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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Structure, composition and age of the small islands of Santa Luzia, Branco and Raso (Cape Verde Archipelago)
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Structure, composition and age of the small islands of Santa Luzia, Branco and Raso (Cape Verde Archipelago)

机译：圣卢西亚，布兰科和拉索（佛得角群岛）小岛的结构，组成和年龄

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The northern alignment of Cape Verde Archipelago contains three small islands in its central sector: Santa Luzia, Branco and Raso on which there is very scarce geological, petrological or geochronological information available. The three islands along with the island of Sao Vicente arise on a continuous underwater relief less than 50 m deep and about 70 km long that formed from separate volcanic edifices. The southernmost island, Raso is formed by accumulation of several tens of lava flows and some remaining strombolian cones. An erosion surface covered by sediments allows the separation of two different episodes of growth: the lower one older than 2 Ma, and the upper one between 0.9 and 1.2 Ma. The smaller island of Branco is the remnant of a large stratovolcano about 6 km in radius, 1000 m of altitude and between 5 and 6 Ma in age. Santa Luzia, the northernmost and largest island of this particular group is essentially a remaining rift zone between 4 and 7 Ma old, at least 600 m high, about 10 km long and 7 km wide. The SE extreme of the island is occupied by rocks of an older partially submarine stage of growth which, also include gabbroic intrusions crossed by a dense network of dikes whose age may be estimated in 8 Ma or more. On the contrary, the NW end shows the only remains of late post-erosion activity that is of much less volumetric importance and it has been dated between 0.8 and 1.4 Ma.
机译：佛得角群岛的北部路线在其中心区域包含三个小岛：圣卢西亚（Santa Luzia），布兰科（Branco）和拉索（Raso），在这些岛上可获取的地质，岩石学或年代学信息非常稀少。这三个岛屿与圣维森特岛一起位于一个连续的水下浮雕上，该浮雕深度小于50 m，长约70 km，由单独的火山大厦形成。拉索岛是最南端的岛屿，是由数十个熔岩流和一些剩余的Strombolian锥堆积而成的。沉积物覆盖的侵蚀面可以分离出两个不同的生长阶段：较低的一个年龄大于2 Ma，而较高的一个则介于0.9和1.2 Ma之间。较小的布兰科岛是一座大型平流火山的遗迹，半径约6公里，海拔1000 m，年龄在5至6 Ma之间。圣卢西亚（Santa Luzia）是这一特殊群体中最北端和最大的岛屿，本质上是一个残存的裂谷带，年龄在4至7 Ma之间，高至少600 m，长约10 km，宽7 km。岛上的SE极地被部分海底生长较旧的岩石所占据，其中还包括由密集的堤防网络穿越的辉长岩侵入体，其年龄估计在8 Ma或以上。相反，西北端显示出后期侵蚀后活动的唯一遗留物，其体积重要性要低得多，其日期在0.8至1.4 Ma之间。

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