"Constraining the History of Fluid Events Using the Fluid Inclusion Assemblage (FIA) Method for Collecting, Displaying and Interpreting Microthermometric Data"
Dr. Andras Fall
Research Associate, Bureau of Economic Geology
Fluid inclusion microthermometric data provide information on the Pressure-Temperature-Composition (P-T-X) fluid history associated with geological processes. During the past several decades fluid inclusions have become a standard tool to study fluid properties and, in spite of the long history of fluid inclusion research and their widespread use in hundreds of laboratories around the world, a universally accepted protocol for the collection, interpretation and presentation of fluid inclusion data is lacking. This, in turn, limits the quality and applicability of fluid inclusion data to place rigorous constraints on fluid evolution and P-T history of geologic systems. Here, we present an approach that allows researchers to test the quality and reliability of fluid inclusion data and to maximize the amount of information that can be extracted from those data. Many geologic processes occur in association with hydrothermal fluids and some of these fluids are eventually trapped as fluid inclusions in minerals formed during the process. The most important step of a fluid inclusion study is the identification of Fluid Inclusion Assemblages (FIA) that represent the finest (shortest time duration) geologic event that can be constrained using fluid inclusions. Homogenization temperature data obtained from fluid inclusions is often used to reconstruct temperature history of a geologic event. The precision with which fluid inclusions constrain the temperatures of a fluid events depends on the precision with which the temperature of a fluid inclusion assemblage can be determined. Homogenization temperature variations within FIAs depend on many factors that vary within different geological environments, and in order to determine minimum and acceptable temperature ranges for FIAs formed in different environments we investigated FIAs in several geologic environments, including sedimentary, metamorphic, and magmatic hydrothermal systems.