|
Detailed Reference Information |
Hacker, B.R., Ratschbacher, L., Webb, L., McWilliams, M.O., Ireland, T., Calvert, A., Dong, S., Wenk, H. and Chateigner, D. (2000). Exhumation of ultrahigh-pressure continental crust in east central China: Late Triassic-Early Jurassic tectonic unroofing. Journal of Geophysical Research 105: doi: 10.1029/2000JB900039. issn: 0148-0227. |
|
The largest tract of ultrahigh-pressure rocks, the Dabie-Hong'an area of China, was exhumed from 125 km depth by a combination of normal-sense shear from beneath the hanging wall Sino-Korean craton, southeastward thrusting onto the footwall Yangtze craton, and orogen-parallel eastward extrusion. Prior to exhumation the UHP slab extended into the mantle a downdip distance of 125--200 km at its eastern end, whereas it was subducted perhaps only 20--30 km at its far western end ~200 km away. Structural reconstructions imply that the slab was >10 km thick. U/Pb zircon and 40Ar/39Ar geochronology indicate that exhumation up to crustal depths occurred diachronously between 240 and -225--210 Ma, reflecting a vertical exhumation rate of >2 mm/yr. The upper boundary of the slab is the Huwan shear zone, a normal-sense detachment that reactivated the plate suture. The lower boundary is represented by the Lower Yangtze fold-thrust belt. NW-trending stretching lineations, NE-vergent, WNW--ESE trending 〈a〉 folds, dominant top-NW shear, and conjugate, but overall asymmetric, shear band fabrics, document that exhumation was accomplished by updip and orogen-parallel extrusion accompanied by layer-parallel thinning. The orientation and shape of the folds, and a change from SE to SW flow directions, imply that the slab rotated clockwise about a western pivot during exhumation; this rotation was likely caused by the eastward increasing depth of subduction mentioned above, combined with a possible marginal basin and a weak eastern plate boundary. Exhumation of the slab produced considerable shortening in the Lower Yangtze fold-thrust belt, perhaps producing the foreland orocline. ¿ 2000 American Geophysical Union |
|
|
|
BACKGROUND DATA FILES |
|
|
Abstract |
|
|
|
|
|
Keywords
Mineralogy and Petrology, Metamorphic petrology, Structural Geology, Tectonophysics, Tectonophysics, Continental contractional orogenic belts |
|
Publisher
American Geophysical Union 2000 Florida Avenue N.W. Washington, D.C. 20009-1277 USA 1-202-462-6900 1-202-328-0566 service@agu.org |
|
|
|