Hydrothermal Synthesis of Corrensite: A Study of the Transformation of Saponite to Corrensite

Abstract

Abstraet~Hydrothermal synthesis experiments were conducted to study the transition from smectite to corrensite. A mixture of oxides with the bulk composition of corrensite--Na0~4(Si6.aAll.6)(Mg7.sA11:)-O20(OH)~0--was sealed in platinum capsules with 29-37 wt. % water. One set of samples was treated in cold-seal vessels at 500~ and 2 kbar for durations of 2, 3, 6, 12, and 24 h; the other set was treated at 350~ and 2 kbar for periods of 12 to 89 d. X-ray diffraction patterns (XRD) of oriented aggregates from treated products were obtained from ethylene glycol-solvated and air-dried preparations. Samples were also heated to 350~ either in a calibrated muffle furnace, removed and quickly placed in a nitrogen filled chamber on the diffractometer, or were heated at 350~ by using a calibrated heating stage mounted on the diffractometer.Initial mineral assemblages at both temperatures contained only saponite and serpentine. In experiments at 500~ saponite u'ansformed to corrensite within 6 h; in experiments at 350~ the transformation occurred as early as 22 d. Increased experiment times at both temperatures produced increasing amounts of well-crystallized corrensite, as indicated by several well-defined XRD peaks. No evidence of a randomly interstratified chlorite-smectite (C-S) precursor to corrensite was found. The identification of pure smectite, as opposed to highly-expanded randomly interstratified C-S, was possible only when clays were dehydrated on a heating stage on the diffractometer.These results call for a new examination of hydrothermally-altered basalt that has been reported to contain randomly interstratified C-S as an intermediate step in the reaction of smectite to corrensite or chlorite. These results also strengthen the view held by increasing numbers of investigators that corrensite should be regarded as a single phase, not as a mixed-layered phyllosilicate.

Mineral reactions associated with hydrocarbon paleomigration in the Huincul High, Neuquén Basin, Argentina

“…The absence of other intermediate mixed layers in the samples with corrensite suggests that corrensite crystallized directly and should be regarded as a discrete phase. In this context, smectite (saponite) transforms directly to corrensite with no intermediate randomly interstratified phase (Reynolds, 1988;Roberson, 1988;Beaufort et al, 1997;Roberson et al, 1999). In the Candeleros Formation, the continental depositional environment with arid climatic conditions (Garrido, 2010) would have favored, after Fe-oxide formation, precipitation of precursor Mg-rich smectite (Anjos et al, 2003;Worden and Morad, 2003) at relatively low temperature (≥20 °C; Roberson et al, 1999), from alkaline waters with high a Mg2+ (April, 1981;Anjos et al, 2003).…”

“…In this context, smectite (saponite) transforms directly to corrensite with no intermediate randomly interstratified phase (Reynolds, 1988;Roberson, 1988;Beaufort et al, 1997;Roberson et al, 1999). In the Candeleros Formation, the continental depositional environment with arid climatic conditions (Garrido, 2010) would have favored, after Fe-oxide formation, precipitation of precursor Mg-rich smectite (Anjos et al, 2003;Worden and Morad, 2003) at relatively low temperature (≥20 °C; Roberson et al, 1999), from alkaline waters with high a Mg2+ (April, 1981;Anjos et al, 2003). During burial, with increasing temperature (60-160 °C; Morrison and Parry, 1986;Hillier, 1993;Worden and Morad, 2003;Hillier et al, 2006;Vidal et al, 2012), the Mg-rich pore waters would have continued to react with the sediments, transforming the smectite into corrensite (April, 1981), as follows:…”

Clay minerals as alteration products in basaltic volcaniclastic deposits of La Palma (Canary Islands, Spain)

“…On the other hand, Aoudjit et al (1995), Ece et al (1999), Minato (2000) and others describe clay minerals formed by chemical weathering of volcanic debris. Moreover, Grauby et al (1994), Roberson et al (1999), Kloprogge et al (1999), Huertas et al (2000), Drief et al (2001), Ramirez et al (1998), Fiore et al (2001) and others, show examples of clay minerals synthesized in the laboratory.…”

“…Shau and Peacor, 1992;Schiffinan and Staudigel, 1994;Laveme et aI., 1996;All, 1999). Roberson et al (1999) stated that the alteration of basalts associated with hydrothermal fl uids provides excellent "natural laboratories" for the study of alteration products with fi ne grained phyllosilicates being the most character istic products of this process.…”

Chlorite, Corrensite, and Chlorite-Mica in Late Jurassic Fluvio-Lacustrine Sediments of the Cameros Basin of Northeastern Spain

“…However, corrensite and chlorite may also form by replacement of biotite Peacor, 1994a, 1994b;Li et al, 1998) and amphibole (Meunier et al, 1988), or by reaction between Mg-rich carbonate and dioctahedral clay minerals (Hutcheon et al, 1980;Hillier, 1993). In recent years it has been debated whether the transition from smectite to chlorite occurs as a continuous progressive transformation characterized by random and regular interlayering of different proportions of the end-member phases, as described by Bettison-Varga et al (1991), or if such transition is more accurately described as discontinuous steps between discrete sincerite, corrensite, and chlorite (Shau et al, 1990;Hillier, 1993Hillier, , 1995Schiffman and Staudigel, 1995;Roberson et al, 1999). Shau and Peacor (1992) suggested that the continuous transition occurs within incompletely recrystallized samples (i.e., those affected by relatively low fluid/rock interactions), whereas for higher fluid/ rock ratios the discontinuous transformation is favored, and only the discrete phases are present.…”