Origin and evolution of smectites in Recent marine sediments of the NE Atlantic

Abstract

A B S T R A C T : Present-day marine sediments around the emerged basaltic areas of Iceland and the Faeroe Islands are characterized by the abundance and predominance of smectites. Smectites increase regularly and systematically near volcanic areas. Their origin from (i) meteoric/ deuteric weathering, (ii) hydrothermal products, (iii) neoformation in the marine environment or (iv) transformation during their transport to or stay in oceanic regions is considered in a comparative study of three types of environments on or near the Faeroe Islands. These are (1) a basaltic environment where phyllite minerals of deuteric and hydrothermal origin are abundant; (2) a soil environment formed on basaltic flows; (3) a marine sedimentary environment within adjacent sedimentary basins. This investigation clearly shows the link between hydrothermal and deuteric saponite--celadonite in basalt, Fe,Mg-smectite in Faeroe soils and Fe-smectite in marine sediments.A question often considered by geologists (e.g. Yeroshchev-Shak, 1964;Griffin et al., 1968;Rateev et al., 1969) is the abundance, and often predominance, of smectite in clay assemblages within the Icelandic Basin of the N Atlantic. There is general agreement that smectites increase near the emerged basaltic areas of Iceland and the Faeroe Islands. This increase appears to be constant and characterizes Quaternary sedimentation in the NE Atlantic both during the glacial and interglacial periods (Parra, 1980;Zimmerman, 1982). Much controversy exists, however, about the location of supply provinces. YeroshchevShak (1964), for instance, suggests on the basis of the disposition of smectite haloes surrounding Iceland that smectites derive from oceanic basaltic rocks, whereas Biscaye (1965), Griffin et al. (1968) and Rateev et al. (1969) imply that they originate from continental areas.Results of more recent investigations imply a positive correlation between the basaltic character of detrital inputs (supplied by the Iceland-Faeroe region) and the abundance of smectites (Zimmerman, 1975;Parra, 1982). Near Iceland, smectites represent almost 100% of the clay mineral assemblage (Grousset et al., 1982;Grousset, 1983).Pedologic studies have shown that some smectites form by meteoric weathering of a variety of rock types under certain very specific climatic conditions, namely those of tropical reducing environments (Pedro, 1966). This, of course, is not the case for the Quaternary Iceland-Faeroe province which has a cold and humid climate in which pedogenesis is relatively inactive; the soils are thin and poorly developed and characterized 9 1985 The Mineralogical Society

Smectite composition as a tracer of deep circulation: the case of the Northern North Atlantic

“…Montmorillonite and beidellite (Al end-member) mostly result from the chemical weathering of diverse substrates under a wide spectrum of environmental conditions. Fe-beidellites and nontronites (Fe end-member) commonly derive from meteoric weathering or hydro-thermal alteration of basalts; they are particularly abundant in active areas of mid-oceanic ridges (Haggerty and Baker, 1967;McMurthy et al, 1983;Parra et al, 1985Parra et al, , 1986.…”

Mineralogy of Firm Muds and Mudstones Associated with Volcanosedimentary Layers from the Tyrrhenian Sea, Holes 650A and 651A, ODP Leg 107

“…But they may also correspond to a transition towards a chloritic structure (Chamley et al, 1985). Concerning the potassic-ferriferous beidellites from Hole 650A, a part of them might have resulted from re-equilibration, on the seafloor, of detrital smectites derived from the continent but, a large proportion of this mineral most likely represents the endmember equilibrium phase of a submarine transformation of the Fe, Mg smectites (Parra et al, 1985). The affinity for K of the dioctahedral smectites with replacement in the tetrahedral layer explains their enrichment with regards to this element (RicoGamboa, 1984).…”

“…The high proportion of exchangeable interlayer potassium in smectites of the firm muds is substantiated by the quantities of this element extracted by the acid ammonium oxalate reagent ( Table 2). Beidellites of this type have been described by Desprairies (1981) and Parra et al (1985).…”

“…In the high frequencies field one observes only an absorption band at 3620-3625 cm -1 besides the strong adsorption band near 3420 cm _1 (interlayer H 2 0 vibration). The characteristic bands of saponite or Fe saponite layers at 3550 and 3678 cm -1 (Farmer, 1974;Van der Marel and Beutelspacher, 1976;Parra et al, 1985) are not present. This fact and the absence, in the low frequencies field, of absorption bands at 685 cm -1 and toward 650 cm -1 shows that the smectites, for the most part or in totality, correspond to a beidellite-type mineral (Parra et al, 1985).…”

Clay mineralogy, strontium and neodymium isotope ratios in the sediments of two High Arctic catchments (Svalbard)

“…Basalt typically weathers to smectite group minerals (e.g. Curtin and Smillie, 1981;Parra et al, 1985) and modern sediments originating from Siberia (basaltic) are enriched in smectite (Nürnberg et al, 1994;Wahsner et al, 1999). Any volcanic particles present will also tend to weather to smectite (Bayon et al, 2015).…”