On the origin of recent intraplate volcanism in Australia
On the origin of recent intraplate volcanism in Australia
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DOI：
10.1130/g36093.1
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发表时间：
2014-12-01
期刊：
影响因子：
5.8
通讯作者：
Rawlinson, Nicholas
中科院分区：
文献类型：
--
作者：
Davies, D. Rhodri;Rawlinson, Nicholas
许多板内火山省似乎并非起源于板块边界作用或上涌的地幔柱。边缘驱动对流（EDC）是一种小规模的对流不稳定性（由岩石圈厚度的局部变化引起）将热地幔物质向上置换，为这种火山作用提供了另一种假设。最近，由于靠近克拉通边缘，EDC被假定为澳大利亚第四纪板内火山活动的触发因素。然而，澳大利亚大陆的前寒武纪盾区有一个至少10000公里长的边界，而新火山省（NVP）被包含在一个400 x 100公里的区域内。这就对EDC作为一种因果机制产生了疑问，除非能解释单一地点的成核。本文采用地震层析成像和地球动力学模拟相结合的方法，首次表明(1)NVP的来源局限于上地幔；(2)由于岩石圈厚度的三维变化和板块运动引起的剪切流，EDC引发的地幔上升流在NVP下方被局部化和强化。这项研究有助于解决岩石圈厚度的阶梯式变化（发生在克拉通边缘和被动边缘）为什么只在孤立的位置产生火山活动的全球性难题。
Many intraplate volcanic provinces do not appear to originate from plate-boundary processes or upwelling mantle plumes. Edge-driven convection (EDC), where a small-scale convective instability (induced by local variations in lithospheric thickness) displaces hot mantle material upward, provides an alternative hypothesis for such volcanism. Recently, EDC has been postulated as the trigger for Quaternary intraplate volcanism in Australia, due to the proximity of a craton edge. However, the Precambrian shield region of the Australian continent has a boundary that is at least 10,000 km long, yet the Newer Volcanics Province (NVP) is contained within a 400 x 100 km region. This brings into question EDC as a causal mechanism, unless nucleation at a single location can be explained. Here, we use a combination of seismic tomography and geodynamic modeling to show, for the first time, that (1) the source of the NVP is restricted to the upper mantle, and (2) mantle upwelling triggered by EDC is localized and intensified beneath the NVP as a result of three-dimensional variations in lithospheric thickness and plate motion-induced shear flow. This study helps to solve the global puzzle of why step changes in lithospheric thickness, which occur along craton edges and at passive margins, produce volcanism only at isolated locations.