Cenozoic extension in the Kenya Rift from low-temperature thermochronology: Links to diachronous spatiotemporal evolution of rifting in East Africa
Cenozoic extension in the Kenya Rift from low-temperature thermochronology: Links to diachronous spatiotemporal evolution of rifting in East Africa
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DOI：
10.1002/2015tc003949
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发表时间：
2015-12-01
期刊：
影响因子：
4.2
通讯作者：
Strecker, Manfred R.
中科院分区：
文献类型：
--
作者：
Acosta, Veronica Torres;Bande, Alejandro;Strecker, Manfred R.
裂谷肩冷却史和裂谷盆地沉降史是重建伸展地动力省形态构造演化、评价其古环境变化作用和盆地充填资源潜力的基础。我们在肯尼亚裂谷北部和中部的Samburu Hills和Elgeyo悬崖的磷灰石裂变径迹和锆石(U-Th)/He数据表明，这两个地区的热演化大致一致。热模拟结果支持早古新世以来的三阶段热历史。第一阶段（类似于65-50 Ma）的特征是裂谷肩的快速冷却，可能与现在位于图尔卡纳凹陷地下和肯尼亚北部东部地区的安扎裂谷盆地的断裂和沉积同时发生。在第二阶段，由于地表条件稳定、挖掘缓慢或下沉，在45至15 Ma之间发生了非常缓慢的冷却或轻微的再加热。第三阶段包括重新开始的快速冷却，温度大约为15毫安。最后的冷却代表了裂谷作用的最新阶段，裂谷作用发生在大范围的洪水-phonolite侵位之后，并通过裂谷肩隆起、断裂、盆地填充、持久的火山作用和侵蚀形成了今天的地貌。与东非裂谷系统其他部分的热年代学和地质数据相比，伸展似乎是历时性的，空间上不同的，部分重叠的，可能是由地幔驱动过程和地壳非均质性之间的相互作用驱动的，而不是先前提出的地幔柱的南北迁移影响。
The cooling history of rift shoulders and the subsidence history of rift basins are cornerstones for reconstructing the morphotectonic evolution of extensional geodynamic provinces, assessing their role in paleoenvironmental changes and evaluating the resource potential of their basin fills. Our apatite fission track and zircon (U-Th)/He data from the Samburu Hills and the Elgeyo Escarpment in the northern and central sectors of the Kenya Rift indicate a broadly consistent thermal evolution of both regions. Results of thermal modeling support a three-phased thermal history since the early Paleocene. The first phase (similar to 65-50 Ma) was characterized by rapid cooling of the rift shoulders and may be coeval with faulting and sedimentation in the Anza Rift basin, now located in the subsurface of the Turkana depression and areas to the east in northern Kenya. In the second phase, very slow cooling or slight reheating occurred between similar to 45 and 15 Ma as a result of either stable surface conditions, very slow exhumation, or subsidence. The third phase comprised renewed rapid cooling starting at similar to 15 Ma. This final cooling represents the most recent stage of rifting, which followed widespread flood-phonolite emplacement and has shaped the present-day landscape through rift shoulder uplift, faulting, basin filling, protracted volcanism, and erosion. When compared with thermochronologic and geologic data from other sectors of the East African Rift System, extension appears to be diachronous, spatially disparate, and partly overlapping, likely driven by interactions between mantle-driven processes and crustal heterogeneities, rather than the previously suggested north-south migrating influence of a mantle plume.