阜平片麻岩之成因

阜平片麻岩的主体成分为灰片麻岩,其稀土型式相似于世界各地的太古代灰片麻岩。该灰片麻岩含丰富的变基性岩包体,二者构成双峰式系列,并经历了强烈形变,变质级别达高角闪岩相。阜平灰片麻岩由基性来源部分熔融而形成。

ORIGIN OF THE FUPING GNEISSES

The Fuping gneiss complex consists mainly of the grey gneisses which are interlayered with small amount of amphibolite and metavolcanic and meta sedimentary rocks. On the basis of the REE data, the Fuping grey gneisses can be divided into two types. The REE pa+-terns of the first type show less fractionation with a prominent negative Eu anomaly. The REE patterns of the second one show highly fractionation with no prominent Eu anomally. Both types could be derived from partial melting of mafic source rocks, but have different mineral phases in the residue. In the first case, the residue consists mainly of plagioclase; in the second case, the most mineral in the residue is amphibole. It is supposed that the latter is related to the total pressure under which the protolithic magma might be derived. At relatively low pressure the residue contains mainly plagioclase; at relatively high pressure the residue contains mainly amphibole. Thus, the protolith of the Fuping grey gneisses might be produced in the different crustal levels corresponding to different total pressures.