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Thermal and Compositional Anomalies of the Australian Upper Mantle From Seismic and Gravity Data
Geochemistry, Geophysics, Geosystems ( IF 4.480 ) Pub Date : 2020-09-25 , DOI: 10.1029/2020gc009305
Magdala Tesauro 1, 2 , Mikhail K. Kaban 3, 4 , Alan R. A. Aitken 5
Affiliation  

To discern temperature and compositional variations of the Australian upper mantle, we apply an integrative technique, which jointly interprets seismic tomography and gravity data. The final thermal model, obtained by changing the upper mantle composition according to the density variations, shows temperatures higher by 100–150°C in the Archean and Proterozoic upper mantle, with respect to the initial model based on a uniform “fertile” composition. In the North and West Australian cratons, the upper mantle is cold, with composition depleted in heavy constituents. This suggests the presence of an Archean lithosphere, which remained relatively undisturbed through the Proterozoic. Central Australia is predominantly characterized by a thick, low‐temperature lithosphere having a more fertile composition. Its shallow part is characterized by a thin layer of low‐velocity mantle, which is interpreted by our results as a thermal anomaly. However, this high‐temperature anomaly is hard to reconcile with the tectonic history of the region. A low‐density mineral phase, such as amphibole, may reduce the density relative to our assumed composition. Furthermore, we observe larger iron depletion in the Western Australian Craton than in the Proterozoic terranes. At the depths larger than 150 km, the depletion becomes negligible beneath the Proterozoic regions, while it also persists in the Western Australian Craton at the depths larger than 200 km.

中文翻译:

从地震和重力数据看澳大利亚上地幔的热和成分异常

为了识别澳大利亚上地幔的温度和成分变化,我们采用了一种综合技术,该技术可以共同解释地震层析成像和重力数据。通过根据密度变化改变上地幔成分获得的最终热力模型显示,与基于统一“肥沃”成分的初始模型相比,太古代和元古代上地幔的温度升高了100–150°C。在北澳大利亚和西澳大利亚的克拉通中,上地幔是冷的,其组成中的重组分耗尽。这表明存在一个太古宙岩石圈,它在元古代一直保持相对不受干扰。澳大利亚中部地区的主要特征是稠密的低温岩石圈,其组成更加肥沃。它的浅部特征是低速地幔的薄层,我们的结果将其解释为热异常。但是,这种高温异常很难与该地区的构造历史相吻合。低密度的矿物相(如闪石)可能会降低密度(相对于我们的假设组成)。此外,我们发现西澳大利亚克拉通的铁耗竭比元古代的铁耗竭更大。在大于150 km的深度处,在元古代地区之下的消耗几乎可以忽略不计,而在大于200 km的深度的西澳大利亚克拉通中也持续存在。例如闪石,可能会降低密度。此外,我们发现西澳大利亚克拉通的铁耗竭比元古代的铁耗竭更大。在大于150 km的深度处,在元古代地区之下的消耗几乎可以忽略不计,而在大于200 km的深度的西澳大利亚克拉通中也持续存在。例如闪石,可能会降低密度。此外,我们发现西澳大利亚克拉通的铁耗竭比元古代的铁耗竭更大。在大于150 km的深度处,在元古代地区之下的消耗几乎可以忽略不计,而在大于200 km的深度的西澳大利亚克拉通中也持续存在。
更新日期:2020-10-29
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