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The petroleum system can be affected in a variety of different ways by the occurrence of magmatism in a region. The associated igneous rocks can be emplaced by several mechanisms, ranging from a shallow mantle source driven by edge convection (Model #1), to a deep seeded lower mantle plume source, with its roots in the core mantel boundary (Model #2), to a passive mantle with the lithosphere driving the emplacement process (Model #3). However, the results of the interaction between the magma and the surrounding country rock are independent of the mechanism that sourced them. Both intrusive and extrusive igneous complexes are associated with the Northern coast of the Gulf of Mexico. The extrusive rocks form volcanoes, lava and ash flows, volcaniclastic sedimentary rocks, and ring dike complexes, while the intrusive form pluton, dikes and often result in small scale and regional uplifts. These features directly affect the accumulation of hydrocarbon resources in the region. The plutons can warp the sedimentary layers and act as seals for a hydrocarbon system. In rare cases the igneous rock can even act as the reservoir rock for the hydrocarbons; the DINEH-BI-KEYAH field in which a Syenite sill, that is highly fractured, acts as such a reservoir. The igneous rocks can also provide a source of other economical elements not typically associated with oil and gas production. For example Helium can be recovered from the decomposition or physical and chemical breakdown of igneous rock, and can be incorporated into the gas that is recoverable from a hydrocarbon system.
The thermodynamic effects of a magmatic system on oil and gas maturation and production are very obvious. Both the extrusive and intrusive systems can completely burn off any potential petroleum products, if they are developing coeval with the occurrence of the magmatism. The lateral migration of heat and hydrothermal fluids associated with a rising packet of melt through the crust can alter the sedimentary rocks surrounding it and result in increased or decreased porosity, permeability and other associated properties.