Gondwanan Eoarchean–Neoproterozoic ancient crustal material in Iran and Turkey: zircon U–Pb–Hf isotopic evidence

2014 ◽  
Vol 51 (3) ◽  
pp. 272-285 ◽  
Author(s):  
Allen P. Nutman ◽  
Mohammad Mohajjel ◽  
Vickie C. Bennett ◽  
Chris L. Fergusson
Keyword(s):  
Northeast India ◽  
Granitic Rocks ◽  
Magmatic Zircon ◽  
Crustal Material ◽  
Isotopic Data ◽  
Crystalline Complex ◽  
Crustal Component ◽  
Menderes Massif ◽  
Sanandaj Sirjan Zone ◽  
Archean Crust

The Sanandaj–Sirjan Zone is a basement culmination northeast of the Neo-Tethys suture in Iran. In this zone near Azna, granite has a magmatic zircon U–Pb age of 568 ± 11 Ma, with 900–800, ca. 2400, and ca. 3600 Ma inherited cores. The ca. 3600 Ma inherited zircon is the oldest crustal component yet detected in Iran. Near Chadegan, orthogneiss has a magmatic zircon U–Pb age of 637 ± 15 Ma, and carries ca. 1000 and 2000 Ma inherited zircons. Inherited 900–1000 Ma zircons have juvenile initial εHf values of ca. +8 to +9, whereas the younger 630 and 568 Ma magmatic zircons show lower initial εHf values; however, the 3600 Ma core has initial εHf = 0.0. A Neoproterozoic rim on the inherited 3600 Ma core has the most extreme initial εHf value of −18. The Hf isotopic data indicates generation of the magmatic protoliths from a mixture of juvenile Neoproterozoic and Archean sources. Previous studies showed that in Turkey the Central Anatolian Crystalline Complex is underlain by Neo-Eoarchean rocks, the Menderes Massif contains Neoproterozoic granitoids, and that central Iran’s basement and the northern Sanandaj–Sirjan Zone contain Neoproterozoic granitic rocks. This basement terrane is from Gondwana, and was transferred across Paleo-Tethys to dock against Eurasia’s southern margin. Occurrence in Iran and Turkey of Eoarchean crust raises the possibility of sinistral migration of this terrane in the closure of Tethys because the nearest known early Archean crust occurs in northeast India.

scholarly journals New zircon radiometric U-Pb ages and Lu-Hf isotopic data from the ultramafic-mafic sequences of Ranau and Telupid (Sabah, eastern Malaysia): Time to reconsider the geological evolution of Southeast Asia?

Geology ◽  
2021 ◽  
Author(s):  
Basilios Tsikouras ◽  
Chun-Kit Lai ◽  
Elena Ifandi ◽  
Nur’Aqidah Norazme ◽  
Chee-Hui Teo ◽  
...  
Keyword(s):  
Ultramafic Rocks ◽  
Crustal Material ◽  
Isotopic Data ◽  
Backarc Basin ◽  
Crustal Component ◽  
Sulu Sea ◽  
Potential Source ◽  
Depleted Mantle ◽  
Geological Evolution ◽  
Mantle Reservoir

New zircon U-Pb geochronology from a peridotite suite near Ranau and the Telupid ophiolite in Sabah, eastern Malaysia, contradict previous studies, which assumed that the Sabah mafic-ultramafic rocks are largely ophiolitic and Jurassic–Cretaceous in age. We show that these rocks formed during a magmatic episode in the Miocene (9.2–10.5 Ma), which is interpreted to reflect infiltration of melts and melt-rock reaction in the Ranau subcontinental peridotites during extension, and concurrent seafloor spreading forming the Telupid ophiolite further south. Older zircons from the Ranau peridotites have Cretaceous, Devonian, and Neoproterozoic ages. Zircon Lu-Hf isotopic data suggest their derivation from a depleted mantle. However, significant proportions of crustal components have been incorporated in their genesis, as evidenced by their less-radiogenic Hf signature compared to a pristine mantle reservoir. The involvement of a crustal component is consistent with our interpreted continental setting for the Ranau peridotite and formation in a narrow backarc basin for the Telupid ophiolite. We infer that the Sulu Sea, which was expanding throughout much of the Miocene, may have extended to the southwest into central Sabah. The Telupid oceanic strand formed during the split, collapse, and rollback of the Sulu arc due to the subduction of the Celebes Sea beneath Sabah. Incorporation of the Sulu arc in the evolving Miocene oceanic basin is a potential source to explain the involvement of crustal material in the zircon evolution of the Telupid ophiolite.

