Clays and Clay Minerals, Vol. 56, No. 6, 711–729, 2008.
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Authors
Mas, Antoine
Meunier, Alain
Beaufort, Daniel
Patrier, Patricia
Dudoignon, Patrick
Issue Date
2008
Type
Article
Language
Keywords
Periodicals , Geology , Basalt , C-S , Celadonite , French Polynesia , Glass , Mesostasis , Mururoa , Nontronite , Vesicle
Alternative Title
Clay Minerals In Basalt-hawaiite Rocks From Mururoa Atoll (french Polynesia). I. Mineralogy
Abstract
Clay minerals in chilled or brecciated margins (altered glass) and massive inner crystalline parts (mesostasis) of three basalt-hawaiite bodies from Mururoa Atoll (French Polynesia) have been studied in order to compare their chemical and mineralogical compositions. Polyphase assemblages comprise di- and trioctahedral phases, both of which consist of non-expandable layers (chlorite, celadonite) and two types of expandable layers (saponite and Fe-rich smectite or ‘nontronite-like’ material). The presence of the Fe-rich clays is supported by the presence of the X-ray diffraction 060 peak at 1.51-1.52 A ˚ and of the infrared absorption bands at 875 and 822 cm-1 (Fe3+-Al-OH and Fe3+-Fe3+-OH groups, respectively). The chemical composition of the Fe-rich smectites does not fit with the theoretical nontronite field. The layer charge averages 1 per Si4O10 making these Fe-rich smectites close to ‘celadonite-type’ clays. This could explain the presence of mixed-layer celadonite-smectite. Plotted in an M+/4Si vs. Fe/sum octahedral cations diagram, the chemical compositions of clay minerals in the mesostasis form a continuous field limited by the celadonite-high-charge nontronite-like smectite and chlorite end-members. The clay assemblages are different from those formed in hydrothermal systems or low-grade metamorphic conditions which are characterized by the sequence: saponite?randomly ordered chlorite-smectite mixed-layered minerals (MLMs)?corrensite?chlorite. The systematic presence of Ferich clays either in the altered chilled margins or in the massive inner parts of the basalt-hawaiite bodies (high-charge nontronite-like smectite and mixed-layer nontronite-celadonite) makes the Mururoa seamount a potential terrestrial analogue for Mars surface exploration.
Description
gsccm56611-mas.pdf - 1,682KB
Citation
Clays and Clay Minerals, Vol. 56, No. 6, 711–729, 2008.
Publisher
The Clay Minerals Society
License
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