Abstract
Vaterite in association with calcite, small quantities of portlandite and ettringite group mineral was found from cuttings of MITI-borehole (Sado-oki) that was carried at offshore of Sado Island, the Sea of Japan. Stratigraphic horizon including vaterite correlates to the Uonuma Group of Pleistocene age.
Lumps containing vaterite are about 10 mm along with elongation. They are white in color and look like volcanic ash. This characteristic appearance is same to ones described in the previous papers that reported vaterite in cuttings. The studied lumps show flat and/or angular shape, and conchoidal fracture. Those appearances suggest that the lumps may be stripped from solid material.
An intensity of peak of vaterite in X-ray powder diffraction pattern has gradually increased by repeat experiments, which suggests that crushing of a lump and mixing with air may cause crystallization of vaterite.
The presence of portlandite and ettringite-group mineral suggests thatformation of vaterite may have relationship with cement material for drilling of oil well.
