Lower Continental Crust. - UCSB Earth Science
... OF CONTINENTAL CRUST Earth’s continental crust is widely believed to be andesitic to dacitic, with 57 to 66 wt% SiO2 (e.g., Rudnick & Gao 2003, 2014), distinct from mafic oceanic crust, with 48 to 52 wt% SiO2 , and from upper mantle residual peridotites, with <46 wt% SiO2 . Compared with oceanic crus ...
... OF CONTINENTAL CRUST Earth’s continental crust is widely believed to be andesitic to dacitic, with 57 to 66 wt% SiO2 (e.g., Rudnick & Gao 2003, 2014), distinct from mafic oceanic crust, with 48 to 52 wt% SiO2 , and from upper mantle residual peridotites, with <46 wt% SiO2 . Compared with oceanic crus ...
The Southern Mountains Zone, Isle of Rum, Scotland
... Zone sections, but cross-cutting intrusions and structural or stratigraphic uncertainties hinder extrapolation to others and to those in the Northern Marginal Zone. Our observations none the less confirm at least two major ignimbrite-forming eruptions in the Southern Mountains Zone, in contrast to t ...
... Zone sections, but cross-cutting intrusions and structural or stratigraphic uncertainties hinder extrapolation to others and to those in the Northern Marginal Zone. Our observations none the less confirm at least two major ignimbrite-forming eruptions in the Southern Mountains Zone, in contrast to t ...
Finite-frequency wave propagation through outer rise fault zones
... subduction [e.g., Ranero et al., 2003; Faccenda et al., 2009; Van Avendonk et al., 2011; Shillington et al., 2015]. Seismic-reflection images appear to show that outer rise faults can extend into the uppermost mantle [Ranero et al., 2003]. Numerical models support the existence of deep-cutting faults ...
... subduction [e.g., Ranero et al., 2003; Faccenda et al., 2009; Van Avendonk et al., 2011; Shillington et al., 2015]. Seismic-reflection images appear to show that outer rise faults can extend into the uppermost mantle [Ranero et al., 2003]. Numerical models support the existence of deep-cutting faults ...
Exploring for molybdenum in Quebec
... All porphyry-type deposits are formed at shallow crustal depths (probably 3–4 km or less). In the case of porphyry Mo deposits, most ore bodies lie just above or within the summit of an intrusive porphyritic or aplitic cupola. If the intrusion crops out over a large area, it is probable that the dep ...
... All porphyry-type deposits are formed at shallow crustal depths (probably 3–4 km or less). In the case of porphyry Mo deposits, most ore bodies lie just above or within the summit of an intrusive porphyritic or aplitic cupola. If the intrusion crops out over a large area, it is probable that the dep ...
Title K-feldspar sand-grain provenance in the Triassic
... Bank has been correlated with the Ketilidian mobile belt on the basis of geochronology (Morton and Taylor 1991), but isotopic data from Cenozoic basalts on the northern bank (Hitchen et al. 1997) suggest the basement here has an Archaean affinity, likely correlated with the North Atlantic Craton of ...
... Bank has been correlated with the Ketilidian mobile belt on the basis of geochronology (Morton and Taylor 1991), but isotopic data from Cenozoic basalts on the northern bank (Hitchen et al. 1997) suggest the basement here has an Archaean affinity, likely correlated with the North Atlantic Craton of ...
Dayem, K. E., G. A. Houseman, and P. Molnar (2009), Localization of shear along a lithospheric strength
... northern Tibet, one such example of localized strain, forms a major part of the boundary between the Tibetan plateau and the Tarim basin and accommodates strain resulting from convergence between India and Asia (Figure 1). Structural [Cowgill et al., 2000] and GPS [Zhang et al., 2007] data suggest t ...
... northern Tibet, one such example of localized strain, forms a major part of the boundary between the Tibetan plateau and the Tarim basin and accommodates strain resulting from convergence between India and Asia (Figure 1). Structural [Cowgill et al., 2000] and GPS [Zhang et al., 2007] data suggest t ...
Crooked River caldera - Oregon Department of Geology and Mineral
... corresponding calderas has been hindered by limited detailed regional geologic mapping. Regional workers have suggested that pyroclastic rocks within the John Day Formation were vented from a nascent West Cascade Range or were erupted near the eastern margin of the present-day Cascades (Robinson, 19 ...
