Structure of the Earth`s Crust in Fennoscandia as Revealed from
... reaching 56 km under the northeastern end of the profile. The crust can be divided into upper crust (P-wave velocity 5.6-6.45 km/s), middle crust (velocity of 6.6-6.75 km/s) and lower crust with velocities of 6.95 - 7.45 km/s. At the bottom of the lower crust a layer with a velocity higher than 7.35 ...
... reaching 56 km under the northeastern end of the profile. The crust can be divided into upper crust (P-wave velocity 5.6-6.45 km/s), middle crust (velocity of 6.6-6.75 km/s) and lower crust with velocities of 6.95 - 7.45 km/s. At the bottom of the lower crust a layer with a velocity higher than 7.35 ...
metamorphic rocks - Math/Science Nucleus
... Contact metamorphism does not affect as large an area as regional metamorphism. It is associated with areas around a magma chamber as well as other smaller igneous structures like dikes or sills. Contact metamorphism zones can be a few centimeters to several kilometers, especially around large plut ...
... Contact metamorphism does not affect as large an area as regional metamorphism. It is associated with areas around a magma chamber as well as other smaller igneous structures like dikes or sills. Contact metamorphism zones can be a few centimeters to several kilometers, especially around large plut ...
Geol Soc London Spec Publ 204 2002
... played a crucial role in development of the region. There are at present a large number of other small plates and plate fragments, and there was probably a similar complexity throughout the Cenozoic (Hall 1996, 2002). The magmatic provinces of SE Asia and the western Pacific can be attributed to fou ...
... played a crucial role in development of the region. There are at present a large number of other small plates and plate fragments, and there was probably a similar complexity throughout the Cenozoic (Hall 1996, 2002). The magmatic provinces of SE Asia and the western Pacific can be attributed to fou ...
Clastic sedimentary rocks 0305731
... However, plagioclase is more common in sandstones derived from uplifted oceanic and island-arc terranes, which are generally less important source areas. Feldspar grains can be easily distinguished from quartz grains in thin sections. Crosshatch twining of microcline, and sometimes Carlsbad twining ...
... However, plagioclase is more common in sandstones derived from uplifted oceanic and island-arc terranes, which are generally less important source areas. Feldspar grains can be easily distinguished from quartz grains in thin sections. Crosshatch twining of microcline, and sometimes Carlsbad twining ...
Geology and Geotectonic Setting of the Basement Complex
... within the Pan African mobile belt in between the West African and Congo cratons. The Geology of Nigeria is dominated by crystalline and sedimentary rocks both occurring approximately in equal proportions (Woakes et al 1987). The crystalline rocks are made up of Precambrian basement complex and the ...
... within the Pan African mobile belt in between the West African and Congo cratons. The Geology of Nigeria is dominated by crystalline and sedimentary rocks both occurring approximately in equal proportions (Woakes et al 1987). The crystalline rocks are made up of Precambrian basement complex and the ...
Chapter 9. Sedimentary Rocks
... Medium-Grained Clastic Rocks Are Sandstone Sandstone (middle row in Figure 9.5) is a very common sedimentary rock, and there are many different kinds of sandstone. It’s worth knowing something about the different types because they are organized according to characteristics that are useful for the d ...
... Medium-Grained Clastic Rocks Are Sandstone Sandstone (middle row in Figure 9.5) is a very common sedimentary rock, and there are many different kinds of sandstone. It’s worth knowing something about the different types because they are organized according to characteristics that are useful for the d ...
Metamorphic Rocks and Cleavage Development Topics Geothermal
... • Deformation Fabric • Rock splits along preferred planes ...
... • Deformation Fabric • Rock splits along preferred planes ...
Precambrian meta-ultramafic rocks from the
... were observed in a chloritic blackwall in Beuler Cirque. Many ultramafic bodies in orogenic belts have been tectonically emplaced, and that is our interpretation for the Tobacco Root meta-ultramafic bodies (see below). This means that they are surrounded by faults. However, we have not been able to ...
... were observed in a chloritic blackwall in Beuler Cirque. Many ultramafic bodies in orogenic belts have been tectonically emplaced, and that is our interpretation for the Tobacco Root meta-ultramafic bodies (see below). This means that they are surrounded by faults. However, we have not been able to ...
