Neoarchean high-potassium granites of the Boothia mainland area, Rae domain, Churchill Province: U–Pb zircon and Sm–Nd whole rock isotopic constraintsThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh.

2011 ◽  
Vol 48 (2) ◽  
pp. 247-279 ◽  
Author(s):  
Alana M. Hinchey ◽  
William J. Davis ◽  
James J. Ryan ◽  
Léopold Nadeau
Keyword(s):  
Sedimentary Cover ◽  
Amphibolite Facies ◽  
Sedimentary Sequence ◽  
Special Issue ◽  
Isotopic Data ◽  
High Potassium ◽  
North Central ◽  
The North ◽  
Facies Metamorphism

The Boothia mainland region of the north-central Rae domain is underlain by remnants of a Neoarchean volcano sedimentary sequence dismembered by two regionally extensive Neoarchean high-potassium granitoid suites with rare occurrences of a structurally interleaved, Paleoproterozoic sedimentary cover sequence. The granitoids and their gneissic equivalents are dominated by variably deformed and metamorphosed I-type, metaluminous, polyphase, commonly porphyritic to augen, biotite ± hornblende monzogranite, and subordinate granodiorite, with rare tonalite. New geochronological results, the first for this area, demonstrate that the widespread Neoarchean granitoid plutonism is dominantly 2.61–2.59 Ga, with a less prominent 2.66 Ga plutonic event. The age of zircon recrystallization suggests that ca. 2.60 Ga Archean metamorphism and fabric development (S1) affected the 2.66 Ga plutons prior to or contemporaneously with intrusion of the voluminous ca. 2.6 Ga suite. εNd(t) for the ca. 2.61–2.59 Ga suite range from 1.4 to –1.9, overlapping with the ca. 2.66 Ga suite that range from 1.4 to 1.5. The Nd isotopic data, coupled with the presence of inherited ca. 2.65, 2.70, and 2.85–2.90 Ga zircon, suggests recycling of older, Neoarchean to Mesoarchean crust in the formation of these suites. Metaplutonic rocks preserve Paleoproterozoic deformation (F4 and F5) and amphibolite-facies metamorphism, sporadically recorded in zircon rims that formed at 1.81 Ga. This event strongly reoriented the Neoarchean fabrics in metaplutonic rocks, generally without the development of a new coaxial Paleoproterozoic fabric, and we attribute this strain and metamorphism to the Hudsonian orogeny.

scholarly journals Zircon U–Pb Dating and Lu-Hf Isotope of the Retrograded Eclogite from Chicheng, Northern Hebei Province, China

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xu Kong ◽  
Xueyuan Qi ◽  
Wentian Mi ◽  
Xiaoxin Dong
Keyword(s):  
Regional Metamorphism ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Metamorphic Event ◽  
Isotopic Data ◽  
Metamorphic Condition ◽  
Eu Anomaly ◽  
Facies Metamorphism ◽  
Eclogite Facies ◽  
Plagioclase Gneiss

We report zircon U–Pb ages and Lu-Hf isotopic data from two sample of the retrograded eclogite in the Chicheng area. Two groups of the metamorphic zircons from the Chicheng retrograded eclogite were identified: group one shows characteristics of depletion in LREE and flat in HREE curves and exhibit no significant Eu anomaly, and this may imply that they may form under eclogite facies metamorphic condition; group two is rich in HREE and shows slight negative Eu anomaly indicated that they may form under amphibolite facies metamorphic condition. Zircon Lu-Hf isotopic of εHf from the Chicheng eclogite has larger span range from 6.0 to 18.0, which suggests that the magma of the eclogite protolith may be mixed with partial crustal components. The peak eclogite facies metamorphism of Chicheng eclogite may occur at 348.5–344.2 Ma and its retrograde metamorphism of amphibolite fancies may occur at ca. 325.0 Ma. The Hongqiyingzi Complex may experience multistage metamorphic events mainly including Late Archean (2494–2448 Ma), Late Paleoproterozoic (1900–1734 Ma, peak age = 1824.6 Ma), and Phanerozoic (495–234 Ma, peak age = 323.7 Ma). Thus, the metamorphic event (348.5–325 Ma) of the Chicheng eclogite is in accordance with the Phanerozoic metamorphic event of the Hongqiyingzi Complex. The eclogite facies metamorphic age of the eclogite is in accordance with the metamorphism (granulite facies or amphibolite facies) of its surrounding rocks, which implied that the tectonic subduction and exhumation of the retrograded eclogite may cause the regional metamorphism of garnet biotite plagioclase gneiss.

