scholarly journals Juvenile crust formation in the Zimbabwe Craton deduced from the O-Hf isotopic record of 3.8–3.1 Ga detrital zircons

2017 ◽  
Vol 215 ◽  
pp. 432-446 ◽  
Author(s):  
Robert Bolhar ◽  
Axel Hofmann ◽  
Anthony I.S. Kemp ◽  
Martin J. Whitehouse ◽  
Sandra Wind ◽  
...  
Keyword(s):  
Detrital Zircons ◽  
Crust Formation ◽  
Zimbabwe Craton ◽  
Juvenile Crust

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.

scholarly journals The Itsaq Gneiss Complex of Greenland: Episodic 3900 to 3660 Ma juvenile crust formation and recycling in the 3660 to 3600 Ma Isukasian orogeny

2013 ◽  
Vol 313 (9) ◽  
pp. 877-911 ◽  
Author(s):  
A. P. Nutman ◽  
V. C. Bennett ◽  
C. R. L. Friend ◽  
H. Hidaka ◽  
K. Yi ◽  
...  
Keyword(s):  
Crust Formation ◽  
Gneiss Complex ◽  
Juvenile Crust

Juvenile crust formation in the northeastern Kaapvaal Craton at 2.97Ga—Implications for Archean terrane accretion, and the source of the Pietersburg gold

2013 ◽  
Vol 233 ◽  
pp. 20-43 ◽  
Author(s):  
Armin Zeh ◽  
Justine Jaguin ◽  
Marc Poujol ◽  
Philippe Boulvais ◽  
Sylvain Block ◽  
...  
Keyword(s):  
Kaapvaal Craton ◽  
Crust Formation ◽  
Juvenile Crust ◽  
Terrane Accretion

U–Pb zircon geochronology of Lower Jurassic and Paleozoic Stikinian strata and Tertiary intrusions, northwestern British Columbia

1995 ◽  
Vol 32 (8) ◽  
pp. 1155-1171 ◽  
Author(s):  
C. J. Greig ◽  
G. E. Gehrels
Keyword(s):  
Volcanic Rocks ◽  
Lower Jurassic ◽  
Detrital Zircons ◽  
Zircon Geochronology ◽  
Fold Belt ◽  
Isotopic Data ◽  
The West ◽  
Juvenile Crust ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

New U–Pb zircon ages are reported from western Stikinia. Devonian and Pennsylvanian ages of volcanic rocks at Oweegee dome confirm the presence of pre-Permian strata, and with Paleozoic and Triassic detrital zircons from Lower Jurassic sandstone, they help to demonstrate pre-Lower Jurassic deformation and uplift. The absence of pre-Paleozoic inherited zircon from all samples is consistent with Nd–Sr isotopic data which suggest that Stikinia consists mainly of juvenile crust. U–Pb ages for posttectonic intrusions suggest that structures in Skeena Fold Belt in the Kinskuch area formed prior to Eocene time. Five ages for felsic volcanic rocks from stratigraphically well-constrained upper parts of the Hazelton arc are approximately 196–199 Ma and suggest near-contemporaneity for cessation of volcanism in the areas studied. The Sinemurian or late Sinemurian – early Pliensbachian ages are older than previously reported U–Pb and biostratigraphic ages for presumed correlative rocks to the west, and westward-migrating volcanism is implied. Together with Toarcian fossils from overlying sandstone, the new ages suggest that a hiatus of moderate duration preceded regionally extensive sedimentation.

Insights into crust formation and recycling in North Africa from combined U–Pb, Lu–Hf and O isotope data of detrital zircons from Devonian sandstone of southern Libya

2013 ◽  
Vol 386 (1) ◽  
pp. 281-292 ◽  
Author(s):  
Guido Meinhold ◽  
Andrew C. Morton ◽  
C. Mark Fanning ◽  
James P. Howard ◽  
Richard J. Phillips ◽  
...  
Keyword(s):  
North Africa ◽  
Detrital Zircons ◽  
Crust Formation ◽  
Isotope Data ◽  
O Isotope

Extending the ancient margin outboard in the Canadian Cordillera: record of Proterozoic crust and Paleocene regional metamorphism in the Nicola horst, southern British Columbia

