Detaset for Global Mantle Gravity Gradient Disturbances and Their Implications on Mantle Dynamics

The variation in mantle density is crucial for understanding mantle structure and dynamics, as well as elucidating the mechanism driving crustal tectonic movements and surface deformation. Mantle gravity and its gradient disturbances serve as primary data for estimating mantle density heterogeneity. However, these gravity signals are masked by the highly heterogeneous crust. In this study, we utilize the latest crustal model, Earth Crustal Model 1 (ECM1), and a spatial-domain three-dimensional gravity gradient forward modeling method to calculate the gravity gradient disturbances of the crustal layers. By removing the crustal response from the global gravity gradient data observed by the GOCE satellite, we obtain the new global mantle gravity gradient disturbances (MGGDs). A detailed analysis of mid-ocean ridges (MORs), cratons, and subduction zones yields the following insights: (1) At MORs, the MGGDs highlight the upwelling of hot mantle materials and the heated, thinned lithosphere beneath the MORs. In Large Igneous Provinces (LIPs), the vertical MGGDs are significantly negative, indicating the low-density composition caused by hot spot activities. (2) Most cratons exhibit high-density anomalies due to their cold, thick lithospheric roots. However, some ancient Archean cratons display low-density anomalies because the compositional changes resulting from the high depletion of lithospheric roots may outweigh the effects of low temperatures on density. (3) At subduction zones, MGGDs reveal subducting plates and the induced mantle convection. High-density subducting plates typically cause positive vertical MGGDs, whereas melting and up mantle flow associated with plate subduction often result in negative vertical gravity gradient disturbances near subduction zones.

地幔密度的变化对于理解地幔结构与动力学、阐明驱动地壳构造运动与地表形变的机制至关重要。地幔重力及其梯度扰动是估算地幔密度非均质性的核心数据，但这些重力信号会被高度非均质性的地壳所掩盖。本研究采用最新地壳模型——地球地壳模型1（Earth Crustal Model 1, ECM1），结合空间域三维重力梯度正演方法，计算得到地壳层的重力梯度扰动。通过移除GOCE卫星观测的全球重力梯度数据中的地壳响应分量，我们获取了全新的全球地幔重力梯度扰动（MGGDs）。通过对洋中脊（mid-ocean ridges, MORs）、克拉通与俯冲带开展详细分析，得到如下认识：(1) 在洋中脊区域，MGGDs清晰反映了热地幔物质上涌以及洋中脊下方被加热减薄的岩石圈；在大火成岩省（Large Igneous Provinces, LIPs）中，垂直方向的MGGDs呈现显著负值，指示热点活动引发的低密度组分特征。(2) 多数克拉通因存在冷而厚的岩石圈根而表现为高密度异常；但部分古老的太古宙克拉通却呈现低密度异常，这是由于岩石圈根发生高度亏损引发的组分变化，其影响超过了低温对密度的调控作用。(3) 在俯冲带区域，MGGDs揭示了俯冲板片与诱发的地幔对流特征：高密度俯冲板片通常会引发正的垂直MGGDs，而与板块俯冲相关的熔融与地幔上升流，往往会在俯冲带附近形成负的垂直重力梯度扰动。