Tectonic implications of carbonate deposits on the eastern slope of the Hahajima Seamount in the collision zone between the Izu?Bonin Arc on the Philippine Sea Plate and the Ogasawara Plateau on the Pacific Plate
Tectonic implications of carbonate deposits on the eastern slope of the Hahajima Seamount in the collision zone between the Izu?Bonin Arc on the Philippine Sea Plate and the Ogasawara Plateau on the Pacific Plate
复制标题
菲律宾海板块伊豆博宁岛弧与太平洋板块小笠原高原碰撞带母岛海山东坡碳酸盐岩沉积的构造意义
DOI：
10.1111/iar.12368
复制
发表时间：
2020
期刊：
影响因子：
1.5
通讯作者：
Iryu Yasufumi
中科院分区：
文献类型：
--
作者：
Miyata Jun;Takayanagi Hideko;Ishigaki Akimasa;Hirano Naoto;Shiokawa Satoshi;Nishimura Akira;Nakazawa Tsutomu;Ishikawa Tsuyoshi;Nagaishi Kazuya;Tokuyama Hidekazu;Ishiwatari Akira;Iryu Yasufumi
Hahajima海山位于西北太平洋Izu-Bonin和Mariana弧前斜坡的交界处，太平洋板块上的菲律宾海板块和小川高原之间。尽管之前有许多研究，但Hahajima海山的起源仍然存在争议。在这里，我们根据从海山东坡收集的浅水碳酸盐的沉积学和年代学分析来限制其来源。碳酸盐岩以浮石为主，含有大量软体动物。砾石大小的生物碎屑包括软体动物(如神经纲动物和硬壳动物)、当地的钙质刺和少量的珊瑚。砂粒大小的成分包括底栖有孔虫和环虫藻类的生物碎屑，以及碎屑壳内和球体的非骨骼颗粒，没有卵圆形。大多数生物碎屑被生物侵蚀，并被微晶包膜覆盖。样品的锶同位素年龄可分为两个范围：贝里亚期或阿普提期(分别为140.3 Ma或118.3~113.2 Ma)和柯尼亚期至坎帕尼亚期(86.5M a~77.2M a)。Hahajima海山上的浅水碳酸盐岩在岩性和锶同位素年龄上与位于伊豆-博宁海沟对面(即太平洋板块)东部的小川高原上的浅水碳酸盐岩相似。这表明，Hahajima海山东坡的浅水碳酸盐不是原地沉积，而是起源于小川高原。因此，这座海山的东段可以被解释为一个吸积楔。
The Hahajima Seamount is located at the junction between the Izu–Bonin and Mariana forearc slopes in the northwest Pacific Ocean, and between the Philippine Sea Plate and the Ogasawara Plateau on the Pacific Plate. Despite numerous previous studies, the origin of the Hahajima Seamount remains controversial. Here we constrain its origin based on sedimentological and chronological analyses of shallow‐water carbonates collected from the eastern slope of the seamount. The carbonates are dominated by floatstones with numerous mollusks. Gravel‐sized bioclasts include mollusks (e.g. nerineids and rudists) and local calcareous spines and minor amounts of corals. Sand‐sized components include bioclasts of benthic foraminifers and dasycladalean algae, and non‐skeletal grains of intraclasts and peloids, with no ooids. Most of the bioclasts are bioeroded and coated with micrite envelopes. The Sr isotope ages of the samples fell into two ranges: Berriasian or Aptian (140.3 Ma or 118.3–113.2 Ma, respectively) and Coniacian to Campanian (86.5–77.2 Ma). Shallow‐water carbonates on the Hahajima Seamount are similar in lithology and Sr isotope ages to those on the Ogasawara Plateau located to the east, on the opposite side of the Izu–Bonin Trench (i.e. on the Pacific Plate). This indicates that the shallow‐water carbonates on the eastern slope of the Hahajima Seamount were not deposited in situ, but instead originated from the Ogasawara Plateau. The eastern section of this seamount can thus be interpreted as an accretionary wedge.