Practical Aspects of Geothermometry
Ascertaining thermal information from fluid inclusions is known as fluid inclusion geothermometry. In Chapter 6, crude petrographic methods for determining thermal conditions of entrapment and post-entrapment history are introduced. The appropriate procedures for collecting microthermometric data from inclusions are presented in Chapter 7, in which the approach of collecting data from fluid inclusion assemblages (FIAs) is stressed. In Chapter 3 the basic principles for understanding the significance of microthermometric data are covered, and in Chapter 4 some processes that can modify inclusions and affect the resulting microthermometric data are treated. Thus, at this point, it should be relatively clear to readers that there is a sound theoretical basis for interpreting microthermometric data as meaningful indicators of some aspects of the thermal history that a rock has experienced. In addition, readers should have developed an appreciation for the fact that there are natural processes that occur which may render the interpretation of Th data less straightforward than they might have originally thought! The purpose of this chapter is to present a systematic framework for interpreting fluid inclusion microthermometric Th data in order to obtain valid information regarding temperature of mineral precipitation, minimum temperature of mineral precipitation, or merely temperatures that a rock has experienced. The limitations of various procedures will be stressed throughout this presentation.
Correct utilization of fluid inclusions as geothermometers begins with observations of fluid inclusion assemblages (FIAs) — groups of fluid inclusions that come from the most finely discernible event of inclusion entrapment. The reason for making observations
Figures & Tables
The past decade has revealed significant advantages to using fluid inclusions as a means of understanding the physical and chemical history of fluids in sedimentary basins, but it also has revealed important limitations which have required that a new approach must be employed to effectively use fluid inclusions. This book is divided into six sections: (1) what fluid inclusions are and what geologic history they are capable of recording; (2) basic phase equilibria that must be known to understand the behavior of pore fluids and fluid inclusions in nature; (3) the question of validity of using fluid inclusions as records of ancient diagenetic systems is dealt with in such a way that the questions commonly asked about the limitations of the technique are addressed; (4) hot to conduct a fluid inclusion study, a new petrographically based approach for conducting fluid inclusion research that is followed by methods that allow for the interpretation of compositions of pore fluids that existed in sedimentary rocks, and methods of geothermometry and geobarometry; (5) selected case histories that are designed specifically to give practice in evaluating fluid inclusion data from the diagenetic realm; and (6) a summary of the arsenal of analytical techniques that may be applied to fluid inclusions to develop additional constraints on fluid inclusion composition.