西南极利文斯顿岛汉那角火山岩地质及火山活动

本文以野外地质资料为基础，并结合岩相学特征，论述了西南极南设得兰群岛利文斯顿岛汉那角（ＨａｎｎａｈＰｏｉｎｔ）火山岩地层及岩石的基本特征，初步讨论了该地火山活动过程。该地互层状产出的火山角砾岩和熔岩，为南极半岛火山岩组的一部分。剖面上出露的三个火山岩地层旋回分别是三期火山作用的产物。第一、二旋回岩层产状的变化记录了火山作用过程中的一次活动间歇。第一旋回的英安岩和含有流纹岩质熔岩夹层的凝灰角砾岩仅为第一期火山活动末的产物；第二旋回为三次较强喷发活动的产物，从安山岩质火山碎屑岩为主，经玄武岩－安山岩质熔岩为主，过渡为含有安山岩或流纹岩质熔浆团的火山角砾岩。第三期火山活动可能更强烈，大面积分布的厚层玄武质熔岩无论从产状上还是在岩石学特征方面都有别于其他旋回。火山岩地层总体产状稳定，平缓地倾向北西，表明该区未受到过明显的构造影响，火山活动中心可能有逐步向北西迁移的趋势，与南设得兰群岛岩浆弧演变趋势一致。次火山岩主要为玄武岩质小岩墙，集中在第二旋回底部。第一、二旋回接触界线两侧凝灰角砾岩表现较强的沸石化。这些现象说明该接触面附近为一薄弱带，侵入活动和蚀变均较易发生。

GEOLOGY AND VOLCANIC ACTIVITIES IN HANNAH POINT, LIVINGSTON ISLAND, SOUTH SHETLAND ISLANDS, WEST ANTARCTICA

Based on detailed geological mapping and petrographical study the volcanic sequence and volcanic activities at Hannah Point, Livingston Island have been described and discussed. As a part of Antarctic Peninsula Volcanic Group, the measured cross-section consisting of interbedded volcaniclastic rocks and lavas could be divided into three volcanic cycles formed in three different stages of volcanism. The unconformity between cycle 1 and 2 recorded a relatively long intermission of eruptions between the first two stages of volcanism. The dacitic to rhyolitic lava and tuff-breccias of the first cycle were formed at the end phase of eruption. The second stage included three intermittent eruptive activities and the erupted products evaluated from mainly andesitic pyroclastic, through predominant basaltic-andesitic lava,to andesitic or rhyolitic melted ash lapillistone. The volcanism in the third stage might be more intense and differ greatly from that in other stages both in geology and petrography. Stable and gentle dipping of the volcanic strata suggests that there was no obvious tectonic effect and the eruptive centers might gradually migrates northeastwards. The facts that dykes and sills were concentrated in the lower part of the second stage volcanism, and that strong zeolitization was developed in the tuffaceous rocks at the two sides of unconformity suggest a weaker zone near the contact betweet two cycles, where structural activity and alteration were easily occurred.