Zhang, G, -W, Bai, Y.-B., Sun, Y., Guo, A, -L., Zhou. D. -W. and Li, T. -H., 1985. Composition and evolution of the Archaean crust in central Henan, China, Precambrian Res., 27: 7-35

The Qinling orogen is a composite continental orogen with a complex evolutionary history. During the Early and Middle Proterozoic, it was a continental rift; in the late Proterozoic, it began to be part of a plate tectonic regime; from the Palaeozoic to Early Mesozoic, it was involved in subduction-collision between three plates; and in the Mesozoic and Cenozoic, it was affected by intracontinental postorogenic tectonism. The Qinling orogen has a flyover-shaped, 3-D lithospheric architecture. Palaeozoic. Two limited oceans originated dunng this time and the Qinling microplate was then separated from the north China plate and the Yangtze plate. Subduction of oceanic crust took place in the Early and Middle Palaeozoic, accompanied by coeval vertical underplating and accretion. Continent-continent collision occurred from the Carboniferous to the Middle Triassic in an oblique and diachronous fashion, creating two major suture zones, that is, the northern Shangdan suture zone and the southern Mianlue suture zone. Intense Mesozoic-enozoic intracontinent orogeny brought about rapid uplift and eventually formed the present-day Qinling.

On the basis of synthetic studies of geology, geophysics and geochemistry, the present Qinling Orogenic Belt can be described as a 3-d "flyover-type" geometricmode lwith rheological layering structures. Furthermore, the tectonic dynamic analyses have been done on the structural geometryand kinematic features. Thus it can be concluded that its present structure has resulted from an adjustment of deep-seated mantle dynamics and lithosphere coupling relationship sinoe the Mesozoic-Cenozoic time.

The Qinling mountains are a typical composite continental orogenic belt which underwent various vstages of evolution characterized by different tectonic regimes. Its late Proterozoic to early Mesozoic evolution was dominated by plate subduction and collision processes. The Shangdan fault zone marks the major suture which resulted from the plate subduction and collision and represents the basic division in both the superficial geology and the deep-seated crustal structure of the Qinling mountains. It is not a simple fault zone but an intricate geologic terrane, characterized by a prolonged and complicated history. It is referred to as Shangdan boundary fault terrane or Shangdan zone for short. The Shangdan zone consists chiefly of five parts: (I) fault systems as marked by various types of mylonite and cataclasite, (2) tectonic assemblages of Danfeng ophiolite blocks, (3) tectonic assemblages of obducted slices of a sedimentary prism, (4) granitic rocks related to orogenic processes of subduction and collision, and (5) basins controlled by late brittle faults. The evolution of the Shangdan zone can be traced through three major stages: the Caledonian period of subduction, the lndosinian period of collision and orogeny. and the Mesozoic-Cenozoic period of intra plate deformationm, among which the Indosmiaan peried marks the most importam stage in its development. In brief, the Shangdan zone is the major division between the ancient lithospheric plates in the Qinling belt and extends deep into the upper mantle.

The Mianlue tectonic zone (Mianlue zone), an ancient suture zone in addition to the Shangdan suture in the Qinling-Dabie orogenic belt, marks an important tectonic division geologically separating north from south and connecting east with west in China continent. To determine present structural geometry and kinematics in the Mianlue tectonic zone and to reconstruct the formation and evolution history involving plate subduction and collision in the Qinling-Dabie orogenic belt, through a multidisciplinary study, are significant for exploring the mountain-building orogenesis of the central orogenic system and the entire process of the major Chinese continental amalgamation during the. Indosinian.