•Evaluating the tectonic settings of new crust formation in the Songliao Block by Pb isotopic ratios.•Identify two distinct regimes of new crust formation in the Songliao block.•Provide a potential ...method to explore the regimes of new crust formation.
How new continental crust formed remains a matter of debate. A key to solve this issue is to determine which tectonic setting(s) are involved in new crust formation. Modern mantle-derived magmas that formed in intracontinental extension settings (OIB-like U/Pb = ∼0.28–0.37) and in subduction settings (IAB-like U/Pb = ∼0.1–0.16) have distinct mean U/Pb ratios, furthermore, the mean U/Pb (∼1.8–2.0) of depleted mantle (DM) is mainly between the OIB-like and IAB-like U/Pb ratios. Therefore, the Pb isotopic ratios (e.g., 206Pb/204Pb) of subduction-related mantle-derived magmas develop below the lead isotopic evolution curve of depleted mantle (DM), whereas those ratios of mantle-derived magmas generated in intracontinental extension settings evolve above the DM evolution curve. Here we used published Nd-Pb isotope compositions from 75 I-type granitoid samples to calculate the time of new crust formation (TDM) and 206Pb/204Pb ratios (206Pb/204Pb)t of new crust at t (i.e., time of new crust remelting) in the Songliao Block from East Asia to determine tectonic settings in which new crust formed have changed with time. Our results show that (206Pb/204Pb)t ratios corresponding to TDM of ∼ 1.55–1.2 Ga plot below the DM evolution curve, indicating a subduction setting of new crust formation, whereas, the (206Pb/204Pb)t ratios corresponding to TDM of ∼ 1.05–0.70 Ga plot above the DM evolution curve, indicating an intracontinental extension setting of new crust formation. Hence, here two distinct tectonic settings of new crust formation are recognized in the Songliao Block. In addition, this method is also applied to well determine the tectonic settings of new crust formation in the Jibei area of North China and the Qinling area of Central China during the Paleoproterozoic (ca. 2.2–1.8 Ga). Therefore, our study demonstrates that the calculation of TDM and (206Pb/204Pb)t ratios of new continental crust from the bulk-rock record may constitute a potential approach to better constrain how new continental crust formed and the Precambrian tectonic evolution of continents.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•The Nage peraluminous granitoids in the Yangtze Block were formed at ca. 850 Ma.•The granitic magma had high temperature but low oxygen fugacity.•Fractional crystallization played a role in ...determining the geochemical composition.•Extension along the southern margin of the Yangtze Block occurred at ca. 850 Ma.
Strongly peraluminous granites are characterized by high A/CNK values (>1.1) and are important for understanding the regional tectonic regime. Here, we present integrated studies of zircon U–Pb ages, trace elements and Lu–Hf isotopes, whole-rock major and trace elements, and Nd isotope compositions for the newly discovered Nage granite porphyry in southeastern Guizhou Province. The porphyry has a crystallization age of 852 ± 5 Ma and shows wide ranges in SiO2 (64.5–72.51 wt%) and Al2O3 (13.08–19.34 wt%) contents, with low TiO2 (0.41–0.84 wt%) and P2O5 (<0.15 wt%) contents. All the samples are strongly peraluminous with A/CNK >1.1, and they have similar trace element patterns with depletion in high field strength elements (HFSE, e.g., Nb and Ta) and enrichment in large-ion lithophile elements (LILE, e.g., Rb, Th and U). Initial zircon Hf isotopes of the porphyry vary from εHf(t) = −7.6 to −0.6, whereas whole-rock Nd isotopes are relatively uniform with εNd(t) = −6.0 to −6.7. They record high zircon saturation temperatures (Tzr) (786–842 °C, mostly >810 °C), but low oxygen fugacity (logfO2 = −16 to −25, corresponding to ΔFMQ −3 to ΔFMQ −7) and emplacement pressure of <0.5 GPa. Major and trace elements, 10,000 Ga/Al ratios and Zr + Nb + Ce + Y values, show good correlations with Tzr, indicating that fractional crystallization may have played an important role. Although these granites show low P2O5 contents that decrease with increasing Rb, the high A/CNK (>1.1), K2O/Na2O (0.7–2.6; average 1.4) and CaO/Na2O (0.2–0.8; mostly >0.5) ratios suggest that clay-poor metasedimentary rock were dominant in the source. Combined with the Nd–Hf isotopes, we suggest that the Nage granite porphyry formed by anatexis of an immature arkose and greywacke source, which was a mixture of weathered juvenile igneous materials and minor recycled ancient crustal components. The ca. 850 Ma strongly peraluminous granites, along with coeval extension-related magmatism along the southwestern margin of the Yangtze Block, indicate an extensional environment started as early as ca. 850 Ma.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Understanding the processes responsible for the intra-plate early Paleozoic Wuyi–Yunkai orogeny (>460Ma to 420–415Ma) in the South China Block (SCB) is important for deducing the interactions of this ...block with other continents at that time, as well as the tectonic evolution of East Asia. One salient feature of the orogen is that despite the wide occurrence of syn- to late-orogenic (440Ma to 420–415Ma) granites in the orogen, neither syn- to late-orogenic volcanic rocks nor mafic rocks of any type have been reported. Such mafic rocks could shed clues about any mantle–crust interaction during such a major orogeny, thus help to understand the dynamics of the orogenic event. We present here, for the first time, geochronological, isotopic and geochemical data for a mafic-intermediate volcanic succession in northern Guangdong, near the edge of the metamorphic core of the orogen. The volcanic rocks unconformably overlie strongly deformed Cambro-Ordovician strata, but are in low-angle unconformable contact with overlying post-orogenic mid-Devonian strata. LA-ICP-MS and SHRIMP U–Pb dating of zircons from two andesitic and dacitic samples gives a consistent crystallization age of ca. 435Ma, younger than the 460–445Ma peak metamorphism of the orogeny but synchronous with the widespread late-orogenic (ca. 440–415Ma) granitic intrusions. Nine least crustally-contaminated basaltic samples are characterized by high MgO (12.3–19.2wt.%), Ni (214–715ppm) and Cr (724–1107ppm), but low TiO2 (0.6–0.8wt.%), Al2O3 (10.2–12.8wt.%) and Fe2O3T (total Fe as Fe2O3) (8.7–11.4wt.%) contents. The basalts also exhibit low Nb/La ratios (0.4–0.8) and constant εNd(t) values (−8.0 to −8.4) with variable SiO2 (44.8–51.5wt.%) contents, suggesting a likely sub-continental lithospheric mantle origin. These high-magnesian basalts have chemical compositions similar to their primary magma, which was estimated using geochemical modeling at SiO2≈50wt.%, MgO≈14wt.% and FeOT≈9wt.%. The estimated potential temperature for the melts is >1300°C, much higher than that of a normal sub-continental lithosphere. This implies that the magma was likely generated from partial melting of lithospheric peridotite heated by hot upwelling asthenosphere. The high-magnesian andesites are interpreted as the products of differentiation and AFC processes from the same basaltic magma source, as supported by their negative zircon εHf(t) values (−21.7 to −6.3) and high zircon δ18O values (7.3–9.0‰). Overall, we interpret that this post-kinematic basalts, plus andesites and dacites as differentiates, resulted from a late-orogenic lithospheric delamination which led to an orogenic collapse, melting of the SCLM, and widespread late-orogenic granitic intrusions in the orogen.
