Telescoping of isotherms beneath the South Tibetan Detachment
... Series (GHS) schists and gneisses in the footwall to the South Tibetan Detachment System (STDS) have undergone extreme telescoping during penetrative flow associated with southward extrusion of the GHS. In the Rongbuk Valley, to the north of Mount Everest, we have made three vertical sampling travers ...
... Series (GHS) schists and gneisses in the footwall to the South Tibetan Detachment System (STDS) have undergone extreme telescoping during penetrative flow associated with southward extrusion of the GHS. In the Rongbuk Valley, to the north of Mount Everest, we have made three vertical sampling travers ...
Geodynamic models of Cordilleran orogens
... et al., 2006; Bianchi et al., 2013), which have been interpreted as fragments of detached continental lithosphere. In this contribution, we investigate the dynamics of lithosphere removal in Cordilleran orogens. Various mechanisms for removing lithosphere have been proposed for the central Andes (Fi ...
... et al., 2006; Bianchi et al., 2013), which have been interpreted as fragments of detached continental lithosphere. In this contribution, we investigate the dynamics of lithosphere removal in Cordilleran orogens. Various mechanisms for removing lithosphere have been proposed for the central Andes (Fi ...
The Geology of Lundy - Lundy Field Society
... Irving, RA, Schofield, AJ and Webster, CJ. Island Studies (1997). Bideford: Lundy Field Society ...
... Irving, RA, Schofield, AJ and Webster, CJ. Island Studies (1997). Bideford: Lundy Field Society ...
Acrobat PDF file - 1 Mb (text and Table 1)
... residual peridotite composition, melt migration features, plutonic rocks, and hydrothermal alteration along axis. Hypotheses for focused solid or liquid upwelling beneath ridge segments make specific predictions regarding the spatial variation of mantle lineation or the distribution of melt migratio ...
... residual peridotite composition, melt migration features, plutonic rocks, and hydrothermal alteration along axis. Hypotheses for focused solid or liquid upwelling beneath ridge segments make specific predictions regarding the spatial variation of mantle lineation or the distribution of melt migratio ...
evidence from Th, Sr and Pb isotope data for Tonga
... beneath the arc. Lavas from the southern (Kermadec) segment of the arc have relatively radiogenic Pb isotope compositions, which reflects a contribution from subducted sediment. In contrast, much of the Pb in Tonga lavas is derived from the altered oceanic crust in the subducting Pacific Plate, and ...
... beneath the arc. Lavas from the southern (Kermadec) segment of the arc have relatively radiogenic Pb isotope compositions, which reflects a contribution from subducted sediment. In contrast, much of the Pb in Tonga lavas is derived from the altered oceanic crust in the subducting Pacific Plate, and ...
Bedrock Geology of the High Peaks Region, Marcy Massif
... strata were never highly folded •..•••••• Grenville foliation was developed •••. in essentially horizontal strata under a heavy load of overlying material ••• under conditions of static metamorphism"(Miller, 1918, p. 66). We, in the 1970's and 'SO's can decipher at least four or five periods of fold ...
... strata were never highly folded •..•••••• Grenville foliation was developed •••. in essentially horizontal strata under a heavy load of overlying material ••• under conditions of static metamorphism"(Miller, 1918, p. 66). We, in the 1970's and 'SO's can decipher at least four or five periods of fold ...
Cordierite in felsic igneous rocks: a synthesis
... Cordierite is a characteristic mineral of many peraluminous felsic igneous rocks. A combination of T-P-X parameters, which overlap the stability conditions for felsic magmas, control its formation. Critical among these parameters are relatively low T, low P, and typically high (Mg+Fe2§ Mg/Fe2+, A/CN ...
... Cordierite is a characteristic mineral of many peraluminous felsic igneous rocks. A combination of T-P-X parameters, which overlap the stability conditions for felsic magmas, control its formation. Critical among these parameters are relatively low T, low P, and typically high (Mg+Fe2§ Mg/Fe2+, A/CN ...
structural geology of the western branch of the east african rift
... Flood volcanism was preceded by heating and mantle metasomatism along the asthenospherelithosphere boundary, which led to the emplacement of kimberlites in Achaean cratons surrounding the rift in the Eocene. The differences in volcanism and uplift/subsidence in the Eastern and Western branch, respec ...
