Rio Grande rift: Problems and Perspectives
... by large crustal blocks separated by steeply dipping normal faults. In central New Mexico, west of Albuquerque and Socorro, this region is more than 200 km in width, extending southwestward across the physiographic Colorado Plateau to Springerville, Arizona, and perhaps farther (Baldridge and others ...
... by large crustal blocks separated by steeply dipping normal faults. In central New Mexico, west of Albuquerque and Socorro, this region is more than 200 km in width, extending southwestward across the physiographic Colorado Plateau to Springerville, Arizona, and perhaps farther (Baldridge and others ...
Global plume-fed asthenosphere flow
... asthenosphere also plays an important role in mantle flow due to its buoyancy and low viscosity. Asthenospheric flow can transport chemical features from a source hotspot to a mid-ocean ridge, thereby linking geophysical flow to geochemical observations. Alongridge migration of asthenosphere was fir ...
... asthenosphere also plays an important role in mantle flow due to its buoyancy and low viscosity. Asthenospheric flow can transport chemical features from a source hotspot to a mid-ocean ridge, thereby linking geophysical flow to geochemical observations. Alongridge migration of asthenosphere was fir ...
The heavy noble gas composition of the depleted MORB mantle
... The extent to which the noble gas composition of popping rock is representative of the depleted MORB mantle, however, is not clear. This is because the sample is highly enriched in trace elements (La/SmN ¼2.1; Dosso et al., 1991, 1993) compared to the normal depleted MORBs (N-MORBs; La/SmN r1) that ...
... The extent to which the noble gas composition of popping rock is representative of the depleted MORB mantle, however, is not clear. This is because the sample is highly enriched in trace elements (La/SmN ¼2.1; Dosso et al., 1991, 1993) compared to the normal depleted MORBs (N-MORBs; La/SmN r1) that ...
Crystal preferred orientation of an amphibole experimentally
... NATURE COMMUNICATIONS | 6:6586 | DOI: 10.1038/ncomms7586 | www.nature.com/naturecommunications ...
... NATURE COMMUNICATIONS | 6:6586 | DOI: 10.1038/ncomms7586 | www.nature.com/naturecommunications ...
Chemical Geodynamics - Woods Hole Oceanographic Institution
... that is heterogeneous on a kilometer or smaller scale but homogeneous on a 20-100 km scale. At the other extreme (large scale lengths), there appear to be large areas of the Earth that, in planform, show coherent and characteristic isotopic signatures (Dupre & Allegre 1983). One ofthese, termed the ...
... that is heterogeneous on a kilometer or smaller scale but homogeneous on a 20-100 km scale. At the other extreme (large scale lengths), there appear to be large areas of the Earth that, in planform, show coherent and characteristic isotopic signatures (Dupre & Allegre 1983). One ofthese, termed the ...
Geology
... continental margin can be inferred from the synrift and postrift stratigraphy. In the northern Appalachians, the Iapetan rift succession displays conspicuous along-strike variations in thickness, age, and depositional environment that strikingly match the modeled stratigraphic characteristics for lo ...
... continental margin can be inferred from the synrift and postrift stratigraphy. In the northern Appalachians, the Iapetan rift succession displays conspicuous along-strike variations in thickness, age, and depositional environment that strikingly match the modeled stratigraphic characteristics for lo ...
Caledonian igneous rocks of Great Britain
... result of the Caledonian Orogeny (Figure 1.1). There is at present no agreed definition of the term ‘Caledonian’. It has, for example, been used universally to describe the whole of the Caledonian mountain belt of Upper Proterozoic to middle Palaeozoic rocks (the Caledonides) which, prior to the mor ...
... result of the Caledonian Orogeny (Figure 1.1). There is at present no agreed definition of the term ‘Caledonian’. It has, for example, been used universally to describe the whole of the Caledonian mountain belt of Upper Proterozoic to middle Palaeozoic rocks (the Caledonides) which, prior to the mor ...
Geological Activity from Plate Tectonics Processes
... So many natural disasters occur because of plate tectonics processes. By using what we know about plate tectonics we can understand where most earthquakes and volcanic eruptions will strike. We can know where to look for many types of mineral deposits. The scar in this satellite image is of the San ...
... So many natural disasters occur because of plate tectonics processes. By using what we know about plate tectonics we can understand where most earthquakes and volcanic eruptions will strike. We can know where to look for many types of mineral deposits. The scar in this satellite image is of the San ...
