Ages of detrital and metamorphic zircons and monazites from a pre-Taltson magmatic zone basin at the western margin of Rae Province

1994 ◽  
Vol 31 (8) ◽  
pp. 1353-1364 ◽  
Author(s):  
H. H. Bostock ◽  
O. van Breemen
Keyword(s):  
Isotope Geochemistry ◽  
Granulite Facies ◽  
Metamorphic Grade ◽  
Detrital Zircons ◽  
Ultramafic Rocks ◽  
Crustal Accretion ◽  
The West ◽  
Slave Province ◽  
Basin Formation ◽  
High Grade Metamorphism

The western edge of Rae Province, prior to indentation of Slave Province, is conceived as a compressional tectonic margin in which Archean plutonic rocks were intruded by syntectonic granites of 2.4–2.3 Ga age as a result of eastward subduction. Subsequently this margin was intruded by the 2.0–1.90 Ga granites that characterize the Taltson magmatic zone. The latter granites engulf remnants of a widespread supracrustal assemblage of lower granulite facies metamorphic grade, the age of which has heretofore been unknown. We use U–Pb zircon and monazite geochronology to limit the age of cessation of deposition of these metasediments in a pre-Taltson granite basin to between 2.13 and 2.09 Ga.Similarities in geochronology and isotope geochemistry between western Rae Province and Buffalo Head domain, together with the presence of mafic to ultramafic rocks both within the basin and along the western Rae margin, suggest that basin formation was by rifting. Influx of 2.15 Ga detrital zircons probably from the west, and high-grade metamorphism accompanying basin closure at 2.09 Ga, suggest an eastward (inward) movement of magmatism at that time. A second similar eastward migration of magmatism occurred in association with the Slave–Churchill collision (2.0–1.9 Ga). These relations suggest a complex record of crustal accretion within Buffalo Head and Chinchaga domains, the details of which remain to be established.

scholarly journals The country rocks of Devonian magmatism in the North Patagonian Massif and Chaitenia

2018 ◽  
Vol 45 (3) ◽  
pp. 301 ◽  
Author(s):  
Francisco Hervé ◽  
Mauricio Calderón ◽  
Mark Fanning ◽  
Robert Pankhurst ◽  
Carlos W. Rapela ◽  
...  
Keyword(s):  
Metamorphic Grade ◽  
Oceanic Island ◽  
Detrital Zircons ◽  
Island Arc ◽  
Ultramafic Rocks ◽  
The West ◽  
Metasedimentary Rocks ◽  
The North ◽  
The Andes ◽  
Late Neoproterozoic

Previous work has shown that Devonian magmatism in the southern Andes occurred in two contemporaneous belts: one emplaced in the continental crust of the North Patagonian Massif and the other in an oceanic island arc terrane to the west, Chaitenia, which was later accreted to Patagonia. The country rocks of the plutonic rocks consist of metasedimentary complexes which crop out sporadically in the Andes on both sides of the Argentina-Chile border, and additionally of pillow metabasalts for Chaitenia. Detrital zircon SHRIMP U-Pb age determinations in 13 samples of these rocks indicate maximum possible depositional ages from ca. 370 to 900 Ma, and the case is argued for mostly Devonian sedimentation as for the fossiliferous Buill slates. Ordovician, Cambrian-late Neoproterozoic and “Grenville-age” provenance is seen throughout, except for the most westerly outcrops where Devonian detrital zircons predominate. Besides a difference in the Precambrian zircon grains, 76% versus 25% respectively, there is no systematic variation in provenance from the Patagonian foreland to Chaitenia, so that the island arc terrane must have been proximal to the continent: its deeper crust is not exposed but several outcrops of ultramafic rocks are known. Zircons with devonian metamorphic rims in rocks from the North Patagonian Massif have no counterpart in the low metamorphic grade Chilean rocks. These Paleozoic metasedimentary rocks were also intruded by Pennsylvanian and Jurassic granitoids.

