摘要
水下火山喷发作用机制不同于陆地环境喷发,随着水参与程度的变化,喷发机制趋向复杂。本文以雷琼火山群的湛江硇洲岛作为研究对象,聚焦浅海火山产物的判断依据和水下火山喷发机制。硇洲岛是我国最大的第四纪火山岛,其上的那晏湾剖面保留了完整的火山喷发堆积序列。在那晏湾剖面的凝灰岩中,主要有三类火山成因的大粒径原生碎屑(2-5mm):塑变熔岩碎屑、碎玄玻璃及玄武玻璃,推断为不同程度水-岩浆相互作用的产物,根据水的参与程度大致排序为:碎玄玻璃>玄武玻璃>塑变熔岩碎屑。通过对硇洲岛水-火山作用机制研究,发现水-岩浆混合质量比(Mwater/Mmelt)是控制爆炸强度和火山碎屑粒度的关键因素。火山喷发序列分析表明,硇洲岛的喷发过程总体可分为三期,早期是冰岛苏特塞式喷发的浅水环境蒸汽爆炸与“火喷泉”喷发;中期过渡转为“火喷泉”喷发,伴随陆上的射汽岩浆喷发;最终以岩浆溢流式喷发结束。
The mechanism of submarine eruption is different from that of the inland eruption, whose mechanism becomes highly variable with varying water participation in the volcanism. Herein, we focus on the largest Quaternary volcanic island in China, namely Naozhou Island in Zhanjiang, which is located in the Leiqiong volcanic field, Guangdong Province. This paper aimed to identify the change characteristics of pyroclasts that signify shallow sea underwater eruption, and constrain its eruption mechanism. The costal outcrop sections of Nayanwan in the southeastern Naozhou Island retain a complete volcanic eruption sedimentary sequence. Among the tuffs in it, there are three types of pyroclasts: fluidal clasts, sideromelane and tachylite, which are inferred to be the products of different degrees of water-magma interaction. According to the degree of water participation, the order is as follows: sideromelane>tachylite>fluidal clasts. It is found that the Mwater/Mmeltratio is the key factor to control the explosion intensity and the size of pyroclasts. The analysis of volcanic eruption mechanism shows that it can be divided into three stages in total: the early stage is an Icelandic Surtseyan eruption in a shallow water environment with vapor explosion and eruption;the middle stage turns into a fire-fountain eruption, accompanied by phreatomagmatic eruption on land;and the late stage ended in a magmatic overflow eruption.
作者
王丽竹
赵勇伟
李霓
陈正全
WANG LiZhu;ZHAO YongWei;LI Ni;CHEN ZhengQuan(Department of Geology,Northwest University,Xi an 710069,China;Jilin Changbaishan Volcano National Observation and Research Station,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Key Laboratory of Seismic and Volcanic Hazards,CEA,Beijing 100029,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2023年第3期907-920,共14页
Acta Petrologica Sinica
基金
中国地震局地质研究所中央级公益性科研院所基本科研业务专项(IGCEA1717)
国家自然科学基金项目(42272351、41872255)联合资助。
关键词
浅海火山喷发
水下喷发
火山碎屑
雷琼火山群
湛江硇洲岛
Shallow sea volcanic eruption
Submarine eruption
Pyroclastic
Leiqiong Volcano Group
Naozhou Island
Zhanjiang
