Formation and transfer of stoped blocks into magma chambers: The high-temperature interplay between focused porous flow, cracking, channel flow, host-rock anisotropy, and regional deformation

摘要: Magmatic stoping, i.e., the formation, transfer into, and movement through magma of older plutonic metamorphic host-rock xenoliths, was widespread in Mesozoic Sierra Nevada batholith (California, United States). However, prevailing view that stoped blocks form by rapid thermal shattering collapse into chambers may not be dominant process block formation displacement Nevada. In detailed studies around Tuolumne Batholith Jackass Lakes pluton, we found evidence for following history slightly older, fairly isotropic host rocks: (1) low stress sites developed, leading to planar zones increased porosity; (2) focused porous flow first felsic melts followed intermediate led growth fingers, which turn porosity loss cohesion; (3) connection magmatic fingers resulted dike-like channels facilitated removal all material these zones. Once formed, were initially displaced repeated injections along channels, often resulting unidirectional creating local sheeted complexes margins. Free rotation occurred when sufficient nonlayered surrounded block; some cases, segments former remain attached rotated blocks. anisotropic rocks, have locally played a role, but processes during initial cracking, parallel at high angles anisotropy, intrusion channel flow. Subsequent eventual are identical those nearly rock. The driving forces development low-stress sites, dilation, uncertain, likely reflect interplay between regional stress, buoyancy stresses, gradients, properties, simply heating expansion cracking. Thus number drive (thermal shattering, roof collapse) whereas others occur over longer durations (incremental pulsing complexes, deformation).