An Investigation of the carbonatites of the Kaapvaal Craton and their
... 1.2 Aims and objectives The hypothesis presented by this work is that carbonatites occur in extensional tectonic settings and therefore carbonatite occurrence can be used to constrain an extensional setting for related occurrences. This work aims to consider the validity of the hypothesis by consid ...
... 1.2 Aims and objectives The hypothesis presented by this work is that carbonatites occur in extensional tectonic settings and therefore carbonatite occurrence can be used to constrain an extensional setting for related occurrences. This work aims to consider the validity of the hypothesis by consid ...
Some Thermal Constraints on Crustal
... We provide a model for the fractional crystallization of hydrous mantle-derived magma to form calc-alkaline plutons, based upon mass balance for geological examples of fractionation sequences in the lower continental crust. This is complemented by a thermal model for the heat budget obtained from a ...
... We provide a model for the fractional crystallization of hydrous mantle-derived magma to form calc-alkaline plutons, based upon mass balance for geological examples of fractionation sequences in the lower continental crust. This is complemented by a thermal model for the heat budget obtained from a ...
Nonvolcanic Seafloor Spreading and Corner
... Lamont-Doherty Earth Observatory, Columbia University, 58 Geochemistry Building, Palisades, New York 10964, USA ...
... Lamont-Doherty Earth Observatory, Columbia University, 58 Geochemistry Building, Palisades, New York 10964, USA ...
Unconventional Isotopes and Approaches
... Terrestrial peridotites have a mean δ56FeIRMM-14 of 0.00 ±0.11‰. Oceanic basalts average slightly heavier, δ56FeIRMM-14 = +0.11‰ ±0.03‰. This consistent with a small (∆56Fe ≈ -0.2‰) fractionation between olivine and silicate liquid during partial melting and fractional crystallization. Lunar basalts ...
... Terrestrial peridotites have a mean δ56FeIRMM-14 of 0.00 ±0.11‰. Oceanic basalts average slightly heavier, δ56FeIRMM-14 = +0.11‰ ±0.03‰. This consistent with a small (∆56Fe ≈ -0.2‰) fractionation between olivine and silicate liquid during partial melting and fractional crystallization. Lunar basalts ...
Subduction kinematics and dynamic constraints
... The kinematics of subduction zones shows a variety of settings that can provide clues for dynamic understandings. Two reference frames are used here to describe the simple 2D kinematics of subduction zones. In the first, the upper plate is assumed fixed, whereas in the second frame upper and lower p ...
... The kinematics of subduction zones shows a variety of settings that can provide clues for dynamic understandings. Two reference frames are used here to describe the simple 2D kinematics of subduction zones. In the first, the upper plate is assumed fixed, whereas in the second frame upper and lower p ...
The global range of subduction zone thermal structures from
... evaluated by van Keken et al. (2002) and Gerya et al. (2002). In general, younger (warmer) subducting plates possess higher predicted temperatures at a given pressure than do older plates (Fig. 3A), and slower convergence leads to higher temperatures for P < 2 GPa than does faster convergence (Fig. ...
... evaluated by van Keken et al. (2002) and Gerya et al. (2002). In general, younger (warmer) subducting plates possess higher predicted temperatures at a given pressure than do older plates (Fig. 3A), and slower convergence leads to higher temperatures for P < 2 GPa than does faster convergence (Fig. ...
Subduction kinematics and dynamic constraints
... The kinematics of subduction zones shows a variety of settings that can provide clues for dynamic understandings. Two reference frames are used here to describe the simple 2D kinematics of subduction zones. In the first, the upper plate is assumed fixed, whereas in the second frame upper and lower p ...
... The kinematics of subduction zones shows a variety of settings that can provide clues for dynamic understandings. Two reference frames are used here to describe the simple 2D kinematics of subduction zones. In the first, the upper plate is assumed fixed, whereas in the second frame upper and lower p ...
Plate dynamics, mantle structure and tectonic evolution of the
... credible. Using the analogy with ice rafting or sea-ice thrusting, where narrow strips on the edge of an ice sheet intrude and overlap the edge of an adjacent ice sheet, Wilson [1966] suggested that the Caribbean plate originally belonged to the Pacific plate and intruded the intra-American domain. ...
