Journal
JOURNAL OF ASIAN EARTH SCIENCES
Volume 114, Issue -, Pages 649-673Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jseaes.2014.10.004
Keywords
Qinling Orogen; Apatite fission-track analysis; Propagation of uplift and exhumation; Intracontinental deformation
Categories
Funding
- National Science Foundation of China [41102126, 91114204]
- Chinese Government's Executive Program [SinoProbe-08-01-03]
- China Geological Survey Program [1212011220259]
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The Qinling Orogen of central China was formed by intracontinental collision between the North and South China Blocks. The orogen comprises several micro-blocks bounded by sutures and faults, and has undergone long-term intracontinental deformation since the Late Triassic. The micro-blocks include the southern margin of the North China Block (S-NCB), the Northern Qinling Belt (NQB), the Southern Qinling Belt (SQB), and the northern margin of the South China Block (N-SCB). Under a uniform tectonic setting in late Mesozoic-Cenozoic, these micro-blocks have been subjected to a range of deformation styles, as demonstrated by their structural deformation, history of magmatism, and the development of sedimentary basins. To investigate the differences among the micro-blocks and to quantify their uplift and exhumation, we obtained 45 rock samples from eight Mesozoic granites in these micro-blocks, and conducted apatite fission-track (AFT) thermochronological modeling. The results reveal that the Qinling Orogen underwent four distinct stages of rapid cooling histories during the late Mesozoic-Cenozoic, and showed variation in uplift and exhumation whereby the intracontinental deformation started in the south (the N-SCB) and propagated to the north (S-NCB). In the first stage, during the Late Jurassic-Early Cretaceous (ca. 160-120 Ma), rock cooling occurred mainly in the N-SCB, attributed to the clockwise rotation and northward subduction of the South China Block beneath the Qinling Orogen. In the second stage, compression- and extension-related uplift was initiated during the late Early Cretaceous-early Late Cretaceous (ca. 120-90 Ma) in the SQB, consistent with the southward subduction of the North China Block and broadly extensional deformation in the eastern China continent. In the third stage, a gentle regional-scale cooling event that occurred during the latest Cretaceous-Paleocene (ca. 90-50 Ma) started in the NQB and became widespread in the Qinling Orogen. This regional-scale uplift and exhumation event was probably a response to the opposite polarity subduction beneath the Qinling Orogen combined with the effects of subduction of the Pacific Plate from the southeast. The fourth stage (Eocene-Oligocene, ca. 50-20 Ma) was marked by another phase of rapid cooling in the S-NCB, the NQB, and the NW-SQB, and is interpreted as being cause by the eastward tectonic escape of Tibetan Plateau related to India-Asia collision. Furthermore, the record of variable timings and rates of cooling of these micro-blocks, together with regional structural analysis, indicates that the late Mesozoic-Cenozoic intracontinental deformation in the Qinling Orogen was characterized by a spatiotemporally variable and propagating-style uplift and exhumation of the micro-blocks, and the predominant deformation was through displacement across various boundary sutures and faults. (C) 2014 Elsevier Ltd. All rights reserved.
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