View - GFZpublic
... age (Hargrove et al., 2006). Most of the AS formed during the Pan‐African orogenic cycle (~1000‐530 Ma) by suturing of juve‐ nile intra‐oceanic arc terrains followed by magmatic thickening, giving rise to regional metamorphism and the generation of batholiths of predominantly ...
... age (Hargrove et al., 2006). Most of the AS formed during the Pan‐African orogenic cycle (~1000‐530 Ma) by suturing of juve‐ nile intra‐oceanic arc terrains followed by magmatic thickening, giving rise to regional metamorphism and the generation of batholiths of predominantly ...
Linking rift propagation barriers to excess magmatism at volcanic
... In agreement with observations from the North and South Atlantic, and as imposed by the model’s boundary conditions, break-up in the model occurs via rift propagation (Figs. 2B and 2C). In the same manner, the area affected by decompression melting (between 65 km and 15 km depth beneath the rift cen ...
... In agreement with observations from the North and South Atlantic, and as imposed by the model’s boundary conditions, break-up in the model occurs via rift propagation (Figs. 2B and 2C). In the same manner, the area affected by decompression melting (between 65 km and 15 km depth beneath the rift cen ...
Earth SC-1002 Geological Wonder of Oman
... The Precambrian spans about 88% of Earth's history Between 4.5 billion years ago and ending approximately 540 million years ago Represented in the cores of the continents known as “shields” Important rock types: Greenstones and “granitoids”, Granulite facies metamorphic rocks. Important deposits of ...
... The Precambrian spans about 88% of Earth's history Between 4.5 billion years ago and ending approximately 540 million years ago Represented in the cores of the continents known as “shields” Important rock types: Greenstones and “granitoids”, Granulite facies metamorphic rocks. Important deposits of ...
Harris, 2007
... bounding lithologies above and below. If viscosities are sufficiently low within this layer, the material within it may flow in response to lateral variations in lithostatic load. Thus lower crustal flow provides a possible means by which lateral pressure gradients equilibrate and so moderate topogr ...
... bounding lithologies above and below. If viscosities are sufficiently low within this layer, the material within it may flow in response to lateral variations in lithostatic load. Thus lower crustal flow provides a possible means by which lateral pressure gradients equilibrate and so moderate topogr ...
Sierra Nevada uplift - University of Missouri
... results indicate that the relatively strong flow within the mantle lithosphere tends to drag crustal material, causing it to flow outward, as long as the density contrast between the upwelling asthenosphere and the surrounding lithosphere is maintained. Felsic material has a higher ductility than ma ...
... results indicate that the relatively strong flow within the mantle lithosphere tends to drag crustal material, causing it to flow outward, as long as the density contrast between the upwelling asthenosphere and the surrounding lithosphere is maintained. Felsic material has a higher ductility than ma ...
Chemistry of Igneous Rocks
... oarse-grained texture characteristic of plutonic rock. Plagioclase is white and quartz is gray; potassium feldspar has been stained ow. Small gradations on ruler are millimeters. (6) A similar rock seen through a polarizing microscope. Note the interlocking crystal ins of individual minerals. ...
... oarse-grained texture characteristic of plutonic rock. Plagioclase is white and quartz is gray; potassium feldspar has been stained ow. Small gradations on ruler are millimeters. (6) A similar rock seen through a polarizing microscope. Note the interlocking crystal ins of individual minerals. ...
Early Paleozoic Tectonic and Thermomechanical
... southward oceanic subduction. The process produced a wide mélange belt and the Qilian magmatic arc. Arc magmatism was active between 520 and 400 Ma, coeval with North Qaidam UHP metamorphism. The North Qaidam UHP metamorphic belt also spatially overlaps the early Paleozoic Qilian magmatic arc. Petro ...
... southward oceanic subduction. The process produced a wide mélange belt and the Qilian magmatic arc. Arc magmatism was active between 520 and 400 Ma, coeval with North Qaidam UHP metamorphism. The North Qaidam UHP metamorphic belt also spatially overlaps the early Paleozoic Qilian magmatic arc. Petro ...
