Plume-subduction interaction in southern Central America: Mantle upwelling and slab melting
Plume-subduction interaction in southern Central America: Mantle upwelling and slab melting
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DOI：
10.1016/j.lithos.2010.10.008
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发表时间：
2011-01-01
期刊：
影响因子：
3.5
通讯作者：
Swisher, Carl, III
中科院分区：
文献类型：
--
作者：
Gazel, Esteban;Hoernle, Kaj;Swisher, Carl, III
中美洲南部的火山前缘以其类似于加拉帕戈斯OIB的地球化学特征而闻名。一套全面的地球化学，同位素和地质年代学数据收集的体积较小的碱性玄武岩和埃达克岩被用来更好地约束地幔和俯冲岩浆成分，并测试不同的模型，解释这个OIB签名在弧设置。我们报告了弧后碱性火山活动向西北方向的迁移，与弧平行地幔流模型一致，以及埃达克岩向东南方向的迁移，可能跟踪巴拿马断裂带与中美洲海沟相交的三重连接点的东移。埃达克岩的主量和微量元素组成与地幔楔源熔融后被板片熔体交代而产生的岩浆一致。碱性岩浆仅限于没有俯冲板块地震证据的地区。碱性岩浆的地球化学特征主要受软流圈上涌的控制，俯冲组分的贡献较小。从碱性玄武岩原生岩浆计算的地幔位温从上新世的接近环境地幔（类似于1380-1410摄氏度）增加到年轻单元的类似于1450摄氏度。计算出的这些原生岩浆的初始熔融压力在石榴子石稳定场（3.0-2.7 GPa）。平均最终熔融压力在2.7 ~ 2.5GPa之间，这被解释为岩石圈-软流圈边界在85-90 km处。我们提供了一个大地构造模型，整合了这里提出的各种观测。板块在加拉帕戈斯轨迹与弧碰撞后分离（类似于10-8 Ma）。拆离使较热的软流圈流入地幔楔。热软流圈的涌入解释了地幔潜在温度的增加，弧后碱性熔岩的西北迁移，跟踪热软流圈的通道，以及在火山前的板熔融签名的存在所造成的回收加拉帕戈斯热点轨道。(C)2010 Elsevier BV保留所有权利。
The volcanic front in southern Central America is well known for its Galapagos OIB-like geochemical signature. A comprehensive set of geochemical, isotopic and geochronological data collected on volumetrically minor alkaline basalts and adakites were used to better constrain the mantle and subduction magma components and to test the different models that explain this OIB signature in an arc setting. We report a migration of back-arc alkaline volcanism towards the northwest, consistent with arc-parallel mantle flow models, and a migration towards the southeast in the adakites possibly tracking the eastward movement of the triple junction where the Panama Fracture Zone intersects the Middle America Trench. The adakites major and trace element compositions are consistent with magmas produced by melting a mantle-wedge source metasomatized by slab derived melts. The alkaline magmas are restricted to areas that have no seismic evidence of a subducting slab. The geochemical signature of the alkaline magmas is mostly controlled by upwelling asthenosphere with minor contributions from subduction components. Mantle potential temperatures calculated from the alkaline basalt primary magmas increased from close to ambient mantle (similar to 1380-1410 degrees C) in the Pliocene to similar to 1450 degrees C in the younger units. The calculated initial melting pressures for these primary magmas are in the garnet stability field (3.0-2.7 GPa). The average final melting pressures range between 2.7 and 2.5 GPa, which is interpreted as the lithosphere-asthenosphere boundary at similar to 85-90 km. We provide a geotectonic model that integrates the diverse observations presented here. The slab detached after the collision of the Galapagos tracks with the arc (similar to 10-8 Ma). The detachment allowed hotter asthenosphere to flow into the mantle wedge. This influx of hotter asthenosphere explains the increase in mantle potential temperatures, the northwest migration in the back-arc alkaline lavas that tracks the passage of the hotter asthenosphere, and the presence of a slab melting signature in the volcanic front caused by recycling of Galapagos Hotspot tracks. (C) 2010 Elsevier B.V. All rights reserved.