Seismic imaging of a mid-lithospheric discontinuity beneath Ontong Java Plateau
Seismic imaging of a mid-lithospheric discontinuity beneath Ontong Java Plateau
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DOI：
10.1016/j.epsl.2016.06.026
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发表时间：
2016-09
影响因子：
5.3
通讯作者：
S. Tharimena;C. Rychert;N. Harmon
中科院分区：
文献类型：
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作者：
S. Tharimena;C. Rychert;N. Harmon
摘要 翁通爪哇高原（OJP）是一个巨大的、完全淹没的火山大厦，据推测是在大约 90 和 120 年前的大规模羽流融化事件中形成的。它目前正在抵抗俯冲到北所罗门海沟。高原的大小和浮力、地幔柱熔化的历史以及当前与俯冲带的相互作用都与大陆形成的特征和假设机制相似。然而，这个高原地处偏远、神秘莫测，其原始大陆的潜力也存在争议。我们使用SS前兆对翁通爪哇高原下方的地震不连续结构进行成像。我们对 28±4 km 处的速度随深度增加的情况进行了成像，与莫霍面一致。此外，我们还发现速度在 80±5 km 和 282±7 km 深度处降低。在海洋和大陆下面经常观察到 60-100 公里深度的不连续性。然而，与周围海洋区域相比，282公里处的不连续性是异常的；根据之前的结果，这可能表明 OJP 下方有一个厚厚的粘性根。如果存在这样的根，那么 80 公里处的不连续面与在大陆下方观察到的中岩石圈不连续面 (MLD) 具有一定的相似性。一种可能性是，类似于形成 OJP 的羽流熔化事件，可能会导致 MLD 深度范围的不连续性。在俯冲开始之前，地幔柱与板块的相互作用可能是太古宙某些大陆MLD形成的机制。
Abstract Ontong Java Plateau (OJP) is a huge, completely submerged volcanic edifice that is hypothesized to have formed during large plume melting events∼ 90 and 120 My ago. It is currently resisting subduction into the North Solomon trench. The size and buoyancy of the plateau along with its history of plume melting and current interaction with a subduction zone are all similar to the characteristics and hypothesized mechanisms of continent formation. However, the plateau is remote, and enigmatic, and its proto-continent potential is debated. We use SS precursors to image seismic discontinuity structure beneath Ontong Java Plateau. We image a velocity increase with depth at 28±4 km consistent with the Moho. In addition, we image velocity decreases at 80±5 km and 282±7 km depth. Discontinuities at 60–100 km depth are frequently observed both beneath the oceans and the continents. However, the discontinuity at 282 km is anomalous in comparison to surrounding oceanic regions; in the context of previous results it may suggest a thick viscous root beneath OJP. If such a root exists, then the discontinuity at 80 km bears some similarity to the mid-lithospheric discontinuities (MLDs) observed beneath continents. One possibility is that plume melting events, similar to that which formed OJP, may cause discontinuities in the MLD depth range. Plume–plate interaction could be a mechanism for MLD formation in some continents in the Archean prior to the onset of subduction.