Zircon geochronology of anatectic melts and residues from a highgrade pelitic assemblage at Ihosy, southern Madagascar: evidence for Pan-African granulite metamorphism

1996 ◽  
Vol 133 (3) ◽  
pp. 311-323 ◽  
Author(s):  
A. Kröner ◽  
I. Braun ◽  
P. Jaeckel
Keyword(s):  
Source Region ◽  
Granulite Facies ◽  
Detrital Zircons ◽  
High Grade ◽  
Left Behind ◽  
Granulite Metamorphism ◽  
Mozambique Belt ◽  
High Grade Metamorphism ◽  
Depositional Age ◽  
Heterogeneous Source

AbstractWe report U—Pb and207Pb/206Pb zircon ages for a granulite facies gneiss assemblage exposed in a large quarry at Ihosy, southern Madagascar. The granulites are derived from pelitic to arkosic sediments and attained equilibrium conditions at 650–700°C and 4–5 kbar. HigherP—Tconditions of 750–800°C and 6 kbar in the presence of low water activities have led to dehydration melting processes. The formation of granitic melts, which (partly) moved away from their source region, intruded into upper parts of the metapelitic gneisses as small granitic veins and left behind granulitic garnet-cordierite-quartz bearing rocks. Detrital zircons in a sample of metapelite and a sample of quartzofeldspathic gneiss yielded ages between ˜720 and ˜1855 Ma, suggesting a chronologically heterogeneous source region and a depositional age of less than ˜720 Ma for these rocks. High-grade metamorphism and anatexis are documented by zircon ages between 526 ±34 and 557 ±2 Ma with a mean age of about 550 Ma. The broad lithologies, metamorphic grades and ages recorded in the Ihosy rocks are similar to those in the Wanni Complex of northwestern Sri Lanka and in high-grade assemblages of southernmost India and support the contention that all these terrains were part of the Mozambique belt which formed as a result of collision of East and West Gondwana in latest Precambrian time.

Contrasting types of bladed olivine in ultramafic rocks from the Archean of Labrador

1976 ◽  
Vol 13 (3) ◽  
pp. 442-450 ◽  
Author(s):  
Kenneth D. Collerson ◽  
C. Wayne Jesseau ◽  
David Bridgwater
Keyword(s):  
Granulite Facies ◽  
Metamorphic Grade ◽  
Coarse Grained ◽  
Ultramafic Rocks ◽  
Host Rocks

Exceptionally coarse grained, interlocking olivine crystals up to 1 m long occur in small lenticular ultramafic bodies within the Nain Province of Labrador. The ultramafic rocks occur in association with Archean gneisses that vary in metamorphic grade from amphibolile fades to granulite facies. Some of the interlocking textures (i.e. near Hopedale) are interpreted as relict cumulate or harrisitic growths, mimicked by olivine regrowlh during metamorphism and preserved in structurally isotropic enclaves in their host rocks. Others (e.g. near Saglek) are regarded as solely of metamorphic origin. None of the olivine growths resemble spinifex textures reported in Archean ultramafic rocks elsewhere.

scholarly journals GEOLOGIA DA REGIÃO DE JEQUERI-VIÇOSA (MG), ORÓGENO ARAÇUAÍ MERIDIONAL

2013 ◽  
Author(s):  
Daniel Tavares Gradim ◽  
Gláucia Nascimento Queiroga ◽  
Tiago Amâncio Novo ◽  
Carlos Maurício Noce ◽  
Antônio Carlos Pedrosa-Soares ◽  
...  
Keyword(s):  
Partial Melting ◽  
Shear Zone ◽  
Granulite Facies ◽  
Minas Gerais ◽  
Amphibolite Facies ◽  
Ultramafic Rocks ◽  
Metamorphic Rocks ◽  
The West ◽  
Minas Gerais State ◽  
Araçuaí Orogen

