Mineralogy, elemental composition and micromorphology of calcium carbonate nodules of some soils of central Punjab

The calcium carbonate nodules from alluvial plains soils of central Punjab were studied for their mineralogical, geochemical and micromorphological characteristics. The nodules reveal dominance of calcite with subsidiary amounts of quartz, feldspars, mica and chlorite/vermiculite whereas coarse fractions of soils have dominance of quartz. The alkali earth carbonates and insoluble residues are the chief constituents making up more than one-half and one-third of the total composition of the nodules. The carbonate nodules are generally non-dolomitic though appreciable substitution of calcium by magnesium has been noticed in some. The thin section of nodules shows skeletal grains supported by micritic calcite mixed with plasma material. The nodules contain cavities which are oftern lined with sparry calcite cement. In the light of the studies carried out on calcium carbonates nodules, their nature and genesis have been discussed.