Volatiles (S-CO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;-H&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O-Cl-F) Behavior during the AD 1944 Eruption

Angelo Paone

doi:10.4236/ijg.2015.63017

Abstract

The AD 1944 is the last vulcanian-effusive eruption of Vesuvius volcano. I have reviewed most of the major and volatile elements in order to better understand the eruptive dynamic of this hazardous volcano. These volcanic products were basically formed by at least two main petrogenetic mechanisms: 1) mixing, 2) crystal fractionation. Crystal fractionation plays a major role in the evolution of the volcanic products of the AD 1944 eruption. According to the major elements data, several fractionation lines can be employed. Volatile data are analyzed in sequence. Indeed, the volatile data allow an insight into the exsolution and degassing processes occur during the growth and eruption of the AD 1944 eruption. Some inferences are also made on the exsolution and degassing depth. The volatile data illustrate a sequential order of exsolution for the AD 1944 eruption: Cl-H2O-CO2-S and finally as volatile phase degassed fluorine. The eruption has not interacted with external water. An early exsolution of Cl in Cl-rich magmas is also confirmed by experimental and geological studies (3 - 4 Kbars) coinciding with the deep magma reservoir.

Highlights

On the scale of an individual eruption, volatiles affect most aspects of its physical and chemical behavior
From the bulk of major elements and volatile data recovered from the literature [1]-[6], it is possible to draw a schematic behavior of the AD 1944 eruption
The major element data illustrate the petrogenetic mechanism of the AD 1944 eruption

Summary

Introduction

On the scale of an individual eruption, volatiles affect most aspects of its physical and chemical behavior. CaO-SiO2 diagram is shown to explain the petrogenetic mechanism during the 1944 last eruption of Vesuvius volcano relating the data on the lavas, scoria, and tephra and melt inclusion trapped into the main phenocrysts of respectively lava and tephra [3] [4]. The major element data (CaO-SiO2 diagram, Figure 1) show that the melt inclusion trapped in the cpx of the 1944 lava flow has relatively more evolved composition in comparison with the lava whole rock data. This shift of the whole rock data at less evolved composition can be explained by mixing the composition of the lava melt inclusion with the melt inclusion trapped in the main phenocryst composing the tephra erupted successively (lava fountains and vulcanian phase, [4]). I can employ multi fractional crystallization evolutionary lines for the single 1944 AD eruption (Figure 1)

Sulfur Data

Carbon Dioxide and Water Data

Chlorine Data

Fluorine Data

Discussion and Conclusions