RESUMO: A característica fundamental da região de Jequeri-Viçosa, situada no extremo sul do Orógeno Araçuaí, é a abundância de rochas metamórficas, ortoderivadas e paraderivadas, de fácies anfibolito alto e granulito. O embasamento paleoproterozóico é representado, a oeste, por ortognaisses tonalíticos a graníticos do Complexo Mantiqueira e, a leste, por ortognaisses charno-enderbíticos do Complexo Juiz de Fora. Ambos os complexos incluem anfibolitos e exibem intensidades variáveis de migmatização. O contato entre eles é marcado pela zona de cisalhamento transpressiva destral de Abre Campo, interpretada como uma sutura paleoproterozóica reativada no Neoproterozóico. O Anfibolito Santo Antônio do Grama e rochas meta-ultramáficas associadas (Córrego do Pimenta) representam restos ofiolíticos ediacaranos, colocados ao longo da Zona de Cisalhamento de Abre Campo. Assentada sobre o embasamento, na parte oeste da área, ocorre uma associação metavulcano-sedimentar neoproterozóica do Grupo Dom Silvério, composta por xistos diversos e quartzito. Na porção leste da área mapeada, a cobertura metassedimentar neoproterozóica é atribuída ao Grupo Andrelândia que inclui paragnaisse migmatítico e raro quartzito. Corpos de hidrotermalito quartzoso, indiscriminadamente associados às unidades do embasamento e da cobertura neoproterozóica, ocorrem ao longo de zonas de cisalhamento. Hidrotermalitos ferruginosos associam-se ao Complexo Mantiqueira na Zona de Cisalhamento de Ponte Nova. O granito foliado a milonitizado da Serra dos Vieiras parece ser um produto de fusão parcial do paragnaisse Andrelândia. Completam o quadro geológico os pegmatitos da Suíte Paula Cândico e diques de diabásio mesozóicos.Palavras-chave: Paleoproterozóico, Neoproterozóico, Orógeno AraçuaíABSTRACT: GEOLOGY OF THE JEQUERI-VIÇOSA REGION, MINAS GERAIS STATE, SOUTHERN ARAÇUAÍ OROGEN. This paper focuses on the southwestern sector of the Araçuaí orogen in a region located close to the boundary with the northern Ribeira orogen. This region is rich in ortho- and para-derived metamorphic rocks of the high amphibolite and granulite facies. The Paleoproterozoic basement includes, to the west, tonalitic to granitic orthogneisses of the Mantiqueira Complex and, to the east, enderbitic to charnockitic orthogneisses of the Juiz de Fora Complex. Both complexes also include amphibolite enclaves and show several rates of partial melting. The contact between them is marked by the dextral transpressional Abre Campo shear zone, considered to be a Paleoproterozoic suture reactivated during the Neoproterozoic Era. The Santo Antônio do Grama Amphibolite and associated meta-ultramafic rocks (Córrego do Pimenta) are Ediacaran ophiolite slivers emplaced along the Abre Campo shear zone. In the western part of the region, the Paleoproterozoic basement is locally covered by a metavolcano-sedimentary assemblage composed of amphibolite facies schist and quartzite of the Neoproterozoic Dom Silvério Group. To the east, the Neoproterozoic cover comprises the migmatized paragneiss and rare quartzite of the Andrelândia Group. The Serra dos Vieiras foliated to mylonitic granite seems to be formed from the partial melting of the Andrelândia paragneiss. Pegmatites of the Paula Cândido Suite and Mesosozic diabase dikes complete the geologic framework of the mapped area.Keywords: Paleoproterozoic, Neoproterozoic, Araçuaí Orogen

Intracratonic indentation of the Archean Slave Province into the Early Proterozoic Thelon Tectonic Zone of the Churchill Province, northwestern Canadian Shield

1990 ◽  
Vol 27 (12) ◽  
pp. 1699-1713 ◽  
Author(s):  
John B. Henderson ◽  
Peter H. McGrath ◽  
Reginald J. Theriault ◽  
Otto van Breemen
Keyword(s):  
Gravity Anomaly ◽  
Metamorphic Grade ◽  
Crustal Thickening ◽  
Positive Anomaly ◽  
The West ◽  
Tectonic Zone ◽  
Isostatic Rebound ◽  
Slave Province ◽  
Metamorphic Gradient ◽  
Middle Proterozoic

Some time between 1735 and 1840 Ma an intracratonic compression resulted in the indentation and consequent underthrusting of the eastern Thelon Tectonic Zone by the central Slave Province and part of the western Thelon Tectonic Zone. The wedge-shaped indentation involved major, transcurrent displacement on the McDonald and Bathurst fault systems. The affected region is characterized by (i) a prominent negative Bouguer gravity anomaly within the Slave Province between the faults and a smaller positive anomaly over the Thelon Tectonic Zone to the east, (ii) an easterly decreasing regional aeromagnetic field over the indenter, and (iii) an easterly increase in Proterozoic metamorphic grade. Rb–Sr dating of biotite shows a 1735 Ma "age plateau" in the eastern part of the wedge, whereas to the west the ages range between 2.0 and 2.5 Ga. Close coincidence between the margin of the 1735 Ma plateau, the metamorphic isograd pattern, and the negative gravity anomaly contours suggests a probable temporal and formative relationship between the metamorphic gradient, gravity anomaly, and the faults. Following indentation and resultant crustal thickening, isostatic rebound in the younger, weaker Thelon Tectonic Zone took place along older Thelon structures. In the older, stronger, structurally more homogeneous Slave Province, isostatic rebound was incomplete. A consequence of the indentation and rebound was crustal flexure to the east of the uplifted area, which resulted in the formation of the large structural basin, symmetrically disposed with respect to the indenting wedge, in which the originally more extensive Middle Proterozoic Thelon Formation is preserved.

