Two types of accretionary complexes in the eastern Mongol–Okhotsk Belt: Constraints from U–Pb and Hf isotopic data of detrital zircons from metasedimentary rocks of the Selemdzha and Tokur terranes

2020 ◽  
Vol 201 ◽  
pp. 104508
Author(s):  
Victor A. Zaika ◽  
Andrey A. Sorokin
Keyword(s):  
Detrital Zircons ◽  
Isotopic Data ◽  
Metasedimentary Rocks

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.

Geochemistry of the Namurian Lismore Formation, northern mainland Nova Scotia: sedimentation and tectonic activity along the southern flank of the Maritimes Basin

1999 ◽  
Vol 36 (10) ◽  
pp. 1655-1669 ◽  
Author(s):  
Jacquelyn E Stevens ◽  
J Brendan Murphy ◽  
Fred W Chandler
Keyword(s):  
Nova Scotia ◽  
Tectonic Activity ◽  
Isotopic Data ◽  
Rock Fragments ◽  
Metasedimentary Rocks ◽  
Clastic Rocks ◽  
Granitoid Rocks ◽  
Maritimes Basin ◽  
Group B ◽  
Southern Flank

Geochemical and isotopic data from the clastic rocks of the Namurian Lismore Formation in mainland Nova Scotia identify key episodes of tectonic activity during the development of the Maritimes Basin in Atlantic Canada. The Lismore Formation forms part of the Mabou Group and is an upward-coarsening 2500 m thick fluvial sequence deposited in the Merigomish sub-basin along the southern flank of the Maritimes Basin. Based on stratigraphic evidence, the Lismore Formation can be divided into upper and lower members which reflect variations in depositional environment and paleoclimate. The geochemical and isotopic data may also be subdivided into two groupings that primarily reflect varying contributions from accessory phases, clay minerals, or rock fragments. This subdivision occurs 115 m above the base of the upper member. The data from the lower grouping (group A) show an important contribution from underlying Silurian rocks, with a relatively minor contribution from Late Devonian granitoid rocks from the adjacent Cobequid Highlands and possibly metasedimentary rocks from the Meguma Terrane to the south. The data from the upper grouping (group B) reveal a more important contribution from the Cobequid Highlands granitoid rocks. This variation in geochemistry is thought to constrain the age of renewed motion and uplift along the faults along the southern flank of the Maritimes Basin and, more generally, suggests that geochemical and isotopic data of continental clastic rocks may help constrain the age of tectonic events that influence deposition of basin-fill rocks.

Detrital chromites reveal Slave craton’s missing komatiite

Geology ◽  
2021 ◽  
Author(s):  
Rasmus Haugaard ◽  
Pedro Waterton ◽  
Luke Ootes ◽  
D. Graham Pearson ◽  
Yan Luo ◽  
...  
Keyword(s):  
Narrow Range ◽  
Thermal Evolution ◽  
Group Element ◽  
Detrital Zircons ◽  
Isotopic Data ◽  
Crust Formation ◽  
Slave Craton ◽  
Provenance Studies ◽  
Juvenile Crust ◽  
Greenstone Belts

Komatiitic magmatism is a characteristic feature of Archean cratons, diagnostic of the addition of juvenile crust, and a clue to the thermal evolution of early Earth lithosphere. The Slave craton in northwest Canada contains >20 greenstone belts but no identified komatiite. The reason for this dearth of komatiite, when compared to other Archean cratons, remains enigmatic. The Central Slave Cover Group (ca. 2.85 Ga) includes fuchsitic quartzite with relict detrital chromite grains in heavy-mineral laminations. Major and platinum group element systematics indicate that the chromites were derived from Al-undepleted komatiitic dunites. The chromites have low 187Os/188Os ratios relative to chondrite with a narrow range of rhenium depletion ages at 3.19 ± 0.12 Ga. While these ages overlap a documented crust formation event, they identify an unrecognized addition of juvenile crust that is not preserved in the bedrock exposures or the zircon isotopic data. The documentation of komatiitic magmatism via detrital chromites indicates a region of thin lithospheric mantle at ca. 3.2 Ga, either within or at the edge of the protocratonic nucleus. This study demonstrates the applicability of detrital chromites in provenance studies, augmenting the record supplied by detrital zircons.

Nd isotopic characteristics of metamorphic and plutonic rocks of the Coast Mountains near Prince Rupert, British Columbia

1998 ◽  
Vol 35 (5) ◽  
pp. 556-561 ◽  
Author(s):  
P J Patchett ◽  
G E Gehrels ◽  
C E Isachsen
Keyword(s):  
British Columbia ◽  
Volcanic Rocks ◽  
Metamorphic Rocks ◽  
Published Data ◽  
Isotopic Data ◽  
Crustal Component ◽  
Coast Mountains ◽  
Crustal Rocks ◽  
Metasedimentary Rocks ◽  
Plutonic Rocks

Nd isotopic data are presented for a suite of metamorphic and plutonic rocks from a traverse across the Coast Mountains between Terrace and Prince Rupert, British Columbia, and for three contrasting batholiths in the Omineca Belt of southern Yukon. A presumed metamorphic equivalent of Jurassic volcanic rocks of the Stikine terrane gives epsilon Nd = +6, and a number of other metaigneous and metasedimentary rocks in the core of the Coast Mountains give epsilon Nd values from +3 to +7. A single metasedimentary rock approximately 3 km east of the Work Channel shear zone gives a epsilon Nd value of -9. Coast Belt plutons in the traverse yield epsilon Nd from -1 to +2. The Omineca Belt plutons give epsilon Nd from -10 to -17. All results are consistent with published data in demonstrating that (i) juvenile origins for both igneous and metamorphic rocks are common in the Coast Belt; (ii) representatives of a continental-margin sedimentary sequence with Precambrian crustal Nd are tectonically interleaved in the Coast Mountains; (iii) Coast Mountains plutons can be interpreted as derived from a blend of metamorphic rocks like those seen at the surface, or as arc-type melts contaminated with the older crustal component; and (iv) Omineca Belt plutons are dominated by remelted Precambrian crustal rocks.

