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Effect of water regime and vegetation on initial granite weathering in a glacier forefield: Evidences from CL, SEM, and Nomarski DIC microscopy


Wongfun, Nuttakan; Götze, Jens; Furrer, Gerhard; Brandl, Helmut; Plötze, Michael (2013). Effect of water regime and vegetation on initial granite weathering in a glacier forefield: Evidences from CL, SEM, and Nomarski DIC microscopy. Geoderma, 211-212:116-127.

Abstract

Glacier forefields are characterised by high spatial variability in water availability, solar radiation, and vegetation, as well as weathering processes. The aim of this study is to improve the understanding of initial weathering of granite material with respect to the water regime (availability and residence time of the water) and the vegeta- tion cover. Samples of granite powder were buried in four selected sites at the Damma glacier forefield for one year. A combined application of cathodoluminescence (CL) microscopy and spectroscopy, scanning electron mi- croscopy (SEM), and Nomarski differential interference contrast (Nomarski DIC) microscopy was used to investigate the initial stage of weathering. The examination of the initial weathering stage revealed that the exposed mineral grains were strongly characterised by intra-variations. A clear change in particle shape and surface morphology could not be observed within the relatively short exposure period of one year. However, the grains from the lake sediment exhibited a clearly rounded shape, caused by mechanical abrasion during transport processes. The combination of several microscopic methods revealed (i) a strong influence of vegetation in the case of plagioclase-oligoclase alteration, (ii) a mutual effect of water and vegetation in the case of biotite delamination, and (iii) alterations of potassium feldspar independent of local environments. Investigations with cathodoluminescence microscopy showed the suppression of blue luminescence and developed brown luminescence and confirmed a new insight in potassium feldspar weathering.

Abstract

Glacier forefields are characterised by high spatial variability in water availability, solar radiation, and vegetation, as well as weathering processes. The aim of this study is to improve the understanding of initial weathering of granite material with respect to the water regime (availability and residence time of the water) and the vegeta- tion cover. Samples of granite powder were buried in four selected sites at the Damma glacier forefield for one year. A combined application of cathodoluminescence (CL) microscopy and spectroscopy, scanning electron mi- croscopy (SEM), and Nomarski differential interference contrast (Nomarski DIC) microscopy was used to investigate the initial stage of weathering. The examination of the initial weathering stage revealed that the exposed mineral grains were strongly characterised by intra-variations. A clear change in particle shape and surface morphology could not be observed within the relatively short exposure period of one year. However, the grains from the lake sediment exhibited a clearly rounded shape, caused by mechanical abrasion during transport processes. The combination of several microscopic methods revealed (i) a strong influence of vegetation in the case of plagioclase-oligoclase alteration, (ii) a mutual effect of water and vegetation in the case of biotite delamination, and (iii) alterations of potassium feldspar independent of local environments. Investigations with cathodoluminescence microscopy showed the suppression of blue luminescence and developed brown luminescence and confirmed a new insight in potassium feldspar weathering.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:07 Faculty of Science > Institute of Evolutionary Biology and Environmental Studies
Dewey Decimal Classification:570 Life sciences; biology
590 Animals (Zoology)
Language:English
Date:2013
Deposited On:22 Aug 2013 10:08
Last Modified:05 Apr 2016 16:54
Publisher:Elsevier
ISSN:0016-7061
Publisher DOI:https://doi.org/10.1016/j.geoderma.2013.07.009

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