Gabbroic Pegmatite Intrusions, Iberia Abyssal
... of 127 ± 4 Ma, which we interpret as an igneous age. The Site 1070 gabbro pegmatites are the only igneous rocks that are demonstrably coeval with rifting in the southern IAP. As such, they help to document the transition from non-volcanic margin to normal ocean crust formation in this part of the No ...
... of 127 ± 4 Ma, which we interpret as an igneous age. The Site 1070 gabbro pegmatites are the only igneous rocks that are demonstrably coeval with rifting in the southern IAP. As such, they help to document the transition from non-volcanic margin to normal ocean crust formation in this part of the No ...
Formation and Evolution of Granite Magmas During
... amphibolite-facies conditions of metamorphism. Orthopyroxene has not been observed. Retrograde greenschistfacies mineral assemblages are developed in some late shear zones. The Ti content of amphiboles coexisting with a Ti-saturating phase increases with temperature (Spear, 1981). Results from 27 Op ...
... amphibolite-facies conditions of metamorphism. Orthopyroxene has not been observed. Retrograde greenschistfacies mineral assemblages are developed in some late shear zones. The Ti content of amphiboles coexisting with a Ti-saturating phase increases with temperature (Spear, 1981). Results from 27 Op ...
Lower crustal earthquakes near the Ethiopian rift induced by
... rift axis may currently be particularly concentrated near volcanic centers, geophysical data suggest a small fraction of aligned partial melt is widespread in the lower crust beneath the NW plateau and may be important in accommodating minor amounts of extensional strain outside the MER [Keranen et ...
... rift axis may currently be particularly concentrated near volcanic centers, geophysical data suggest a small fraction of aligned partial melt is widespread in the lower crust beneath the NW plateau and may be important in accommodating minor amounts of extensional strain outside the MER [Keranen et ...
Upper mantle velocity-temperature conversion and composition
... geological units (10– 20 km) is irrelevant and one must consider an average heat production model. In the southern Superior Province, Perry et al. [2006] have studied in detail the distributions of heat flow and heat production. They demonstrated that the crusts of the volcano-plutonic belts (Wawa, ...
... geological units (10– 20 km) is irrelevant and one must consider an average heat production model. In the southern Superior Province, Perry et al. [2006] have studied in detail the distributions of heat flow and heat production. They demonstrated that the crusts of the volcano-plutonic belts (Wawa, ...
Oxygen and hydrogen isotope compositions of oceanic plutonic rocks
... between extensional veins oriented perpendicular to the metamorphic foliation and intensity of deformation. The veins related to deformation are either hornblende-bearing or hornblende- and sodic plagioclase-bearing, and are the most abundant vein type in the upper 250 m of core. Similar amphibole v ...
... between extensional veins oriented perpendicular to the metamorphic foliation and intensity of deformation. The veins related to deformation are either hornblende-bearing or hornblende- and sodic plagioclase-bearing, and are the most abundant vein type in the upper 250 m of core. Similar amphibole v ...
Mann et al in prep
... constraints as possible. The reconstructions show that some of the tectonic and geochemical complexities of the CAVA and CAVF may be related to structures and crustal variations in the upper plate. Some important tectonic elements of the CAVA that attest to its mobility, highlighted in reconstructio ...
... constraints as possible. The reconstructions show that some of the tectonic and geochemical complexities of the CAVA and CAVF may be related to structures and crustal variations in the upper plate. Some important tectonic elements of the CAVA that attest to its mobility, highlighted in reconstructio ...
Age and petrogenesis of the Tinn granite, Telemark, South
... Andersen, T., Andresen, A. & Sylvester, A.G. 2002: Age and petrogenesis of the Tinn granite, Telemark, South Norway, and its geochemical relationship to metarhyolite of Rjukan Group. Norges geologiske undersøkelse Bulletin 440, 19-26. The Tinn granite is a Mid Proterozoic, foliated pluton, situated ...
... Andersen, T., Andresen, A. & Sylvester, A.G. 2002: Age and petrogenesis of the Tinn granite, Telemark, South Norway, and its geochemical relationship to metarhyolite of Rjukan Group. Norges geologiske undersøkelse Bulletin 440, 19-26. The Tinn granite is a Mid Proterozoic, foliated pluton, situated ...
