Abstract: The granulites in various compositions and their retrograded products (plagio-clase amphibolites) are dominant members of the Early Archaean metamorphic rock series in the Eastern Hebei province,China.The meta-ironstone occurs in the upper part of the metamorphic rock series.There are some intercalations of ultramafic rock in the form of lens and thin layer in the base of the metamorphic rock series.The mineral assemblage is orthopyroxene + clinopyxene + plagioclase + quartz + magnetite ? garnet ? hornblende ? biotite.This paper presents wet chemical analyses of fifty two rock samples.The original rock types of the metamorphic rock series are distinguished by nine methods.The conclusions are as follows:the granulite and its retrograded product are considered to be derived essentially from a suite of volcanic rocks,in which the pyroclastic rocks are locally developed.The suite of volcanic rocks is essentially composed of intermediate and basic lavas with minor acid volcanic rocks which were metamorphosed into pyroxene and felsic granulites respectively.The original rock of meta-ultramafic rock may be ultramafic or mafic lava.The iron-bearing rock series in Mt.Louzi is considered to be derived from a suite of sedimentary rocks,with minor pyroclastic rocks.Petrochemistry of the volcanic rock series shows that most of the volcanic rocks belong to nonalkalic rock series and a small amounts of basic volcanic rock belong to the alkalic series.The basic member of the nonalkalic series is characterized by low K2O(1% wt.) and TiO2(1.2% wt.),and Na2O>>(or>)K2O.It belongs possibly to the island arc tholeiitic series.The alkalic basalt described appears to be ascribed to the straddle-I type.In addition,there exists a kind of high-Mg basalt (MgO,15-16%),which was metamorphosed into the meta-amphibole pyroxenite in the area studied.The chemiscally can be comparable with the komatiite.However,all the acid volcanic rocks studied belong to CA rock series.The nature of the volcanic rock association implies that this area was of high thermal flow at that time,and similar to recent heat point.It was caused by the strong mantle diapirism leading to the upwelling and extrusion of materials.Then,an oceanic island was rapidly built on the oceanic crust and developed into an initial island arc.