Structure and evolution of the Australian plate and underlying upper mantle from waveform tomography with massive data sets
Structure and evolution of the Australian plate and underlying upper mantle from waveform tomography with massive data sets
复制标题
通过海量数据集波形断层扫描研究澳大利亚板块和底层上地幔的结构和演化
DOI：
10.1093/gji/ggad062
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发表时间：
2023
影响因子：
2.8
通讯作者：
De Laat J
中科院分区：
文献类型：
--
作者：
De Laat J
我们提出了一个新的S波速度层析成像模型的上地幔下的澳大利亚板块及其边界，我们称之为Aus 22。它包括方位角各向异性，并受到90万垂直分量地震图波形的限制，在以澳大利亚大陆为中心的半球进行密度数据采样，使用涵盖该半球的所有现有数据。波形反演提取结构信息的面波，S波和多重S波和约束S波和P波速度和S波方位角各向异性的地壳和上地幔，下到660公里的不连续性。该模型通过分辨率测试和澳大利亚特定位置的面波相速度独立站间测量进行了验证，与以往模型有显著差异。Aus 22可用于在区域尺度上精细地约束澳大利亚板块及其边界的结构和演化。厚，高速（和，推断，冷）超声波岩石圈几乎占据了整个西部和中部的澳大利亚，但显示出实质性的横向异质性。它一直延伸到板块的北方边缘，在那里它与岛弧碰撞，没有俯冲。含金刚石金伯利岩和钾镁煌斑岩矿床下伏于超高压岩石圈，除了最近在利奥波德王造山带发现的含金刚石钾镁煌斑岩。该模型解决了岩石圈东部边界崎岖的问题，提供了塔斯曼线的岩石圈定义。就在塔斯曼线以东，在大陆南部观察到一个中厚岩石圈区域。澳大利亚东部的岩石圈薄而温暖，地震速度低。澳大利亚东部新生代板内火山活动场所均位于薄岩石圈之上。一个低速异常是目前在地幔过渡区（410-660公里深处）下的豪勋爵和塔斯马尼亚热点，温度异常高的指示和一致的深地幔上涌喂养这些热点，也可能是东澳大利亚热点。在新几内亚以下200-410公里深处的高地震速度表明存在板片碎片，可能与澳大利亚板块的俯冲有关。在澳大利亚东北部以下的过渡带中观察到高地震速度，表明存在被困在过渡带中的俯冲岩石圈碎片，可能是澳大利亚前北方大陆边缘的一部分。
We present a new S-wave velocity tomographic model of the upper mantle beneath the Australian Plate and its boundaries that we callAus22. It includes azimuthal anisotropy and was constrained by waveforms from 0.9 million vertical-component seismograms, with the densest data sampling in the hemisphere centred on the Australian continent, using all available data covering this hemisphere. Waveform inversion extracted structural information from surface waves, S- and multiple S-waves and constrained S- and P-wave speeds and S-wave azimuthal anisotropy of the crust and upper mantle, down to the 660-km discontinuity. The model was validated by resolution tests and, for particular locations in Australia with notable differences from previous models, independent inter-station measurements of surface-wave phase velocities.Aus22can be used to constrain the structure and evolution of the Australian Plate and its boundaries in fine detail at the regional scale. Thick, high-velocity (and, by inference, cold) cratonic lithosphere occupies nearly all of western and central Australia but shows substantial lateral heterogeneity. It extends up to the northern edge of the plate, where it collides with island arcs, without subducting. Diamondiferous kimberlites and lamproite deposits are underlain by cratonic lithosphere, except for the most recent diamondiferous lamproites in the King Leopold Orogen. The rugged eastern boundary of the cratonic lithosphere resolved by the model provides a lithospheric definition of the Tasman Line. Just east of the Tasman Line, an area of intermediate-thick lithosphere is observed in the southern part of the continent. The eastern part of Australia is underlain by thin, warm lithosphere, evidenced by low seismic velocities. All the sites of Cenozoic intraplate volcanism in eastern Australia are located on thin lithosphere. A low-velocity anomaly is present in the mantle transition zone (410–660 km depths) beneath the Lord Howe and Tasmanid hotspots, indicative of anomalously high temperature and consistent with a deep mantle upwelling feeding these hotspots and, possibly, also the East Australia hotspot. High seismic velocities at 200–410 km depth below New Guinea indicate the presence of slab fragments, probably linked to the subduction of the Australian Plate. High seismic velocities are observed in the transition zone below northeast Australia and indicate the presence of subducted lithospheric fragments trapped in the transition zone, possibly parts of the former northern continental margin of Australia.