TIME-SPATIAL DEVELOPING FEATURES OF CO-EXISTED INHERITED AND NEOGENIC STRUCTURES AND THEIR GUIDENCE TO MARINE ORIGIN OIL-GAS EXPLORATION IN THE TARIM CRATON

The Tarim Craton was created in the Jinningian orogeny by amalgamation of the North Tarim and South Tarim Blocks,with the basement structures being varied in its northern,middle and southern parts.The paper discussed,in succession of tectonic cycles,the neogenic structures in each part,including the ages,orientations and active modes.Their mechanisms were explorated in the light of coupled evolution with the surrounding orogenies.The guidence to marine origin oil-gas exploration was analysed,which revealed the NW-striking neogenic structure in central Tarim controlling the lithologic pool,and the fractures with varied orientation in northern Tarim playing different roles in oil-gas migration.Based on a comparative study with the Yangtze Craton,three distinctions could be summed up.1)The marine oil-gas in the Tarim Craton was mainly accumulated in Late Hercynian-Indosinian.The key was to understand the laws of adjustment or later secondary accumulation of the ancient pool in the Himalayan cycle since the Yanshanian movement being relatively gentle.2)In each tectonic epoch of marine deposition,some neogenic structures with varied orientations might be mobile synchronously,and the Paleozoic neogenic structures might react in the Cenozoic.It was complicated fault systems and their repeated activities that resulted in oil-gas accumulation,later adjustment or secondary accumulation,and creating a large scale multiple oil-gas accumulation play.3)The Paleogene gypsum-salt layer became an interlayer-gliding fault.The Cenozoic thrusts,stretching downwards,converged onto the layer so that the Paleozoic marine deposits and oil-gas pools relatively well reserved.The deformation mode of the Paleozoic was faulting,with folding being constrained by the faults,so the petroliferous structural belts should be fault ones.