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► We report the first mafic Silurian volcanic rocks in the Wuyi–Yunkai orogen. ► The 435Ma volcanic rocks erupted during the orogenic collapse. ► The high Mg basalts were likely derived from sub-continental lithospheric mantle. ► They indicate high potential melting temperature of ~1300°C. ► The results support the orogenic-root delamination model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The circulation of seawater within the oceanic crust promotes cycling of metals and sulfur, as well as development of the subsurface biosphere. Characterization of the full spectrum of sulfide ...geochemistry in the altered oceanic crust is critical for a complete understanding of global cycling of sulfur and metals, while those in off-axis hydrothermal circulation have received less attention. This study applied a combination of in-situ sulfur isotopic and trace metal analyses to study the pyrite geochemical features in altered basalts of the South China Sea basin. This contribution unravels a detailed picture of the cycling of sulfur and metals in the subsurface. Such cycling is likely to be co-controlled by the hydrothermal and microbial activities when oceanic crusts transit from on-axis to off-axis hydrothermal systems.
A total of five groups of pyrites associated with distinct mineral assemblages, morphologies, trace metal enrichment and sulfur isotopic values were observed in altered basalts. Pyrite disseminated (type 1) within the background hydrothermal alteration is characterized by δ34S values close to zero, with relative enrichment of trace metals (> 500 ppm), such as Ni, Co, and Cu. This type of pyrite is most likely to precipitate from upwelling high-temperature hydrothermal fluids when they ascended towards the seafloor. Sulfur was mainly derived from magmatic sulfides. Linear regression analyses of trace metal contents in disseminated pyrite show various strong positive correlations between trace metals reflecting a series of metal mobility processes, including incorporation into pyrite and leaching directly from sulfides or silicate minerals. Additionally, a population of pyrite has δ34S values ranging from +4 to +8 ‰ and low trace element contents, which reveals precipitation conditions where the ascending high-temperature hydrothermal fluids have mixed with significant amounts of seawater-sourced fluids. This group of pyrites is either formed by the replacement of silicates as patchy texture (type 2) or are exclusively associated with epidote‑carbonate veins (type 3). Furthermore, strongly positive δ34S signatures are observed within framboidal pyrite (type 4) (δ34S up to +57 ‰) and within overgrown euhedral pyrite (type 5) (δ34S up to +24 ‰). These unprecedented isotopically-heavy framboidal pyrite in modern oceanic crust presents a well-preserved organic matter framework, which is interpreted as a consequence of microbial sulfate reduction activities based on current observations. The extremely positive values of the sulfur isotopes could be produced by Rayleigh isotopic fractionation when ~77% sulfate (assumed with an initial seawater sulfate δ34S of 21%) is consumed by microorganisms in closed systems, in this case, the cavities in the altered basalt. The microorganisms meanwhile may enhance the sequestration of trace metals into pyrite, possibly through microbial metabolisms or detoxification processes. The positive δ34S values of overgrown euhedral pyrite (type 5) are interpreted to be mainly introduced by the involvement of seawater-derived sulfur or inherited from the framboidal pyrite.
The various isotopic and elemental signatures in these five types of pyrites could be linked to either the hydrothermal or microbial processes occurring within the upper oceanic crust in the South China Sea basin. Both processes are critical to the metal and sulfur cycling in subsurface and should be considered jointly in future studies. Additionally, our results exemplify the potential roles of microorganisms, not only in accumulating trace metals in sulfides in the subsurface but also as a potential biosignature to reveal microbial activities in similar environments in the early Earth.
