28 research outputs found
Diffusively disseminated hydrogen-hydrocarbon gases in rocks of nepheline syenite complexes
Combined application of sample-melting and -crushing to isotopic investigations of noble gases (Taking He as an example)
Noble gas isotopes and carbon in rocks of the foidite-syenite complexes, the Kola Alkaline Province (KAP), Russia
Features and Factors of Time Variations in Hydrogen Release at Lovozersky Rare-Metal Deposit (Kola Peninsula)
Trapped helium in the rocks: Preferable minerals and retaining (After the example of Kola Peninsula rocks age of 370 Ma)
Relationships between gas geochemistry and release rates and the geomechanical state of igneous rock massifs
In contrast to sedimentary sequences, the relationships between the stressed state of igneous rocks and the chemistry and physical properties of gases contained within them are not well known. Here, we attempt to fill this gap by using, as an example, the apatite-nepheline and rare-metal ore deposits hosted within the Khibiny and Lovozero alkaline nepheline-syenite complexes of the Kola Peninsula, NW Russia. These massifs are characterized by unusually high, for igneous rocks, contents of multi-component, essentially hydrogen-hydrocarbon, gases and also by high hardness, elasticity and unevenly distributed, subhorizontal tectonic stresses. Relationships between the chemical and dynamic characteristics of the gases and the geomechanical properties of the host rocks have been examined using field observations and laboratory experiments. Patterns of gas release variations in time and space, gas emissions from rock pillars during artificial loading, variations of gas pressure in sealed shot-holes and changes in liberation rates of gaseous components during experimental rock loading are suggested to result from changes in rock stress and deformation state. Gas compositions in sealed shot-holes in stressed rocks change with time. Partly this is due to belated release of gases held in fluid inclusions and isolated voids and their subsequent mixing with gases held in interconnected fracture systems as the included gases are preferentially released as fluid inclusion arrays are opened during later stages of stress build-up. Partly it may also be because released gases may react with new fracture surfaces to generate enhanced levels of reduced H2 gases