Continental rifting at magmatic centres: structural implications from the Late Quaternary Menengai Caldera, central Kenya Rift
Continental rifting at magmatic centres: structural implications from the Late Quaternary Menengai Caldera, central Kenya Rift
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岩浆中心的大陆裂谷：肯尼亚中部裂谷晚期第四纪 Menengai 火山口的结构影响
DOI：
10.1144/jgs2019-021
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发表时间：
2019
影响因子：
2.7
通讯作者：
Strecker
中科院分区：
文献类型：
--
作者：
Melnick;Strecker
裂谷中破火山口的构造演化有助于表征岩浆活动、长波长地壳变形与沿裂谷轴沿着构造变形带形成的时空关系。我们记录的结构特征。36万年的老Menengai火山口位于一个年轻的区域内的延伸在肯尼亚裂谷中部。 野外测绘和高分辨率数字地表模型表明，垂直于区域ESE-WNW延伸方向的NNE走向全新世正断层主导了裂谷的内部部门。在破火山口内部，这些结构被坍塌后的穹隆和岩浆中心的断层所覆盖，导致斜滑的正断层形成复活地垒。放射性碳测年的断层单元年轻的5 ka cal BP和古海岸线的湖泊在非洲潮湿时期形成的纳库鲁盆地表明，火山活动和断层活动的内部和附近的Menengai必须在全新世持续。 我们的分析证实，破火山口位于一个延伸的裂谷段的中心，并表明其他岩浆中心和年轻的断层带沿着肯尼亚裂谷的火山构造轴可能构成断层的成核点，最终促进未来的大陆分裂。补充材料：40 Ar/39 Ar放射性测年数据表可在：https://doi.org/10.6084/m9.figshare.c.4647818
The structural evolution of calderas in rifts helps to characterize the spatiotemporal relationships between magmatism, long wavelength crustal deformation and the formation of tectonic deformation zones along the rift axis. We document the structural characteristics of thec.36 ka old Menengai Caldera located within a young zone of extension in the central Kenya Rift. Field mapping and high-resolution digital surface models show that NNE-striking Holocene normal faults perpendicular to the regional ESE–WNW extension direction dominate the interior sectors of the rift. Inside the caldera, these structures are overprinted by post-collapse doming and faulting of the magmatic centre, resulting in obliquely slipping normal faults bounding a resurgence horst. Radiocarbon dating of faulted units as young as 5 ka cal BP and the palaeo-shorelines of a lake formed during the African Humid Period in the Nakuru Basin indicate that volcanism and fault activity inside and in the vicinity of Menengai must have been sustained during the Holocene. Our analysis confirms that the caldera is located at the centre of an extending rift segment and suggests that other magmatic centres and young zones of faulting along the volcano-tectonic axis of the Kenya Rift may constitute nucleation points of faulting that ultimately foster future continental break-up.Supplementary material:40Ar/39Ar radiometric dating data table is available at: https://doi.org/10.6084/m9.figshare.c.4647818
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