scholarly journals Supplemental Material: Protracted northward drifting of South China during the assembly of Gondwana: Constraints from the spatial-temporal provenance comparison of Neoproterozoic–Cambrian strata

2020 ◽  
Author(s):  
Qiong Chen ◽  
Guochun Zhao ◽  
et al.
Keyword(s):  
South China ◽  
Detrital Zircons ◽  
Isotopic Data

Table S1: In-situ U-Pb ages and Hf isotopic data of detrital zircons from the Neoproterozoic–Cambrian samples from the western and eastern margins of South China.

The Parry Sound domain: a far-travelled allochthon? New evidence from U–Pb zicon geochronology

1996 ◽  
Vol 33 (7) ◽  
pp. 1087-1104 ◽  
Author(s):  
N. Wodicka ◽  
R. A. Jamieson ◽  
R. R. Parrish
Keyword(s):  
Source Region ◽  
Detrital Zircons ◽  
Absolute Maximum ◽  
Present Position ◽  
Mafic Dyke ◽  
Metasedimentary Rocks ◽  
Thrust Zone ◽  
Tonalitic Gneiss ◽  
Central Gneiss Belt ◽  
New Evidence

We report U–Pb zircon ages for metaplutonic and metasedimentary rocks from three lithotectonic assemblages within the Parry Sound allochthon of the Central Gneiss Belt, southwestern Grenville Orogen: the basal Parry Sound, interior Parry Sound, and Twelve Mile Bay assemblages. Magmatic crystallization ages for granitic to tonalitic gneisses from the basal Parry Sound assemblage fall in the range 1400–1330 Ma. Younger intrusions include the Parry Island anorthosite dated at 1163 ± 3 Ma and a crosscutting mafic dyke bracketed between 1151 and 1163 Ma. Dated at [Formula: see text] a tonalitic gneiss from the overlying interior Parry Sound assemblage is slightly younger than the older group of rocks from the basal Parry Sound assemblage. 207Pb/206Pb ages for zircons from a quartzite of the basal Parry Sound assemblage range from 1385 Ma to the Neoarchaean. An absolute maximum age for this quartzite is 1436 ± 17 Ma. In contrast, detrital zircons from a quartzite of the Twelve Mile Bay assemblage constrain the age of deposition at post-ca. 1140–1120 Ma. We speculate that Grenvillian-age zircons within this quartzite were derived from rocks in the Adirondack Highlands and Frontenac terrane, implying that part of the Parry Sound domain and these terranes were contiguous during deposition of the quartzite. Our data support previous interpretations that the Parry Sound domain is allochthonous with respect to its surroundings, and suggest that the most likely source region of the basal Parry Sound domain lies southeast of the Central Gneiss Belt, within the Central Metasedimentary Belt boundary thrust zone or the Adirondack Highlands. This implies the possibility of 100–300 km of displacement of the domain. Emplacement of the Parry Sound domain into its present position must have occurred relatively late in the orogen's history, by about 1080 Ma.

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.

Resistance of zircons to U–Pb resetting in a prograde metamorphic sequence of Caledonian age in East Greenland

1985 ◽  
Vol 22 (3) ◽  
pp. 330-338 ◽  
Author(s):  
J. J. Peucat ◽  
D. Tisserant ◽  
R. Caby ◽  
N. Clauer
Keyword(s):  
Source Area ◽  
Detrital Zircons ◽  
Metamorphic Event ◽  
Great Resistance ◽  
East Greenland ◽  
Geological Interpretation ◽  
Source Areas ◽  
Metasedimentary Rocks ◽  
Sedimentary Source

In the Alpefjord area, Caledonian metamorphism from the chlorite zone to the sillimanite zone is seen to cut across the sedimentary pile of the lower Eleonore Bay Group. Zircons have been collected from quartzite layers enriched in heavy minerals.U–Pb zircon dating in the chlorite and the sillimanite zones does not reveal the Caledonian event but, instead, previous episodes at 1100 and 2500 Ma ago. The Caledonian event can be recognized in anatectic gneisses where detrital zircons are surrounded by overgrowths, K–Ar and Rb–Sr methods yield 1030–410 Ma ages on micas, with a positive correlation between the degree of apparent reselling of mica ages and the grade of the Caledonian metamorphism.The following geological interpretation of the age data is proposed. (1) A major metamorphic event occurred around 1100 Ma ago in the source area for the lower Eleonore Bay Group sediments. During this Grenvillian event, Archaean detrital zircons were affected by an episodic lead loss and a muscovite phase recorded the cooling and uplift of a basement source area. (2) Erosion of this source area occurred after 1100 Ma, followed by sedimentation of the lower Eleonore Bay Group [Formula: see text]. The 2500–1100 Ma U–Pb system remained nearly a closed system during Caledonian metamorphism up to and including sillimanite-zone conditions.This example shows the great resistance or inherited zircons to an important secondary Pb loss during Caledonian metamorphism and consequently shows that the lower-intercept ages of zircons from metasedimentary rocks do not always record the last metamorphic event observed in situ, but retain memories of previous geological events in the sedimentary source areas. By contrast, zircons separated from quartzitic xenoliths in migmatitic gneisses have recorded a disturbance in their U–Pb systems that corresponds to Caledonian partial melting.

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