粘土鉱物とグリーンタフ変質

概要

論文の詳細を見る
Identification of clay minerals such as saponite, vermiculite and interstratified mineral in the Green Tuff have been very confusing. The WALKER'S test (solvating the magnesium saturated sample's with ethylene glycol) is very usefull to detect a character of vermiculite. Diagenetic changes of chloritic minerals depend upon the chemical compositions of the host rocks and the sedimentary environment. In basic pyroclastic sediments, Fe-rich saponite ("Al-saponite") seems to have been changed to Fe-Mg chlorite through the mixed-layer chlorite-saponite with advancing alteration grade. In acidic pyroclastic sediments, however, Fe-Mg chlorite seems to have been derived from Al-montmorillonite by adding of Mg and/or Fe under hydrothermal condition. Paragenesis of laumontite and chlorite and/or mixed-layer chlorite-montmorillonite are very common in the Green Tuff area. Lower stability limit of laumontite (1 Kb, 150℃ determined by LIOU is in accord with that of chlorite (1 Kb, 140'C) and is higher than the upper limit of montmorillonite (1 Kb, 100℃) estimated from natural occurrences.
日本地質学会の論文
1973-07-01