Magnetic anomaly map of Ori Massif and its implications for oceanic plateau formation
Magnetic anomaly map of Ori Massif and its implications for oceanic plateau formation
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DOI：
10.1016/j.epsl.2018.08.029
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发表时间：
2018-11
影响因子：
5.3
通讯作者：
Yanming Huang;W. Sager;M. Tominaga;J. Greene;Jinchang Zhang;M. Nakanishi
中科院分区：
文献类型：
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作者：
Yanming Huang;W. Sager;M. Tominaga;J. Greene;Jinchang Zhang;M. Nakanishi
许多海洋高原位于洋中脊处或附近。为了解释与正常洋壳相比的高原体积和增厚的地壳，通常假设热点-山脊相互作用，但相互作用的方式仍不清楚。沙茨基隆起海洋高原是一座大型火山，形成于侏罗纪晚期和白垩纪早期的三重交界处。最近的钻探和地震调查表明，奥里地块的中间建筑是一座中央火山。矛盾的是，在奥里地块的部分地区追踪到了磁线，这意味着形成于扩张的山脊处。在这项研究中，我们检查了奥里地块及其周围的磁异常，以获得有关这座火山大厦形成的见解。对 21 次航行的磁数据进行了校正、组合和网格化，以构建磁异常图。通过正向和逆向磁力模拟来研究奥里地块的磁力结构。结果表明，这个大型火山大厦的主要特征是由交替的正常和反极性磁化块产生的线性磁异常，类似于扩展脊记录的磁异常。对于由长距离熔岩流形成的中央火山来说，这种磁性结构是预计不会出现的，这意味着奥里地块的喷发一定被限制在山脊轴附近。奥里地块南北边界上的磁湾表明它被三重交点包围，表明沙茨基隆起形成期间存在复杂的山脊构造。奥里地块被相干线性磁异常穿过这一令人惊讶的发现表明，尽管地壳厚度很大，海洋高原仍可以记录海底传播的磁异常。其他海洋高原也记录了线性磁异常，这意味着不同的板块边界与海洋高原火山活动之间存在联系。
Many oceanic plateaus have been emplaced at or adjacent to mid-ocean ridges. To explain plateau volume and thickened crust compared to normal oceanic crust, hotspot–ridge interaction is commonly assumed, but the manner of interaction remains unclear. The Shatsky Rise oceanic plateau is a large volcanic mountain that formed at a triple junction during Late Jurassic and Early Cretaceous time. Recent drilling and seismic investigations suggest that the intermediate edifice in the rise, Ori Massif, is a central volcano. Paradoxically, magnetic lineations were traced across parts of Ori Massif, implying formation at a spreading ridge. In this study, we examined magnetic anomalies over and around Ori Massif to obtain insights about the formation of this volcanic edifice. Magnetic data from 21 cruises were corrected, combined, and gridded to construct a magnetic anomaly map. Forward and inverse magnetic modeling was done to investigate the magnetic structure of Ori Massif. The results imply that this large volcanic edifice is predominantly characterized by linear magnetic anomalies resulting from alternating normal and reversed polarity magnetization blocks, analogous to magnetic anomalies recorded by spreading-ridges. This magnetic structure is not expected for a central volcano that was built by long runout lava flows, implying that Ori Massif eruptions must have been constrained near the ridge axis. Magnetic bights on the north and south boundaries of Ori Massif imply that it was bracketed by triple junctions, indicating complex ridge tectonics during the formation of Shatsky Rise. The surprising finding that Ori Massif is traversed by coherent linear magnetic anomalies indicates that oceanic plateaus can record seafloor spreading magnetic anomalies despite large crustal thickness. Other oceanic plateaus also record linear magnetic anomalies, implying a link between divergent plate boundaries and oceanic plateau volcanism.