TECTONIC EVOLUTIONS OF SOME MOUNTAIN RANGES IN CHINA, AS TENTATIVELY INTERPRETED ON THE CONCEPT OF PLATE TECTONICS
LEE CHUN-YU (Geological Institute of Northwest China)
In order to facilitate the investigation of plate tectonic on the continent, the writer proposes some principles for references. They are: 1, the juncture between two plates is always represented by a great fault or fracture zone extending for at least several hundreds or usually more than one thousand kilometers long; 2, the sharp diversities of depositional phases and faunas on the adjacent plates; 3, the presence of melanges; 4, the presence of ophiolite zone; 5, the presence of blueschists; 6, the dis-tribution with some regularities of intrusive and extrusive rocks; 7, the distribution of earthquake epicenters; and 8, the unequal polar wanderings of adjacent plates.Judging from the above mentioned principles and examining the geological features of China, we find that, some mountain ranges and territories may be considered as junctures of plate tectonics, those are: 1, the Tsinling structural zone, 2, the eastern coast of Taiwan, 3, the Yalutsangpo Eiver in Tibet, 4, the upper stream of Jinsha River, 5, the Lungmen Mountain and "Kangdian axis" and 6, the northern rim of Chilien Mountain.There are some questions, which need to be further studied. 1, The hypothesis of collision of two continents seems to require certain modifications, because almost all of the subduction zones occur along one or both sides of the geosyncline, and two con-tinents do not come to contact directly with each other. It is fairly the same as along the continental margin, where the oceanic plate moves against the continental plate. 2, Can the ultrabasic rocks intrude into continental crust, or can they only be gene-rated in the mantle? 3, If the ultrabasic rocks appear only in the geosyncline, is it possible to say, that the old massifs, in which ultrabasic rocks are present, such as the Taihwa group of Shensi and the Hwaiyang Shield of Dabie Mountain are geosynclinal metamorphic rocks instead of igneous origin? 4, In northwestern Pacific all of the is-land arcs are with the convex side opposite to the underthrusting plate. Is it possible to be considered as a rule to judge that, which side is the undergoing plate ? It is true, that the subduetion zones on the continent and even along the line between Pacific and South America are not in arc form. 5, According to Dickinson, Mitchell and Eeading there is a gap between the trench and volcanic arcs. In China, so far we know, the intrusive bodies are always directly in contact with the subduction zone, with only the Taiwan Strait as an exception. 6, Sometimes there are granite or granodiorite intrusions to be found behind the subduction zone. Is there another subduction zone behind the former one, or were there igneous activities during the folding of geosyn-cline as indicated .by the classical geotectonic theory ? 7, Except in the eastern provinces of China, where the volcanic rocks are wide-spread, in central and western China very rare volcanic rocks have been found along the margin of overriding plate. Whether the volcanic rocks were eroded away on the magma did not rise to the earth surface at all, is still a question.