Meddelelser fra Dansk Geologisk Forening, vol. 17/4, pp. 504-516
... even smaller than present day ones. The difficulty is how the depths necessary for such high pressure metamorphism were achieved. In this respect it has to be stated that in the present author's opinion tectonic overpressures cannot have been the main cause, because the Hercynian metamorphics are al ...
... even smaller than present day ones. The difficulty is how the depths necessary for such high pressure metamorphism were achieved. In this respect it has to be stated that in the present author's opinion tectonic overpressures cannot have been the main cause, because the Hercynian metamorphics are al ...
Age and tectonic setting of the Tysfjord gneiss granite, Efjord, North
... obvious due to the lower biotite content and smaller grain size in the former. The basement-cover contact strikes E-W and dips steeply toward N north of Efjord, but changes to an almost N-S strike and easterly dip between Efjord and Ofotfjorden (Figs. 3 and 4). Early (synmetamorphic) mineral lineati ...
... obvious due to the lower biotite content and smaller grain size in the former. The basement-cover contact strikes E-W and dips steeply toward N north of Efjord, but changes to an almost N-S strike and easterly dip between Efjord and Ofotfjorden (Figs. 3 and 4). Early (synmetamorphic) mineral lineati ...
metamorphism
... Textural Response to Metamorphism Reflects the intensity and directionality of pressure (or stress). • Increased grain size - During prograde metamorphism or at a particular grade that is maintained for a long period of time, minerals will tend to increase in size. • Foliation - As new platy minera ...
... Textural Response to Metamorphism Reflects the intensity and directionality of pressure (or stress). • Increased grain size - During prograde metamorphism or at a particular grade that is maintained for a long period of time, minerals will tend to increase in size. • Foliation - As new platy minera ...
DNR kettle dome fox
... but in places the sill-like bodies can be followed into and through fold hinges. At approximately 2,630 ft elevation, the granitic dikes weather into cavernous zones under steep cliffs developed in massive white quartzite above. (Work to the west and north on benches below the upper cliff.) The gran ...
... but in places the sill-like bodies can be followed into and through fold hinges. At approximately 2,630 ft elevation, the granitic dikes weather into cavernous zones under steep cliffs developed in massive white quartzite above. (Work to the west and north on benches below the upper cliff.) The gran ...
Mafic to Intermediate Plutons
... •Subophitic texture containing hornblende, plagioclase feldspar, and small amounts of biotite •Very weak metamorphic fabric present •Cross cuts the Garnet Hill migmatite, folded metasediments, and quartz monzonite •Felsic veins are locally injected into diorite with small amounts of migmatization lo ...
... •Subophitic texture containing hornblende, plagioclase feldspar, and small amounts of biotite •Very weak metamorphic fabric present •Cross cuts the Garnet Hill migmatite, folded metasediments, and quartz monzonite •Felsic veins are locally injected into diorite with small amounts of migmatization lo ...
ALKALINE PORPHYRY COPPER DEPOSITS AND - Rigeo
... The geotectonic setting (cratonic or back-arc) of IOCG deposits, and the nature of their associated magmas is not consensual. Alkaline porphyry deposits and IOCG’s show the same high temperature Na-Ca alteration and both occur in extensional tectonic settings. These two similarities contribute to th ...
... The geotectonic setting (cratonic or back-arc) of IOCG deposits, and the nature of their associated magmas is not consensual. Alkaline porphyry deposits and IOCG’s show the same high temperature Na-Ca alteration and both occur in extensional tectonic settings. These two similarities contribute to th ...
BASIN TYPES ACCORDING TO TECTONIC by Prof. Dr. Abbas
... • Epicratonic basins are those which lie on the edge of continental crust. Though subcircular in plan, by definition, they tend to be embayed and open towards the adjacent ocean basin. The axis of an epicratonic basin may plunge to the floor of the ocean or be interrupted by a sill-like feature at t ...
... • Epicratonic basins are those which lie on the edge of continental crust. Though subcircular in plan, by definition, they tend to be embayed and open towards the adjacent ocean basin. The axis of an epicratonic basin may plunge to the floor of the ocean or be interrupted by a sill-like feature at t ...
Petrology and Geochemistry of Basement Complex Rocks in Okom
... Phyllite is a regionally metamorphosed foliated pellitic rock. They are fine grained micaceous rocks occasionally showing segregation layering. Just like schist, phyllites are restricted to the western part of Oban Massif. Garnetiferous varieties have been reported from the Uwet area [14]. They are ...
... Phyllite is a regionally metamorphosed foliated pellitic rock. They are fine grained micaceous rocks occasionally showing segregation layering. Just like schist, phyllites are restricted to the western part of Oban Massif. Garnetiferous varieties have been reported from the Uwet area [14]. They are ...
