Tamu Massif is an immense Mesozoic submarine volcano, the main edifice of the Shatsky Rise oceanic plateau. It is located at a spreading ridge triple junction, but considered to be a shield volcano formed by effusive volcanism from an emerging mantle plume. However, it is unclear how Tamu Massif eruptions interacted with the spreading ridges, which are enormous linear volcanoes themselves. Here we create a magnetic anomaly map for Tamu Massif, which can provide clues about crustal formation. For Tamu Massif, we find dominantly linear magnetic field anomalies caused by crustal blocks of opposite magnetic polarity. This pattern suggests that Tamu Massif is not a shield volcano, but was emplaced by voluminous, focused ridge volcanism. If the magma source at the Shatsky Rise was a plume, it was closely connected to and controlled by seafloor spreading. By implication, even the largest oceanic plateau edifices can be formed by seafloor spreading. We suggest that the widely accepted analogy between continental flood basalts and oceanic plateaus requires reconsideration.

塔木山峰是巨大的中生代海底火山，是沙茨基上升海洋高原的主要建筑物。它位于扩张脊三重交界处，但被认为是由新兴地幔羽喷出的火山作用形成的盾构火山。但是，目前尚不清楚塔木山地块喷发是如何与扩张的山脊相互作用的，而扩张的山脊本身就是巨大的线性火山。在这里，我们为Tamu Massif创建了一个磁异常图，它可以提供有关地壳形成的线索。对于Tamu Massif，我们发现主要是由相反极性的地壳引起的线性磁场异常。这种模式表明，塔木山地块不是盾构火山，而是被大量集中的山脊火山所包围。如果说Shatsky Rise的岩浆源是一股羽状流，它就与海底扩散密切相关并受其控制。言外之意，即使最大的海洋高原大厦也可以通过海底扩张形成。我们建议，大陆洪水玄武岩与海洋高原之间的广泛接受的类比需要重新考虑。