Sr, Nd, Pb and trace element systematics of the New Caledonia harzburgites: Tracking source depletion and contamination processes in a SSZ setting

Secchiari, Arianna; Montanini, Alessandra; Bosch, Delphine; Macera, Patrizia; Cluzel, Dominique

doi:10.1016/j.gsf.2019.04.004

Cited by 29 publications

(36 citation statements)

References 97 publications

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“…In contrast to most subduction zone magmatic rocks, Eocene supra-subduction dykes of the Peridotite Nappe dominantly display strong positive Zr and Hf anomalies (~10 times) and contain abundant magmatic zircons (Cluzel et al 2006 Caledonia's peridotites, which are thus likely due to slab-derived magma input (Secchiari et al 2019).…”

Section: Selective Input Of Incompatible Trace-elements Record Of Trementioning

confidence: 99%

“…The Peridotite Nappe is dominantly composed of harzburgite (>80%), dunite and minor lherzolite (in northern massifs only) that represent a prominently depleted supra-subduction mantle lithosphere (Marchesi et al 2009;Pirard et al 2013). Owing to their depletion in incompatible elements compared to primitive mantle composition, residual harzburgites probably underwent about 20%-25% partial melting (Prinzhoffer 1981;Secchiari et al 2019). They are overlain by dunite, pyroxenite, websterite and gabbronorite cumulates (Prinzhoffer 1981).…”

Section: Geological Settingmentioning

confidence: 99%

“…Thin tremolite coatings around high-temperature minerals (olivine/orthopyroxene) and crosscutting tremolite needles, which have been rarely found in unserpentinized harzburgites Secchiari et al 2019), signal early Ca input by circulating fluids or melts. Rocks of the Peridotite Nappe are serpentinized at various degrees (0% to 100%) and this early tremolite crystallization did not survive the development of lizardite-brucite (± chrysotile) mesh and tremolite now only appears in syntectonic or replacement veins in serpentinized peridotites.…”

Section: Geological Settingmentioning

confidence: 99%

“…Positive Eu anomalies have been described in peridotite-hosted hydrothermal fluids (Allen and Seyfrid 2003Seyfrid , 2005Schmidt et al 2007) and in serpentines of mid-oceanic ridges (German et al 1999;Douville et al 2002;Paulick et al 2006, Ningthoujam et al 2012 Assessing the enrichment of tremolite veins in some trace-elements compared to peridotites/serpentinites is not always possible because some trace-element abundances in the latter are below the standard detection limit (Secchiari et al 2019;table 2). When measurable, this enrichment is not uniform and prominent depletion appears in HFSE (Nb, Ta, Zr and Hf), some of which are below the detection limit of standard ICPMS whole rock analysis (Table 2).…”

Section: Selective Input Of Incompatible Trace-elements Record Of Trementioning

confidence: 99%

“…In weakly serpentinized lherzolites of the Peridotite Nappe, calcium content is relatively high (1.5 wt% to 2.2 wt% CaO) . It is lower in unserpentinized harzburgites (0.3 wt% to 0.6 wt% CaO) (Secchiari et al 2019). However, occurrence of such fresh rocks is extremely rare and the bulk of the Peridotite Nappe underwent 40% to 100% serpentinization (lizardite mesh) and contain less than 0.1 wt% CaO (0.01%-0.1%), a general feature of serpentinized peridotites (Kodolànyi et al 2000).…”

Section: Introductionmentioning

confidence: 99%

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Slab-derived origin of tremolite–antigorite veins in a supra-subduction ophiolite: the Peridotite Nappe (New Caledonia) as a case study

Cluzel

Boulvais

Iseppi

et al. 2019

Int J Earth Sci (Geol Rundsch)

