HR: 1330h
AN: T12C-0466    [PDF]
TI: Tectonic Mechanisms Associated with Metamorphic P-T Paths: Alternatives to Thrusting-Thermal Relaxation Cycles
AU: * Wakabayashi, J
EM: wako@tdl.com
AF: Consultant, 1329 Sheridan Lane, Hayward, CA 94544 United States
AB: Geoscientists commonly use metamorphic pressure (P)-temperature (T) paths to interpret the tectonic history of orogenic belts. Many studies and reviews relating P-T path development to tectonics have focused on thrusting-thermal relaxation cycles, generally associated with collisional processes. Most of the P-T paths interpreted this way have been 'clockwise' (P on the positive y-axis) paths. This emphasis may partly reflect the fact that collisional processes can account for an entire burial-exhumation cycle. P-T paths, however, generally do not record an entire burial-exhumation cycle, because metamorphic mineral growth did not occur at the lowest grade parts of the paths. In addition, many P-T paths may have formed from multiple, unrelated, tectonic events instead of a single event as commonly assumed. Many P-T paths interpreted in the last decade and a half differ markedly from clockwise P-T loops. Such paths include hairpin, isobaric hairpin, isobaric cooling, and anticlockwise P-T paths. The variety of tectonothermal processes affecting large parts of the Earth, in addition to the tectonic settings of many metamorphic terranes, suggest that P-T paths recorded in rocks result from a greater variety of tectonic processes than are generally considered. Some of these processes may include subduction initiation, continuous subduction, triple junction interactions, initiation and shut off of arc magmatism, subcontinental delamination, and hot spot migration. I will present examples of different types of P-T paths and their possible relationship to tectonic processes. Although thrusting-heating cycles have influenced metamorphic evolution in many orogenic belts, the potential impact of other types of tectonic mechanisms should not be overlooked.
DE: 8102 Continental contractional orogenic belts
DE: 8105 Continental margins and sedimentary basins
DE: 8110 Continental tectonics--general (0905)
DE: 8150 Plate boundary--general (3040)
DE: 8199 General or miscellaneous
SC: Tectonophysics [T]
MN: 2003 Fall Meeting