Publication details for Professor Yaoling NiuNiu, Yaoling (2005). Generation and evolution of basaltic magmas: Some basic concepts and a new view on the origin of the Mesozoic-Cenozoic volcanism in eastern China. Geological Journal of China Universities 11(1): 9-46.
- Publication type: Journal Article
- ISSN/ISBN: 1006-7493
- Keywords: Mantle peridotite, partial melting, magma generation and evolution, eastern China, lithosphere thinning, Mesozoic and Cenozoic volcanism, a special case of plate tectonics
- Further publication details on publisher web site
Author(s) from Durham
Some basic concepts of basaltic magma generation and evolution are discussed in the context of global tectonics. These concepts need better understanding before invoking elusive possibilities in igneous petrogenesis on all scales and in all tectonic environments. A hypothesis for the Mesozoic lithosphere thinning and Mesozoic/Cenozoic basaltic volcanism in eastern China is presented. This hypothesis is consistent with observations and complies with basic physics. While the eastern China volcanism can be defined as “intra-plate” volcanism, it is in fact a special consequence of plate tectonics. The Mesozoic lithosphere thinning in eastern China is best explained by a process that “transformed” the deep portion of the lithosphere into convective asthenosphere by hydration. The water that did so may come from dehydration of subducted Pacific (or predecessor) oceanic lithosphere that is presently lying horizontally in the transition zone beneath eastern Chinese continent as detected by seismic tomographic models. The Mesozoic volcanism may be genetically associated with the lithospheric thinning because the basaltic source is ancient isotopically enriched (Nd < 0) lithosphere - being converted to the asthenosphere. The NNE-SSW Great Gradient Line (GGL) marked by the sharp altitude, gravity anomaly, crustal thickness, and mantle seismic velocity changes from the plateau west to the hilly plains of eastern China is an expression of variation in lithospheric thickness from probably > 150-200 km beneath the plateaus in the west to the thin, probably < 80 km, beneath eastern China. The “remote” western Pacific subduction systems induce asthenospheric flow from beneath eastern China towards the subduction zones, which, in turn, requires asthenospheric material replenishment from beneath the plateaus to the eastern China. As a result, such eastward asthenospheric flow experiences an upwelling and decompression (from beneath thickened to thinned lithosphere), which causes the flowing asthenosphere (e.g., Nd > 0) to partially melt and produce Cenozoic eastern China basaltic volcanism. Such volcanism may have actually begun at the end of the Mesozoic lithosphere thinning in the late Cretaceous. This simplistic concept is currently being substantiated with detailed petrologic and geochemical data.