... corresponding calderas has been hindered by limited detailed regional geologic mapping. Regional workers have suggested that pyroclastic rocks within the John Day Formation were vented from a nascent West Cascade Range or were erupted near the eastern margin of the present-day Cascades (Robinson, 19 ...
Orogens and slabs vs. their direction of subduction
... Subduction zones appear primarily controlled by the polarity of their direction, i.e., W-directed or E- to NNE-directed, probably due to the westward drift of the lithosphere relative to the asthenosphere. The decollement planes behave differently in the two end-members. In the W-directed subduction ...
... Subduction zones appear primarily controlled by the polarity of their direction, i.e., W-directed or E- to NNE-directed, probably due to the westward drift of the lithosphere relative to the asthenosphere. The decollement planes behave differently in the two end-members. In the W-directed subduction ...
Izu detachment hypothesis: A proposal of a unified cause for... event and the Tokai slow event
... 1984; Ukawa, 1991) because these predict smooth stress trajectories. On the contrary, Ida (1991) explained such a sudden change in stress regime by introducing the western and eastern Izu blocks; the western one is accommodating a simple shear due to differential subduction along the Suruga Trough, ...
... 1984; Ukawa, 1991) because these predict smooth stress trajectories. On the contrary, Ida (1991) explained such a sudden change in stress regime by introducing the western and eastern Izu blocks; the western one is accommodating a simple shear due to differential subduction along the Suruga Trough, ...
Rhenium^Osmium Isotope and Platinum
... anomaly studies show the intrusion extends northward for at least 250 km under younger cover where it becomes more laterally extensive (Fig. 1). The present exposure probably represents a thin, oblique slice through a much larger intrusion (Francis, 1994), with an estimated original volume in excess ...
... anomaly studies show the intrusion extends northward for at least 250 km under younger cover where it becomes more laterally extensive (Fig. 1). The present exposure probably represents a thin, oblique slice through a much larger intrusion (Francis, 1994), with an estimated original volume in excess ...
Petrology and Geochemistry of the Nipissing Gabbro
... A1.7 Sketch map showing relationships between lithologies at the roof of the Kerns Intrusion . . . . . . . . . . . . . . 59 A1.8a. Sketch map showing the locations of samples referred to in MRD 19. Englehart Intrusion (based on regional compilation maps) . . . . . . . . . . . . . . . . . . . . . . . ...
... A1.7 Sketch map showing relationships between lithologies at the roof of the Kerns Intrusion . . . . . . . . . . . . . . 59 A1.8a. Sketch map showing the locations of samples referred to in MRD 19. Englehart Intrusion (based on regional compilation maps) . . . . . . . . . . . . . . . . . . . . . . . ...
The Origin, Evolution and Present State of Subcontinental Lithosphere
... “delamination” beneath Tibet has been interpreted as a result of continental subduction. The latter mechanism has been also invoked to interpret the SCLM thinning beneath NCC as resulting from northward subduction of the Yangtze craton in the early Mesozoic as recorded by the exhumed Dabie-Sulu ultr ...
... “delamination” beneath Tibet has been interpreted as a result of continental subduction. The latter mechanism has been also invoked to interpret the SCLM thinning beneath NCC as resulting from northward subduction of the Yangtze craton in the early Mesozoic as recorded by the exhumed Dabie-Sulu ultr ...
Cascadia subducting plate fluids channelled to fore
... and earlier great earthquakes. Although there are still significant uncertainties, these constraints and several others are in general agreement. The Cascadia downdip limit is concluded to be thermally Figure 1. The locations of (1) the seismogenic zone downdip limit, limited to an unusually shallow ...
... and earlier great earthquakes. Although there are still significant uncertainties, these constraints and several others are in general agreement. The Cascadia downdip limit is concluded to be thermally Figure 1. The locations of (1) the seismogenic zone downdip limit, limited to an unusually shallow ...
The birth of the Rheic Ocean — Early Palaeozoic subsidence
... epicontinental sediments, which have been previously interpreted as having been deposited on the rifting Gondwana margin (Franke, 1992). Related extensional faults were discussed by Zulauf et al. (1997), and the deposition of Cambrian epicontinental sediments was accompanied by contemporaneous rifti ...