Geochronology of the transition of eclogite to amphibolite facies metamorphism in the North Qinling orogen of central China

Lithos ◽  
2011 ◽  
Vol 125 (3-4) ◽  
pp. 969-983 ◽  
Author(s):  
Hao Cheng ◽  
Chao Zhang ◽  
Jeffrey D. Vervoort ◽  
Xianhua Li ◽  
Qiuli Li ◽  
...  
Keyword(s):  
Amphibolite Facies ◽  
Central China ◽  
Qinling Orogen ◽  
The North ◽  
Facies Metamorphism ◽  
North Qinling

scholarly journals Structural studies in the pre-Cambrian of western Greenland. Part III. Southern Sukkertoppen District

1962 ◽  
Vol 31 ◽  
pp. 1-46
Author(s):  
A Berthelsen
Keyword(s):  
Structural Evolution ◽  
Granulite Facies ◽  
Field Work ◽  
Amphibolite Facies ◽  
Alternative Theory ◽  
Low Grade ◽  
The North ◽  
Kinematic Evolution ◽  
Facies Metamorphism ◽  
Wrench Fault

This paper summarises several summers field work within the southern Sukkertoppen district. Since detailed mapping has only been carried out within smaller areas within the region, the remainder being covered by reconnaissance mapping along the coasts, the results should be considered as preliminary. The southern Sukkertoppen district can be divided into three tectonic units, the Nordland, the Finnefjeld, and the Alángua complexes, which, most probably, were formed during the Ketilidian cycle (E. Wegmann, 1938). The metamorphic complexes are traversed by postorogenic dykes and faults (Berthelsen and Bridgwater, 1960). The dykes and faults were seemingly formed before the Nagssugtôqidian revolution which affected the country further to the north (Ramberg, 1948). The northern Nordland complex is shown to have passed through a metamorphic and structural evolution very similar to that which recently has been described from a small area within the complex (see table 2). An original granulite facies rock assemblage has been exposed to two successive imprints of retrograde metamorphism: first an amphibolite facies metamorphism; next a postorogenic epidote-amphibolite to greenschist facies metamorphism in connection with the formation of the younger faults. Evidence is brought forward that the tectonic phases established from Tovqussap nunâ may also be traced within the remaining parts of the Nordland complex. In one case (see fig. 3) an analysis of the basement structures reveals that the post-orogenic faulting is of the wrench fault type. The Finnefjeld complex which is built up of homogeneous hornblende-biotite-bearing quartz-dioritic gneisses is believed to have been originally composed of granulite facies rocks. Subsequent strong penetrative movements accompanied by low grade amphibolite facies metamorphism were responsible for the formation of the present Finnefjeld gneisses. This idea is strongly supported by the facts that relic patches of hypersthene gneiss and transgressive, but deformed, more or less uralitised diorite bodies occur within the Finnefjeld gneiss. The Alangua complex comprises abundant pelitic and semipelitic schists, amphibolites, ultrabasics and skarn rocks in addition to gneisses which are considered to be of metasomatic origin. The ultrabasic rocks have been described by H. Sørensen (1952,1953, 1954, and 1955). The rocks of this complex can also be shown to have passed through two periods of metamorphism (see also H. Sørensen, 1952); an original medium to high grade amphibolite facies metamorphism was succeeded by a later low grade amphibolite facies metamorphism accompanied by granitisation, pegmatisation etc., indicating the presence of a volatile-rich dispersed phase. Although not studied in detail, the structures of the Alángua complex are sufficiently well-known to establish the kinematic evolution of this complex. The first amphibolite facies metamorphism seems to correspond to the Smalledal-Pâkitsoq phases of the Nordland complex, while the subsequent period of low grade amphibolite metamorphism can be matched with the posthumous phase. During this latter, the northern part of the Nordland complex, which locally was thrust over the Alángua rocks (thereby causing their refolding) was converted into the present Finnefjeld gneisses. This interpretation explains the present differences between the three com· plexes as being due to Stockwerk tectonics, fig. 16. An alternative theory which holds that the Alángua rocks are younger than those of the southern complexes does not seem to concur with the field relation known so far. No mineral deposits of economic interest were found during the survey, but traces of sulfides (see tables 1 and 3), magnetite, molybdenite, corundum, monazite, zircon, talc and soapstone have been met with at various localities.

