306 results on '"Weidong Sun"'
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2. Unradiogenic Pb isotopic compositions of late Archean lower continental crust
- Author
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Weidong Sun and William F. McDonough
- Subjects
Geology ,QE1-996.5 - Published
- 2023
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3. The evolution of the Magma Ocean and the formation of the habitable Earth
- Author
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Weidong Sun and Xiuqi Shang
- Subjects
Geology ,QE1-996.5 - Published
- 2022
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4. Fragments of archean cratonic lithosphere mantle at large
- Author
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Weidong Sun and Fanfan Tian
- Subjects
Geology ,QE1-996.5 - Published
- 2022
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5. How will volcanic ash from the Tonga volcano eruption perturbate marine carbon cycle?
- Author
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Xiaole Sun and Weidong Sun
- Subjects
Geology ,QE1-996.5 - Published
- 2022
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6. Enhanced cooling of the mantle by the onset of modern plate tectonics
- Author
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Weidong Sun
- Subjects
Geology ,QE1-996.5 - Published
- 2022
- Full Text
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7. Water in coesite: Incorporation mechanism and operation condition, solubility and P-T dependence, and contribution to water transport and coesite preservation
- Author
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Wei Yan, Yanyao Zhang, Yunlu Ma, Mingyue He, Lifei Zhang, Weidong Sun, Christina Yan Wang, and Xi Liu
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Coesite preservation ,FTIR ,New IR experimental Protocol ,Anhydrous minerals ,P-T dependence of water solubility ,Water-incorporation mechanism ,Geology ,QE1-996.5 - Abstract
A series of coesite, coexisting with or without a liquid phase, was synthesized in the nominal system SiO2–H2O at 800–1450 °C and 5 GPa. Micro-Raman spectroscopy was used to identify the crystalline phase, electron microprobe and LA-ICP-MS were employed to quantify some major and trace elements, and unpolarized FTIR spectroscopy was applied to probe the different types of hydrogen defects, explore water-incorporation mechanisms and quantify water contents. Trace amounts of Al and B were detected in the coesite. Combining our results with the results in the literatures, we have found no positive correlation between the Al contents and the “Al”-based hydrogen concentrations, suggesting that previously proposed hydrogen-incorporation mechanism H+ + Al3+ ↔ Si4+ does not function in coesite. In contrast, we have confirmed the positive correlation between the B contents and the B-based hydrogen concentrations. The hydrogen-incorporation mechanism H+ + B3+ ↔ Si4+ readily takes place in coesite at different P-T conditions, and significantly increases the water content at both liquid-saturated and liquid-undersaturated conditions. For the SiO2–H2O system, we have found that type-I hydrogarnet substitution plays a dictating role in incorporating water into coesite at liquid-saturated condition, type-II hydrogarnet substitution contributes significantly at nearly dry condition, and both operate at conditions in between. The water solubility of coesite, as dictated by the type-I hydrogarnet substitution, positively correlates with both P and T, cH2O = −105(30) + 5.2(32) × P + 0.112(26) × T, with cH2O in wt ppm, P in GPa and T in °C. Due to its low water solubility and small fraction in subducted slabs, coesite may contribute insignificantly to the vertical water transport in subduction zones. Furthermore, the water solubility of any coesite in exhuming ultra-high pressure metamorphic rocks should be virtually zero as coesite becomes metastable. With an adequately fast water-diffusion rate, this metastable coesite should be completely dry, which may have been the key factor to the partial preservation of most natural Coe. As a byproduct, a new IR experimental protocol for accurate water determination in optically anisotropic nominally anhydrous minerals has been found. Aided with the empirical method of Paterson (1982) it employs multiple unpolarized IR spectra, collected from randomly-orientated mineral grains, to approximate both total integrated absorbance and total integrated molar absorption coefficient. Its success relies on a high-level orientation randomness in the IR analyses.
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- 2021
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8. Trace element characteristics of pyrite in Dongguashan Cu (Au) deposit, Tongling region, China
- Author
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Jiancheng Xie, Likai Ge, Lin Qian, Quanzhong Li, and Weidong Sun
- Subjects
Laser ablation ICP-MS ,Trace elements ,Pyrite ,Dongguashan Cu (Au) deposit ,Tongling region ,Geology ,QE1-996.5 - Abstract
The Dongguashan deposit is the largest and deepest Cu (Au) deposit in the Tongling region, eastern China. The presence of skarn and stratiform ore bodies in the same system of the Dongguashan deposit has caused much debate as to whether the mineralization was associated with magmatic-hydrothermal or sedimentary origin. In this study, in situ (LA-ICP-MS and EPMA) elemental compositions of medium-to coarse-grained euhedral pyrite from the stratiform and skarn ore bodies, and pyritization marble are investigated in the Dongguashan deposit. The results of the studied pyrite samples have relatively consistent trace element composition characteristics and several genetically significant elemental combinations. Gold and Ag are mainly of lattice bound appearance in pyrite. The Pb, Cu, Sb and Tl elements are mainly incorporated into the pyrite structure as substitutions. The distinctly trace element distribution correlations (e.g., Mn, Se and Tl) of the studied pyrites indicate that they were formed in a high temperature and oxidizing environment. Low Au (1) and Se/Tl (>10) ratios of the studied pyrites imply that the Dongguashan deposit is most likely to be a magmatic-hydrothermal origin.
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- 2020
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9. Effect of Particle Size and Dosing of Polymeric Aluminum Chloride Waste Residue on Cement Mortar
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Weitao Yang, Zhenguo Hou, Haiying He, Ping Xu, Weidong Sun, Yingbin Wang, and Jian Gong
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Geology ,QE1-996.5 - Abstract
Five particle sizes and six dosages of polymerized aluminum chloride (PAC) residue were taken to prepare polymerized aluminum chloride residue cement mortar (PACRM). The compressive and flexural strengths were tested, and SEM analysis was performed. The results showed that the change pattern of strength of PAC waste residue mixed into cement mortar was similar to that of fly ash at the same substitution rate. However, the strength of PACRM decreased with the increase of substitution rate. The flexural and compressive strengths of PACRM reached their peak at all ages after replacing cement with PAC waste residue with particle size of 0-0.075 mm and 30% doping. Their strength ratios were greater than 62%. It does not contribute much to the early strength development of PACRM, but contributes more to the later strength development after the cement is replaced by PAC waste residue. PAC waste residue mainly acts as microaggregate and fills into the mortar pores at low substitution rate. The cracks of the matrix structure are filled by C-S-H, so the mortar structure is more dense and the material strength is enhanced. When the substitution rate increases, the water requirement of mortar increases, resulting in an uncompact structure. The internal pores increase after hardening, and the mortar strength decreases rapidly.
