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首页> 外文期刊>Contributions to Mineralogy and Petrology >The Campanian Ignimbrite (southern Italy) geochemical zoning: insight on the generation of a super-eruption from catastrophic differentiation and fast withdrawal
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The Campanian Ignimbrite (southern Italy) geochemical zoning: insight on the generation of a super-eruption from catastrophic differentiation and fast withdrawal

机译：Campanian Ignimbrite（意大利南部）地球化学区划：从灾难性分化和快速撤离中产生超喷发的见解

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摘要

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.
机译：在Campanian Ignimbrite超级喷发过程中，爆发了约39 ka的大约100 km 3 几乎均质的晶体稀薄的方沸石和大约100 km 3 的微带状长寿石。在那不勒斯地区。分配系数计算，平衡矿物组合，玻璃成分和质地被用来重建喷发前储层的成分，热和压力梯度，以及向岩浆室超压和喷发演化的时间和机制。我们的岩石学数据表明，在CI喷发之前，坎帕尼亚平原下2.5 kmbar处有一个宽大的基石状的曲折岩浆室。高液相线（1199°C）的桥形基台与凉爽的乡村岩石之间的热交换引起强烈的过冷，从而导致灾难性的快速原位分步结晶和地壳同化（10 2 年），从而产生水过饱和的胶结顶盖和腔室中的超压触发了超级喷发。此过程最终导致了突然的油藏开度和快速的一步高减压。 Sanidine phenocrysts晶体的大小分布显示出较高的分化率，因此表明这种基岩状的岩浆系统能够在很短的时间内演化，并且仅在短期预警下突然爆发。

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