scholarly journals Bedrock geology of the nunataks and semi-nunataks in the Frederikshåbs Isblink area of southern West Greenland

1970 ◽  
Vol 29 ◽  
pp. 1-60
Author(s):  
P.R Dawes
Keyword(s):  
Granulite Facies ◽  
Ultramafic Rocks ◽  
West Greenland ◽  
Precambrian Geology ◽  
Metamorphic History ◽  
Metavolcanic Rocks ◽  
Gneiss Granite ◽  
High Grade Metamorphism ◽  
Basic Rocks ◽  
Complex Display

The Precambrian geology of an area of 250 km2 within the old gneiss block ofWest Greenland is described. The area is composed of a gneiss-granite-amphibolite complex which is cut by later basic dykes. The largest part of the complex is made up of folded and migmatised biotite-, hornblende- and epldotebearing gneisses in which granodiorites and adamellites can be mapped as separate granite units. Different types of amphibolites and ultramafic rocks occur in the complex. The oldest amphibolites occur as migmatised and folded inclusions and tracts within the gneisses and these are cut by different generations of metabasite dykes which are themselves migmatised and deformed. Metavolcanic rocks containing pillow lavas and metagabbro layers exist on some nunataks and these are considered to form cover rocks to an earlier basement. Aspects of the deformational and metamorphic history are discussed. At least six main phases of deformation ean be recognised in rocks which are polymetamorphic. The gneisses and granites of the complex display amphibolite facies mineralogy but greenschist mineral assemblages characterise some of the amphibolite and ultramafic rocks. Relics of an early high-grade metamorphism, possibly reaching granulite facies conditions, are preserved in some basic rocks. The basic dykes which cut this polymetamorphic complex vary from dolerite to lamprophyre. The late tectonism and metamorphism is described. An attempt is made to place the area into the regional chronology of this part of West Greenland.

Geology and U-Pb geochronology of rocks of the Eokuk Uplift: a pre-2.8 Ga basement inlier in the northwestern Slave Province, Nunavut, Canada

1999 ◽  
Vol 36 (7) ◽  
pp. 1061-1082 ◽  
Author(s):  
K A Emon ◽  
V A Jackson ◽  
G R Dunning
Keyword(s):  
Granite Gneiss ◽  
Granulite Facies ◽  
High Grade ◽  
Zircon Age ◽  
Crustal Component ◽  
Slave Province ◽  
Zircon Crystallization ◽  
Intrusive Rocks ◽  
High Grade Metamorphism ◽  
Combined Data

Rocks of the Eokuk Uplift have been mapped in detail along the coast of Coronation Gulf and 10 key units have been dated by U-Pb analysis of zircon, monazite, and titanite. The combined data indicate that this inlier of the Slave Province has a >3.2 Ga crustal component, evidence of a granulite-grade orogenic event predating 2.8 Ga and a lack of evidence for any significant orogenic activity corresponding to the 2.7-2.6 Ga events common in the rest of the Slave Province. The oldest rocks in the study area are a succession of granitoid and supracrustal gneisses that have been metamorphosed to amphibolite to granulite facies. From field relationships, the oldest rock is a granodiorite to tonalite orthogneiss, with a zircon crystallization age of 3254+13-6 Ma. A granite gneiss, which may be a small felsic intrusion or an anatectic melt of the tonalite gneiss, yields a zircon age of 3216+14-13 Ma. A K-feldspar megacrystic monzogranite gneiss contains old, discordant, possibly inherited zircons with 207Pb/206Pb ages ranging from 3103 to 3039 Ma, together with coexisting 2879 ± 3 Ma zircon and monazite. These high-grade gneisses are intruded by two megacrystic granite plutons, dated at 2887 ± 2 and 2881+4-3 Ma. The absence of extensive recrystallization and complex structures in these plutons indicates that this igneous event postdated the high-grade metamorphism. An amphibolite-grade synplutonic metamorphic event is dated at ~2880 Ma by new monazite in the older gneiss units. A series of variably deformed mafic to felsic dykes and pegmatites intrude both the granites and gneisses and constrain the end of penetrative deformation in the area. Of these, a boudinaged diorite dyke, with a strong internal foliation parallel to the regional fabric, is dated at 2877 ± 3 Ma. A younger granodiorite dyke that crosscuts the regional fabric at a high angle and has only a weak internal foliation yields an age of 2864+3-9 Ma. An undeformed syenogranite pegmatite, which represents a suite that intrudes all other units in the study area, has a combined zircon-monazite age of 2852 ± 3 Ma. The varying degrees of deformation in these minor intrusive rocks constrains the end of deformation in the study area to ca. 2850 Ma. This contrasts with data from the rest of the Slave Province, where the main phases of deformation, metamorphism, and synmetamorphic plutonism have been dated at ca. 2.62-2.59 Ga. Metamorphic titanite ages from the diorite and granodiorite dykes indicate two lower amphibolite to greenschist facies metamorphic events: one at ca. 2705 Ma and one at ca. 2646 Ma. The youngest Archean magmatic event in the area is represented by granite intrusions at 2594+3-2 Ma, coeval with crystallization of titanite at greenschist-grade conditions in some of the older gneissic and intrusive rocks.