•The cycling of sulfur and metals within subsurface of the China South Sea basin was investigated.•Five types of pyrite with various morphologies, sulfur isotopic values and trace element enrichment were observed.•Framboidal pyrite features with the heaviest sulfur isotopic values and enrichment of organic matter and trace metals.•The cycling of sulfur and metals is likely to be co-controlled by hydrothermal and microbial processes in the subsurface.•The framboidal pyrite can act as potential useful biosignatures to trace microbial activities on early Earth.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The seismic, drilling and logging data reveal that a large-scale igneous intrusion with a width of 14 Km and a maximum thickness of 170 m intruded within the Paleogene Liushagang Formation in the ...Fushan Depression, Beibuwan Basin, South China Sea (SCS). In this study, we report the geochemistry and Sr-Nd-Pb-Hf isotopic compositions of the igneous rocks, and evaluate the thermal effect induced by this large-scale igneous intrusion on the host rocks. The analyzed igneous samples exhibit strong enrichment in light rare earth elements (LREE) and large-ion lithophile elements (LILE), having characteristics similar to intra-plate oceanic island basalts (OIB). The Sr-Nd-Pb-Hf isotopic data display narrow ranges (e.g. 87Sr/86Sri = 0.7042–0.7044, 143Nd/144Ndi = 0.5128–0.5129, 206Pb/204Pbi = 18.90–18.94, εHf(t) = +7.56∼+9.60). Geochemical and isotopic compositions suggest a mixed mantle source between depleted mid-ocean-ridge-basalt (MORB) mantle (DMM)-like mantle and enriched mantle type II (EMII, possibly the Hainan mantle plume). Vitrinite reflectance values, major mineralogical changes together with a maturity-related biomarker Ts/(Ts + Tm) all reveal significant thermal effect induced by the igneous intrusion. Vitrinite reflectance values of the host rock are up to 2.5% in the intrusion region, whereas lower reflectance values (0.62–0.73%) occur in the unaffected area of the same strata. Moreover, our results suggest that the host rocks above the igneous intrusion are characterised by higher maturity than below, which should be attributed to the different behavior of hydrothermal fluids. These observations suggest that the thermal effect of large-scale thick igneous intrusions is much more intense than that of thin igneous intrusions, and the behavior of hydrothermal fluids induced by magmatic intrusive events should be a critical impact factor during heat transfer process.
•A large-scale Paleogene igneous intrusion intruded in Eocene strata was reported.•The intrusion was generated through mixing between DMM-like mantle and EMII.•Its thermal effect is much more intense than that of thin igneous intrusions.•The host rocks above the intrusion were more strongly affected than those below.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•New 1888 Ma mafic dyke swarm in southwest Yilgarn Craton, Western Australia has been discovered.•The new dyke suite suggests connection with India at ca. 1890 Ma and may be part of the ...Bastar-Cuddapah Large Igneous Province.•The dyke swarm is coeval with global mafic magmatism found on most other Precambrian cratons.
The Archean Yilgarn Craton in Western Australia is intruded by numerous mafic dykes of varying orientations, which are poorly exposed but discernible in aeromagnetic maps. Previous studies have identified two craton-wide dyke swarms, the 2408 Ma Widgiemooltha and the 1210 Ma Marnda Moorn Large Igneous Provinces (LIP), as well as limited occurrences of the 1075 Ma Warakurna LIP in the northern part of the craton. We report here a newly identified NW-trending mafic dyke swarm in southwestern Yilgarn Craton dated at 1888 ± 9 Ma with ID-TIMS U-Pb method on baddeleyite from a single dyke and at 1858 ± 54 Ma, 1881 ± 37 and 1911 ± 42 Ma with in situ SHRIMP U-Pb on baddeleyite from three dykes. Preliminary interpretation of aeromagnetic data indicates that the dykes form a linear swarm several hundred kilometers long, truncated by the Darling Fault in the west. This newly named Boonadgin dyke swarm is synchronous with post-orogenic extension and deposition of granular iron formations in the Earaheedy basin in the Capricorn Orogen and its emplacement may be associated with far field stresses. Emplacement of the dykes may also be related to initial stages of rifting and formation of the intracratonic Barren Basin in the Albany-Fraser Orogen, where the regional extensional setting prevailed for the following 300 million years. Recent studies and new paleomagnetic evidence raise the possibility that the dykes could be part of the coeval 1890 Ma Bastar-Cuddapah LIP in India. Globally, the Boonadgin dyke swarm is synchronous with a major orogenic episode and records of intracratonic mafic magmatism on many other Precambrian cratons.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