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- 2022
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10. Geochemistry and genesis of the Nadun Nb-enriched arc basalt in the Duolong mineral district, western Tibet: Indication of ridge subduction
- Author
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Tian-Yu Zhang, Jianghong Deng, Ming Wang, Cai Li, Lipeng Zhang, and Weidong Sun
- Subjects
Tibet ,Duolong porphyry Cu–Au deposit ,Nb-enriched arc basalt ,Tethys ocean ,Ridge subduction ,Geology ,QE1-996.5 - Abstract
The Duolong mineral district in western Tibet is one of the largest porphyry Cu–Au deposit fields with significant metallogenic potential in China. Its tectonic environment relevant to Early Cretaceous Cu–Au mineralization remains controversial. Here we report new whole-rock major and trace element, and Sr-Nd-Hf-Pb isotopic data for the newly discovered basalt in the Nadun area, Duolong mineral district, to decipher their genesis and further constrain the tectonic environment. A contemporaneous rhyolite sample interbedded with the basalt in the lower part of the volcanic section in the Nadun area yields an LA-ICP-MS zircon U–Pb age of 122.5 ± 1.2 Ma. The basalt samples exhibit high-K calc-alkaline/shoshonite properties and are enriched in high field strength elements, e.g., high TiO2 (1.43–1.79 wt.%) and Nb (14.6–19.5 ppm) contents, with high Nb/La ratios (0.4–0.6), which are compositionally comparable to those of Nb-enriched arc basalts (NEABs). The (87Sr/86Sr)i ratios of 0.7052 to 0.7056, negative εNd(t) (− 0.7 to − 0.2) and εHf(t) values (+ 6.0 to + 6.5), and high (206Pb/204Pb)i, (207Pb/204Pb)i, (208Pb/204Pb)i and ratios (18.522 to 18.561, 15.641 to 15.645 and 38.679 to 38.730, respectively) suggest that the Nadun NEABs are more enriched than those of the island arc basalts (IABs) in the area. The slightly enriched radiogenic isotopes for the Nadun NEABs indicate that the subducting sediments play an important role in the source. Furthermore, their high Nb, Ti, and Cu contents indicate that the source mantle wedge was metasomatized by slab melts. The Nadun NEAB and other coeval magmatic rocks in the Duolong mineral district, including adakite, OIB-like basalt, MORB-type basalt, A-type rhyolite, and common IAB, are typical rock assemblages of ridge subduction. We infer that the Duolong mineral district were formed by ridge subduction in the Early Cretaceous.
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- 2022
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11. Ore deposits in the Lower Yangtze River Belt
- Author
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Weidong Sun
- Subjects
Geology ,QE1-996.5 - Published
- 2021
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12. 'Yanshanian Movement' induced by the westward subduction of the paleo–Pacific plate
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Zhe-Kun Zhang, Ming-Xing Ling, Wei Lin, Ming Sun, and Weidong Sun
- Subjects
Yanshanian movement ,Subduction ,Paleo–Pacific plate ,North China Craton ,Analogue modelling ,Geology ,QE1-996.5 - Abstract
Mountain building (orogeny) has a strong causal relationship with compression induced by plate drifting. It is generally accepted that orogenic belts are distributed perpendicular to the direction of plate movement. Extensive Late Mesozoic intra-continental deformations occurred around the North China Craton (NCC) in three different directions (i.e. EW-, WNW- and NNE-striking), which were previously attributed to three different geodynamic processes; the closure of the Mongolia-Okhotsk Ocean, convergence of the NCC and the South China block, and subduction of the paleo-Pacific plate. Remarkably, all these tectonic events were synchronised. Analogue modelling experiments were used to constrain far-field stress and basement shapes, to reconsider tectonic evolution around the NCC during this period. Results showed that all of these tectonic deformations could be plausibly interpreted as a unitary geodynamic regime governed by the westward indentation of the wedge-shaped NCC, driven by subduction of the paleo-Pacific plate. Mountain chains were formed along the edges of the wedge, indicating that the distribution of orogenic belts is not necessarily correlated with the direction of plate movement.
- Published
- 2020
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13. The Late Mesozoic granodiorite and polymetallic mineralization in southern Anhui Province, China: A perspective from apatite geochemistry
- Author
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Lin Qian, Yu Wang, Jiancheng Xie, and Weidong Sun
- Subjects
Geology ,QE1-996.5 - Abstract
The region of southern Anhui Province (SAP) is one of Late Mesozoic magmatic belts and copper-molybdenum-gold-tungsten polymetallic ore districts in China, but the relationship of polymetallic mineralization and related granodiorite remains unclear. Previous studies indicate that apatite can be an indicator for magmatic evolution and mineral exploration. In this study, apatites from the SAP ore-bearing granodiorites were investigated using observations from the electron microscope, electron probe microanalysis (EPMA), laser-ablation inductively-coupled plasma-mass spectrometry (LA-ICP-MS). The studied apatite samples identified as fluorapatite, show high F (2.69–4.13 wt.%) and low Cl contents (mainly
- Published
- 2019
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14. Geochemistry of subducted metabasites exhumed from the Mariana forearc: Implications for Pacific seamount subduction
- Author
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Jianghong Deng, Lipeng Zhang, He Liu, Haiyang Liu, Renqiang Liao, Abdul Shakoor Mastoi, Xiaoyong Yang, and Weidong Sun
- Subjects
IODP 366 ,Mariana convergent margin ,Forearc ,Seamount subduction ,OIB ,Geology ,QE1-996.5 - Abstract
Seamounts on the drifting oceanic crust are inevitably carried by plate motions and eventually accreted or subducted. However, the geochemical signatures of the subducted seamounts and the significance of seamount subduction are not well constrained. Hundreds of seamounts have subducted beneath the Philippine Sea Plate following the westward subduction of the Pacific Plate since the Eocene (~52 Ma). The subducted oceanic crust and seamount materials can be exhumed from the mantle depth to the seafloor in the Mariana forearc region by serpentinite mud volcanoes, providing exceptional opportunities to directly study the subducted oceanic crust and seamounts. The International Ocean Discovery Program (IODP) expedition 366 has recovered a few metamorphosed mafic clasts exhumed from the Mariana forearc serpentinite mud volcanoes, e.g., the Fantangisña and Asùt Tesoru seamounts. These mafic clasts have tholeiitic to alkaline affinities with distinct trace elements and Nd-Hf isotopes characteristics, suggesting different provenances and mantle sources. The tholeiites from the Fantangisña Seamount have trace element characteristics typical of mid-ocean ridge basalt. The Pacific-type Hf-Nd isotopic compositions, combined with the greenschist metamorphism of these tholeiites further suggest that they came from the subducted Pacific oceanic crust. The alkali basalts-dolerites from the Fantangisña and Asùt Tesoru seamounts show ocean island basalt (OIB)-like geochemical characteristics. The OIB-like geochemical signatures and the low-grade metamorphism of these alkali basalts-dolerites suggest they came from subducted seamounts that originally formed in an intraplate setting on the Pacific Plate. The Pacific Plate origin of these metabasites suggests they were formed in the Early Cretaceous or earlier.Two types of OIBs have been recognized from alkali metabasites, one of which is geochemically similar to the HIMU-EMI-type OIBs from the West Pacific Seamount Province, and another is similar to the EMII-type OIBs from the Samoa Island in southern Pacific, with negative Nb-Ta-Ti anomalies and enriched Nd-Hf isotopes. Generally, these alkali metabasites are sourced from the heterogeneous mantle sources that are similar to the present South Pacific Isotopic and Thermal Anomaly. This study provides direct evidence for seamount subduction in the Mariana convergent margins. We suggest seamount subduction is significant to element cycling, mantle heterogeneity, and mantle oxidation in subduction zones.
