『Abstract
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 ＜5μm, whereas on slates the weathering has
produced of ca. 1μm 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
oxy-hydroxides 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.
Keywords: Weathering; Porosity; Mass balance; Granodiorite; Slates;
Piedmont surfaces』
Introduction
Materials, methods and techniques
Materials
Methodology
Techniques
Results
Profile on granodiorite
Profile on slates
Discussion
Conclusions
Acknowledgments
References