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Hydration of mantle peridotites provides information on the exhumation history and on the fluid regime accompanying exhumation of these rocks (reservoirs involved, fluid/rock ratios, temperature of interaction). Highly depleted harzburgites and dunites of the Peridotite Nappe of New Caledonia are crosscut by fractures, which have been pervasively serpentinized, producing lizardite, brucite, magnetite and minor chrysotile in a near-static environment, probably by sea water circulating in cooling joints. This event is generally referred to as "primary serpentinization". In a next step, already serpentinized joints were reopened to produce tension and shear cracks sealed by highertemperature synkinematic fibrous minerals. Locally, tremolite-bearing veins and pockets, which do not display evidence for void infill, were generated by metasomatic replacement of the wall rock peridotite. Most veins only contain fibrous antigorite but some display tremolite-antigorite intergrowths or even pure tremolite. The latter rocks yield high contents of Ca and incompatible elements, which contrast with the overall depletion of the peridotite host rock and suggest contribution of an external source. Whole-rock geochemical and isotopic features (87 Sr/ 86 Sr,  18 O and H) suggest that antigorite veins, which bear highly radiogenic Sr isotope signatures, were strongly influenced by fluids emitted by the subducted slab and associated sediments. In contrast, the geochemical and isotopic signatures of tremolite-bearing rocks suggest a genetic link with Early Eocene supra-subduction dykes and fluids that leached them. Calcium, strontium and REE-bearing oxidized fluids reacted with already serpentinized fracture wall rock as shown by fibre nucleation, chromite alteration and high Cr contents in tremolite. The bulk of syn-tectonic fluid-rock interaction associated with shear and tensile fracture development probably occurred at the onset of Eocene intra-oceanic subduction, when the buoyant lower plate (the South Loyalty Basin) obliquely forced its way beneath the nascent Loyalty fore-arc. Mobile elements extracted from supra-subduction dykes temporarily enriched the circulating fluids and generated tremolite, antigorite, Mg-chlorite and magnetite instead of antigorite and magnetite solely. Tremolite crystallization probably ceased due to the exhaustion of Ca-rich fluids in a globally cooling fore-arc environment.

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Section: Selective Input Of Incompatible Trace-elements Record Of Trementioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Selective Input Of Incompatible Trace-elements Record Of Trementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Slab-derived origin of tremolite–antigorite veins in a supra-subduction ophiolite: the Peridotite Nappe (New Caledonia) as a case study

Cluzel

Boulvais

Iseppi

et al. 2019

Int J Earth Sci (Geol Rundsch)

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Serpentinization of New Caledonia peridotites: from depth to (sub-)surface

Ulrich

Muñoz

Boulvais

et al. 2020

Contrib Mineral Petrol

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Serpentinization processes occur at geological settings notably during oceanic subduction and 32 obduction, where mantle rocks interact with water. Different types of serpentine minerals form 33 according to temperature and pressure conditions, and potentially chemical exchanges. Therefore, the 34 characterization of serpentine minerals, and the possible occurrence of multiple serpentine 35 generations in mantle rocks provide essential constraints on the conditions of fluid-rock interactions 36 in the mantle. The serpentinite sole of the Peridotite Nappe of New Caledonia (Southwest Pacific) is 37 the result of several superimposed serpentinisation events. The latter were discriminated using 38 mineralogical and geochemical approaches and modeling. 39Lizardite represents more than 80% of the entire serpentine content of the ophiolite. It is 40 crosscut by several veins of other serpentine species in the serpentinite sole. The relative chronology 41 appears as follows: lizardite 1 → lizardite 2 → antigorite → chrysotile → polygonal serpentine. The 42 transition from primary/magmatic minerals to lizardite 1 is almost isochemical. Then, the 43 development of lizardite 2 yields an enrichment in fluid-mobile elements such as Cs, Rb, Ba, U and 44 light rare-earth elements and an apparent increase of the Fe 3+ /FeT ratio. The modeling of δ 18 O values 45 (1.9‰ to 13.9‰) and δD values (88‰ to 106‰) of all serpentine species through Monte-Carlo 46 simulations show that New Caledonia serpentines were mainly formed in equilibrium with fluids 47 released by the dehydration of altered oceanic crust (AOC) during subduction between 250°C and 48 350°C. AOC-derived fluids are not the unique source of fluids since a low temperature (100-150°C) 49 meteoric component is also predicted by the models. Thus, serpentine acts as a tape-recorder of fluid-50 rock interactions into the mantle from depth to (sub-)surface. 51 52 assumed to be one of the most efficient ways to recycle water and fluid-mobile elements (FME) into 67 the deeper mantle (

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Hydrous mafic–ultramafic intrusives at the roots of a proto-arc: implications for crust building and mantle source heterogeneity in young forearc regions

Secchiari

Montanini

Cluzel

2022

Contrib Mineral Petrol

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Sr, Nd, Pb and trace element systematics of the New Caledonia harzburgites: Tracking source depletion and contamination processes in a SSZ setting

Cited by 29 publications

References 97 publications

Slab-derived origin of tremolite–antigorite veins in a supra-subduction ophiolite: the Peridotite Nappe (New Caledonia) as a case study

Slab-derived origin of tremolite–antigorite veins in a supra-subduction ophiolite: the Peridotite Nappe (New Caledonia) as a case study

Serpentinization of New Caledonia peridotites: from depth to (sub-)surface

Hydrous mafic–ultramafic intrusives at the roots of a proto-arc: implications for crust building and mantle source heterogeneity in young forearc regions

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