Abstract. Volgo-Uralia is a Neoarchean easternmost part of the East European craton. Recent seismic studies of the Volgo-Uralian region provided new insights into the crustal structure of this area. In this study, we combine satellite gravity and seismic data in a common workflow to perform a complex study of Volgo-Uralian crustal structure which is useful for further basin analysis of the area. In this light, a new crustal model of the Volgo-Uralian subcraton is presented from a step-wise approach: (1) inverse gravity modeling followed by (2) 3D forward gravity modeling. First, inversion of satellite gravity gradient data was applied to determine the Moho depth for the area. Density contrasts between crust and mantle were varied laterally according to the tectonic units present in the region, and the model is constrained by the available active seismic data. The Moho discontinuity obtained from the gravity inversion was consequently modified and complemented in order to define a complete 3D crustal model by adding information on the sedimentary cover, upper crust, lower crust, and lithospheric mantle layers in the process of forward gravity modeling where both seismic and gravity constraints were respected. The obtained model shows crustal thickness variations from 32 to more than 55 km in certain areas. The thinnest crust with a thickness below 40 km is found beneath the Pericaspian basin, which is covered by a thick sedimentary layer. The thickest crust is located underneath the Ural Mountains as well as in the center of the Volga-Uralian subcraton. In both areas the crustal thickness exceeds 50 km. At the same time, initial forward gravity modeling has shown a gravity misfit of ca. 95 mGal between the measured Bouguer gravity anomaly and the forward calculated gravity field in the central area of the Volga-Uralian subcraton. This misfit was interpreted and modeled as a high-density lower crust which possibly represents underplated material. Our preferred crustal model of the Volga-Uralian subcraton respects the gravity and seismic constraints and reflects the main geological features of the region with Moho thickening in the cratons and under the Ural Mountains and thinning along the Paleoproterozoic rifts, Pericaspian sedimentary basin, and Pre-Urals foredeep.

中文翻译：

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反向和正向重力建模揭示的伏尔加-乌拉尔亚克拉通的地壳结构

摘要。伏尔加-乌拉利亚是东欧克拉通的新太古代最东端。最近对伏尔加-乌拉尔地区的地震研究提供了对该地区地壳结构的新见解。在这项研究中，我们在一个通用工作流程中结合卫星重力和地震数据，对伏尔加-乌拉尔地壳结构进行复杂的研究，这有助于对该地区的进一步盆地分析。有鉴于此，Volgo-Uralian subcraton 的新地壳模型通过逐步方法提出：(1) 反重力建模，然后是 (2) 3D 正向重力建模。首先，应用卫星重力梯度数据反演来确定该地区的莫霍面深度。根据该地区存在的构造单元，地壳和地幔之间的密度差异横向变化，并且模型受到可用的活动地震数据的约束。从重力反演获得的莫霍面不连续面因此被修改和补充，以通过在正向重力建模过程中添加有关沉积盖层、上地壳、下地壳和岩石圈地幔层的信息来定义一个完整的 3D 地壳模型。并尊重重力限制。获得的模型显示某些地区的地壳厚度变化从 32 到 55 公里以上。厚度低于 40 公里的最薄地壳位于 Pericaspian 盆地下方，该盆地被厚厚的沉积层覆盖。最厚的地壳位于乌拉尔山脉下方以及伏尔加-乌拉尔亚克拉通的中心。这两个地区的地壳厚度都超过 50 公里。同时，初始前向重力建模显示重力失配约。伏尔加-乌拉尔亚克拉通中心区域测得的布格重力异常与前向计算的重力场之间为 95 mGal。这种错配被解释和建模为高密度下地壳，可能代表镀层不足的材料。我们首选的伏尔加-乌拉尔亚克拉通地壳模型尊重重力和地震约束，反映了该地区的主要地质特征，克拉通和乌拉尔山脉下莫霍面增厚，沿古元古代裂谷、中海沉积盆地和前乌拉尔深渊。这种错配被解释和建模为高密度下地壳，可能代表镀层不足的材料。我们首选的伏尔加-乌拉尔亚克拉通地壳模型尊重重力和地震约束，反映了该地区的主要地质特征，克拉通和乌拉尔山脉下莫霍面增厚，沿古元古代裂谷、中海沉积盆地和前乌拉尔深渊。这种错配被解释和建模为高密度下地壳，可能代表镀层不足的材料。我们首选的伏尔加-乌拉尔亚克拉通地壳模型尊重重力和地震约束，反映了该地区的主要地质特征，克拉通和乌拉尔山脉下莫霍面增厚，沿古元古代裂谷、中海沉积盆地和前乌拉尔深渊。