Naslov
Corrensite in metabasalts and metagabbros from Mt. Medvednica, Croatia

Autori
Judik, Katalin ; Németh, Tibor ; Tibljaš, Darko ; Horváth, Péter ; Árkai, Péter

Izvornik
Acta mineralogica-petrographica (0365-8066) 44 (2003); 1-8

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
corrensite; smectite-to-chlorite transition; hydrothermal metamorphism; weathering

Sažetak
Complex mineral paragenetic and mineral structural and -chemical studies were carried out on metabasite samples from the ophiolitic mélange unit of Mt. Medvednica, Croatia using petrographic microscopic, XRPD and EMP techniques. According to XRPD studies of the <2 &micro ; m and < 0.6 &micro ; m grain-size fractions, chlorite and corrensite (regularly interstratified chlorite/smectite) are the predominant phyllosilicate components. Randomly interstratified chlorite/smectite and discrete smectite are also found in minor amounts. On the basis of the EMP analyses chemical composition of "chloritic materials" from different textural positions reveals that they contain not only chlorite layers but certain amount of trioctahedral smectite (saponite) interlayers also occur being responsible for their relatively high Ca and/or Na contents, large excess of Al(VI) relative to Al(IV) and high octahedral vacancy. The formation temperature of the "chloritic materials" is suggested to be in the range of ca. 160-200 &ordm ; C using the geothermometer of Cathelineau (1988). Metabasalt samples from the ophiolitic mélange could be affected by minimum alteration, and the appearance of corrensite, together with mixed-layered chlorite/smectite and discrete smectite suggest "intermediate" temperature conditions (Shau and Peacor, 1992). According to Proust (1982) and Proust et al. (1986) corrensite as chlorite/vermiculite forms as an intermediate product of the weathering but the occurrence of chlorite/smectite in the studied samples may indicate that rather the diagenetic-incipient metamorphic alteration is the process that may be the main mechanism responsible for its formation.

Izvorni jezik
Engleski

Znanstvena područja
Geologija

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