scholarly journals Caledonian and pre-Caledonian geology of the region between Grandjean Fjord and Bessel Fjord (75°–76°N), North-East Greenland

1989 ◽  
Vol 145 ◽  
pp. 90-97
Author(s):  
N Henriksen ◽  
J.D Friderichsen ◽  
R.A Strachan ◽  
N.J Soper ◽  
A.K Higgins
Keyword(s):  
Amphibolite Facies ◽  
Sedimentary Sequence ◽  
East Greenland ◽  
Early Proterozoic ◽  
Late Proterozoic ◽  
North East ◽  
The North ◽  
Group A ◽  
Metasedimentary Sequence

The area between Grandjean Fjord and Bessel Fjord was the focus in 1988 of regional geological investigations and 1:500000 mapping during the North-East Greenland project (Henriksen, 1989). The greater part of the area forms part of the East Greenland Caledonides and can be divided into three distinct rock groups: infracrustal gneisses and granites of possibie Archaean or early Proterozoic origin; a metasedimentary sequence which has probably suffered both mid-Proterozoic and Caledonian migmatisation and metamorphism; and the late Proterozoic Eleonore Bay Group, a thick sedimentary sequence which has undergone amphibolite facies Caledonian metamorphism in its lower parts and is intruded by Caledonian granites. Aspects of the stratigraphy and sedimentology of the Eleonore Bay Group are described by Sønderholm et al. (1989); only the structures affecting the sequence are described here.

scholarly journals Tectonic inversion of the Dnieper-Donets basin. Part 1. Collizion tectonics of the Western-Donets graben

2020 ◽  
Keyword(s):  
Transition Zone ◽  
Sedimentary Cover ◽  
Donets Basin ◽  
Tectonic Deformation ◽  
Sedimentary Sequence ◽  
Heterogeneous Distribution ◽  
Three Generations ◽  
The North ◽  
Thrust Front ◽  
Folded Structure

