TY - JOUR

T1 - Mineralogy and pore space characteristics of traprocks from Central Siberia, Russia

T2 - Prerequisite of weathering trends and soil formation

AU - Lessovaia, Sofia

AU - Dultz, Stefan

AU - Goryachkin, Sergey

AU - Plötze, Michael

AU - Polekhovsky, Yury

AU - Andreeva, Natalia

AU - Filimonov, Alexey

N1 - Funding information: This study was supported by the Russian Foundation for Basic Research ( 14-04-00327) , St-Petersburg State University ( 18.38.86.2012 ) and a grant from the DAAD through their fellowship program under contract number A/10/01109 (S. Lessovaia). XRD study of soils was carried out in the X-ray Diffraction Centre of St. Petersburg State University. The authors are grateful to Dr. Jock Churchman for helpful suggestions and discussions. We thank two anonymous reviewers for useful comments and corrections on the article.

PY - 2014/12/1

Y1 - 2014/12/1

N2 - Pore space issues and mineral paragenesis of traprocks from the central part of the basaltic province (Central Siberia, Russia) were studied, as was the fine size fraction (<. 1. μm) of well-drained soils from two groups - "shallow with hard rock" and "deeper and mature with saprolite." The explanation of coexisting of these two groups was given via rocks' characteristics.The methods used included mercury intrusion porosimetry (MIP), impregnation of connective pores with a molten alloy (Wood's metal) combined with subsequent electron microscopy, optical microscopy, X-ray diffraction, and IR spectroscopy.Rock from the lithic contact is represented by slightly weathered dolerite and shows a tendency to bimodal pore size distribution with a second maximum in pore size at 10. nm, which is due to the occurrence of phyllosilicates. Coarse pore systems are mainly due to cracks, which allow an easy exchange of water. Higher total porosity in the rock in one of two pits (~. 12. vol.% compared with 4. vol.%) appears to be a prerequisite for the formation of a deeper and more mature profile.Secondary products of dolerite weathering are smectites determining the association of clay minerals in both soil profiles and Fe-oxides. Most likely, desegregation and weathering of the rock fragments from soil horizons are fast enough to keep sufficient amounts of smectite only in the fine size fraction of the shallow profile. In the mature profile, pedogenesis leads to acidification of upper soil horizons and to a pronounced decrease in the smectite proportion, not only in the soil but also in the rock fragments from soil horizons. Thus, smectite(s) that was stable in early stages of rock weathering and soil formation and became unstable due to soil acidification illustrates the metastable nature of clay mineralogy in the well-drained soils from basic rock.

AB - Pore space issues and mineral paragenesis of traprocks from the central part of the basaltic province (Central Siberia, Russia) were studied, as was the fine size fraction (<. 1. μm) of well-drained soils from two groups - "shallow with hard rock" and "deeper and mature with saprolite." The explanation of coexisting of these two groups was given via rocks' characteristics.The methods used included mercury intrusion porosimetry (MIP), impregnation of connective pores with a molten alloy (Wood's metal) combined with subsequent electron microscopy, optical microscopy, X-ray diffraction, and IR spectroscopy.Rock from the lithic contact is represented by slightly weathered dolerite and shows a tendency to bimodal pore size distribution with a second maximum in pore size at 10. nm, which is due to the occurrence of phyllosilicates. Coarse pore systems are mainly due to cracks, which allow an easy exchange of water. Higher total porosity in the rock in one of two pits (~. 12. vol.% compared with 4. vol.%) appears to be a prerequisite for the formation of a deeper and more mature profile.Secondary products of dolerite weathering are smectites determining the association of clay minerals in both soil profiles and Fe-oxides. Most likely, desegregation and weathering of the rock fragments from soil horizons are fast enough to keep sufficient amounts of smectite only in the fine size fraction of the shallow profile. In the mature profile, pedogenesis leads to acidification of upper soil horizons and to a pronounced decrease in the smectite proportion, not only in the soil but also in the rock fragments from soil horizons. Thus, smectite(s) that was stable in early stages of rock weathering and soil formation and became unstable due to soil acidification illustrates the metastable nature of clay mineralogy in the well-drained soils from basic rock.

KW - Clay destruction

KW - Clay mineralogy

KW - Dolerite

KW - Shallow soils

KW - Silicate weathering

UR - http://www.scopus.com/inward/record.url?scp=84912138710&partnerID=8YFLogxK

U2 - 10.1016/j.clay.2014.09.039

DO - 10.1016/j.clay.2014.09.039

M3 - Article

AN - SCOPUS:84912138710

VL - 102

SP - 186

EP - 195

JO - Applied clay science

JF - Applied clay science

SN - 0169-1317

ER -