Re^Os evidence for replacement of ancient mantle
... (3800^3000 Ma) granitic gneisses and supracrustal rocks, including ultrama¢c to felsic volcanic rocks and metasediments [17,18]. The Western Block is characterized by late Archean to Paleoproterozoic metasedimentary belts that unconformably overlie Archean basement [17,21,22], which consists of gran ...
... (3800^3000 Ma) granitic gneisses and supracrustal rocks, including ultrama¢c to felsic volcanic rocks and metasediments [17,18]. The Western Block is characterized by late Archean to Paleoproterozoic metasedimentary belts that unconformably overlie Archean basement [17,21,22], which consists of gran ...
Geology of Greenland Survey Bulletin 177, 89-95
... The early tonalitic orthogneiss precursors were intruded into the supracrustal rocks as sheets, which were subsequently multiply folded together with their supracrustal host rocks in a tectonic regime dominated by lateral forces. Subsequent tonalite-trondhjemite and tonalite-granodiorite intrusions ...
... The early tonalitic orthogneiss precursors were intruded into the supracrustal rocks as sheets, which were subsequently multiply folded together with their supracrustal host rocks in a tectonic regime dominated by lateral forces. Subsequent tonalite-trondhjemite and tonalite-granodiorite intrusions ...
Three Dimensional Electrical Structure of the Crust and Upper
... Three Dimensional Electrical Structure of the Crust and Upper Mantle in Ordos Block and Adjacent Area: Evidence of Regional Lithospheric ...
... Three Dimensional Electrical Structure of the Crust and Upper Mantle in Ordos Block and Adjacent Area: Evidence of Regional Lithospheric ...
Slavonian excursion
... according to Pamić, 1986; Pamić et al., 1988a; Pamić and Lanphere, 1991) surrounded by (b) migmatites and migmatitic gneisses that grade into (c) medium-grade (amphibolite facies) metamorphic sequences composed of garnetiferous amphibolites, paragneisses and micaschists. The Radlovac metamorphic com ...
... according to Pamić, 1986; Pamić et al., 1988a; Pamić and Lanphere, 1991) surrounded by (b) migmatites and migmatitic gneisses that grade into (c) medium-grade (amphibolite facies) metamorphic sequences composed of garnetiferous amphibolites, paragneisses and micaschists. The Radlovac metamorphic com ...
GEOL100 4-5-10 Historical Geology of North America
... Silurian - Devonian - Acadian Orogeny in the East, Antlers Orogeny in the West By the middle Paleozoic, the east coast was an active margin, fringed by a new active subduction zone. During the Silurian , a small continent called Avalonia rode the oceanic lithosphere into this subduction zone and in ...
... Silurian - Devonian - Acadian Orogeny in the East, Antlers Orogeny in the West By the middle Paleozoic, the east coast was an active margin, fringed by a new active subduction zone. During the Silurian , a small continent called Avalonia rode the oceanic lithosphere into this subduction zone and in ...
TECTONIC AND GEOLOGIC EVOLUTION OF THAILAND
... middle, separating the other two, is a north-south trending fold belt of middle Paleozoic to lower Mesozoic marine sediments. The other two are fragments of ancient continent with crystalline Precambrian basement rocks. The three may be designated Western Province, Central Province and Eastern Provi ...
... middle, separating the other two, is a north-south trending fold belt of middle Paleozoic to lower Mesozoic marine sediments. The other two are fragments of ancient continent with crystalline Precambrian basement rocks. The three may be designated Western Province, Central Province and Eastern Provi ...
Metamorphism and Metamorphic Reactions?
... only theorize as to the origin of ignimbrites and the other massive flows resulting from explosive volcanism. These massive deposits could be seen in the field, but the rate and nature of deposition was very poorly understood. Films and pictures (some even taken from the space shuttle) of the progre ...
... only theorize as to the origin of ignimbrites and the other massive flows resulting from explosive volcanism. These massive deposits could be seen in the field, but the rate and nature of deposition was very poorly understood. Films and pictures (some even taken from the space shuttle) of the progre ...
Plate tectonics and lithosphere architecture: temporal and spatial
... 'stratigraphy' of the lithosphere beneath individual volcanic provinces. Lithostratigraphic variations can be (a) investigated across boundaries between major crustal age provinces, (b) studied in relation to heat flow variations, and, (c) correlated with the presence or absence of high velocity ano ...
... 'stratigraphy' of the lithosphere beneath individual volcanic provinces. Lithostratigraphic variations can be (a) investigated across boundaries between major crustal age provinces, (b) studied in relation to heat flow variations, and, (c) correlated with the presence or absence of high velocity ano ...
full text - NWT Protected Area Strategy
... ultramafic rocks commonly occur as xenoliths within the granitoid gneisses (e.g., King, 1986; Bowring et al., 1989b; Stern and Bleeker, 1998; Iizuka et al., 2007). These rocks are cut by several generations of younger granitoid veins and dykes that range from foliated to massive. Post-Archean lithol ...
