scholarly journals Sr-Nd-Pb-Ca Isotopes of Holocene Basalts from Jingpohu, NE China: Implications for the Origin of Their Enriched Mantle Signatures

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 790
Author(s):  
Feixiang Wei ◽  
Bo Pan ◽  
Jiandong Xu
Keyword(s):  
Volcanic Field ◽  
Magma Chambers ◽  
Ne China ◽  
Isotopic Signatures ◽  
Enriched Mantle ◽  
Depleted Mantle ◽  
Mantle Sources ◽  
Heavy Rare Earth Elements ◽  
Oceanic Island Basalts ◽  
Back Arc

The geochemistry on Holocene lavas from the Jingpohu volcanic field in NE China are compared with other Cenozoic lavas from across the back-arc rift of NE China, in order to constrain their enriched mantle sources. Holocene lavas within Jingpohu volcanic field comprise two separate “Crater Forest” (CF) and “Frog Pool” (FP) volcanic areas. FP lavas have lower MgO, CaO, and heavy rare earth elements and higher Al2O3, Na2O, K2O, and large-ion lithophile elements than CF lavas. Yet, both CF and FP lavas share similar isotopic signatures, with depleted Sr and Nd isotopes (87Sr/86Sr = 0.703915–0.704556, 143Nd/144Nd = 0.512656–0.512849) and unradiogenic Pb isotopes (208Pb/204Pb = 37.79–38.06, 207Pb/204Pb = 15.45–15.54, 206Pb/204Pb = 17.49–18.15), similar to oceanic island basalts. An important new constraint for the Jingpohu lavas lies in their Ca isotopes of δ44/40Ca from 0.63 to 0.77‰, which are lower than that of the bulk silicate earth (0.94 ± 0.05‰). By comparing the isotopic signatures of sodic lavas with that of the potassic lavas across NE China, we propose a three-component mixing model as the source for the sodic lavas. In consistence with geophysical results, we propose that subducting Pacific plate induces asthenospheric mantle upwelling of an upper depleted mantle (DM), including subducted ancient sediments (EM I), which partially melted upon ascent. These primary melts further interacted with the lithospheric mantle (EM II), before differentiating within crustal magma chambers and erupting.

scholarly journals Geochemical Variation of Miocene Basalts within Shikoku Basin: Magma Source Compositions and Geodynamic Implications

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 25
Author(s):  
Shuang-Shuang Chen ◽  
Tong Hou ◽  
Jia-Qi Liu ◽  
Zhao-Chong Zhang
Keyword(s):  
Japan Sea ◽  
Isotopic Signature ◽  
Magma Source ◽  
Isotopic Compositions ◽  
Enriched Mantle ◽  
Shikoku Basin ◽  
Depleted Mantle ◽  
Parece Vela Basin ◽  
Back Arc ◽  
Ocean Ridge

Shikoku Basin is unique as being located within a trench-ridge-trench triple junction. Here, we report mineral compositions, major, trace-element, and Sr-Nd-Pb isotopic compositions of bulk-rocks from Sites C0012 (>18.9 Ma) and 1173 (13–15 Ma) of the Shikoku Basin. Samples from Sites C0012 and 1173 are tholeiitic in composition and display relative depletion in light rare earth elements (REEs) and enrichment in heavy REEs, generally similar to normal mid-ocean ridge basalts (N-MORB). Specifically, Site C0012 samples display more pronounced positive anomalies in Rb, Ba, K, Pb and Sr, and negative anomalies in Th, U, Nb, and Ta, as well as negative Nb relative to La and Th. Site 1173 basalts have relatively uniform Sr-Nd-Pb isotopic compositions, close to the end member of depleted mantle, while Site C0012 samples show slightly enriched Sr-Nd-Pb isotopic signature, indicating a possible involvement of enriched mantle 1 (EM1) and EM2 sources, which could be attributed to the metasomatism of the fluids released from the dehydrated subduction slab, but with the little involvement of subducted slab-derived sedimentary component. Additionally, the Shikoku Basin record the formation of the back-arc basin was a mantle conversion process from an island arc to a typical MORB. The formation of the Shikoku Basin is different from that of the adjacent Japan Sea and Parece Vela Basin, mainly in terms of the metasomatized subduction-related components, the nature of mantle source, and partial melting processes.