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- 2021
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15. Corrigendum to 'Yanshanian movementˮ induced by the westward subduction of the paleo–Pacific plate [Solid Earth Sciences Volume 5 (2) (2020) 103–114]
- Author
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Zhe-Kun Zhang, Ming-Xing Ling, Wei Lin, Ming Sun, and Weidong Sun
- Subjects
Geology ,QE1-996.5 - Published
- 2021
- Full Text
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16. New discrimination diagrams for basalts based on big data research
- Author
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Qi Zhang, Weidong Sun, Yong Zhao, Fanglin Yuan, Shoutao Jiao, and Wanfeng Chen
- Subjects
big data ,discrimination diagram ,tectonic settings ,svm ,georoc ,Geography. Anthropology. Recreation ,Geology ,QE1-996.5 - Abstract
In recent days, discrimination diagrams have been widely used for tracing the tectonic settings and origins of basalts from orogenic belts. However, conventional discrimination diagrams are not accurate enough. Here, we reported six new discrimination diagrams obtained from the global database using data mining methods. For most individual diagrams, island arc basalt can be nearly 100% was identified, whereas ocean island basalt and mid-ocean ridge basalt can be discriminated from each other with less than 10% of overlap, under a confidence coefficient of 85%. Using the six new discrimination diagrams together, basalts of different origins can be efficiently identified.
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- 2019
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17. Thermodynamic and Elastic Properties of Magnesite at Mantle Conditions: First‐Principles Calculations
- Author
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Chao Yao, Zhongqing Wu, Fan Zou, and Weidong Sun
- Subjects
magnesite ,first‐principles calculations ,thermoelasticity ,thermodynamic properties ,elastic anisotropy ,high pressure and temperature ,Geophysics. Cosmic physics ,QC801-809 ,Geology ,QE1-996.5 - Abstract
Abstract Magnesite (MgCO3) is a likely main host of carbonates in the mantle and plays an important role in the transport and storage of carbon in the Earth's mantle. Its physical properties at high pressure and high temperature (PT) are crucial for understanding the deep carbon cycle. Here we investigated thermodynamic and elastic properties of magnesite under the mantle PT conditions using first‐principles calculations with local density approximation (LDA). Magnesite has the seismic velocities close to those of forsterite. The effect of the magnesite on seismic velocity of the carbonated peridotite and eclogite is subtle in the upper mantle. However, magnesite has much smaller seismic velocities and far larger elastic anisotropy than major minerals in the transition zone and lower mantle. The enrichment of magnesite in the transition zone and lower mantle will likely produce seismically detectable low‐velocity zone and velocity anisotropy.
- Published
- 2018
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18. The production of iron oxide during peridotite serpentinization: Influence of pyroxene
- Author
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Ruifang Huang, Chiou-Ting Lin, Weidong Sun, Xing Ding, Wenhuan Zhan, and Jihao Zhu
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Serpentinization ,Iron oxide ,Peridotite ,Orthopyroxene ,Silica ,Aluminum ,Geology ,QE1-996.5 - Abstract
Serpentinization produces molecular hydrogen (H2) that can support communities of microorganisms in hydrothermal fields; H2 results from the oxidation of ferrous iron in olivine and pyroxene into ferric iron, and consequently iron oxide (magnetite or hematite) forms. However, the mechanisms that control H2 and iron oxide formation are poorly constrained. In this study, we performed serpentinization experiments at 311 °C and 3.0 kbar on olivine (with
- Published
- 2017
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19. The age of the Ordovician-Silurian boundary and the End Ordovician Mass Extinction
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Weidong Sun
- Subjects
Geology ,QE1-996.5 - Published
- 2020
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20. Challenges in Solid Earth Sciences
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Weidong Sun
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Geology ,QE1-996.5 - Published
- 2016
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21. Fluids, Metals, and Mineral/Ore Deposits
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Xing Ding, Daniel E. Harlov, Bin Chen, and Weidong Sun
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Geology ,QE1-996.5 - Published
- 2018
- Full Text
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22. The initiation of plate subduction
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Weidong Sun
- Subjects
Geology ,QE1-996.5 - Published
- 2017
- Full Text
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23. The geomicrobiology of bauxite deposits
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Xiluo Hao, Kwunlun Leung, Rucheng Wang, Weidong Sun, and Yiliang Li
- Subjects
Geomicrobiology ,Bauxite ,Microbial activity ,Microbial-mediated release of elements ,Biomineralization ,Geology ,QE1-996.5 - Abstract
Bauxite deposits are studied because of their economic value and because they play an important role in the study of paleoclimate and paleogeography of continents. They provide a rare record of the weathering and evolution of continental surfaces. Geomicrobiological analysis makes it possible to verify that microorganisms have played a critical role during the formation of bauxite with the possibility already intimated in previous studies. Ambient temperature, abundance of water, organic carbon and bioavailable iron and other metal substrates provide a suitable environment for microbes to inhabit. Thiobacillus, Leptospirilum, Thermophilic bacteria and Heterotrophs have been shown to be able to oxidize ferrous iron and to reduce sulfate-generating sulfuric acid, which can accelerate the weathering of aluminosilicates and precipitation of iron oxyhydroxides. Microorganisms referred to the genus Bacillus can mediate the release of alkaline metals. Although the dissimilatory iron-reducing and sulfate-reducing bacteria in bauxites have not yet been identified, some recorded authigenic carbonates and “bacteriopyrites” that appear to be unique in morphology and grain size might record microbial activity. Typical bauxite minerals such as gibbsite, kaolinite, covellite, galena, pyrite, zircon, calcium plagioclase, orthoclase, and albite have been investigated as part of an analysis of microbial mediation. The paleoecology of such bauxitic microorganisms inhabiting continental (sub) surfaces, revealed through geomicrobiological analysis, will add a further dimension to paleoclimatic and paleoenvironmental studies.
