Fluid Flow Events in the Southern Dabashan Fold-thrust Belt, Central China: Insight From Fluid Inclusion and Isotope Data in Calcite Veins

Abstract

The authors systematically analyzed fluid inclusions in calcite veins from 33 samples collected from the fractures zones in 3 different units of southern Dabashan (SDBS) fold-thrust belt to study the characteristics of fluids in the different units and determine possible migration pathways of the fluids with particular reference to the petroleum exploration potential in the region. Homogenization temperatures and salinities of fluid inclusions and their stable isotope (δD, δ18O) showed a distinct zonation and variations of fluid characteristics in the different tectonic units of the SDBS fold-thrust belt. Homogenization temperature measurements and fluorescence observation results indicated that faults are the main conduits for fluids during their active periods. Oxygen and hydrogen isotopic compositions from the imbricate thrust belt to the fold-thrust belt and to the front detachment-fold belt shift from a mixing of surface meteoric water and sedimentary formation water box toward the magmatic water zone and metamorphic zone. The front detachment-fold belt has the best condition for petroleum preservation and is the potentially favorable area for future exploration.