Weathering of Serpentinite in Matanzas Province, Cuba: Mass Transfer Calculations and Irreversible Reaction Pathways

Abstract

AbstractWeathering processes of serpentinite rock in the Province of Matanzas, Cuba, were studied by means of detailed mineralogical and chemical analyses of three pedons in a toposequence. The observed mineralogical composition was compared with that predicted theoretically by mass transfer calculations.All soils are extremely rich in ferric oxides. The lowest, poorly drained soil, a Gleysol, is smectitic and contains carbonates (magnesite and siderite). Its subsoil appears to meet the requirements for application of the model most closely. Here weathering proceeds at high CO2 concentrations leading to the formation of siderite, magnesite, smectite, and amorphous silica. Reduction of colluvial goethite to siderite may be involved also. Carbonates are lacking in the two well‐drained soils (Chromic Cambisols) which contain appreciable kaolinite in addition to smectite. This agrees with the stronger leaching at the well‐drained sites. Yet, the presence of amorphous silica implies that the rate of leaching only slightly exceeds the rate of weathering.Published water analyses from serpentinite areas are in good agreement with the water composition predicted by the model.