THE COMPARISON OF THE OROGENIC PROCESSES IN THE CIRCUM-PACIFIC AREA DURING JURASSIC-CRETACEOUS PERIOD

In Jurassic-Cretaceous period, namely 200-80 Ma, corresponding to the multi-stage cracking of Gondwana land in the Southern Hemisphere, multi-stage orogeny widely appeared in the Northern Hemisphere, including the typical orogenic movement, namely, Jurassic-Cretaceous orogeny in the Pacific Rim region. It is generally acknowledged that the orogeny during Yanshan Period in Asia and Navoda orogeny in western North America mainly occurred at the middle and late Jurassic Period, i.e., 170-165 Ma ,155-140 Ma and 120-105Ma. In these orogenic processes, some grand zones were formed in Pacific Rim, including accretionary complex zone on the continental margin, intracontinental orogenic zone, volcano-magmatic zone, thrust-nappe structural zone, strike-slip shear zone and regional metamorphic zone. While in the orogenic intervals, namely 140-125 Ma and 100-90 Ma, there commonly happened magmatism related to the lithospheric extension in the Pacific Rim region.. Large amounts of metamorphic core complex and extension and pull-apart basins were developed in East Asia and the west part of North America in the Cretaceous period during 140-125 Ma and 100-80 Ma respectively. The Jurassic-Cretaceous orogenic event in the circum-pacific region occurred under the circumstance of the Gondwanan breakup of the Southern Hemisphere. It was closely associated with the decrement process of ancient Pacific plate and has been regarded as an essential geological record concerning the convergence of the continents in north hemisphere. With constant change of Jurassic-Cretaceous oceanic -continental tectonics pattern, the global climate, environment, and creature have shown a profound change. Rich mineral resources are formed in the process of the accretion and orogenesis of the continental margin in Jurassic and Cretaceous periods. The background and dynamic mechanism of the Jurassic-Cretaceous tectonics in Western North America and East Asia are quite similar through comparison. Therefore, it is necessary to conduct a research on renaming and comparing the Jurassic-Cretaceous tectonics process of these two typical regions.