Crustal thickening in Gansu-Qinghai, lithospheric mantle subduction
... Typically, the foreland thrusts and décollements appear to splay from master thrusts that plunge at least 15–20 km down beneath the high ranges. Plio-Quaternary anticlinal ridges rising to more than 3000 m a.s.l. expose Palaeozoic metamorphic basement in their core. In general, the geology and topo ...
... Typically, the foreland thrusts and décollements appear to splay from master thrusts that plunge at least 15–20 km down beneath the high ranges. Plio-Quaternary anticlinal ridges rising to more than 3000 m a.s.l. expose Palaeozoic metamorphic basement in their core. In general, the geology and topo ...
Dipping reflector sequences in the vicinity of the continent
... on the Law of the Sea (1980) includes a number of proposed criteria for the delineation of the continental shelf of a coastal state, where its margin extends beyond 200 nautical miles from the continental baseline. One of these criteria, (para. 4(a), (i)), the so-called 'Irish formula' requires the ...
... on the Law of the Sea (1980) includes a number of proposed criteria for the delineation of the continental shelf of a coastal state, where its margin extends beyond 200 nautical miles from the continental baseline. One of these criteria, (para. 4(a), (i)), the so-called 'Irish formula' requires the ...
LOW RES
... and Uyeda, 1975]. Subduction zones are regions of intense earthquake activity, explosive volcanism, and complex mass transfer between the crust, mantle, hydrosphere, and atmosphere. In this contribution, I present subduction-zone thermal models that provide a framework for discussing the petrologica ...
... and Uyeda, 1975]. Subduction zones are regions of intense earthquake activity, explosive volcanism, and complex mass transfer between the crust, mantle, hydrosphere, and atmosphere. In this contribution, I present subduction-zone thermal models that provide a framework for discussing the petrologica ...
IODP Proposal Cover Sheet
... Mooney, 1995; Kelemen, 1995; Taylor, 1995; Rudnick, 1995). Since such intermediate igneous rocks typify magmatism at convergent plate boundaries, arcs may thus play a central role in continental crust formation (McLennan and Taylor, 1982). Yet the means by which the initial arc crust, composed of ma ...
... Mooney, 1995; Kelemen, 1995; Taylor, 1995; Rudnick, 1995). Since such intermediate igneous rocks typify magmatism at convergent plate boundaries, arcs may thus play a central role in continental crust formation (McLennan and Taylor, 1982). Yet the means by which the initial arc crust, composed of ma ...
Present-day crustal motion within the Tibetan Plateau inferred from
... Banerjee and Burgmann [2002] (red vectors). The rectangular box surrounding the Tibetan Plateau encloses the area concerned in this study. The yellow solid line in the northern plateau indicates the 420-km-long surface rupture of the 2001 Kokoxili Ms 8.1 earthquake. ...
... Banerjee and Burgmann [2002] (red vectors). The rectangular box surrounding the Tibetan Plateau encloses the area concerned in this study. The yellow solid line in the northern plateau indicates the 420-km-long surface rupture of the 2001 Kokoxili Ms 8.1 earthquake. ...
2.3. New Zealand – Primary Site 1. Background and Motivation
... the North, there is a rich record of active and ancient subduction margin processes, from subduction initiation through to fully developed, mature subduction systems. For simplicity, the seven SCD key questions (Section 2.1) can be organized into four overarching questions to be addressed at the New ...
... the North, there is a rich record of active and ancient subduction margin processes, from subduction initiation through to fully developed, mature subduction systems. For simplicity, the seven SCD key questions (Section 2.1) can be organized into four overarching questions to be addressed at the New ...
Miocene Landscape Evolution and Geomorphologic Controls on
... of the large Pascua-Lama and Veladero prospects at its northern extremity. In contrast, the major vein systems of the El Indio camp proper incorporate (Jannas et al., 1999; Bissig et al., 2001) both high- and intermediate-sulfidation facies (sensu Hedenquist et al., 2000). Mined and proven resources ...
... of the large Pascua-Lama and Veladero prospects at its northern extremity. In contrast, the major vein systems of the El Indio camp proper incorporate (Jannas et al., 1999; Bissig et al., 2001) both high- and intermediate-sulfidation facies (sensu Hedenquist et al., 2000). Mined and proven resources ...
The Geology of Lundy - Lundy Field Society
... intrigued geologists since the nineteenth century, as it is formed from rocks that are of a very different type and age to the nearby rocks of Devon and South Wales. It is formed mainly of granite (a coarse-grained igneous rock, composed of the minerals feldspar and quartz, often with biotite and am ...
... intrigued geologists since the nineteenth century, as it is formed from rocks that are of a very different type and age to the nearby rocks of Devon and South Wales. It is formed mainly of granite (a coarse-grained igneous rock, composed of the minerals feldspar and quartz, often with biotite and am ...
alps vs apennines - Dipartimento di Scienze della Terra
... promontory to the Guadalquivir basin. Similarly to the Alps, the Betics show low dip foreland monocline, high elevation, widespread outcrops of basement rocks, highpressure metamorphism, etc.. For these reasons they can be reasonably considered to be part of the same belt. Analyzing the Atlantic exa ...
