长白山天池火山千年大喷发火山碎屑流堆积相特征  

Facies variations in the pyroclastic density currents( PDCs) produced by the Millennium Eruption of the Changbaishan Tianchi volcano,NE China

作　　者：衣健 王璞珺[1,2] 单玄龙 CARNIEL Roberto[3] 武成智 王寒非[5] 孙松 郭剑南 YI Jian;WANG PuJun;SHAN XuanLong;CARNIEL Roberto;WU ChenZhi;WANG HanFei;SUN Song;GUO JianNan(Key Laboratory for Evolution of Past Life and Environment in Northeast Asia,Ministry of Education,Jilin University,Changchun 130026,China;College of Earth Sciences,Jilin University,Changchun 130061,China;Dipartimento Politecnico di Ingegneriae Architettura,University of Udine,Udine,Friuli 33100,Italy;Changbai Mountain Tianchi Volcano Observatory,Antu 133613,China;Department of Geological Sciences,University of Canterbury,Christchurch,Private Bag 4800,New Zealand)

机构地区：[1]吉林大学,东北亚生物演化与环境教育部重点实验室,长春130026 [2]吉林大学地球科学学院,长春130061 [3]Dipartimento Politecnico di Ingegneriae Architettura,University of Udine,Udine 33100 [4]长白山天池火山监测站,安图133613 [5]Department of Geological Sciences,University of Canterbury,Christchurch 4800

出　　处：《岩石学报》2020年第11期3346-3362,共17页Acta Petrologica Sinica

基　　金：国家自然科学基金重大项目(41790453);国家自然科学基金面上项目(41972313);吉林省科技发展计划主题引导项目(20170101001JC);吉林大学地热资源开发技术与装备教育部工程研究中心联合资助。

摘　　要：发生于公元946年的长白山天池火山千年大喷发(Millennium Eruption,ME)形成的火山碎屑堆积物体积高达100~172km3,并可分为大规模的ME-Ⅰ和小规模的ME-Ⅱ两个喷发阶段。通过对围绕长白山天池火山53个典型露头剖面进行火山地质测量(单元构成、垂向堆积序列和堆积特征),结合筛析法粒度分析、偏光显微镜成分分析,刻画了长白山千年大喷发火山碎屑流堆积物特征,探讨了相和亚相划分,并建立了火山碎屑流搬运和堆积模式。根据火山碎屑的堆积特征,将长白山千年大喷发火山碎屑流堆积分为峡谷充填火山碎屑流相(包括块状峡谷充填亚相和层状峡谷充填亚相)和火山碎屑流冲击扇相(包括扇头亚相和扇体亚相)等两相四亚相。峡谷充填火山碎屑流相主要发育在天池火山锥体周缘距离喷发中心8~23km左右范围内(坡度在15°~60°之间)的火山U型谷中;火山碎屑流冲积扇相主要发育在距离喷发中心23~45km左右范围内,地形相对平缓的熔岩台地处(坡度在5°~15°之间),火山碎屑流的搬运不受地形限制,一般形成较大纵横比扇状堆积。块状峡谷充填亚相和扇体亚相以块状混杂堆积为主要特征,而层状峡谷充填亚相和扇头亚相则以多火山碎屑流单元垂向叠加为主要特征。多单元叠加现象是由搬运过程中火山碎屑流单元发生分离增生作用形成。根据火山碎屑流的最大分布范围和厚度,如果再次发生与长白山千年大喷发类似规模的普林尼式喷发,至少距长白山天池火山喷发中心45km范围内具有巨大的火山碎屑流灾害风险。该研究有利于进一步深入认识长白山千年大喷发火山碎屑流堆积物的空间分布特征和相变规律,对火山碎屑喷发灾害的预防具有指导作用。The Plinian Millennium Eruption( ME) of the Changbaishan Tianchi volcano in 946 AD generated a total tephra volume of 100 ~ 172 km3 produced by a large scale of ME-Ⅰ eruption and a small scale of ME-Ⅱ eruption. This study examines the facies variations in the pyroclastic density currents( PDCs) emplaces that were produced by the ME based on observations of the depositional units,vertical sequences in 53 outcrops. Grain-size and composition analysis using standard dry sieving techniques and microscope observations of thin sections in the laboratory provided detailed information for the PDCs emplacement. The ME PDCs deposits of the Changbaishan Tianchi volcano can be divided into two facies: canyon filling PDCs facies and fan-shaped PDCs facies. The canyon filling PDCs facies are mainly developed in the circumference area of the volcanic cone( 8 ~ 23 km from the crater and slope between15° to 60°) which are mainly restricted by the volcanic valleys,and can further be divided into massive canyon filling and layer canyon filling sub-facies. In contrast,fan-shaped PDCs facies are mainly distributed in the areas between 23 ~ 45 km from the crater which present relatively gentle slope between 5° to 15°. In this area,the fan-shaped PDCs were not restricted by the topography and generally formed fan-shaped emplacements with a large aspect ratio. Fan-shaped PDCs can also be divided into fan head and fan body sub-facies.The vertical stacked multiple PDCs units occurred in both layer canyon filling and fan head sub-facies,which can be attributed to the separation and proliferation of flow units in the process of PDCs transport. According to the maximum distribution range and the thickness of the ME PDCs,in case of another Plinian eruption like ME,the area within at least 45 km from the eruption center has a huge risk of PDCs disaster. This study is helpful to understand the spatial distribution of the PDCs emplacement in the Changbaishan Tianchi volcano,in order to mitigate the potential disastrous consequences of a

关 键 词：长白山天池火山 千年大喷发 火山碎屑流堆积 相模式 火山灾害 

分 类 号：P317[天文地球—固体地球物理学]