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首页> 外文期刊>Tectonophysics: International Journal of Geotectonics and the Geology and Physics of the Interior of the Earth >Southward extrusion of eclogite-bearing mafic-ultramafic bodies in the Sanbagawa belt, central Shikoku, Japan
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Southward extrusion of eclogite-bearing mafic-ultramafic bodies in the Sanbagawa belt, central Shikoku, Japan

机译：日本四国中部三河川带中带榴辉岩的镁铁质-超镁铁质体向南挤压

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摘要

several mafic rock masses, which have experienced eclogite facies metamorphism, are distributed in flat-lying non-eclogitic schists in an intermediate structural level (thermal core) of the Sanbagawa belt. The largest, Iratsu mass, and an associated peridotite, the Higashi-Akaishi mass, extend E-W for about 8 km, and N-S for about 3 km, and are surrounded by pelitic, basic and quartz schists. The Iratsu mass consists of metabasites of gabbroic and basaltic origin, with intercalations of ultramafic rocks, felsic gneiss, quartz schist and metacarbonate. The Iratsu mass can be divided into two layers along a WNW-trending metacarbonate layer. The Higashi-Akaishi mass consists of peridotite with intercalations of garnet clinopyroxenite. It is situated beneath the western half of the Iratsu mass, and their mutual boundary dips gently or steeply to the N or NE. These masses underwent eclogite, and subsequent epidote-amphibolite facies metamorphism as has been reported elsewhere. The Iratsu-Higashi-Akaishi masses and the surrounding rocks underwent ductile deformation under epidote-amphibolite facies (or lower P-T) metamorphic conditions. Their foliation generally trends WNW and dips moderately to the NNE, and the mineral lineation mostly plunges to the N and NE. In non-eclogitic schists surrounding the Iratsu Higashi-Akaishi masses, the foliation generally trends WNW and dips gently or steeply to the N or S and the mineral lineation mostly plunges to the NW, N and NE. Kinematic analysis of deformation structures in outcrops and oriented samples has been performed to determine shear senses. Consistent top-to-the-north, normal fault displacements are observed in peridotite layers of the Higashi-Akaishi mass and eclogite-bearing epidote amphibolite layers of the Iratsu mass. Top-to-the-northeast or top-to-the-northwest displacements also occur in non-eclogitic pelitic-quartz schists on the northern side of the Iratsu mass. In the structural bottom of the Iratsu-Higashi-Akaishi masses and to the south, reverse fault (top-to-the-south) movements are recognized in serpentinized peridotite and non-eclogitic schists. These observations provide the following constraints on the kinematics of the rock masses: (1) northward normal displacement of Iratsu relative to Higashi-Akaishi, (2) northward normal displacement of non-eclogitic schists on the north of the Iratsu mass and (3) southward thrusting of the Iratsu-Higashi-Akaisbi masses upon non-eclogitic schists in the south. The exhumation process of the Iratsu-Higashi-Akaishi masses can be explained by their southward extrusion. (C) 2004 Elsevier B.V. All rights reserved.
机译：经历了榴辉岩相变质作用的几个镁铁质岩体分布在三叶川川带的中间构造层（热芯）中的平坦非榴辉岩片岩中。最大的Iratsu质量以及一个相关的橄榄岩，Higashi-Akaishi质量，将E-W延伸约8 km，将N-S延伸约3 km，并被白垩质，碱性和石英片岩包围。 Iratsu团块由辉长岩和玄武岩成因的阶变质组成，并夹有超镁铁质岩石，长英质片麻岩，石英片岩和碳酸盐岩。 Iratsu物质可沿着WNW趋势的碳酸氢盐层分为两层。东赤石集团由橄榄岩和石榴石斜辉石组成。它位于Iratsu质量块的西半部之下，并且它们的相互边界向N或NE缓和或陡峭地倾斜。这些块体发生了榴辉岩，随后的附子-闪石岩相变质作用已经在其他地方报道过。 Iratsu-Higashi-Akaishi块体和周围的岩石在显露-闪石岩相（或较低的P-T）变质条件下经历了韧性变形。它们的叶面通常呈西北偏北趋势，并向北近北倾斜适度，矿物线大多向北向北倾斜。在围绕Iratsu Higashi-Akaishi团块的非生态岩片岩中，叶面通常趋向于西北偏北，并向北或北向缓缓或陡峭地倾斜，而矿物线大多向北偏北，北偏北和东北倾斜。对露头和定向样品中的变形结构进行了运动学分析，以确定剪切感。从东-赤石块的橄榄岩层和有松块的带榴辉岩的附子角闪石层中观察到一致的从上到北的正常断层位移。在Iratsu地块北侧的非外倾性胶粉石英片岩中也发生了从顶向东北或从顶向西北的位移。在Iratsu-Higashi-Akaishi群众的结构底部和南部，蛇形化橄榄岩和非硬岩片岩中都识别出反向断层（自上而下）运动。这些观察结果对岩体的运动提供了以下约束条件：（1）井上相对于东赤石的北正法向位移;（2）井上北面的非内陆片岩的北正向位移;（3） Iratsu-Higashi-Akaisbi群众向南推挤南部的非顺滑片岩。 Iratsu-Higashi-Akaishi人群的尸体挖掘过程可以通过向南挤压来解释。 （C）2004 Elsevier B.V.保留所有权利。

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