THE BUILDING OF SOUTH CHINA - COLLISION OF YANGZI AND CATHAYSIA BLOCKS, PROBLEMS AND TENTATIVE ANSWERS

This paper aims to give answers to the questions of timing, tectonic s tyle and geodynamic interpretation of south China geologic development . In the middle Jiangnan segment, Yangzi plate and Cathaysia got clear ly welded during a Late Proterozoic orogeny of collisional type, marke d by HP/LT metamorphism, ophiolite melange obduction, thrusting of gre enschist nappes, emplacement of collisional S-type granites. This coll ision, which built the initial Jiangnan belt, began around 950 +/- 40 Ma and was completed at about 770-800 Ma ago. Kinematic study indicate s that the Cathaysia plate was underthrust beneath the Yangzi plate. A likely earlier collisional event occurred around 1500 Ma, but is poor ly preserved in the studied area. The proposed geodynamic model implie s two successive suturings of oceanic domains during the Middle-Late P roterozoic: one about 1500 Ma and one about 950 Ma. A strong remobiliz ation occurred during the Early Paleozoic 'Caledonian' orogeny, which induced transpressive ductile deformation. Thin-skinned folding and th rusting took place during the Mesozoic; this intracontinental shorteni ng could be due to collision between the China-Indochina and west Phil ippines blocks. South China is a composite block, comprising the relie s of at least three, maybe four sutures from Jiangnan to the coast. Co pyright (C) 1996 Elsevier Science Ltd