Abstract
The Saile bentonite-zeolite mine is located in the west-central portion of Luzon Island in the northern Philippines, close to the Zambales ophiolite. The mine and surrounding area is a suitable survey site for studying a natural analogue of bentonite-cement interaction. In the area, bentonite is in contact with alkaline groundwater, a situation analogous to cement leachates. The groundwater is generated and evolves mainly by low-temperature serpentinization in the ophiolite, and it flows along faults.
The bentonite influenced by alkaline groundwater in the survey area showed the following geochemical and mineralogical characteristics. Bentonite close to pillow basalts has high levels of Cr, Ni, and light-rare-earth elements because of increased alkaline interaction. An iron-concentration band and bentonite alteration zone containing Ca-zeolites and K-feldspar were formed at the contact interface with pillow basalts as a result of alkaline alteration. The width of the zone is 5 mm. However, bentonite is little altered at the outcrop scale because of clogging by alteration minerals.
