Single-crystal structure analysis of REE-bearing zircon: evidence of the HREE-Th rich zircon formed at low temperature in an igneous process

Abstract

Zircons from granitic rocks, Japan, were divided into two types: an HREE-U-Th-poor type from granites and an HREE-U-Th-rich type from granitic pegmatites. Zircons of an HREE-U-Th-poor type from granites are formed at high temperature (>700 °C), whereas those of an HREE-U-Th-rich type from granitic pegmatites at low temperature (<500 °C) (Hoshino et al., 2007). Hoskin & Schaltegger (2003) suggested that zircon contain less than 1 wt% ΣREE + Y and analyses containing significantly higher abundances almost certainly represent altered zircon or accidental analysis of inclusions. This aims of this study are (1) to determine accurate chemical compositions and crystal structure of zircon from Takenouchi granitic pegmatite, Japan and (2) to confirm occurrence of zircon formed at low temperature in an igneous process.