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Geodynamic processes inferred from Moho and Curie depths in Central and Southern African Archean Cratons
Tectonophysics ( IF 2.7 ) Pub Date : 2021-07-20 , DOI: 10.1016/j.tecto.2021.228993
Opeyemi Joshua Akinrinade 1, 2 , Chun-Feng Li 1, 3, 4 , Ademolawa John Afelumo 1
Affiliation  

Central and Southern Africa is home to major Archean Cratons, flanked by Proterozoic mobile belts. The region is characterized by anomalously high topography and shallow Curie depth (Zb). Factors controlling topography and Zb anomalies in old continental crusts remain poorly understood. In this study, we present high-resolution Moho undulation (Zm) derived with gravity spectral technique. Archean Cratons and Proterozoic belts are mostly characterized by deep Moho (>36 km), whereas the Moho depths in Mozambique belts is mostly shallow (~26 to 41 km). Extremely shallow Zb (<10 km) is dominant in Archean Cratons, whereas intermediate Zb (10–25 km) is prevalent in the mobile belts. The Curie points are mostly above the Moho. Low surface heat flow (Qs) in Archean Cratons indicate that Zb is not correlated with thermal perturbation. Shallow Zb are mostly found in areas with low Vp/Vs ratio, predominantly felsic lower crust and sharp Moho. Shallow Zb also correlate with intense metasomatism and mineral enrichment, as well as depletion in basaltic components and geochemical overprinting by multiple episodes of melt and fluid infiltration. Crustal composition is the main factor that controls shallow Zb in Central and Southern Africa Archean Cratons. The regional elevated topography is not due to thermal perturbation as mostly argued by mantle plume hypothesis, but may be caused by regional thermo-chemical mantle upwelling dominated by composition.



中文翻译:

从非洲中部和南部太古代克拉通的莫霍面和居里深度推断的地球动力学过程

非洲中部和南部是主要太古代克拉通的所在地,两侧是元古代移动带。该地区的特点是异常高的地形和浅的居里深度 (Z b )。旧大陆地壳中控制地形和Z b异常的因素仍然知之甚少。在这项研究中,我们提出了用重力光谱技术导出的高分辨率莫霍面起伏 (Z m )。太古宙克拉通和元古代带的主要特征是深莫霍面(>36 公里),而莫桑比克带的莫霍面深度大多较浅(~26 至 41 公里)。极浅的 Z b (<10 km) 在太古代克拉通中占主导地位,而中间的 Z b(10-25 公里)在移动带中很普遍。居里点大多在莫霍面之上。太古代克拉通的低表面热流 (Q s ) 表明 Z b与热扰动无关。浅层 Z b主要出现在 V p /V s比值低的区域,主要是长英质下地壳和锋利的莫霍面。浅层 Z b还与强烈的交代作用和矿物富集,以及玄武岩成分的枯竭和多次熔融和流体渗透造成的地球化学叠印有关。地壳成分是控制浅Z b的主要因素在非洲中部和南部太古代克拉通。区域抬高的地形不是由地幔柱假说所争论的热扰动引起的,而可能是由成分主导的区域热化学地幔上涌引起的。

更新日期:2021-08-01
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