Magma traps and driving pressure: consequences for pluton shape and emplacement in an extensional regime

摘要: Abstract The level of emplacement and final form felsic mafic igneous rocks the Wichita Mountains Igneous Province, southwestern Oklahoma, U.S.A. are discussed in light magma driving pressure, lithostatic load, crustal traps. Deposition voluminous A-type rhyolites upon an eroded gabbroic substrate formed a subhorizontal strength anisotropy that acted as trap for subsequent rising magma. Intruded along this sheet granites (length/thickness 100:1) Granite Group, which Mount Scott is typical, smaller plutons biotite bearing Roosevelt Gabbro. In marked contrast to granite sheets, gabbro more equant stocks with flat roofs steep side walls. Late Diabase dikes cross-cut all other units, but accompanying basaltic flows extremely rare volcanic pile. Based on magmastatic calculations, we draw following conclusions concerning shape these intrusions. (1) Magma can rise depth at pressure becomes negligible. maintains positive surface has potential erupt. (2) ascent may be arrested deeper crust by (i.e. trap) if greater than or equal load anisotropy. (3) Subhorizontal sheet-intrusions traps when greatly exceeds load. Under such conditions, sufficent lift overburden create necessary space intrusion. (4) Thicker steep-sided batholiths, roofs, approximates intrusion must created mechanisms (e.g. stoping). (5) Subvertical sheets dikes) less emplacement.