Chapter 20: Anorthosites
... Figure 20.2. Model for the generation of Massif-type anorthosites. a. Mantle-derived magma underplates the crust as it becomes density equilibrated. b. Crystallization of mafic phases (which sink), and partial melting of the crust above the ponded magma. The melt becomes enriched in Al and Fe/Mg. c. ...
... Figure 20.2. Model for the generation of Massif-type anorthosites. a. Mantle-derived magma underplates the crust as it becomes density equilibrated. b. Crystallization of mafic phases (which sink), and partial melting of the crust above the ponded magma. The melt becomes enriched in Al and Fe/Mg. c. ...
pdf version - Berkeley Seismological Laboratory
... of geophysical measurements provides the most direct estimate of melt production at mid-ocean ridges. However, there are several challenges for this observation-based method, including: 1. This method is limited by the preservation of old oceanic crust. The oldest seafloor is 180 Ma, and this method ...
... of geophysical measurements provides the most direct estimate of melt production at mid-ocean ridges. However, there are several challenges for this observation-based method, including: 1. This method is limited by the preservation of old oceanic crust. The oldest seafloor is 180 Ma, and this method ...
ch 4
... 40 million years in age, with most falling between 50 and 45 million years ago. Most (but not all) of these plutons appear to have intruded along fault zones, shear zones or other tectonic features. They characteristically rose to shallow depths, and were frequently accompanied by surface volcanism. ...
... 40 million years in age, with most falling between 50 and 45 million years ago. Most (but not all) of these plutons appear to have intruded along fault zones, shear zones or other tectonic features. They characteristically rose to shallow depths, and were frequently accompanied by surface volcanism. ...
MAJOR-ELEMENT CHEMISTRY OF PLUTONIC ROCK SUITES
... 1971): (1) at ocean--ocean plate boundaries where oceanic lithosphere is subducted beneath oceanic lithosphere; (2) at ocean--continent plate boundaries where oceanic lithosphere is subducted beneath continental lithosphere; and (3) at continent--continent collision boundaries. In the last case, sub ...
... 1971): (1) at ocean--ocean plate boundaries where oceanic lithosphere is subducted beneath oceanic lithosphere; (2) at ocean--continent plate boundaries where oceanic lithosphere is subducted beneath continental lithosphere; and (3) at continent--continent collision boundaries. In the last case, sub ...
Chapter 4 Intrusive Igneous Rocks
... Mafic dykes are mostly of basaltic andesite composition but range from basalt to andesite. On Ma Wan and at Tsing Chau Tsai, melanocratic enclaves within quartzphyric rhyolite dykes are dacitic in composition and similar to the melanocratic margins of composite dykes. Whereas these dacitic dykes are ...
... Mafic dykes are mostly of basaltic andesite composition but range from basalt to andesite. On Ma Wan and at Tsing Chau Tsai, melanocratic enclaves within quartzphyric rhyolite dykes are dacitic in composition and similar to the melanocratic margins of composite dykes. Whereas these dacitic dykes are ...
as a PDF
... reference frame because the motions of the Americas are smoothest in this reference frame, and because it does not differ significantly, at least since c. 90 Ma, from more recent ‘moving hot spot’ reference frames. The Caribbean oceanic lithosphere has moved little relative to the hot spots in the C ...
... reference frame because the motions of the Americas are smoothest in this reference frame, and because it does not differ significantly, at least since c. 90 Ma, from more recent ‘moving hot spot’ reference frames. The Caribbean oceanic lithosphere has moved little relative to the hot spots in the C ...
Extensional troughs in the Caloris Basin of Mercury
... limit of zero rigidity, equation 2 results in the usual isostatic equation, as required. Given the deflection w(k), the surface stresses may be calculated using the approach outlined in Comer et al. (1985, their Appendix B), taking the elastic limit. There is an inconsistency arising from the fact t ...
... limit of zero rigidity, equation 2 results in the usual isostatic equation, as required. Given the deflection w(k), the surface stresses may be calculated using the approach outlined in Comer et al. (1985, their Appendix B), taking the elastic limit. There is an inconsistency arising from the fact t ...
Upper mantle velocity-temperature conversion and composition
... heat flow are less than the uncertainty on the heat flow estimates (2 mW m2) and cannot be detected. [12] Using the systematics of heat flow and heat production distributions together with geological and geophysical constraints on the crustal structure, one may obtain estimates of the Moho heat flo ...
... heat flow are less than the uncertainty on the heat flow estimates (2 mW m2) and cannot be detected. [12] Using the systematics of heat flow and heat production distributions together with geological and geophysical constraints on the crustal structure, one may obtain estimates of the Moho heat flo ...