Formulation of the problem. New results of tectonophysical studies of the structural-kinematic evolution of the Earth's crust of Dnieper-Donets paleorift at the collision stage are presented in the paper. The subject of research is a complex of deformation structures that complicate the sedimentary cover in the transitional zone with Donets folded structure. Review of previous publications and studies. According to new mapping data, tectonic deformations of the sedimentary cover were controlled by systems of faults of the north, northwest, and southeast vergence. The lattices of the Hercynian, Lamaric, and Attic tectonites determine the specific “cross-thrust” structure of pushing. Due to the heterogeneous distribution of deformations of different ages, the stratigraphic volume of the sedimentary sequence varies in area from the Pliocene-Anthropogenic to the Mesozoic-Cenozoic. Overthrusts and linear folding of three generations permeate the sedimentary sequence of the transition zone from east to west for hundreds of kilometers within the eastern part of Izyumsky paleorift segment. Methods. Using the original method of tectonic deformation fields’ reconstruction and tectonophysics analysis of structures, collision deformations of the platform sedimentary cover of the southeastern part of Dnieper-Donets depression are studied. The materials of geological mapping of the transition zone and instrumental definitions of the vergence of the Hercynian, Laramian, and Attic faults constituted the analytical base of tectonophysical studies. Results. In the transition zone, West-Donets segment of the tectonic wedging, which completely destroys the riftogenic structure in the southeast of the basin was identified. It was formed as a result of a thrust on the syneclise autochthon repeatedly deformed, crumpled into the folds of geomass from the western slopes of Donets folded structure. It consists of structural ensembles of linear thrust folds, tectonic covers of transverse, pushing of sedimentary geomas from axial to onboard zones, and folded covers of longitudinal thrust. The thrust covers and folds of allochthon end in the depression with scaly compression fans formed at the ends of the main thrusts. In the thrust front of West Donets segment, a geodynamic discharge strip was diagnosed, where structural zones of displacement of geomass were formed. On the north-eastern flank of the thrust front they are represented by large linear anticlinal zones of the so-called “open Paleozoic structures”, such as Torsko-Drobishevsk, North-Donets, Matrossko-Toshkovsk zones, and on the southwestern - Petrovsky-Novotroitsk zone of reverse-folds. The structural peak of the West-Donets segment is the tectonic node of thrusts and strike-slips of three generations, localized in the joint area of the central and southern structural branches of the axial salt-dome folding. Scientific novelty and practical significance. The current regional tectonic scheme has been revised on the conceptual foundations of dynamic geotectonics. It is shown that the riftogenic structure of the transition zone at the collision stage of evolution was completely destroyed by deformations of three generations. Lattice of tectonites, thrust cover and uplift folding zones of the Hercynian, Laramian, and Attic generations together form West-Donets cover-fold region within it. The main tectonic element of the region is the segment of the tectonic wedging of the same name. By the nature of the structure in its northern part, Lugansk-Kamyshevakhsky district is distinguished by a link echelon of linear folding, and in the south by Kalmius-Toretsky region of tectonic thrust cover. West Donets segment is an important component of the structural-tectonic frame of the sedimentary cover, which determines the modern transverse tectonic segmentation of the paleorift.

scholarly journals Contrasted types of metamorphism of basic intrusions in the Precambrian basement of the Tasîussaq area, South Greenland

1968 ◽  
Vol 71 ◽  
pp. 1-47
Author(s):  
P.R Dawes
Keyword(s):  
Granulite Facies ◽  
Amphibolite Facies ◽  
Precambrian Basement ◽  
Thermal Front ◽  
Granulite Facies Metamorphism ◽  
North West ◽  
Metamorphic History ◽  
Long Span ◽  
The North ◽  
Facies Metamorphism

Metamorphosed rocks of three distinct episodes of basic intrusion can be recognised in the Precambrian basement of the Tasiussaq area, South Greenland. The oldest intrusions, represented by sills and dykes, are pyriclasites and biotitepyriclasites; the second episode intrusions, in the form of dykes, are pyroxenemetadolerites and the third episode intrusions, represented by dykes and small bodies, are metagabbros, metadolerites, metanorites and amphibolites. The metamorphic nature of the rocks of the three episodes is a reflection of age. Chemical and modal analyses of rocks from the three episodes are presented. Fresh diorite sills and dolerite dykes represent later episodes of Precambrian basic intrusion. The basic rocks depict the varying types of metamorphic conditions which affected the area in Precambrian time, and these are seen to differ from the established metamorphic history in areas to the north-west in South Greenland. The pyriclasites and biotite-pyriclasites have been derived through granulite facies metamorphism; the pyroxene-metadolerites by dipsenic metamorphism under conditions corresponding to the amphibolite facies and the metagabbros, metadolerites, metanorites and amphibolites through amphibolitisation during amphibolite facies metamorphism. It is suggested that the metamorphism producing the pyroxene-metadolerites (Sanerutian in age) was controlled by dipsenic conditions inherited from earlier granulite facies metamorphism (Ketilidian in age). This implies that the Ketilidian and Sanerutian metamorphisms in the Tasiussaq area are not separated by a long span of time and that the break in plutonism marked by the pyroxene-metadolerites cannot be regarded as a significant cratogenic hiatus between two separate plutonisms. The importance of water in controlling trends in the metamorphism of dolerites is stressed. The 1st episode intrusions have undergone severe changes since intrusion and no palimpsest features indicative of primary texture or mineralogy remain. The majority of the 2nd episode intrusions display a granular texture, but some display sub-ophitic and relic sub-ophitic textures. The 3rd episode intrusions display a range from ophitic, sub-ophitic and microporphyritic textures to relic stages of these textures. The 1st episode intrusions were emplaced into a geosynclinal pile of sediments and were probably connected with the volcanicity which occurred at the end of sedimentation. The 2nd and 3rd episode intrusions were emplaced into granitic and metamorphic rocks at a later stage in the same 'geological cycle'. Both the 2nd and 3rd episode intrusions are considered to indicate trends in the crust towards brittle conditions marking temporary partial withdrawals of the thermal front. Their preserved ophitic and sub-ophitic textures are not indicative of emplacement and crystallisation in cratogenic conditions.

