Geochemical and Isotopic Investigation of the Miaoya Carbonatite Complex, Central China

The Miaoya carbonatite complex is located within the southwestern edge of the Wudang Terrane at the southern margin of the Qinling orogenic belt. The latter separates the North China block from the South China block, and is divided into the North and South Qinling belts along the Shangdan suture. The North Qinling belt is interpreted to represent a Mid-Paleozoic orogen consisting of widespread Paleozoic island-arc type magmatism and metamorphism. In contrast, the South Qinling belt represents a Late-Paleozoic to Early- Mesozoic orogen characterized by abundant Triassic granitic metamorphism and magmatism. A single K-Ar biotite age reported for the Miaoya carbonatite yields a date of 278 Ma. The Miaoya carbonatite intrusives consist predominantly of calcite and contain abundant rare earth element (REE)-bearing minerals, such as fluorapatite, monazite-(Ce), bastnäsite-(Ce) and synchysite-(Ce). Previous investigations report that the abundant REE mineralization associated with the Miaoya carbonatites is a primary magmatic feature and not associated with obvious hydrothermal REE mineralization, which differentiates it from most other REE deposits worldwide. In this study, the petrography and major element composition of a suite of Miaoya carbonatites are investigated via micro-XRF and electron microprobe analyses. Carbonate separates are investigated for their C and O isotope compositions, and in-situ trace element and Sr and Pb isotope analyses are obtained via laser ablation-ICP-MS. The combined elemental and isotopic results are used to determine the validity of the magmatic petrogenetic model proposed for the origin of the Miaoya carbonatites and its associated REE deposits.