Heterogeneous sources for Pleistocene lavas of Marie Byrd Land
... Mountains, resting depositionally upon frost-heaved periglacial surfaces and upon angular glacial boulders that mantle bedrock surfaces at low elevations. Many volcanic exposures consist of delicate tephra, cinder, and splatter forms, not evidently modified by wet-based glacial ice. In addition, a f ...
... Mountains, resting depositionally upon frost-heaved periglacial surfaces and upon angular glacial boulders that mantle bedrock surfaces at low elevations. Many volcanic exposures consist of delicate tephra, cinder, and splatter forms, not evidently modified by wet-based glacial ice. In addition, a f ...
Synthesis of Results From the CD-ROM Experiment
... oceanic terranes in the Paleoproterozoic. Crustal provinces with different geologic histories correspond to distinct mantle velocity domains, with profound mantle velocity contrasts associated with the ancient sutures. Typically, the transitions between the velocity domains are tabular, dipping, ext ...
... oceanic terranes in the Paleoproterozoic. Crustal provinces with different geologic histories correspond to distinct mantle velocity domains, with profound mantle velocity contrasts associated with the ancient sutures. Typically, the transitions between the velocity domains are tabular, dipping, ext ...
Geology and gold mineralization of mesozoic rocks in the Pine
... northwest and has mineralization and alteration similar to the Wheeler Mine, but it is further from the Wheeler Fault so that deposit has not undergone the same deformation as the Wheeler Mine deposit. The Wilson Mine was not studied ...
... northwest and has mineralization and alteration similar to the Wheeler Mine, but it is further from the Wheeler Fault so that deposit has not undergone the same deformation as the Wheeler Mine deposit. The Wilson Mine was not studied ...
of the American Cordillera
... extend over a northeast-trending area of approximately 900 km by 200 km (northern and central parts of this belt are shown in Fig. 3). Table 1 list selected plutonic rock analyses from the Kuskokwim Mountains. All igneous K-Ar age dates from the Kuskokwim Mountains range from 58 to 77 Ma while pluto ...
... extend over a northeast-trending area of approximately 900 km by 200 km (northern and central parts of this belt are shown in Fig. 3). Table 1 list selected plutonic rock analyses from the Kuskokwim Mountains. All igneous K-Ar age dates from the Kuskokwim Mountains range from 58 to 77 Ma while pluto ...
Nazca slab retreat versus compressional deformation in the central
... present-day direction). and a lithospheric age of the slab at the trench in the range 35 - 65 My. The only singular event during this period is the arrival of the Naxcaridge at the Peru-Chile trench at ca, 4 Ma, causing shallowing of subducIion in central Peru. During Urisperiod, the Andes have expe ...
... present-day direction). and a lithospheric age of the slab at the trench in the range 35 - 65 My. The only singular event during this period is the arrival of the Naxcaridge at the Peru-Chile trench at ca, 4 Ma, causing shallowing of subducIion in central Peru. During Urisperiod, the Andes have expe ...
6. The main mineralization types of the Arabian Shield
... assemblages resulting from the accretion of several volcanic-arcs. It is overlain to the east, north and south by a thick Phanerozoic sedimentary formation. The more than 500 U-Pb, Rb-Sr, Sm-Nd, K-Ar and Ar-Ar age determinations available for the Arabian Shield , both previously published (see synth ...
... assemblages resulting from the accretion of several volcanic-arcs. It is overlain to the east, north and south by a thick Phanerozoic sedimentary formation. The more than 500 U-Pb, Rb-Sr, Sm-Nd, K-Ar and Ar-Ar age determinations available for the Arabian Shield , both previously published (see synth ...
Subduction styles in the Precambrian
... et al. (2007a,b) argue for episodic plate tectonics in the Precambrian (alternating between the active and stagnant lid regimes (cf. Sleep, 2007)), where higher mantle temperatures result in lower lithospheric stresses, causing rapid pulses of subduction interspersed with periods of relative quiesce ...
... et al. (2007a,b) argue for episodic plate tectonics in the Precambrian (alternating between the active and stagnant lid regimes (cf. Sleep, 2007)), where higher mantle temperatures result in lower lithospheric stresses, causing rapid pulses of subduction interspersed with periods of relative quiesce ...
Ignimbrite flare-up and deformation in the southern Sierra Madre
... were performed we obtained consistent results; the isochron age calculated for the combined fractions of the duplicate experiments is also reported in Table 1. The majority of the samples yielded well-defined isochron ages which we take as the best estimate of the age for the sample; however, we had ...