The debate on the Mesozoic tectonics of the South China Block (SCB), featuring a broad orogenic belt and a large continental magmatic province, has been rejuvenated in the past years. There are a ...number of competing tectonic models, each predicting different time, space, and compositional evolutional trends for the Mesozoic igneous rocks, including sporadic basalts. In this paper, we report high precision
40Ar/
39Ar ages and geochemical and Sr–Nd isotopic data for basaltic rocks in central–eastern SCB. These results, together with a data compilation, indicate three evolutionary stages for the basalts. Stage 1 (195–160
Ma) basalts occur only in inland SCB. They exhibit low initial
87Sr/
86Sr ratios (0.7038 to 0.7078), high ε
Nd(t) values (−
1.5 to 6.0) and ocean island basalt (OIB)-like geochemical characteristics such as low La/Nb ratios (0.6 to 1.4), implying negligible to minor lithosphere contamination. Stage 2 (160–110
Ma) basalts, mostly from the same inland region with minor occurrence closer to the coast, are characterized by variable initial
87Sr/
86Sr ratios (0.7053 to 0.7102), εNd(t) values (−
6.0 to 5.0) and low La/Nb ratios (0.9 to 1.8), indicating an enhanced asthenosphere–lithosphere interaction. Stage 3 (110 to ≤
80
Ma) basalts can be further divided into two sub-groups based on their geographic and geochemical variations. Basalts in the coastal regions are characterized by low εNd(t) values (−
8.1 to 3.7) and variably high La/Nb ratios (up to 4.8) indicating a strong arc signature. On the other hand, basalts in the inland regions have high ε
Nd(t) values (−
1.9 to 6.8) and low La/Nb ratios (0.6 to 1.2) that are similar to the stage 1 basalts. We interpret these features as results of geodynamics processes related to the break-up, foundering and retreating of an early Mesozoic flat-subducted oceanic slab.
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► Characterizing temporal–spatial distribution of Mesozoic basaltic rocks in South China. ► Secular changes in geochemical features in different parts of the continent. ► Independent evidence supporting the flat-slab subduction model.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
There is increasing evidence indicating that melts derived from subducted oceanic crust and sediments may have played a key role in building continental crust. This mechanism predicts that juvenile ...arc crust should have oxygen isotope characteristics ranging from mantle-like to supracrustal, but consistent mantle-like radiogenic (Nd-Hf) isotopic signatures. Here we present
in-situ
zircon U-Pb dating, Hf-O isotope analyses, and whole rock major-trace element and Nd isotope analyses of a granitoid from NW India.
In-situ
secondary ion mass spectrometry (SIMS) zircon U-Pb dating yields a weighted mean
207
Pb/
206
Pb age of 873±6 Ma for the granitoid. It displays mantle-like zircon
ε
Hf
(
ε
Hf(873 Ma)
=+9.3 to +10.9) and whole-rock Nd (
ε
Nd(873 Ma)
=+3.5) values but supracrustal δ
18
O values, the latter mostly varying between 9‰ and 10‰. The calculated whole-rock δ
18
O value of 11.3‰±0.6‰ matches well with those of hydrothermally-altered pillow lavas and sheeted dykes from ophiolites. The major and trace element composition of the granitoid is similar to petrological experimental melts derived from a mixture of MORB+sediments. Thus, the granitoid most likely represents the product of partial melting of the uppermost oceanic crust (MORB+sediments). We propose that the decoupling between Hf-Nd and O isotopes as observed in this granitoid can be used as a powerful tool for the identification of slab melting contributing to juvenile continental crustal growth. Such isotopic decoupling can also account for high δ
18
O values observed in ancient juvenile continental crust, such as Archean tonalite-trondhjemite-granodiorite suites.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
In this study, Re and Os isotopes were systematically determined in six geological reference materials (RMs; covering a wide range of lithologies) using the Carius tube (CT) digestion technique with ...and without hydrofluoric acid desilicification. Our results show that the HF desilicification increased the Re extraction efficiency (by 9–15%) evidenced from basaltic and andesitic rocks (e.g., BHVO‐2, TDB‐1 and AGV‐2). This implies that a small proportion of Re resides in silicate phases. For mafic–ultramafic rocks (e.g., BCR‐2, WGB‐1 and WPR‐1), Re extraction efficiencies obtained by the CT digestion with and without HF desilicification were similar. This may indicate that Re in these rocks may dominantly reside in some phases (e.g., magnetite and sulfides) that could be completely dissolved in aqua regia solutions without the aid of HF desilicification. Our results also show that the HF desilicification increased Os extraction efficiency (by 13–99%) in some RMs (e.g., BHVO‐2, WGB‐1 and AGV‐2). This observation suggests that a portion of Os‐rich trace phases may occur as inclusions in the silicate phases that act as isolators at ~ 200 mesh sizes. This study demonstrates that the HF desilicification step prior to CT digestion is important for complete extraction of Re and Os in geological samples.
