Fluid Inclusion Petrography
This chapter presents practical methodologies for examining the petrographic characteristics of fluid inclusions in diagenetic minerals, together with a format for interpreting the diagenetic environment and thermal history of a sample from the petrography of the fluid inclusions alone! Accomplishing a study of fluid inclusion petrography is much like any other petrographic study in that there are certain necessities, and some amount of thought and effort is required before a sample can be studied: samples must be collected with respect to the problem at hand, samples must be prepared for microscopic observation, and a properly adjusted microscope must be available. The difference between standard thin section petrography and fluid inclusion petrography is that each of these mechanical steps must be carried-out with great care; otherwise, great barriers will impede even the most persevering scientist from obtaining useful information from the fluid inclusions. Luckily, the reader will be relieved to know that these mechanics have been solved to the extent that all that is required for their successful implementation is to take note of the information presented in this chapter.
The next hurdle will be for an inclusionist to record the fluid inclusion petrography. This is not a trivial undertaking — remember what it was like when you took your first thin section petrography course! In a single thin section there can be thousands of crystals. The object is to be selective: a petrographer learns to answer a series of mental questions (e.g., minerals present, textures present, etc.) in order to
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.