... Flood volcanism was preceded by heating and mantle metasomatism along the asthenospherelithosphere boundary, which led to the emplacement of kimberlites in Achaean cratons surrounding the rift in the Eocene. The differences in volcanism and uplift/subsidence in the Eastern and Western branch, respec ...
High-Mg# andesitic lavas of the Shisheisky Complex, Northern
... 2007). These studies point to petrographic observations, such as reverse compositional zoning and dacitic melt inclusions in mafic phenocrysts, as evidence for a complex origin involving mixing and hybridization between basaltic melts from the mantle and felsic melts of crustal rocks. If correct, th ...
... 2007). These studies point to petrographic observations, such as reverse compositional zoning and dacitic melt inclusions in mafic phenocrysts, as evidence for a complex origin involving mixing and hybridization between basaltic melts from the mantle and felsic melts of crustal rocks. If correct, th ...
Thermal structure of the shallow upper mantle beneath Italy and
... and of the consequent widespread back-arc extension process started about 10–15 Ma ago (Tyrrhenian Sea) (Panza and Calcagnile, 1979; Royden and Burchfiel, 1989; Doglioni, 1991). The seismic models of the upper mantle structure in the Tyrrhenian Sea area indicate the presence of partial melting at sha ...
... and of the consequent widespread back-arc extension process started about 10–15 Ma ago (Tyrrhenian Sea) (Panza and Calcagnile, 1979; Royden and Burchfiel, 1989; Doglioni, 1991). The seismic models of the upper mantle structure in the Tyrrhenian Sea area indicate the presence of partial melting at sha ...
Flow and melting of a heterogeneous mantle: 2. Implications for a
... solutions are indistinguishable from the observed MORB compositions and thus do not require a chemically layered mantle. Focusing on these solutions, the implied range of (nonlayered) mean mantle compositions can satisfy the global Th and U budget if the upper-bound estimates for the content of thes ...
... solutions are indistinguishable from the observed MORB compositions and thus do not require a chemically layered mantle. Focusing on these solutions, the implied range of (nonlayered) mean mantle compositions can satisfy the global Th and U budget if the upper-bound estimates for the content of thes ...
Origin and consequences of western Mediterranean subduction
... 2012b]. Following marine magnetic anomaly constraints of the Bay of Biscay, almost all pre-Eocene AfricaEurope convergence in the Iberian segment was accommodated in the Pyrenees, and Africa-Iberia convergence slowly started around 85 Ma, becoming significant after ~45 Ma. In the second model, Iberia ...
... 2012b]. Following marine magnetic anomaly constraints of the Bay of Biscay, almost all pre-Eocene AfricaEurope convergence in the Iberian segment was accommodated in the Pyrenees, and Africa-Iberia convergence slowly started around 85 Ma, becoming significant after ~45 Ma. In the second model, Iberia ...
Early opening history of the North Atlantic — I. Structure
... (3) The Rockall Trough. The geophysical evidence available to date is consistent with a normal oceanic crustal structure for the Trough south of about 58”N, with the Moho at 12-14km (Scrutton 1972). Nevertheless, the Trough is assumed by Talwani & Eldholm to be underlain by subsided continental crus ...
... (3) The Rockall Trough. The geophysical evidence available to date is consistent with a normal oceanic crustal structure for the Trough south of about 58”N, with the Moho at 12-14km (Scrutton 1972). Nevertheless, the Trough is assumed by Talwani & Eldholm to be underlain by subsided continental crus ...
Antigorite Peridotite, Metaserpentinite, and other
... analysis. The assemblage antigorite^diopside^olivine formed and was stable in the mantle. In a Cr-magnetite dunite, olivine compositions span the range Fa9^3, and chlorite-rich pockets contain extraordinarily pure pyrope (Py94·4Alm5·5Gr0·1). The Cr-magnetite dunite is a product of prograde metamorph ...