Le terrane de Slide Mountain (Cordillères canadiennes) : une lithosphère océanique marquée par des points chauds

2003 ◽  
Vol 40 (6) ◽  
pp. 833-852 ◽  
Author(s):  
M Tardy ◽  
H Lapierre ◽  
D Bosch ◽  
A Cadoux ◽  
A Narros ◽  
...  
Keyword(s):  
Volcanic Rocks ◽  
Oceanic Island ◽  
Light Rare Earth ◽  
Isotopic Compositions ◽  
Incompatible Elements ◽  
Depleted Mantle ◽  
Mantle Sources ◽  
British Colombia ◽  
Ultramafic Cumulates ◽  
Back Arc

The Slide Mountain Terrane consists of Devonian to Permian siliceous and detrital sediments in which are interbedded basalts and dolerites. Locally, ultramafic cumulates intrude these sediments. The Slide Mountain Terrane is considered to represent a back-arc basin related to the Quesnellia Paleozoic arc-terrane. However, the Slide Mountain mafic volcanic rocks exposed in central British Colombia do not exhibit features of back-arc basin basalts (BABB) but those of mid-oceanic ridge (MORB) and oceanic island (OIB) basalts. The N-MORB-type volcanic rocks are characterized by light rare-earth element (LREE)-depleted patterns, La/Nb ratios ranging between 1 and 2. Moreover, their Nd and Pb isotopic compositions suggest that they derived from a depleted mantle source. The within-plate basalts differ from those of MORB affinity by LREE-enriched patterns; higher TiO2, Nb, Ta, and Th abundances; lower εNd values; and correlatively higher isotopic Pb ratios. The Nd and Pb isotopic compositions of the ultramafic cumulates are similar to those of MORB-type volcanic rocks. The correlations between εNd and incompatible elements suggest that part of the Slide Mountain volcanic rocks derive from the mixing of two mantle sources: a depleted N-MORB type and an enriched OIB type. This indicates that some volcanic rocks of the Slide Mountain basin likely developed from a ridge-centered or near-ridge hotspot. The activity of this hotspot is probably related to the worldwide important mantle plume activity that occurred at the end of Permian times, notably in Siberia.

scholarly journals 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 ◽  
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.

scholarly journals Adakites, High-Nb Basalts and Copper–Gold Deposits in Magmatic Arcs and Collisional Orogens: An Overview

Geosciences ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 29
Author(s):  
Pavel Kepezhinskas ◽  
Nikolai Berdnikov ◽  
Nikita Kepezhinskas ◽  
Natalia Konovalova
Keyword(s):  
Subduction Zones ◽  
Far East ◽  
Gold Deposits ◽  
Type I ◽  
Isotopic Signatures ◽  
Epithermal Mineralization ◽  
Depleted Mantle ◽  
Mantle Sources ◽  
East Russia ◽  
Collisional Orogens

Adakites are Y- and Yb-depleted, SiO2- and Sr-enriched rocks with elevated Sr/Y and La/Yb ratios originally thought to represent partial melts of subducted metabasalt, based on their association with the subduction of young (<25 Ma) and hot oceanic crust. Later, adakites were found in arc segments associated with oblique, slow and flat subduction, arc–transform intersections, collision zones and post-collisional extensional environments. New models of adakite petrogenesis include the melting of thickened and delaminated mafic lower crust, basalt underplating of the continental crust and high-pressure fractionation (amphibole ± garnet) of mantle-derived, hydrous mafic melts. In some cases, adakites are associated with Nb-enriched (10 ppm < Nb < 20 ppm) and high-Nb (Nb > 20 ppm) arc basalts in ancient and modern subduction zones (HNBs). Two types of HNBs are recognized on the basis of their geochemistry. Type I HNBs (Kamchatka, Honduras) share N-MORB-like isotopic and OIB-like trace element characteristics and most probably originate from adakite-contaminated mantle sources. Type II HNBs (Sulu arc, Jamaica) display high-field strength element enrichments in respect to island-arc basalts coupled with enriched, OIB-like isotopic signatures, suggesting derivation from asthenospheric mantle sources in arcs. Adakites and, to a lesser extent, HNBs are associated with Cu–Au porphyry and epithermal deposits in Cenozoic magmatic arcs (Kamchatka, Phlippines, Indonesia, Andean margin) and Paleozoic-Mesozoic (Central Asian and Tethyan) collisional orogens. This association is believed to be not just temporal and structural but also genetic due to the hydrous (common presence of amphibole and biotite), highly oxidized (>ΔFMQ > +2) and S-rich (anhydrite in modern Pinatubo and El Chichon adakite eruptions) nature of adakite magmas. Cretaceous adakites from the Stanovoy Suture Zone in Far East Russia contain Cu–Ag–Au and Cu–Zn–Mo–Ag alloys, native Au and Pt, cupriferous Ag in association witn barite and Ag-chloride. Stanovoy adakites also have systematically higher Au contents in comparison with volcanic arc magmas, suggesting that ore-forming hydrothermal fluids responsible for Cu–Au(Mo–Ag) porphyry and epithermal mineralization in upper crustal environments could have been exsolved from metal-saturated, H2O–S–Cl-rich adakite magmas. The interaction between depleted mantle peridotites and metal-rich adakites appears to be capable of producing (under a certain set of conditions) fertile sources for HNB melts connected with some epithermal Au (Porgera) and porphyry Cu–Au–Mo (Tibet, Iran) mineralized systems in modern and ancient subduction zones.

