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  • 1
    Electronic Resource
    Electronic Resource
    Development of P-T prograde and P-retrograde, T-prograde isogradic surfaces during blueschist to eclogite regional deformation/metamorphism in New Caledonia, as indicated by progressively developed porphyroblast microstructures (1985)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of metamorphic geology 3 (1985), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract The mid-Tertiary blueschists, eclogites and eclogitic gneisses of northern New Caledonia are the products of four phases of regional metamorphism and deformation (D1–D4). Omphacite, lawsonite and Mn-rich garnet isogradic surfaces were developed during the second deformation (D2) under prograde pressure and temperature conditions. Subsequent deformations (D3–D4) folded these D2 isogradic surfaces. However, within the P-retrograde, T-prograde metamorphic environment of the D4 phase, omphacite altered to albite and chlorite; as a result, a late-stage sub-horizontal isogradic surface developed for omphacite-out where this mineral preserved as relics within syn-D4 albite porphyroblasts. Other minerals that crystallized for the first time (epidote) or had rim additions (almandine phengite) during D4, also form nearly horizontal isogradic surfaces. Porphyroblastic garnet and albite contain inclusion trails, which allow their microstructural development and crystallization of the matrix to be traced from D2 to D4.Late syn-D4 the temperature increased markedly in association with an extensive exothermic decarbonation, even though the rocks were in a state of pressure retrogression. This caused considerable neocrystallization, recrystallization and growth of mattix and porphyroblasts such that, although S2 foliation crenulated by D3 and D4 is readily observable, almost all signs of stored strain due to D3 and D4 have been removed, and the deeper schists and eclogitic gneisses superficially appear to have undergone a drastic annealing recrystallization, post-dating deformation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.1985.tb00305.x
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  • 2
    Electronic Resource
    Electronic Resource
    Chloritoid-bearing rocks associated with blueschists and eclogites, northern New Caledonia (1987)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of metamorphic geology 5 (1987), S. 0 
    Details
    ISSN: 1525-1314
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Abstract Chloritoid-bearing metasedimentary rocks occur in close proximity to blueschists and eclogites in the Tertiary high-pressure metamorphic belt of northern New Caledonia. The typical assemblage of chloritoid-bearing rocks in the epidote zone is quartzchlorite-muscovite-garnet-chloritoid. In the omphacite zone, epidote is an additional member of the chloritoid-bearing assemblage. Paragonite is rare, plagioclase was not detected, and rutile and ilmenite are the Fe-Ti oxide phases. Chloritoid-glaucophane is not a common assemblage. Chloritoid-bearing rocks have relatively low (Ca+K+Na)/Al ratios and the chloritoids are relatively Mg-rich with Mg/ (Mg+Fe) up to about 0.4. A comparison of the mineral assemblages and mineral chemistry with experimental and computed phase equilibria suggest an upper temperature limit near 560° C in the omphacite zone and a minimum temperature limit near 450° C at 10 kbar. An empirical garnet-chlorite Fe-Mg exchange thermometer does not yield consistent results for the higher-grade rocks, suggesting Ts ranging from 390 to 535° C in the omphacite zone and 420–465° C in the epidote zone. The distribution coefficient KD= (Fe/Mg)ctd/(Fe/Mg)chl for chloritoid and chlorite ranges from 3.9 to 6.4, values which are lower than those (=10) from lower greenschist facies rocks, but are near those of upper greenschist facies and albite-epidote amphibolite facies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1525-1314.1987.tb00382.x
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  • 3
    Electronic Resource
    Electronic Resource
    High-pressure schists in Northern New Caledonia (1974)
    Springer
    Contributions to mineralogy and petrology 46 (1974), S. 109-127 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Regional high-pressure metamorphism in the Oligocene-lowermost Miocene (38-21 m.y. before present) produced a schist belt measuring 170×25 km adjacent to a thrust (melange) zone along the northeast margin of New Caledonia. The parent rocks were trench sediments with coeval basic and acid volcanics of Cretaceous-Eocene age in a sequence about 20 km thick. Tectonic events covering the same time span included westwards obduction of the great southern basalt-gabbro-peridotite massif which had no causative relationship with high-pressure metamorphism; eastwards-directed low-angle thrusts in the northern part of the Permian-Mesozoic sialic basement, originating along the melange zone, developed a thick stack of metagreywacke schuppen which capped the high-pressure metamorphic pile. Thus, while the site for sedimentation and metamorphism was an active trench in a northeasterly (oceanward) dipping convergence zone, the adjacent upper oceanic plate apparently was not directly involved in the metamorphic setting. Regional high-pressure assemblages are defined with reference to isograds for paraschist lawsonite, epidote and Ca-amphibole in a continuous progression from lawsonite-albite facies through glaucophanitic greenschists to eclogitic albite-epidote amphibolites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377499
