Major-trace element and Sr-Nd isotope compositions of mafic dykes of the Singhbhum Craton: Insights into evolution of the lithospheric mantle

We report major and trace element concentrations, along with Nd isotope compositions, for Late Mesoproterozoic to Early Neoproterozoic dolerite sills from the Sette-Daban ridge (southern Verkhoyansk, south-east Siberia). Based on their major element composition, all rocks correspond to low-Ti (<3 wt% TiO2) moderately alkaline basalts. The intrusions can be subdivided into two groups based on their trace element compositions. One group includes sills mainly distributed in the southern part of the study area (Yudoma group), with mid-ocean ridge basalt (MORB) trace element patterns enriched in aqueous fluid mobile incompatible (FMI) elements (Sr, Pb, Ba, U). The second group includes sills mostly distributed in the northern part of the study area, enriched in immobile incompatible (II) elements (Th, Nb, light rare earth elements (LREE)) and to a lesser extent, in aqueous fluid mobile elements. The Nd isotope signatures of the dolerites characterize a depleted mantle source, with a small enrichment from recycled continental crust. The geochemical characteristics of these igneous rocks are analogous to low-Ti basalts of large intraplate provinces (e.g., the Karoo and Siberian Traps). We propose that they formed by rifting-induced melting of the heterogeneous metasomatized shallow spinel-bearing mantle zone. We suggest that two different melting sources were involved in the generation of the two geochemically distinct sill groups, including the addition of two different subduction components. The southern sills were formed by melting of depleted lithospheric mantle enriched with FMI elements, corresponding to subduction-induced metasomatic alteration by fluids at shallow depths. The northern dolerites were formed by melting of depleted lithospheric mantle enriched with II elements, associated with the melting of subducted sediments at deeper depths.

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Subduction-related subcontinental lithospheric mantle metasomatism and crustal thickening: origin for superchondritic Nb/Ta in mafic dykes

Journal of the Geological Society ◽

10.1144/jgs2020-120 ◽

2020 ◽

Vol 178 (1) ◽

pp. jgs2020-120

Author(s):

Xiang Cui ◽

Wenbin Zhu ◽

F. Jourdan

Keyword(s):

Trace Element ◽

South China ◽

Lithospheric Mantle ◽

Incompatible Trace Element ◽

Mantle Metasomatism ◽

Crustal Thickening ◽

Subcontinental Lithospheric Mantle ◽

Content Type ◽

Mafic Dykes ◽

Supplementary Material

Superchondritic Nb/Ta is rarely reported in terrestrial reservoirs and is usually attributed to carbonatite metasomatism or accessory rutile in the residue phase. Previously documented high Nb/Ta in rocks derived from subcontinental lithospheric mantle indicated a predominance of carbonatite metasomatism. This study evaluates Nb/Ta in conjunction with other trace elements of Neoproterozoic mafic dykes exposed in the eastern segment of the Jiangnan Orogen, where early subduction existed before the amalgamation of South China. These mafic dykes show mostly superchondritic Nb/Ta ratios from 19.6 to 24.5. Partial melting modelling suggested low-degree melting of rutile-bearing subcontinental lithospheric mantle for these mafic dykes. A literature review of Neoproterozoic mafic–intermediate rocks throughout the Jiangnan Orogen shows sporadically but coincidently superchondritic Nb/Ta near or beneath the Shuangxiwu arc, indicating rutile stability in the relict sub-arc mantle. Rutile in the lherzolite was formed sometime after Neoproterozoic subduction initiation in South China but contemporaneous with crustal thickening at c. 860 Ma. This study brings direct evidence to bear on the mechanism of rutile formation in the mantle wedge, as well as the link between crustal thickening and superchondritic Nb/Ta of mafic products derived from the metasomatized mantle.Supplementary material: Major and trace element compositions, photomicrographs of samples, and figures illustrating geochemistry, REE and incompatible trace element patterns and loss on ignition versus Nb/Ta and La/Yb are available at https://doi.org/10.6084/m9.figshare.c.5093535

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Ore and Geochemical Specialization and Substance Sources of the Ural and Timan Carbonatite Complexes (Russia): Insights from Trace Element, Rb–Sr, and Sm–Nd Isotope Data

Minerals ◽

10.3390/min11070711 ◽

2021 ◽

Vol 11 (7) ◽

pp. 711

Author(s):

Irina Nedosekova ◽

Nikolay Vladykin ◽

Oksana Udoratina ◽

Boris Belyatsky

Keyword(s):

