冀东太古代高级变质地体中两类麻粒岩相深成片麻岩

河北东部太古代麻粒岩相深成片麻岩有两种类型:一种亏损放射性生热元素和大离子亲石元素;另一种富集这些元素。该文讨论了这种化学差异及造成差异的原因。

CONTRASTING ARCHAEAN GRANULITE FACIES ROCKS FROM EASTERN HEBEI, NORTH CHINA

In the eastern Hebei, North China, the Taipingzbai area is separated from Shuichang area by shear zone. Higher P-T conditions are recorded for Taipingzhai granulites, therefore two areas, representing different crustal levels, were in juxtaposition. The granulite facies orthogneisses from Taipingzhai and the charnockites from Shuichang have strikingly different chemistry. The Taipingzhai granulites are strongly depleted in heat-producing elements and other large ion lithophile elements, whereas, Shuichang charnockites are enriched in these elements. This is postulated to be due to the action of metamorphic fluids in the lower crust. Different models for source of fluids from both areas have been proposed. In Shuichang area, there is an intimite relationship between the production of granites and the charnockates. Differences in mineral and chemical composition between granites and charnockites are considered. It is suggested that such differences could result from partial melting processes occurred in metasedimentary gneisses.