A FLUID INCLUSIONS STUDY OF PUERTO RICO TERTIARY DOLOMITE

The island of Puerto Rico was divided by Schellekens (1991) in three different igneous provinces named; in the southwest, central and the northeast igneous provinces. These provinces are divided based on the lithology, geology and geochemistry. The north coast Tertiary limestone of Puerto Rico are composed of carbonate rocks that contain the most important aquifer in Puerto Rico. The statigraphy of the North Coast have been described by several authors. The dolomites of the north coast of Puerto Rico have been studied by González and Ruiz, 1991 and Ramírez, 2000. Both studies sugguest mixing zone dolomitization for these dolomites. This study is based on the study of fluid inclusions analysis in the Puerto Rico north coast dolomites to better constrain the environment of precipitation of these dolomites. The fluid inclusion analysis provided direct information on the environments and the temperatures of precipitation. The temperatures obtained for the fluid inclusions present in the samples IAS-4 (510.1m) are 0.0 and 0.1 that show a small quantity of salt in the samples. The inclusions in the dolomites suggest altered dolomites in freshwater environments. The fluid inclusion analysis in samples IAS-4 (420.1m) suggests either fresh water environments of dolomites or alteration in freshwater. Stable isotopic analysis in the same samples were made to help identify the environments of precipitation. The stable isotopic analysis in Garrochales, IAS-4, and IAS-1 cores indicated alterations in meteoric and marine waters. The calcite/dolomite was precipitated and altered in marine and meteoric environments