scholarly journals Geochemistry and petrology of mafic Proterozoic and Permian dykes on Bornholm, Denmark: Four Episodes of magmatism on the margin of the Baltic Shield

2010 ◽  
Vol 58 ◽  
pp. 35-65
Author(s):  
Paul Martin Holm ◽  
L.E. Pedersen, ◽  
B Højsteen
Keyword(s):  
Mantle Plume ◽  
Mantle Source ◽  
Small Degree ◽  
Spinel Peridotite ◽  
Alkali Basalts ◽  
Enriched Mantle ◽  
Depleted Mantle ◽  
Proterozoic Basement ◽  
The Baltic ◽  
Back Arc

More than 250 dykes cut the mid Proterozoic basement gneisses and granites of Bornholm. Most trend between NNW and NNE, whereas a few trend NE and NW. Field, geochemical and petrological evidence suggest that the dyke intrusions occurred as four distinct events at around 1326 Ma (Kelseaa dyke), 1220 Ma (narrow dykes), 950 Ma (Kaas and Listed dykes), and 300 Ma (NW-trending dykes), respectively. The largest dyke at Kelseaa (60 m wide) and some related dykes are primitive olivine tholeiites, one of which has N-type MORB geochemical features; all are crustally contaminated. The Kelseaa type magmas were derived at shallow depth from a fluid-enriched, relatively depleted, mantle source,but some have a component derived from mantle with residual garnet. They are suggested to have formed in a back-arc environment. The more than 200 narrow dykes are olivine tholeiites (some picritic), alkali basalts, trachybasalts, basanites and a few phonotephrites. The magmas evolved by olivine and olivine + clinopyroxene fractionation. They have trace element characteristics which can be described mainly by mixing of two components: one is a typical OIB-magma (La/Nb < 1, Zr/Nb = 4, Sr/Nd = 16) and rather shallowly derived from spinel peridotite; the other is enriched in Sr and has La/Nb = 1.0 - 1.5, Zr/Nb = 9, Sr/Nd = 30 and was derived at greater depth, probably from a pyroxenitic source. Both sources were probably recycled material in a mantle plume. A few of these dykes are much more enriched in incompatible elements and were derived from garnet peridotite by a small degree of partial melting. The Kaas and Listed dykes (20-40 m) and related dykes are evolved trachybasalts to basaltic trachyandesites. They are most likely related to the Blekinge Dalarne Dolerite Group. The few NW-trending dykes are quartz tholeiites, which were generated by large degrees of rather shallow melting of an enriched mantle source more enriched than the source of the older Bornholm dykes. The source of the NW-trending dykes was probably a very hot mantle plume.

The Early Proterozoic carbonatite complex of Angico dos Dias, Bahia State, Brazil: geochemical and Sr-Nd isotopic evidence for an enriched mantle origin

2003 ◽  
Vol 67 (5) ◽  
pp. 1039-1057 ◽  
Author(s):  
P. Antonini ◽  
P. Comin-chiaramonti ◽  
C. B. Gomes ◽  
P. Censi ◽  
B. F. Riffel ◽  
...  
Keyword(s):  
Large Scale ◽  
Alkaline Complex ◽  
Carbonatite Complex ◽  
Early Proterozoic ◽  
Isotopic Signatures ◽  
Enriched Mantle ◽  
Mantle Sources ◽  
Northern Side ◽  
Very High ◽  
Potassic Magmatism

