DOI: 10.1016/j.epsl.2020.116706
论文题名: Rheological control on the segmentation of the mid-ocean ridges: Laboratory experiments with extension initially perpendicular to the axis
作者: Sibrant A.L.R. ; Davaille A. ; Mittelstaedt E.
刊名: Earth and Planetary Science Letters
ISSN: 0012821X
出版年: 2021
卷: 557 语种: 英语
中文关键词: axial mechanical strength
; laboratory experiments
; mid-ocean ridge
; segmentation
; transform faults
英文关键词: Diffusion in liquids
; Fracture mechanics
; Morphology
; Silica
; Sols
; Submarine geology
; Transform faults
; Colloidal silica dispersions
; Elastic thickness
; Failure parameters
; Laboratory experiments
; Lithospheric thickness
; Mantle temperatures
; Surface water layer
; Thermal structure
; Surface waters
; brittle deformation
; crack propagation
; experimental study
; laboratory method
; mechanical property
; rheology
; transform fault
英文摘要: Mid-ocean ridges (MOR) axes are not straight, but segmented over scales of 10s to 100s of kilometers by several types of offsets including transform faults (TF), overlapping spreading centers (OSC) and non-transform, non-overlapping offsets (NTNOO). Variations in axial morphology and segmentation have been attributed to changes in magma supply, axial thermal structure (which depends on mantle temperature and spreading rate), and axial mechanical properties. To isolate the effect of each of these processes is difficult with field data alone. We therefore present a series of analogue experiments using colloidal silica dispersions as an Earth analogue. Diffusion of salt from saline solutions placed in contact with these fluids, causes formation of a skin, whose rheology evolves from viscous to elastic and brittle with increasing salinity. Applying a fixed spreading rate to this pre-formed, brittle plate results in cracks, faults, and ridge segments. Lithospheric thickness is varied independently by changing the surface water layer salinity. Experimental results depend on the axial failure parameter ΠF, the ratio of a mechanical length scale (Zm) and the axial elastic thickness (Zaxis), which depends on mantle temperature and spreading velocity. Slow-spreading fault-dominated, and fast-spreading fluid intrusion-dominated, ridges on Earth and in the laboratory are separated by the same critical value ΠFc±0.024, suggesting that the axial failure mode governs ridge geometry. Here, we examine ridge axis segmentation. Measurements of >4000 experimental ridge segments and offsets yield an average segment length Lm that is quasi-constant at all spreading velocities. Scaled to the Earth, Lm∼55 km, in agreement with the natural data. Experiments with low ΠF show offset size varying as dl=csteLmZaxis regardless of offset type, a correlation well explained by fracture mechanics. Finally, as on Earth, experimental ridge segments are separated by transform and non-transform discontinuities, and their nature and occurrence vary with ΠF. NTNOOs develop when ΠF<ΠFc, while OSCs develop when ΠF>ΠFc. In contrast, TF may form at any ΠF, but the proportion of TFs relative to OSCs or NTNOOs decreases when ΠF/ΠFc>> 1 or << 1, in agreement with natural MOR. © 2020 Elsevier B.V. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/165673
Appears in Collections: 气候变化与战略
There are no files associated with this item.
作者单位: Laboratoire FAST (CNRS / Univ. Paris-Sud), Bat. 530-Pascal, Campus Universitaire, Rue Andre Riviere, ORSAY cedex, 91 405, France; Department of Geological Sciences, University of Idaho, Moscow, ID, United States; Univ. Brest, CNRS, IUEM, UMR6538, Geosciences Ocean, Plouzane, F-29290, France
Recommended Citation:
Sibrant A.L.R.,Davaille A.,Mittelstaedt E.. Rheological control on the segmentation of the mid-ocean ridges: Laboratory experiments with extension initially perpendicular to the axis[J]. Earth and Planetary Science Letters,2021-01-01,557