Zircon/rock partition coefficients of REEs, Y, Th, U, Nb, and Ta in granitic rocks: Uses for provenance and mineral exploration purposes

Abstract

The trace element composition of magmatic zircon is highly variable even within the same grain, and its study is complicated by the abundance of microinclusions, metamict portions, and strong compositional zoning, among other factors. To contribute to the understanding of the geochemistry of trace elements in zircon, we determined the rare earth, Y, Nb, Ta, Th, and U contents in zircon grains by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) with the use of cathodoluminescence and backscattered MEV images. Zircon/rock partition coefficients were determined in nine different types of granitoids and compared with experimental and natural data. The obtained data are comparable with those reported by other authors. By using the partition coefficient, we estimated the composition of the host granitoids based on the zircon grain composition, which was interpreted as evidence that the patterns of the trace elements in zircon grains are controlled by the liquid composition at the moment of crystallization. A new set of partition coefficients for REEs, Y, Nb, Ta, Th, and U is suggested for provenance and exploratory studies: La 0.8, Ce 1.7, Pr 2.1, Nd 3.4, Sm 9.8, Eu 7.9, Gd 24, Tb 37, Dy 69, Ho 117, Er 167, Tm 281, Yb 379, Lu 437, Nb 1.6, Ta 2.9, Th 27, U 177, and Y 109. Trace element diagrams (Eu*/Eu vs. Yb, Nb vs. Th, and (Y/200+Lu/10+Nb) vs. Nb/Ce) are proposed for discriminating zircon from different types of granitoids, particularly for A-type, I-type and shoshonitic rocks. The trace element patterns of zircon are useful as a tool for mineral exploration studies because they often reproduce the patterns of mineralized granites.