Geological correlation of southwest Japan and Korean Peninsula-tectonics for spreading of active continental margin-.

该项目的题目是日本西南部和朝鲜半岛的地质对比-活动大陆边缘扩张的构造-。项目的一些成员访问了Yongwol地区，对Yongwol煤田的Pamuchi混杂岩单元进行了地质检查，并揭示了以下地质事件; 1）晚二叠世帕穆奇古海的伸展发育，表现为中二叠世晚期至晚二叠世早期硅质岩与下二叠世泻湖相灰岩互层，2）帕穆奇盆地在晚二叠世至三叠纪的闭合，导致帕穆奇混杂岩单元的形成。后一个事件与晚二叠世舞鹤和日本西南部的超丹波地体的事件相吻合，后者是根据砂岩的岩石学数据详细研究的。该项目的其他成员留在韩国东南部，对白垩纪-白垩纪火成岩和沉积岩进行野外工作。与日本西南部山阴带的花岗岩类岩石相似，韩国东南部的大多数白垩纪-古近纪侵入岩为I型磁铁矿系列。这些岩石显示出较低的初始Sr同位素比在山阴带，日本西南部。两个代表性岩体的Rb-Sr全岩等时线年龄分别为53和58Ma。这些数据可能表明，韩国东南部大部分花岗岩类岩石的时代是古近纪，其岩浆来源与山阴带下的岩浆来源相似。全岩和角闪石K-Ar年龄测定结果表明，中新世火山岩的年龄与山阴地区相似，但韩国东南部火山活动最强烈的时期略早于日本西南部。与日本西南部的山阴地区不同，韩国东南部的碱性岩系火山活动始于白垩纪。这是考虑伴随日本海张开的大陆边缘岩浆和构造演化的一个重要因素。

The title of the project is geological correlation of southwest Japan and Korean Peninsula-tectonics for spreading of active continental margin-. Some members of the project visited Yongwol area and examined geologically the Pamuchi melange unit in the Yongwol coal field, and revealed following geologic events ; 1) extensional development of the Late Permian Pamuchi paleo-sea represented by the occurrence of the late Middle to early Late Permian siliceous rocks interbedded with the Lower Permian lagoonal facies limestones, 2) Closure of the Pamuchi basin in Latest Permian to Triassic which resulted to the formation of the Pamuchi melange unit. The latter event coincides significantly to that of the Late Permian Maizuru and Ultra-Tanba Terrains of SW Japan which was investigated in detail on the basis of petrographical data of sandstones. Other members of the project stayed in southeastern part of Korea to do field work for Cretaceous-Miocne igneous and sedimentary rocks. Similar to the granitoid rocks in the San'in Zone, SW Japan, most Cretaceous-Paleogene intrusive rocks in SE Korea are I-type magnetite-series. These rocks show low initial Sr isotope ratios comparable to those in the San'in Belt, SW Japan. Two repesentative plutons show Rb-Sr whole rock isochron ages of 53 and 58 Ma. These data may suggest that the most granitoid rocks in SE Korea are Paleogene in age, and their magmas were derived from similar source materials to those beneath the San'in Belt. Whole rock and hornblende K-Ar age determination revealed that Miocene volcanic rocks have similar ages to those in the San'in district, but the period of the most intensive volcanism was slightly older in SE Korea than in SW Japan. In contrast with San'in district, southwest Japan, volcanism of alkaline rock series initiated in the Cretaceous in SE Korea. This is an important factor to consider magmatic and tectonic evolution of the continental margin accompanied by the opening of Japan Sea.