Three-dimensional constrained gravity inversion of Moho depth and crustal structural characteristics at Mozambique continental margin
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Abstract: Mozambique’s continental margin in East Africa was formed during the break-off stage of the east and west Gondwana lands. Studying the geological structure and division of continent-ocean boundary (COB) in Mozambique’s continental margin is considered of great significance to rebuild Gondwana land and understand its movement mode. Along these lines, in this work, the initial Moho was fit using the known Moho depth from reflection seismic profiles, and a 3D multi-point constrained gravity inversion was carried out. Thus, high-accuracy Moho depth and crustal thickness in the study area were acquired. According to the crustal structure distribution based on the inversion results, the continental crust at the narrowest position of the Mozambique Channel was detected. According to the analysis of the crustal thickness, the Mozambique ridge is generally oceanic crust and the COB of the whole Mozambique continental margin is divided.
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Figure 1. Depiction of the topography and main geological structures of the study area, the white circle refers to the OBS station in the area (a); Free-air gravity anomalies in the study area, the dotted lines are magnetic anomaly strips (b); Sedimentary thickness in the study area (c). SB: Somalia Basin; DFZ: Davie Fracture Zone; MozC: Mozambique Channel; BH: Beira High; NNV: northern Natal Valley; MFZ: Mozambique Fracture Zone; nMozR: north Mozambique Ridge; sMozR: south Mozambique Ridge; MB: Mozambique Basin; MadR: Madagascar Range; AG: Ariel Graben; MCP: Mozambique Coastal Plain.
Figure 2. Flowchart of inversion (FAA: free-air anomaly; BGA: Bouguer gravity anomaly).
Figure 3. Gravity effect of the sedimentary layer (a); Bouguer gravity anomaly after correction of sedimentary layer (b).
Figure 4. Comparison of Moho depth gravity inversion results and deep seismic data interpretation results Measuring line MZ07 (a) Measuring line 20070201 (b). The positions of the measuring lines are shown in Fig. 1.
Figure 5. Moho depth in the study area (a); crustal thickness in the study area (b). SB: Somalia Basin; DFZ: Davie Fracture Zone; MozC: Mozambique Channel; BH: Beira High; NNV: northern Natal Valley; MFZ: Mozambique Fracture Zone; nMozR: north Mozambique Ridge; sMozR: south Mozambique Ridge; MB: Mozambique Basin; MadR: Madagascar Range; AG: Ariel Graben; MCP: Mozambique Coastal Plain.
Figure 6. COB distribution in Mozambique continental margin. a. North region; b. south region. The bottom map is crustal thickness. MozC: Mozambique Channel; BH: Beira High; nMozR: north Mozambique Ridge; sMozR: south Mozambique Ridge; AG: Ariel Graben; MCP: Mozambique Coastal Plain.
Figure 7. Crustal thickness map of the Mozambique Channel. The brown translucent area is part of the continental crust. MozC: Mozambique Channel; MB: Mozambique Basin.
Figure 8. Geological interpretation of profile AWI-20140010. The free-air gravity anomaly (a). The magnetic anomaly along the profile are shown (b). Geological interpretation of the profile (c) (Mueller et al., 2016).
Figure 9. P-wave velocity models of profile MZ1 (km/s) (Moulin et al., 2020).
Table 1. OBS constraint points for inversion.
Name of measuring
linesNumber of the used
constraint pointsSource AWI-20140100 25 Vormann et al. (2020) AWI-20140050 25 Vormann et al. (2020) AWI-20140150 20 Vormann and Jokat (2021) AWI-20140130 20 Vormann and Jokat (2021) 20070201 27 Leinweber et al. (2013) 20070202 11 Leinweber et al. (2013) AWI-20140010 37 Mueller et al. (2016) Total 165 
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