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首页> 外文期刊>Journal of Asian earth sciences >The petrology of two distinct granulite types in the Hengshan Mts, China, and tectonic implications
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The petrology of two distinct granulite types in the Hengshan Mts, China, and tectonic implications

机译：衡山的两种独特的花岗石类型的岩石学及其构造意义

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摘要

The Archean to Proterozoic Hengshan Complex (North China Craton), comprises tonalitic and granodioritic gneisses with subordinate mafic lenses, pegmatites and granites. Amphibolite facies assemblages predominate, although granulite-facies relics are widespread, and greenschist-facies retrogression occurs in km-wide shear zones. Mafic lenses, locally abundant, occur as strongly deformed amphibolite (hornblende + plagioclase) boudins or sheets. In contrast to previously published models we find two series of mafic rocks with distinctly different granulite-facies evolutions. In the north of the complex, relict high-pressure mafic granulites are garnet + clinopyroxene-bearing rocks with a secondary development of orthopyroxene around both garnet (kelyphites) and clinopyroxene (coronas). South of the newly defined central, E-W-trending, Zhujiafang shear zone, numerous mafic boudins and less-deformed dykes exhibit a macroscopically visible magmatic texture with coronitic growth of metamorphic garnet (full of quartz inclusions) between the magmatic plagioclase and pyroxene domains. Additional orthopyroxene (after magmatic augite) and sodic rims to magmatic plagioclase clearly indicate medium-pressure granulite-facies metamorphism. These findings suggest tectonic juxtaposition in this area of three different structural levels of the same Proterozoic-imprinted crust: high-pressure granulite grade in the northern Hengshan, medium-pressure granulite grade in the southern Hengshan and amphibolite- to greenschist-facies grade in the Wutaishan to the SE.
机译：太古代至元古代的横山综合体（华北克拉通）由成色质和粒状二元片麻岩组成，下属镁铁质晶状体，伟晶岩和花岗岩。尽管花岗石相遗迹很普遍，但角闪石相组合仍占主导地位，而绿片岩相的倒退发生在千米宽的剪切带中。镁铁晶状体，局部丰富，以强烈变形的角闪石（角闪石+斜长石）布丁或片状出现。与以前发表的模型相反，我们发现了两个系列的镁铁质岩石，其花岗石相演化明显不同。在该综合体的北部，残留的高压镁铁质花岗石是石榴石+含斜ino石的岩石，在榴石（锂盐岩）和斜cl石（日冕）周围有邻二甲苯的二次开发。在新定义的中部，西南走向的朱家坊剪切带以南，大量的铁镁质布丁和变形岩脉呈现出宏观可见的岩浆质地，并且在岩浆斜长石和辉石岩域之间变质的石榴石（充满了石英包裹体）呈皮质生长。在岩浆斜长石上还加入了邻苯二甲酚（岩浆辉石之后）和苏打边缘清楚地表明了中压粒岩相的变质作用。这些发现表明，该区域在构造上并列在同一元古代压印地壳的三个不同结构水平上：横山北部为高压花岗石等级，衡山南部为中压花岗石等级，恒山南部为闪石-绿片岩相。五台山到东南。

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