2002 ◽  
Vol 39 (11) ◽  
pp. 1605-1623 ◽  
Author(s):  
Philippe Erdmer ◽  
John M Moore ◽  
Larry Heaman ◽  
Robert I Thompson ◽  
Ken L Daughtry ◽  
...  
Keyword(s):  
British Columbia ◽  
Regional Metamorphism ◽  
Geological Mapping ◽  
Detrital Zircons ◽  
Source Rocks ◽  
Late Triassic ◽  
Low Grade ◽  
Rock Types ◽  
Ductile Flow ◽  
Juvenile Crust

The Nicola horst exposes plutonic and amphibolite-grade metamorphic rocks and is surrounded by low-grade arc rocks of the Late Triassic Nicola Group. We present new geological mapping and U–Pb, Nd, and metamorphic data for the Nicola horst near Bob Lake, ~40 km south of Kamloops, British Columbia. The Bob Lake assemblage includes felsic to intermediate metavolcaniclastic rocks, metaconglomerate, schist, phyllite, and other rock types. From U–Pb zircon analysis, a felsic metaporphyry clast in metaconglomerate is 1.04 Ga old. The oldest detrital zircons in metaconglomerate and schist are also near 1 Ga. The Bob Lake assemblage was intruded by 230 Ma tonalite, 219 Ma diorite, and 64 Ma leucogranite and includes 161 Ma felsic porphyry and 157 Ma rhyodacite. Amphibolite-grade metamorphism and ductile flattening and stretching affected all rocks except crosscutting Paleocene granite and granodiorite. The high-grade rocks may be exposed as a result of latest Cretaceous – Eocene extensional ductile flow beneath a thin brittle upper crust. A thickness of ~20 km of juvenile crust beneath the proposed Quesnel terrane is inconsistent with the evidence of Proterozoic source rocks at surface. We infer that most of the crustal lithosphere in this part of the Intermontane Belt is continental, which does not preclude possibly thick arc rocks in other parts. The local thinness of the Nicola Group, however, is inconsistent with emplacement as a regional allochthon and thus with their inclusion in a Quesnel "terrane." The Nicola arc succession appears to have been built on the ancient continental margin.

Growth of continental crust: a balance between preservation and recycling

2014 ◽  
Vol 78 (3) ◽  
pp. 623-637 ◽  
Author(s):  
K. C. Condie
Keyword(s):  
Continental Crust ◽  
Sedimentary Rocks ◽  
Ocean Basin ◽  
Detrital Zircons ◽  
Mantle Xenoliths ◽  
Isotopic Data ◽  
Remarkable Feature ◽  
Zircon Age ◽  
Continental Arc ◽  
Juvenile Crust

AbstractOne of the major obstacles to our understanding of the growth of continental crust is that of estimating the balance between extraction rate of continental crust from the mantle and its recycling rate back into the mantle. As a first step it is important to learn more about how and when juvenile crust is preserved in orogens. The most abundant petrotectonic assemblage preserved in orogens (both collisional and accretionary) is the continental arc, whereas oceanic terranes (arcs, crust, mélange, Large Igneous Provinces, etc.) comprise <10%; the remainder comprises older, reworked crust. Most of the juvenile crust in orogens is found in continental arc assemblages. Our studies indicate that most juvenile crust preserved in orogens was produced during the ocean-basin closing stage and not during the collision. However, the duration of ocean-basin closing is not a major control on the fraction of juvenile crust preserved in orogens; regardless of the duration of subduction, the fraction of juvenile crust preserved reaches a maximum of ∼50%. Hafnium and Nd isotopic data indicate that reworking dominates in external orogens during supercontinent breakup, whereas during supercontinent assembly, external orogens change to retreating modes where greater amounts of juvenile crust are produced. The most remarkable feature of εNd (sedimentary rocks and granitoids) and εHf (detrital zircons) distributions through time is how well they agree with each other. The ratio of positive to negative εNd and eHf does not increase during supercontinent assembly (coincident with zircon age peaks), which suggests that supercontinent assembly is not accompanied by enhanced crustal production. Rather, the zircon age peaks probably result from enhanced preservation of juvenile crust. Valleys between zircon age peaks probably reflect recycling of continental crust into the mantle during supercontinent breakup. Hafnium isotopic data from zircons that have mantle sources, Nd isotopic data from detrital sedimentary rocks and granitoids and whole-rock Re depletion ages of mantle xenoliths collectively suggest that ≥70% of the continental crust was extracted from the mantle between 3500 and 2500 Ma.

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