Consequences of plume-lithosphere interactions
Consequences of plume-lithosphere interactions
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DOI：
10.1144/gsl.sp.1992.068.01.04
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发表时间：
1992
期刊：
影响因子：
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通讯作者：
Andrew D. Saunders;Michael Storey;R. W. Kent;M. Norry
中科院分区：
文献类型：
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作者：
Andrew D. Saunders;Michael Storey;R. W. Kent;M. Norry
摘要地幔柱上方岩石圈的分裂或变薄可导致大量熔体的产生，从而形成大的火成岩省（LIPs）。LIP的例子包括大陆溢流玄武岩区和海洋高原。来自Ontong Java高原、瑙鲁盆地和Manihiki高原的玄武岩样品是最大的LIP之一，其同位素组成在洋岛玄武岩范围内。然而，大多数大陆玄武岩记录了它们喷发时岩石圈的微量元素和同位素贡献。因此，我们无法调和现有的成分数据与模型，推导出同位素和大离子亲石元素富集的大陆溢流玄武岩的特点，完全从亚岩石圈地幔柱来源。地幔源的组合表示，与热能被提供的大量熔体从羽，和大陆溢流玄武岩的岩石圈成分被继承的污染羽源熔体低熔点含水和碳酸盐馏分在岩石圈。连续注入的地幔柱衍生的熔体加热岩石圈，降低其粘度，使其易于破裂，如果允许的区域板块力量。此外，岩石圈，包括机械边界层，可能会被从下面的热剥离变薄，使地幔柱上升和进一步膨胀。这样的系统具有正反馈的潜力，导致快速熔体生成。虽然我们不排除最近的模型LIP的形成，需要一个新的地幔柱的突然影响，我们赞成一个模型，即热异常逐步建立，孵化下一个稳定状态的岩石圈帽。
Abstract Splitting or thinning of lithosphere above a mantle plume can result in voluminous melt generation, leading to the formation of large igneous provinces, or LIPs. Examples of LIPs include continental flood basalt provinces and oceanic plateaus. Basaltic samples from the Ontong Java Plateau, Nauru Basin and Manihiki Plateau, which are among the largest of the LIPs, have isotopic compositions within the range of ocean island basalts. The majority of continental basalts, however, record a trace element and isotopic contribution from the lithosphere through which they have erupted. We are thus unable to reconcile the available compositional data with models which derive the isotopic and large-ion lithophile element-enriched character of continental flood basalts solely from sub-lithospheric mantle plume sources. A combination of mantle sources is indicated, with the thermal energy being supplied by voluminous melts from a plume, and the lithospheric components in continental flood basalts being inherited by contamination of plume-derived melts by low melting point hydrous and carbonated fractions in the lithosphere. Successive injection of plume-derived melts serves to heat the lithosphere, reducing its viscosity and making it susceptible to rupture if allowed by regional plate forces. Furthermore, the lithosphere, including the mechanical boundary layer, may be thinned by thermal stripping from below, allowing the plume mantle to ascend and decompress further. Such a system has the potential for positive feedback leading to rapid melt generation. While we do not exclude recent models of LIP formation which require the sudden impact of a new mantle plume, we favour a model whereby the thermal anomaly builds gradually, incubating beneath a steady-state lithospheric cap.