Geochemical and isotopic studies of the sedimentary and granitic rocks of the Altai orogen of northwest China and their tectonic implications

2002 ◽  
Vol 139 (1) ◽  
pp. 1-13 ◽  
Author(s):  
BIN CHEN ◽  
BOR-MING JAHN
Keyword(s):  
Oceanic Crust ◽  
Significant Proportion ◽  
Northwest China ◽  
Passive Margin ◽  
Granitic Rocks ◽  
Crustal Material ◽  
Isotopic Data ◽  
Margin Setting ◽  
Metasedimentary Rocks ◽  
Back Arc

The Altai orogen (northwest China) represents the southwestern margin of the Central Asian Orogenic Belt. Geochemical and Nd–Sr isotope analyses were carried out on the Palaeozoic sedimentary and granitic rocks in order to trace their sources and to evaluate the pattern of continental growth of the orogen. Nd isotopic data for both the granites and sediments suggest a significant proportion of middle Proterozoic crust beneath the Altai orogen. However, addition of juvenile material (arc/back-arc oceanic crust) during Palaeozoic times is also significant. Trace elements and isotopic data of sediments suggest their sources were immature. They represent mixtures between a Palaeozoic juvenile component and an evolved continental crust. The early Palaeozoic sediments show εNd(T) = −3.4 to −5.0, TDM = 1.5–1.8 Ga, and ISr = 0.710–0.712. They represent a passive margin setting, with a predominance of evolved crustal material in the source. The Devonian sequences, however, might have been deposited in a back-arc basin setting, produced by subduction of the Junggar oceanic crust along the Irtysh fault. A significant addition of arc material into the sedimentary basin is responsible for the highly variable εNd values (−6 to 0) and ISr (0.711–0.706). The Carboniferous rocks were also deposited in a back-arc basin setting but with predominantly arc material in the source as suggested by an abrupt increase in εNd(T) (+6 to +3) and decrease in ISr (0.7045–0.7051). Voluminous syn-orogenic granitoids have εNd(T) = +2.1 to −4.3, ISr = 0.705–0.714 and TDM = 0.7–1.6 Ga. They were not derived by melting of local metasedimentary rocks as suggested by previous workers, but by melting of a more juvenile source at depth. Post-orogenic granites have higher εNd(T) (∼ +4.4) than the syn-orogenic granitoids, indicating their derivation from a deeper crustal level where juvenile crust may predominate.

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.

Age and petrogenesis of the Qassiarsuk carbonatite-alkaline silicate volcanic complex in the Gardar rift, South Greenland

1997 ◽  
Vol 61 (407) ◽  
pp. 499-513 ◽  
Author(s):  
Tom Andersen
Keyword(s):  
Volcanic Rocks ◽  
Single Stage ◽  
Volcanic Complex ◽  
Crustal Material ◽  
Crustal Component ◽  
Depleted Mantle ◽  
Common Parent ◽  
Nd Model Age ◽  
Extrusive Carbonatite ◽  
Age Estimates

