摘要
琼北地区晚更新世射气岩浆喷发形成众多的低平火山口 ,出露典型的基浪堆积物 ,在火口垣露头上可清晰地观察到大型低角度交错层理、板状层理和波状层理以及远源相的球粒状增生火山砾。玄武质岩浆在上升过程中遇水爆炸形成低平火山口及基浪堆积 ,为认识琼北地区新生代以来的火山活动规律和琼北 -雷南地区的构造环境 ,以及未来火山灾害预测提供了重要的依据。
This study focuses on the northern Hainan volcanoes. The volcanic region belongs to the southern part of the Leiqiong depression, which experienced extensive subsidence during the Cenozoic. The surface of this area is covered with basalts and Quaternary sediments. Cenozoic volcanic rocks cover about 12 percent of the whole Hainan Island. In general, NW trending fractures have controlled the volcanic activities in this area since Holocene. According to the published data, the volcanic activity in northern Hainan Island since Late Pleistocene was divided into Daotang period (Late Pleistocene) and Shishan period (Holocene). Our field investigation on volcanic activities has revealed that after the effusive eruption in early Pleistocene, considerable scale phreatomagmatic eruptions occurred during late Pleistocene, and then the typical central eruptions occurred at the beginning of Holocene. Late Pleistocene is the most active period of phreatomagmatic eruptions in Northern Hainan Island, while phreatomagmatic eruptions were the important eruptive character before the Holocene volcanic activity in this area. Phreatomagmatic eruptions may produce base surges, and base surges are usually accompanied with 'maar'. Maar is originally the name that the local people of Rhine, Germany called the lake and swamp filled with water in the region. In 1921, Steininger, a Germanic scientist, defined maar as a kind of volcanoes when he studied a Quaternary small round crater at Eifel, western Germany. Chinese scholar Liu Jiaqi had researched some maars within Chinese territory during the past several years, he pointed out that maar is something caused by phreatomagmatic eruptions, and its shape is similar to some other volcanic apparatus. Maar is a kind of familiar volcanic physiognomy besides volcanic cone. Some typical maars concentrate in Longgang (Northeast China) and Leiqiong (South China) regions, which are Cenozoic volcanic area. In Longgang region, there are eight maars caused by phreatomagmatic eruptions. Local peopl
出处
《地震地质》
EI
CSCD
北大核心
2003年第2期289-297,共9页
Seismology and Geology
基金
20 0 0年科技部社会公益项目研究专项资金 (2 0 0 0DIA10 2 0 0 6 )资助
