Trans-Pecos Province Magma Types
Nathanial Matis
01/12/2014
Trans-Pecos Province Magma Types
Nathanial Matis
Abstract
The Cretaceous was the starting point when the Laramide Orogeny began to fault and fold as a result of tectonic activity which pushed the Farallon plate into the North American plate forcing the subduction of the Farallon. This subduction caused the plate to melt and form magma that either formed laccoliths, or intruded country rock with different igneous compositions. These compositions ranged from alkaline to mafic to rhyolitic based on their interactions as they made their way to the surface with country rock. Mafic magma interacts well with host rock while rhyolitic magma does not due to its high viscosity. …show more content…
In the TPMP, there are specific areas such as the Rattlesnake Mountain Sill, located in the western part, that has the best exposed sill with medium to fine grained syenodiorite rock in the northern and southern regions of the mountain (Carman, 1994). The textures in these rocks go from a glassy devitrified content to very fine grained on the surface and medium to coarse grained in the center where contact with country rock and fast cooling cannot occur (Carman, 1994). The major minerals contained within these basalts are augite, olivine, Fe-Ti oxides, and biotites which contain compositional zoning, and zoning in feldspar grains and some pyroxenes (Carman, 1994). Phenocrysts occur on the cooled edges of the Big Bend sills which, when present in a magma intrusion, are rather important because the settling of phenocrysts signifies the major factor in differentiation in intrusions (Carman, 1994). However, phenocrysts are very rare in the Rattlesnake Mountain Sill contact rock, but that does not rule out the possibility of flow differentiation that may have reduced the phenocrysts along the borders (Carman, 1994).Plagioclase grains have a bimodal size distribution with the smaller size having a greater plethora than the larger of the two because the larger ones were transported in by …show more content…
144-145, pg. 161-176. (Adams, 2012)
Befus, K., Breyer, J., Busbey, A., Hanson, R., Miggins, D., 2009, Nonexplosive and explosive magma/wet-sediment interaction during emplacement of Eocene intrusions into Cretaceous to Eocene strata, Trans-Pecos igneous province, West Texas, Journal of Volcanology and Geothermal Research, v. 181, pg. 155-172. (Befus, 2009)
Urbancyzk, K., White, J., 2001, Origin of a silica-oversaturated quartz trachyte-rhyolite suite through combined crustal melting, magma mixing, and fractional crystallization: the Levya Canyon volcano, Trans-Pecos Magmatic Province, Texas Journal of Volcanology and Geothermal Research, v. 111, 155-182. (Urbancyzk, 2001)
Davidson, M., 2014, Zircon Geochronology of Volcanic Rocks from the Trans-Pecos orogenic belt, western Texas: Timing the cessation of Laramide folding, uplift, and post flat-slab ignimbrite flare-ups, University of Houston, pg. 6-22. (Davidson, 2014) Maxson, J., Tikoff, B., 1996, Hit-and-run collision model for the Laramide Orogeny, western United States, Geological Society of America, v. 24, pg. 968-972. (Maxson,
Nathanial Matis
01/12/2014
Trans-Pecos Province Magma Types
Nathanial Matis
Abstract
The Cretaceous was the starting point when the Laramide Orogeny began to fault and fold as a result of tectonic activity which pushed the Farallon plate into the North American plate forcing the subduction of the Farallon. This subduction caused the plate to melt and form magma that either formed laccoliths, or intruded country rock with different igneous compositions. These compositions ranged from alkaline to mafic to rhyolitic based on their interactions as they made their way to the surface with country rock. Mafic magma interacts well with host rock while rhyolitic magma does not due to its high viscosity. …show more content…
In the TPMP, there are specific areas such as the Rattlesnake Mountain Sill, located in the western part, that has the best exposed sill with medium to fine grained syenodiorite rock in the northern and southern regions of the mountain (Carman, 1994). The textures in these rocks go from a glassy devitrified content to very fine grained on the surface and medium to coarse grained in the center where contact with country rock and fast cooling cannot occur (Carman, 1994). The major minerals contained within these basalts are augite, olivine, Fe-Ti oxides, and biotites which contain compositional zoning, and zoning in feldspar grains and some pyroxenes (Carman, 1994). Phenocrysts occur on the cooled edges of the Big Bend sills which, when present in a magma intrusion, are rather important because the settling of phenocrysts signifies the major factor in differentiation in intrusions (Carman, 1994). However, phenocrysts are very rare in the Rattlesnake Mountain Sill contact rock, but that does not rule out the possibility of flow differentiation that may have reduced the phenocrysts along the borders (Carman, 1994).Plagioclase grains have a bimodal size distribution with the smaller size having a greater plethora than the larger of the two because the larger ones were transported in by …show more content…
144-145, pg. 161-176. (Adams, 2012)
Befus, K., Breyer, J., Busbey, A., Hanson, R., Miggins, D., 2009, Nonexplosive and explosive magma/wet-sediment interaction during emplacement of Eocene intrusions into Cretaceous to Eocene strata, Trans-Pecos igneous province, West Texas, Journal of Volcanology and Geothermal Research, v. 181, pg. 155-172. (Befus, 2009)
Urbancyzk, K., White, J., 2001, Origin of a silica-oversaturated quartz trachyte-rhyolite suite through combined crustal melting, magma mixing, and fractional crystallization: the Levya Canyon volcano, Trans-Pecos Magmatic Province, Texas Journal of Volcanology and Geothermal Research, v. 111, 155-182. (Urbancyzk, 2001)
Davidson, M., 2014, Zircon Geochronology of Volcanic Rocks from the Trans-Pecos orogenic belt, western Texas: Timing the cessation of Laramide folding, uplift, and post flat-slab ignimbrite flare-ups, University of Houston, pg. 6-22. (Davidson, 2014) Maxson, J., Tikoff, B., 1996, Hit-and-run collision model for the Laramide Orogeny, western United States, Geological Society of America, v. 24, pg. 968-972. (Maxson,