Episodicity of structural flow in an active subduction system, new insights from mud volcano's carbonate veins – Scientific Ocean drilling expedition IODP 366

Abstract

This study's goal is to understand the structural events and episodes of fluid flow recorded in calcium carbonate precipitation sampled in Mariana forearc serpentine mud volcanoes. Those active mounts provide a unique window to deep structural and fluid flow events affecting the subduction channel mélange zone and the subducted Pacific Plate.To build a conceptual model of vein precipitations from the subduction zone to the mud volcanoes edifice, we unravelled the origin, timing, and mechanisms of those precipitations with a multidisciplinary study of calcium carbonate veins, from samples drilled in the flank of Fantangisña Seamount during the International Ocean Discovery Program (IODP) Expedition 366.Structural analysis of the carbonate vein network revealed stages of precipitation and dissolution. The most ancient calcium carbonate minerals underwent high tectonic stress and several degrees of silicification. U-Pb dates ranged from Early Cretaceous to present day, recording potential pre-convergence events and calibrating an episodic building of the Mariana mud volcanoes from the start of the convergence to present day. The UCC-normalized LREE pattern, 87 Sr/ 86 Sr ratios ranging from 0.704977 to 0.705798 and δ 18 O signature 18.7 to 19.8 (‰, V-SMOW) of the veins indicate a mixed origin of the precipitated fluids influenced by the serpentine mud signature.Those mud volcanoes were episodically built from the start of the subduction to present day in function of the forearc tectonic activity. They are complex systems internally composed of a fault network providing multiple circulation pathways that can be successively opened or closed.

High-pressure synthesis and storage of solid organic compounds in active subduction zones

“…Despite the fact that abundant carbonate minerals may be sampled in the shallow Mariana forearc, as late calcite and aragonite veins, chimneys (49)(50)(51), or stored within blue-serpentinite (this study), their carbon isotope composition suggest that they formed nearby the surface through microbially mediated fluid interaction between shallow seawater and deep-sourced fluids. It is therefore not clear how much of this carbon is derived from the subduction process and how much is derived from late seawater circulation.…”

“…The microbial oxidation of organic carbon compounds in blue-serpentinites is also supported by the predominance of authigenic aragonite and calcite in the top meters of the mud volcanoes ( 49 – 51 ). On the basis of Sr and C isotope analyses, their precipitation was interpreted as resulting from microbially mediated fluid interactions between shallow seawater and deep-sourced and slab-related fluids.…”

Fluid‐Mantle Interaction Along the Mariana Convergent Margin

“…Several studies confirmed the episodicity of serpentinite mudflows formation from a central conduit due to the presence of multiple mudflow units on the flanks of the seamounts (Frery et al., 2021; Fryer, 1992; Fryer et al., 1990; Oakley et al., 2007; Wheat et al., 2008). The presence of clay layers within the serpentinite mud flow deposits may represent quiet phases between serpentinite mud eruptions (Fryer, 1996).…”

A Review of the Migration of Hydrogen from the Planetary to Basin Scale

“…Studies at both reservoir and basin scales have demonstrated that fault transmissivity is primarily influenced by (i) the fault's type, geometry, and displacement; (ii) the internal architecture of the fault zone; (iii) the surrounding stratigraphy and lithology; and (iv) the geomechanical stress (Faulkner et al, 2010;Solum et al, 2010;Massiot et al, 2019). Due to the variability of these parameters, fault transmissivity evolves both temporally and spatially (Frery et al, 2015;Frery, Fryer, et al, 2021). The opening of faults can be triggered by seismic events, fluid overpressures, or localised dissolution (Gratier & Gueydan, 2007), while their closure can be attributed to progressive sealing resulting from mechanical (Hancock et al, 1999;Eichhubl & Boles, 2000), chemical processes and fault roughness (Renard et al, 2013).…”