Overthrust structure of the main ultrabasic new caledonian massives

Avias, Jacques

doi:10.1016/0040-1951(67)90017-0

Cited by 114 publications

(65 citation statements)

References 6 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The NW-SE elongated main island represents the emerged portion of the New Caledonia ridge and includes a large allochthonous sheet of oceanic lithosphere thrusted over continental basement at the late Eocene (Avias, 1967;Cluzel et al, 2001;Pirard et al, 2013). The 3.5 km thick ophiolite nappe covers an area of 7000 km 2 distributed throughout the island, the main part covering the southern end of the main island.…”

Section: Geological Setting Of the Prony Hydrothermal Fieldmentioning

confidence: 99%

Fluid chemistry of the low temperature hyperalkaline hydrothermal system of Prony Bay (New Caledonia)

et al. 2014

View full text Add to dashboard Cite

Abstract. The terrestrial hyperalkaline springs of Prony Bay (southern lagoon, New Caledonia) have been known since the nineteenth century, but a recent high-resolution bathymetric survey of the seafloor has revealed the existence of numerous submarine structures similar to the well-known Aiguille de Prony, which are also the location of high-pH fluid discharge into the lagoon. During the HYDROPRONY cruise (28 October to 13 November 2011), samples of waters, gases and concretions were collected by scuba divers at underwater vents. Four of these sampling sites are located in Prony Bay at depths up to 50 m. One (Bain des Japonais spring) is also in Prony Bay but uncovered at low tide and another (Rivière des Kaoris spring) is on land slightly above the seawater level at high tide. We report the chemical composition (Na, K, Ca, Mg, Cl, SO 4 , dissolved inorganic carbon, SiO 2 (aq)) of 45 water samples collected at six sites of high-pH water discharge, as well as the composition of gases.Temperatures reach 37 • C at the Bain des Japonais and 32 • C at the spring of the Kaoris. Gas bubbling was observed only at these two springs. The emitted gases contain between 12 and 30 % of hydrogen in volume of dry gas, 6 to 14 % of methane, and 56 to 72 % of nitrogen, with trace amounts of carbon dioxide, ethane and propane.pH values and salinities of all the 45 collected water samples range from the seawater values (8.2 and 35 g L −1 ) to hyperalkaline freshwaters of the Ca-OH type (pH 11 and salinities as low as 0.3 g L −1 ) showing that the collected samples are always a mixture of a hyperalkaline fluid of meteoric origin and ambient seawater. Cl-normalized concentrations of dissolved major elements first show that the Bain des Japonais is distinct from the other sites. Water collected at this site are three component mixtures involving the highpH fluid, the lagoon seawater and the river water from the nearby Rivière du Carénage. The chemical compositions of Published by Copernicus Publications on behalf of the European Geosciences Union. C. Monnin et al.: Low temperature hyperalkaline hydrothermal system of Prony Baythe hyperalkaline endmembers (at pH 11) are not significantly different from one site to the other although the sites are several kilometres away from each other and are located on different ultramafic substrata. The very low salinity of the hyperalkaline endmembers shows that seawater does not percolate through the ultramafic formation.Mixing of the hyperalkaline hydrothermal endmember with local seawater produces large ranges and very sharp gradients of pH, salinity and dissolved element concentrations. There is a major change in the composition of the water samples at a pH around 10, which delimitates the marine environment from the hyperalkaline environment. The redox potential evolves toward negative values at high pH indicative of the reducing conditions due to bubbling of the H 2 -rich gas. The calculation of the mineral saturation states carried out for the Na-K-Ca-Mg-Cl-SO 4 -DIC-SiO 2 -H2O system shows...

show abstract

Section: Geological Setting Of the Prony Hydrothermal Fieldmentioning

confidence: 99%

Fluid chemistry of the low temperature hyperalkaline hydrothermal system of Prony Bay (New Caledonia)

et al. 2014

View full text Add to dashboard Cite

show abstract

“…In that sense, they provide a unique opportunity to study the physical and chemical processes that affect the upper mantle in mid oceanic and subduction environments. The Cretaceous to Eocene New Caledonia ophiolite is an extensive and very well-exposed mafic-ultramafic complex ( [Avias, 1967], [Collot et al, 1987] and [Prinzhofer, 1981]) that is still partially connected to the modern oceanic floor of the South Loyalty Basin to the east of the island (Fig. 1).…”

