『Abstract
Black shale oxidative weathering plays a significant role in
a variety of processes including acid mine drainage and atmospheric
CO2 control. The modeling of weathering is
highly dependent o reactive surface area. In this study it is
shown that black shale oxidative weathering is regulated mainly
by the external, geometrical surface area of rock polyhedrons
and the organic matter's (OM) internal surface area. The internal
rock surface area decreases dramatically during OM dissolution
from 〜15 m2/g to 〜5 m2/g. A linear relationship
was found between the decrease of internal rock surface area and
quantity of OM dissolved. Optical roughness analyses of black
and bleached shale surface area reveal the formation of macropores
due to the dissolution of mesoporous and probably microporous
OM. However, due to deconsolidation, the geometrical external
rock polyhedron surface area increases during weathering. Black
shale polyhedrons show a doubling of their external surface area
as OM decreases. This provokes an increase of the shale volume
which is easily accessible by fluids. The increase of the external
rock surface area seems to be self-accelerating during weathering.
The upscaling of external and internal rock surface area evolution
during weathering presented in this study demonstrates the possible
application of these results to the improved understanding of
a chemical transport in a variety of natural systems.』
1. Introduction
1.1. Dissolution processes and the surface area quantification
of minerals and rocks
1.2. Surface area of rocks
1.3. Surface area evolution during weathering
2. Geological setting
3. Materials and methods
3.1. Petrographic observations
3.2. Black shale weathering succession and sample selection
3.3. Systematic method for surface area quantification
3.3.1. External surface area quantification
3.3.2. Internal surface area
4. Results ad discussion
4.1. Organic carbon content
4.2. External rock surface area
4.3. Internal rock surface area
4.4. Fluid-rock interfacial surface area evolution during black
shale weathering−Implications for reactive surface area
4.5. Generalizations
5. Conclusions
Acknowledgments
References
Appendix