AbstractBorehole samples of carbonatites and phlogopite-pyroxenites from the Angico dos Dias (AdD) intrusive alkaline complex, State of Bahia, Brazil, have been investigated in terms of mineralogy, geochemistry and C-O-Sr-Nd isotopes. The AdD complex, of Early Proterozoic age (2 Ga), intrudes the northern side of the São Francisco Craton. Mineralogy and petrography indicate that the studied rocks only partially preserved their magmatic textural features owing to their metamorphic re-equilibration (greenschist facies). The REE contents and LREE/HREE ratios of the AdD carbonatites are very high (mean 3979±718 ppm and La/Yb = 215±23, respectively), as for most Precambrian magmatic carbonatites. The AdD carbonatites are also enriched in 18O (δ18O = 11.9 to 15.8‰), possibly due to secondary processes (e.g. metamorphism, alteration) whereas carbon isotopes are in the range of ‘primary carbonatites’ (δ13C = –5.7 to –7.1‰). Most of the initial 87Sr/86Sr and 143Nd/144Nd values of the studied carbonatites were not appreciably modified by secondary processes. Their εtSr and εtNd values (20.0 to 25 and 0.7 to –4.5, respectively) indicate enriched mantle sources very different from the ‘depleted’ ones related to many Precambrian carbonatites from North America (0.6 –2.6 Ga) and Africa (0.5 –2.0 Ga). The Early Proterozoic Sr-Nd isotopic signatures of the AdD carbonatites are similar to those of the Early Cretaceous carbonatites from the Paraná basin. The latter carbonatites show a great isotopic variability ranging from Bulk Earth to the related potassic magmatism from Asunción-Sapucai graben in the Eastern Paraguay (K-ASU magmatism: εtSr = 35 to 50 and εtNd = –12 to –20). The very similar isotopic compositions of Precambrian and post-Palaeozoic carbonatites worldwide indicate that the subcontinental mantle variability lasted for long periods of time and indicate a large-scale mantle heterogeneity.

Geochemical aspects of back-arc spreading in the Scotia Sea and western Pacific

1981 ◽  
Vol 300 (1454) ◽  
pp. 263-285 ◽  
Keyword(s):  
Island Arc ◽  
Calc Alkaline ◽  
Volcanic Arc ◽  
Scotia Sea ◽  
Marginal Basin ◽  
Early Stages ◽  
Enriched Mantle ◽  
Mantle Sources ◽  
History Of ◽  
Back Arc

The results of recent geochemical investigations of several island arc - marginal basin systems in the Scotia Sea area and in the western Pacific are outlined. Marginal basins in different stages of evolution are represented, from those in the initial stages of formation to those with an extensive and multiple history of back-arc spreading. Some are completely intraoceanic, others have developed at continental margins. Basalts erupted at back-arc spreading centres seem to be as geochemically varied as those from normal mid-ocean ridges, and record evidence for similar processes of partial melting, fractional crystallization and magma mixing in their genesis. They appear to have been derived from mantle sources with incompatible trace element characteristics ranging from ‘depleted’ to ‘enriched’, but with the ‘enriched’ mantle sources being sampled during the earlier stages of back-arc spreading. Submarine back-arc basalts are more vesicular than their normal ocean ridge equivalents, and their corresponding glasses have higher water contents. This, together with other geochemical features such as the higher ratios of lithophile to high field strength elements in some back-arc basalts, suggests that a component from the subducted slab may be involved in their petrogenesis. The chemistry of the corresponding arc volcanics is described in relation to the subduction and extensions history of marginal basin development. In intraoceanic arcs the early stages of arc magmatism are dominated by the eruption of large volumes of island arc tholeiites and subsidiary high-Mg andesites. In the Mariana region, after the initial volcanic arc is split and separated by back-arc spreading, the later frontal arc volcanics have calc-alkaline characteristics. Basalts erupted during the early stages of back-arc spreading more commonly have arc-like geochemical features when the marginal basin has developed through splitting of a calc-alkaline volcanic arc. The secular variation in the geochemistry of the arc volcanics may be related to the progressive development of a lithophile element enriched mantle source beneath the arc. This source contributes to the basalts produced during the early stages of arc rifting and back-arc spreading. Ophiolite complexes which represent marginal basin floor may well carry these arc-like geochemical features.