... were performed we obtained consistent results; the isochron age calculated for the combined fractions of the duplicate experiments is also reported in Table 1. The majority of the samples yielded well-defined isochron ages which we take as the best estimate of the age for the sample; however, we had ...
The Subductability of Continental Lithosphere
... (1994) hypothesized about the settings in which subduction of continental derived materials would occur. These authors proposed active ocean ocean and ocean continent subduction zones as one potential environment, where significant amounts of sediments are being subducted into the mantle (e.g., Clif ...
... (1994) hypothesized about the settings in which subduction of continental derived materials would occur. These authors proposed active ocean ocean and ocean continent subduction zones as one potential environment, where significant amounts of sediments are being subducted into the mantle (e.g., Clif ...
Review Sheet - School of Ocean and Earth Science and Technology
... Know the layers of Earth defined by composition and by physical properties. How does the mechanical behavior of the lithosphere and asthenosphere differ? Know the properties and characteristics of Earth’s crust, mantle, and core. Know the commonly accepted origin of Earth’s magnetic field. Know what ...
... Know the layers of Earth defined by composition and by physical properties. How does the mechanical behavior of the lithosphere and asthenosphere differ? Know the properties and characteristics of Earth’s crust, mantle, and core. Know the commonly accepted origin of Earth’s magnetic field. Know what ...
Channel flow and the Himalayan-Tibetan orogen: a critical review
... orogen implies that extrusion of a wedge will lead to crustal thinning, unless there is some means of accreting new material into the wedge. Some form of channel flow would obviate the need for such thinning, as such models require that the crust thickens continuously until it weakens at depth, wher ...
... orogen implies that extrusion of a wedge will lead to crustal thinning, unless there is some means of accreting new material into the wedge. Some form of channel flow would obviate the need for such thinning, as such models require that the crust thickens continuously until it weakens at depth, wher ...
A Plate Tectonic Model for the Origin of Porphyry Copper Deposits
... andHess(1962) hasrecentlybeenfurtherdeveloped subcrustalbasic magrnas,slide past one another by Isacks, Oliver and Sykes (1968), Le Pichon along transform (horizontal shear) faults, and are (1968), McKenzieand Parker (1967) and Morgan destroyedat trench systemsby descent into the (1968), resultingin ...
... andHess(1962) hasrecentlybeenfurtherdeveloped subcrustalbasic magrnas,slide past one another by Isacks, Oliver and Sykes (1968), Le Pichon along transform (horizontal shear) faults, and are (1968), McKenzieand Parker (1967) and Morgan destroyedat trench systemsby descent into the (1968), resultingin ...
BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA
... paleochemistry of sea water and atmosphere. Several less conclusive lines of evidence now available suggest that the composition of both sea water and atmosphere may have varied somewhat during the past; but the geologic record indicates that these variations have probably been within relatively nar ...
... paleochemistry of sea water and atmosphere. Several less conclusive lines of evidence now available suggest that the composition of both sea water and atmosphere may have varied somewhat during the past; but the geologic record indicates that these variations have probably been within relatively nar ...
Steady state, erosional continuity, and the topography of landscapes
... channel morphology have primarily focused on regions with active uplift, where rock layers are often deformed and tilted from horizontal. However, a substantial percentage of Earth’s surface contains subhorizontal strata. Many of these settings also contain bedrock channels, with examples including ...
... channel morphology have primarily focused on regions with active uplift, where rock layers are often deformed and tilted from horizontal. However, a substantial percentage of Earth’s surface contains subhorizontal strata. Many of these settings also contain bedrock channels, with examples including ...
Paleogeography, Southwestern US
... probably resembled modern SE Asia. As various tectonic blocks collided, orogenic (mountain-building) events were generated. This view shows what the region may have looked like during these collisional events. About 1.1 Ga North America was part of the supercontinent Rodinia. The Southwest possibly ...
... probably resembled modern SE Asia. As various tectonic blocks collided, orogenic (mountain-building) events were generated. This view shows what the region may have looked like during these collisional events. About 1.1 Ga North America was part of the supercontinent Rodinia. The Southwest possibly ...
The Great Basin Altiplano during the middle
... (1997) model states that the crust thinning was from 70 to 50 km by extensional unroofing between the Cretaceous and Eocene–Oligocene, whereas Constenius (1996) concluded that extensional basins formed from the middle Eocene to early Miocene. However, on the basis of his study of interbedded ash-flo ...
... (1997) model states that the crust thinning was from 70 to 50 km by extensional unroofing between the Cretaceous and Eocene–Oligocene, whereas Constenius (1996) concluded that extensional basins formed from the middle Eocene to early Miocene. However, on the basis of his study of interbedded ash-flo ...
