REE GEOCHEMISTRY OF PRECAMBRIAN GRANITOIDS IN WUTAISHAN REGION
Wu Suzhen(Tianjin Institute of Geology and Mineral Resources, Chinese Academy of Geosacnces, Tianjin 300170)
Conspicuous Archaean REE geochemical characteristics are noticed for the Precambrian granitoids in the Wutaishan region. The REE abundances of the granitoids show a progressive increase from the early to the late Wutai stage. For example, the REE abundances of potassic granitoids are higher than those of soda-granites and of high-Al granites are much lower than those of low-Al equivalents. Three types of REE distribution patterns have been distinguished: (1) rightward declined smooth curves, showing no obvious Eu anomaly (Eu/Eu* = 0.74-0.82) and high fractionation (granodiorite-quartz monzonite); (2) moderately rightward declined curves, displaying remarkable positive and negative Eu anomalies (Eu/Eu* = 1.24-1.62 -0.83) and a minimum total REE content (high-Al and low-Al tonalitetrondhjemite); and (3) rightward declined V-shape curves with a maximum content of REE (granites). These granitoids are considered to have resulted from partial melting and differentiation, and their parent materials may be originated from upper crust rocks and basalts.