Exhumation of basement rocks on the seafloor is a worldwide feature along passive continental margins and (ultra-) slow-spreading environments, documented by dredging, drilling or direct observations by diving expeditions. Complementary observations from exhumed ophiolites in the Alps allow for a better understanding of the underlying processes. The Aiguilles Rouges ophiolitic units (Val d’Hérens, Switzerland) are composed of kilometre-scale remnants of laterally segmented oceanic lithosphere only weakly affected by Alpine metamorphism (greenschist facies, Raman thermometry on graphite: 370–380 °C) and deformation. Geometries and basement-cover sequences comparable to the ones recognized in actual (ultra-) slow-spreading environments were observed, involving exhumed serpentinized and carbonatized peridotites, gabbros, pillow basalts and tectono-sedimentary cover rocks. One remarkable feature is the presence of a kilometric gabbroic complex displaying preserved magmatic minerals, textures and crosscutting relationships between the host gabbro and intruding diabase, hornblende-bearing dikelets or plagiogranite. The bulk major and trace element chemistry of mafic rocks is typical of N-MORB magmatism (CeN/YbN: 0.42–1.15). This is supported by in-situ isotopic signatures of magmatic zircons (εHf = + 13 ± 0.6) and apatites (εNd = + 8.5 ± 0.8), determined for gabbros and plagiogranites. In-situ U–Pb dating was performed on zircons by laser ablation-ICP-MS, providing ages of 154.9 ± 2.6 Ma and 155.5 ± 2.8 Ma, which are among the youngest for oceanic gabbros in the Alps. Our study suggests that the former Aiguilles Rouges domain was characterized by tectonism and magmatism resembling present-day (ultra-) slow-spreading seafloor. It also suggests that the Tethyan lithosphere is laterally segmented, with punctuated magmatism such as the Aiguilles Rouges gabbros and carbonated ultramafic seafloor covered by basalts and Jurassic tectono-sedimentary deposits.

中文翻译：

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化石海洋核心复合体在阿尔卑斯山。Tethyan Aiguilles Rouges Ophiolite（瑞士西阿尔卑斯山的Val d'Hérens）的新油田，地球化学和同位素约束

在被动大陆边缘和（超）缓慢扩展的环境中，海底基底岩石的挖掘是一项全球性的功能，通过疏,、钻探或潜水探险的直接观察来证明。来自阿尔卑斯山发掘的蛇绿岩的补充观测结果可以更好地理解其下伏过程。艾吉耶·鲁日（Aiguilles Rouges）的岩相单元（瑞士Val d'Hérens）是由横向分段的海洋岩石圈的几千米规模的残余物组成的，仅受高山变质作用（绿片岩相，石墨拉曼测温：370–380°C）和变形的影响。观察到的几何形状和基底覆盖序列与实际（超）缓慢扩展环境中可识别的序列相当，包括发掘出的蛇纹石化和碳化碳化橄榄岩，辉长岩，枕形玄武岩和构造沉积沉积岩。一个显着的特征是存在公里长辉长岩复合物，该岩辉石复合物显示了保留的岩浆矿物，质地以及宿主辉长岩与侵入辉绿岩，含角闪石二尖晶石或斜长花岗岩之间的横切关系。镁铁质岩石的本体化学和微量元素化学特征是N-MORB岩浆作用的典型特征（CeN / YbN：0.42-1.15）。岩浆锆石（εHf= + 13±0.6）和磷灰石（εNd= + 8.5±0.8）的原位同位素特征支持了这一点，确定了辉长岩和斜长花岗岩。通过激光烧蚀-ICP-MS在锆石上进行了原位U-Pb测年，年龄为154.9±2.6 Ma和155.5±2.8 Ma，是阿尔卑斯山中长生辉长石中年龄最小的年龄。我们的研究表明，前Aiguilles Rouges域的特征是构造运动和岩浆作用，类似于当今（超）缓慢扩展的海底。这也暗示着特提斯岩石圈是横向分段的，具有点状岩浆作用，例如被玄武岩和侏罗纪构造沉积沉积物覆盖的Aiguilles Rouges gabbros和碳酸盐化的超镁铁质海底。