Hydrothermal alteration at Mururoa Atoll (French Polynesia)

Dudoignon, P.; Meunier, Alain; Beaufort, Daniel; Gachon, A.; Buigues, D.

doi:10.1016/0009-2541(89)90106-x

Cited by 23 publications

(17 citation statements)

References 24 publications

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“…Three types of hydrothermal alteration, based in part on stable isotope systematics, have been recognized in the altered basalts from the Mururoa and Fangataufa atolls (Dudoignon et al, 1989(Dudoignon et al, , 1992Destrigneville et al, 1991): submarine (sea water/ basalt interaction; exemplified in the present study by Mururoa submarine lava flows), subaerial (meteoric water/basalt interaction; Mururoa subaerial lava flows) and hydrothermal (magmatic fluid/basalt interaction; exemplified by Fangataufa intrusives). The subaerial and submarine alterations differ from processes related to low temperature weathering or sea water alteration.…”

Section: Petrography and Alterationmentioning

confidence: 71%

“…The altered flows have distinct mineralogy and abundant secondary phases. The alteration assemblage is controlled by the rock/ fluid interaction (Dudoignon et al, 1989). The submarine flows were modified by interaction with sea water which led to crystallization of saponites at about 80~ (O and H isotope data;Dudoignon et al, 1989Dudoignon et al, , 1992.…”

Section: Petrography and Alterationmentioning

confidence: 99%

“…The alteration assemblage is controlled by the rock/ fluid interaction (Dudoignon et al, 1989). The submarine flows were modified by interaction with sea water which led to crystallization of saponites at about 80~ (O and H isotope data;Dudoignon et al, 1989Dudoignon et al, , 1992. Slightly altered inner parts of flows contain 'protoceladonite' and Fe-saponite assemblages which fill vesicles and replace glass and olivine.…”

Section: Petrography and Alterationmentioning

confidence: 99%

“…Petrographic investigation by Dudoignon et al (1989) revealed that the drill core material is variably altered. The samples were analyzed for a range of incompatible trace elements including B, Be, Li, U, Th, Pb, rare earth elements (REE), Nb, Ta, Zr, Hf, Ba, Sr, Rb and Cs (Table 1).…”

Section: Introductionmentioning

confidence: 99%

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Distribution of boron, lithium and beryllium in ocean island basalts from French Polynesia: implications for the B/Be and Li/Be ratios as tracers of subducted components

1996

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The study focuses on the distribution of B, Be, Li, rare earth elements (REE), high-field-strength elements (HFSE), Th, U and Pb in fresh and hydrothermally altered ocean island basalts (OIB) from French Polynesia, and evaluates B/Be and Li/Be ratios as potential tracers of subducted components in the mantle. Hydrothermal solutions affecting the rocks during cooling were derived from meteoric water, sea water and magmatic fluids. The concentrations of REE, HFSE, Th and Be in the OIB were not affected by secondary processes except during advanced stages of subaerial hydrothermal alteration where saponite was a dominant secondary phase. This alteration modified the contents of these elements, changed REE patterns and produced a positive Ce anomaly. The subaerial and submarine hydrothermal alteration (T ~ 70-100~ may change U concentrations in OIB, whereas Pb was only marginally redistributed during alteration.Boron was enriched during submarine and subaerial hydrothermal alteration but was not noticeably affected in basalts altered by magmatic fluids at T > 200~ Like B, the mobility of Li during the alteration varies with fluid temperature. Lithium became enriched in the basalts during advanced stages of lower T hydrothermal alteration (<100~ However, this element was partly removed from the rocks during higher T alteration (>200~ by magmatic fluids. Boron, Be and Li behave as incompatible trace elements in basaltic magmas. Beryllium content in primitive mantle is estimated to be 0.07 ppm. Fresh Polynesian OIB have low abundances of B and Li and low B/Be (2-5) and Li/Be (2.5-5) ratios compared with volcanic arc rocks, marine sediments and altered oceanic crust. Various OIB including even those which have HIMU-and EMaffinities have similar overlapping B/Be and Li/Be ratios. Both B and Li are probably stripped from a lithospheric slab during subduction-related metamorphism and are, thus, not involved in deep mantle recycling. The mantle-normalized trace element abundances of MORB and OIB usually display patterns characterized by negative B, Pb and Li anomalies. The patterns of continental crust and crustal rocks have distinct positive anomalies for these elements whereas continental basaltic rocks have variable relative abundances of B, Pb and Li. The anomalies of these elements in basalts can be useful in discriminating their tectonic setting and constraining the mantle source regions of basalts.

