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.

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.

Nature of the Quetico–Wabigoon boundary in the de Courcey – Smiley Lakes area, northwestern Ontario

1976 ◽  
Vol 13 (6) ◽  
pp. 737-748 ◽  
Author(s):  
Manfred M. Kehlenbeck
Keyword(s):  
Regional Metamorphism ◽  
Sedimentary Rocks ◽  
Metamorphic Grade ◽  
Boundary Zone ◽  
Present Level ◽  
Metasedimentary Rocks ◽  
The North ◽  
Northwestern Ontario ◽  
Multiple Phase ◽  
Mineral Assemblages

In the de Courcey – Smiley Lakes Area, the boundary between the Quetico and Wabigoon Belts is expressed by a sequence of pelitic to semi-pelitic schists and gneisses. At the present level of erosion, these metasedimentary rocks are in contact with granodioritic gneisses, granites, and pegmatites, which are exposed to the south.To the north of this area, regional metamorphism of volcanic and sedimentary rocks has resulted in greenschist facies assemblages, which characterize the Wabigoon Belt in general. In the boundary zone, the metamorphic grade increases southward toward de Courcey and Smiley Lakes.Formation of three distinct foliation surfaces was accompanied by syn-tectonic as well as post-tectonic recrystallization, producing polymetamorphic schists.In the boundary zone, mineral assemblages comprising andalusile, sillimanite, cordierite, garnet. biotite, and muscovite form a facies series of the Abukuma type.The boundary between the Quetico and Wabigoon Belts in this area is a complex zone in which rocks of both belts have been reconstituted by multiple-phase metamorphism and partial melting.

scholarly journals Recycling of Paleoproterozoic and Neoproterozoic crust recorded in Lower Paleozoic metasandstones of the Northern Gemericum (Western Carpathians, Slovakia): Evidence from detrital zircons

2019 ◽  
Vol 70 (4) ◽  
pp. 298-310
Author(s):  
Anna Vozárová ◽  
Nickolay Rodionov ◽  
Katarína Šarinová
Keyword(s):  
Detrital Zircon ◽  
Detrital Zircons ◽  
Western Carpathians ◽  
Published Data ◽  
Lower Paleozoic ◽  
Metasedimentary Rocks ◽  
Late Neoproterozoic ◽  
Central Western Carpathians ◽  
A Minor ◽  
Detrital Zircon Ages

Abstract U–Pb (SHRIMP) detrital zircon ages from the Early Paleozoic meta-sedimentary rocks of the Northern Gemericum Unit (the Smrečinka Formation) were used to characterize their provenance. The aim was to compare and reconcile new analyses with previously published data. The detrital zircon age spectrum demonstrates two prominent populations, the first, Late Neoproterozoic (545–640 Ma) and the second, Paleoproterozoic (1.8–2.1 Ga), with a minor Archean population (2.5–3.4 Ga). The documented zircon ages reflect derivation of the studied metasedimentary rocks from the Cadomian arc, which was located along the West African Craton. The acquired data supports close relations of the Northern Gemericum basement with the Armorican terranes during Neoproterozoic and Ordovician times and also a close palinspastic relation with the other crystalline basements of the Central Western Carpathians. In comparison, the detrital zircons from the Southern Gemericum basement and its Permian envelope indicate derivation from the Pan-African Belt–Saharan Metacraton provenance.

scholarly journals Age and sources of the metasedimrntary rocks of the Tokur terrane in the Mongol-Okhotsk fold belt: results of the U–Pb geoсhronological and Lu–Hf isotope studies

2019 ◽  
Vol 486 (4) ◽  
pp. 446-450
Author(s):  
V. A. Zaika ◽  
A. A. Sorokin ◽  
A. P. Sorokin
Keyword(s):  
Detrital Zircons ◽  
Hf Isotope ◽  
Fold Belt ◽  
Metasedimentary Rocks ◽  
The North ◽  
Icp Ms ◽  
North Asia ◽  
Southeastern Margin ◽  
Isotope Studies ◽  
Metamorphic Complexes

This paper presents the results of U–Pb (LA–ICP–MS) and Lu–Hf ­isotope studies of detrital zircons from metasedimentary rocks of the Tokur Terrane. It has been shown that metasedimentary rocks of the Tokur and Ekimchan formations are characterized by similar age peaks of detrital zircons, which indicates a close (or same) age of these formations. The lower age of the sedimentation is determined by the age of the youngest zircons of 326–323 Ma. The upper age boundary is determined of 254–251 Ma, based on the intruded of the Late Permian granitoids. The main sources of zircons in the metasedimentary rocks of the Tokur Terrane are the igneous and metamorphic complexes of the southeast framing of the North Asia Craton. The Tokur Terrane can be considered as a fragment of the Paleozoic accretionary complex, the formation in front of the southeastern margin of the North Asia Craton.

scholarly journals New data on age of the Neoproterozoic volcanic rocks of Isakovka Terrain from the Sayan-Yenisei accretion belt (U-Pb, zircon)

