Kimberlite deposits attract much interest as the host rock for diamonds, but their eruption mechanisms and deep root structure remain poorly perceived. Independent geochronological and seismic shear-wave anisotropy studies in NW Canada near the world's newest diamond mines revealed an unexpected correlation in structural trends. Age of eruption grouped 36 kimberlites into linear clusters; forward modelling of shear-wave delays indicated two distinct layers of seismic anisotropy with a boundary about 120 km deep. The similarity of inferred age and trend direction at surface and at depth indicates that these kimberlites erupted along lithospheric-scale fractures oriented by continental stress fields related to North American plate motions.

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