The Recent volcanology of Terceira, Azores
The Recent volcanology of Terceira, Azores
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亚速尔群岛特塞拉岛的最新火山学
DOI：
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发表时间：
1976
影响因子：
2.7
通讯作者：
S. Self
中科院分区：
文献类型：
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作者：
S. Self
作为一个海洋岛屿，特塞拉显示了大量的熔岩和火山碎屑岩，并以大量产生过碱性盐岩而闻名。四座火山组成了这个岛；三座火山同时由基性岩石和盐岩组成，一座火山只露出盐岩。自从该岛出现以来，就出现了成分上的双峰岩石群。特尔塞拉群上部100多次喷发的产物已被识别。这些岩石包括火成岩、浮石陨落沉积、盐化熔岩喷出、闪锌矿沉积、玄武岩熔岩流和滨海玄武岩凝灰岩。玄武岩活动集中在一条裂隙带上，该裂隙带将岛屿从NW向SE斜分，可能是Terceira裂谷的陆上表现。体积研究表明，新地壳沿着这个小的扩张中心积累的速度；在过去的23 000年里，岛上喷发了5.46千米3的新物质，其中超过4千米3是孔雀石-方铅矿的成分。浮石瀑布沉积为次成矿型，具有分散面积小于成矿体、浮石分级倒置和内部层结的特点。浮石矿床是由爆炸性低于其他大西洋岛屿的喷发产生的，这被解释为岩浆气体含量较低。
Terceira shows a great diversity of lavas and pyroclastics for an oceanic island and is noteworthy for voluminous production of peralkaline salic magma. Four volcanoes form the island; three are composed of both basic and salic rocks and one has only salic rocks exposed. Since the emergence of the island a compositionally bimodal population of rocks has been represented. The products of over 100 eruptions in the upper Terceira Group have been recognised. These include ignimbrites, pumice fall deposits, salic lava extrusions, strombolian scoria deposits, basaltic lava flows and littoral (surtseyan) basaltic tuffs. Basaltic activity is concentrated along a fissure zone which bisects the island diagonally from NW to SE and may be the subaerial expression of the Terceira Rift. Volumetric studies show the rate of accumulation of new crust along this small spreading centre; 5.46 km3 of new material has been erupted on the island in the past 23 000 years, of which over 4 km3 is of comendite–pantellerite composition. The pumice fall deposits are of sub-plinian type characterised by smaller dispersal areas than plinian deposits, inverse grading of pumice and internal stratification. The pumice deposits were produced by eruptions of lower explosivity than those which occur on other Atlantic islands, which are interpreted as resulting from lower magmatic gas contents.