Fluid inclusion
- 1. Priya Verma 2nd semester Msc Geology
- 2. Fluid inclusion is a microscopic bubble of liquid &gases that is trappedin mineral . Range in size : 0.1- 1mm Visible in microscopic study Formed from defects in crystals during their growth which lead to the entrapment of fluid in their surrounding. Trapped fluid maybe : liquid, vapour, or supercritical fluids. Host minerals are: Sphalerite, Cassiterite, Quartz,Calcite, Dolomite, fluorite , topaz etc Somefeldspar in granite also contain fluid inclusion
- 4. Vapour contains or liquid phase : H2O Gas phase: CO2,CH2,H2S,Cl,etc Solid phase: Na, K, Ca, Mg, Fe and their salt. E.g: NaCl
- 5. Classification of Fluid Inclusions: It relates the timing of formation of the inclusion relative to that of the host mineral (Bodnar, 2003). Based on their origin, fluid inclusions are of following types: • Primary Secondary • Pseudo secondary
- 6. It is formed during the formation of the enclosing crystal are primary in origin. Trapped along the growth zones and crystal faces. Very good indicators of the condition of crystallization.
- 7. Trapped in the fractures which are developed after the formation of host mineral. At the time of healing. Occur as trails or clusters Often cut across the grain boundaries. They can reveal the evolution of pressure, temperature and chemistry of fluids.
- 10. Trapped during formation of the host minerals. Occur along trails
- 11. Commonly identified as primary or secondary on the basis of detailed petrological study. Single Crystal
- 12. Zoned crystal • It provides important guides for identifying primary fluid inclusion
- 13. They are of 3 types: Isolated, Clustered, Trail-Bound inclusion • Isolated: Basically primary but additional criteria are required to know about its principle nature.
- 14. Clustered: typically comprised of a group of 10-20 neighbouring inclusions. : may have quite different origins such as neighbouring isolated cavities. Trail bound: It either remain confined to a single mineral or cut across different grains or phases.
- 16. Trapped fluid inclusions are sometimes modified because of several processes subsequent to their trapping. It cause reduction in their volume, change in morphology and often loss of originally trapped fluid. Some mechanisms are: Recrystallization Stretching and Necking-down Explosion Decrepitation Leakage
- 17. Sample Preparation Fluid Inclusion Petrography Microthermometry Raman Microprobe
- 19. Fluid inclusions provide a wealth of information on the geofluids that influenced the petrogenesis of rocks. Such inclusions provide important information: Temperature of Entrapment of Fluid Pressure of the Fluid System Density of Fluids Salinity of Fluids Composition of Fluids P-T History of the Sample Gas Composition of the Inclusions
- 20. The more direct uses of fluid inclusions in exploration mainly rely on defining an empirical relationship between some inclusion characteristic and mineralization. It is used for mineral exploration : for hydrothermal deposits like, copper , gold, silver etc.
- 21. If the hydrothermal fluid is highly saline, above 23% NaCl. Halite can crystallise upon cooling with solid crystals present. Such fluids usually occur in porphyry copper deposits or the core of igneous intrusion derived fluid systems. * Saline inclusions are less common.