Cenozoic magmatism in the western Ross Embayment:
... dikes, most are 1 m thick and have alkali basalt-basanite-tephrite compositions, along with minor intermediate rocks. Trachytic-rhyolitic dikes (up to 50 m thick) are by far less common. The 40Ar-39Ar data for dikes indicate middle Eocene to early Oligocene ages, the oldest found to date for igneous ...
... dikes, most are 1 m thick and have alkali basalt-basanite-tephrite compositions, along with minor intermediate rocks. Trachytic-rhyolitic dikes (up to 50 m thick) are by far less common. The 40Ar-39Ar data for dikes indicate middle Eocene to early Oligocene ages, the oldest found to date for igneous ...
Buildup of a dynamically supported orogenic plateau: Numerical
... Ma following plate collision (from 31 to 20 mm yr21) [McQuarrie et al., 2003; Vernant et al., 2004], is distributed across a wide area, from the Persian Gulf in the South to the Alborz and Kopet Dagh belts in the North. Deformation marked by seismicity [Maggi et al., 2000] is concentrated in the Zag ...
... Ma following plate collision (from 31 to 20 mm yr21) [McQuarrie et al., 2003; Vernant et al., 2004], is distributed across a wide area, from the Persian Gulf in the South to the Alborz and Kopet Dagh belts in the North. Deformation marked by seismicity [Maggi et al., 2000] is concentrated in the Zag ...
Review of Late Jurassic-early Miocene sedimentation and plate
... Abstract Production of voluminous igneous arc rocks, high-pressure/low-temperature (HP/LT) metamafic rocks, westward relative migration of the Klamath Mountains province, and U–Pb ages of deposition, sediment sources, and spatial locations of Jurassic and younger, detrital zirconbearing clastic rock ...
... Abstract Production of voluminous igneous arc rocks, high-pressure/low-temperature (HP/LT) metamafic rocks, westward relative migration of the Klamath Mountains province, and U–Pb ages of deposition, sediment sources, and spatial locations of Jurassic and younger, detrital zirconbearing clastic rock ...
Great Lakes tectonic zone
The Great Lakes tectonic zone is bounded by South Dakota at its tip and heads northeast to south of Duluth, Minnesota, then heads east through northern Wisconsin, Marquette, Michigan, and then trends more northeasterly to skim the northern-most shores of lakes Michigan and Huron before ending in the Sudbury, Ontario, Canada, area.During the Late Archean Era the Algoman orogeny added landmass to the Superior province by volcanic activity and continental collision along a boundary that stretches from present-day South Dakota, U.S., into the Lake Huron region near Sudbury, Ontario, Canada.This crustal boundary is the Great Lakes tectonic zone. It is 1,400 km (870 mi) long, and separates the older Archean gneissic terrane to the south from younger Late Archean greenstone-granite terrane to the north.The zone is characterized by active compression during the Algoman orogeny (about 2,700 million years ago), a pulling-apart (extensional) tectonics (2,450 to 2,100 million years ago), a second compression during the Penokean orogeny (1,900 to 1,850 million years ago), a second extension during Middle Proterozoic time (1,600 million years ago) and minor reactivation during Phanerozoic time (the past 500 million years).Collision began along the Great Lakes tectonic zone (GLTZ) with the Algoman mountain-building event and continued for tens of millions of years. During the formation of the GLTZ, the gneissic Minnesota River Valley subprovince was thrust up onto the Superior province's edge as it consumed the Superior province's oceanic crust. Fragmentation of the Kenorland supercontinent began 2,450 million years ago and was completed by 2,100 million years ago. The Wyoming province is the continental landmass that is hypothesized to have rifted away from the southern Superior province portion of Kenorland, before moving rapidly west and docking with the Laurentia supercontinent 1,850 to 1,715 million years ago. Sedimentation from the GLTZ-rifting environment continued into the Penokean orogeny, which is the next major tectonic event in the Great Lakes region. Several earthquakes have been documented in Minnesota, Michigan's Upper Peninsula and Sudbury in the last 120 years along the GLTZ.