Sub-lithospheric mantle sources for overlapping southern African Large Igneous Provinces

2021 ◽  
Author(s):  
L.D. Ashwal
Keyword(s):  
Lithospheric Mantle ◽  
Isotopic Data ◽  
Isotopic Signatures ◽  
Large Igneous Provinces ◽  
Igneous Provinces ◽  
Depleted Mantle ◽  
Heating Event ◽  
Mantle Sources ◽  
Short Time ◽  
Melt Composition

Abstract At least four spatially overlapping Large Igneous Provinces, each of which generated ∼1 x 106 km3 or more of basaltic magmas over short time intervals (&lt;5 m.y.), were emplaced onto and into the Kaapvaal Craton between 2.7 and 0.18 Ga: Ventersdorp (2 720 Ma, ∼0.7 x 106 km3), Bushveld (2 056 Ma, ∼1.5 x 106 km3), Umkondo (1 105 Ma, ∼2 x 106 km3) and Karoo (182 Ma, ∼3 x 106 km3). Each of these has been suggested to have been derived from melting of sub-continental lithospheric mantle (SCLM) sources, but this is precluded because: (1) each widespread heating event sufficient to generate 1 to 2 x 106 km3 of basalt from the Kaapvaal SCLM (volume = 122 to 152 x 106 km3) would increase residual Mg# by 0.5 to 2 units, depending on degree of melting, and source and melt composition, causing significant depletion in already-depleted mantle, (2) repeated refertilization of the Kaapvaal SCLM would necessarily increase its bulk density, compromising its long-term buoyancy and stability, and (3) raising SCLM temperatures to the peridotite solidus would also have repeatedly destroyed lithospheric diamonds by heating and oxidation, which clearly did not happen. It is far more likely, therefore, that the Kaapvaal LIPs were generated from sub-lithospheric sources, and that their diverse geochemical and isotopic signatures represent variable assimilation of continental crustal components. Combined Sr and Nd isotopic data (n = 641) for the vast volumetric majority of Karoo low-Ti tholeiitic magmatic products can be successfully modelled as an AFC mixing array between a plume-derived parental basalt, with &lt;10% of a granitic component derived from 1.1 Ga Namaqua-Natal crust. Archaean crustal materials are far too evolved (εNd ∼ -35) to represent viable contaminants. However, a very minor volume of geographically-restricted (and over-analysed) Karoo magmas, including picrites, nephelinites, meimechites and other unusual rocks may represent low-degree melting products of small, ancient, enriched domains in the Kaapvaal SCLM, generated locally during the ascent of large-volume, plume-derived melts. The SCLM-derived rocks comprise the well-known high-Ti (&gt;2 to 3 wt.% TiO2) magma group, have εNd, 182 values between +10.5 and -20.9, and are characteristically enriched in Sr (up to 1 500 ppm), suggesting a possible connection to kimberlite, lamproite and carbonatite magmatism. These arguments may apply to continental LIPs in general, although at present, there are insufficient combined Sr + Nd isotopic data with which to robustly assess the genesis of other southern African LIPs, including Ventersdorp (n = 0), Bushveld (n = 55) and Umkondo (n = 18).

scholarly journals Volcanogenic CO2 Degassing in the Songliao Continental Rift System, NE China

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-14
Author(s):  
Wenbin Zhao ◽  
Zhengfu Guo ◽  
Ming Lei ◽  
Maoliang Zhang ◽  
Lin Ma ◽  
...  
Keyword(s):  
Volcanic Field ◽  
Continental Rift ◽  
Rift System ◽  
Chemical Compositions ◽  
Ne China ◽  
Depleted Mantle ◽  
Cold Spring ◽  
Organic Sediments ◽  
Co2 Degassing ◽  
Isotope Analyses

The Wudalianchi monogenetic volcanic field (WMVF) is located in the Songliao basin within a major continental rift system in NE China. Bubbling springs and diffuse degassing from soils are typical features of the WMVF. Chemical compositions and C-He isotope analyses revealed that the cold spring gases might originate from the enriched upper mantle (EM), which resulted from the mixing between slab materials (subducted organic sediments and carbonates) in the mantle transition zone (MTZ) and the ambient depleted mantle. These EM-derived volatiles experienced variable degrees of crustal input, including both continental organic metasediments and crustal carbonates during their ascending path to the surface. The estimated results of the degassing CO2 fluxes, combined with previous geophysical evidence, suggest that the CO2 degassing activities become weaker from early to late in Quaternary.

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