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随着沿南极洲西部边缘俯冲作用的休止,中生代钙碱性火山活动至新生代逐渐让位于与引张状态相伴随的富碱火山作用。钙碱性火山作用在南设得兰群岛,一直持续到第三纪,而在南桑维奇群岛甚至开始出现于第四纪,虽然本组的大部分上新世-全新世火山作用产物具有岛弧拉斑玄武岩亲缘性。 罗斯海和玛丽伯德地的新生代火山岩通常为极不饱和玻基碧玄岩,碱性玄武岩和响岩。相比之下,南极半岛偏北部及其向海岛屿的大部分火山岩则呈弱碱性或过渡性。然而,位于南极半岛最北部的一个最年幼火山——波列特(Paulet)岛的火山岩,较其上新世前期岩石明显地更富碱。以强烈富钠质分异岩为特征的迪塞普申岛可能与沿布兰斯菲尔德海峡的残余的弧后引张有关。
Following the subduction of the western edge of Antarctica, the Mesozoic calc-alkaline volcanic activity gradually gave way to Cenozoic alkali-rich volcanic activity accompanied by the tension state. The calc-alkaline volcanoes play a role in the South Shetland Islands until the Tertiary, and even started to appear in the Quaternary in the South Sandwich Islands. Although most of the Pliocene-Holocene volcanism products in this group had islands Arc tholei basalt affinity. The Cenozoic volcanic rocks of the Rose Sea and Marybird are usually extremely unsaturated Bikonite, alkaline basalts and ring rocks. In contrast, most of the volcanic rocks in the north of the Antarctic Peninsula and its islands toward the sea are weakly alkaline or transitional. However, volcanic rocks on the island of Paulet, one of the youngest volcanoes in the northernmost part of the Antarctic Peninsula, are significantly more alkali-rich than their pre-Pliocene rocks. Decepticon island, which is characterized by a strong accumulation of sodium-rich rocks, may be related to the residual posterior-arc extension along the Bransfield Strait.