Composition of the peninsular India rivers average clay (PIRAC): A reference sediment composition for the upper crust from peninsular India

Abstract

We present a new dataset on the average composition of the clay fraction of sediments in 13 rivers draining the entire peninsular India, referred to here as Peninsular India Rivers Average Clay (PIRAC). PIRAC showed relatively low Si and high Fe, Mn and Mg compared to the other reference sediments. The total trace elements (∑TE) content of PIRAC was lower than that of Post-Archean average Australian Shale (PAAS), but close to that of Average Suspended Sediment of World Rivers (ASSWR). The total rare earth elements (∑REE) content of PIRAC was slightly lower than that of PAAS but close to that of World River Average Clay (WRAC). The ∑TE and ∑REE were much higher for PIRAC than in other reference sediments. Anomalously high Cu, Zn and Pb in PIRAC suggest that these trace elements do not reliably indicate the crustal composition. PAAS-normalised REE of PIRAC showed LREE-depleted, MREE- and HREE-enriched REE patterns with positive Ce and Eu anomalies, suggesting that PIRAC is more mafic than that of PAAS and the clays weathered from volcanic rocks and felsic component of the metamorphic rocks dominated the crustal composition of peninsular India. The REE pattern of PIRAC resembles to that of European Shale (ES) and Mud of Queensland (MUQ) but different from PAAS, WRAC, upper continental crust (UCC) and East China Post-Archean Shale (ECPAS), which exhibit LREE-enriched and HREE-depleted REE patterns. It implies that the REE composition of the upper crust is not uniform and it should be thoroughly investigated to determine the composition of PIRAC with more analyses on sediments for better understanding of the evolution of the crust.