The Averno 2 fissure eruption: a recent small-size explosive event at the Campi Flegrei Caldera (Italy)
The Averno 2 fissure eruption: a recent small-size explosive event at the Campi Flegrei Caldera (Italy)
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Averno 2 裂缝喷发：最近在 Campi Flegrei Caldera（意大利）发生的一次小规模爆炸事件
DOI：
10.1007/s00445-010-0417-0
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发表时间：
2011
影响因子：
3.5
通讯作者：
G. Orsi
中科院分区：
文献类型：
--
作者：
M. D. Di Vito;I. Arienzo;G. Braia;L. Civetta;M. D’Antonio;Valeria Di Renzo;G. Orsi
Averno 2喷发（3，700 ± 50 aB. P.）是一个爆发性的低震级事件，其特征是岩浆和蒸汽岩浆爆炸，分别产生主要的下降和浪涌床。它发生在Campi Flegrei破火山口（坎帕尼亚地区，意大利南部）的西段，位于两个活动断层系统的交叉处，分别为NE和NW。形态复杂的火山口区域，主要由Averno湖填充，是由喷口活化和沿沿着NE向断层系统迁移造成的。火山爆发产生了一个复杂的火山碎屑沉积序列，包括下部的浮石沉积，以及中上部的主要浪涌床。通过地层学、构造地貌学和岩石学研究，将其划分为A ~ C三段。A段是在喷发的第一阶段主要通过岩浆爆炸形成的，产生的柱体最高可达10公里。在这一阶段的喷发达到高潮，质量排放率为3.2 106公斤/秒。强烈的断裂和断层活化有利于大量的水进入系统，这产生了由高效率的水-岩浆相互作用驱动的爆炸。这些爆炸产生了由湿到干的浪涌沉积物，分别使B段和C段就位。等值线和等值线图，以及区域分布的弹道碎片和相变化的浪涌存款允许定义四个喷口，打开沿着东北方向，2公里长的裂缝。喷发期间喷出的岩浆总量估计约为0.07立方公里（DRE）。喷发产物的成分范围从最初的弱过碱性粗面岩到最后侵位的碱性粗面岩。同位素数据和建模表明，混合发生在阿韦尔诺2喷发之间的一个更进化，较少的放射性储存的岩浆，和一个更少的进化，更多的放射性岩浆进入浅水库触发喷发。喷发的早期阶段，在此期间，出口从西南迁移到本湖的中心，由更先进的，最上层的岩浆，而以下阶段挤出较少的进化，最低的岩浆。地质和岩石学结果的整合表明，阿韦尔诺2复杂的喷发是从一个堤形浅水库侵入到东北-西南断层系统接壤的La Starza复活块西部，在破火山口地板。
The Averno 2 eruption (3,700 ± 50 a B.P.) was an explosive low-magnitude event characterized by magmatic and phreatomagmatic explosions, generating mainly fall and surge beds, respectively. It occurred in the Western sector of the Campi Flegrei caldera (Campanian Region, South Italy) at the intersection of two active fault systems, oriented NE and NW. The morphologically complex crater area, largely filled by the Averno lake, resulted from vent activation and migration along the NE-trending fault system. The eruption generated a complex sequence of pyroclastic deposits, including pumice fall deposits in the lower portion, and prevailing surge beds in the intermediate-upper portion. The pyroclastic sequence has been studied through stratigraphical, morphostructural and petrological investigations, and subdivided into three members named A through C. Member A was emplaced during the first phase of the eruption mainly by magmatic explosions which generated columns reaching a maximum height of 10 km. During this phase the eruption reached its climax with a mass discharge rate of 3.2 106 kg/s. Intense fracturing and fault activation favored entry of a significant amount of water into the system, which produced explosions driven by variably efficient water-magma interaction. These explosions generated wet to dry surge deposits that emplaced Member B and C, respectively. Isopachs and isopleths maps, as well as areal distribution of ballistic fragments and facies variation of surge deposits allow definition of four vents that opened along a NE oriented, 2 km long fissure. The total volume of magma extruded during the eruption has been estimated at about 0.07 km3 (DRE). The erupted products range in composition from initial, weakly peralkaline alkali-trachyte, to last-emplaced alkali-trachyte. Isotopic data and modeling suggest that mixing occurred during the Averno 2 eruption between a more evolved, less radiogenic stored magma, and a less evolved, more radiogenic magma that entered the shallow reservoir to trigger the eruption. The early phases of the eruption, during which the vent migrated from SW to the center of the present lake, were fed by the more evolved, uppermost magma, while the following phases extruded the less evolved, lowermost magma. Integration of the geological and petrological results suggests that the Averno 2 complex eruption was fed from a dyke-shaped shallow reservoir intruded into the NE-SW fault system bordering to the west the La Starza resurgent block, within the caldera floor.