Pervasive granitoid magma transfer through the lower–middle crust during non‐coaxial compressional deformation

摘要: Granitic magmas migrated through Early Proterozoic middle–lower crust at Mt Hay, central Australia, via a diverse network of narrow structurally controlled channelways, during period progressive W–SW-directed thrusting (D1a–D1d). They utilized existing folds, boudins and shear zones, or created new channels by magmatic fracture either parallel to layering or, rarely, in irregular arrays. The rose obliquely, the plunging (50–60°) regional elongation direction, which was defined coaxial boudin necks strong mineral-elongation lineation. Megacrystic charnockitic metre-scale conduits D1a–D1b, but leucosomes were generally restricted smaller (centimetre-scale) structures that existed throughout entire deformation history. Thus, D1a/D1b potential feeders situ partial melts adjacent larger charnockite magma, thereby providing pervasive interconnected allowed efficient migration all magma types early stages thrusting. The upper–middle Anmatjira–Reynolds Range area contains abundant megacrystic granitoid sheets are similar age geochemistry those Hay. considered have formed as syntectonic intrusions emplaced thrusting, suggesting granitic near base continental passed mid-lower crustal level (25–30 km) exposed Hay accumulated, batholithic proportions, shallower levels (12–20 km) such area. The observations imply deep capable major compressive, noncoaxial deformation. Localization sequentially developed, narrow, compressive suggests dilatancy followed successive foliation-forming events, situation can occur steady-state if effective confining pressures low, would be result high possibly variable rates influx. inferred rapid melt segregation suggest large chambers do not form until reaches neutral buoyancy middle upper crust.