Effects of axially variable diking rates on faulting at slow spreading mid-ocean ridges

What is it about?

Magma injection in the form of dikes accommodates a portion of the separation of tectonic plates at mid-ocean ridges. The rest of plate motions are taken up by faults forming within the plates. The relative importance of the two, diking and faulting, can explain a lot of important characteristics of mid-ocean ridges. Observations have shown that the rate of diking can be highly variable along the axis of slow-spreading ridges but how this variability is related to changes in the faulting pattern along the axis was not fully understood. Using fully three-dimensional numerical models, we have shown for the first time that two highly contrasting styles of faulting can occur next to each other within a short (15-20 km long) ridge segment when the diking rates change significantly enough.

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Why is it important?

Our models show that the interaction between the regions of more and less frequent dike injections tends to homogenize faulting styles along a ridge segment, inhibiting the domination of a particular faulting mode associated with an extreme local diking rate. This homogenizing effect explains why some faulting styles are observed even under the conditions previously thought to be unfavorable. However, when the variations in diking rates are large enough, two contrasting faulting styles can coexist within one ridge segment, as often observed along the slow-spreading ridges.