Abstract. Based on recent results of AlpArray, we propose a new model of Alpine collision that involves subduction and detachment of thick (180–200 km) European tectosphere. Our approach combines teleseismic P-wave tomography and existing Local Earthquake Tomography (LET) allowing us to image the Alpine slabs and their connections with the overlying orogenic crust at an unprecedented resolution. The images call into question the conventional notion that slabs comprise only seismically fast lithosphere and suggest that the mantle of the downgoing European Plate is heterogeneous, containing both positive and negative Vp anomalies of up to 5–6%. We interpret these as compositional rather than thermal anomalies, inherited from the Variscan and pre-Variscan orogenic cycles. They make up a kinematic entity referred to as tectosphere, which presently dips beneath the Alpine orogenic front. In contrast to the European Plate, the tectosphere of the Adriatic Plate is thinner (100–120 km) and has a lower boundary approximately at the interface between positive and negative Vp anomalies. Horizontal and vertical tomographic slices reveal that beneath the Central and Western Alps, the downgoing European tectospheric slab dips steeply to the S and SE and is only locally still attached to the Alpine crust. However, in the Eastern Alps and Carpathians, the European slab is completely detached from the orogenic crust and dips steeply to the N-NE. This along-strike change in attachment coincides with an abrupt decrease in Moho depth below the Tauern Window, the Moho being underlain by a pronounced negative Vp anomaly that reaches eastward into the Pannonian Basin area. This negative Vp anomaly is interpreted to represent hot upwelling asthenosphere that was instrumental in accommodating Neogene orogen-parallel lateral extrusion of the ALCAPA tectonic unit (upper plate crustal edifice of Alps and Carpathians) to the east. A European origin of the northward-dipping, detached slab segment beneath the Eastern Alps is likely since its imaged down-dip length (300–500 km) matches estimated Tertiary shortening in the Eastern Alps accommodated by south-dipping subduction of European tectosphere. A slab anomaly beneath the Dinarides is of Adriatic origin and dips to the northeast. There is no evidence that this slab dips beneath the Alps. The slab anomaly beneath the northern Apennines, also of Adriatic origin, hangs subvertically and is detached from the Apenninic orogenic crust and foreland. Except for its northernmost segment where it locally overlies the southern end of the European slab of the Alps, this slab is clearly separated from the latter by a broad zone of low Vp velocities located south of the Alpine slab beneath the Po Basin. Considered as a whole, the slabs of the Alpine chain are interpreted as attenuated, largely detached sheets of continental margin and Alpine Tethyan lithosphere that locally reach down to a slab graveyard in the Mantle Transition Zone (MTZ).

中文翻译：

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大阿尔卑斯地区下方的欧洲构造层和板块–通过远震V _p研究解释阿尔卑斯-亚平宁山脉-潘诺尼山脉地区的地幔结构

摘要。根据AlpArray的最新结果，我们提出了一种高山碰撞的新模型，该模型涉及俯冲和脱离厚（180-200 km）的欧洲对流层。我们的方法将远震P波层析成像技术与现有的局部地震层析成像技术（LET）相结合，使我们能够以前所未有的分辨率对高山平板及其与上覆造山壳的联系进行成像。这些图像使传统观念认为平板仅包括地震快的岩石圈，并暗示正在下降的欧洲板块的地幔是非均质的，正负Vp异常都高达5％至6％。我们将这些解释为从Variscan和Variscan之前的造山循环中继承的成分异常而不是热异常。它们组成运动学实体，称为平流层，目前浸没在高山造山带锋面之下。与欧洲板块相比，亚得里亚海板块的大气圈更薄（100-120 km），并且在正负Vp异常之间的界面处具有较低的边界。水平和垂直断层扫描切片显示，在中阿尔卑斯山和西阿尔卑斯山下面，正在下降的欧洲构造层平板陡峭地向南和北倾斜，并且仅在局部仍附着在高山地壳上。但是，在东部阿尔卑斯山和喀尔巴阡山脉，欧洲板块完全与造山壳分离，并陡峭地倾入N-NE。这种沿袭的附着变化与Tauern窗下方的Moho深度突然减小相吻合，该Moho处于明显的负Vp异常之下，该异常向东延伸到Pannonian盆地地区。该负Vp异常被解释为代表上升流的软流圈，这有助于将新近纪造山带平行向东挤压ALCAPA构造单元（阿尔卑斯山和喀尔巴阡山脉的上地壳）。欧洲的起源可能是东阿尔卑斯山下方的北倾，分离的板块段，因为其成像的下倾长度（300-500 km）与估计的东阿尔卑斯山第三纪缩短相吻合，这是由于欧洲对流层北倾所引起的。Dinarides下面的板状异常源于亚得里亚海，并向东北倾斜。没有证据表明该板块浸没在阿尔卑斯山下面。也是亚得里亚海起源的亚平宁山脉北部下方的板状异常体垂下悬挂，并与亚平宁造山地壳和前陆分离。除了其最北端的部分局部覆盖在欧洲阿尔卑斯山板的南端，该板块明显地与后者隔开，位于波盆地下方的阿尔卑斯山板块以南的广阔的低Vp速度区。从整体上看，高山链条的板块被解释为大陆边缘和特提斯岩性岩石圈的衰减的，高度分离的片层，它们局部向下延伸至地幔过渡带（MTZ）的板块墓地。