2019 ◽  
Vol 488 (5) ◽  
pp. 521-525
Author(s):  
P. S. Kozlov ◽  
I. I. Likhanov ◽  
K. S. Ivanov ◽  
A. D. Nozhkin ◽  
S. V. Zinoviev
Keyword(s):  
Oil And Gas ◽  
Volcanic Rocks ◽  
Island Arc ◽  
Yenisei Ridge ◽  
Junction Zone ◽  
The West ◽  
Late Precambrian ◽  
Unconventional Oil And Gas ◽  
Late Neoproterozoic ◽  
First Time

The Late Neoproterozoic U-Pb age for zircon of island-arc metadacites (691 8.8 million years) and basalts (572 6.5 million years) of the Kiselikhinskaya Formation of the Kutukasskaya Group was established for the first time. The manifestation of basaltic volcanism is associated with rift-related processes. The studies clarify the Late Precambrian stratigraphy of the Yenisei Ridge and the features of the evolution of the Sayan-Yenisei accretionary belt at the Neoproterozoic stage of its history. Folded-thrust structures of the junction zone of the Yenisei Ridge with the West Siberian Plate may be favorable in relation to the search for unconventional oil and gas traps.

U–Pb geochronology of detrital zircons from a continental margin assemblage in the northern Coast Mountains, southeastern Alaska

1991 ◽  
Vol 28 (8) ◽  
pp. 1285-1300 ◽  
Author(s):  
George E. Gehrels ◽  
William C. McClelland ◽  
Scott D. Samson ◽  
P. Jonathan Patchett
Keyword(s):  
Continental Margin ◽  
North American ◽  
Detrital Zircons ◽  
Northern Coast ◽  
Coast Mountains ◽  
Metasedimentary Rocks ◽  
The North ◽  
Upper Proterozoic ◽  
Two Samples ◽  
Cordilleran Margin

Metamorphic rocks within and west of the northern Coast Mountains in southeastern Alaska consist of an Upper Proterozoic(?) to upper Paleozoic continental margin assemblage that we interpret to belong to the Yukon-Tanana terrane. U–Pb geochronologic analyses of single detrital zircon grains from four samples of quartzite suggest that the zircons were shed from source regions containing rocks of ~495 Ma, ~750 Ma, 1.05–1.40 Ga, 1.75–2.00 Ga, ~2.3 Ga, 2.5–2.7 Ga, and ~3.0 Ga. Multigrain fractions from two samples yield upper intercepts between 2.0 and 2.3 Ga, but the scarcity of single grains of similar age suggests that these fractions comprise a mixture of < 2.0 and > 2.3 Ga grains. Zircons in these rocks generally overlap in age with (i) detrital zircons in metasedimentary rocks of the Yukon–Tanana terrane in eastern Alaska and Yukon, (ii) detrital zircons in strata of the Cordilleran miogeocline, and (iii) plutonic and gneissic rocks that intrude or are overlain by miogeoclinal strata. In addition, the pre-1.7 Ga grains overlap in age with dated crystalline rocks of the western Canadian Shield. These similarities raise the possibility that metaclastic rocks in the northern Coast Mountains accumulated in proximity to western North America. The younger zircon populations were likely shed from mid-Proterozoic to early Paleozoic igneous rocks that now occur locally (but may have been widespread) along the Cordilleran margin. Recognition of a continental margin assemblage of possible North American affinity in the Coast Mountains raises the possibility that some arc-type and oceanic terranes inboard of the Coast Mountains may be large klippen that have been thrust over the North American margin.

U–Pb and Hf isotopic study of detrital zircons from the Lüliang khondalite, North China Craton, and their tectonic implications

2009 ◽  
Vol 146 (5) ◽  
pp. 701-716 ◽  
Author(s):  
XIAOPING XIA ◽  
MIN SUN ◽  
GUOCHUN ZHAO ◽  
FUYUAN WU ◽  
LIEWEN XIE
Keyword(s):  
North China Craton ◽  
North China ◽  
Detrital Zircons ◽  
Crustal Material ◽  
Isotopic Data ◽  
Isotopic Study ◽  
Metasedimentary Rocks ◽  
The North ◽  
Wide Range ◽  
Western Block

AbstractTwo types of metasedimentary rocks occur in the Trans-North China Orogen of the North China Craton. One type consists of highly metamorphosed supracrustal rocks with protoliths of mature cratonic shale, called khondalites, as found in the Lüliang Complex; rocks of the other type are also highly metamorphosed but less mature, as represented by the Wanzi supracrustal assemblage in the Fuping Complex. U–Pb isotopic data for detrital zircons from khondalites show a provenance dominated by 1.9–2.1 Ga Palaeoproterozoic rocks. These detrital zircons display a wide range of εHfvalues from −16.0 to +9.2 and give Hf isotopic model ages mostly around 2.3 Ga. The high positive εHfvalues approach those for the depleted mantle at 2.1 Ga, highlighting a juvenile crustal growth event in Palaeoproterozoic times. Hf isotopic data also imply thatc.2.6 Ga old crustal material was involved in the Palaeoproterozoic magmatic event. These data are similar to those for the khondalitic rocks from the interior of the Western Block of the North China Craton, suggesting a common provenance. In contrast, other metasedimentary rocks in the Trans-North China Orogen, such as the Wanzi supracrustal assemblage in the Fuping Complex, have a source region with both Palaeoproterozoic and Archaean rocks. Their detrital zircon Hf isotopic data indicate reworking of old crustal material and a lack of significant juvenile Palaeoproterozoic magmatic input. These rocks are similar to the coevally deposited meta-sedimentary rocks in the interior of the Eastern Block. We propose that the Lüliang khondalites were deposited on the eastern margin of the Western Block in a passive continental margin environment and were thrust eastward later during collision with the Eastern Block. Other metasedimentary rocks in the Trans-North China Orogen were deposited on the western margin of the Eastern Block in a continental arc environment. Our data support the eastward subduction model for the Palaeoproterozoic tectonic evolution of the North China Craton.

