Abstract This study provides new insights about mechanisms of synkinematic interplay between dyking emplacement and ductile narrow shear zones formation in the Sierra Chica de Cordoba. A detailed analysis of structural, microstructural, geometric-scaling and geochronologic data is performed in order to demonstrate the important role that minor and meso-scale felsic dykes played in the formation of paired shear zones symmetrically from dyke contacts. This magmatism and associated deformation conspicuously overprint medium-to high grade metamorphic and igneous rocks of Pampean age. Internally, the shear zones are formed by mylonites with mineral paragenesis in the amphibolite facies and foliation planes totally concordant to dyke contacts. Low rheological contrast between igneous intrusions and host rocks, together with fast rates of magma channeling and emplacement, was responsible for a brittle mechanical regime at moderate to high temperatures (500–700 °C). Melt-filled shear fractures rapidly propagated while the host rock was being mylonitized at ductile conditions. Shear structures controlling dyke construction and mylonite formation adjust to a strike-slip dominated dextral transtensional regime. The predicted axes of finite maximum shortening (Z) and maximum extension (X) have NNE and NNW directions, respectively. Ar/Ar muscovite cooling ages determined for pegmatite dykes, yielded minimum crystallization ages between 451 ± 1 and 435 ± 3 My. These geochronological data are further supported by field structural relationships and the regional knowledge, pointing to a Famatinian age for magmatism and related narrow shear zones. This paper constitutes a new contribution reporting the occurrence of magmatism and strike-slip-dominated dextral transtension deformation in the inner foreland of the Famatinian accretionary orogen, developed in the Middle Paleozoic along the southwestern Gondwana margin.

中文翻译：

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长英质岩脉和主岩糜棱岩化之间的同运动相互作用：岩浆作用如何帮助阿根廷科尔多瓦山脉韧性窄剪切带的形成

摘要 本研究提供了新的见解，即在 Sierra Chica de Cordoba 中堤防侵位与韧性窄剪切带形成之间的同运动相互作用机制。对结构、微观结构、几何尺度和地质年代数据进行了详细分析，以证明小和中尺度长英质岩脉在由岩脉接触对称地形成成对剪切带中发挥的重要作用。这种岩浆作用和相关变形显着叠加了潘潘时代的中至高级变质岩和火成岩。在内部，剪切带由糜棱岩形成，角闪岩相和叶理平面中的矿物共生与岩脉接触完全一致。火成岩侵入体和主岩之间的低流变对比，加上岩浆窜流和侵位的速度快，是造成中高温（500-700°C）下脆性机械状态的原因。当主岩在韧性条件下糜棱岩化时，熔体填充的剪切裂缝迅速扩展。控制岩脉构造和糜棱岩形成的剪切结构调整到走滑主导的右旋张拉机制。有限最大缩短 (Z) 和最大延伸 (X) 的预测轴分别具有 NNE 和 NNW 方向。为伟晶岩脉确定的 Ar/Ar 白云母冷却年龄，产生的最小结晶年龄介于 451 ± 1 和 435 ± 3 My 之间。这些地质年代学数据得到了现场结构关系和区域知识的进一步支持，表明岩浆作用和相关的窄剪切带处于法马蒂阶时代。