南沙微板块边界的动力学演化

南沙微板块的四周为性质不同的超壳边界断裂所围限,北为长龙-黄岩扩张断裂带,南为八仙-巴兰-约克-库约推复断裂带,西为万安-纳土纳走滑拉张断裂带,东为马尼拉-班乃走滑挤压断裂带,它们共同以南沙软流圈顶面为拆离面.该微板块在新生代的动力学过程可分为四个阶段:K₂-E₂1,南沙微板块沿北部的康泰-双子-雄南断裂带伸展,裂离华南-印支陆缘,古南海向南俯冲,西布增生楔形成;E₂2-E₃1,西南次海盆沿长龙扩张脊断裂带扩张,西布增生楔碰撞造山;E₃2-N₁1,中央次海盆沿黄岩扩张脊断裂带扩张,米里增生楔形成,北巴拉望南缘“A”型俯冲;N₁2至现在,南部边界断裂大规模向北逆冲推复造山,南海扩张停止.

On dynamic process and boundary faults' kinematic characteristics of Nansha microplate

The features and present positions of the boundary faults of Nansha microplate and its dynamic process during Cenozoic are discussed.According to the view point of "interlayer-glide-dip-slip-strike-slip 4-dimensional associated fault systematic motion of laye-rblock tectonics",it is proposed that the microplate is enclosed by differe transcrustal faults and can be regarded as a typical Cenozoic microplate.Facts show that the northern boundary the micr oplate moves to the present location of Chang long-Huangy an seamount chain (spreading ridge fault zone) from Kangtai-Shuangzi-Xiongnan transcrustal normal dip-slip fault zone,Baxian-Baram-Yoca-Cuyo trascrustal reversed-slip thrust fault zone as the southern boundary,Wan'an-Natuna transcrustal strike-slip pullapatransfer zone as the western boundary and Manila-Panay transcrustal strike-slip compressional transfer zone as theastern boundary.These boundary fault zones take the same top layer of Nansha asthenosphere as their shared dtachmental layer.In the light of the viewpo int of multivariant dynamic force origin,the Cenozoic dynamic process the microplate can be divided into four stages.(1) K₂-E₂¹,the delamination of lower lithosphere of South Chin continental margin resulted in the microplateps dispersing away from the margin of SE China-Indochina continen paleo-South China Sea(SCS) southward subducting under Sunda craton in the SW section of the southern bounda and under the oceanic crust of eastern Calimantan-Sulawesi Sea in the SE section of the southern boundary respetively,and the formation of Sibuaccretion wedge.(2) E₂²-E₃¹,eastward hydraulic-pressure-transfe-rtype creepo the mantle flew under Tibet plateau lithosphere,eastward strike-slip extrusion of East A sian lithosphere and equtorward longitudinal inertia for cecaused by the incr ease of the earthps rotation rate,all of these forces initiated thopening of SW subbasin of the SCS,Sibu accretion wedge's collision with Kuching zone and the formation of C gayan-Kalumpang-Tungku-Sulu volcanic arc.(3) E₃²-N₁¹,the central subbasin of the SCS opened,Miriaccrtion wedge formed.Mean while,Sulawesi Sea northwards subducted under Sulu arccaused by northward driftin and compression of Australian plate,Sulu Sea opened in Cagayan-Suluarc.And the southern margin of N or Palawan continental block subducted under Cagayan volcanic ridge,like the A-type subjection.(4) N₁² to present the collision of the Australian-derived Banggai-Sula block with the northernarm of Sulawesi caused the southe boundary fault zone of the microplate thrusting and orogenic movementon a large-scale.And the spreading of the SCS stopped.