Incipient shortening of a passive margin: the mechanical roles of
... 1 I N T RO D U C T I O N By definition, a passive margin is tectonically stable. It forms as a result of continental break-up, after prolonged rifting. During a later tectonic cycle the margin may become involved in collision or subduction; but before that, the only admissible style of deformation i ...
... 1 I N T RO D U C T I O N By definition, a passive margin is tectonically stable. It forms as a result of continental break-up, after prolonged rifting. During a later tectonic cycle the margin may become involved in collision or subduction; but before that, the only admissible style of deformation i ...
Bathymetry of Mariana trench-arc system and formation of the
... [2] The classic trench/arc/back arc geomorphology, so typical of the Mariana convergent plate boundary, changes markedly toward its southern end. The forearc narrows southward and the trench-arc distance decreases until the Mariana Ridge almost intersects the Mariana Trench near the island of Guam ( ...
... [2] The classic trench/arc/back arc geomorphology, so typical of the Mariana convergent plate boundary, changes markedly toward its southern end. The forearc narrows southward and the trench-arc distance decreases until the Mariana Ridge almost intersects the Mariana Trench near the island of Guam ( ...
The detrital record of orogenesis: A review of approaches and
... The sediment archive, of material eroded from an active tectonic region and stored in adjacent basins, can provide a valuable record of hinterland tectonism especially when information in the source region itself is obscured by later metamorphism or removed by tectonism or erosion. Using the sedimen ...
... The sediment archive, of material eroded from an active tectonic region and stored in adjacent basins, can provide a valuable record of hinterland tectonism especially when information in the source region itself is obscured by later metamorphism or removed by tectonism or erosion. Using the sedimen ...
Late Sveconorwegian monzonitic dykes in the Setesdalen areaof
... The plutons all contain a granitic and a monzonitic component, varying in proportions. In general, the relations between the two components are complex with highly irregular boundaries and contradicting age relationships, leading to the impression that they represent largely immiscible melts that we ...
... The plutons all contain a granitic and a monzonitic component, varying in proportions. In general, the relations between the two components are complex with highly irregular boundaries and contradicting age relationships, leading to the impression that they represent largely immiscible melts that we ...
Geophysical Journal International - E
... and their Iberian and Moroccan forelands. Crustal thickness values show strong lateral variations in the southern Iberia peninsula, ranging from ∼19 to ∼46 km. The Variscan foreland is characterized by a relatively flat Moho at ∼31 km depth, and an average v P /v S ratio of ∼1.72, similar to other V ...
... and their Iberian and Moroccan forelands. Crustal thickness values show strong lateral variations in the southern Iberia peninsula, ranging from ∼19 to ∼46 km. The Variscan foreland is characterized by a relatively flat Moho at ∼31 km depth, and an average v P /v S ratio of ∼1.72, similar to other V ...
Receiver function images of the Hellenic subduction zone and
... structures in the forearc that have been identified as nearly vertical margins of forearc slivers the seismicity extends down to the subduction interface (Meier et al., 2007; Becker et al., 2009; Brüstle et al., 2014). The seismicity of the plate contact is only incompletely recorded due to the limi ...
... structures in the forearc that have been identified as nearly vertical margins of forearc slivers the seismicity extends down to the subduction interface (Meier et al., 2007; Becker et al., 2009; Brüstle et al., 2014). The seismicity of the plate contact is only incompletely recorded due to the limi ...
Kimberlites and Lamproites: Primary Sources of Diamond
... phenocrysts in kimberlite or lamproite, and that their origins must lie within rocks sampled by these magmas during their ascent toward the crust. Additional evidence regarding the origin of diamonds has stemmed from studies of upper mantle-derived xenoliths and mineral inclusions In macrodiamonds. ...
... phenocrysts in kimberlite or lamproite, and that their origins must lie within rocks sampled by these magmas during their ascent toward the crust. Additional evidence regarding the origin of diamonds has stemmed from studies of upper mantle-derived xenoliths and mineral inclusions In macrodiamonds. ...
Igneous Environments
... Volcanic ash forms when dissolved gases in the magma expand and blow the magma apart into small fragments of volcanic glass. Any igneous rock that forms on the surface is called an extrusive rock because it forms from magma extruded onto the surface. More commonly, we simply call it a volcanic rock. ...
... Volcanic ash forms when dissolved gases in the magma expand and blow the magma apart into small fragments of volcanic glass. Any igneous rock that forms on the surface is called an extrusive rock because it forms from magma extruded onto the surface. More commonly, we simply call it a volcanic rock. ...
Differential preservation in the geologic record of intraoceanic arc
... to reconstruct paleogeography and plate motion, and to understand how continental crust is formed, recycled, and maintained through time. However, interpreting tectonic and sedimentary records from ancient terranes after arc–continent collision is complicated by preferential preservation of evidence ...