... analysis. The assemblage antigorite^diopside^olivine formed and was stable in the mantle. In a Cr-magnetite dunite, olivine compositions span the range Fa9^3, and chlorite-rich pockets contain extraordinarily pure pyrope (Py94·4Alm5·5Gr0·1). The Cr-magnetite dunite is a product of prograde metamorph ...
Ar– Ar ages of intrusions in East Greenland: Rift-to
... revise the magmatic history of the central East Greenland margin and discuss the link to asymmetry of rift-todrift transition in the Northeast Atlantic and reconfiguration of oceanic spreading ridges over the Iceland mantle plume. 2. Geology and chronology background 2.1. Rifted margin structure Sou ...
... revise the magmatic history of the central East Greenland margin and discuss the link to asymmetry of rift-todrift transition in the Northeast Atlantic and reconfiguration of oceanic spreading ridges over the Iceland mantle plume. 2. Geology and chronology background 2.1. Rifted margin structure Sou ...
Defining the Himalayan Main Central Thrust in Nepal
... Himalayan structural geology is that recent workers have mapped the Main Central Thrust within the Greater Himalayan Sequence high-grade metamorphic sequence along several different structural levels. Some workers map the Main Central Thrust as coinciding with a lithological contact, others as coinc ...
... Himalayan structural geology is that recent workers have mapped the Main Central Thrust within the Greater Himalayan Sequence high-grade metamorphic sequence along several different structural levels. Some workers map the Main Central Thrust as coinciding with a lithological contact, others as coinc ...
Late Cretaceous–early Cenozoic tectonic evolution of
... et al., 2003). This point is critical, because it indicates that underthrusting of the PelonaOrocopia-Rand schists began at least 15 m.y. prior to the 75 Ma or younger initiation of slip on the Nacimiento fault. Hence, formation of the schists was at least in part a separate phenomenon from the juxt ...
... et al., 2003). This point is critical, because it indicates that underthrusting of the PelonaOrocopia-Rand schists began at least 15 m.y. prior to the 75 Ma or younger initiation of slip on the Nacimiento fault. Hence, formation of the schists was at least in part a separate phenomenon from the juxt ...
GEOLOGICAL SURVEY OF FINLAND Special Paper 48 2008 GTK
... Explanation Volume 1 covers the whole of southern Mozambique. Only in the northwestern corner of this mapping area, south of Manica, are Proterozoic rocks exposed, while by far the majority of the area is covered by Phanerozoic units, from Karoo sediments and volcanics to extensive Cretaceous – Tert ...
... Explanation Volume 1 covers the whole of southern Mozambique. Only in the northwestern corner of this mapping area, south of Manica, are Proterozoic rocks exposed, while by far the majority of the area is covered by Phanerozoic units, from Karoo sediments and volcanics to extensive Cretaceous – Tert ...
AusMoho: the variation of Moho depth in Australia
... Most of the receiver function studies (Fig. 3b) have been carried out using waveform matching methods for broad-band stations. Shibutani et al. (1996) made use of genetic algorithm inversion for waveform fitting of receiver functions to generate 1-D shear wave speed and Vp /Vs profiles for portable ...
... Most of the receiver function studies (Fig. 3b) have been carried out using waveform matching methods for broad-band stations. Shibutani et al. (1996) made use of genetic algorithm inversion for waveform fitting of receiver functions to generate 1-D shear wave speed and Vp /Vs profiles for portable ...
Primitive off-rift basalts from Iceland and Jan Mayen: Os
... that within the convecting upper mantle source for Atlantic MORB (e.g., Hémond et al., 1993; Hards et al., 1995; Fitton et al., 1997; Chauvel and Hémond, 2000; Skovgaard et al., 2001; Breddam, 2002; Fitton et al., 2003; Thirlwall et al., 2004; Kokfelt et al., 2006). In contrast, others have argued ...
... that within the convecting upper mantle source for Atlantic MORB (e.g., Hémond et al., 1993; Hards et al., 1995; Fitton et al., 1997; Chauvel and Hémond, 2000; Skovgaard et al., 2001; Breddam, 2002; Fitton et al., 2003; Thirlwall et al., 2004; Kokfelt et al., 2006). In contrast, others have argued ...
