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 Å 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 Fe-rich 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 sea-mount a potential terrestrial analogue for Mars surface exploration.

Adsorption of nucleotides onto ferromagnesian phyllosilicates: Significance for the origin of life

“…These phyllosilicates are aluminum-rich and unlikely to be abundant in the primitive altered oceanic crust of the Hadean. The Hadean seafloor was mainly formed of mafic and ultramafic rocks, such as basalt, komatiite and peridotite, which hydrothermal alteration has been widely studied through (i) petrological and mineralogical observations of samples collected in oceanic hydrothermal settings (Alt and Honnorez, 1984;Buatier et al, 1993;Hunter et al, 1999;Buatier et al, 2001;Alt and Teagle, 2003;Dias and Barriga, 2006;Lackschewitz et al, 2006;Mas et al, 2008); (ii) experimental alteration of bulk rocks (Humphris, 1978;Mottl and Holland, 1978;Mottl et al, 1979;Seyfried and Bischoff, 1979;Seyfried and Dibble, 1980;Seyfried and Bischoff, 1981;Seyfried and Mottl, 1982;Marcaillou, 2011;Lazar et al, 2012); and (iii) mineral evolution (Hazen et al, 2008;Hazen and Sverjensky, 2010;Hazen, 2013;Hazen et al, 2013). All above studies suggested that Fe-Mg rich phyllosilicates along with various oxides, hydroxides, anhydrites and sulfides are the major alteration minerals formed.…”

A natural analogue for CO2 mineral sequestration in Miocene basalt in the Kuanhsi-Chutung area, Northwestern Taiwan

“…However, because this unknown hydrous mineral is enriched with iron in EMP analysis and associated with iron-rich saponite, it may be a ferric rich member of smectite, nontronite. Nontronite can be produced by saponite oxidation; however, it is still an undetermined mineral and is named as nontronite-like mineral in this study (Mas et al, 2008). Conclusively, dolomite, magnesite, diopside and spinel can only be identified by EMP although there are suspicious peaks in some cases; the chemical variation of carbonates are also mainly determined by EMP; and calcite, saponite, mica, serpentine, forsterite and enstatite show observable signals in XRD.…”

The Fe-Rich Clay Microsystems in Basalt-Komatiite Lavas: Importance of Fe-Smectites for Pre-Biotic Molecule Catalysis During the Hadean Eon

“…Mas et al (2008) show that subaerial, submarine lava flows and dyke exhibit all chilled thin vitreous margins ( Fig. 2a) contrasting with a thick inner part which is highly crystallized (Fig.…”

“…The average size of mesostasis micro-settings can be represented by a square of 50 µm side. According to Mas et al (2008), there are about 50 to 100 sites observable on a single thin section of Mururoa basalt (30×40 mm). In other words, 8 × 10 4 to 16 × 10 4 clay micro- settings per square meter are outcropping on any surface crosscutting the crystallized inner parts of the basalt lava bodies.…”