Comparison of mantle-derived matierals from different spatiotemporal settings: Implications for destructive and accretional processes of the North China Craton |
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Authors: | JianPing Zheng |
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Institution: | State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences, Wuhan 430074, China |
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Abstract: | Cratonic destruction or lithospheric thinning beneath North China makes it as one of the most ideal areas for the studying
on the formation and evolution of continent. However, the mechanism, time, range and dynamic setting of the destruction, even
the lithospheric status before the destruction, are contentious. The comparison among mantle xenoliths in the volcanic rocks
from different captured times (e.g. Paleozoic, Mesozoic and Cenozoic) and locations (e.g. intra-plate or its rim, the translithospheric
Tanlu fault or the North-South Gravity Line), and peridotitic massifs within the Sulu-Dabie ultrahigh-pressure metamorphism
belt along the southern margin of the North China Craton, indicates that (1) the cratonic lithosphere is heterogeneous in
structure and composition, and contains mantle weak zones; and (2) the Mesozoic-Cenozoic lithospheric thinning process is
complex, including lateral spreading of lithosphere, interaction between melt and peridotite, non-even asthenospheric erosion
(huge lithospheric thinning), and the limited lithospheric accretion and thus thickening, which resulted in the final replacement
of the refractory cratonic lithosphere by juvenile fertile mantle. In early Mesozoic, the integrity of the North China Craton
was interrupted, even destroyed by subduction and collision of the Yangtze block. The mantle wedge of the North China Craton
was also metasomatized and modified by melt/fluids revealed from the subducted Yangtze continent. Lithospheric mantle extension
and tectonic intrusion of the North China Craton also occurred, accompanied by the asthenospheric upwelling that due to the
detachement of the subducted Yangtze continent (orogenic root). During early Cretaceous-early Tertiary, the huge thinning
of lithosphere was triggered by the upwelling asthenosphere due to the subduction of the Pacific plate. Since late Tertiary,
the cooling of the upwelling asthenosphere resulted in the replacement of the mantle in existence by the newly accreted lithosphere,
accompanied with a little thickness in lithosphere and thus finally achieved the lithospheric thinning as a whole. The translithospheric
faults, such as the Tanlu fault, play excellent channels for asthenospheric upwelling. Meanwhile, the channels in lithosphere
are usually irregular, which resulted in different eruption times of magma. Peridotite xenolith in the basalts erupted at
100 Ma is mainly fertile, indicating such a fact, that is, the mantle replacement occurred before the eruption (e.g. 125–100
Ma) beneath the eastern part of the North China Craton. |
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Keywords: | cratonic destruction North China peridotite different spatiotemporal settings heterogeneity |
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