... epicontinental sediments, which have been previously interpreted as having been deposited on the rifting Gondwana margin (Franke, 1992). Related extensional faults were discussed by Zulauf et al. (1997), and the deposition of Cambrian epicontinental sediments was accompanied by contemporaneous rifti ...
Iron Oxide Copper-Gold Deposits: Geology, Space
... magnetite and/or hematite; (4) Fe oxides with Fe/Ti greater those in most igneous rocks and bulk crust; and (5) no clear spatial associations with igneous intrusions as, for example, displayed by porphyry and skarn ore deposits. IOCG deposits commonly have a space-time association with Kiruna-type a ...
... magnetite and/or hematite; (4) Fe oxides with Fe/Ti greater those in most igneous rocks and bulk crust; and (5) no clear spatial associations with igneous intrusions as, for example, displayed by porphyry and skarn ore deposits. IOCG deposits commonly have a space-time association with Kiruna-type a ...
Laramide crustal thickening event in the Rocky Mountain Foreland
... huge regional "root" that now supports the foreland and Great Plains at up to 2 km average elevation. The same shear tractions that Brewer et al. [1980] invoked to cause the Wind River range overthrust may also have dragged and transported ductile lower crust from within the Sevier orogen in the Sou ...
... huge regional "root" that now supports the foreland and Great Plains at up to 2 km average elevation. The same shear tractions that Brewer et al. [1980] invoked to cause the Wind River range overthrust may also have dragged and transported ductile lower crust from within the Sevier orogen in the Sou ...
The Picuris Formation - New Mexico Geological Society
... mapping. Additional radiometric age estimates and sedimentologic analyses are currently underway, and are expected to add to the developing picture of this little-studied formation. GEOLOGIC SETTING AND BACKGROUND The Picuris Mountains of north-central New Mexico are a Proterozoic-cored uplift that ...
... mapping. Additional radiometric age estimates and sedimentologic analyses are currently underway, and are expected to add to the developing picture of this little-studied formation. GEOLOGIC SETTING AND BACKGROUND The Picuris Mountains of north-central New Mexico are a Proterozoic-cored uplift that ...
Continental geotherm and the evolution of rifted margins
... base of cratonic lithosphere from heat flow models (Jaupart et al., 1998), expected values of thermal conductivity and heat production in the mantle, and heat flow across the cratonic Moho (Jaupart and Mareschal, 1999). More globally, variations in the depths to the 410 and 660 km discontinuities im ...
... base of cratonic lithosphere from heat flow models (Jaupart et al., 1998), expected values of thermal conductivity and heat production in the mantle, and heat flow across the cratonic Moho (Jaupart and Mareschal, 1999). More globally, variations in the depths to the 410 and 660 km discontinuities im ...
Nitrogen concentration and d N of altered oceanic crust obtained on
... Knowledge of the subduction input flux of nitrogen (N) in altered oceanic crust (AOC) is critical in any attempt to massbalance N across arc-trench systems on a global or individual-margin basis. We have employed sealed-tube, carrier-gas-based methods to examine the N concentrations and isotopic comp ...
... Knowledge of the subduction input flux of nitrogen (N) in altered oceanic crust (AOC) is critical in any attempt to massbalance N across arc-trench systems on a global or individual-margin basis. We have employed sealed-tube, carrier-gas-based methods to examine the N concentrations and isotopic comp ...
Geodynpub_files/Boutelier, Chemenda, 2011
... that the asthenosphere exerts a small shear traction on the base of the lithosphere. This traction can thus be neglected if we focus our interest on the solid interaction of the plates in the subduction zone because the action of such small shear traction on a limited area such as the subduction zon ...
... that the asthenosphere exerts a small shear traction on the base of the lithosphere. This traction can thus be neglected if we focus our interest on the solid interaction of the plates in the subduction zone because the action of such small shear traction on a limited area such as the subduction zon ...
Full Text - Tectonic Analysis
... eastern South Caribbean Plate Boundary Zone (ESCPBZ), the last 10 million years of evolution at this boundary have occurred under a regime of E-W dextral shear. It was only prior to 10 Ma (end Middle Miocene) that these two plates underwent dextral oblique collision. Third, the collision prior to 10 ...