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- 2010
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24. Chemical variations of loess from the Chinese Loess Plateau and its implications
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Yuanyuan Xiao, Shengying Wu, Peishan Sui, Yaoling Niu, Weidong Sun, Guodong Wang, Juanjuan Kong, Fengli Shao, Xiaohong Wang, Hongmei Gong, Meng Duan, and Zihang Huang
- Subjects
Geology - Abstract
The Chinese Loess Plateau (CLP) is the largest loess deposit on Earth with expansive surface-exposed source rocks of varying origins, ages, and history. Here, we present abundances of elements on representative loess and palaeosol samples from seven classic sections of the CLP. Most elements, including soluble elements (e.g. Rb and Cs), show significant correlations with La or Al2O3. These correlations indicate that these elements are hosted or absorbed in particle minerals during weathering, transport, and deposition (e.g. mica, K-feldspar, and clay minerals). These new observations allow the use of La/X (‘X’ being the element of interest) and the estimated La abundance of 31 ppm in the model upper continental crust (UCC) to estimate the abundances of other elements. The results show higher Cs (Cs = 6.7 ± 1.2 ppm), lower transition metals, Ba, and Ga. Given the high CaO and presence of carbonate in UCC rocks of both vast western China (the primary source for the CLP) and eastern China, we propose that these updates on the element abundances represent a refined model for the carbonate-bearing UCC.
- Published
- 2022
25. Unusual δ26Mg values in oceanic crust basalts from the South China Sea
- Author
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Renqiang Liao, Hongli Zhu, Lipeng Zhang, He Li, Congying Li, Yongsheng He, Weidong Sun, and He Liu
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Geology - Abstract
Whether or not oceanic crust basalts are affected by plate subduction is a hot topic of debate. The South China Sea is one of the largest marginal basins in the western Pacific Ocean and has been surrounded by subduction of the Pacific plate and Indian plate, yet, to date, no study has clearly shown evidence of subduction in the geochemistry of volcanism in the basin due to a lack of sampling of igneous crust basalts on the seafloor. The International Ocean Discovery Program Expedition 349 cored seafloor basalts near the fossil spreading ridges of the eastern (Site U1431) and southwestern (Site U1433 and U1434) subbasins in the South China Sea. The recovered basalt samples indicated a pyroxenite-bearing peridotite mantle source. Here, we report Mg isotopic data from 14 of these oceanic crust basalt samples. The δ26Mg values of most basalts from the three drill holes were higher (up to −0.10‰) than that of the average mantle (−0.25‰). The lack of correlations of δ26Mg with geochemical indices of magmatic processes (e.g., MgO, CaO/Al2O3, La/Sm, Nb/Zr) suggests that crystal fractionation and partial melting had insignificant effects on the Mg isotopic compositions of the South China Sea basalts. Thus, the variations in Mg isotopes were inherited from their mantle sources. Considering the highly varied Ce/Pb ratios and elevated 87Sr/86Sr values but mantle-like 143Nd/144Nd values, we propose that the varied δ26Mg values were likely caused by metasomatism of subduction-released fluids. The coupling of Mg and Sr-Fe isotopes provides robust evidence that the high-δ26Mg values of the South China Sea basalts resulted from mixing among pyroxenite-bearing peridotite mantle, the nearby Hainan plume materials, and subducting serpentinite-released fluids. Therefore, these Mg isotopes suggest that the mantle source of the South China Sea basalts was influenced by subducted materials, providing further evidence of the initial expansion, formation, and evolution of the South China Sea during plate subduction.
- Published
- 2022
26. Comparison of Granites from the Eastern and Western Districts of the Gejiu Ore District in South China: Implication for Petrogenesis and Tin Metallogeny
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Saijun Sun, Junjie Zhang, Shuang Li, Haobin Niu, Zhaojian Wu, and Weidong Sun
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Geology ,Geotechnical Engineering and Engineering Geology ,Late Cretaceous granite ,magma source ,melting condition ,biotite ,Gejiu tin ore - Abstract
Late Cretaceous granitoids are developed in the eastern and western districts of the Gejiu ore district, but tin deposits mainly occur in the eastern district, and the reasons for the difference in mineralization between the eastern and western districts are still controversial. Considering the main factors controlling granite Sn fertility, the whole-rock geochemical characteristics of granites on both sides are compared. LA-ICP-MS zircon U-Pb analyses of the Gejiu granites yielded two age periods: the early phase from 79.2 to 83.3 Ma and the later phase from 73.8 to 75.6 Ma. The western district granites have higher zircon εHf(t), CaO/Na2O, Ba, and Sr concentrations and lower Rb/Sr ratios than the eastern district granites, indicating that the western district granites have more mantle-derived materials in the source than the eastern district granites. Results of oxygen fugacity show that the western granites have a higher oxygen fugacity condition. More depleted Ba, Sr, P, Eu and Ti characteristics with obviously negative Eu anomalies in the eastern granites also have high Rb/Sr ratios and low Nb/Ta and Zr/Hf ratios, indicating that the eastern granites experienced highly magmatic differentiation, attributed to high volatile F contents that can reduce the viscosity and solidus of magma. Combined with the differences in field observations and structural styles, on the whole, the western district granites have higher oxygen fugacities and lower F contents and magmatic differentiation than those in the eastern district granites, indicating that the western district granites are not conducive to mineralization.
- Published
- 2023
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27. Tracing black shales in the source of a porphyry Mo deposit using molybdenum isotopes
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Qiqi Xue, Lipeng Zhang, Shuo Chen, Kun Guo, Tao Li, Zhong Han, and Weidong Sun
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Geology - Abstract
Porphyry Mo deposits are important suppliers of molybdenum for industrial applications, but the origin and source of metals in these deposits remain debated. Here, we present Mo isotope data for Miocene mineralized porphyritic monzogranites (MPMs) and Paleocene barren biotite monzogranites and tuffs (BMTs) from the Bangpu porphyry Mo (Cu) deposit in the Gangdese metallogenic belt. The results show that the MPMs display radiogenic Sr and Pb isotopes and elevated δ98/95Mo (relative to NIST SRM 3134; +0.07‰–1.2‰) and Mo contents, which exceed the range of the depleted mantle. These characteristics cannot be attributed to surface weathering, hydrothermal alteration, magmatic differentiation, or partial melting but rather reflect the incorporation of Mo from black shales into their magma sources, as evidenced by the significant correlations between δ98/95Mo and εNd(t) and aluminum saturation index (ASI) values. In contrast, the BMTs display lower Mo and δ98/95Mo values than the mineralized samples, and their δ98/95Mo values display no correlations with radiogenic isotopes or ASI values. The contrasting characteristics of mineralized and barren samples provide strong evidence that the addition of black shales played an important role in the formation of the Bangpu porphyry Mo deposit. Our study thus establishes a possible link between porphyry Mo deposits and organic-rich sediments and highlights the great potential of Mo isotopes in studying porphyry Mo deposits.