... promontory to the Guadalquivir basin. Similarly to the Alps, the Betics show low dip foreland monocline, high elevation, widespread outcrops of basement rocks, highpressure metamorphism, etc.. For these reasons they can be reasonably considered to be part of the same belt. Analyzing the Atlantic exa ...
Ore Bin / Oregon Geology magazine / journal
... Columbia Plateau; BM, Blue Mountains; HLP, High Lava Plains; BR, Basin and Range; OU, Owyhee Uplands. (bottom) Enlarged central part of area shown in top figure with the distribution of the “western,” “southern,” and “eastern” facies after Robinson and others (1990) within the John Day Formation. So ...
... Columbia Plateau; BM, Blue Mountains; HLP, High Lava Plains; BR, Basin and Range; OU, Owyhee Uplands. (bottom) Enlarged central part of area shown in top figure with the distribution of the “western,” “southern,” and “eastern” facies after Robinson and others (1990) within the John Day Formation. So ...
Mechanisms for folding of high-grade rocks in extensional tectonic
... shortening, hence other criteria (such as pressure – temperature – time paths derived from detailed metamorphic studies) must be used in determining tectonic settings. Fold mechanisms unique to or of particular importance in extensional settings are identified. We also consider models for the origin ...
... shortening, hence other criteria (such as pressure – temperature – time paths derived from detailed metamorphic studies) must be used in determining tectonic settings. Fold mechanisms unique to or of particular importance in extensional settings are identified. We also consider models for the origin ...
Provenance characteristics of the Brumunddal sandstone in the Oslo
... to earliest Permian age (300 ± 1Ma, Corfu & Dahlgren 2008). Graben subsidence continued and large volumes of rhomb porphyry lava (latite) and minor basalt erupted through large fissure volcanoes. Also, thick volcanoclastic and sedimentary units were deposited during this stage. The composite Larvik ...
... to earliest Permian age (300 ± 1Ma, Corfu & Dahlgren 2008). Graben subsidence continued and large volumes of rhomb porphyry lava (latite) and minor basalt erupted through large fissure volcanoes. Also, thick volcanoclastic and sedimentary units were deposited during this stage. The composite Larvik ...
PDF
... continuing plate convergence following jamming of a subduction zone by buoyant crust. This results in regional compression, uplift and underthrusting that may yield a new subduction zone. Two subclasses of INSZ, transference and polarity reversal, are distinguished. Transference INSZ moves the new s ...
... continuing plate convergence following jamming of a subduction zone by buoyant crust. This results in regional compression, uplift and underthrusting that may yield a new subduction zone. Two subclasses of INSZ, transference and polarity reversal, are distinguished. Transference INSZ moves the new s ...
Tectono-stratigraphic framework of Neoproterozoic to Cambrian
... Stratigraphic, geochronologic, and geochemical patterns of Neoproterozoic to Cambrian sedimentary and volcanic rocks in Utah, Nevada, and SE Idaho record a dynamically evolving landscape along the North American Cordillera margin, which included: (1) initial development of intracratonic basins with ...
... Stratigraphic, geochronologic, and geochemical patterns of Neoproterozoic to Cambrian sedimentary and volcanic rocks in Utah, Nevada, and SE Idaho record a dynamically evolving landscape along the North American Cordillera margin, which included: (1) initial development of intracratonic basins with ...
Can slab melting be caused by flat subduction
... under normal subduction-zone thermal gradients. We propose an unusual mode of subduction known as flat subduction, occurring in -10% of the world’s convergent margins, that can produce the temperature and pressure conditions necessary for fusion of moderately old oceanic crust. Of the 10 known flat ...
... under normal subduction-zone thermal gradients. We propose an unusual mode of subduction known as flat subduction, occurring in -10% of the world’s convergent margins, that can produce the temperature and pressure conditions necessary for fusion of moderately old oceanic crust. Of the 10 known flat ...
Behaviour of high field strength elements in subduction zones
... source mass spectrometry (MC-ICPMS) using isotope dilution [31,32]. In combination with Hf –Nd isotope systematics, the HFSE ratios are used to constrain the mobility of HFSE during subduction zone processes. This approach exploits the near identical geochemical properties of the element pairs Nb – ...
... source mass spectrometry (MC-ICPMS) using isotope dilution [31,32]. In combination with Hf –Nd isotope systematics, the HFSE ratios are used to constrain the mobility of HFSE during subduction zone processes. This approach exploits the near identical geochemical properties of the element pairs Nb – ...
Evolution of the Eocene Galisteo Basin, north
... upper Galisteo, which is transitional into the pure volcaniclastics of the Espinaso. The lower Galisteo is characterized by coarse sandstone and green mudstone, the middle by sandstone, conglomerate and red mudstone, and the upper by mudstone and lenticular pebbly sandstone. Locally, the Galisteo co ...
