长白山天池火山主断裂活动与热液蚀变带
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摘要
在野外考察中发现 ,天池破火山口内壁同一层位不同段的近水平向红褐色、砖红色热液蚀变带顶界面有明显高差热液蚀变顶界面 ,北段 (靠近天文峰 )比南段 (朝鲜境内靠近将军峰 )高出约 110m。热液蚀变带顶界面可作为判断构造运动的标志面。北段与南段顶界面的高差 ,反映了自热液蚀变以来 ,天池火山北东向主断裂六道沟 -天池 -甑峰山断裂北西盘的抬升幅度大于南东盘 ,这可能是天池北西部较南东部地形坡度更陡、水系更发育的内在原因。北西向主断裂———白山镇 -天池 -金策断裂北东盘的抬升幅度大于南西盘。由热液蚀变和古风化壳特征观察到的北东向主断裂的近期垂向活动速率大于北西向主断裂的活动速率。这两条在天池交叉的主断裂将天池火山切割成 4个块体 ,它们的抬升幅度从大到小依次为北、西、东、南块体。北块体抬升幅度最大 ,这与深地震测深、大地电磁探测等得出的天池北部岩浆囊较浅的结果有较好的对应关系和一定的成因联系。
It is discovered in a field survey that the elevation of nearly horizontal top planes of brown and red hydrothermal alteration zones are varied obviously at different segments on the same layer of caldera wall, and that the elevation at the northern segment next to the Tianwen Peak is about 110 m higher than one at the southern segment next to the Jiangjun Peak in Korea. The authors show here that the top plane of hydrothermal alteration zone can be treated as a mark to assess tectonic activity. The elevation difference of the top planes of hydrothermal alteration in the two segments shows that, from generation of hydrothermal alteration up to now, the total uplift height in the NW block is bigger than in the SE block along the main fault in NE trend, the Liudaogou-Tianchi-Zenfengshan fault that passes between the two segments. It also explained why the topography in the northwestern side of Tianchi is steeper and with more river channels than in the southeastern side of Tianchi. The uplift height in the NE block is bigger than in the SW block along the main fault in NW trend,the Baishanzhen-Tianchi-Jince fault. It seems that the recent activity rate of the main fault in NE trend is bigger than that of the main fault with NW trend by observing hydrothermal alteration and paleosoil. The two main faults that cross at Tianchi cut the Tianchi volcano into 4 blocks, that is, north block, west block, east block and south block in order of successively decreasing of uplift value respectively. The uplift value of north block that is obtained by analyzing elevation difference of top planes of hydrothermal alteration is the biggest. Deep seismic sounding and magnetotelluric survey show that there are low velocity and low resistivity bodies that may be shallower magma chambers in the north part of Tianchi. All of these results are in consistent with each other and there may be some connections of causes.
It is discovered in a field survey that the elevation of nearly horizontal top planes of brown and red hydrothermal alteration zones are varied obviously at different segments on the same layer of caldera wall, and that the elevation at the northern segment next to the Tianwen Peak is about 110 m higher than one at the southern segment next to the Jiangjun Peak in Korea. The authors show here that the top plane of hydrothermal alteration zone can be treated as a mark to assess tectonic activity. The elevation difference of the top planes of hydrothermal alteration in the two segments shows that, from generation of hydrothermal alteration up to now, the total uplift height in the NW block is bigger than in the SE block along the main fault in NE trend, the Liudaogou-Tianchi-Zenfengshan fault that passes between the two segments. It also explained why the topography in the northwestern side of Tianchi is steeper and with more river channels than in the southeastern side of Tianchi. The uplift height in the NE block is bigger than in the SW block along the main fault in NW trend,the Baishanzhen-Tianchi-Jince fault. It seems that the recent activity rate of the main fault in NE trend is bigger than that of the main fault with NW trend by observing hydrothermal alteration and paleosoil. The two main faults that cross at Tianchi cut the Tianchi volcano into 4 blocks, that is, north block, west block, east block and south block in order of successively decreasing of uplift value respectively. The uplift value of north block that is obtained by analyzing elevation difference of top planes of hydrothermal alteration is the biggest. Deep seismic sounding and magnetotelluric survey show that there are low velocity and low resistivity bodies that may be shallower magma chambers in the north part of Tianchi. All of these results are in consistent with each other and there may be some connections of causes.
引文
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丁国瑜主编,1991,中国岩石圈动力学概论,142～153,北京,地震出版社。
金伯禄、张希有,1994,长白山天池火山地质研究,49～74,长春:东北朝鲜民族教育出版社。
刘若新、魏海泉、李继泰等,1995,刘若新主编,火山作用与人类环境,1～13,北京:地震出版社。
刘若新、魏海泉、李继泰等,1998,长白山天池火山近代喷发,北京:科学出版社。
刘嘉麒,1989,论中国东北大陆裂谷系的形成与演化,地质科学,(3),209～216。
单新建、陈国光、叶 洪等,2000,利用数字遥感图像研究长白山天池火山近代喷发规模,地震地质,22(2),187～194。
汤 吉、邓前辉、赵国泽等,2001,长白山于池火山区电性结构和岩浆系统,地震地质,23(2),191～200。
魏海泉、刘若新、樊祺诚等,1999,长白山天池火山-多成因中央式火山,地质论评,45(增刊),257～262。
张先康、张成科、赵金仁等,200,长白山天池火山区岩浆系统深部结构的深地震测深研究,地震学报,24(2),135～143。
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