A garnet peridotite and a garnet-amphibole pyroxenite from South Harris, Outer Hebrides, and their bearing on the South Harris eclogite facies status

1967 ◽  
Vol 36 (279) ◽  
pp. 380-388 ◽  
Author(s):  
A. Livingstone
Keyword(s):  
Optical Properties ◽  
Granulite Facies ◽  
Garnet Peridotite ◽  
Ultramafic Rocks ◽  
Chemical Analyses ◽  
The South ◽  
Outer Hebrides ◽  
Eclogite Facies

SummaryA garnet-olivine metaperidotite and a garnet-amphibole pyroxenite are described. Chemical analyses are presented for six rocks and optical properties and chemical analyses are tabulated for clinopyroxene, almandine-pyrope garnet, and hastingsitie amphibole from the garnet-amphibole pyroxenite. A possible origin for the garnet peridotite and chemically similar granulite facies ultramafic rocks is suggested. The eclogite facies in South Harris is reinstated in the light of the data presented.

scholarly journals Supplemental Material: Detrital zircon geochronology and Hf isotope geochemistry of Mesozoic sedimentary basins in south-central Alaska: Insights into regional sediment transport, basin development, and tectonics along the NW Cordilleran margin

2020 ◽  
Author(s):  
C.R. Fasulo ◽  
et al.
Keyword(s):  
Sediment Transport ◽  
Detrital Zircon ◽  
Isotope Geochemistry ◽  
Sedimentary Basins ◽  
Detrital Zircons ◽  
Zircon Geochronology ◽  
Detrital Zircon Geochronology ◽  
South Central ◽  
Analytical Results ◽  
Cordilleran Margin

<div>Supplemental Data. (A) U-Pb analytical results from detrital zircons from the Nutzotin, Wrangell Mountains, and Wellesly basins. (B) Lu-Hf analytical results from detrital zircons from the Nutzotin and Wellesly basins. <br></div>

scholarly journals U–Pb Age and Hf Isotope Geochemistry of Detrital Zircons from Cambrian Sandstones of the Severnaya Zemlya Archipelago and Northern Taimyr (Russian High Arctic)

Minerals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 36 ◽  
Author(s):  
Victoria B. Ershova ◽  
Andrei V. Prokopiev ◽  
Andrey K. Khudoley ◽  
Tom Andersen ◽  
Kåre Kullerud ◽  
...  
Keyword(s):  
Detrital Zircon ◽  
Isotope Geochemistry ◽  
High Arctic ◽  
Detrital Zircons ◽  
Hf Isotope ◽  
Magmatic Arc ◽  
Novaya Zemlya ◽  
Late Neoproterozoic ◽  
Severnaya Zemlya ◽  
Severnaya Zemlya Archipelago

U–Pb and Lu–Hf isotope analyses of detrital zircons collected from metasedimentary rocks from the southern part of Kara Terrane (northern Taimyr and Severnaya Zemlya archipelago) provide vital information about the paleogeographic and tectonic evolution of the Russian High Arctic. The detrital zircon signatures of the seven dated samples are very similar, suggesting a common provenance for the clastic detritus. The majority of the dated grains belong to the late Neoproterozoic to Cambrian ages, which suggests the maximum depositional age of the enclosing sedimentary units to be Cambrian. The εHf(t) values indicate that juvenile magma mixed with evolved continental crust and the zircons crystallized within a continental magmatic arc setting. Our data strongly suggest that the main provenance for the studied clastics was located within the Timanian Orogen. A review of the available detrital zircon ages from late Neoproterozoic to Cambrian strata across the wider Arctic strongly suggests that Kara Terrane, Novaya Zemlya, Seward Peninsula (Arctic Alaska), Alexander Terrane, De Long Islands, and Scandinavian Caledonides all formed a single tectonic domain during the Cambrian age, with clastics predominantly sourced from the Timanian Orogen.

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