西南极利文斯顿岛火山岩地质

THE VOLCANIC GEOLOGY OF LIVINGSTON ISLAND, WEST ANTARCTICA:A SUMMARY

本文综合近年研究中新获得的资料和证据，对利文斯顿岛火山岩的地质特征和火山作用特点作了综合性的介绍。百耳斯建造是该岛最老的火山岩地层，由晚侏罗世至早白垩世生成的玄武岩、玄武安山岩质熔岩和火山碎屑岩、集块岩以及泥岩、页岩等组成，分布在岛西部的百耳斯半岛。中白垩世的鲍勒斯山组主要出露在岛的中部，是由安山岩质熔岩和火山碎屑岩夹层组成的一套蚀变火山岩系。汉那角剖面的火山碎屑岩和熔岩及史莱夫角的橄榄玄武岩均具有中白垩世的年龄。晚白垩世火山活动的产物以粗玄岩为代表，集中出露在西多斯角一带。伴随着火山活动，始新世英云闪长岩侵入白垩系火山岩地层。更新世至现代则有依诺特角组橄榄玄武岩在岛的东北部产出。上述火山活动随时间演进而自北西向南东不断迁移的特点，与整个南设得兰群岛火山作用的发展趋势相符。岩石化学和地球化学资料表明，百耳斯半岛熔岩、史莱夫角的橄榄玄武岩和西多斯角的粗玄岩等白垩纪火山岩基本属于钙碱性岩系并且具有低钾低镁的特点。早第三纪的英云闪长岩继承了橄榄玄武岩和粗玄岩的成分特点，同是南设得兰群岛岩浆弧中生代－新生代火山作用的产物，在钙碱性岩系岩浆演化的晚期生成。而鲍勒斯山组的熔岩和汉那角的熔岩表现出岩相学和岩石化学性质上的?

This paper give the outline of the volcanic geology and volcanism of Livingston Island,which is based mainly on the new data and new evidences gotten in recent years investigation and researches. The oldest volcanic stratigraphical unit is named Byres Formation,which consists of Late Jurassic to Early Cretaceous basalt,basaltic andesite lava,volcaniclastic,agglomerates and mudstone,siltstone outcropped at Byers Peninsula,the northwest part of Livingston Island. The Mount Bowles Formation of Cretaceous age is an altered volcanic strata,outcropped in the central part of Livingston Island and composed largely of andesitic lava with interbedded pyroclastic rocks. Both the interlayered volcaniclastic rock and lava at Hannah Point and the olivine basalt at Cape Shirreff have the same Middle Cretaceous ages. Dolerite is accumulated at Siddons Point which represents the typical products of Late Cretaceous volcanism. Combining with volcanic activities,Eocene hypabyssal rocks,tonalite,intruded in Cretaceous volcanic strata. Quaternary olivine basalt of Edinburgh Hill Formation occurred in the northern part of island. The spatial distribution of volcanic rocks and the migration of volcanic activities in Livingston Island with time is basically corresponded to that in South Shetland Islands. Petrographical,petrochemical and geochemical data show that the lavas of Byers Peninsula and Cape Shirreff and the dolerite at Siddons Point belong to calc alkaline series and with the characters of lower potassium and magnesium. The Early Tertiary tonalite,caring out the compositional features of olivine basalt and dolerite and being the product of Cenozoic volcanism in the South Shetland magma arc was formed at the late evolution stage of calc alkaline magma. The lavas of Mount Bowles Formation and from Hannah Point are distinguishable both in petrography and petrochemistry from that of other places,the presence of which is related not only to the arc volcanism but also to the distinctive tectonic setting where they formed. Pleistocene to Recent olivine basalt was derived from a primary magma,and the volcanism might be controlled by Late Cenozoic extensional or transtensional tectonics.