Other
Scientific paper
Mar 1987
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1987gecoa..51..567b&link_type=abstract
Geochimica et Cosmochimica Acta, vol. 51, Issue 3, pp.567-587
Other
41
Scientific paper
Relations characterizing the chemical, physical, and mechanical changes resulting from metasomatic hydrochemical processes are developed using mass balance models which formally link chemical composition to bulk density, mineral density, volumetric properties, porosity, and amount of deformation (strain). Rigorous analysis of aqueous solute transport effects is then made possible in a variety of porous media flow environments including chemical weathering, pedogenesis (soil formation), diagenesis, ore deposition and enrichment, and metamorphism. Application of these linear constitutive relations to chemical weathering profiles shows that immobile and locally mobile chemical elements, with masses conserved on the scale of soil profiles, can be accurately identified from analysis of appropriate data arrays and then used as natural geochemical tracers to infer the nature and extent of hydrochemical weathering processes and volume changes during pedogenesis. Assumptions commonly made in the past about the supposed immobility of certain elements, e.g. , Ti and Zr, become unnecessary. Quantitative differentiation between the effects of residual and supergene fractionation is then easily made. These methods are applied to Ni-rich laterites developed by weathering of ultramafic rocks, showing that during ordinary residual enrichment, Ni is concentrated by as much as 4× protolith peridotite concentrations. This occurs simply by silicate mineral dissolution and removal of chemical elements other than Ni ( e.g. , Mg) with a corresponding reduction in saprolite density and increase in bulk porosity without significant deformation. In contrast, laterites with mineable concentrations of Ni which are similarly undeformed (such as the Nickel Mountain Mine in Riddle, Oregon) have experienced, in addition to residual enrichment, strong supergene enrichment by fractionation of ore elements between a leached zone from which Ni is extracted and a complementary enriched zone positioned farther along the direction of ground water flow. Soil-forming processes in podzol chronosequences developed on sandy beach terraces of the Mendocino Coast of California involved soil column collapse of 60 percent by dissolution of silicate minerals in the albic horizon of Al and Fe leaching, and 70 percent dilation (expansion) in the overlying organic-rich layer by root growth. The amount of erosion based upon paleosurface reconstructions using the excess mass of Fe, Al, Pb, Ga, and Cu in the zone of supergene enrichment (spodic horizon) below the ground water table indicates that subsurface erosion by dissolutional collapse is three times that of surficial erosion. Finally, using published chemical data for Ti, Zr, and Cr on major bauxite deposits in Australia where erosion rates are thought to be low, we infer that there may have been major amounts of dissolutional collapse to explain the upwards increase of detrital zircon and rutile in weathering profiles.
Brimhall George H.
Dietrich William E.
No associations
LandOfFree
Constitutive mass balance relations between chemical composition, volume, density, porosity, and strain in metasomatic hydrochemical systems: Results on weathering and pedogenesis does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Constitutive mass balance relations between chemical composition, volume, density, porosity, and strain in metasomatic hydrochemical systems: Results on weathering and pedogenesis, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Constitutive mass balance relations between chemical composition, volume, density, porosity, and strain in metasomatic hydrochemical systems: Results on weathering and pedogenesis will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1455569