The Impact of Complex Volcanic Plumbing on the Nature of Seismicity in the Developing Magmatic Natron Rift, Tanzania
The Impact of Complex Volcanic Plumbing on the Nature of Seismicity in the Developing Magmatic Natron Rift, Tanzania
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DOI：
10.3389/feart.2020.609805
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发表时间：
2021-02-23
影响因子：
2.9
通讯作者：
Ruempker, Georg
中科院分区：
文献类型：
--
作者：
Reiss, Miriam Christina;Muirhead, James D.;Ruempker, Georg
在活跃的裂谷内限制复杂的3D火山管道系统的结构及其对裂谷过程的影响对于检查裂谷段中的断层，岩浆和岩浆流体之间的相互作用至关重要。东非裂谷系统的Natron盆地为研究这些过程提供了理想的位置，这是由于其最近在Oldoinyo Lengai正在进行的岩浆岩石构造活动和正在进行的活性碳酸盐火山岩。在这里，我们报告了跨越Oldoinyo Lengai，Naibor Soito火山场和Gelai Volcano的长10个月临时地震网络的地震平面解决方案。我们定位6,827次具有M -L -0.85至3.6的地震，这些地震与该地区的先前和正在进行的岩浆和火山活动以及区域构造延伸有关。我们观察到地震态度与奥尔多尼奥·林格（Oldoinyo Lengai）北部和南部的17公里深度相似，浅层（3-10公里），包括两只蜂群。最深的地震性（类似于20公里）发生在先前成像的岩浆体上方，而Naibor Soito下方则发生。这些地震性模式揭示了复杂的火山管道系统的详细图像，从而支持浅层和深层岩浆之间的潜在横向和垂直连接，在这些岩浆和深层岩浆中，流体和融化到表面的转运均通过堤防和斜视的侵入来促进。焦点机制在空间上变化。 T轴趋势显示了Gelai附近的WNW-ESE扩展，而在Oldoinyo Lengai附近观察到了滑滑机制和P轴的径向趋势。这些数据支持压力状态的局部变化，这是由于火山建筑物负荷和岩浆驱动的应力变化在区域扩展应力场上施加的。我们的结果表明，南部的纳特隆盆地是一个分段的裂谷系统，其中流体优先在菌株从边界断层转移到发育中的岩浆裂裂片的区域中优先垂直和侧向渗透。
Constraining the architecture of complex 3D volcanic plumbing systems within active rifts, and their impact on rift processes, is critical for examining the interplay between faulting, magmatism and magmatic fluids in developing rift segments. The Natron basin of the East African Rift System provides an ideal location to study these processes, owing to its recent magmatic-tectonic activity and ongoing active carbonatite volcanism at Oldoinyo Lengai. Here, we report seismicity and fault plane solutions from a 10 month-long temporary seismic network spanning Oldoinyo Lengai, Naibor Soito volcanic field and Gelai volcano. We locate 6,827 earthquakes with M-L -0.85 to 3.6, which are related to previous and ongoing magmatic and volcanic activity in the region, as well as regional tectonic extension. We observe seismicity down to similar to 17 km depth north and south of Oldoinyo Lengai and shallow seismicity (3-10 km) beneath Gelai, including two swarms. The deepest seismicity (similar to down to 20 km) occurs above a previously imaged magma body below Naibor Soito. These seismicity patterns reveal a detailed image of a complex volcanic plumbing system, supporting potential lateral and vertical connections between shallow- and deep-seated magmas, where fluid and melt transport to the surface is facilitated by intrusion of dikes and sills. Focal mechanisms vary spatially. T-axis trends reveal dominantly WNW-ESE extension near Gelai, while strike-slip mechanisms and a radial trend in P-axes are observed in the vicinity of Oldoinyo Lengai. These data support local variations in the state of stress, resulting from a combination of volcanic edifice loading and magma-driven stress changes imposed on a regional extensional stress field. Our results indicate that the southern Natron basin is a segmented rift system, in which fluids preferentially percolate vertically and laterally in a region where strain transfers from a border fault to a developing magmatic rift segment.