... credible. Using the analogy with ice rafting or sea-ice thrusting, where narrow strips on the edge of an ice sheet intrude and overlap the edge of an adjacent ice sheet, Wilson [1966] suggested that the Caribbean plate originally belonged to the Pacific plate and intruded the intra-American domain. ...
Peculiarities of roughness and thickness of oceanic crust in the
... important opportunity to improve our knowledge of ridge systematics. Thermal models of mid-ocean ridges imply a faster cooling of magma and therefore an increasing viscosity of the melt below slow-spreading ridges (Sleep & Rosendahl 1979). This effect would lead to a lower basalt productivity and a ...
... important opportunity to improve our knowledge of ridge systematics. Thermal models of mid-ocean ridges imply a faster cooling of magma and therefore an increasing viscosity of the melt below slow-spreading ridges (Sleep & Rosendahl 1979). This effect would lead to a lower basalt productivity and a ...
Chromium isotope fractionation during subduction
... almost exclusively as Cr(III) in rocks. After the advent of oxygenic photosynthesis, local and eventually global oxygenated environments passed a critical threshold required for Cr(III) oxidation to Cr(VI), in a process likely linked to manganese redox cycling (Eary and Rai, 1987; Fendorf and Zasosk ...
... almost exclusively as Cr(III) in rocks. After the advent of oxygenic photosynthesis, local and eventually global oxygenated environments passed a critical threshold required for Cr(III) oxidation to Cr(VI), in a process likely linked to manganese redox cycling (Eary and Rai, 1987; Fendorf and Zasosk ...
Lithospheric evolution of the Andean fold–thrust belt, Bolivia, and
... We combine geological and geophysical data to develop a generalized model for the lithospheric evolution of the central Andean plateau between 188 and 208 S from Late Cretaceous to present. By integrating geophysical results of upper mantle structure, crustal thickness, and composition with recently ...
... We combine geological and geophysical data to develop a generalized model for the lithospheric evolution of the central Andean plateau between 188 and 208 S from Late Cretaceous to present. By integrating geophysical results of upper mantle structure, crustal thickness, and composition with recently ...
Deep structure of the Baikal rift zone revealed by joint inversion of
... [6] Previous studies in the Baikal rift zone have led to contrasting interpretations regarding its deep structure and the driving mechanisms. In their teleseismic study, Gao et al. [1994] proceed to a downward projection, assuming that the delay times arise from the geometry of the lithosphereasthen ...
... [6] Previous studies in the Baikal rift zone have led to contrasting interpretations regarding its deep structure and the driving mechanisms. In their teleseismic study, Gao et al. [1994] proceed to a downward projection, assuming that the delay times arise from the geometry of the lithosphereasthen ...
Crustal thickness variation in south
... 1995). The transition in crustal thickness north of the Alaska Range coincides with a major tectonostratigraphic boundary. Sharp changes in Moho depth have been noted elsewhere, such as the southern edge of the Qaidam Basin in Tibet, a major boundary with a Moho offset of 15–20 km (Zhu and Helmberge ...
... 1995). The transition in crustal thickness north of the Alaska Range coincides with a major tectonostratigraphic boundary. Sharp changes in Moho depth have been noted elsewhere, such as the southern edge of the Qaidam Basin in Tibet, a major boundary with a Moho offset of 15–20 km (Zhu and Helmberge ...
Mapping the Moho Across the Northern and Central Apennine
... Abstract. Waveforms of seismic events occurred at epicentral distances ranging from 30◦ to 90◦ , and recorded by 3-component stations installed in peninsular Italy and in eastern Sicily, were analyzed using the receiver function technique. Receiver functions are time series where the arrivals of P-t ...
... Abstract. Waveforms of seismic events occurred at epicentral distances ranging from 30◦ to 90◦ , and recorded by 3-component stations installed in peninsular Italy and in eastern Sicily, were analyzed using the receiver function technique. Receiver functions are time series where the arrivals of P-t ...
Mantle-derived magmas and magmatic Ni-Cu-(PGE) deposits
... Magmatic Fe-Ni-Cu ± platinum-group element (PGE) sulfide deposits form when mantlederived mafic and ultramafic magmas become saturated in sulfide and segregate immiscible sulfide liquid, commonly following interaction with crustal rocks. Although the metal contents of primary magmas influence ore co ...
