genomes from 14 other countries. Gene variation among isolates from humans, animals, and food was strongly associated with country of origin and stx toxin profile but not isolation source. Time of origin estimates indicate serogroup O26 sequence type 21 was introduced at least 3 times into New Zealand from the 1920s to the 1980s, whereas nonvirulent O26 sequence type 29 strains were introduced during the early 2000s. New Zealand's remarkably fewer introductions of Shiga toxin-producing Escherichia coli O26 compared with other countries (such as Japan) might be related to patterns of trade in live cattle.

Heterogeneous nickel isotope compositions of the terrestrial mantle - Part 2: Mafic lithologies

Geochimica et Cosmochimica Acta

Rapid metal pollutant deposition from the volcanic plume of Kīlauea, Hawai’i

Communications Earth & Environment

Long-lived basaltic volcanic eruptions are a globally important source of environmentally reactiv... more Long-lived basaltic volcanic eruptions are a globally important source of environmentally reactive, volatile metal pollutant elements such as selenium, cadmium and lead. The 2018 eruption of Kīlauea, Hawai’i produced exceptionally high discharge of metal pollutants, and was an unprecedented opportunity to track them from vent to deposition. Here we show, through geochemical sampling of the plume that volatile metal pollutants were depleted in the plume up to 100 times faster than refractory species, such as magnesium and iron. We propose that this rapid wet deposition of complexes containing reactive and potentially toxic volatile metal pollutants may disproportionately impact localised areas close to the vent. We infer that the relationship between volatility and solubility is an important control on the atmospheric behaviour of elements. We suggest that assessment of hazards from volcanic emissions should account for heterogeneous plume depletion of metal pollutants.

Lightning strikes as a major facilitator of prebiotic phosphorus reduction on early Earth

Nature Communications

When hydrated, phosphides such as the mineral schreibersite, (Fe,Ni)3P, allow for the synthesis o... more When hydrated, phosphides such as the mineral schreibersite, (Fe,Ni)3P, allow for the synthesis of important phosphorus-bearing organic compounds. Such phosphides are common accessory minerals in meteorites; consequently, meteorites are proposed to be a main source of prebiotic reactive phosphorus on early Earth. Here, we propose an alternative source for widespread phosphorus reduction, arguing that lightning strikes on early Earth potentially formed 10–1000 kg of phosphide and 100–10,000 kg of phosphite and hypophosphite annually. Therefore, lightning could have been a significant source of prebiotic, reactive phosphorus which would have been concentrated on landmasses in tropical regions. Lightning strikes could likewise provide a continual source of prebiotic reactive phosphorus independent of meteorite flux on other Earth-like planets, potentially facilitating the emergence of terrestrial life indefinitely.

The Conductive Cooling of Planetesimals With Temperature‐Dependent Properties

Journal of Geophysical Research: Planets

Planetesimals are small rocky or icy bodies of a few to a few hundred kilometers in diameter that... more Planetesimals are small rocky or icy bodies of a few to a few hundred kilometers in diameter that formed by collisional coagulation in the protoplanetary disk, and are considered the building blocks of larger planetary bodies . These early planetesimals are hypothesized to be the primary parent bodies of meteorites while the remnants of disrupted planetesimals, preserved as asteroids, are termed the secondary parent bodies . Planetesimals experienced varied thermal histories: differentiated meteorites displaying igneous textures are sourced from planetesimals that underwent melting and segregation of a metallic core and silicate mantle , while

Late Cadomian rifting of the NW Gondwana margin and the reworking of Precambrian crust – evidence from bimodal magmatism in the early Paleozoic Moroccan Meseta

International Geology Review

ABSTRACT The Meseta Goaïda magmatism, which occurs as gabbro, dolerite and rhyolitic intrusions i... more ABSTRACT The Meseta Goaïda magmatism, which occurs as gabbro, dolerite and rhyolitic intrusions in the Neoproterozoic basement and Cambrian platform sedimentary series of the Moroccan Hercynian orogen, has been ascribed to the Variscan orogenesis in the late Palaeozoic. Here, we provide new LA–ICP-MS U-Pb zircon ages – ranging from c. 519 Ma to c. 479 Ma – of this magmatism that reveal, for the first time in the Moroccan Central Meseta, the existence of early Cambrian to early Ordovician bimodal magmatism. Inherited zircons in these magmatic rocks yield dates that range from c. 1.2 to 1.0 Ga and c. 0.63 to 0.50 Ga. This inheritance suggests provenance from Precambrian crustal sources in the Cadomian‒Pan-African of the NW margin of the West African Craton, which is buried beneath the currently exposed Paleozoic Moroccan Meseta. The affinity of this early Palaeozoic magmatism is mainly tholeiite to transitional for the mafic rocks and high-K calc-alkaline for the silicic rocks. The Cambrian–Ordovician age and varying parental magma signature – as shown by trace element and Sr-Nd-Pb isotopic data from this magmatism and its Neoproterozoic granitoid basement rocks – indicate that the Moroccan Meseta early-Paleozoic magmatism might be associated with the weakening of the continental lithosphere during the early stages of rifting during the Cambrian–Ordovician along the NW Gondwana margin. This is supported by the presence of inherited zircons derived from reworking of the Precambrian crust in the early-Palaeozoic magmas.

