| 冀东迁西-迁安地区早太古代变质岩系原岩恢复及其地质意义 |
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| 引用本文： | 从柏林,李继亮,张儒瑗.冀东迁西-迁安地区早太古代变质岩系原岩恢复及其地质意义[J].地质科学,1982,0(2):125-133. |
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| 作者姓名： | 从柏林 李继亮 张儒瑗 |
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| 作者单位： | 中国科学院地质研究所 |
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| 摘 要： | 冀东早太古代变质岩系的主体是一套呈层分布的,各种成分麻粒岩及其某些退变质产物——斜长角闪岩类。在其上部发育变质含铁建造,而在其下部常夹有变质的镁铁质和超镁铁质岩(如变闪辉岩、变辉石岩和蛇纹石化橄榄岩等)薄层或透镜体。 麻粒岩的矿物组合是斜方辉石+单斜辉石+斜长石(常常为反条纹长石)+石英+磁铁矿±角闪石±黑云母。在变质含铁建造中局部出现包括铝硅酸盐的矿物组合(蓝晶石-石榴石-黑云母-斜长石-石英)。变质铁硅质岩可以分为两类:辉石磁铁石英岩和英榴易熔岩(张儒瑗,从柏林,1981)。
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ON THE PROTOTITH RECONSTRUCTION AND GEOLOGICAL IMPLICATIONS OF EARLY ARCHAEAN METAMORPHIC ROCKS IN EASTERN HEBEI |
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| Cong Bolin,Li Jiliang,Zhang Euyuan.ON THE PROTOTITH RECONSTRUCTION AND GEOLOGICAL IMPLICATIONS OF EARLY ARCHAEAN METAMORPHIC ROCKS IN EASTERN HEBEI[J].Chinese Journal of Geology,1982,0(2):125-133. |
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| Authors: | Cong Bolin Li Jiliang Zhang Euyuan |
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| Institution: | Institute of Geology, Academia Sinica, Beijing |
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| 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. |
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