Sudoite in some Visean (Lower Carboniferous) K-bentonites from Belgium

Abstract

Sudoite occurs as a cryptocrystalline clay in some Visean K-bentonites from Belgium. Usually associated with illite-smectite mixed-layers, this chlorite has been found locally as a monomineralic clay component of a K-bentonite bed. The mineral has a composition close to (A13Mg2)(Si3AI)OI0(OH)s. The cell parameters have been calculated from the diffractogram using the space group C2/m (a = 5.228, b = 9-056, c = 14.326 A,/3 = 97~ ', d(060) = 1.509 A). The polytype corresponds to a llb structure. Some hypotheses are proposed for the origin of this chlorite. The coexistence of sudoite and pyrite could explain why the chlorite present in Visean K-bentonites is not a Fe-rich species typical of diagenetic conditions, but a Fe-poor one.

Geochemistry and origin of Carboniferous (Mississippian; Viséan) bentonites in the Namur-Dinant Basin, Belgium: evidence for a Variscan volcanic source

“…5). The type(s) of chlorite cannot be determined from the whole-rock powder XRD data, but AlMg-rich chlorites including sudoite and clinochore have been reported from some of the 'W' bentonites at Anhée Nord (Anceau, 1992(Anceau, , 1996. The transitional nature of the change in K 2 O/Al 2 O 3 , MgO/Al 2 O 3 and clay mineralogy between bentonites W6 and W8 may record a short-term change in ash composition.…”

“…The clay mineralogy varies laterally and vertically, both within a single bentonite and between different bentonites (Thorez & Pirlet, 1979;Anceau, 1992Anceau, , 1996. Thorez & Pirlet (1979) noted that the clay mineral assemblages are consistent with the early diagenetic alteration of volcanic ash in a marine environment, although some modification during burial diagenesis cannot be excluded as Mississippian strata within the basin have experienced temperatures of up to c. 250 °C based on illite crystallinity and conodont alteration indices (Helsen & Kønigshof, 1994;Han et al, 2000).…”

“…Thorez & Pirlet, 1979). Their mineralogy has been studied previously (Thorez & Pirlet, 1979;Delcambre, 1989;Anceau, 1992Anceau, , 1996 and is only summarised here. The bentonites comprise mostly polymineralic clays, including mixed-layer clays (illite/ Sedimentation areas are redrawn from Poty (2016;not palinspastic).…”

“…smectite, illite/vermiculite, illite/chlorite), illite, kaolinite and/ or Al-rich chlorites (Thorez & Pirlet, 1979;Anceau, 1992Anceau, , 1996. The clay mineralogy varies laterally and vertically, both within a single bentonite and between different bentonites (Thorez & Pirlet, 1979;Anceau, 1992Anceau, , 1996.…”

Dioctahedral Tosudite in Hydrothermally Altered Pliocene Rhyolitic Tuff, Neutla, Mexico

“…Minerals described with trioctahedral or di,trioctahedrat layers include tosudite, a regular interstratification of di,trioctahedral chlorite-montmoriltonite (Sudo and Kodama, 1957;Shimoda, 1975); a di,trioctahedral chlorite-montmorillonite associated with iron ores in Michigan (Bailey and Tyler, 1960); sudoite from Ottre, Belgium, with a dioctahedral 2:1 layer plus a trioctahedral interlayer (Bailey and Brown, 1962;Eggleton and Bailey, 1967;Fransolet and Bourguignon, 1975;Cheng-Yi and Bailey, 1985); sudoite in the Visean K-bentonites from Anh6e, Belgium (Anceau, 1992); Li-cookeite (Bailey and Brown, 1962); and donbassite (Drits and Lazarenko, 1967). Less common are those containing only dioctahedral layers, among which the best known mineral is di,dioctahedral tosudite (Sudo et al, 1954;Sudo and Hayashi, 1956;Sudo and Kodama, 1957;FrankKamenetsky et al, 1965;Shimoda, 1969;Imai and Watanabe, 1972;Furbish, 1975); and those containing Li in the gibbsitic interlayer (Nishiyama et al, 1975).…”