AUTHORS: Richard Sibson
NE Honshu, Japan, is a magmatic arc under arc-normal compression. The volcanic front together with the flanking forearc and backarc regions are currently undergoing compressional inversion following Early- to Mid-Miocene extensional rifting associated with the opening of the Japan Sea. Reverse fault rupture occurs predominantly on steep faults inherited from the former extensional phase. The crustal seismogenic zone is 10-20 km deep with geophysical indicators suggesting that the lower seismogenic zone and mid-crust are overpressured to near-lithostatic values by hydrothermal fluids derived from ongoing magmatism, crustal thickening, and slab dewatering. This overpressured arc provides an analog to ancient mesozonal (orogenic lode gold) mineralising environments with implications for exploration.
KEYWORDS: magmatic arc, reverse faulting, compressional inversion, fluid overpressure, mesozonal mineralisation
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