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  • 4
    Electronic Resource
    Electronic Resource
    Subduction regression and oceanward migration of volcanism, North Island, New Zealand (1984)
    [s.l.] : Nature Publishing Group
    Nature 309 (1984), S. 698-700 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Regional calc-alkaline volcanism in the North Island of New Zealand, of early Miocene-Holocene age, is confined to an area north-west of the main axial range of basement Mesozoic grey-wackes. Two geographically and petrologically distinct systems of eruptive rocks trend NW-SE parallel to the length ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/309698a0
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  • 5
    Electronic Resource
    Electronic Resource
    Subduction regression of volcanism in New Zealand (1985)
    [s.l.] : Nature Publishing Group
    Nature 313 (1985), S. 820-821 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] BROTHERS REPLIES-The comments by Ballance et al reflect the problems of bio-stratigraphers trying to equate an imprecise time scale with the more exact ages provided by radiometric methods. The time-lines used in my study1 were based on K-Ar dates for dikes, flows and plutonic intrusions. It is ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/313820b0
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  • 6
    Electronic Resource
    Electronic Resource
    Coalification and graphitization in high-pressure schists in New Caledonia (1978)
    Springer
    Contributions to mineralogy and petrology 68 (1978), S. 63-78 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The northern portion of the Tertiary high-pressure schist belt in New Caledonia contains, from west to east, a metamorphic progression from lawsonite-albite facies through glaucophanitic greenschists to eclogitic albite-epidote amphibolites. This belt is flanked to the west by Upper Cretaceous-Eocene metasediments, of prehnite-pumpellyite grade. Paraschists throughout this whole sequence contain abundant carbonaceous material which shows a progressive metamorphism from coal to graphite. Structural analysis of lithostatic load and oxygen isotope data have provided a PT profile for the carbon metamorphism. In the prehnite-pumpellyite metasediments, phytoclasts were progressively coalified to anthracite rank under PT conditions which extended up to 3 kb/255 ° C at the lawsonite isograd where graphite first appears. On the high grade side of the lawsonite isograd a transitional mixed zone of continued coalification and graphitization occurred within the PT range 3 kb/255 ° C to 5.5 kb/335 ° C which included the ferroglaucophane isograd. Immediately beyond this zone all phytoclasts were completely graphitized before the epidote isograd was reached at 6.3 kb/ 390 ° C. The prevailing metamorphic environment retarded coalification, but accelerated graphitization, under conditions of high pressure and a low temperature gradient (7 ° C/km) that had been generated within the sedimentary pile by rapid tectonic thickening and consequent deep burial.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00375447
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  • 7
    Electronic Resource
    Electronic Resource
    Blueschist ophiolites in the melange zone, northern New Caledonia (1977)
    Springer
    Contributions to mineralogy and petrology 65 (1977), S. 69-78 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract A regional melange zone, 150 km long and 30 km wide, forms the southern boundary and structural capping to a high-pressure blueschist belt in northern New Caledonia. The disrupted country rocks in the melange zone are Mesozoic metagrey-wackes and Eocene chert-limestone sequences which have been penetrated from below by tectonically-injected ophiolite slivers containing metamorphosed serpentinite, gabbro, dolerite, basalt, tuff, chert and shale. An ocean crust origin for these rocks is indicated by chemical, mineralogical and radiometric data from coastal outcrops at Anse Ponandou on the northeast coast. The age (41 m.y.), metamorphic environment (350 ° C at 7 kb), and mineral association (acmitic jadeite-riebeckite-pyropic spessartine-pistacitic epidote-lawsonite-high Si phengite) are significantly different from those of the adjacent regional high-pressure schist belt, indicating a separate structural site for blueschist metamorphism of buried ophiolitic ocean crust during early Tertiary orogenesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00373572
