REE geochemistry of recent clastic sediments from the Kaveri floodplains, southern India: Implication to source area weathering and sedimentary processes

The Kaveri River drains through Archean gneissic and chamockitic terranes i n south India. The rare earth element (REE) chemistry of the floodplain sed iments, along with their major and trace element composition in different s ize fractions, are discussed. We observe a strong coherence between REE and TiO2 contents in the sediments, which is suggestive of strong control by t itanite, or its weathered products, on the REE chemistry. REE concentration s also show a general increase with decreasing size of bulk sediments, diff erent size fractions and of light and heavy mineral fractions. This suggest s the presence of REE in the Fe-oxy-hydroxide surface coatings on clastic g rains, formed by the weathering of hornblende and titanite in the granodior itic to dioritic protoliths. We also interpret the data as showing that REE patterns of elastic sediments, notably Eu anomaly, are affected by the deg ree of source rock weathering, as well as by the fluvial processes of sorti ng and mineral differentiation. Therefore, for provenance study, sediments having all granulometric grades, such as the floodplain sediments, are pref erable because they most closely represent the source, particularly when th e source region suffered little chemical weathering. In the present case, t he sediments were derived from the high standing hills of Archean charnocki tes because of their recent uplift and physical denudation. Copyright (C) 2 001 Elsevier Science Ltd.