scholarly journals PETROGRAPHY AND GEOCHEMISTRY OF METASEDIMENTARY ROCKS FROM THE TAKU SCHIST IN KELANTAN, NORTH-EAST PENINSULAR MALAYSIA.

2021 ◽  
Vol 5 (2) ◽  
pp. 124
Author(s):  
Muhammad Irman Khalif Bin Ahmad Aminuddin ◽  
Nugroho Imam Setiawan ◽  
I Wayan Warmada ◽  
Kamar Shah Ariffin ◽  
Kotaro Yonezu
Keyword(s):  
Sedimentary Cover ◽  
Tectonic Setting ◽  
Evolutionary Process ◽  
Peninsular Malaysia ◽  
Amphibolite Facies ◽  
Accretionary Wedge ◽  
Metasedimentary Rocks ◽  
North East ◽  
The North ◽  
Sedimentary Provenance

The Taku Schist, which is located in the north-east Peninsular Malaysia, is characterized by its North-South oriented elongated body. It forms part of the Indonesian orogenic build-up that was generated via the convergence of the Sibumasu continental unit and Sukhothai Arc. Subsequent petrography analyses of the metasedimentary rocks sourced from the Taku Schist revealed that their formation was attributable to the metamorphism of greenschist into amphibolite facies, which could be observed near the Triassic and Cretaceous intrusions of the Kemahang Granite. The evolutionary process of the rocks could be linked with the interactions occurring between contact and regional metamorphisms. The resulting chemical classification upon their assessment disclosed that the metasedimentary rocks of Taku Schist were made up of greywacke and shale, grouped into the quartzose sedimentary provenance, and belonged to the Continental Island Arc (CIA). This information is required for the tectonic setting discrimination purpose. It is a reflection of the episodic contractions underwent by the Taku Schist, wherein they would lead to the Sibumasu sedimentary cover along with both an accretionary wedge and the genetically-correlated Bentong-Raub melange to different greenschist. Otherwise associated with amphibolite facies, the conditions and depths of the facies were determined according to their position in relation to the upper plate of the Sukhothai Arc.

Trondhjemitic basement enclave near the Archean Favourable Lake volcanic complex, northwestern Ontario, Canada

1980 ◽  
Vol 17 (5) ◽  
pp. 652-667 ◽  
Author(s):  
E. M. Hillary ◽  
L. D. Ayres
Keyword(s):  
Partial Melting ◽  
Amphibolite Facies ◽  
Volcanic Complex ◽  
Volcanic Event ◽  
Major Phase ◽  
Trout Lake ◽  
The North ◽  
Northwestern Ontario ◽  
Quartz Monzonite ◽  
Facies Metamorphism