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  • 8
    Electronic Resource
    Electronic Resource
    Sulfides, oxides and sphene in high-pressure schists from New Caledonia (1985)
    Springer
    Contributions to mineralogy and petrology 91 (1985), S. 151-162 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract In the New Caledonia high-pressure schists pyrite, pyrrhotite, chalcopyrite, rutile and sphene are common phases while hematite and ilmenite are rare and magnetite is absent. The parageneses of these minerals were clarified from their occurrence as inclusions in garnet, from phase relations in the Cu-Fe-S and Fe-Ti-O-S systems, and from phase rule considerations for the multi-component system. The sulfur fugacity estimated for pelites and basites containing pyrrhotite, pyrite and rutile increased with increasing metamorphic grade; the oxygen fugacity in these schists was less than 10−27.6 bars at 400° C, 10 kb and 10−22.3 bars at 500° C, 11 kb. Among the other components of the metamorphic fluid in pelites, H2O was major, CH4, CO2 and H2S minor, and H2, CO, COS and SO2 rare. The fluid composition altered with advancing metamorphic grade, such that H2O decreased while CO2, CH4 and H2S increased, and this change was linked to concurrent massive decarbonization in the rock matrices.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377762
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  • 9
    Electronic Resource
    Electronic Resource
    Lawsonite-albite schists from northernmost New Caledonia (1970)
    Springer
    Contributions to mineralogy and petrology 25 (1970), S. 185-202 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract In the Boat Pass-Tiebaghi area of New Caledonia regional metamorphism of Cretaceous-Eocene sediments and volcanics is related to intrusion of large peridotite bodies along a well-defined west coast tectonic line. Three metamorphic zones have been mapped, passing eastwards from the ultramafic line: aragonite-lawsonite, calcite-lawsonite, and calcite-lawsonite-glaucophane. The relationship between structure, stratigraphy and metamorphic zones is simple; assemblages indicative of the highest ratio of pressure to temperature (aragonite-lawsonite zone) lie immediately adjacent to the intrusive peridotites and also occupy stratigraphically the highest position of all three metamorphic zones. Albite-bearing assemblages persist in all zones and spessartine and omphacite appear in the deepest zone (calcite-lawsonite-glaucophane). The high pressure mineralogy was developed by fluid overpressure generated from a normal to steep geothermal gradient within a sealed environment beneath the tectonically-emplaced peridotite plate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00371130
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  • 10
    Electronic Resource
    Electronic Resource
    Comparison of the high-pressure schist belts of New Caledonia and Sanbagawa, Japan (1982)
    Springer
    Contributions to mineralogy and petrology 79 (1982), S. 219-229 
    Details
    ISSN: 1432-0967
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract The high-pressure schist terranes of New Caledonia and Sanbagawa were developed along the oceanic sides of sialic forelands by tectonic burial metamorphism. The parent rocks were chemically similar, as volcanic-sedimentary trough or trench sequences, and metamorphic temperatures in both belts were 250° to 600° C. From phase equilibria curves, total pressures were higher for New Caledonia (6–15 kb) than for Sanbagawa (5–11 kb) and the estimated thermal gradients were 7–10° C/km and 15° C/km respectively.PT paths identify the higher pressure in New Caledonia (P differences 2 kb at 300° C and 4 kb at 550° C) with consequent contrast in progressive regional metamorphic zonation for pelites in the two areas: lawsonite-epidote-omphacite (New Caledonia) and chlorite-garnet-biotite (Sanbagawa). In New Caledonia the Na-amphibole is dominantly glaucophane and Na-pyroxenes associated with quartz are Jadeite (Jd95–100) and omphacite; in Sanbagawa the amphibole is crossite or riebeckite and the pyroxene is omphacite (Jd50). For both areas, garnet rims show increase in pyrope content with advancing grade, but Sanbagawa garnets are richer in almandine. Progressive assemblages within the two belts can be equated by such reactions as:New Caledonia Sanbagawa glaucophane+paragonite+H2O⇌albite+chlorite+quartz glaucophane+epidote+H2O⇌albite+chlorite+actinolite and the lower pressure Japanese associations appear as retrogressive phases in the New Caledonia epidote and omphacite zones. The contrasts inPT gradient, regional zonation and mineralogy are believed due to differences in the tectonic control of metamorphic burial: for New Caledonia, rapid obduction of an upper sialic plate over an inert oceanic plate and sedimentary trough; and for Sanbagawa, slower subduction of trench sediments beneath a relatively immobile upper plate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01132889
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