Finite strain analysis and thermal modeling of magmatically folded leucocratic dikes in the Mount Stuart Batholith, Washington and the Tuolumne Intrusive Suite, California, yield strain rates in the range of 10−2 to 10−13 s−1. Compared to published regional strain rates (10−13 to 10−15 s−1), wall-rock strain rates associated with dike-fed expansion (10−7 s−1), and rates resulting from numerical modeling of crystal-plastic creep in aureoles (10−11 s−1), our fast rates are several orders of magnitude higher.

Field and microstructural observations suggest that multiple material transfer processes, including rigid rotation, ductile flow, cracking, and potentially melt-assisted granular flow operated in the aureoles to accommodate emplacement of these two plutons. Calculated durations of pluton construction and bulk shortening in the aureoles indicate that aureole deformation requires only slow, long-term strain rates of 10−14 s−1. Thus our local fast strain rates indicate that aureoles may be characterized by pulsating high strain rate surges. We suggest that magmatically folded dikes in these and other pluton aureoles around the world may be used as evidence for fast host rock strain rates during pluton emplacement.

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