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Suture zones located across the Tibetan region clearly demarcate the rift-and-drift and continental accretion history of the region. However, the intraplate responses to these marginal plate-tectonic events are rarely quantified. Our understanding of the Paleo-Tethyan orogenic system, which involved ocean opening and closing events to grow the central Asian continent, depends on the tectonic architecture and histories of major late Paleozoic−early Mesozoic orogenic belts. These opening and collision events were associated with coupled intracontinental deformation, which has been difficult to resolve due to subsequent overprinting deformation. The late Paleozoic−early Mesozoic Zongwulong Shan−Qinghai Nanshan belt in northern Tibet separates the Qilian and North Qaidam regions and is composed of Carboniferous−Triassic sedimentary materials and mantle-derived magmatic rocks. The tectonic setting and evolutional history of this belt provide important insight into the paleogeographic and tectonic relationships of the Paleo-Tethyan orogenic system located ∼200 km to the south. In this study, we integrated new and previous geological observations, detailed structural mapping, and zircon U-Pb geochronology data from the Zongwulong Shan−Qinghai Nanshan to document a complete tectonic inversion cycle from intraplate rifting to intracontinental shortening associated with the opening and closing of the Paleo-Tethyan Ocean. Carboniferous−Permian strata in the Zongwulong Shan were deposited in an intracontinental rift basin and sourced from both the north and the south. At the end of the Early−Middle Triassic, foreland molasse strata were deposited in the southern part of the Zongwulong Shan during tectonic inversion in the western part of the tectonic belt following the onset of regional contraction deformation. The Zongwulong Shan−Qinghai Nanshan system has experienced polyphase deformation since the late Paleozoic, including: (1) early Carboniferous intracontinental extension and (2) Early−Middle Triassic tectonic inversion involving reactivation of older normal faults as thrusts and folding of pre- and synrift strata. We interpret that the Zongwulong Shan−Qinghai Nanshan initiated as a Carboniferous−Early Triassic intracontinental rift basin related to the opening of the Paleo-Tethyan Ocean to the south, and it was then inverted during the Early−Middle Triassic closing of the Paleo-Tethyan Ocean. This work emphasizes that pre-Cenozoic intraplate structures related to the opening and closing of ocean basins in the Tethyan realm may be underappreciated across Tibet.
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Impact of rift history on the structural style of intracontinental rift-inversion orogens
Abstract Although many collisional orogens form after subduction of oceanic lithosphere between two continents, some orogens result from strain localization within a continent via inversion of structures inherited from continental rifting. Intracontinental rift-inversion orogens exhibit a range of structural styles, but the underlying causes of such variability have not been extensively explored. We use numerical models of intracontinental rift inversion to investigate the impact of parameters including rift structure, rift duration, post-rift cooling, and convergence velocity on orogen structure. Our models reproduce the natural variability of rift-inversion orogens and can be categorized using three endmember styles: asymmetric underthrusting (AU), distributed thickening (DT), and localized polarity flip (PF). Inversion of narrow rifts tends to produce orogens with more localized deformation (styles AU and PF) than those resulting from wide rifts. However, multiple combinations of the parameters we investigated can produce the same structural style. Thus, our models indicate no unique relationship between orogenic structure and the conditions prior to and during inversion. Because the style of rift-inversion orogenesis is highly contingent upon the rift history prior to inversion, knowing the geologic history that preceded rift inversion is essential for translating orogenic structure into the processes that produced that structure.
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- Award ID(s):
- 2050623
- PAR ID:
- 10592591
- Publisher / Repository:
- Geological Society of America
- Date Published:
- Journal Name:
- Geology
- Volume:
- 52
- Issue:
- 6
- ISSN:
- 0091-7613
- Page Range / eLocation ID:
- 429 to 434
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1130/G51489.1
