GEOCHEMICAL CHANGES ACCOMPANYING BASIC IGNEOUS ROCKS—CLAY TRANSITION IN A HUMID MEDITERRANEAN CLIMATE

Abstract

Geochemical changes accompanying the weathering of basalt, scoria, and tuff-lapilli into kaolinitic soil clays under the humid Mediteranean climate of the Upper Golan Heights were studied. The weathered rocks were considerably depleted in alkali and alkaline earth metals. From the clays these elements were nearly completely eliminated except for K, whose depletion was less complete. Molar SiO₂/Al₂O₃ ratios decreased from 4.7–7.7 in rocks to 3.2–4.6 in the clays. The mobility of the minor elements, assessed according to their depletion rate from the weathered rocks, was Sr > Mn, Cu > Co, Ni > Zn > Cr. The relative capacities of the minor elements to be retained in the clays were: Zn, Mn > Ni, Co, Cu > Cr, Sr.