AbstractThe Qassiarsuk (formerly spelled Qagssiarssuk) complex is located in a roughly E–W trending graben structure between Qassiarsuk village and Tasiusaq settlement in the northern part of the Precambrian Gardar rift, South Greenland. The complex comprises a sequence of alkaline silicate tuffs and extrusive carbonatites interlayered with sandstones, and their subvolcanic equivalents, which represent possible feeders for the extrusive rocks. The Rb-Sr, Sm-Nd and Pb isotopic characteristics of 65 samples of extrusive carbonatite- and silicate tuffs and carbonatite diatremes have been determined by mass spectrometry. The Qassiarsuk complex can be dated to c. 1.2 Ga by Rb-Sr and Pb-Pb isochrons on whole-rocks and mineral separates, agreeing with previous isotopic ages for the volcanic rocks of the Eriksfjord formation in the Eriksfjord area of the Gardar rift, but not with previous, indirect age estimates of >1.31 Ga for assumed Eriksfjord equivalents in the Motzfeldt area further east. Recalculated isotopic compositions at 1.2 Ga indicate that the Qassiarsuk carbonatite- and alkaline-silicate magmas were comagmatic and derived from a depleted mantle source (εNd>4, εSr<−13, time-integrated, single- stage 238U/204Pb ≤ 7.4). The mantle-derived magmas were contaminated with crustal material, equivalent to the local, pre-Gardar granites and gneisses and sediments derived from these. The crustal component has a depleted mantle Nd model age of 2.1-2.6 Ga; at 1.2 Ga it was characterized by εSr = +76, εNd = −8.4, time-integrated, single- stage 238U/204Pb = 8.2−8.3. Strong decoupling of the Pb from the Sr and Nd isotopic systems suggests that the contamination happened only after carbonatitic and alkaline-silicate magmas had evolved from a common parent, by processes such as liquid immisicibility and/or fractional crystallization. Post-magmatic hydrothermal alteration (oxidation, hydration of mafic silicates, carbonatization of melilite) may have contributed further to the contamination of the carbonatite and alkaline silicate rocks of the Qassiarsuk complex.

scholarly journals Final-Stage Magmatic Record of Paleo-Asian Oceanic Subduction? Insights from Late Permian to Early Triassic Intrusive Rocks in the Yanbian Area, Easternmost Central Asian Orogenic Belt

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 799
Author(s):  
Chao Zhang ◽  
Franz Neubauer ◽  
Zheng-Hong Liu ◽  
Fang-Hua Cui ◽  
Qing-Bin Guan
Keyword(s):  
Partial Melting ◽  
Granitic Rocks ◽  
Early Triassic ◽  
Crustal Material ◽  
Late Permian ◽  
The North ◽  
Wide Range ◽  
Intrusive Rocks ◽  
Subduction Setting ◽  
T Values

This paper reports new zircon LA–ICP–MS U–Pb and Hf isotope data, and whole-rock major and trace element data for Late Permian to Early Triassic intrusive rocks in the Yanbian area, NE China. These data provide new insights into the timing of the final subduction of the Paleo-Asian Ocean beneath the North China Craton. The zircon U–Pb age data indicate that a suite of Late Permian to Early Triassic intrusive rocks related to subduction is present within the Yanbian area. The Late Permian intrusive rocks consist of diorites while the Early Triassic granites and hornblende gabbros constitute a geochemically bimodal igneous rock association. Furthermore, the Early Triassic granites show the geochemical characteristics of shoshonitic rocks. All the rocks are characterized by enrichment in LILEs and LREEs, and depletion in HREEs and HFSEs, suggesting they formed in a subduction setting. Zircons from the Early Triassic gabbros have εHf(t) values and TDM2 ages of +7.6 to +10.7 and 735–1022 Ma, respectively, suggesting that they formed from a primary magma generated by the partial melting of lithospheric mantle material that had been previously modified by subduction-related fluids. The Late Permian diorites have εHf(t) values and TDM2 ages of +0.5 to +9.5 and 853 to 1669 Ma, respectively, while they have high contents of Al2O3, Fe2O3, and low contents of SiO2, Cr, and Ni, indicating Late Permian diorites should derive from the mantle and are influenced by some crustal material. Early Triassic granitic rocks have a wide range of εHf(t) values and TDM2 ages of −4.8 to +9.4 and 852 to 2136 Ma, respectively. Their zircons imply that the Early Triassic granites could be mainly derived from partial melting of the crust, with minor contribution of the crustal material of an ancient crust. The Early Triassic bimodal intrusive rocks in Yanbian area, combined with the regional geologic information; therefore, record a final post-subduction extensional environment due to the break-off of the previously subducted slab.