... ultramafic rocks commonly occur as xenoliths within the granitoid gneisses (e.g., King, 1986; Bowring et al., 1989b; Stern and Bleeker, 1998; Iizuka et al., 2007). These rocks are cut by several generations of younger granitoid veins and dykes that range from foliated to massive. Post-Archean lithol ...
Popov_a
... thick volcano-sedimentary complex and associated intrusions were formed. The magmatic rocks belong to 4 series: tholeiitic, Ca-alkaline, subalkaline and K-alkaline. This zone marks a new tectonic plan in the investigated territory. This is a transittype structure, because it penetrated deeply into t ...
... thick volcano-sedimentary complex and associated intrusions were formed. The magmatic rocks belong to 4 series: tholeiitic, Ca-alkaline, subalkaline and K-alkaline. This zone marks a new tectonic plan in the investigated territory. This is a transittype structure, because it penetrated deeply into t ...
Experimental_laboratory_files/2004_The source of Granites
... involved has to produce low Sm/Nd and low Rb/Sr. An alternative way is to assume that I-type granites typically with low 87Sr86/Sr initial ratios are generated from a crustal source that has this particular composition. Comparison with Archaean crust array (Fig. 1a) suggests that tonalites of the lo ...
... involved has to produce low Sm/Nd and low Rb/Sr. An alternative way is to assume that I-type granites typically with low 87Sr86/Sr initial ratios are generated from a crustal source that has this particular composition. Comparison with Archaean crust array (Fig. 1a) suggests that tonalites of the lo ...
chapter9_Proterozoic..
... atmosphere and biosphere, as well as the origin of some important natural resources. Oxygen dependant organisms and the types of cells that make up most of today's organisms evolved during this time. Fig. 19.1, p. 494 ...
... atmosphere and biosphere, as well as the origin of some important natural resources. Oxygen dependant organisms and the types of cells that make up most of today's organisms evolved during this time. Fig. 19.1, p. 494 ...
Characterization of crustal-scale structures interpreted from
... City was used as a test area to determine if a radiometric survey may provide indirect evidence for hydrothermal fluid flow along faults and shear zones in gneiss terranes of the Grenville Province and for training of MSc students Camille Armengaud and Jean-Phillipe Drolet) in the use of instruments ...
... City was used as a test area to determine if a radiometric survey may provide indirect evidence for hydrothermal fluid flow along faults and shear zones in gneiss terranes of the Grenville Province and for training of MSc students Camille Armengaud and Jean-Phillipe Drolet) in the use of instruments ...
Local modification of the lithosphere beneath the central and
... body wave tomography studies have been conducted within the tectonic blocks of the NCC and adjacent regions (e.g., Tian et al., 2009; Zhao et al., 2009, 2012). Zhao et al. (2009) observed a plume-like low-velocity anomaly in the upper mantle beneath the TNCO from images of finite frequency body wave ...
... body wave tomography studies have been conducted within the tectonic blocks of the NCC and adjacent regions (e.g., Tian et al., 2009; Zhao et al., 2009, 2012). Zhao et al. (2009) observed a plume-like low-velocity anomaly in the upper mantle beneath the TNCO from images of finite frequency body wave ...
Foliated rocks
... Composed of light-colored feldspar layers with bands of dark mafic minerals ...
... Composed of light-colored feldspar layers with bands of dark mafic minerals ...
main geological features of the kuopio district
... whose age is about 1930–1900 Ma old (i.e. older Svecofennian). Further south, the western side of the Iisvesi fault zone consists predominantly of well preserved metagreywackes with thin conglomerate interbeds and partly of migmatic mica gneisses (Rusalansuo lithodeme). INFRACRUSTAL ROCKS Most of th ...
... whose age is about 1930–1900 Ma old (i.e. older Svecofennian). Further south, the western side of the Iisvesi fault zone consists predominantly of well preserved metagreywackes with thin conglomerate interbeds and partly of migmatic mica gneisses (Rusalansuo lithodeme). INFRACRUSTAL ROCKS Most of th ...
68a_Chemale Hartmann..
... this part of Brazil using regional geological data, and by correlating the Brasiliano/pan-African belts such as the Ribeira, Dom Feliciano, Damara and Gariep Belts in southern Brazil and southern Africa respectively (Porada, 1979, 1989; Basei, 1985; Brito Neves and ...
... this part of Brazil using regional geological data, and by correlating the Brasiliano/pan-African belts such as the Ribeira, Dom Feliciano, Damara and Gariep Belts in southern Brazil and southern Africa respectively (Porada, 1979, 1989; Basei, 1985; Brito Neves and ...
Yilgarn Craton
The Yilgarn Craton is a large craton that constitutes the bulk of the Western Australian land mass. It is bounded by a mixture of sedimentary basins and Proterozoic fold and thrust belts. Zircon grains in the Jack Hills, Narryer Terrane have been dated at ~4.27 Ga, with one detrital zircon dated as old as 4.4 Ga.