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Crustal and thermal structure of the Permian – Jurassic Luangwa – Lukusashi – Luano Rift, Zambia: Implications for strain localization in magma – poor continental rifts
Journal of African Earth Sciences ( IF 2.2 ) Pub Date : 2021-03-01 , DOI: 10.1016/j.jafrearsci.2020.104090
Kitso N. Matende , Estella Atekwana , Kevin Mickus , Mohamed G. Abdelsalam , Eliot A. Atekwana , Rob Evans , Victor N. Nyalugwe , Luelseged Emishaw

Abstract This work uses aeromagnetic, satellite gravity, and ground gravity data to image the thermal and crustal structures beneath the NE-trending Paleozoic - Mesozoic Luangwa – Lukusashi – Luano (LLL) rift in southeastern Zambia. This rift extends between the Precambrian Irumide metacraton in the northwest and the Niassa craton to the southeast and is partially controlled by the NE-trending Mwembeshi suture zone between the two blocks. Although the LLL rift is suggested to have been reactivated by the Southwestern Branch (SWB) of the East African Rift System (EARS), this work did not find shallowing of Curie Point Depth (estimated from the spectral analysis of aeromagnetic data) that would be indicative of elevated heat flow beneath the rift. Three-dimensional inversion of the aeromagnetic data shows a number of magnetized bodies, the largest occurring beneath the central part of the LLL rift and extending to a depth of ∼35 km. Spectral analysis of the satellite gravity data indicates a ∼45 km thick crust beneath the southwestern and central parts and the northeastern tip of the LLL rift. Two-dimensional (2D) forward modeling of the ground gravity data indicates a ∼200 km wide and ∼12 km thick under-plated mafic body (UPMB). These results support limited reactivation of the LLL rift by the SWB of the EARS. Further, extensional strain localization during the onset of the LLL rifting is attributed to the accretion of the UPMB beneath the crust.

中文翻译:

二叠纪-侏罗纪卢安瓜-卢库萨什-赞比亚卢阿诺裂谷的地壳和热结构:岩浆中应变定位的意义-贫瘠的大陆裂谷

摘要 这项工作利用航磁、卫星重力和地面重力数据对赞比亚东南部NE向古生界-中生界卢安瓜-卢库萨什-卢阿诺(LLL)裂谷下的热和地壳结构进行成像。该裂谷在西北部的前寒武纪伊鲁米德元克拉通和东南部的 Niassa 克拉通之间延伸,部分受两个区块之间的 NE 向 Mwembeshi 缝合带控制。尽管 LLL 裂谷被认为已被东非裂谷系统 (EARS) 的西南分支 (SWB) 重新激活,但这项工作并未发现居里点深度(根据航磁数据的光谱分析估计)的变浅。表明裂隙下方的热流升高。航磁数据的三维反演显示了多个磁化体,最大的发生在 LLL 裂谷的中央部分之下,并延伸到约 35 公里的深度。卫星重力数据的光谱分析表明,在 LLL 裂谷的西南部和中部以及东北端下方有大约 45 公里厚的地壳。地面重力数据的二维 (2D) 正演模型表明一个约 200 公里宽、约 12 公里厚的下镀镁铁质体 (UPMB)。这些结果支持 EARS 的 SWB 有限地重新激活 LLL 裂缝。此外,在 LLL 裂谷开始期间的拉伸应变局部化归因于地壳下 UPMB 的吸积。卫星重力数据的光谱分析表明,在 LLL 裂谷的西南部和中部以及东北端下方有大约 45 公里厚的地壳。地面重力数据的二维 (2D) 正演模型表明一个约 200 公里宽、约 12 公里厚的下镀镁铁质体 (UPMB)。这些结果支持 EARS 的 SWB 有限地重新激活 LLL 裂缝。此外,在 LLL 裂谷开始期间的拉伸应变局部化归因于地壳下 UPMB 的吸积。卫星重力数据的光谱分析表明,在 LLL 裂谷的西南部和中部以及东北端下方有大约 45 公里厚的地壳。地面重力数据的二维 (2D) 正演模型表明一个约 200 公里宽、约 12 公里厚的下镀镁铁质体 (UPMB)。这些结果支持 EARS 的 SWB 有限地重新激活 LLL 裂缝。此外,在 LLL 裂谷开始期间的拉伸应变局部化归因于地壳下 UPMB 的吸积。
更新日期:2021-03-01
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