Abstract
Zeolites found in the Late Cenozoic marine sediments of the Japanese oil producing regions are widely distributed in a vertical zonal arrangement. The zeolitization in these sediments is studied at eleven deep wells drilled in the regions. The strata in these wells have been deposited continuously under the marine environments until the Recent.
The zeolite and albite zones are present at the various depth, and are oblique to the stratigraphic datums. The subsurface temperature at the top of each zeolite zone ranges from 42°C to 60°C for the clinoptilolite zone, 64°C to 112°C for the analcime zone, and 124°C to 152°C for the albite zone.
From consideration of burial and thermal histories in these wells, the transformation temperature of the alkali zeolite reaction series decreases gradually with increase in geological time elapsed since sedimentation, and/or with increase in the effective heating time of HOOD and CASTANO (1975). For exsample, clinoptilolite is transformed into analcime at 62°C for the effective heating time of 5Ma, and at 105°C for 0.5Ma, approximately.
The zeolitization is governed by not only the maximum temperature but also by the geological reaction time under the marine enviroments saturated with the sufficient cations (Na+) in interstitial water.