Dans cette étude, les isotopes du Re et de l'Os ont été systématiquement déterminés pour six matériaux géologiques de référence (RMs, couvrant un large éventail de lithologies) en utilisant la technique de digestion avec tube de Carius (CT) avec et sans désilicification avec de l'acide fluorhydrique (HF). Nos résultats montrent à partir de l'étude de roches basaltiques et andésitiques (par exemple, BHVO‐2, TDB‐1 et AGV‐2) que la désilicification avec l'HF augmente l'efficacité d'extraction du Re (de 9‐15 %). Cela implique qu'une petite proportion du Re réside dans les phases silicatées. Pour les roches mafiques‐ultramafiques (par exemple, BCR‐2, WGB‐1 et WPR‐1), les rendements d'extraction obtenus pour le Re par la digestion CT avec et sans désilicification avec de l'HF son similaires. Ceci semble indiquer que le Re dans ces roches peut résider principalement dans certaines phases (par exemple, la magnétite et les sulfures) qui pourraient être complètement dissoutes dans des solutions d'aqua regia sans l'aide de la désilicification avec de l'HF. Nos résultats montrent également que la désilicification avec de l'HF augmente l'efficacité d'extraction de l'Os (de 13‐99 %) dans certains RMs (par exemple, BHVO‐2, WGB ‐1 et AGV‐2). Cette observation suggère qu'une partie des phases traces riches en Os peuvent être présentes sous forme d'inclusions dans les phases silicatées qui agissent comme des isolateurs au maillage à ~ 200. Cette étude démontre que la désilicification avec de l'HF avant la digestion CT est importante pour l'extraction complète du Re et de l'Os dans des échantillons géologiques.
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FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK
Widespread Cenozoic basalts, erupted at ca. 24–0.16 Ma in central Inner Mongolia, eastern China, are significant for understanding the potential links between deep subduction of oceanic slabs and the ...genesis of continental intra-plate magmatism. Here we examine the whole-rock geochemical and isotopic data, as well as olivine compositions, for Cenozoic alkali and tholeiitic basalts from the Abaga, Huitengliang, and Chifeng areas in central Inner Mongolia. The results suggest that fractional crystallization of olivine + clinopyroxene (in the alkali basalts) and olivine (in the tholeiites), played a key role in their magmatic evolution, without significant crustal contamination or post-magmatic alteration. Geochemical and petrogenetic analyses show that pyroxene and garnet were dominant phases in the residual mineral assemblage for both alkali basalts and tholeiites, implying a pyroxenite source for these basalts. We propose that a pyroxenite-dominated source may be the product of reaction between recycled oceanic slab-derived melts and surrounding mantle peridotites. The spatial and geochemical variations of the Cenozoic basalts in central Inner Mongolia, together with recent geophysical and geological observations in eastern China, imply that the origin and evolution of large-scale Cenozoic continental intra-plate magmatism can be related to subduction of the Paleo-Pacific and Paleo-Asian oceanic slabs. Incorporation of recycled oceanic materials from these two subducted slabs thus influenced the mantle source lithologies and deep-Earth geodynamic processes beneath eastern China.
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•A pyroxenite source is inferred for the Abaga, Huitengliang and Chifeng basalts•Recycled altered oceanic crust contributed to the generation of the basalts•Geochemical variation relates to recycled Paleo-Asian and -Pacific oceanic slabs
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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