Tectonic Evolution of the Eastern Moroccan Meseta: From Late Devonian Forearc Sedimentation to Early Carboniferous Collision of an Avalonian Promontory
Tectonic Evolution of the Eastern Moroccan Meseta: From Late Devonian Forearc Sedimentation to Early Carboniferous Collision of an Avalonian Promontory
复制标题
摩洛哥东部梅塞塔的构造演化：从晚泥盆世弧前沉积到早石炭世阿瓦隆期海角碰撞
作者：
Cristina Accotto;D. Martínez Poyatos;A. Azor;A. Jabaloy‐Sánchez;C. Talavera;N. Evans;A. Azdimousa
摩洛哥东部梅塞塔的变形古生代序列在相对较小且孤立的内层中露头，周围环绕着中生代和新生代岩石。两个最大的内围层（Mekkam和Debdou）的特征是在低至极低变质条件下发生的多相褶皱影响下的板岩和灰岩的单调连续。来自Debdou-Mekkam变质沉积物的碎屑锆石颗粒的新U-Pb年龄将最大沉积年龄限制为晚泥盆世，解释为接近真实沉积年龄。此外，泥盆纪碎屑锆石的εHf值以及一系列年龄在c. 0.9和c. 1.9 Ga，表明物源来自阿瓦隆边缘与俯冲有关的岩浆弧。Debdou‐Mekkam构造的特征是早石炭世第一次变形事件（D1），该事件让位于与多公里尺度相关的普遍劈理（S1），紧密等倾，翻转为平卧褶皱。后期事件（Dc）发生在石炭纪晚期，并产生了与不同方向的公制至千米级褶皱相关的非常发育的锯齿状劈理（Sc），这使D1交叉线理（L1）和轴向痕迹的模式复杂化。这种明显的弯曲模式的恢复产生了最初的SW‐NE‐取向的D1褶皱轴，具有区域SE‐聚散。这一重要的早石炭世缩短和东南向构造搬运可以用莱茵洋的闭合以及冈瓦纳北方被动边缘与阿瓦隆海岬碰撞的第一阶段来解释。
The deformed Paleozoic succession of the Eastern Moroccan Meseta crops out in relatively small and isolated inliers surrounded by Mesozoic and Cenozoic rocks. Two of the largest inliers (Mekkam and Debdou) are characterized by a monotonous succession of slates and greywackes affected by polyphasic folding that occurred at low‐ to very low grade metamorphic conditions. New U‐Pb ages on detrital zircon grains from the Debdou‐Mekkam metasediments constrain the maximal depositional age as Late Devonian, interpreted to be close to the true sedimentation age. Furthermore, the εHf values of the Devonian detrital zircons, together with the presence of a series of scattered zircon grains with ages between c. 0.9 and c. 1.9 Ga, suggest provenance from a subduction‐related magmatic arc located on the Avalonian margin. The Debdou‐Mekkam massif is characterized by an Early Carboniferous first deformational event (D1), which gave way to a pervasive cleavage (S1) associated with plurikilometric‐scale, tight to isoclinal, overturned to recumbent folds. Later events (Dc) occurred at Late Carboniferous time and generated variably developed crenulation cleavages (Sc) associated with variously oriented metric‐ to kilometric‐scale folds, which complicate the pattern of both D1 intersection lineations (L1) and axial traces. The restoration of this pronounced curved pattern yields originally SW‐NE‐oriented D1 fold axes with regional SE‐vergence. This important Early Carboniferous shortening and SE‐directed tectonic transport can be explained by closure of the Rheic Ocean and the first phases of the collision between the northern passive margin of Gondwana and an Avalonian promontory.
影响因子：
12.1
作者：
P. Vermeesch
通讯作者：
P. Vermeesch
影响因子：
5.8
作者：
Cawood, P. A.;Hawkesworth, C. J.;Dhuime, B.
通讯作者：
Dhuime, B.