Section: Introductionmentioning

confidence: 99%

Multiple melting stages and refertilization as indicators for ridge to subduction formation: The New Caledonia ophiolite

Ulrich

Picard

Guillot

et al. 2010

Lithos

125

View full text Add to dashboard Cite

The origin of the New Caledonia ophiolite (South West Pacific), one of the largest in the world, is controversial. This nappe of ultramafic rocks (300 km long, 50 km wide and 2 km thick) is thrust upon a smaller nappe (Poya terrane) composed of basalts from mid-ocean ridges (MORB), back arc basins (BABB) and ocean islands (OIB). This nappe was tectonically accreted from the subducting plate prior and during the obduction of the ultramafic nappe.The bulk of the ophiolite is composed of highly depleted harzburgites (± dunites) with characteristic U-shaped bulk-rock rare-earth element (REE) patterns that are attributed to their formation in a forearc environment. In contrast, the origin of spoon-shaped REE patterns of lherzolites in the northernmost klippes was unclear. Our new major element and REE data on whole rocks, spinel and clinopyroxene establish the abyssal affinity of these lherzolites. Significant LREE enrichment in the lherzolites is best explained by partial melting in a spreading ridge, followed by near in-situ refertilization from deeper mantle melts. Using equilibrium melting equations, we show that melts extracted from these lherzolites are compositionally similar to the MORB of the Poya terrane. This is used to infer that the ultramafic nappe and the mafic Poya terrane represent oceanic lithosphere of a single marginal basin that formed during the late Cretaceous. In contrast, our spinel data highlights the strong forearc affinities of the most depleted harzburgites whose compositions are best modeled by hydrous melting of a source that had previously experienced depletion in a spreading ridge. The New Caledonian boninites probably formed during this second stage of partial melting.The two melting events in the New Caledonia ophiolite record the rapid transition from oceanic accretion to convergence in the South Loyalty Basin during the Late Paleocene, with initiation of a new subduction zone at or near the ridge axis.

show abstract

“…This began with the opening of the Tasman and New Caledonia Basins [Weissel and Hayes, 1977;Mignot, 1984], which isolated the two main ridges-Lord Howe Rise and Norfolk Ridge. During late Eocene time, the oceanic lithosphere of the Loyalty Basin overthrust the is land of New Caledonia from NNE to SSW [Avias, 1967;Paris, 1981]. …”

Section: Geodynamic Evolutionmentioning

confidence: 99%

Scientists study deep geological structure between New Hebrides Arc and Eastern Australian Margin

Lafoy¹,

Beuque²,

Bernardel³

et al. 1998

EoS Transactions

View full text Add to dashboard Cite

French and Australian scientists hope that deep seismic profiling performed earlier this year in the southwest Pacific will improve understanding of the geological framework, crustal characteristics, and evolution of basins and ridges between the eastern Australian margin and the New Hebrides Trench system. The data already have indicated that the basements of several basins are thinned and oceanic, that the basements of several ridges are continental, and that, contrary to previous thinking, the Loyalty Basin was formed in late Cretaceous time. Submerged continental fragments separated by deep ocean basins dominate the region in the west, and the Australian Plate is subducting beneath the New Hebrides Arc in the east. Subduction started in Late Miocene time [MacFarlane et al., 1988] at a rate of 12 cm/ year with a convergence direction of WSW‐ENE [Dubois et al., 1977].

show abstract

Overthrust structure of the main ultrabasic new caledonian massives

Cited by 114 publications

References 6 publications

Fluid chemistry of the low temperature hyperalkaline hydrothermal system of Prony Bay (New Caledonia)

Fluid chemistry of the low temperature hyperalkaline hydrothermal system of Prony Bay (New Caledonia)

Multiple melting stages and refertilization as indicators for ridge to subduction formation: The New Caledonia ophiolite

Scientists study deep geological structure between New Hebrides Arc and Eastern Australian Margin

Contact Info

Product

Resources

About