... to reconstruct paleogeography and plate motion, and to understand how continental crust is formed, recycled, and maintained through time. However, interpreting tectonic and sedimentary records from ancient terranes after arc–continent collision is complicated by preferential preservation of evidence ...
Fluid Processes in Subduction Zones Hydrous Minerals and
... • H2O and hydrous minerals weaken plate interface permitting subduction and plate tectonics to occur • H2O lowers melting temperature of mantle, generates explosive arc magmas • Fluids released by slab dehydration promote brittle behavior and may trigger earthquakes • Hydration structure, rheologica ...
... • H2O and hydrous minerals weaken plate interface permitting subduction and plate tectonics to occur • H2O lowers melting temperature of mantle, generates explosive arc magmas • Fluids released by slab dehydration promote brittle behavior and may trigger earthquakes • Hydration structure, rheologica ...
Telescoping of isotherms beneath the South Tibetan Detachment
... On the north side of the Mount Everest Massif two major detachments have been mapped in the sidewalls of the Rongbuk valley southwards to Changtse and Mount Everest, the upper brittle Qomolangma detachment (QD) and the lower ductile Lhotse detachment (LD), which merge towards the north into one larg ...
... On the north side of the Mount Everest Massif two major detachments have been mapped in the sidewalls of the Rongbuk valley southwards to Changtse and Mount Everest, the upper brittle Qomolangma detachment (QD) and the lower ductile Lhotse detachment (LD), which merge towards the north into one larg ...
Late Palaeozoic lam pro phyres and as so ci ated mafic subvolcanic
... Lamprophyric magmatism in the Sudetes, in the eastern part of the European Variscides, occurred during a period of post-collisional extension in the Carboniferous. The lamprophyres (minettes, vogesites, spessartites, kersantites) and associated mafic rocks (monzonites, micromonzodiorites) were empla ...
... Lamprophyric magmatism in the Sudetes, in the eastern part of the European Variscides, occurred during a period of post-collisional extension in the Carboniferous. The lamprophyres (minettes, vogesites, spessartites, kersantites) and associated mafic rocks (monzonites, micromonzodiorites) were empla ...
high-sulphidation, epithermal-style
... west–northwest, where massive to semimassive hematite schists are present. In the same area, vuggy quartz– hematite-rich rocks are developed on a small scale, and contain up to 1.36 g/t gold (Table 1). Drillhole data indicate that the host rocks of at least part of the hematite-rich zone have a mafi ...
... west–northwest, where massive to semimassive hematite schists are present. In the same area, vuggy quartz– hematite-rich rocks are developed on a small scale, and contain up to 1.36 g/t gold (Table 1). Drillhole data indicate that the host rocks of at least part of the hematite-rich zone have a mafi ...
Seismic velocity structure of the rifted margin of the eastern Grand
... [6] In the summer of 2000, we carried out a seismic data acquisition program termed ‘‘Studies of Continental Rifting and Extension on the Eastern Canadian shelf’’ (SCREECH). During this cruise, we collected three long profiles with both seismic reflection and refraction data across the margins of Gr ...
... [6] In the summer of 2000, we carried out a seismic data acquisition program termed ‘‘Studies of Continental Rifting and Extension on the Eastern Canadian shelf’’ (SCREECH). During this cruise, we collected three long profiles with both seismic reflection and refraction data across the margins of Gr ...
Unusual nickel and copper to noble
... Rh, Pt, Pd and Au (hereafter referred to as noble metals) analyses. Exploration programs rarely tind platinum deposits, but the noble-metal analy ses that are gathered can be useful in providing information on the geochemical cycle of these elements in different geological environments. This inform ...
... Rh, Pt, Pd and Au (hereafter referred to as noble metals) analyses. Exploration programs rarely tind platinum deposits, but the noble-metal analy ses that are gathered can be useful in providing information on the geochemical cycle of these elements in different geological environments. This inform ...
Mechanisms of continental subduction and exhumation of HP and
... from thermo-mechanical numerical models of convergent processes. This provides key validation of the inferred concepts of convergent dynamics and thermo-mechanical properties of oceanic and continental subduction zones (e.g., Yamato et al., 2007, 2008; Li and Gerya, 2009). However, both, the mechani ...
... from thermo-mechanical numerical models of convergent processes. This provides key validation of the inferred concepts of convergent dynamics and thermo-mechanical properties of oceanic and continental subduction zones (e.g., Yamato et al., 2007, 2008; Li and Gerya, 2009). However, both, the mechani ...
Rock Classification Scheme (BGS)
... deuteric, metasomatic or metamorphic processes. Igneous rocks include fragmental rocks formed as a direct result of volcanic processes. Arguments as to whether a rock is igneous, sedimentary or metamorphic become irrelevant in this context ii Classification is based on descriptive attributes, such a ...
