An intermittent detachment faulting system with a large sulfide deposit revealed by multi-scale magnetic surveys

Abstract

Magmatic and tectonic processes can contribute to discontinuous crustal accretion and play an important role in hydrothermal circulation at ultraslow-spreading ridges, however, it is difficult to accurately describe the processes without an age framework to constrain crustal evolution. Here we report on a multi-scale magnetic survey that provides constraints on the fine-scale evolution of a detachment faulting system that hosts hydrothermal activity at 49.7°E on the Southwest Indian Ridge. Reconstruction of the multi-stage detachment faulting history shows a previous episode of detachment faulting took place 0.76~1.48 My BP, while the present fault has been active for the past ~0.33 My and is just in the prime of life. This fault sustains hydrothermal circulation that has the potential for developing a large sulfide deposit. High resolution multiscale magnetics allows us to constrain the relative balance between periods of detachment faulting and magmatism to better describe accretionary processes on an ultraslow spreading ridge.

Variability of Sea‐Surface Magnetic Anomalies at Ultraslow Spreading Centers: Consequence of Detachment Faulting and Contrasted Magmatism?

“…The area between Indomed and Gallieni FZs displays the most magmatic segments of the SWIR, with the lowest mantle Bouguer gravity anomaly and Na 8.0 content in basalt samples, the highest amplitude of the central magnetic anomaly, and the thickest crust (Sauter & Cannat, 2010; Sauter et al., 2001). In this area, we select two sea‐surface magnetic anomaly profiles, one (Figure 3c) across the Longqi OCC (Wu et al., 2021), and the other (Figure 3d) in the middle of magmatic spreading segment 27 (Chen et al., 2021). We construct the crustal accretion model for the western less magmatic area (Figure 3c).…”

Sensitivity of mid-ocean ridge hydrothermal system controlled by the detachment fault to the glacial cycle

“…Therefore, we propose a new mechanism to explain the sea level changes related to the glacial cycle, which regulates the melt supply of the mantle beneath the new volcanic ridge and then regulates the hydrothermal circulation above the detachment fault. The correlation between hydrothermal activity and tectonic activity related to detachment faults has been found at several oceanic ridges 14,15,23,28 . The activity of the detachment fault increases the permeability of the rock and controls the heat injection under the fault, and the repeated movement on the fault activates and controls the hydrothermal circulation on which it occurs 14,15 .…”

“…The correlation between hydrothermal activity and tectonic activity related to detachment faults has been found at several oceanic ridges 14,15,23,28 . The activity of the detachment fault increases the permeability of the rock and controls the heat injection under the fault, and the repeated movement on the fault activates and controls the hydrothermal circulation on which it occurs 14,15 . Additionally, it has been found that the hydrothermal venting of the large hydrothermal circulation systems on slow-ultraslow spreading ridges may be episodic 7,32,33 .…”

“…Deep faults can readily extract heat from deeper heat sources. Moreover, the repeated movement of faults activates the permeable uid channels of the overlying oceanic crust, thus driving the long-life hydrothermal cycle [13][14][15] . The mechanism of heat mining of a fault-controlled hydrothermal system is very different from the magma-dominated companion commonly seen in the intermediate-fast spreading ridge (such as EPR and JDFR).…”

Variability of Sea-surface Magnetic Anomalies at Ultraslow Spreading Centers: Consequence of Detachment Faulting and Contrasted Magmatism?

“…The area between Indomed and Gallieni FZs displays the most magmatic segments of the SWIR, with the lowest mantle Bouguer gravity anomaly and Na 8.0 content in basalt samples, the highest amplitude of the central magnetic anomaly, and the thickest crust (Sauter & Cannat, 2010;Sauter et al, 2001). In this area, we select two sea-surface magnetic anomaly profiles, one (Figure 3c) across the Longqi OCC (Wu et al, 2021), and the other (Figure 3d) in the middle of magmatic spreading segment 27 (Chen et al, 2021). We construct the crustal accretion model for the western less magmatic area (Figure 3c).…”