A 15 km2 foliated to gneissic trondhjemite enclave (2.91 Ga) in the Archean North Trout Lake batholith is a metamorphosed remnant of prevolcanism sialic basement. The basement is separated from the nearby Archean Favourable Lake volcanic complex by younger plutons, but was a source of detritus for some of the sedimentary formations in the volcanic complex. The trondhjemite is only a small remnant of an originally more extensive basement.Primary plutonic features can be readily recognized in the trondhjemite in spite of amphibolite facies metamorphism. The basement underwent at least two deformational events: (1) syn-emplacement deformation that produced foliation and gneissosity, and brecciated and deformed early dikes and xenoliths and (2) later recrystallization. The recrystallization was caused by strain and heat produced by emplacement of the North Trout Lake batholith. Emplacement of successive batholith phases progressively heated the basement and elevated it from its originally deeper level. Metamorphism culminated with emplacement of the youngest major phase of the batholith. The intensity of recrystallization and the habit and abundance of late leucocratic quartz monzonite sills and dikes are zoned with respect to this youngest phase.The high Al2O3 trondhjemitic magma probably formed by partial melting of amphibolite at relatively shallow depths. The parent amphibolite probably represents a still earlier volcanic event.

Geochemical and radiogenic isotope (Sr-Nd) characteristics of Paleoproterozoic anorthositic and granitoid rocks in the Umiakoviarusek Lake region, Labrador, Canada.

1999 ◽  
Vol 36 (12) ◽  
pp. 1957-1972 ◽  
Author(s):  
Stephen J Piercey ◽  
Derek HC Wilton
Keyword(s):  
Crustal Contamination ◽  
Isotopic Data ◽  
North Central ◽  
Radiogenic Isotope ◽  
The North ◽  
Lake Region ◽  
Intrusive Rocks ◽  
Mantle Component ◽  
Granitoid Rocks ◽  
Source Materials

Recent work in the north-central Labrador has identified Paleoproterozoic anorthositic and granitoid rocks that are spatially associated with, yet temporally distinct from, younger Mesoproterozoic intrusions of the Nain Plutonic Suite. The Umiakoviarusek Lake (UL) region of Labrador contains several of these Paleoproterozoic intrusions and provides an opportunity to study their geochemical and radiogenic isotope (Sr-Nd) characteristics. Geochemically, the anorthositic and granitoid rocks have features consistent with contemporary anorthositic and granitoid rocks from other anorthosite-mangerite-charnockite-granite complexes. The anorthositic rocks contain elevated contents of Al2O3, CaO, Sr, and Eu with low Ba, Rb, K, Zr, total rare earth elements (REE), and light REE. The granitoid rocks, on the other hand, contain lower concentrations of these elements along with elevated SiO2 and K2O. Isotopic data at 2050 Ma for the anorthositic rocks (ISr = 0.7048-0.7082; εNd = -4.1 to -15.9) and granitoid rocks (ISr = 0.7036-0.7094, εNd = -5.1 to -9.7) are consistent with variable crustal and mantle contributions to their genesis. The relatively unradiogenic Sr and slightly evolved Nd isotopic data from the UL granitoid rocks is consistent with a significant juvenile mantle component, possibly derived from an underplating mantle plume; this component may also be present in the anorthositic rocks. The Nd and Sr isotopic data are also consistent with crustal contamination from Archean source materials; however, based on the existing isotopic database for the Nain Province gneisses, it is not possible to delineate a specific gneiss component. Furthermore, it is also quite possible that an Archean source, unlike any described at present, was a crustal source component in the UL intrusive rocks.

A bedded deposit of anthophyllite schist in the Precambrian belt of Nellore, South India

1974 ◽  
Vol 111 (3) ◽  
pp. 221-228 ◽  
Author(s):  
T. Ramamohana Rao
Keyword(s):  
South India ◽  
Regional Metamorphism ◽  
Amphibolite Facies ◽  
Schist Belt ◽  
North Central ◽  
The North ◽  
Nellore Schist Belt ◽  
Silicate Rocks

SummaryA pure anthophyllite schist occurs as a bedded deposit conformable with garnet-bearing quartz—muscovite, and quartz—chlorite—biotite schists and diopside-bearing caic-silicate rocks in the north-central part of the Nellore Schist Belt. Field and petrochemical studies show that anthophyllite schist has formed from regional metamorphism of Fe-, Mg-rich aluminous sediments aided by metamorphic differentiation due to local kinematic action under amphibolite facies conditions which is the general grade of metamorphism of the Nellore Schist Belt. A pure anthophyllite schist of sedimentary origin reported here is the first of its kind described from any terrain.

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