Geochemical and isotopic (Nd, O, and Pb) constraints on granite sources in the Humber and Dunnage zones, Gaspésie, Quebec, and New Brunswick: implications for tectonics and crustal structure

1994 ◽  
Vol 31 (2) ◽  
pp. 323-340 ◽  
Author(s):  
Joseph B. Whalen ◽  
George A. Jenner ◽  
Ernst Hegner ◽  
Clément Gariépy ◽  
Frederick J. Longstaffe
Keyword(s):  
Subduction Zone ◽  
Incompatible Element ◽  
Crustal Material ◽  
Early Paleozoic ◽  
Isotopic Data ◽  
Geologic History ◽  
Seismic Reflection Data ◽  
Crustal Rocks ◽  
Isotopic Compositions ◽  
Reflection Data

Siluro–Devonian granitoids span a wide compositional range (~50–76% SiO2) and can be subdivided into two groups: (i) monzonitic or incompatible element enriched with affinities to within-plate magmatism (WPG); and (ii) calc-alkalic or incompatible element depleted with supra-subduction zone affinities (VAG). Granitoid εNd(T = 0.4 Ga) values range from −1 to +5.5; most lie between +3 and +5.5. 207Pb/204Pb isotopic compositions range from 15.52 to 15.61; most fall between ~15.55 and 15.59. Most δ18O values lie between +5.5 and +8‰. No well-established trends exist between SiO2 and isotopic composition, and isotopic compositions do not differ between the two trace element defined granitoid groups.Though Pb isotopic data are consistent with a major contribution to the granitoids from Proterozoic-aged Laurentian plate rocks (i.e., Grenville basement), Nd and O isotopic data are not. These isotopic data are consistent with major source components derived from early Paleozoic depleted or supra-subduction zone affected mantle and (or) crustal rocks derived from the early Paleozoic mantle(s). These protoliths would not have seen significant interaction with time-integrated old crustal material or surficial processes. Granitoid Pb isotopic data can be reconciled with an early Paleozoic mantle–crust origin, but it may also be that the Pb isotopes are decoupled from other isotopic systems. In either case, Nd and O isotopic data clearly prohibit the involvement of significant amounts of Grenville crust and suggest that seismic-reflection data do not define crustal blocks, or at least not blocks having a tectonic and geologic history easily related to the surface geology.

The geochronology of the granitic rocks along the Bear–Slave Structural Province boundary, northwest Canadian Shield

1977 ◽  
Vol 14 (6) ◽  
pp. 1356-1373 ◽  
Author(s):  
Rosaline Frith ◽  
R. A. Frith ◽  
R. Doig
Keyword(s):  
Age Groups ◽  
Canadian Shield ◽  
Granitic Rocks ◽  
Thermal Event ◽  
Slave Province ◽  
Fault Block ◽  
Granitic Intrusions ◽  
Main Period ◽  
Archean Crust ◽  
Archean Basement

