Geochemical characteristics of back-arc basin lower crust and upper mantle at final spreading stage of Shikoku Basin: an example of Mado Megamullion

Progress in Earth and Planetary Science

Kyoko Okino¹  Norikatsu Akizawa¹  Hisashi Asanuma¹  Katsuyoshi Michibayashi²  Jonathan E. Snow³  Atlanta Sen⁴  Ken-ichi Hirauchi⁵  Alessio Sanfilippo⁶  Valentin Basch⁶  Takafumi Hirata⁷  Yasuhiko Ohara⁸  Hiroyuki Yamashita⁹  Masakazu Fujii^1,10  Shiki Machida^1,11  Osamu Ishizuka^1,12  Yumiko Harigane^1,12 

[1] Atmosphere and Ocean Research Institute, The University of Tokyo, 5-1-5 Kashiwanoha, 277-8564, Kashiwa, Chiba, Japan;Department of Earth and Planetary Sciences, Nagoya University, 464-8601, Furocho, Chikusa, Nagoya, Japan;Department of Geology and Geophysics, Louisiana State University, 70803, Baton Rouge, LA, USA;Department of Geology and Geophysics, Louisiana State University, 70803, Baton Rouge, LA, USA;Department of Earth and Atmospheric Sciences, University of Houston, 77204, Houston, TX, USA;Department of Geosciences, Shizuoka University, 836 Ohya, 422-8529, Suruga, Shizuoka, Japan;Dipartimento di Scienze della Terra e dell’ambiente, University of Pavia, 1 Via Ferrata, Pavia, Italy;Geochemical Research Center, The University of Tokyo, 7-3-1 Hongo, 113-0033, Bunkyo, Tokyo, Japan;Hydrographic and Oceanographic Department of Japan, 3-1-1 Kasumigaseki, 100-8932, Chiyoda, Tokyo, Japan;Japan Agency for Marine-Earth Science and Technology, 2-15 Natsushima, 237-0061, Yokosuka, Kanagawa, Japan;Department of Earth and Planetary Sciences, Nagoya University, 464-8601, Furocho, Chikusa, Nagoya, Japan;Kanagawa Prefectural Museum of Natural History, 499 Iryuda, 250-0031, Odawara, Kanagawa, Japan;National Institute of Polar Research/SOKENDAI, 190-8518, Tachikawa, Tokyo, Japan;Ocean Resources Research Center for Next Generation, Chiba Institute of Technology, 2-17-1 Tsudanuma, 275-0016, Narashino, Chiba, Japan;Research Institute of Earthquake and Volcano Geology, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, 305-8567, Tsukuba, Ibaraki, Japan;

关键词: Gabbro;    Peridotite;    Oceanic core complex;    Magmatic water;    In-situ Pb isotope;    And Slab rollback;   

DOI  :  10.1186/s40645-021-00454-3

来源: Springer

【 摘 要 】

This paper explores the evolutional process of back-arc basin (BAB) magma system at final spreading stage of extinct BAB, Shikoku Basin (Philippine Sea) and assesses its tectonic evolution using a newly discovered oceanic core complex, the Mado Megamullion. Bulk and in-situ chemical compositions together with in-situ Pb isotope composition of dolerite, oxide gabbro, gabbro, olivine gabbro, dunite, and peridotite are presented. Compositional ranges and trends of the igneous and peridotitic rocks from the Mado Megamullion are similar to those from the slow- to ultraslow-spreading mid-ocean ridges (MOR). Since the timing of the Mado Megamullion exhumation corresponds to the very end of the Shikoku Basin opening, the magma supply was subdued and highly episodic, leading to extreme magma differentiation to form ferrobasaltic, hydrous magmas. In-situ Pb isotope composition of magmatic brown amphibole in the oxide gabbro is identical to that of depleted source mantle for mid-ocean ridge basalt (MORB). In the context of hydrous BAB magma genesis, the magmatic water was derived solely from the MORB source mantle. The distance from the back-arc spreading center to the arc front increased away through maturing of the Shikoku Basin to cause MORB-like magmatism. After the exhumation of Mado Megamullion along detachment faults, dolerite dikes intruded as a post-spreading magmatism. The final magmatism along with post-spreading Kinan Seamount Chain volcanism were introduced around the extinct back-arc spreading center after the opening of Shikoku Basin by residual mantle upwelling.

【 授权许可】

CC BY