UNIT 6 Time Geologic
... Scientists are able to learn about the past by studying the present. One way to do this is by studying the order in which geologic events occurred using a process called relative-age dating. This does not allow scientists to determine exactly how many years ago an event occurred, but it gives scient ...
... Scientists are able to learn about the past by studying the present. One way to do this is by studying the order in which geologic events occurred using a process called relative-age dating. This does not allow scientists to determine exactly how many years ago an event occurred, but it gives scient ...
Late Palaeozoic lam pro phyres and as so ci ated mafic subvolcanic
... post-collisional extension in the Carboniferous. The lamprophyres (minettes, vogesites, spessartites, kersantites) and associated mafic rocks (monzonites, micromonzodiorites) were emplaced as dyke swarms and as scattered veins that cut the crystalline basement and, locally, the overlying molasse dep ...
... post-collisional extension in the Carboniferous. The lamprophyres (minettes, vogesites, spessartites, kersantites) and associated mafic rocks (monzonites, micromonzodiorites) were emplaced as dyke swarms and as scattered veins that cut the crystalline basement and, locally, the overlying molasse dep ...
Harris, 2007
... orogen implies that extrusion of a wedge will lead to crustal thinning, unless there is some means of accreting new material into the wedge. Some form of channel flow would obviate the need for such thinning, as such models require that the crust thickens continuously until it weakens at depth, wher ...
... orogen implies that extrusion of a wedge will lead to crustal thinning, unless there is some means of accreting new material into the wedge. Some form of channel flow would obviate the need for such thinning, as such models require that the crust thickens continuously until it weakens at depth, wher ...
- BIROn - Birkbeck Institutional Research Online
... intrusion of small-degree partial melts (e.g. melilitites and nephelinites) in the Massif Central, Vosges, Black Forest, Rhenish Massif and Bohemian Massif. During the early Eocene (~ 52 Ma) the convergence rate between Africa and Europe gradually increased, followed by a decrease in the early Mioce ...
... intrusion of small-degree partial melts (e.g. melilitites and nephelinites) in the Massif Central, Vosges, Black Forest, Rhenish Massif and Bohemian Massif. During the early Eocene (~ 52 Ma) the convergence rate between Africa and Europe gradually increased, followed by a decrease in the early Mioce ...
Reconciling the geological history of western Turkey with plate
... We place the geological history since Cretaceous times in western Turkey in a context of convergence, subduction, collision and slab break-off. To this end, we compare the west Anatolian geological history with amounts of Africa– Europe convergence calculated from the Atlantic plate circuit, and the ...
... We place the geological history since Cretaceous times in western Turkey in a context of convergence, subduction, collision and slab break-off. To this end, we compare the west Anatolian geological history with amounts of Africa– Europe convergence calculated from the Atlantic plate circuit, and the ...
Mid-crustal_magmatic.. - Department of Earth Sciences
... to Jurassic based on correlations with unmetamorphosed strata. Both units, but particularly the Holden unit, have been intruded by numerous plutons now preserved as orthogneisses. In the southwest part of the Chelan block, the Napeequa unit overlies the Swakane terrane along a probable thrust contac ...
... to Jurassic based on correlations with unmetamorphosed strata. Both units, but particularly the Holden unit, have been intruded by numerous plutons now preserved as orthogneisses. In the southwest part of the Chelan block, the Napeequa unit overlies the Swakane terrane along a probable thrust contac ...
PDF
... 2006). These events include the late Mesoproterozoic Grenville orogen, early Cambrian– middle Paleozoic continental rifting and passive margin formation, late Paleozoic Ouachita orogeny during the final stages of assembly of Pangea, and formation of the modern continental margin accompanied by brief ...
... 2006). These events include the late Mesoproterozoic Grenville orogen, early Cambrian– middle Paleozoic continental rifting and passive margin formation, late Paleozoic Ouachita orogeny during the final stages of assembly of Pangea, and formation of the modern continental margin accompanied by brief ...
Guide to Epithermal Gold and Silver in NL
... They have different gangue and ore mineralogy, formed by the interaction of different hydrothermal fluids with host rocks and ground waters (Figures 4). HS and LS systems share some ore, gangue and alteration minerals, but the two systems can be separated based on the presence of several key ore ...
... They have different gangue and ore mineralogy, formed by the interaction of different hydrothermal fluids with host rocks and ground waters (Figures 4). HS and LS systems share some ore, gangue and alteration minerals, but the two systems can be separated based on the presence of several key ore ...
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.