地熱地帯下部で形成されたChlorite-Montmorillonite系鉱物のタイブ分け試案

抄録

By X-ray diffraction analyses at dry (low humidity) condition and ethylene glycol treatment, chlorite-montmorillonite series minerals formed at the depth of Onikobe and Hakone geothermal areas can be divided into the following seven types:
I: Alkaline montmorillonite
I': Non or low alkaline montmorillonite (smectite)
I'': Mixture of I and I'
II: Mixture of I and IV
III: Mixture of I' and IV
IV: Mixed layer mineral chlorite/smectite
V: Chlorite
Chlorite-montmorillonite series minerals generally change by the order of I, I', I''
→II, III→IV→V with increasing depth and increasing temperature.
Among these types of clay minerals, I, I', IV and V types are most commonly observed and minerals of types I'', II and III are rare, indicating that most of chlorite-montmorillonite series minerals were formed at equilibrium conditions in the depth of these geothermal areas.
As far as judged from X-ray diffraction data, there seem to be gaps between type I and type I', between type I and type IV and between type I' and type IV.
The above-noted typology can well be correlated to the Kristmanndóttir's classification of clay minerals in Icelandic geothermal areas, although the mineralogic problem related to the so-called swelling chlorite still remains unsolved.