Geochemical features and geological significance of the leucosomes in the quartzofeldspathic gneisses of Fuping Complex, Hebei, China

The leucosomes in the quartzofeldspathic gneisses of Fuping Complex can be discerned to two types. The earlier type is rich in microcline, quartz, but poor in plagioclase and essentially aligned along the foliation. This leucosome is formed under low-water anatexis or pressure solution, locally dehydrated but has not been up to the degree of total dehydration as a whole. Cutting the folition, the late type is rich in plagioclase, quartz, but poor in K-feldspar, and is derived from water-present partial melting. The Pingyang trondhjemite may correspond with this stage. But the Nanying gneiss and leucogranite are inconsistent with other gneisses of the region in geochemistry. The REE patterns of the leucosomes are very complicated. According to the relative enrichment or depletion of elements, we can deduce that most leucosomes are controlled by the host bulk chemistry. From the earlier leucosome to the later one, the REE tend to be relatively depleted in LREE and enriched in HREE, and some trace elements may inherit the features of the host. Relative to the geochemical features, it seems that the mineral assemblages of the leucosomes are more important for the stage ascription. The metamorphism evolution of the Fuping Complex is not simple progressive dehydration and the water content variation in the system is rather complicated. Detailed research can assist in elucidating the geological process of the region.