Experimental Study of Water Leakage from Melt Inclusions in Quartz During Laboratory Heating

Virginia Polytechnic Institute And State University, Blacksburg VA

Investigators

Abstract

Glassy, silicate melt inclusions trapped in igneous minerals contain samples of the melt that was present in the magma chamber beneath an active volcano. These inclusions provide one of the best tools available for determining water concentrations in magmas, and have been used to determine the volatiles present in magmas. Moreover, because the solubility of water in silicate melts as a function of P, T and X is well known, the pressure at trapping may be estimated from the water content. A basic assumption required to use melt inclusions to understand processes in magma chambers is that the inclusions have not lost or gained components following trapping. While this assumption is generally valid for most melt components, it is known that water (or hydrogen) diffuses through most minerals very easily and can be lost from (or gained by) inclusions following entrapment. This project involves a systematic study using both natural and synthetic silicate melt inclusions to identify those laboratory heating techniques that are most likely to preserve the original water content of the melt inclusions. Natural and synthetic silicate melt inclusions will be characterized before heating to determine the size, shape, and distance from the crystal surface or fracture, and then heated by one of several techniques, followed by Raman analysis of the melt to determine the water content. These results will be used to develop a protocol for selecting and homogenizing crystallized silicate melt inclusions that will minimize water loss. Broader impacts of this project include the training of both graduate and undergraduate students in modern experimental and analytical techniques. An important outreach component of this project involves the establishment of the Roedder Digital Library. The library will include digital images of all the fluid inclusions that Dr. Roedder has published over his 68-year professional career. These images will be made available for educational and research usage through the worldwide web and become an important resource for those teaching and conducting research in a broad range of earth science areas.