... Magmatic Fe-Ni-Cu ± platinum-group element (PGE) sulfide deposits form when mantlederived mafic and ultramafic magmas become saturated in sulfide and segregate immiscible sulfide liquid, commonly following interaction with crustal rocks. Although the metal contents of primary magmas influence ore co ...
The Moho - EarthByte
... crust. It is identified as a first order discontinuity where the seismic P-wave velocity increases from typically 6.5–7.0 km/s to above 8.0 km/ s in continental lithosphere, and from about 6.8–7.3 km/s to above 7.6 km/s in oceanic lithosphere (e.g. White et al., 1992). The Moho is generally interprete ...
... crust. It is identified as a first order discontinuity where the seismic P-wave velocity increases from typically 6.5–7.0 km/s to above 8.0 km/ s in continental lithosphere, and from about 6.8–7.3 km/s to above 7.6 km/s in oceanic lithosphere (e.g. White et al., 1992). The Moho is generally interprete ...
Izu detachment hypothesis: A proposal of a unified cause for... event and the Tokai slow event
... Nishimura et al. (2001) assumed a creep dislocation source east of Kozushima at the northern end of the dike intrusion zone, whose moment corresponds to Mw 6.6–7. Figure 7(b) shows displacement vectors when the dislocation source of Yamaoka (2000) is added to the dike intrusion. Even if this point s ...
... Nishimura et al. (2001) assumed a creep dislocation source east of Kozushima at the northern end of the dike intrusion zone, whose moment corresponds to Mw 6.6–7. Figure 7(b) shows displacement vectors when the dislocation source of Yamaoka (2000) is added to the dike intrusion. Even if this point s ...
Sabzevar Ophiolite, NE Iran - The University of Texas at Dallas
... Elements (LILEs) and depleted in High Field Strength Elements (HFSEs), similar to SSZ-type magmatic rocks. They (except OIB-type lavas) have higher Th/Yb and plot far away from mantle array and are similar to arc-related rocks. Subordinate OIB-type lavas show Nb–Ta enrichment with high Light Rare Ea ...
... Elements (LILEs) and depleted in High Field Strength Elements (HFSEs), similar to SSZ-type magmatic rocks. They (except OIB-type lavas) have higher Th/Yb and plot far away from mantle array and are similar to arc-related rocks. Subordinate OIB-type lavas show Nb–Ta enrichment with high Light Rare Ea ...
(Cambridge: Cambridge University Press, 1988), 1-2, 37
... ocean floor to their current locations. This 'Drift' theory' conflicted with the two prevailing views. 'Permanentists' believed that continents and ocean basins had remained mostly unchanged in location and configuration since their formation. 'Contractionists' believed that due to the gradual contr ...
... ocean floor to their current locations. This 'Drift' theory' conflicted with the two prevailing views. 'Permanentists' believed that continents and ocean basins had remained mostly unchanged in location and configuration since their formation. 'Contractionists' believed that due to the gradual contr ...
Mantle plume
A mantle plume is a mechanism proposed in 1971 to explain volcanic regions of the earth that were not thought to be explicable by the then-new theory of plate tectonics. Some such volcanic regions lie far from tectonic plate boundaries, for example, Hawaii. Others represent unusually large-volume volcanism, whether on plate boundaries, e.g. Iceland, or basalt floods such as the Deccan or Siberian traps.A mantle plume is posited to exist where hot rock nucleates at the core-mantle boundary and rises through the Earth's mantle becoming a diapir in the Earth's crust. The currently active volcanic centers are known as ""hot spots"". In particular, the concept that mantle plumes are fixed relative to one another, and anchored at the core-mantle boundary, was thought to provide a natural explanation for the time-progressive chains of older volcanoes seen extending out from some such hot spots, such as the Hawaiian–Emperor seamount chain.The hypothesis of mantle plumes from depth is not universally accepted as explaining all such volcanism. It has required progressive hypothesis-elaboration leading to variant propositions such as mini-plumes and pulsing plumes. Another hypothesis for unusual volcanic regions is the ""Plate model"". This proposes shallower, passive leakage of magma from the mantle onto the Earth's surface where extension of the lithosphere permits it, attributing most volcanism to plate tectonic processes, with volcanoes far from plate boundaries resulting from intraplate extension.