Lithospheric Structure Controls Sequentially Active Detachment Faulting at the Longqi Segment on the Southwest Indian Ridge

Oceanic detachment faulting, a major mode of seafloor accretion at slow and ultraslow spreading ridges, is thought to occur during magma‐poor phases and be abandoned when magmatism increases. In this framework, detachment faulting is the result of temporal variations in magma flux, which is inconsis...

Full description

Saved in:
Bibliographic Details
Published in:Journal of geophysical research. Solid earth 2023-11, Vol.128 (11), p.n/a
Main Authors: Chen, Ming, Tao, Chunhui, Rüpke, Lars H., Liu, Yunlong, Wang, Hanchuang, Liu, Sibiao
Format: Article
Language:English
Subjects:
Accretion
Active control
Continuous flow
Deposition
detachment fault
Evolution
Fault lines
Faults
Fluctuations
Geodynamics
Geological faults
Geophysics
Lava
Life cycle
Life cycles
Lithosphere
lithospheric structure
Magma
Modelling
numerical models
Ocean floor
Ocean models
Ridges
Segments
Spreading
Spreading centres
Structure-function relationships
Tectonophysics
Temporal variations
Two dimensional models
ultraslow spreading ridges
Upper mantle
Volcanic vents
Citations: Items that this one cites
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:Oceanic detachment faulting, a major mode of seafloor accretion at slow and ultraslow spreading ridges, is thought to occur during magma‐poor phases and be abandoned when magmatism increases. In this framework, detachment faulting is the result of temporal variations in magma flux, which is inconsistent with recent geophysical observations at the Longqi segment on the Southwest Indian Ridge (49°42′E). In this paper, we focus on this sequentially active detachment faulting system that includes an old, inactive detachment fault and a younger, active detachment fault. We investigate the mechanisms controlling the temporal evolution of this tectonomagmatic system by using 2D mid‐ocean ridge spreading models that simulate faulting and magma intrusion into a visco‐elasto‐plastic continuum. Our models show that temporal variations in magma flux alone are insufficient to match the inferred temporal evolution of the sequentially active detachment system. Rather we find that sequentially active detachment faulting spontaneously occurs at the Longqi segment as a function of lithospheric thickness. This finding is in agreement with an analytical model, which shows that a thicker axial lithosphere results in a smaller fault heave and that a flatter angle in lithosphere thickening away from the accretion axis stabilizes the active fault. A thicker axial lithosphere and its flatter off‐axis angle combined have the potential to modulate sequentially active detachment faulting at the Longqi segment. Our results thus suggest that temporal changes of magmatism are not necessary for the development and abandonment of detachment faults at ultraslow spreading ridges. Plain Language Summary The oceanic lithosphere is frequently generated through slip on long‐lived faults called oceanic detachment faults, which exhume lower crustal and upper mantle materials on the seabed and form dome‐shaped features. Yet, oceanic detachment faulting is a sequentially active process and previous studies have focused on temporal variations in magma flux as the primary cause. Magma flux refers to the rate at which the continuous flow of magma moves from melted mantle at depth toward the ridge axis through volcanic vents or fissures. In the presented manuscript we show that this standard model does not work for the ultraslow spreading Southwest Indian Ridge (49°42′E). Here, we present geological and geophysical evidence that the magma flux had remained stable during the two most recent phases of de
ISSN:2169-9313
2169-9356
DOI:10.1029/2023JB026467