Journal of African Earth Sciences ( IF 2.3 ) Pub Date : 2021-04-01 , DOI: 10.1016/j.jafrearsci.2021.104206 Cyrille Donald Njiteu Tchoukeu , Charles Antoine Basseka , Yvette Poudjom Djomani , Sonia Rousse , Jacques Etame , Muriel Llubes , Lucia Seoane , Constantin Som Mbang , Albert Eyike Yomba
The Bangui Magnetic Anomaly (BMA) is one of the largest magnetic anomalies in the world whose origin is still not known. This research investigated the crustal thickness, Curie depths and thermal structures in the Central African sub-regions – Cameroon, Central African Republic and adjacent countries – which are largely characterized by the Bangui Magnetic Anomaly. To achieve a better understanding and clearer idea of the location of the possible sources of the BMA, analyses of geothermal structures were conducted. Two potential methods were used: gravity to evaluate the crustal thickness and magnetics for geothermal analysis. Spectral analysis of gravity data shows that crustal thickness range between 14 and 55 km. The highest depths were found in Central African Republic. The lower values of crustal thickness were obtained in South-Chad basin with a minimum of roughly 14 km. Geothermal analysis is carried out using the Curie point depth, thermal gradient and heat-flow evaluations. The results show that the BMA is related to a thick crust of roughly 40 km. Depth to the bottom of possible sources does not exceed the lower crust. The mean Curie point depth estimated is 38 km with an error of ±2 km. Geothermal results also show the difference in the thermal behaviour between the crust in the Pan African and Precambrian domain. The mobile zone which constitutes the Pan African domain is associated with a thin crust of high heat-flow values of 65 mW/m2. However, the Precambrian domain beneath the BMA is associated with a thick crust with lower heat-flow values (roughly 45 mW/m2). The difference between crustal thickness and Curie point depths shows that all the sources of the BMA are crustal. The present results are in favour of a geological origin for the Bangui Magnetic anomaly.
中文翻译:
从喀麦隆到中非共和国的地壳厚度,到磁源底部的深度和地壳的热结构:初步结果有助于更好地了解班吉磁异常的起源
班吉磁异常(BMA)是世界上最大的磁异常之一,其起源尚不清楚。这项研究调查了中非次区域(喀麦隆,中非共和国和邻国)的地壳厚度,居里深度和热力结构,其主要特征是班吉磁异常。为了更好地了解和更清楚地了解BMA的可能来源,对地热结构进行了分析。使用了两种可能的方法:重力法评估地壳厚度;地磁法进行地热分析。重力数据的频谱分析表明,地壳厚度在14至55 km之间。在中非共和国发现的深度最大。在南乍得盆地,地壳厚度较低,最小约14 km。地热分析使用居里点深度,热梯度和热流评估。结果表明,BMA与大约40 km的厚壳有关。可能来源底部的深度不超过下地壳。估计的居里点平均深度为38 km,误差为±2 km。地热结果还表明,泛非地区和前寒武纪地区的地壳之间的热行为有所不同。构成泛非区域的活动区与高热流值为65 mW / m 2的薄壳相关。但是,BMA下的前寒武纪区域与厚壳壳相关,而后者的热流值较低(大约为45 mW / m 2)。地壳厚度和居里点深度之间的差异表明,BMA的所有来源都是地壳。目前的结果有利于班吉磁异常的地质成因。