Weathering of granites along an east-west climatic transect of northern India

• MD MAROOF AZAM

  ジャワハラルラネール大学

Abstract

Lithology and climate exert a major influence on weathering processes. The complete understanding of weathering processes necessitates a deeper study of inter-relationships of lithology-climate-weathering. In the present study, an attempt has been made to understand the role of climate and source-rock mineralogy in the formation of clay minerals during weathering of granites along an east-west climatic transect of northern India. The Aravalli craton (west), Bundelkhand craton (centre) and Singhbhum craton (east) provided an ideal condition to carry out this study as they are characterised by arid, semi-arid and sub-humid climate, respectively. Analysis of primary minerals present in the least altered granite rocks was carried out using thin section petrography, X-ray diffraction (XRD) technique and normative calculation. Clay mineralogy of weathering profiles along the climatic transect was studied using XRD. In the Aravalli craton, 2:1 clay (smectite, characteristic of the poorly drained environment) was dominant. Illite, interstratified smectite-kaolinite and kaolinite were found only in trace amounts. In the Bundelkhand craton, smectite, illite and kaolinite were dominant with some amount of interstratified smectite-kaolinite minerals and mixed layers (10-14 Å). On the other hand, in the weathering profiles of the Singhbhum craton 2:1 clay (illite) and 1:1 clay (kaolinite) were dominant clay minerals with significant peaks of mixed layer clays as well as interstratified smectite-kaolinite minerals. Interstratified smectite-kaolinite minerals characterised by tailing in the low angle region of kaolinite (7.2 Å) peak are an important ephemeral stage during the transformation of smectite to kaolinite in humid climates. Presence of interstratified smectite-kaolinite minerals is also suggestive of advancement of in situ weathering in the weathering profile. The data generated on clay mineralogy was analysed in the light of primary minerals present in granite of each area, and it was found that the rainfall plays a dominant role in the formation of clay minerals as compared to source-rock mineralogy.

Journal

• Abstracts of Annual Meeting of the Geochemical Society of Japan

  Abstracts of Annual Meeting of the Geochemical Society of Japan 65 (0), 41-, 2018

  GEOCHEMICAL SOCIETY OF JAPAN

Keywords

• Weathering
• Granite
• Source Rock
• Climate
• Clay Mineralogy

Details

• CRID: 1390564238048621824
• NII Article ID: 130007520776
• DOI: 10.14862/geochemproc.65.0_41
• Text Lang: ja
• Data Source:
  • JaLC
  • CiNii Articles
• Abstract License Flag: Disallowed