- Published
- 2023
28. Study on Local Yielding Effect and Energy Evolution Law of Deep Roadway
- Author
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Zhijia Wang, Wenlong Wu, Feiyue Sun, Weidong Sun, and Pengfei Li
- Subjects
Architecture ,Soil Science ,Geology ,Geotechnical Engineering and Engineering Geology - Published
- 2022
29. Redox-sensitive elements of Ediacaran black shales in South China with implications for a widespread anoxic ocean
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Yufei Hao, He Liu, Qian Chen, Weidong Sun, and Jing Huang
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Geology ,Earth-Surface Processes - Published
- 2023
30. Unraveling the link between mantle upwelling and formation of Sn-bearing granitic rocks in the world-class Dachang tin district, South China
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Reimar Seltmann, Rongqing Zhang, Ming-Xing Ling, Kai Wu, Jia Guo, Weidong Sun, and Congying Li
- Subjects
Bearing (mechanical) ,South china ,Granitic rock ,Geochemistry ,chemistry.chemical_element ,Geology ,Mantle (geology) ,law.invention ,World class ,chemistry ,law ,Upwelling ,Tin - Abstract
Increasing evidence shows that the mantle contributes (directly or indirectly) to Sn-bearing granites worldwide. However, the specific role of mantle in the formation of tin granites and related mineralization remains poorly understood. In the world-class Dachang district, South China, tin mineralization is related to the Longxianggai equigranular/porphyritic biotite granites and tin orebodies are cut by granite porphyry dykes hosting mafic microgranular enclaves (MMEs). A combination of zircon U-Pb dating and Hf-O isotopes, mineral chemistry, and whole-rock elemental and Sr-Nd isotopic compositions—for granitic rocks and MMEs, is employed to constrain the petrogenesis and to unravel the link between tin fertility and mantle upwelling. Laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) zircon U-Pb dating indicates that the biotite granites were emplaced at ca. 93 Ma, and the granite porphyry dykes and MMEs were formed at ca. 86 Ma. The biotite granites are silica- and alkali-enriched with A/CNK ratios of 1.04–1.36, and exhibit elevated concentrations of Li, F, P, Rb, Cs, Ta, Sn, W, and U, showing affinities with highly fractionated S-type granites. Whole-rock geochemical and Nd isotopic (εNd(t) = −10.0 to −7.8) data, and in situ zircon Hf-O (εHf(t) = −9.9 to −3.9, δ18O = 6.2–8.9‰) isotopes indicate that the biotite granites were formed by partial melting of metasedimentary rocks at relatively high temperatures (≥782 °C), possibly with minor input of mantle material. Likewise, the post-ore granite porphyry dykes have similar chemical and mineralogical characteristics as fractionated S-type granites. Zircon Hf-O isotopes (εHf(t) = −9.0 to −4.9, δ18O = 6.5–8.2‰) and whole-rock geochemical data suggest they were derived from a similar source as the biotite granites, whereas elevated εNd(t) values of −5.0 to −3.3 for granite porphyry dykes relative to biotite granites reveal an increasing mantle input. Distinct εNd(t) (−0.4 and −0.3) and zircon Hf-O (εHf(t) = 1.5–5.0, δ18O = 6.5–7.2‰) isotopes of the MMEs, suggest that the mafic melt could be sourced from the asthenospheric mantle, contaminated by subcontinental lithospheric mantle/continental crust during magma ascent, and hybridized by felsic melt at emplacement-level. The magmatic sequence in the Dachang district is indicative of an extensional tectonic setting where mantle-derived magmas are predicted to migrate to shallower crustal levels as the crust progressively becomes thinner and hotter. High-temperature partial melting of mature metasedimentary crust triggered by heat input from the upwelled mantle, may contribute to biotite breakdown, which is important for concentrating tin in melts. Fractional crystallization of initially Sn-rich felsic melts under reduced conditions makes further tin enrichment and produces Sn-bearing granites (the Longxianggai pluton). Prolonged mantle upwelling results in distinct magma mixing and the formation of granite porphyry dykes and MMEs. These dykes are highly fractionated with elevated Sn and W contents, which show great potential to form hydrothermal Sn-W mineralization.
