The Nature of Vermiculite in Adirondack Soils and Till

Abstract

Abstract--The clay and bulk mineralogy of soil and till from 26 Adirondack watersheds was studied. The materials consist typically of quartz, K-feldspar, plagioclase, mica, vermiculite, and kaolinite. Talc, smectite, halloysite, and hornblende are present in some samples. The clay fraction of the soils is composed predominantly of vermiculite, likely derived from the transformation of a mica precursor, and kaolinite. The soil vermiculite commonly contains hydroxy-Al interlayers which are especially prevalent in the B-horizon samples. Despite significant variation in the type of bedrock and the composition of heavy mineral assemblages in these watersheds, the clay mineralogy is remarkably uniform. This finding supports earlier suggestions that the occurrence of vermiculite in soils is more dependent on climate than on the nature of the parent material.

Vermiculitization of Phlogopite in Metagabbro, Central Turkey

“…The origin of the trioctahedral variety of vermiculite remains unclear (Justo et al, 1986;de la Calle and Suquet, 1988;Zhelyaskova-Panayotova et al, 1992 whereas the dioctahedral variety is unquestionably accepted as the product of low-temperature surface weathering (Gruner, 1939;Hathaway, 1955;Barshad and Kishk, 1969;April et al, 1986;Graham et al, 1989;Moon et al, 1994). Experimental studies produced vermiculite as an alteration product of micas Toksoy-Krksal, Ttirkmeno~lu, and GOnciao~lu Clays and Clay Minerals owing to the effects of low-alkali solutions (Komarneni and Roy, 1981).…”

Chlorite Vermiculitization and Pyroxene Etching in an Aeolian Periglacial Sand Dune, Allen County, Indiana

“…For example, vermiculite forms in the A horizon at the same time hydroxy-A1 vermiculite forms in the deeper B horizons of certain Adirondack soils (April et aL, 1986). This distribution can be explained by the presence of organic acids (especially citric and oxalic acids formed under aerobic conditions) from the overlying leaf-litter that prevent the formation of hydroxy-Al interlayers in the vermiculites at near-surface depths (Vicente et aL, 1977;April et aL, 1986).…”

“…Hydroxy-A1 vermiculites form by intense weathering under acid conditions and are stable with respect to vermiculite (and possibly kaolinite) in many weathering horizons (Douglas, 1977). However, there are some exceptions and April et al (1986) suggested that organic acids from leaf litter, or the establishment of more aggressive weathering regimes, had remobilized hydroxy-A1 interlayers producing vermiculite in an Adirondack soil.…”

Supergene Vermiculitization of Phlogopite and Biotite in Ultramafic and Mafic Rocks, Central Korea

“…Many workers have studied this process by observing both naturally weathered micaceous minerals and mica altered artificially in the laboratory. Supergene vermiculitization of trioctahedral micas through intermediate stages ofinterstratified mica/vermiculite has been identified as one of the main mineral weathering sequences reported in the literature (Coleman et al, 1963;Rhoades and Coleman, 1967;Meunier and Velde, 1979;April et aL, 1986;Ildefonse et al, 1986;Banfield and Eggleton, 1988;Bain et aL, 1990;Fordham, 1990a). Vermiculite deposits at Cheongyang, South Korea, appear to be derived from both phlogopite in ultramafic and biotite in mafic intrusive rocks (Song et aL, 1990).…”