The Campanian Ignimbrite (southern Italy) geochemical zoning: insight on the generation of a super-eruption from catastrophic differentiation and fast withdrawal
The Campanian Ignimbrite (southern Italy) geochemical zoning: insight on the generation of a super-eruption from catastrophic differentiation and fast withdrawal
复制标题
坎帕尼亚 Ignimbrite（意大利南部）地球化学分区：深入了解灾难性分异和快速撤退导致的超级喷发
DOI：
--
复制
发表时间：
2008
期刊：
影响因子：
--
通讯作者：
G. Mastrolorenzo
中科院分区：
文献类型：
--
作者：
L. Pappalardo;L. Ottolini;G. Mastrolorenzo
超过约100公里3的几乎均匀的结晶贫响岩和约100公里3的略分区粗面岩爆发39万年在坎帕尼亚火山灰岩超级喷发，最强大的那不勒斯地区。分配系数计算，平衡矿物组合，玻璃成分和纹理被用来重建成分，热和压力梯度在喷发前的储层，以及时间和机制的演变对岩浆房超压和喷发。我们的岩石学数据表明，一个广泛的窗台状粗面质岩浆房下的坎帕尼亚平原在2.5千巴CI喷发前活动。高液相线（1199°C）的粗面岩岩床和冷的围岩之间的热交换导致强烈的过冷，驱动了灾难性的快速（102年）原位分离结晶和地壳同化，产生了水过饱和的响岩帽和引发超级喷发的超压室。这一过程最终导致水库突然开放，并在一个快速的单步高减压。透长石斑晶的粒度分布显示出高的分异率，这表明这种类似于岩床的岩浆系统能够在很短的时间内演化，并且只有短期警告的突然喷发。
More than ca 100 km3 of nearly homogeneous crystal-poor phonolite and ca 100 km3 of slightly zoned trachyte were erupted 39 ka during the Campanian Ignimbrite super eruption, the most powerful in the Neapolitan area. Partition coefficient calculations, equilibrium mineral assemblages, glass compositions and texture were used to reconstruct compositional, thermal and pressure gradients in the pre-eruptive reservoir as well as timing and mechanisms of evolution towards magma chamber overpressure and eruption. Our petrologic data indicate that a wide sill-like trachytic magma chamber was active under the Campanian Plain at 2.5 kbar before CI eruption. Thermal exchange between high liquidus (1199°C) trachytic sill and cool country rocks caused intense undercooling, driving a catastrophic and fast (102 years) in situ fractional crystallization and crustal assimilation that produced a water oversaturated phonolitic cap and an overpressure in the chamber that triggered the super eruption. This process culminated in an abrupt reservoir opening and in a fast single-step high decompression. Sanidine phenocrysts crystal size distributions reveal high differentiation rate, thus suggesting that such a sill-like magmatic system is capable of evolving in a very short time and erupting suddenly with only short-term warning.