The Qixiangzhan Lava Flow at the Tianchi Volcano:Eruptive Dynamics,Emplacement Mechanism and Implications for the Formation of Long-lived Magmatic Systems Prior to Caldera-forming Eruptions  

作　　者：LI Jiahui SHAN Xuanlong YI Jian WU Chengzhi Ventura GUIDO LIU Pengcheng GUO Jiannan WANG Wei 

机构地区：[1]College of Earth Science,Jilin University,Changchun 130061,China [2]International Center of Future Science,Changchun 130061,China [3]Changbaishan Tianchi Volcano Observatory,Antu,Jilin 133613,China [4]Istituto Nazionale di Geofisica e Vulcanologia,Roma 00143,Italy [5]Istituto per lo Studio degli impatti Antropici e Sostenibilitàin ambiente marino(IAS),Capo Granitola(TP)91021,Italy [6]Tianjin Branch of the China National Offshore Oil Company Ltd.,Tianjin 300452,China

出　　处：《Acta Geologica Sinica(English Edition)》2025年第1期114-125,共12页地质学报(英文版)

基　　金：funded by the National Natural Science Foundation of China(Grant Nos.41972313 and 41790453);the Engineering Research Center of Geothermal Resources Development Technology and Equipment,Ministry of Education,Jilin University。

摘　　要：The 7 ka old Qixiangzhan lava flow(QXZ,Tianchi volcano)represents the last eruptive event before the 946 CE,caldera-forming‘Millennium’eruption(ME).Petrographic,whole rock,mineral composition,Sr-Nd isotopic data on QXZ show that:(a)the lava consists of two components,constituted by comenditic obsidian fragments immersed in a continuous,aphanitic component;(b)both components have the same geochemical and isotopic variations of the ME magma.The QXZ and ME comendites result from fractional crystallization and crustal assimilation processes.The temperature of the QXZ magma was about 790℃ and the depth of the magma reservoir around 7 km,the same values as estimated for ME.QXZ had a viscosity of 10^(5.5)-10^(9) Pa s and a velocity of 3-10 km/yr.The emplacement time was 0.5-1.6yr and the flow rate 0.48-1.50 m^(3)/s.These values lie within the range estimated for other rhyolitic flows worldwide.The QXZ lava originated through a mixed explosive-effusive activity with the obsidian resulting from the ascent of undercooling,degassing and the fragmentation of magma along the conduit walls,whereas the aphanitic component testifies to the less undercooled and segregated flow at the center of the conduit.The QXZ lava demonstrates the extensive history of the ME magma chamber.

关 键 词：lava flow rhyolitic volcanism eruptive mechanism long-lived magmatic systems Tianchi volcano Qixiangzhan Formation 

分 类 号：P317.3[天文地球—固体地球物理学]