| 秦岭构造带与转换断层 |
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| THE QINLING TECTONIC BELT AND TRANSFORM FAULT |
| Transform faulting is a major control on the generation and evolution of the Qinling tectonic belt. The formation of the Caledonian Qinling sea, like the Cretaceous Mediterranean sea which resulted from eastward movement of the African continent relative to the Eurasian continent, was due to eastward movement of the North China block relative to the Yangzi block caused by a spreading of the Qilian ocean, along the Shangdan fault zone. Thus, it may be considered that the Shangdan fault zone is a transform-extension fault in cha-racter, which is responsible for the opening of the Qinling sea.Because of the oblique subduction of the Qinling sea along the' Shangdan fault zone, the North Qinling islandarc zone and marginal sea were formed. As a convergence of the continental blocks took place and the subduction was subsequently interrupted, the oblique subduction along the Shangdan fault zone was gardually changed to a sinistral strike-slip movement and a collision be- tween the island-arc and the North China block caused by compression occurred, which resulted in the North Qinling Caledonian! erogenic belt. However, only regional uplifting rather than orogenesis occurred in the South Qinling area.Following the ceasing of the subduction process, the sinistral movement of the Shangdan fault zone caused its further extension towards the Kunlun zone to separate the Qaidam block from the Yangzi block.The eastward movement of the Yangzi block relative to the North China block led to the formation of a Hercynian transform basin in the southern Qinling area, as indicated by a number of evidence such as higher sedimentation rate, rapidly lithofacies changs, dextral-stepping pattern, minor magmatism and association with a Hercynian"fold belt". The presence of an ophiolitic assemblage in the western part of the transform basin suggests a small-sized protooceanic basin.A spreading of the Jinshajiang ocean during Permian time resulted in the establishment of the Kunlun erogenic belt to the north. The southern Qinling basin again changed into an extensional feature, immediately after a compression of the original basin. This extensional basin may be connected with the Jinshajiang palaeotethys through the Bayan Har"triangular area". This space relationship suggests that the southern Qinling Indosinian basin should be an aulacogen in character, whlich may be interpreted to be a composite basin superimposed over a small transform oceanic basin between two plates. It can be suggested that the Qinling orogenic belt seems to be similar to Tethyan orogenesis in character, based on the above analyses. |
| PAN Xing-nan.1993.THE QINLING TECTONIC BELT AND TRANSFORM FAULT[J].Acta Geoscientica Sinica,14(1):29-38. |
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