Magnetic Anomaly Map of Shatsky Rise and Its Implications for Oceanic Plateau Formation
Magnetic Anomaly Map of Shatsky Rise and Its Implications for Oceanic Plateau Formation
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DOI：
10.1029/2019jb019116
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发表时间：
2020-12
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影响因子：
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通讯作者：
Yanming Huang;W. Sager;Jinchang Zhang;M. Tominaga;J. Greene;M. Nakanishi
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作者：
Yanming Huang;W. Sager;Jinchang Zhang;M. Tominaga;J. Greene;M. Nakanishi
沙茨基隆起大洋高原是在地磁极性反转频繁的时期侵位的，因此可以利用磁异常重建其构造演化。以往的研究主要集中在识别磁性等时线上，在追踪高起伏上的磁性线理方面遇到了困难。我们编制了沙茨基隆起及其周围地区的一个大型磁学数据集，使用了跨越54年的96次地球物理巡航的5.5×106个数据点。组件数据集的长时间跨度和异构性使得数据合并成为一项挑战。在处理过程中去除了内场和外场的贡献以及虚假读数。开发了一种“主干”方法，以最近的全球定位系统导航数据为基础，以改进数据集的一致性。新的磁异常图的奇异特征是线性磁异常普遍存在。在几乎每一个数据密集到足以描绘异常趋势的地方，高原和周围地壳的特征都是线性异常。一些地区的不协调异常暗示了与三结点迁移和山脊重新定向有关的复杂构造。塔木地块显然是沿着太平洋-法拉隆扩张海脊的一段形成的，该海脊旋转了90°，形成了一个三重连接，穿过了该建筑物。Ori Massif似乎是在太平洋-Izanagi海脊三个交界处之间形成的。谢尔肖夫地块含有可能指示微板块的不协调线条。沙茨基隆起内普遍存在的线性磁异常表明，这些火山建筑物一定是由类似大洋中脊的扩张形成的，形成了异常厚的地壳。
Shatsky Rise oceanic plateau was emplaced during a period of frequent geomagnetic polarity reversals, allowing reconstruction of its tectonic evolution using magnetic anomalies. Prior studies mainly focused on identifying magnetic isochrons and encountered difficulties in tracing magnetic lineations over high relief. We complied a large magnetic data set over Shatsky Rise and its environs, using 5.5 × 106 data points from 96 geophysical cruises spanning 54 years. The long‐time span and heterogeneity of component data sets made data merger a challenge. Contributions of internal and external fields, and spurious readings were removed during processing. A “backbone” method, using recent GPS‐navigated data as a foundation, was developed to improve the coherency of the data set. The singular characteristic of the new magnetic anomaly map is that linear magnetic anomalies are ubiquitous. In nearly every place where data are dense enough to delineate anomaly trends, the plateau and surrounding crust are characterized by linear anomalies. Discordant anomalies in some areas imply complex tectonics related to triple junction migration and ridge reorientation. Tamu Massif apparently formed along a segment of Pacific‐Farallon spreading ridge that rotated by 90° as a triple junction migrated through the edifice. Ori Massif appears to have formed on the Pacific‐Izanagi ridge between triple junctions. Shirshov Massif contains discordant lineations that may indicate a microplate. The pervasive occurrence of linear magnetic anomalies within Shatsky Rise implies that these volcanic edifices must have formed by spreading analogous to mid‐ocean ridges that formed anomalously thick crust.