Juvenile Petroleum Comes from Deep Fluid Inclusions

Alexander Kitchka
CASRE, Kiev, Ukraine

Fluid inclusions are natural occurrences in rock bodies that were in the fluid state at the time of entrapment. Hydrocarbons, mainly methane and its homologues, are not rare constituents of fluid inclusions, which also include liquid oils and bitumens. The suggestion that hydrocarbon-rich, primordial fluid inclusions concentrated in the basal lithosphere are released and migrate from time to time on pathways opened tectonically suggests massive inorganic petroleum discharges. This suggested scenario for the origin of petroleum is based on the theory that hydrocarbon accumulations in sedimentary basins, with the exceptions of coalbed methane and similar proxies of organic origin, are derivatives of fluid inclusions from the underlying petroleum-prone basement. Crushing of crystalline rocks in zones of regional, mantle-driven faulting is interpreted to explain the release of deep fluids that may have been trapped in miarolitic clusters of negative crystals for hundreds of millions of years. Thereby, the fluid depletion of the tectonosphere is a direct consequence of dynamo-metamorphism that triggers and supports the “mild”, non-volcanic outgassing of the Earth's interior. Deep faults systems provide conduits and reservoirs for the migration and paroxismic streaming through intermediate fractured reservoirs or temporal barriers at seismogenic depths. It is not difficult to calculate that within an active fault zone, such as a regional strike-slip belt, that the crushing and mylonitization of rocks propagate to significant length, width and depth in the crust and involves thousands of cubic kilometers of host rocks and releases enormous fluid volumes from juvenile inclusions. This approach enables us to trace petroleum as it evolves from microscopic fluid inclusions in the crystalline sub-basement upward into the widely diverse oil and gas accumulations in sedimentary basins.

AAPG Search and Discovery Article #90072 © 2007 AAPG and AAPG European Region Conference, Athens, Greece