东北亚南区中—新生代大地构造轮廓

东北亚南区是西太平洋构造带、北美大陆板块(或鄂霍次克板块)与中亚造山带、中朝、扬子板块等交汇部位,在泛大陆(Pangaea)拼合、裂解的宏观背景下中—新生代以来经历了多次构造事件的叠加,构造面貌比较复杂。包括朝鲜半岛在内,许多中—小型陆块的构造归属长期以来一直存在着争议,笔者根据近年来SHRIMP测年信息、生物古地理和相邻构造带的延伸,认为朝鲜半岛、日本飞驒—隐歧地块古生代应该归属于中朝板块;萨哈林岛—日本北海道归属于北美板块;布列亚—佳木斯—兴凯地块古生代归属于西伯利亚板块。20世纪80年代以来绝大多数学者都把本区中生代以来的构造发展同西太平洋壳向东北亚大陆的俯冲联系在一起,然而近年相当多学者从东亚大陆本身的陆-陆碰撞-挤出-扩张来寻求晚中生代以来地壳-岩石圈减薄的地球动力学原因。本区经历了晚海西—印支期古亚洲洋消亡和晚燕山期(晚侏罗—早白垩世)南北大陆的陆-陆碰撞汇聚两个时期,使中亚造山带扩展到中朝板块北缘的阴山—燕山地区,使地壳增厚,形成与现今青藏高原类似的高原地貌;早白垩世晚期—古近纪本区地壳-岩石圈减薄,出现大规模伸展型盆-山结构,郯—庐断裂北延,出现左行走滑错移,东部陆缘俯冲增生、太平洋板块运动转向,引起的挤压变形,以及古近纪晚期大面积准平原化,黑龙江、吉林古近纪隆起边缘断陷盆地中的许多重、贵金属砂矿矿床也多半形成在此期;新近纪本区地壳-岩石圈进一步减薄,大陆裂谷扩展为东亚—西太平洋裂谷带,形成NNE向伸展型盆-山结构,日本海打开,西太平洋岛弧形成,早更新世末初步形成地形阶梯,晚更新世以后才形成了控制着地热与水系分布的现今地貌格架。

Mesozoic-Cenozoic tectonic framework of southern Northeast Asia

Southern Northeast Asia covers the area where the West Pacific tectonic belt, North America or Okhotsk Plate, Central Asia orogenic belt, the Sino-Korea and the Yangtze blocks meet together. In the course of Pangaea and supercontinent assembling and disintegration this belt has experienced multple tectonic events since the Mesozoic and has acquired a rather complicated structure. The tectonic affiliation of many middle-scaled and small scaled blocks, including that of the Korea Peninsula, have long been disputed. Based on recent obtained SHRIMP geochronologic data and palaeobiogeographic and tectonic evidences, the authores in this paper deem that the Korea Peninsula and the Hida-Oki belt of Japan might have been affiliated to the Sino-Korea Plate during the Paleozoic, Sakhalin-Hokkaido massifs, to the North America Plate, and the Bureya-Jiamusi-Khanka massifs, to Siberia Plate. Since the 80's of last century most authors have regarded the discussed area as connected with the westward subduction of the West Pacific oceanic crust under Northeast Asia since the Mesozoic. But recently more and more scholars prefer to interpret the geodynamics of crust-lithospheric thinning of Eastern Asia from continent collision and extrusion. The southern Northeast Asia belt has experienced two stages of tectonic development: consumption of the Palaeo-Asian Ocean during the late Hercynian-Indosinian epoch and convergence-collision between the southern and the northern continents during the late Yanshanian epoch (late Jurassic to early Cretaceous). It was these processes that resulted in the extension of the Central Asia orogenic belt to the Yinshan-Yanshan region at the northern edge of the Sino-Korea plate and the formation of a plateau morphology caused by crustal thickening similar to the Qinghai-Tibet Plateau today. In the late Cretaceous to Palaeogene, the crust-lithosphere thinning of this area caused the appearance of large scale extension type Basin-Range structure. In the meantime, the northward section of the Tanlu faults system underwent sinistral displacement. Along the East Asia continental margin occurred accretion, and the rotation of the Pacific plate caused compressional deformation and extensive peneplanation. Many heavy metal and noble metal placeres in the fault basins bordering Palaogene uplifts in Heilongjiang and Jinin were formed in this period. In the Neogene the crust-lithosphere further thinned and the continental rifts developed into the East Asia-Pacific rift belt and the NNE-trending Basin-Range structure came to appear. The Sea of Japan opened, the Western Pacific island arcs appeared. The recent topographic steps of China was initiated at the end of the Early Pleistocene. But the present geomorphic frame that controls the nowadays climate and river system was not formed until post-late Pleistocene time.