The crustal structure of the southern Caspian region
... structure whose western boundary is a relatively narrow zone across which the crust thins rapidly (~20 km thinning over a 100 km zone) and whose eastern boundary has a more gradual change in crustal thickness (~20 km thinning over a 400 km zone). The velocity–depth profiles derived from the receiver ...
... structure whose western boundary is a relatively narrow zone across which the crust thins rapidly (~20 km thinning over a 100 km zone) and whose eastern boundary has a more gradual change in crustal thickness (~20 km thinning over a 400 km zone). The velocity–depth profiles derived from the receiver ...
STRIKE-SLIP AND OBLIQUE
... respectively). P shears also form an en échelon array contemporaneous with R shears or later as links between R shears. P-shears are contractional and accommodate fault parallel shortening as shearing proceeds. They are less common as R and R’ shears and may require more displacement to form. As for ...
... respectively). P shears also form an en échelon array contemporaneous with R shears or later as links between R shears. P-shears are contractional and accommodate fault parallel shortening as shearing proceeds. They are less common as R and R’ shears and may require more displacement to form. As for ...
Hotspots and Melting anomalies - Earth and Environmental Sciences
... topographic swells, distinct radiogenic isotope characteristics, flood basalt events, and ageprogressive volcanism, consistent with the movement of plates over relatively fixed point sources of magma. We classify at least 13 chains as having long-lived (>50 Myr) age progressive volcanism, at least 8 ...
... topographic swells, distinct radiogenic isotope characteristics, flood basalt events, and ageprogressive volcanism, consistent with the movement of plates over relatively fixed point sources of magma. We classify at least 13 chains as having long-lived (>50 Myr) age progressive volcanism, at least 8 ...
Tectonic wedging along the rear of the offshore Taiwan accretionary
... detailed analysis of this feature is beyond the scope of this study. A westward decrease in stratigraphic thickness causes an increase in bedding dip from 5j to 30j at greater depths. We follow the seismic sequence designation of Hirtzel (1996) to study the geometry of the youngest to the oldest str ...
... detailed analysis of this feature is beyond the scope of this study. A westward decrease in stratigraphic thickness causes an increase in bedding dip from 5j to 30j at greater depths. We follow the seismic sequence designation of Hirtzel (1996) to study the geometry of the youngest to the oldest str ...
Earth and Planetary Science
... inadequate for investigating the spatial variations in plate bending. In this paper, we present a new approach in identifying the deformed shape of a bending plate. Instead of using seafloor bathymetry directly, we conduct the analysis in two steps: First, we calculated “non-isostatic” topography by ...
... inadequate for investigating the spatial variations in plate bending. In this paper, we present a new approach in identifying the deformed shape of a bending plate. Instead of using seafloor bathymetry directly, we conduct the analysis in two steps: First, we calculated “non-isostatic” topography by ...
Plate tectonics
Plate tectonics (from the Late Latin tectonicus, from the Greek: τεκτονικός ""pertaining to building"") is a scientific theory that describes the large-scale motion of Earth's lithosphere. This theoretical model builds on the concept of continental drift which was developed during the first few decades of the 20th century. The geoscientific community accepted the theory after the concepts of seafloor spreading were later developed in the late 1950s and early 1960s.The lithosphere, which is the rigid outermost shell of a planet (on Earth, the crust and upper mantle), is broken up into tectonic plates. On Earth, there are seven or eight major plates (depending on how they are defined) and many minor plates. Where plates meet, their relative motion determines the type of boundary; convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. The lateral relative movement of the plates typically varies from zero to 100 mm annually.Tectonic plates are composed of oceanic lithosphere and thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, subduction carries plates into the mantle; the material lost is roughly balanced by the formation of new (oceanic) crust along divergent margins by seafloor spreading. In this way, the total surface of the globe remains the same. This prediction of plate tectonics is also referred to as the conveyor belt principle. Earlier theories (that still have some supporters) propose gradual shrinking (contraction) or gradual expansion of the globe.Tectonic plates are able to move because the Earth's lithosphere has greater strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection. Plate movement is thought to be driven by a combination of the motion of the seafloor away from the spreading ridge (due to variations in topography and density of the crust, which result in differences in gravitational forces) and drag, with downward suction, at the subduction zones. Another explanation lies in the different forces generated by the rotation of the globe and the tidal forces of the Sun and Moon. The relative importance of each of these factors and their relationship to each other is unclear, and still the subject of much debate.