Geochemistry at DSDP Leg 60

The mineralogical composition of the volcaniclastic sediments (tuffs) is the same as that of the other associated sediments (mudstones). Diagenetic alterations are significant and seem to result from two processes.

The first (low-temperature alteration) develops with age and depth; it consists of the genesis of pure smectite, coupled with zeolites (phillipsite, clinoptilolite). The second is limited to sediments immediately overlying basalts and to the altered basalts themselves. It consists of the massive development of palygorskite, and seems to be linked with hydrothermal activity in the igneous basement.