The Mantle Dynamics, the Crustal Formation, and the Hydrothermal Activity of the Southern Mariana Trough Back-Arc Basin

Abstract

The Southern Mariana Trough back-arc basin is a currently active back arc basin, and it has fast spreading morphologic and geophysical characteristics, suggesting an additional magma supply, even though the full spreading rate is categorized as slow spreading. Five hydrothermal vent sites have been found within 5 km around the spreading axis at 13 N. The Japanese TAIGA Project selected this area as one of three integrated target sites, and TAIGA Project members conducted series of JAMSTEC research cruises for different types of geophysical surveys, together with dive observation and samplings by the submersible Shinkai 6500. We reviewed the results from these geophysical surveys and the volcanic rock samples to summarize the products from the TAIGA Project. The results provide strong constraints on the mantle dynamics and the crustal formation at the Southern Mariana Trough back-arc basin; all the results support that they are influenced by hydration derived from the subducting slab with accompanying the additional magma supply. Furthermore, the results from the geophysical and geological surveys for the five hydrothermal vent sites provide characteristic features on the hydrothermal activity and the features are different between on-axis and off-axis hydrothermal sites. The on-axis hydrothermal site is associated with an episodic diking event followed by fissures in a fourth order ridge segment, and its duration and size vary depending on the episodic diking event and on the fissures following. In contrast, the formation of the off-axis hydrothermal sites is closely related to the residual heat from the volcanism rather than tectonic stresses accompanied by faults, and the off-axis hydrothermal activity is for a long period and in a large scale. We summarized all the evidence to propose our scenario of the mantle dynamics, the crustal formation, and the hydrothermal activity of the Southern Mariana Trough back-arc basin.

High‐resolution magnetic signature of active hydrothermal systems in the back‐arc spreading region of the southern Mariana Trough

“…Contour interval is 40 m. Bathymetry is made using 0.025 nmi interval grid data from Seama et al . [].…”

Comparative Analysis of Microbial Communities in Iron-Dominated Flocculent Mats in Deep-Sea Hydrothermal Environments

“…1a and d). This field was found in the year 2010 during the YK10-10 cruise by the DSV Shinkai6500 (52,79,80). Orange chimneys approximately 10-m high were observed throughout the site (Fig.…”

Chemical composition of hydrothermal fluids in the central and southern Mariana Trough backarc basin

“…A unique appearance and strong arc geochemical signal was observed in the form of emanation of liquid CO 2 droplets (e.g., Lupton et al, 2006Lupton et al, , 2008. The southernmost part of the Mariana Trough near 13°N was a target field of the Archean Park and TAIGA projects (Kakegawa et al, 2008;Kato et al, 2012;Seama et al, 2015). High temperature fluid venting was discovered at four sites on and off the backarc spreading axis, and their fluid chemistry has been reported by Toki et al (2015).…”

“…The southernmost part (from 12.5°N to 13.1°N, termed Malaguana-Gadao Ridge) is characterized by inflated morphology and resembles a fast spreading ridge, where the axial depth is about 3000 m (Martínez et al, 2000). This morphology is attributed to enhanced magmatic flux reflecting the combined effects of crust extension and subduction-related hydrous flux (Stern et al, 2013;Seama et al, 2015).…”