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A chemical study of Hawaiian magmatic gases
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|Title:||A chemical study of Hawaiian magmatic gases|
|Authors:||Heald, Emerson Francis|
|Keywords:||Lava -- Analysis|
|Abstract:||The spectacular sight of a volcano in eruption has fascinated mankind since prehistoric times. Early man thought volcanoes to be the work of all-powerful gods residing in the earth. The ancient Hawaiians, for instance, had the greatest respect for the legendary Volcano Goddess Pele, whom they feared would punish them with lava flows if she were displeased. This belief has survived to the present day; people on the island of Hawaii still offer gifts to Pele to win her favor.(1) A volcano is an extension of one of the huge bodies of subterranean rock material called magma, which solidifies to form the igneous rocks of the earth's crust. lava is magma. which has flowed onto the earth's surface, and volcanic gases are the volatile materials associated with the magma. Both provide a means of studying magmas, whose chemical composition must otherwise be inferred from the rocks they form.(2) A magma is a hot, fluid substance, consisting generally of a silicate phase, but sometimes also containing a separate gas phase. It may solidify or crystallize over a range of temperatures, from 1200°C. down to about 500°C., to form a variety of minerals and rocks. The solidification process may be extended over a wide range of time and space by fractional crystallization. If there is a separation of some of the components producing a change in the composition of the magma, this process is called differentiation. The volatile components of the magma, often called mineralizers, are believed to be very important in determining the course of differentiation. Furthermore, the residual solutions and gases left after the bulk of the magma has solidified or crystallized playa very important role in the formation of the ore deposits which contain large concentrations of the rarer components of the earth's crust.(3) It is, of course, not possible to reach down into a crystallizing magma and sample its volatile components. It is necessary to rely upon more indirect methods, such as analyzing the gases given off by igneous rocks when they are heated under vacuum, or examining the gases and condensates from fumaroles. As a result, there has been much controversy in the literature regarding the amount and composition of volatile magmatic materials. There has been much speculation (e.g., Graton, 1945) regarding their influence on volcanic phenomena, but little is actually known.(4) As a first step in gaining this knowledge, it is essential to develop systematic methods for studying volcanic gases and condensates, and to attempt to find the relationship between them and the original magmas from which they are presumably derived. The purpose of this investigation has been to apply the techniques of modern chemistry to the study of the volatile components of Hawaiian magmas. As an approach to this problem, it seemed desirable in the beginning to develop and extend the technique of vacuum fusion of rocks as a means of studying the oxidation state of their constituent elements. It was originally intended to study the geologically important regions of the Mg-Fe-O-Si system, and to examine the relationships between dissolved volatile material and the oxidation state of iron. Preliminary investigation, however, showed that too many uncertainties were introduced by the equipment presently available because of unavoidable reactions of the fused rock with crucible materials. Accordingly, the problem of magmas was approached from another direction - a study of the gases of the volcano Kilauea. A number of circumstances combined to make this possible. Most important was the 1959-60 eruption of Kilauea, which provided an opportunity for the collection of gas samples by modern methods. The gas chromatography system developed for analyzing gases from rocks was adapted easily to the analysis of volcanic gases. Furthermore, the establishment of the University of Hawaii Computing Center made available a high-speed digital computer for use in studying the complex equilibria occurring in volcanic gases. This thesis is therefore logically divided into two sections: First, an investigation of the applicability of the vacuum fusion technique to the determination of the oxidation state of the constituent elements of rocks, and second, a chemical study of the gases of the volcano Kilauea. It was hoped that these studies would complement each other in adding to our knowledge of the gases from volcanoes and heated rocks, thus helping to provide further understanding of the relationship of these gases to the primary volatile materials associated with magmas and volcanic rock types.|
Thesis (Ph. D.)--University of Hawaii, 1961.
Bibliography: leaves 110-115.
vi, 115,  l diagrs., tables
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|Appears in Collections:||Ph.D. - Chemistry|
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