长白山天池火山晚更新世以来岩浆房系统的压力探讨  

Analysis to the pressure condition of magmatic system from the Late Pleistocene Changbaishan-Tianchi volcanism

作　　者：周秉锐潘波颜丽丽徐丹 武成智 ZHOU BingRui;PAN Bo;YAN LiLi;XU Dan;WU ChengZhi(Jilin Changbaishan Volcano National Observation and Research Station,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Changbaishan Tianchi Volcano Observatory,Antu 133613,China)

机构地区：[1]中国地震局地质研究所,吉林长白山火山国家野外科学观测研究站,北京100029 [2]吉林省长白山天池火山监测站,安图133613

出　　处：《岩石学报》2024年第7期2075-2086,共12页Acta Petrologica Sinica

基　　金：吉林长白山火山国家野外科学观测研究站项目(NORSCBS23-01)资助。

摘　　要：长白山天池火山是一座大型的复合式活火山,由于其曾剧烈的喷发活动(946~947AD)和2002-2006年的扰动事件而备受瞩目。自晚更新世以来,天池火山有过多次剧烈的爆炸式喷发活动,其岩浆主要为高分异的碱流质与粗面质岩浆,SiO_(2)>65%。地球物理探测表明天池火山地下在浅部地壳存在岩浆房,但却未能对历史喷发活动的岩浆系统进行约束。本文利用晚更新世以来喷发物的电子探针数据,运用Qz-Ab-Or系统投图、单斜辉石机器学习压力计以及rhyolite-MELTS压力计对各期喷发的岩浆驻存压力条件进行计算,认为天文峰期(TWF)碱流岩压力约246~444MPa、气象站期(QXZ)碱流岩压力约184~344MPa、千年大喷发(ME-I)碱流岩压力约162~314MPa,千年大喷发(ME-II)粗面岩压力约438~540MPa。通过压力与深度换算后发现上述喷发岩浆贮存位置均对应中上地壳深度的岩浆房,并且三期碱流岩压力随喷发时间逐渐降低,暗示天池碱流质岩浆房在万年尺度内逐渐向浅部地壳演化的趋势;而粗面质岩浆可能来自另一个更深的岩浆房。该发现将有助于提高对天池火山岩浆房系统演化的认识,并为火山监测数据解释和灾害预警等工作提供依据。Changbaishan-Tianchi(CBS-TC)is a giant composite active volcano,which is well-known by its intense eruptions(946~947AD)and unrest during 2002-2006.Since Late Pleistocene,CBS-TC has experienced several intense eruptions of highly differentiated comenditic and trachytic magma with SiO_(2)>65%.According to geophysical research,there are shallow crustal magma chambers below Tianchi.However,the magmatic system of the historical eruptions remains unconstrained.In this paper,massive glass compositions from electron microprobe analysis are applied to constrain the detailed pressure condition of the Tianchi magma storages by using the Qz-Ab-Or trinary projection,the Clinopyroxene Machine Learning geobarometer and the rhyolite-MELTS geobarometers.Among the Late Pleistocene volcanic products,the Tianwenfeng(TWF)eruption,the Qixiangzhan(QXZ)eruption,the Millennium comenditic eruption(ME-I)and the Millennium trachytic eruption(ME-II)yield pressure ranges of 246~444MPa,184~344MPa,162~314MPa and 438~540MPa,respectively.After pressure-depth transformation,the four episodes of silicic magma are generally supposed to be stored in upper to middle crust level.It is worth-noting that the pressure ranges of TWF,QXZ and ME-I comenditic magma have a trend of descent with eruption time,which might reveal the evolution process of an identical comenditic magma chamber to a shallower level in a 10-thousand-year timescale;while the trachytic magma chamber generating the ME-II eruption is located in a lower layer beneath the former one.The new findings derived from our work are helpful in understanding the evolution of the Tianchi magma chamber system,explaining volcanic monitoring data and forecasting of volcanic hazards.

关 键 词：长白山天池火山 地质压力计 高分异岩浆 岩浆贮存压力 岩浆演化 岩浆房系统 

分 类 号：P317[天文地球—固体地球物理学] P588.11[天文地球—地球物理学]