- Published
- 2021
31. Sediment recycling and adakite petrogenesis: Constraints from the late Ordovician tonalite in the North Qilian suture zone
- Author
-
Yuxiao Chen, Ying Cui, Lipeng Zhang, Shanming Fu, Kai Wu, Shuguang Song, Weidong Sun, and Tangfu Xiao
- Subjects
Geochemistry and Petrology ,Geology - Published
- 2023
32. Magnesium isotopic composition of the Mariana forearc serpentinite: Implications for Mg isotopic composition of the mantle wedge and Mg isotopic fractionation during mantle wedge serpentinization
- Author
-
Yiran Wang, Jianghong Deng, Renqiang Liao, Long Chen, Dongyong Li, He Liu, and Weidong Sun
- Subjects
Geochemistry and Petrology ,Geology - Published
- 2023
33. Water solubility in coesite at realistic temperatures of subduction zones
- Author
-
Wei Yan, Mingda Lv, Dan Wu, Weidong Sun, Xiaohu Li, Mingyue He, and Xi Liu
- Subjects
Geochemistry and Petrology ,Geology - Published
- 2023
34. Subduction of the Neo-Tethys ridge beneath the Eurasian continent during the Cretaceous
- Author
-
Lipeng Zhang, Jianghong Deng, Saijun Sun, Qinglin Sui, Kun Wang, and Weidong Sun
- Subjects
Geochemistry and Petrology ,Economic Geology ,Geology - Published
- 2023
35. The Caroline Ridge fault system and implications for the bending-related faulting of incoming oceanic plateaus
- Author
-
Zhengyi Zhang, Dongdong Dong, Guangxu Zhang, and Weidong Sun
- Subjects
geography ,geography.geographical_feature_category ,Rift ,010504 meteorology & atmospheric sciences ,Subduction ,Trough (geology) ,Geology ,Oceanic plateau ,Fault (geology) ,010502 geochemistry & geophysics ,01 natural sciences ,Horst and graben ,Paleontology ,Abyssal hill ,Ridge (meteorology) ,0105 earth and related environmental sciences - Abstract
The latest multichannel seismic data from the Yap subduction zone is presented to investigate the Caroline Ridge fault system, developed by faulting and bending processes within the incoming oceanic plateau. We reveal that horst and graben structures exist along the entire incoming Caroline Ridge adjacent to the trench and that pervasive bending-related faults trending ~N30°E have developed subparallel to the trench. However, the widths of the horst and graben structures decrease gradually from north to south. The two-stage ancient abyssal hill fabrics overlap the incoming Caroline Ridge. Abyssal hill faults trending ~N65°W present large trench-ridge angles (85–90°); in the southern segment, abyssal hill faults trending ~N70°E have relatively low trench-ridge angles (~35–40°). From the Caroline Ridge to the horst and graben structures, the topography decreases, and slump bodies with deformed internal reflections have developed above an irregular reflector. Little stable pelagic sediment with horizontal reflectors accumulates on the horst and graben structures, suggesting that the faulting and bending processes involve long and intense tectonic processes that affect the sedimentary environment. The sedimentary strata and fault distributions differ between the North and South Caroline Ridge, which is primarily attributable to the different rifting processes. Furthermore, we propose that N65°W-trending ancient faults sufficiently decrease the yield strength of the incoming Caroline Ridge to facilitate the bending-related faulting. During subduction, the incoming North Caroline Ridge that has a large degree of rifting and the Sorol Trough, which has a thin crust, may resist less flexural bending and generate the wide horst and graben structures. The ancient faults and rifting model of incoming oceanic plateaus play a significant role in bending-related faulting
- Published
- 2021
36. Boron, arsenic and antimony recycling in subduction zones: New insights from interactions between forearc serpentinites and CO2-rich fluids at the slab-mantle interface
- Author
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Jia Guo, Jianghong Deng, Zhian Bao, Honglin Yuan, Weidong Sun, Chunlei Zong, Robert E. Zartman, Kai Wu, and Lipeng Zhang
- Subjects
010504 meteorology & atmospheric sciences ,Subduction ,Spinel ,Carbonate minerals ,Geochemistry ,chemistry.chemical_element ,engineering.material ,010502 geochemistry & geophysics ,01 natural sciences ,Mantle (geology) ,Antimony ,chemistry ,Geochemistry and Petrology ,Slab ,engineering ,Boron ,Forearc ,Geology ,0105 earth and related environmental sciences - Abstract
Hydrous minerals in the hybridized zone at the slab-mantle interface play a critical role in retaining and transporting fluid mobile elements in subduction zones. The observed high B and As concentrations and high δ11B values in arc magmas were previously thought to have been resulted from the mechanical transport of forearc serpentinites down to subarc depths by mantle corner flows or through subduction channels because B, As, and Sb are mostly released during early stages of subduction. This study provides new insights into the recycling of B, As, and Sb in subduction zones via an in-situ study on a set of carbonate-bearing serpentinite samples from the Mianlue melange complex in the Qinling Orogen. Petrological observations and bulk-rock Sr-Pb isotopes reveal that the Jianchaling serpentinites were formed by interactions between forearc peridotites and sediment-derived fluids at a shallow depth in the subduction channel. Some Jianchaling serpentinites experienced the lizardite to antigorite transition at 300–400 °C with infiltrations of CO2-rich fluids. In contrast, the Liangyazi antigorite serpentinites were produced at a greater depth. Antigorite grains in the Jianchaling serpentinites have lower Feapfu than those in the Liangyazi serpentinites and most antigorite with geochemical data in the literature. Meanwhile, B, As, and Sb concentrations of Fe-poor antigorite from the Jianchaling serpentines (385–653 ppm B, 198–334 ppm As, and 6.24–8.01 ppm Sb) are not only higher than those of the Fe-rich antigorite from the Liangyazi serpentinites but also 2–3.5 times higher than those of the surrounding lizardite. The lower modal percentage of spinel and ferritchromite in antigorite veinlets, together with the lower bulk-rock FeO content of antigorite-lizardite serpentinites than that of lizardite serpentinites from the Jianchaling region, indicates that some FeO might be lost during the lizardite to antigorite transition. The presence of carbonate minerals in the antigorite veinlets and the remarkably high B, As, and Sb concentrations in the Jianchaling antigorite indicate that the penetrating fluids during the lizardite to antigorite transition are most likely derived from sediment and metabasite decarbonations at
- Published
- 2021
37. The big mantle wedge and decratonic gold deposits
- Author
-
Weidong Sun and Rixiang Zhu
- Subjects
geography ,geography.geographical_feature_category ,010504 meteorology & atmospheric sciences ,Mantle wedge ,Subduction ,Pargasite ,Partial melting ,Geochemistry ,010502 geochemistry & geophysics ,01 natural sciences ,Craton ,Transition zone ,Slab ,General Earth and Planetary Sciences ,Metasomatism ,Geology ,0105 earth and related environmental sciences - Abstract
The Circum-Pacific subduction zone is a famous gold metallogenic domain in the world, with two important gold metallogenic provinces, the North China Craton and Nevada, which are related to the destruction of the North China Craton and the Wyoming Craton, respectively. Their ore-forming fluids were possibly derived from the stagnant slab in the mantle transition zone. The oceanic lithospheric mantle usually contains serpentine layers up to thousands of meters thick. During plate subduction, serpentine is dehydrated at depths of 300 km. The overlying big mantle wedge is hydrated during the breakdown of these hydrous facies in the mantle transition zone. The dehydration of the subducted slab in the big mantle wedge releases sulfur-rich fluid, which extracts gold and other chalcophile elements in the surrounding rocks, forming gold-rich fluid. Because the cratonic geotherm is lower than the water-saturated solidus line of lherzolite, the fluid cannot trigger partial melting. Instead, it induces metasomatism and forms pargasite and other water-bearing minerals when it migrates upward to depths of less than 100 km in the cratonic lithospheric mantle, resulting in a water- and gold-rich weak layer. During the destruction of craton, the weak layer is destabilized, releasing gold-bearing fluids that accelerate the destruction. The ore-forming fluids migrate along the shallow weak zone and are accumulated at shallow depths, and subsequently escape along deep faults during major tectonic events, leading to explosive gold mineralization. The ore-forming fluids are rich in ferrous iron, which releases hydrogen at low pressure through iron hydrolysis. Therefore, decratonic gold deposits are often reduced deposits.