... upper Galisteo, which is transitional into the pure volcaniclastics of the Espinaso. The lower Galisteo is characterized by coarse sandstone and green mudstone, the middle by sandstone, conglomerate and red mudstone, and the upper by mudstone and lenticular pebbly sandstone. Locally, the Galisteo co ...
Accreted oceanic terranes in Ecuador: Southern edge of the
... Near Guayaquil, the Piñón basement is overlain by a 30 to 200 m thick series of andesitic breccias, tuffs, and basaltic lavas (Las Orquídeas Mb, Reynaud et al. 1999; Fig. 6A). Although its geochemical signature is that of a primitive island arc, such a geodynamic setting is unlikely for two main rea ...
... Near Guayaquil, the Piñón basement is overlain by a 30 to 200 m thick series of andesitic breccias, tuffs, and basaltic lavas (Las Orquídeas Mb, Reynaud et al. 1999; Fig. 6A). Although its geochemical signature is that of a primitive island arc, such a geodynamic setting is unlikely for two main rea ...
Structure of the crust beneath Cameroon, West Africa, from the joint
... straints. To make the contribution of each data set to the joint least-squares misfit comparable, a normalization of the data set is necessary, and this is done using the number of data points and variance for each of the data sets. An influence factor is used to control the trade-off between fittin ...
... straints. To make the contribution of each data set to the joint least-squares misfit comparable, a normalization of the data set is necessary, and this is done using the number of data points and variance for each of the data sets. An influence factor is used to control the trade-off between fittin ...
Interpretation of an Aeromagnetic Survey of the Amchitka Island
... were examined for features that might be related to faulting. The survey was facilitated by data on the magnetic properties of 347 rock specimens collected from surface exposures and 216 from drill cores and by plots of 25 miles of ground magnetic traverse. The data on magnetic properties furnished ...
... were examined for features that might be related to faulting. The survey was facilitated by data on the magnetic properties of 347 rock specimens collected from surface exposures and 216 from drill cores and by plots of 25 miles of ground magnetic traverse. The data on magnetic properties furnished ...
Structure, Construction, and Emplacement of the Yosemite Valley
... study into several texturally and compositionally distinct units, whereas the Taft Granite is relatively homogeneous. Injection of a few large increments of magma or many increments intruded close in time ...
... study into several texturally and compositionally distinct units, whereas the Taft Granite is relatively homogeneous. Injection of a few large increments of magma or many increments intruded close in time ...
Cenozoic basin evolution of the Virgin Islands basin and Anegada
... (1990). This view shows well the asymmetrical, half-graben structure of the VIB with the steeper scarp of the St. Croix fault and the more gently sloped, largely unfaulted, and thinly sedimented basement surface on the north side of the basin (compare this view to the Shell seismic line shown in Fig ...
... (1990). This view shows well the asymmetrical, half-graben structure of the VIB with the steeper scarp of the St. Croix fault and the more gently sloped, largely unfaulted, and thinly sedimented basement surface on the north side of the basin (compare this view to the Shell seismic line shown in Fig ...
Synclinal-horst basins: examples from the southern Rio Grande rift
... synclinal-horst basins are rare, because horsts wide enough to develop broad synclines are uncommon in extensional terrains. Synclinal-horst basins may be most common along the margins of extensional terrains, where thicker, colder crust results in wider fault spacing. ...
... synclinal-horst basins are rare, because horsts wide enough to develop broad synclines are uncommon in extensional terrains. Synclinal-horst basins may be most common along the margins of extensional terrains, where thicker, colder crust results in wider fault spacing. ...
Geochemistry, origin, and U-Pb zircon ages of the Sierra Cuchillo
... Abstract—Eocene-Oligocene volcanism in New Mexico, Colorado, Arizona, and west Texas is commonly thought of as regional ash flow tuffs associated with Rio Grande rift calderas, although intermediate-composition volcanism also built stratovolcanos. The Sierra Cuchillo laccolith in Sierra County, New ...
... Abstract—Eocene-Oligocene volcanism in New Mexico, Colorado, Arizona, and west Texas is commonly thought of as regional ash flow tuffs associated with Rio Grande rift calderas, although intermediate-composition volcanism also built stratovolcanos. The Sierra Cuchillo laccolith in Sierra County, New ...
Geology of Hawaii - Duke Geological Laboratory
... supply of juicy basalt which, over the last million years or so has creates the overlapping outpourings of basalt that have built the Hawaiian shield volcano over 31,000’ from the base of the ocean floor (Figure 7) and have produced a broad arch (the Hawaiian arch) in the ocean. Growth of the island ...
... supply of juicy basalt which, over the last million years or so has creates the overlapping outpourings of basalt that have built the Hawaiian shield volcano over 31,000’ from the base of the ocean floor (Figure 7) and have produced a broad arch (the Hawaiian arch) in the ocean. Growth of the island ...
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.