The Twillingate Granite and nearby Volcanic Groups: An Island Arc Complex In Northeast Newfoundland

1975 ◽  
Vol 12 (6) ◽  
pp. 982-995 ◽  
Author(s):  
Harold Williams ◽  
John G. Payne
Keyword(s):  
Volcanic Rocks ◽  
Metamorphic Grade ◽  
Island Arc ◽  
Granitic Rocks ◽  
Arc Volcanism ◽  
Pillow Lavas ◽  
The North ◽  
Structural Style ◽  
Lower Ordovician ◽  
Island Arc Volcanism

The Twillingate Granite cuts mafic pillow lavas and silicic fragmental volcanic rocks of the Sleepy Cove Group. The granitic rocks are soda-rich and they vary from intensely foliated and mylonitic in the south to mildly foliated and massive toward the north. The Sleepy Cove volcanic rocks show similar structural and metamorphic variations from lineated amphibolitic pillow lavas, to elongated pillows of greenschist metamorphic grade, to slightly metamorphosed and relatively undeformed pillow lavas.The collective terrane occupied by the Twillingate Granite and Sleepy Cove Group is virtually surrounded by intrusive mafic dikes that are integral and coeval parts of the Moretons Harbour and Herring Neck Groups. The dikes decrease in abundance away from the contacts of the collective Twillingate – Sleepy Cove terrane. The essentially intrusive contact is modified by faults and locally, the profuse dike swarms are absent.Regional relationships, thickness, lithofacies, and petrochemistry all indicate that the Moretons Harbour and Herring Neck Groups relate to an episode of Lower Ordovician island arc volcanism. Intrusive relationships and contrasts in structural style and metamorphic grade indicate that the Twillingate Granite and Sleepy Cove Group are older. These older rocks are also interpreted as island arc derivatives, so that in their present position, they may represent the remnant of a partly deformed and metamorphosed older arc that is now bordered by relatively undeformed Lower Ordovician volcanic rocks.Similar relationships within transported sequences of western Newfoundland suggest a central Newfoundland island arc provenance for the transported Little Port Complex.

scholarly journals The Kohistan between Gilgit and Chilas, northern Pakistan: regional tectonic implications

1996 ◽  
Vol 14 ◽  
Author(s):  
T. Khan ◽  
M. A. Khan ◽  
M. Q. Jan ◽  
M. Latif
Keyword(s):  
Sedimentary Rocks ◽  
Oceanic Island ◽  
Island Arc ◽  
Northern Pakistan ◽  
The Past ◽  
Volcanic Group ◽  
The North ◽  
Regional Tectonic ◽  
Back Arc ◽  
Field Geology

In this paper, we present geological description of an area located between Gilgit and Chilas within the Kohistan terrane. This terrane has been considered an intra-oceanic island arc, formed due to northward subduction of the Neo-tethyan lithospheric plate. At present, it is squeezed between the Karakoram­ Asian and Indian continental plates. Both the contacts are marked by suture zones, that is, Shyok (MKT) in the north and Indus (MMT) sutures in the south, respectively. The investigated area consists of plutonic, metamorphosed volcanic and sedimentary rocks, the Chilas Complex, and the Kamila Amphibolite. The metamorphosed volcanic and sedimentary rocks are packaged into the Jagfot Group. This group comprises basal turbiditic sediments, intercalated with amphibolites and calc-silicates (the Gilgit Formation), followed upward by the Gashu-Confluence Volcanics = Chait Volcanic Group, and finally the Thelichi Formation = Yasin Group of Aptian-Albian age. The Thelichi Formation comprises a volcanic base (Majne volcanics) and overlying turbidites, local intercalation of marbles, volcaniclastics and lava flows. Greenschist and amphibolite facies are common in the Jaglot Group, and particularly the sillimanite in the Gilgit Formation. A pair of anticline (the Gilgit anticline) and syncline (the Jaglot syncline) make up the structural scenario. On the basis of field geology, we conclude that the entire Jaglot Group and its equivalents, the Yasin Group, Chait Volcanic Group in Kohistan, and Burjila Formation, Bauma Harel Formation and Katzarah Formation in Ladakh show intra-oceanic back-arc basin rather than island arc affinities as suggested in the past.

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