... deuteric, metasomatic or metamorphic processes. Igneous rocks include fragmental rocks formed as a direct result of volcanic processes. Arguments as to whether a rock is igneous, sedimentary or metamorphic become irrelevant in this context ii Classification is based on descriptive attributes, such a ...
Mineralogy Petrology
... Let's look at the five parts of this definition: 1.) "Naturally occurring" means that synthetic compounds not known to occur in nature cannot have a mineral name. However, it may occur anywhere, other planets, deep in the earth, as long as there exists a natural sample to describe. 2.) "Homogeneous ...
... Let's look at the five parts of this definition: 1.) "Naturally occurring" means that synthetic compounds not known to occur in nature cannot have a mineral name. However, it may occur anywhere, other planets, deep in the earth, as long as there exists a natural sample to describe. 2.) "Homogeneous ...
Physics and Chemistry of Deep Continental Crust
... caused by decompression in the upwelling legs of solid-state mantle convection or by volatile flux melting in subduction zones. Owing to their low densities, liquids rise upward to form basaltic crust, which makes up most of the seafloor on Earth and the crusts of other rocky planets. Generating Ear ...
... caused by decompression in the upwelling legs of solid-state mantle convection or by volatile flux melting in subduction zones. Owing to their low densities, liquids rise upward to form basaltic crust, which makes up most of the seafloor on Earth and the crusts of other rocky planets. Generating Ear ...
volcanogenic massive sulphide deposits
... and Alaska, respectively (Peter and Scott, 1999). These are known as Besshi-type deposits from the type locality in the fore-deep accretionary wedge outboard of the Miocene ...
... and Alaska, respectively (Peter and Scott, 1999). These are known as Besshi-type deposits from the type locality in the fore-deep accretionary wedge outboard of the Miocene ...
Rudnick and Lee.fm - Cin
... compositions of peridotite residues are difficult to overprint by later processes, such as melt infiltration, which have such dramatic effects on other radiogenic isotope systems. For this reason, Os isotopes have proven useful in dating lithosphere formation, assuming that lithosphere formation goe ...
... compositions of peridotite residues are difficult to overprint by later processes, such as melt infiltration, which have such dramatic effects on other radiogenic isotope systems. For this reason, Os isotopes have proven useful in dating lithosphere formation, assuming that lithosphere formation goe ...
Geochemistry of Jurassic Oceanic Crust beneath
... and dikes or sills) is ~2 km thick, whereas crustal layer 3 (intrusives, primarily gabbros) has a thickness of ~2·5 km. The 15 my subaerial volcanic history of Gran Canaria (Schmincke, 1982; Hoernle & Schmincke, 1993a, 1993b) can be divided into two major cycles of volcanic activity: (1) Miocene or ...
... and dikes or sills) is ~2 km thick, whereas crustal layer 3 (intrusives, primarily gabbros) has a thickness of ~2·5 km. The 15 my subaerial volcanic history of Gran Canaria (Schmincke, 1982; Hoernle & Schmincke, 1993a, 1993b) can be divided into two major cycles of volcanic activity: (1) Miocene or ...
Tectonic activity recorded by multiple episodes of zircon growth: an
... a variegated series of Mesozoic marbles, schists and metavolcanics (Drift et al., 1978). During the Alpine orogeny these rocks experienced an Eocene high pressure metamorphism (M1) overprinted by OligoMiocene greenschist-amphibolite facies medium pressure metamorphism (M2). They form the lower plate ...
... a variegated series of Mesozoic marbles, schists and metavolcanics (Drift et al., 1978). During the Alpine orogeny these rocks experienced an Eocene high pressure metamorphism (M1) overprinted by OligoMiocene greenschist-amphibolite facies medium pressure metamorphism (M2). They form the lower plate ...
- Wiley Online Library
... Complete sediment offscraping does not appear to occur offshore Oregon. Seismically imaged seaward thrust fault vergence and decreased P-wave velocities suggest the presence of a subduction sediment channel 1 km in thickness under the coast [Gulick et al., 1998; Trehu et al., 2012; McNeill et al., ...
... Complete sediment offscraping does not appear to occur offshore Oregon. Seismically imaged seaward thrust fault vergence and decreased P-wave velocities suggest the presence of a subduction sediment channel 1 km in thickness under the coast [Gulick et al., 1998; Trehu et al., 2012; McNeill et al., ...
2014-Wannamaker-Casc.. - University of Alberta
... Complete sediment offscraping does not appear to occur offshore Oregon. Seismically imaged seaward thrust fault vergence and decreased P-wave velocities suggest the presence of a subduction sediment channel 1 km in thickness under the coast [Gulick et al., 1998; Trehu et al., 2012; McNeill et al., ...
... Complete sediment offscraping does not appear to occur offshore Oregon. Seismically imaged seaward thrust fault vergence and decreased P-wave velocities suggest the presence of a subduction sediment channel 1 km in thickness under the coast [Gulick et al., 1998; Trehu et al., 2012; McNeill et al., ...
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.