Lichens play an unparalleledly vital role in weathering and soil-forming processes in Antarctic region. Inthis study some related chemical components and micromorphological analyses have been carried out on thesamples...Lichens play an unparalleledly vital role in weathering and soil-forming processes in Antarctic region. Inthis study some related chemical components and micromorphological analyses have been carried out on thesamples of the weathered rocks and the lichens grown on them from Fildes Peninsula, Antarctic. The resultsindicated that the major chemical components in the bioweathering surface layer of the sampled rocks havebeen obviously altered and the weathering potential in this layer has greatly decreased by an average rangearound 4.66 percent in 4 samples. In the weathering surface layer ferruginmation of some minerals in varyingdegrees was seen by means of microscopic examination through the thin section of the weathered rocks, andits products proved to be dominated by hematite, limonite, goethite and free iron oxides Meanwhile, thestudy suggested that the dissolntion and absorption of lichens by their secretion accelerated the process ofcalcitization of minerals in the bicaweathering surface layer. Eventually, the results aIso show that differentspeciesof lichens play different roles in weathering and soilforming processes.展开更多
This study was conducted to evaluate the weathering intensity of the major soils developed on igneous rocks in semiarid region of northwestern Iran.Eight parent materials were selected including monzodiorite,alkali gr...This study was conducted to evaluate the weathering intensity of the major soils developed on igneous rocks in semiarid region of northwestern Iran.Eight parent materials were selected including monzodiorite,alkali granite,granodiorite,syenite,pyroxene diorite,hornblende andesite,pyroxene andesite,and dacite.Representative soil profiles were described and soil samples were collected and analyzed for selected chemical and physical properties and total concentrations of major elements and Zr,V,Ti and Y.Bulk densities as well as Ti,Zr and V concentrations were used to estimate the strain factors and mass balance equations were used to quantify the net result of pedogenic weathering,i.e.elemental loss and gain.The results of clay content and pedogenic iron variability as well as index of compositional variability(ICV),chemical index of alteration(CIA) and,A-CN-K and MFW ternary plots showed that the soils developed on volcanic rocks(hornblende andesite> pyroxene andesite> dacite) were more weathered than those on the plutonic parent rocks(alkali granite,granodiorite,monzodiorite,syenite,pyroxene diorite).The results of mass balance calculations based on the strain factors revealed that the Ca and Na depleted during weathering progress mostly from plagioclase grains.In the semiarid regions Ca is precipitated as pedogenic calcite in the soil horizons.K and Mg depletion is less than Ca and Na especially in the profiles on the hornblende andesite with the highest clay and LOI content.The results of this study clearly suggest that the behavior of K and Mg during the weathering cannot only be explained by the disintegration of the primary minerals,since they are fixed on the secondary clay minerals.Iron did not change in the soils compared to the parent material and was precipitated as the pedogenic iron and conserved in the soil horizons.Overall,the results on the weathering indicators and major elements mass balance enrichment/depletion in the study area confirmed that the soil profiles developed on volcanic rocks are more weathered than those on the plutonic igneous rocks.展开更多
文摘Lichens play an unparalleledly vital role in weathering and soil-forming processes in Antarctic region. Inthis study some related chemical components and micromorphological analyses have been carried out on thesamples of the weathered rocks and the lichens grown on them from Fildes Peninsula, Antarctic. The resultsindicated that the major chemical components in the bioweathering surface layer of the sampled rocks havebeen obviously altered and the weathering potential in this layer has greatly decreased by an average rangearound 4.66 percent in 4 samples. In the weathering surface layer ferruginmation of some minerals in varyingdegrees was seen by means of microscopic examination through the thin section of the weathered rocks, andits products proved to be dominated by hematite, limonite, goethite and free iron oxides Meanwhile, thestudy suggested that the dissolntion and absorption of lichens by their secretion accelerated the process ofcalcitization of minerals in the bicaweathering surface layer. Eventually, the results aIso show that differentspeciesof lichens play different roles in weathering and soilforming processes.
文摘This study was conducted to evaluate the weathering intensity of the major soils developed on igneous rocks in semiarid region of northwestern Iran.Eight parent materials were selected including monzodiorite,alkali granite,granodiorite,syenite,pyroxene diorite,hornblende andesite,pyroxene andesite,and dacite.Representative soil profiles were described and soil samples were collected and analyzed for selected chemical and physical properties and total concentrations of major elements and Zr,V,Ti and Y.Bulk densities as well as Ti,Zr and V concentrations were used to estimate the strain factors and mass balance equations were used to quantify the net result of pedogenic weathering,i.e.elemental loss and gain.The results of clay content and pedogenic iron variability as well as index of compositional variability(ICV),chemical index of alteration(CIA) and,A-CN-K and MFW ternary plots showed that the soils developed on volcanic rocks(hornblende andesite> pyroxene andesite> dacite) were more weathered than those on the plutonic parent rocks(alkali granite,granodiorite,monzodiorite,syenite,pyroxene diorite).The results of mass balance calculations based on the strain factors revealed that the Ca and Na depleted during weathering progress mostly from plagioclase grains.In the semiarid regions Ca is precipitated as pedogenic calcite in the soil horizons.K and Mg depletion is less than Ca and Na especially in the profiles on the hornblende andesite with the highest clay and LOI content.The results of this study clearly suggest that the behavior of K and Mg during the weathering cannot only be explained by the disintegration of the primary minerals,since they are fixed on the secondary clay minerals.Iron did not change in the soils compared to the parent material and was precipitated as the pedogenic iron and conserved in the soil horizons.Overall,the results on the weathering indicators and major elements mass balance enrichment/depletion in the study area confirmed that the soil profiles developed on volcanic rocks are more weathered than those on the plutonic igneous rocks.
