Seismic evidence links the subducted Mongol-Okhotsk slab to deformation in D″ near the northeastern margin of the Perm Anomaly
Seismic evidence links the subducted Mongol-Okhotsk slab to deformation in D″ near the northeastern margin of the Perm Anomaly
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DOI：
10.1016/j.tecto.2019.228297
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发表时间：
2020-01
期刊：
影响因子：
2.9
通讯作者：
Juntao Tao;Jinfeng Hu;Cong Jin;Xiaobo He
中科院分区：
文献类型：
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作者：
Juntao Tao;Jinfeng Hu;Cong Jin;Xiaobo He
数值模拟表明，大低剪切速度道（llsvp）与D″的俯冲板块之间存在动态相互作用，而板块又对大低剪切速度道的形状和位置产生重要影响。在这项研究中，我们通过分析发生在西北太平洋俯冲带的两个深层事件产生的下地幔三叠相，并在欧洲和土耳其的台站记录，在Perm异常（欧亚大陆下一个较小的LLSVP）东北边缘附近发现了D”不连续存在的证据。北部的D″结构面在核幔边界（CMB）上方300 km处速度增加+2%，而南部的D″结构面在CMB上方260 km处速度增加+3%。D″结构不连续最有可能归因于钙钛矿到后钙钛矿的相变，并伴有残余板块物质的存在（可能与俯冲的蒙古-鄂霍次克板块有关）。我们的观测-连同之前的地震各向异性探测-提供了将俯冲板块与LLSVP边缘附近发生的变形动态联系起来的线索。
Numerical simulations have indicated that the Large low-Shear Velocity Provinces (LLSVPs) dynamically interact with subducted slabs in D″, and slabs in turn play an important role in influencing the shape and location of the LLSVPs. In this study, we find evidence for the existence of the D” discontinuity near the northeastern margin of the Perm Anomaly — a smaller LLSVP beneath Eurasia, by analyzing theScd(the lower mantle triplication) phases generated from two deep events occurring in the northwestern Pacific subduction zone and recorded at stations in Europe and Turkey. The D″ discontinuity in the north is characterized with a +2% velocity increase occurring at a height of 300 km above the core-mantle boundary (CMB), whereas the discontinuity in the south is characterized with a +3% velocity increase occurring at a height of 260 km above the CMB. The D″ discontinuity is most likely attributed to a phase transition from perovskite to post-perovskite in conjunction with the presence of relic slab materials (likely related to the subducted Mongol-Okhotsk slab). Our observations– along with previous seismic anisotropic detections– provide a clue to dynamically link the subducted slab to deformation taking place near the edges of the LLSVP.