Regularly Interstratified Montmorillonite-Chlorite in Basalt

Abstract

The dmninant clay mineral in an amygdaloidal basalt from Mozambique is a mixed-layer variety having a highly regular alternation of montmorillonite-like and chlorite-like layers. The montmorillonite-chlorite occurs in the amygdules as green rosettes having a fine fibrous structure.X-ray examination of this mineral shows a long spacing of about 29 A in air and a fairly well-developed sequence of basal spacings. The long spacing shows some variation which is dependent on the relative humidity of the air surrounding the sample. The montmorillonitelike layers expand with glycerol and contract with heat treatment similar to montmorillonite, while the chlorite-like layers show modified reflection intensities on beating similar to chlorite. The mineral shows a 31.7 A spacing when glycerol saturated and a 23.3 A spacing when fully dehydrated.

Chloritic Clay Minerals in Tuffaceous Sandstone of the Miocene Green Tuff Formation, Yamanaka District, Ishikawa Prefecture, Japan

“…In this study, the name is used for regularly interstratified chlorite-saponite. specimen Y-20 can be identified as a regular ly interstratified mineral of chlorite and saponite, and its mineralogical properties are closely similar to those of the regularly interstratified chlorite-montmorillonite re ported by Earley et al (1956) and the regularly interstratified chlorite-vermiculite by Bradely and Weaver (1956). As given in Tables 2, 3 * The name "swelling chlorite" has been used for a chlorite-like mineral showing expansion of 14 A reflection to 17.8 A one after treatment with glycerol as in the case of smectite (Stephen and MacEwan, 1951).…”

“…Earley et al (1956) maintained that such a specific term should be employed only for 1:1 regulr interstratification.…”

“…Magnesian chloritic clay minerals such as chlorite, swelling chlorite and interstrati fled clay mineral occur widely in sediment ary rocks, particularly in carbonate sedi ments (Honeyborne, 1951;Stephen and MacEwan, 1951;Lippmann, 1954;Earley et al, 1956;Bradely and Weaver, 1956;Peterson, 1961). They are also found in the altered zone of hydrothermal ore-deposites as gypsum and dolomite (Takahashi, 1959;Sugiura, 1962;Shimoda, 1970).…”

“…They are also found in the altered zone of hydrothermal ore-deposites as gypsum and dolomite (Takahashi, 1959;Sugiura, 1962;Shimoda, 1970). Further more, ferro-magnesian chloritic clay miner als occur in basic pyroclastic sediments of Miocene (Yoshimura, 1964(Yoshimura, , 1971Seki et al, 1969), and also occur as weathering products of basic rocks (Earley and Milne, 1955;Gallitelli, 1956;Nichols, 1970).…”

A regularly interstratified mineral of chlorite-montmorillonite in an altered andesite from Kinzan, Kagoshima prefecture.

“…It has been considered that these minerals were transformed from parent minerals to altered minerals under some environmental conditions. These minerals were found in the weathering products of chlorite (Johnson, 1964), of hornblende (Stephen and MacEwan, 1951), of ser pentines (Veniale and van der Marel, 1963), in the hydrothermally altered rocks (Sudo and Hayashi, 1955;Earley and Milne, 1956) and in the sediments (Honeyborne, 1951;Lippmann, 1954Lippmann, , 1956. Interstrati fied minerals of chlorite/montmorillonite are also found in altered andesites or pyroclastic deposits in green tuff region in Japan (Kimbara et al, 1971;Yoshimura, 1971).…”