MESOZOIC AND CENOZOIC MAGMATIC ACTIVITIES OF CONTINENTAL MARGIN AND ISLAND ARCS IN EAST ASIA AND PLATE TECTONICS
亚洲东部陆缘及岛弧区中—新生代的岩浆活动与板块构造

In the geological evolution of the coastal region of the Pacific Ocean inEast Asia during the Mesozoic and Cenozoic eras, two outstanding characteristics can be recognized, i. e., the appearance of well-known magmatic beltscomposed of widely developed igneous rocks, and the formation of a seriesof fault-depressed basins, including fringing seas, marginal seas and some interior basins. The former contain various kinds of endogenous minerals whilethe latter are abundant in energy resources. According to recent studies, wesuggest that the formation of these huge magmatic zone and basins is theresults of deep melting and partial division and extension caused by subduction, when convergence between the Pacific Ocean and the Eurasian platestook place since the Mesozoic era. There are three associations of intrusive and eruptive rocks in East Asia.The first one consists of basic and ultrabasic complex developed during theearly geosynclinal stage or under mid-ocean ridge conditions and submarinebasic pillow lava accompanied with radiolarian siliceous rock and graywacke.Besides forming oceanic crust and marginal sea floor, this ophiolite association sometimes occurs as narrow stripes in orogenic belts; also it may appearin a flysch formation as allochthonous rock, thus constituting an ophiolitemelange zone.Two roughly parallel ophiolitic or ophiolite-melange zones arediscovered in East Asia:the interior ophiolite belt distributed intermittently inKoryak Range, Sikhote-Alin Mountains, the islands of Sakhalin, Hokkaido,Honshu and Shikoku, as well as Nadanhada Range and the coastal region ofFujian Province is mainly of late-Palaeozoic to early Mesozoic age; the exteinal melange belt is of Mesozoic age and appears in eastern Kamchatka,the Shimanto zone of Southeastern Japan, coast mountains in Taiwan Province of China, Luzon, etc. The second association developed along the continental active margin orisland-arc zone and belonging to intermediate acid calc-alkali series is madeup of diorite, granodiorite, basalt, andesite, dacite, liparite, etc. The Mesozoicrocks of this type can be found along the coast of Okhotsk sea, the Sikho-te-Alin, Laoye Mountain and Zhangguangcai Mountain, Japan, Korea, andfujian and Zhejiang provinces of China. The isotopic age of the intrusiverocks is 62-214 m. y. (in Fujian), 68-225 m. y. (in Korea), or 50-95 m. y. (inSouthwestern Japan), obviously indicating that the rocks get younger fromNW to SE. The volcanic rocks in East China occur chiefly in the upper Jurassic and Cretaceous formation, showing isotopic age of 70-140 m. y. The Cenozoic rocks of this association appear in an external belt in Kamchatka, Kurileislands, Ryukyu islands, Luzon and other places, with the intensity of magmatic activities weaker than those of the Mesozoic. These two age groups ofigneous association are found respectively at the western side of the twoophiolite zones mentioned above, thus forming two notable "pair belts". The third association which is