- Published
- 2021
38. Diachronous subduction of the Proto-Tethys Ocean along the northern margin of East Gondwana: Insights from SHRIMP and LA-ICP-MS zircon geochronology in the West Kunlun Orogenic Belt, Northwestern China
- Author
-
Denghui Chen, Xiaofeng Gao, Xianfeng Zha, Lipeng Zhang, Xiaojian Zhao, Qinglin Sui, Jiming Sun, and Weidong Sun
- Subjects
Subduction ,020209 energy ,Geochemistry ,Geology ,02 engineering and technology ,Diachronous ,010502 geochemistry & geophysics ,Tethys Ocean ,01 natural sciences ,Gondwana ,Geochronology ,0202 electrical engineering, electronic engineering, information engineering ,Igneous differentiation ,0105 earth and related environmental sciences ,Terrane ,Zircon - Abstract
The geological evolution of the Proto-Tethys Ocean remains vague. The Tianshuihai Terrane (TSHT), a subterrane of the West Kunlun, distributed to the south of the Proto-Tethys Ocean during the Earl...
- Published
- 2021
39. Trace element characteristics of pyrite in Dongguashan Cu (Au) deposit, Tongling region, China
- Author
-
Lin Qian, Weidong Sun, Likai Ge, Jiancheng Xie, and Quanzhong Li
- Subjects
Mineralization (geology) ,010504 meteorology & atmospheric sciences ,Geochemistry ,Dongguashan Cu (Au) deposit ,Skarn ,Electron microprobe ,engineering.material ,010502 geochemistry & geophysics ,01 natural sciences ,Geochemistry and Petrology ,Trace element composition ,0105 earth and related environmental sciences ,Earth-Surface Processes ,Trace elements ,Laser ablation ICP-MS ,Pyrite ,Chemistry ,lcsh:QE1-996.5 ,Eastern china ,Trace element ,Geology ,Tongling region ,Geotechnical Engineering and Engineering Geology ,lcsh:Geology ,Geophysics ,engineering ,Sedimentary rock - Abstract
The Dongguashan deposit is the largest and deepest Cu (Au) deposit in the Tongling region, eastern China. The presence of skarn and stratiform ore bodies in the same system of the Dongguashan deposit has caused much debate as to whether the mineralization was associated with magmatic-hydrothermal or sedimentary origin. In this study, in situ (LA-ICP-MS and EPMA) elemental compositions of medium-to coarse-grained euhedral pyrite from the stratiform and skarn ore bodies, and pyritization marble are investigated in the Dongguashan deposit. The results of the studied pyrite samples have relatively consistent trace element composition characteristics and several genetically significant elemental combinations. Gold and Ag are mainly of lattice bound appearance in pyrite. The Pb, Cu, Sb and Tl elements are mainly incorporated into the pyrite structure as substitutions. The distinctly trace element distribution correlations (e.g., Mn, Se and Tl) of the studied pyrites indicate that they were formed in a high temperature and oxidizing environment. Low Au (1) and Se/Tl (>10) ratios of the studied pyrites imply that the Dongguashan deposit is most likely to be a magmatic-hydrothermal origin.
- Published
- 2020
40. Combined mica and apatite chemical compositions to trace magmatic-hydrothermal evolution of fertile granites in the Dachang Sn-polymetallic district, South China
- Author
-
Jia Guo, Gangyang Zhang, Lu Xiang, Rongqing Zhang, Lipeng Zhang, and Weidong Sun
- Subjects
Geochemistry and Petrology ,Economic Geology ,Geology - Published
- 2022
41. Coupled Fe–S isotope composition of sulfide chimneys dominated by temperature heterogeneity in seafloor hydrothermal systems
- Author
-
Shikui Zhai, Huaiming Li, Jing Huang, Weidong Sun, and Shujie Wang
- Subjects
chemistry.chemical_classification ,Multidisciplinary ,Sulfide ,Isotope ,Mineralogy ,engineering.material ,010502 geochemistry & geophysics ,01 natural sciences ,Hydrothermal circulation ,Seafloor spreading ,δ34S ,Isotope fractionation ,chemistry ,engineering ,Chimney ,Pyrite ,Geology ,0105 earth and related environmental sciences - Abstract
Seafloor hydrothermal chimneys are significant metal resources and have fundamental effects on marine chemistry balance. Previous studies on growth of the chimneys focused on mineral composition and elemental distribution in chimney walls, but the isotopic composition of different elements and their correlations remain poorly understood. Here, we report lateral Fe and S isotopes from sulfides across a chimney wall in detail from the Deyin-1 hydrothermal field (DHF) on the South Mid-Atlantic Ridge. Pyrite was characterized by increases in both δ34S and δ56Fe from the exterior to the interior within the chimney wall, which is likely related to enhanced S and Fe isotope fractionation between pyrite and fluids derived from the temperature gradient. Furthermore, δ56Fe displayed a well-defined, linear, positive correlation with δ34S in pyrite from the DHF as well as in pyrite from other areas. A model of hydrothermal pyrite formation suggests that, under conditions with uniform hydrothermal fluid, different temperatures and similar pyrite–fluid exchange degrees could result in the observed linear relationships between δ34S and δ56Fe. The regular and coupled Fe–S isotope variations within the chimney wall efficiently constrain the process of hydrothermal sulfide formation.
- Published
- 2020
42. Late Cambrian tonalite-trondhjemite association in the eastern segment of North Qilian suture zone: petrogenesis and geodynamic implications
- Author
-
Lipeng Zhang, Tangfu Xiao, Yuxiao Chen, Weidong Sun, Shanming Fu, Ying Cui, and Shuguang Song
- Subjects
Tectonics ,Fractional crystallization (geology) ,020209 energy ,0202 electrical engineering, electronic engineering, information engineering ,Geochemistry ,Geology ,02 engineering and technology ,Suture (geology) ,010502 geochemistry & geophysics ,01 natural sciences ,0105 earth and related environmental sciences ,Petrogenesis - Abstract
The late Cambrian tonalite-trondhjemite association in the eastern segment of North Qilian suture zone (E. NQSZ) is important for understanding of the sub-arc magmatic process and tectonic evolutio...
