长白山天池火山千年大喷发期后火山泥石流沉积特征及其源-汇响应关系  

Characteristics and source-sink response of the Lahar deposits in Changbaishan-Tianchi volcano and adjacent area following the Millennium Eruption

作　　者：王璞珺[1] 许伟东 陈海潮 衣键 王寒非 唐华风[1] 王文华[1] 武成智[4] WANG PuJun;XU WeiDong;CHEN HaiChao;YI Jian;WANG Han Fei;TANG HuaFeng;WANG WenHua;WU ChengZhi(College of Earth Sciences,MOE Key Lab.for Evolution of Past Lfe&Enwironment in NE Asia,Jilin Uniersity,Changchun 130061,China;School of Earth and Enrironment,Unrersity of Canterbury,lam rod,Chrstchurch 8053,New Zealand;Department of Computer Science,Nanjing University,Nanjing 210023,China;Monitoring Station of the Changbaishan.Tionchi Volcanos,Jilin Earthquahe Administration,Antu 133613,China)

机构地区：[1]东北亚生物演化与环境教育部重点实验室(吉林大学),吉林大学地球科学学院,长春130061 [2]坎特伯雷大学地球与环境学院,基督城8053 [3]南京大学计算机科学与技术系,南京210023 [4]长白山天池火山监测站,吉林省地震局,安图133613

出　　处：《岩石学报》2020年第9期2893-2911,共19页Acta Petrologica Sinica

基　　金：吉林省科技厅科技发展计划项目(20170101001JC);国家自然科学基金项目(41472304、41790453、41972313)联合资助。

摘　　要：源于长白山天池地区的火山泥石流沉积可分为粗碎屑岩块(岩屑)泥石流和细碎屑浮岩泥石流,它们沿二道白河和松花江水系搬运的路径为从距天池火山口40km的三合水电站经过丰满大坝(360km)和吉林市(380km)到小白旗屯(450km),形成广泛的沉积区域。这两类火山泥石流的沉积成因有两种解释:一是形成于千年大喷发同期,是由一次性洪水事件搬运和沉积形成的;二是形成于千年大喷发期后经过多次搬运和沉积的产物。两个模式的共同问题是都没有考虑天池当时是否有水及其蓄水过程。后一模式在某种程度上,还回避了导致岩屑与浮岩两类泥石流频繁互层的沉积物源和水动力条件以及二者的转换机制,而这恰恰是关于泥石流沉积成因的基本要素。通过重新研究火山泥石流经典剖面(位于天池西北57.73km的水田村),作者发现本区火山泥石流沉积存在明显的物源剥蚀区与沉积堆积区的反剖面关系。即无论是粒径32~500mm的粗碎屑还是0.0625~16mm的细碎屑,成分自下而上(或沉积早期到晚期)呈现规律性变化:剖面下部的碎屑成分以浮岩为主(浮岩在物源区位于顶部),向上粗面岩和玄武岩明显增多(在源区它们位于浮岩之下),而沉积序列上部的碎屑成分是在物源区处于较深层位的岩脉辉绿岩和基底流纹岩。整个序列碎屑成分的沉积分异特征明显。沉积构造和岩相组合特征显示,该火山泥石流剖面的下部和上部碎屑粒度细、分选较好、成层性好、水平状层理发育,主要表现为环境较为稳定的以地面径流为主的河流相和末端扇相背景沉积;中部粒度粗、成层性差、主要表现为突发性洪水作用导致的洪积相事件沉积。沉积序列中频繁出现的冲刷面构造指示水流强度曾出现周期性的快速增加。自下而上冲刷面规模由小变大再变小,指示水流强度由弱变强再变弱。为了探讨天池的积水条Lahars generated from the Tianchi crater lake in the Changbai Mountain area include coarse-grained lithic and finegrained pumice deposits. They were transported along the Erdaobaihe River and Songhua River systems from the nearest Sanhe waterpower station being 40 km away from the crater,through Fengman Dam( 360 km) and Jilin City( 380 km) to the far most Xiaobaiqitun 450 km away from the crater lake. All the way along the lahar flows left behind widespread lahar deposits in the region.There are two explanations concerning formation of these volcanic lahar deposits. Firstly,they were formed by a sudden release of the giant lake water caused by dam break during the Millennium Eruption( ME) which occurred about CE 946 ± 3 in the ChangbaishanTianchi volcano,and all the pyroclastic materials were transported and deposited by the same off flood event. The second is that the lithic and pumice lahar deposits were separately formed by two episodes of transportation and deposition events after the ME. The question with the two models is that the water was not considered,i. e. whether or not there was any water in the crater lake at that time during the ME and how could the water accumulate. And more so,The latter scheme potentially avoided,to some extent,the sediment source,hydrodynamic condition and the mechanism on the transition that led to frequent inter bedding of the lithic and pumice lahars,those are,of course,important factors concerning depositional process of the lahars. We challenge the above explanations and researched in detail the well-known examples of the so-called classic lahar successions outcropped in the Shuitian Village which is57. 73 km northwest from the Tianchi crater. We found that there are steady state of inversely back-striping relationship between the source denudation area and the sedimentary accumulation process. That is to say,both coarse debris in diameter 32 ~ 500 mm and fine debris of 0. 0625 ~ 16 mm,their components change in upward sequence is as follows. The fragments in the lower pa

关 键 词：长白山火山千年大喷发 火山岩渗透率 天池积水数学模拟 岩屑和浮岩泥石流 源-汇响应 

分 类 号：P317[天文地球—固体地球物理学]