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首页> 外文期刊>Journal of Volcanology and Geothermal Research >Eruption history and petrogenesis of rocks from Nyos volcano (NW Cameroon): Evidence from lithostratigraphy and geochemistry
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Eruption history and petrogenesis of rocks from Nyos volcano (NW Cameroon): Evidence from lithostratigraphy and geochemistry

机译：尼奥斯火山（喀麦隆西北部）岩石的喷发历史和岩石成因：来自岩石地层学和地球化学的证据

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Even though ca 1746 people and over 3000 cattle were killed in 1986 by sudden release of about 800 million m(3) of CO2 from Lake Nyos volcano in northwest Cameroon, the lake's formation history is not known. Here we report results of a lithostratigraphic and petrogenetic study of Nyos volcano that allows us to confirm its phreatomagmatic (maar) origin. Eruptive products are divided into 2 units, the phases of each of which are closely related in time. Unit A comprises 4 phases, the last (A-4) represents the cataclysmic phreatomagmatic formation of Nyos maar and may have been triggered by collapse of the vent system of the previous (A-1 to A-3) phases, and/or reactivation of basement faults. After a repose period, activity shifted NE of the maar to form Unit B products. The B-1 phase of this unit deposited the scoria now covering most of the Lake Nyos area. Unit B-2 constructed the Fon's cone. A small lava flow (Unit B-3) represents the latest phase of volcanic activity of Nyos volcano. Based on area-thickness estimation methods, a total of ca 0.8 km(3) of eruptive material was produced from the volcano. Geochemical data suggest that magma of the 2 units probably formed by melting of the same garnet-bearing OIB-like asthenospheric mantle source, and evolved mainly by crustal contamination and fractional crystallization in independent magma batches that erupted without mixing. Our results provide a basis for advice on general hazard mitigation in the Lake Nyos area. (C) 2019 Elsevier B.V. All rights reserved.
机译：尽管在1986年，喀麦隆西北部的尼奥斯湖火山突然释放了约8亿立方米（3）的二氧化碳，造成约1746人死亡和3000多头牛被杀死，但该湖的形成历史尚不清楚。在这里，我们报告了Nyos火山的岩石地层学和岩石成因研究的结果，这使我们能够确定其岩浆岩浆（maar）的起源。喷发产品分为2个单元，每个阶段的时间密切相关。单元A包含4个阶段，最后一个（A-4）代表Nyos maar的灾难性岩浆岩形成，可能是由先前（A-1至A-3）阶段的排空系统坍塌和/或重新激活触发的地下断层。休养期过后，活动转移到了Maar的NE上，形成了B单元产品。该部队的B-1阶段沉积的火山灰现在覆盖了尼约斯湖大部分地区。 B-2部队建造了Fon锥。少量的熔岩流（B-3单元）代表了尼约斯火山的最新火山活动阶段。根据面积厚度估算方法，该火山总共产生了约0.8 km（3）的喷发物质。地球化学数据表明，这两个单元的岩浆可能是由相同的带有石榴石的OIB类软流圈地幔源融化形成的，并且主要是由地壳污染和部分结晶形成的，这些岩浆在独立的岩浆批次中爆发而没有混合。我们的研究结果为尼约斯湖地区总体减灾建议提供了依据。 （C）2019 Elsevier B.V.保留所有权利。

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