1 research outputs found
Importance of porosity and transfer of matter in the rock weathering processes: two examples in Central Spain.
14 p.Some physical properties (bulk and free
porosity, pore size distribution), and the chemical composition
and mass balance of two deeply weathered profiles
one developed on Hercynian granodiorite and the other on
pre-Cambrian slates were studied. Hydric and mercury
porosimetry, nitrogen adsorption techniques, chemical
analyses and XRD techniques were used. On granodiorite,
weathering has created increased porosity with a pore
diameter \5 lm, whereas on slates the weathering has
produced of ca. 1 lm in diameter. These pore sizes have
played an important role in the weathering processes.
Assuming that weathering preserves volumes, except in the
uppermost part of the profiles, it brought about a loss of
matter of more than 12% (*300 kg/m3) on granodiorite
and ca. 30% (*800 kg/m3) on slates. These changes are
related to shifts in the mineralogical evolution, with the
appearance of new 2:1 and 1:1 phyllosilicates and Fe oxyhydroxides
as the main authigenic minerals. The release of
matter, at least since the upper Neogene until the present,
has led to the lowering of relief in a more or less homogeneous
way, giving rise to gentle hillsides and flat surfaces
below which the current river networks are incised. Porosity studies have the potential to explain several
specific landforms as well as affecting landscape development
in general.The authors acknowledged the interesting suggestions
of Prof. C. R. TWIDALE. We also thank the Ministerio de
Educacio´n y Ciencia of Spain and the Junta de Castilla y Leo´n for
financial support under Projects CGL2007-62168/BTE (funds
FEDER) and Project SA024A07, respectively.10261/35212Peer reviewe