广东硇洲岛火山地质与射气岩浆喷发

Volcanic geology and phreato-magmatic eruption of Naozhou Island in Guangdong

硇洲岛位于雷州半岛东部海域,该岛最具特征的火山喷发形式是发生在其东南部那晏湾的射气岩浆喷发,这也是揭开硇洲岛火山喷发历史、环境和过程的窗口。本文从硇洲岛火山地质、射气岩浆喷发基浪堆积物粒度分析、有机质稳定同位素分析、电子自旋共振(ESR)测年等方法入手,分析讨论火山活动历史和射气岩浆喷发特征并追溯其基浪堆积物原始沉积环境。研究结果表明,早更新世强烈的岩浆溢流完成了岛屿的初始建造,之后硇洲岛高出海平面以上停止接受沉积;中更新世发生了两幕中小规模的火山活动,分别为距今约588ka的射气岩浆喷发和距今448ka的岩浆溢流;晚更新世在存亮湾附近可能发生了弱爆炸式火山喷发,自此硇洲岛的火山活动结束。

Naozhou Island is located in the eastern sea of the Leizhou Peninsula,and the most characteristic form of volcanic eruption on the island is the phreato-magmatic eruption that occurred in the Nayan Bay,southeast of the island,which is a window to unraveling the history,environment,and process of volcanic eruption series on Naozhou Island.In this paper,we analyze and discuss the history of volcanic activity and the characteristics of phreato-magmatic eruption and trace the source of its base surge deposits,starting from the volcanic geology of Naozhou Island,the particle size analysis of base surge deposits from phreato-magmatic eruption,the stable isotope analysis of the organic matter,and the electron spin resonance(ESR)dating methods.The results show that the initial construction of the island was completed by a strong magma overflow in the Early Pleistocene,after which Naozhou Island ceased to receive deposits above sea level;two episodes of small to medium scale volcanic events occurred in the Middle Pleistocene,a phreato-magmatic eruption of about 588ka before present and a magma overflow of about 448ka before present.A weakly explosive eruption may have occurred in the Late Pleistocene in the vicinity of Cunliang Bay,and the volcanic activity on the island has been over since Naozhou Island was established.The island s volcanic activity has ended since then.