Archean granitic rocks along the southern Bear–Slave boundary fall into three age groups: the oldest are 3000 Ma old intrusive tonalites and granodiorites that form the basement to the Yellowknife Supergroup; the second are syn-volcanic granitic intrusions of ~ 2700 Ma; and the youngest are ~ 2560 Ma granitic and migmatitic diapirs formed in part from supracrustal and granitic rocks. Two Proterozoic thermal events are recognized within the Slave Province. A ~ 2300 Ma event may be related to early rift breakup of the Archean crust and is recorded in Rb–Sr whole-rock and K–Ar mineral systems. A ~ 1970 Ma event was less intense but may be related to further rifting of the Archean and to fault-block depression of the Indin Lake supracrustal basin, the intrusion of a group of granodioritic stocks, and the formation or granitic pegmatite.Within the Bear Province, evidence of a ~ 2700 Ma intrusive event and a ~ 2300 Ma thermal event are preserved in Rb–Sr whole rock systems. Practically all the granitic rocks of the Bear Province, including the Hepburn batholitic rocks, are thought to have been derived wholly or partly from Archean rocks. The main period of Hudsonian deformation and metamorphism was accompanied by a diapiric remobilization of the Archean basement about 1800 Ma ago. Twelve Rb–Sr isochrons, as well as other published geochronologic data from the region, support these conclusions.

Formation of Canadian 1.9 Ga old continental crust. I: Nd isotopic data

1987 ◽  
Vol 24 (3) ◽  
pp. 396-406 ◽  
Author(s):  
C. Chauvel ◽  
N. T. Arndt ◽  
S. Kielinzcuk ◽  
A. Thom
Keyword(s):  
Continental Crust ◽  
Dominant Role ◽  
Sedimentary Rocks ◽  
Hudson Bay ◽  
Crustal Material ◽  
Isotopic Study ◽  
Volcanic Material ◽  
Crustal Rocks ◽  
Lake Zone ◽  
Archean Crust

A Nd isotopic study was carried out on 1.9−1.8 Ga rocks from two parts of the Trans-Hudson Orogen in northern Canada. The first part is the Reindeer Lake Zone in the Churchill Province in Saskatchewan, where a variety of volcanic, granitoid, and sedimentary rocks are preserved in several lithotectonic belts that border a reworked Archean craton to the northwest. The second area comprises the Ottawa and Belcher islands, in Hudson Bay, and the Fox River volcanics, in Manitoba. These form part of the Circum-Superior Belt, a band of basaltic volcanics and sedimentary rocks that overlies the Archean Superior craton.From U–Pb zircon ages, Pb–Pb ages, and Sm–Nd ages, Nd initial isotopic compositions were calculated for all analyzed samples. In the Saskatchewan terrains, we obtained a large range of εNd values, from +5 to −8. The highest values (+4 to +5) come from two volcanic-dominated belts (Flin Flon and Western la Ronge), lower values (~+2) characterize intervening sediment-dominated domains (Eastern La Ronge, Glennie Lake, and Kisseynew), and still lower values (−1 to −4) were found in migmatitic and granitoid belts adjacent to the reworked Archean craton in the northwest. Each lithotectonic belt has its own characteristic, restricted range of εNd values, and, with few exceptions, there is no correlation between εNd and rock type; i.e., in individual belts, volcanics, granites, and sediments have very similar εNd values.In the Circum-Superior Belt, three lava flows from the Ottawa Islands have εNd values ranging from +4.5 to 0, and samples from the Belcher Islands have values ranging from +3.5 to −9.These results are explained by mixing between mantle-derived rocks and variable amounts of Archean continental crustal rocks. Assuming that 1.9 Ga ago the mantle had an εNd value of +5 and Archean crust had an εNd value of −12, we calculate proportions of Archean crustal material in Trans-Hudson rocks ranging from ~2 to 35 %, increasing systematically toward the Archean platform. The mean Archean component is about 8%: this area of Proterozoic continental crust is clearly dominated by material derived directly from the mantle.The similarity between the εNd values of sediments, granites, and volcanics in the Trans-Hudson Orogen suggests that sedimentary processes played a dominant role in transporting Archean detritus from eroding Archean continental areas into basins, where it mixed with mantle-derived volcanic material and melted to form granitoids.

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