Morphology, Trace, and Rare Earth Elements of Detrital Zircon of Kayamkulam, Thottappally Placers, South West India—Implications for Provenance

Abstract

Detrital zircon crystals from beach and were subjected to morphology and Inductively coupled plasma mass spectrometry (ICPMS) analysis to assess the efficacy of the zircon composition as a provenance indicator. The inclusions of rutile and sillimanite in the lattice of the zircon support metamorphic growth. Zircon grains from relatively dry alkalic and igneous rocks tend to be dominated by {100} and {101} forms, whereas those from aluminous to calc-alkaline rocks exhibit various combinations of forms, with a predominance of {211}, and those from water-rich granites and pegmatites tend to have {110} and {101} as their dominant forms. Prismatic faces develop from zircon mainly due to the temperature of the crystallisation, but the pyramidal faces were linked to chemical factors. Light group Rare Earth Element (LREE) is enriched relative to Heavy group Rare Earth Element (HREE) in zircon. It shows significant negative anomalies in Eu, Co, Rb, and Cs and positive anomalies in V, Zn, Sr, Y, Nb, and Ba. The negative anomaly of Eu is maybe due to the redox condition operative at the time of zircon crystallisation from magma, where most of the Eu could be in Eu2+ state. The ratio of the Zr/Hf in detrital zircon shows a range of values between 6.56 and 6.25%. This supports the idea of the role ascribed to mafic rocks for the parentage of southwest coastal placer deposits.