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首页> 外文期刊>Geodinamica Acta >Oligo-Miocene exhumation of the Beni-Bousera peridotite througha lithosphere-scale extensional shear zone
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Oligo-Miocene exhumation of the Beni-Bousera peridotite througha lithosphere-scale extensional shear zone

机译：贝尼-玻色亚橄榄岩橄榄岩中新世的岩石圈规模扩展剪切带发掘

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摘要

New structural data and P—T estimates of syn-deformational assemblages within the Beni Bousera peridotites and their crustal envelope are used to explain their Alpine exhumation. The Beni Bousera peridotites occur as thin sheets within high grade crustal units of the lower Sebtides (inner Rif, Morocco) and are composed of weakly deformed spinel lherzolite in the core of the massif and garnet-spinel mylonite at the rim. The main foliation trajectories in both the peridotites and overlying crustal units show systematic rotation towards their mutual contact, indicating a kilometer-scale top to the NW shearing with a dextral component along this crust/mantle contact. Widespread top to the NW shear criteria within the crustal units overlying the peridotite support this feature. Available ages constrain the development of the main foliation in both the peridotites and crustal rocks between 25 and 20 Ma. New P—T data from the peridotites show that deformation occurs during decompression from 22 kbar, 1050°C to 9-15 kbar, 800°C. As a consequence, exhumation of the Beni Bousera peridotites takes place during the Oligo-Miocene lithosphere thinning in the footwall of a lithospheric extensional shear zone. The exceptional preservation of garnet within the mylonitic peridotites results from rapid cooling of the border of the massif due to the juxtaposition with colder crustal rocks along this shear zone. Uplifting of the hot mantle rocks simultaneously induces high temperature metamorphism in the overlying crustal units. These new findings allow us to reconstruct the deformation history of the Beni Bousera region and the Alboran domain in the framework of the western Mediterranean geodynamics during the last 40 Myrs.
机译：贝尼布塞拉橄榄岩橄榄岩及其地壳中的新结构数据和对变形组合的PT估计被用来解释他们的高寒化石。 Beni Bousera橄榄岩以薄板的形式出现在下Sebtides（内里夫，摩洛哥）的高级地壳单元中，由地心中的弱变形尖晶石锂铁矿和边缘处的石榴石-尖晶石型山my石组成。橄榄岩和上覆地壳单元的主要叶面轨迹都显示出朝着它们相互接触的方向系统旋转，这表明沿着地壳/地幔接触，一公里规模的顶部向西北剪切，具有右旋成分。覆盖在橄榄岩上的地壳单元内的西北剪切标准的广泛顶部支持该特征。可用年龄限制了25至20 Ma之间的橄榄岩和地壳岩石的主要叶脉发育。来自橄榄岩的新的PT数据表明，在从1050°C的22 kbar压缩到800°C的9-15 kbar的减压过程中会发生变形。结果，在岩石圈伸展剪切带下盘的中新世岩石圈变薄过程中，发生了贝尼·布塞拉橄榄岩的发掘。石榴石在橄榄岩橄榄岩中的特殊保存是由于沿该剪切带与较冷的地壳岩石并置而使地块边界迅速冷却所致。热地幔岩石的隆升同时引起上覆地壳单元的高温变质作用。这些新发现使我们能够在最近40 Myrs的西地中海地球动力学框架内重建Beni Bousera地区和Alboran域的变形历史。

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