Trace Element ◽

Mantle Source ◽

Crustal Evolution ◽

Trace Element Data ◽

The Urals ◽

Nd Isotope ◽

Enriched Mantle ◽

Depleted Mantle ◽

Mantle Sources ◽

Geochemical Specialization

The Ilmeno–Vishnevogorsk (IVC), Buldym, and Chetlassky carbonatite complexes are localized in the folded regions of the Urals and Timan. These complexes differ in geochemical signatures and ore specialization: Nb-deposits of pyrochlore carbonatites are associated with the IVC, while Nb–REE-deposits with the Buldym complex and REE-deposits of bastnäsite carbonatites with the Chetlassky complex. A comparative study of these carbonatite complexes has been conducted in order to establish the reasons for their ore specialization and their sources. The IVC is characterized by low 87Sr/86Sri (0.70336–0.70399) and εNd (+2 to +6), suggesting a single moderately depleted mantle source for rocks and pyrochlore mineralization. The Buldym complex has a higher 87Sr/86Sri (0.70440–0.70513) with negative εNd (−0.2 to −3), which corresponds to enriched mantle source EMI-type. The REE carbonatites of the Chetlassky сomplex show low 87Sr/86Sri (0.70336–0.70369) and a high εNd (+5–+6), which is close to the DM mantle source with ~5% marine sedimentary component. Based on Sr–Nd isotope signatures, major, and trace element data, we assume that the different ore specialization of Urals and Timan carbonatites may be caused not only by crustal evolution of alkaline-carbonatite magmas, but also by the heterogeneity of their mantle sources associated with different degrees of enrichment in recycled components.

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TRACE ELEMENT AND Sr-Nd ISOTOPE GEOCHEMISTRY OF FLUORITE FROM THE XIANGSHAN URANIUM DEPOSIT, SOUTHEAST CHINA

Economic Geology ◽

10.2113/gsecongeo.101.8.1613 ◽

2006 ◽

Vol 101 (8) ◽

pp. 1613-1622 ◽

Cited By ~ 25

Author(s):

Y.-h. Jiang ◽

H.-f. Ling ◽

S.-y. Jiang ◽

W.-z. Shen ◽

H.-h. Fan ◽

...

Keyword(s):

Trace Element ◽

Uranium Deposit ◽

Isotope Geochemistry ◽

Nd Isotope ◽

Southeast China

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Trace-element and Nd-isotope systematics in detrital apatite of the Po river catchment: Implications for provenance discrimination and the lag-time approach to detrital thermochronology

Lithos ◽

10.1016/j.lithos.2017.08.006 ◽

2017 ◽

Vol 290-291 ◽

pp. 48-59 ◽

Cited By ~ 14

Author(s):

Marco G. Malusà ◽

Jiangang Wang ◽

Eduardo Garzanti ◽

Zhi-Chao Liu ◽

Igor M. Villa ◽

...

Keyword(s):

Trace Element ◽

Lag Time ◽

Po River ◽

Nd Isotope ◽

River Catchment ◽

Isotope Systematics

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Evolution and composition of the lithospheric mantle underneath the western Arabian peninsula: constraints from Sr?Nd isotope systematics of mantle xenoliths

Contributions to Mineralogy and Petrology ◽

10.1007/bf00286833 ◽

1990 ◽

Vol 105 (4) ◽

pp. 460-472 ◽

Cited By ~ 76

Author(s):

Friedhelm Henjes-Kunst ◽

Rainer Altherr ◽

Albrecht Baumann

Keyword(s):

Lithospheric Mantle ◽

Arabian Peninsula ◽

Mantle Xenoliths ◽

Nd Isotope ◽

Isotope Systematics

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Late Eocene post-collisional magmatic rocks from the southern Qiangtang terrane record the melting of pre-collisional enriched lithospheric mantle

Geological Society of America Bulletin ◽

10.1130/b35864.1 ◽

2021 ◽

Author(s):

Yue Qi ◽

Qiang Wang ◽

Gang-jian Wei ◽

Xiu-Zheng Zhang ◽

Wei Dan ◽

...

