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首页> 外文期刊>Journal of Volcanology and Geothermal Research >The Managua Graben and Las Sierras-Masaya volcanic complex (Nicaragua); pull-apart localization by an intrusive complex: results from analogue modeling
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The Managua Graben and Las Sierras-Masaya volcanic complex (Nicaragua); pull-apart localization by an intrusive complex: results from analogue modeling

机译：Managua Graben和Las Sierras-Masaya火山群（尼加拉瓜）；侵入式复合体的局部拉动：模拟建模的结果

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There is a well-documented association between pull-apart basins in strike-slip zones and large volcanic caldera complexes. Las Sierras-Masaya volcanic complex, Nicaragua, is a large basaltic lava and ignimbrite shield with nested calderas. The widest caldera is partly underlain by a large and dense intrusive complex, evidenced by a positive gravity anomaly. The Las Sierras Caldera, relating to this cumulate complex, is less than 30,000 years old and is probably still hot and ductile. The inner Masaya Caldera hosts an active magmatic system. The volcanic complex is in a dextral transtensional tectonic context of the Nicaraguan Depression. The highly active Managua Graben is on the northern part of the volcano. We speculate that the graben and volcano are linked tectonically, with the graben initiating in response of a regional stress field modified around the dense, ductile intrusive complex. Previous field work and reappraisal of structures with digital elevation model morphological analysis show that the volcano is surrounded by a rhombic fault pattern that may form a nascent pull-apart basin. We have done scaled analogue models to test the effect of intrusion density and rheology anomalies on strike-slip fault geometries. The models show that intrusion density variations alone do not significantly change fault patterns. In contrast, ductile rocks (silicone in the models as analogue for hot mafic intrusive rocks) markedly alter strike-slip fault patterns. In transtension the presence of a ductile intrusion causes the formation of a pull-apart, while in pure strike-slip or transpression, uplift and thrusting is generated. Pull-apart and uplift structures are rhomb-shaped even when the ductile inclusion is circular. We conclude that a pull-apart is developing at Las Sierras-Masaya volcanic complex in response to the transtensive regional deformation regime and the dense, ductile intrusive complex. We suggest that the volcano and graben are one dynamic system and should be monitored as one entity.
机译：在走滑带的拉脱盆地与大型火山破火山口复合体之间存在着据充分记录的关联。尼加拉瓜的Las Sierras-Masaya火山群是一个大型的玄武岩熔岩和易燃物护层，带有嵌套的火山口。最宽的破火山口部分地被大型且密集的侵入性复合物所覆盖，这由正重力异常所证明。与这个复杂的综合体有关的Las Sierras Caldera不到30,000年的历史，并且可能仍然炎热而易碎。内部的Masaya破火山口拥有活跃的岩浆系统。火山复合体处于尼加拉瓜pression陷的右旋张性构造环境中。活跃的Managua Graben位于火山的北部。我们推测，地en和火山在构造上是联系在一起的，地in是在密集，延性侵入性复合体周围改变的区域应力场的作用下引发的。先前的野外工作和使用数字高程模型形态分析对结构进行的重新评估显示，火山周围环绕着菱形断层，可能形成新生的拉脱盆地。我们已经完成了按比例缩放的模拟模型，以测试侵入密度和流变异常对走滑断层几何形状的影响。这些模型表明，单独的入侵密度变化不会显着改变故障模式。相反，可延展岩石（模型中的硅树脂类似于热镁铁质侵入岩）明显改变了走滑断层的形态。在拉力作用下，韧性侵入的存在导致拉开的形成，而在纯走滑或压阻作用下，则产生隆起和推动作用。即使延展性夹杂物是圆形的，拉拔结构和隆起结构也是菱形的。我们得出结论，拉斯拉塞拉斯-马萨亚火山综合体正在形成拉脱现象，以应对跨区域变形体制和密集，延性的侵入性复合体。我们建议火山和and沼是一个动态系统，应作为一个整体进行监控。

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