Geochronological constraints on 140–85 Ma thermal doming extension in the Dabie orogen, central China |
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| Authors: | Xu Changhai Zhou Zuyi Ma Changqian and Peter W Reiners |
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| Institution: | (1) MOU Laboratory of Marine Geology, Tongji University, 200092 Shanghai, China;(2) Faculty of Earth Sciences, China University of Geosciences, 430074 Wuhan, China;(3) Department of Geology, Washington State University, 99164-2812 Pullman, WA, USA |
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| Abstract: | Regional architecture of geochronology and differential cooling pattern show that the Dabie orogen underwent a thermal doming
extension during 140–85 Ma. This extension resulted in widespread re-melting of the Dabie basement, intense volcanic activities
in North Huaiyang and the formation of fault-controlled depressions in the Hefei basin. This thermal doming extension can
be further divided into two consecutive evolving stages, i.e. the intensifying stage (140–105 Ma) and the declining stage
(105–85 Ma). In the first stage (140–105 Ma), the thermal doming mainly was concentrated in the Dabie block, and to a less
degree, in the Hongan block. The thermal doming structure of the Dabie block is configured with Macheng-Yuexi thermal axis,
Yuexi/Luotian thermal cores and their downslide flanks. The orientation of thermal axis is dominantly parallel to the strike
of orogen, and UHP/HP units together with metamorphic rocks of North Huaiyang constitute the downslide flanks. The Yuexi core
differs from the Luotian core in both the intensity and the shaping time. To some extent, the Hongan block can be regarded
as part of downslide systems of the Dabie doming structure. The doming process is characterized by thermal-center’s migration
along the Macheng-Yuexi thermal axis; consequently, it is speculated to be attributed to the convective removal of thickened
orogenic root, which is a process characterized by intermittance, mi gration, large-scale and differentiation. During the
declining stage (105–85 Ma), the dome-shaped figure still structurally existed in the Dabie orogen, but orogenic units cooled
remarkably slow and magmatic activities stagnated gradually. Study on the thermal doming of Dabieshan Mountains can thus provide
detailed constraints on the major tectonic problems such as the UHP/HP exhumation model, the boundary between North Dabie
and South Dabie, and the orogenesis mechanism. |
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| Keywords: | Dabie orogen geochronology cooling pattern thermal doming extension |
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