Miocene and Early Pliocene Epithermal Gold
... Numerous important Miocene and early Pliocene epithermal Au-Ag deposits are present in the northern Great Basin. Most deposits are spatially and temporally related to two magmatic assemblages: bimodal basaltrhyolite and western andesite. These magmatic assemblages are petrogenetic suites that reflec ...
... Numerous important Miocene and early Pliocene epithermal Au-Ag deposits are present in the northern Great Basin. Most deposits are spatially and temporally related to two magmatic assemblages: bimodal basaltrhyolite and western andesite. These magmatic assemblages are petrogenetic suites that reflec ...
Incipient shortening of a passive margin: the mechanical roles of
... m−1 K−1 ). Eq. (10) yields temperature profiles for different ages of oceanic lithosphere (Fig. 1). From these profiles and eqs (6) and (7), we obtain rheological profiles (Fig. 2a), assuming a thickness of 6 km for oceanic crust (Calmant & Cazenave 1987) and a strain rate of 10−14 s−1 . On the prof ...
... m−1 K−1 ). Eq. (10) yields temperature profiles for different ages of oceanic lithosphere (Fig. 1). From these profiles and eqs (6) and (7), we obtain rheological profiles (Fig. 2a), assuming a thickness of 6 km for oceanic crust (Calmant & Cazenave 1987) and a strain rate of 10−14 s−1 . On the prof ...
Tracing the evolving flux from the subducting plate in the Tonga
... variations in this flux should have a major effect on arc geochemistry. Hole et al. (1984), and more recently Plank and Langmuir (1993) and Johnson and Plank (1999), suggested that the REE characteristics of many arc lavas are derived from the sediments being subducted in the adjacent trench. In the ...
... variations in this flux should have a major effect on arc geochemistry. Hole et al. (1984), and more recently Plank and Langmuir (1993) and Johnson and Plank (1999), suggested that the REE characteristics of many arc lavas are derived from the sediments being subducted in the adjacent trench. In the ...
Seismic velocity structure of the rifted margin of the eastern Grand
... central Grand Banks. We therefore assume that the eastern rim of the Grand Banks stretched uniformly by 25%. Farther seaward, the continental crust tapers rapidly beneath the continental slope to 6 km thickness. In the distal margin we find a 60-km-wide zone with seismic velocities between 5.0 and ...
... central Grand Banks. We therefore assume that the eastern rim of the Grand Banks stretched uniformly by 25%. Farther seaward, the continental crust tapers rapidly beneath the continental slope to 6 km thickness. In the distal margin we find a 60-km-wide zone with seismic velocities between 5.0 and ...
Roberts et al., 2013, Basin Modeling
... break-up, leading to prediction of heat-flow history; •• identify (i) areas of stretched continental crust, (ii) areas of highly attenuated continental crust within the ocean–continent transition (OCT), (iii) the location of the continent–ocean boundary (COB), (iv) areas of oceanic crust; •• assess ...
... break-up, leading to prediction of heat-flow history; •• identify (i) areas of stretched continental crust, (ii) areas of highly attenuated continental crust within the ocean–continent transition (OCT), (iii) the location of the continent–ocean boundary (COB), (iv) areas of oceanic crust; •• assess ...
Baltic Shield
The Baltic Shield (sometimes referred to as the Fennoscandian Shield) is located in Fennoscandia (Norway, Sweden and Finland), northwest Russia and under the Baltic Sea. The Baltic Shield is defined as the exposed Precambrian northwest segment of the East European Craton. It is composed mostly of Archean and Proterozoic gneisses and greenstones which have undergone numerous deformations through tectonic activity (see Geology of Fennoscandia map [1]). The Baltic Shield contains the oldest rocks of the European continent. The lithospheric thickness is about 200-300 km. During the Pleistocene epoch, great continental ice sheets scoured and depressed the shield's surface, leaving a thin covering of glacial material and innumerable lakes and streams. The Baltic Shield is still rebounding today following the melting of the thick glaciers during the Quaternary Period.