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Section: Petrography and Alterationmentioning

confidence: 71%

Section: Petrography and Alterationmentioning

confidence: 99%

Section: Petrography and Alterationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Distribution of boron, lithium and beryllium in ocean island basalts from French Polynesia: implications for the B/Be and Li/Be ratios as tracers of subducted components

1996

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“…7). At known temperature, the equilibrium system exists as a closed system whereas, pressure affects the equilibrium state but, on a minor scale under near surface conditions [59,60]. The temperature -activity and temperature -fugacity relations shows the effects of temperature on the stability of minerals and the predominance of aqueous species in the chemical systems.…”

Section: Fig (8) Eds Spectra Of Nuclear Waste Glass (Avs)mentioning

confidence: 99%

Corrosion Mechanism in the Obsidian and its Comparison with the Nuclear Waste Glass for Long-Term Performance Assessment in the Geological Repository~!2009-08-04~!2009-10-08~!2010-03-16~!

Rani¹,

Shrivastava²,

Bajpai³

2010

TOCORRJ

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Present paper discusses experimental work on obsidian glass to understand corrosion mechanism at variable pressure temperature conditions. For comparison, Advanced Vitrification System, a nuclear waste glass was studied simultaneously under similar conditions. Owing to massive weight loss the glass samples were unable to sustain beyond 4 hour during the experiments. Corrosion experiments on both these glasses were performed under hydrothermal like conditions and observed that the changes in the experimental conditions have major control over the release of sodium and other ions from obsidian and nuclear waste glass, hence effecting corrosion mechanism. X-ray diffraction patterns of the residue obtained after the experiments on obsidian glass revealed appearance of neo-formed minerals, such as quartz, celadonite, halloysite, sodalite, heulandites and wairakite. High degree of corrosion and formation of amorphous residue observed in case of the experiments performed at 300 0 C over the granules of the nuclear waste glass. The back scattered electron images of the scanning electron microscope indicate distinctive microstructures, associated with the neo-formed minerals, and their formation is linked with the release of sodium, potassium and other ions, causing changes in the pH and conductivity of the leachate. In case of nuclear waste glass back scattered images of the scanning electron microscope indicates formation of multiple alteration layers and secondary alteration products. The surface of the pellet after the experiment shows phyllosilicate with numerous tiny spherules embedded within the structure. These experimental results when extrapolated suggest formation of amorphous silica, quartz and chalcedony as end members in case of obsidian glass whereas, formation of iron rich fayalite and greenalite can be observed in case of nuclear waste glass. The mechanism, conditions of formation of neo-formed minerals and their stability have been discussed in the paper.

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Hydrothermal alteration associated with rift zones at Fangataufa atoll (French Polynesia)

Dudoignon

Proust

Gachon

1997

Bulletin of Volcanology

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The Mururoa and Fangataufa atoll basement consists of superimposed submarine and subaerial lava flows which have been intruded by late volcanics. The intrusions have developed large hydrothermal alteration haloes throughout the basaltic wall rock. The cuttings of the Natice-1 and Mitre-1 holes, drilled into the submarine volcanic pile at Fangataufa atoll, show a vertical zonation of clay minerals ranging from 270 to 850 m depth. The newly formed clay minerals occurring from top to bottom of the altered pile are: dioctahedral aluminous smectites, saponite, an intimate assemblage of saponite with two random chlorite/saponite mixed layers and an intimate assemblage of one random chlorite/saponite mixed-layer with one ordered chlorite/saponite mixed layer and one chlorite below 816 m depth. These clay mineral assemblages indicate a general increase in the chloritic component with depth. They are associated throughout the pile with secondary carbonates and quartz. The u 18 O and u 13 C of calcite and u 18 O of clay minerals, on the one hand, and the intimate mixtures of trioctahedral species, on the other, suggest a general cooling with the evolution of a paleogeothermal gradient from approximately 300 7C/km during the crystallization of chlorite to 150 7C/km for the late calcite precipitation.

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Hydrothermal alteration at Mururoa Atoll (French Polynesia)

Cited by 23 publications

References 24 publications

Distribution of boron, lithium and beryllium in ocean island basalts from French Polynesia: implications for the B/Be and Li/Be ratios as tracers of subducted components

Distribution of boron, lithium and beryllium in ocean island basalts from French Polynesia: implications for the B/Be and Li/Be ratios as tracers of subducted components

Corrosion Mechanism in the Obsidian and its Comparison with the Nuclear Waste Glass for Long-Term Performance Assessment in the Geological Repository~!2009-08-04~!2009-10-08~!2010-03-16~!

Hydrothermal alteration associated with rift zones at Fangataufa atoll (French Polynesia)

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