Keyword(s):

Tibetan Plateau ◽

Trace Element ◽

Partial Melting ◽

Early Cretaceous ◽

Lithospheric Mantle ◽

Late Eocene ◽

The Tibetan Plateau ◽

Mafic Rocks ◽

Isotopic Compositions ◽

Qiangtang Terrane

Diverse rock types and contrasting geochemical compositions of post-collisional mafic rocks across the Tibetan Plateau indicate that the underlying enriched lithospheric mantle is heterogeneous; however, how these enriched mantle sources were formed is still debated. The accreted terranes within the Tibetan Plateau experienced multiple stages of evolution. To track the geochemical characteristics of their associated lithospheric mantle through time, we can use mantle-derived magmas to constrain the mechanism of mantle enrichment. We report zircon U-Pb ages, major and trace element contents, and Sr-Nd isotopic compositions for Early Cretaceous and late Eocene mafic rocks in the southern Qiangtang terrane. The Early Cretaceous Baishagang basalts (107.3 Ma) are characterized by low K2O/Na2O (<1.0) ratios, arc-like trace element patterns, and uniform Sr-Nd isotopic compositions [(87Sr/86Sr)i = 0.7067−0.7073, εNd(t) = −0.4 to −0.2]. We suggest that the Baishagang basalts were derived from partial melting of enriched lithospheric mantle that was metasomatized by subducted Bangong−Nujiang oceanic material. We establish the geochemistry of the pre-collisional enriched lithospheric mantle under the southern Qiangtang terrane by combining our data with those from other Early Cretaceous mafic rocks in the region. The late Eocene (ca. 35 Ma) post-collisional rocks in the southern Qiangtang terrane have low K2O/Na2O (<1.0) ratios, and their major element, trace element, and Sr-Nd isotopic compositions [(87Sr/86Sr)i = 0.7042−0.7072, εNd(t) = −4.5 to +1.5] are similar to those of the Early Cretaceous mafic rocks. Based on the distribution, melting depths, and whole-rock geochemical compositions of the Early Cretaceous and late Eocene mafic rocks, we argue that the primitive late Eocene post-collisional rocks were derived from pre-collisional enriched lithospheric mantle, and the evolved samples were produced by assimilation and fractional crystallization of primary basaltic magma. Asthenosphere upwelling in response to the removal of lithospheric mantle induced the partial melting of enriched lithospheric mantle at ca. 35 Ma.

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Miocene Olivine Leucitites in the Hoh Xil Basin, Northern Tibet: Implications for Intracontinental Lithosphere Melting and Surface Uplift of the Tibetan Plateau

Journal of Petrology ◽

10.1093/petrology/egaa026 ◽

2020 ◽

Vol 61 (1) ◽

Author(s):

Yue Qi ◽

Qiang Wang ◽

Ying-Tang Zhu ◽

Lian-Chang Shi ◽

Ya-Nan Yang

Keyword(s):

Tibetan Plateau ◽

Lithospheric Mantle ◽

The Tibetan Plateau ◽

Nd Isotope ◽

Northern Tibet ◽

Surface Uplift ◽

Enriched Mantle ◽

Magmatic Rocks ◽

Low Degree ◽

Pliocene Magmatism

Abstract The generation of Miocene–Pliocene post-collisional magmatic rocks in northern Tibet was coeval with surface uplift, meaning that understanding the petrogenesis of these rocks should provide clues to the mechanism of uplift of the Tibetan Plateau. However, the nature of the source(s) of Miocene–Pliocene post-collisional rocks is unresolved, especially for potassic–ultrapotassic rocks. This study focuses on 16 Ma olivine leucitites in the Hoh Xil Basin of northern Tibet, which display the lowest SiO2 (43·4–48·8 wt%) contents of all Miocene–Pliocene magmatic rocks in northern Tibet and have high MgO (4·85–8·57 wt%) contents and high K2O/Na2O (>1) ratios. Whole-rock geochemical compositions suggest that the olivine leucitites did not undergo significant fractional crystallization or crustal assimilation. All samples are enriched in large ion lithophile elements relative to high field strength elements, and they exhibit uniform whole-rock Sr–Nd isotope [(87Sr/86Sr)i = 0·7071–0·7077 and εNd(t) = −3·1 to −3·9] and olivine O isotope (5·8–6·6 ‰, mean of 6·2 ± 0·2 ‰, n = 21) compositions. We propose that the olivine leucitites were derived by low-degree partial melting of phlogopite-lherzolite in garnet-facies lithospheric mantle. Given the tectonic evolution of the Hoh Xil Basin and adjacent areas, we suggest that southward subduction of Asian (Qaidam block) lithosphere after India–Asia collision transferred potassium and other incompatible elements into the lithospheric mantle, forming the K-enriched mantle source of the Miocene–Pliocene potassic–ultrapotassic rocks. Removal of lower lithospheric mantle subsequently induced voluminous Miocene–Pliocene magmatism and generated >1 km surface uplift in the Hoh Xil Basin.

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