Continental intraplate volcanic systems, with their locations far from plate tectonic boundaries, are not well understood: the crustal and lithospheric mantle structure of these systems remain enigmatic and there is no consensus on the mechanisms that cause melt generation and ascent. The Cenozoic saw the development of numerous volcanic provinces on the African plate, including within the Central Hoggar, located in Northwest Africa, part of the Tuareg shield. The magmatic activity began at approximately 34 Ma and continued throughout the Quaternary. In order to understand the origins and potential mechanisms that generated the intraplate volcanic activity in the Central Hoggar we aim to image the subsurface architecture, in terms of electrical resistivity, from the surface to the lithospheric mantle. To do so we use magnetotelluric measurements from 40 locations to generate a 3-D electrical resistivity model, over an area of about 100 km by 160 km. Low-resistivity features (i.e., conductors) are observed in the crust that are narrow, linear structures congruent with the boundaries of terranes and prominent fault zones (e.g., Azrou N’Fad). They likely reflect the Pan-African mega-shear zones, which were reactivated throughout the tectonic evolution of the region. The model reveals that these faults are lithospheric-scale. The low-resistivity features likely represent the signatures of past fluid pathways and mineralization. A deeper low-resistivity feature is observed in the upper lithospheric mantle directly beneath the Manzaz and Atakor volcanic districts. It may represent local, small-scale metasomatism of the sub-continental lithospheric mantle, and low-percent partial melting, that sits above a regional, large-scale asthenospheric upwelling associated with the Hoggar swell. It is likely the origin point of the fluids responsible for the overlying anomalies. The results highlight the control of the lithospheric-scale, mega-shear zones on the spatial distribution of the recent Cenozoic volcanic activity, which was influenced by the location of pre-existing structural weaknesses.

中文翻译：

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大陆板内火山系统的结构和剪切带的控制：从电阻率图像洞察非洲西北部中部霍加尔新生代火山省


大陆板内火山系统的位置远离板块构造边界，人们对这些系统的了解还不够深入：这些系统的地壳和岩石圈地幔结构仍然是个谜，并且对于导致熔体产生和上升的机制也没有达成共识。新生代见证了非洲板块上许多火山省的发展，包括位于非洲西北部的中央霍加尔火山省，它是图阿雷格地盾的一部分。岩浆活动开始于大约34 Ma，并持续整个第四纪。为了了解中央霍加尔板内火山活动的起源和潜在机制，我们的目标是根据电阻率对从地表到岩石圈地幔的地下结构进行成像。为此，我们使用 40 个位置的大地电磁测量来生成面积约 100 公里 x 160 公里的 3D 电阻率模型。在地壳中观察到低电阻率特征（即导体），这些特征是狭窄的线性结构，与地体和突出断层带（例如，Azrou N'Fad）的边界一致。它们可能反映了泛非大剪切带，这些剪切带在该地区的构造演化过程中被重新激活。该模型显示这些断层是岩石圈规模的。低电阻率特征可能代表了过去流体通道和矿化的特征。在曼扎兹和阿塔科尔火山区正下方的上岩石圈地幔中观察到更深的低电阻率特征。 它可能代表了次大陆岩石圈地幔的局部小规模交代作用，以及位于与霍格隆起相关的区域性大规模软流圈上升流上方的低百分比部分熔融作用。它很可能是造成上覆异常的流体的起源点。结果强调了岩石圈规模、巨型剪切带对近代新生代火山活动空间分布的控制，这受到先前存在的结构弱点位置的影响。