... eastern South Caribbean Plate Boundary Zone (ESCPBZ), the last 10 million years of evolution at this boundary have occurred under a regime of E-W dextral shear. It was only prior to 10 Ma (end Middle Miocene) that these two plates underwent dextral oblique collision. Third, the collision prior to 10 ...
GEOLOGIC STRUCTURE OF THE UPPERMOST OCEANIC CRUST
... diminishes across the very narrow (few kilometers wide) zone of lava accumulation and dike intrusion at the ridge axis. This type of crustal structure is in accord with some existing models of spreading but augments these idealized views with more realistic geological complexity. ...
... diminishes across the very narrow (few kilometers wide) zone of lava accumulation and dike intrusion at the ridge axis. This type of crustal structure is in accord with some existing models of spreading but augments these idealized views with more realistic geological complexity. ...
The Palaeozoic of the Southern Alps
... age. In the western Carnic Alps and in the Brixen Phyllite Complex even older rocks occur the age of which, however, is not precisely known. Presumably, the oldest part of this sequence may be attributed to the Cambrian or Lower Ordovician. In the Austrian part of the Southern Alps the Ordovician su ...
... age. In the western Carnic Alps and in the Brixen Phyllite Complex even older rocks occur the age of which, however, is not precisely known. Presumably, the oldest part of this sequence may be attributed to the Cambrian or Lower Ordovician. In the Austrian part of the Southern Alps the Ordovician su ...
The Dynamic Earth - Betavak-NLT
... format on the Internet. For many parts of the module ‘The Dynamic Earth’, the context is Dutch (e.g. assignment 2.1 “when did the Netherlands lie on the equator?”) Someone from abroad who wants to use (parts of) this module can adapt the context so that it is suitable for to his or her own location ...
... format on the Internet. For many parts of the module ‘The Dynamic Earth’, the context is Dutch (e.g. assignment 2.1 “when did the Netherlands lie on the equator?”) Someone from abroad who wants to use (parts of) this module can adapt the context so that it is suitable for to his or her own location ...
Geomorphic constraints on fault throw rates and linkage times
... where the coefficient UK n ¼ k s, the steepness index of the channel, which depends on uplift rate (and K). As the steepness index and concavity (m/n) covary, normalized steepness ksn is calculated using a reference concavity [Wobus et al., 2006a]. Normalized steepness indices have shown a solid corr ...
... where the coefficient UK n ¼ k s, the steepness index of the channel, which depends on uplift rate (and K). As the steepness index and concavity (m/n) covary, normalized steepness ksn is calculated using a reference concavity [Wobus et al., 2006a]. Normalized steepness indices have shown a solid corr ...
Algoman orogeny
The Algoman orogeny, known as the Kenoran orogeny in Canada, was an episode of mountain-building (orogeny) during the Late Archean Eon that involved repeated episodes of continental collisions, compressions and subductions. The Superior province and the Minnesota River Valley terrane collided about 2,700 to 2,500 million years ago. The collision folded the Earth's crust and produced enough heat and pressure to metamorphose the rock. Blocks were added to the Superior province along a 1,200 km (750 mi) boundary that stretches from present-day eastern South Dakota into the Lake Huron area. The Algoman orogeny brought the Archaen Eon to a close, about 2,500 million years ago; it lasted less than 100 million years and marks a major change in the development of the earth’s crust.The Canadian shield contains belts of metavolcanic and metasedimentary rocks formed by the action of metamorphism on volcanic and sedimentary rock. The areas between individual belts consist of granites or granitic gneisses that form fault zones. These two types of belts can be seen in the Wabigoon, Quetico and Wawa subprovinces; the Wabigoon and Wawa are of volcanic origin and the Quetico is of sedimentary origin. These three subprovinces lie linearly in southwestern- to northeastern-oriented belts about 140 km (90 mi) wide on the southern portion of the Superior Province.The Slave province and portions of the Nain province were also affected. Between about 2,000 and 1,700 million years ago these combined with the Sask and Wyoming cratons to form the first supercontinent, the Kenorland supercontinent.