Heterogeneous nickel isotopic compositions in the terrestrial mantle – Part 1

Geochimica et Cosmochimica Acta

High precision nickel stable isotopic compositions (d 60/58 Ni) are reported for 22 peridotite xe... more High precision nickel stable isotopic compositions (d 60/58 Ni) are reported for 22 peridotite xenoliths from the USA (Kilbourne Hole, New Mexico), Tanzania, and Cameroon. For a subset of these, d 60/58 Ni is also reported for their constituent mineral separates (olivine, orthopyroxene, clinopyroxene, and spinel). Bulk peridotites show significant heterogeneity in Ni isotopic composition, ranging from +0.02‰ to +0.26‰. Unmetasomatised fertile peridotites from three localities, define an average d 60/58 Ni of +0.19±0.09‰ (n = 18). This value is comparable to previous estimates for the d 60/58 Ni of the bulk silicate earth (BSE), but is unlikely to be representative, given observed heterogeneity, presented here and elsewhere. Samples with reaction rims and interstitial glass (interpreted as petrographic indications of minor metasomatism) were excluded from this average; their Ni isotopic compositions extend to lighter values, spanning nearly the entire range observed in peridotite worldwide. Dunites (n = 2) are lighter in d 60/58 Ni than lherzolites and harzburgites from the same location, and pyroxenites (n = 5) range from +0.16‰ to as light as À0.38‰. The d 60/58 Ni in the Kilbourne Hole xenoliths correlate negatively with bulk-rock Fe concentration and positively with 143 Nd/ 144 Nd, providing evidence that light d 60/58 Ni is associated with mantle fertility and enrichment. The trend between d 60/58 Ni and Fe concentration in bulk rocks appears to be global, replicated across the peridotites in this work from other localities, and in literature data. The inter-mineral fractionations are small; the maximum difference between heaviest and lightest phase is 0.12‰. This provides evidence that bulk rock d 60/58 Ni variation does not result from differences in modal mineralogy, fractional crystallization or degrees of partial melting. The d 60/58 Ni fractionation appears to be an equilibrium effect and usually is in the decreasing order spinel > olivine = orthopyroxene > clinopyroxene. However, the fractionation between clinopyroxene and orthopyroxene varies in magnitude and sign, and is correlated with pyroxene Si/Fe positively, and Fe/Mg negatively. The magnitude of inter-pyroxene fractionation also correlates with other pyroxene compositional ratios (e.g. La/Sm clinopyroxene ); as well as bulk rock d 60/58 Ni, and [U]. These data provide evidence that Ni isotopes fractionate at the bulk rock and mineral scale in response to mantle enrichment processes, possibly related to recycling of isotopically light subducted components.

Ultramafic rocks at the Isua supracrustal belt and East Pilbara Terrane are crustal cumulates, not slices of early mantle

Eoarchean tectono-metamorphic signatures recorded on the Isua Supracrustal Belt

Effects of melting, subduction-related metasomatism, and sub-solidus equilibration on the distribution of water contents in the mantle beneath the Rio Grande Rift

Geochimica et Cosmochimica Acta

The distribution of water in the upper mantle plays a crucial role in the Earth's deep water cycl... more The distribution of water in the upper mantle plays a crucial role in the Earth's deep water cycle, magmatism, and plate tectonics. To better constrain how these large-scale geochemical systems operate, peridotite and pyroxenite mantle xenoliths from Kilbourne Hole (KH) and Rio Puerco (RP) along the Rio Grande Rift (NM, USA) were analyzed for water contents, and major and trace element compositions. These xenoliths sample a lithosphere whose composition was influenced by subduction and rifting, and can be used to examine the effects of melting, metasomatism, and sub-solidus equilibration on the behavior of water. The KH peridotites have 252-447 ppm H2O in clinopyroxene (Cpx) and 73-174 ppm H2O in orthopyroxene (Opx) and can be divided into two groups. Group 1, representing the majority of KH xenoliths, has flat to depleted light rare earth element (LREE) patterns in Cpx and bulk-rock when normalized to primitive mantle (PM). The trace element and water contents of Group 1 KH 1962

Old magma and a new, intrusive trigger: using diffusion chronometry to understand the rapid-onset Calbuco eruption, April 2015 (Southern Chile)

Contributions to Mineralogy and Petrology

In April 2015, an unpredicted rapid-onset eruption occurred at Calbuco Volcano, Southern Andes of... more In April 2015, an unpredicted rapid-onset eruption occurred at Calbuco Volcano, Southern Andes of Chile. This event consisted of two, sub-Plinian eruptions separated by a few hours. By analysis of Fe-Ti exchange between ilmenite and titanomagnetite crystals in samples of erupted material, we determine timescales of pre-eruptive heating experienced at the partially solidified chamber base and constrain the magma residence time for the bulk of the carrier magma. Analysis of the Fe-Ti oxide pairs from a sample retrieved from a pyroclastic density current deposit (Cal-160) shows that it was affected by a significant heating event (recording 70-220 °C of heating), while other collected samples did not record this late heating. This sample is interpreted to represent a piece of crystal mush located at the bottom of a prolate, ellipsoidal mush reservoir, mobilised < 4 days before the eruption by a triggering pulse of mafic magma considerably hotter than the typical magmatic temperature of the reservoir. Another two fall deposit samples (lapillus, Cal-149Tb and Cal-155) of the eruption are interpreted to represent resident, eruptible magmas that did not interact with any magma recharge immediately prior to or during the eruption. We infer that these magmas had been at eruption temperature for some years based on their extensively equilibrated Fe-Ti oxides. Communicated by Mark S Ghiorso.