- Published
- 2020
43. Early cretaceous transformation from Pacific to Neo-Tethys subduction in the SW Pacific Ocean: Constraints from Pb-Sr-Nd-Hf isotopes of the Philippine arc
- Author
-
Weidong Sun, He Liu, Huasheng Qi, Al Emil Berador, Jianghong Deng, Lipeng Zhang, Xiaoyong Yang, Abdul Shakoor Mastoi, Zhaofeng Zhang, and Robert E. Zartman
- Subjects
Provenance ,010504 meteorology & atmospheric sciences ,Subduction ,Pacific Plate ,Partial melting ,010502 geochemistry & geophysics ,01 natural sciences ,Cretaceous ,Mantle (geology) ,Paleontology ,Geochemistry and Petrology ,Adakite ,Island arc ,Geology ,0105 earth and related environmental sciences - Abstract
The westward subduction of the Pacific plate interacted with the northward subduction of the eastern Neo-Tethys plate in the Early Cretaceous. However, the subduction polarities between these two plates in the Early Cretaceous is not well constrained. The proto-Philippine arc is suggested to have originated at the Pacific – Neo-Tethys intersection in the SW Pacific in the latest Jurassic – Early Cretaceous, and can provide information about the ancient interaction between these two plates. In this study, the oldest known Early Cretaceous mantle-derived arc volcanic rocks and slab-melting generated adakites occurring in the Philippine arc have been studied for Pb, Sr, Nd and Hf isotopes to discriminate the provenance of their mantle sources and/or subduction components. The 126–118 Ma Kansi island arc volcanics have Pacific-type Pb isotopes, suggesting that the subduction components in the source are mainly from the subducted Pacific plate. Their Hf-Nd isotopes give support to a mantle source that is isotopically transitional Pacific-Indian type. The formation of the Kansi volcanics dates the subduction of the Pacific plate under the transitional Pacific-Indian mantle as Early Cretaceous. The subsequent generation of the 110 Ma Kansi adakitic diorites with the similar Pacific-type Pb isotopes indicates further partial melting of the subducted Pacific plate. In contrast, the post-110 Ma Lutopan adakitic diorites have Indian-type Pb isotopes, indicating the subsequent subduction of an Indian-type oceanic slab in the eastern Neo-Tethys tectonic regime. Therefore, the proto-Philippine arc is constrained to have originated at the intersection between Indian-type and Pacific-type oceanic crusts and mantle domains. The successive generation of these Early Cretaceous arc rocks in the Philippines indicates that a transformation of the tectonic regime from southwestward Pacific subduction to northeastward subduction of the eastern Neo-Tethys plate in the SW Pacific Ocean occurred at ca. 110 Ma, due to the abrupt change in drifting direction of the Pacific plate.
- Published
- 2020
44. Geochemistry and genesis of the Nadun Nb-enriched arc basalt in the Duolong mineral district, western Tibet: Indication of ridge subduction
- Author
-
Cai Li, Ming Wang, Jianghong Deng, Tian-Yu Zhang, Weidong Sun, and Lipeng Zhang
- Subjects
Basalt ,QE1-996.5 ,Mantle wedge ,Subduction ,Geochemistry ,Trace element ,Nb-enriched arc basalt ,Ridge subduction ,Geology ,Tethys ocean ,Tibet ,Rhyolite ,Adakite ,General Earth and Planetary Sciences ,Island arc ,Duolong porphyry Cu–Au deposit ,Zircon - Abstract
The Duolong mineral district in western Tibet is one of the largest porphyry Cu–Au deposit fields with significant metallogenic potential in China. Its tectonic environment relevant to Early Cretaceous Cu–Au mineralization remains controversial. Here we report new whole-rock major and trace element, and Sr-Nd-Hf-Pb isotopic data for the newly discovered basalt in the Nadun area, Duolong mineral district, to decipher their genesis and further constrain the tectonic environment. A contemporaneous rhyolite sample interbedded with the basalt in the lower part of the volcanic section in the Nadun area yields an LA-ICP-MS zircon U–Pb age of 122.5 ± 1.2 Ma. The basalt samples exhibit high-K calc-alkaline/shoshonite properties and are enriched in high field strength elements, e.g., high TiO2 (1.43–1.79 wt.%) and Nb (14.6–19.5 ppm) contents, with high Nb/La ratios (0.4–0.6), which are compositionally comparable to those of Nb-enriched arc basalts (NEABs). The (87Sr/86Sr)i ratios of 0.7052 to 0.7056, negative eNd(t) (− 0.7 to − 0.2) and eHf(t) values (+ 6.0 to + 6.5), and high (206Pb/204Pb)i, (207Pb/204Pb)i, (208Pb/204Pb)i and ratios (18.522 to 18.561, 15.641 to 15.645 and 38.679 to 38.730, respectively) suggest that the Nadun NEABs are more enriched than those of the island arc basalts (IABs) in the area. The slightly enriched radiogenic isotopes for the Nadun NEABs indicate that the subducting sediments play an important role in the source. Furthermore, their high Nb, Ti, and Cu contents indicate that the source mantle wedge was metasomatized by slab melts. The Nadun NEAB and other coeval magmatic rocks in the Duolong mineral district, including adakite, OIB-like basalt, MORB-type basalt, A-type rhyolite, and common IAB, are typical rock assemblages of ridge subduction. We infer that the Duolong mineral district were formed by ridge subduction in the Early Cretaceous.
- Published
- 2022
45. Plate convergence in the Indo-Pacific region
- Author
-
Weidong Sun, Renqiang Liao, Sai-Jun Sun, He Liu, Lipeng Zhang, and Congying Li
- Subjects
geography ,geography.geographical_feature_category ,Subduction ,Pacific Plate ,Slab pull ,Transform fault ,Oceanography ,Plate tectonics ,Paleontology ,Oceanic crust ,Slab ,Oceanic basin ,Geology ,Water Science and Technology - Abstract
The Indo-Pacific convergence region is the best target to solve the two remaining challenges of the plate tectonics theory, i.e., subduction initiation and the driving force of plate tectonics. Recent studies proposed that the Izu-Bonin subduction initiation belongs to spontaneous initiation, which implies that it started from extension, followed by low angle subduction. Numerical geodynamic modeling suggests that the initiation of plate subduction likely occurred along a transform fault, which put the young spreading ridge in direct contact with old oceanic crust. This, however, does not explain the simultaneous subduction initiation in the west Pacific region in the Cenozoic. Namely, the subduction initiations in the Izu-Bonin- Mariana, the Aleutian, and the Tonga-Kermadec trenches are associated with oceanic crusts of different ages, yet they occurred at roughly the same time, suggesting that they were all triggered by a major change in the Pacific plate. Moreover, low angle subduction induces compression rather than extension, which requires external compression forces. Given that the famous Hawaiian-Emperor bending occurred roughly at the same time with the onset of westward subductions in the west Pacific, we propose that these Cenozoic subductions were initiated by the steering of the Pacific plate, which are classified as induced initiation. Induced subduction initiation usually occurs in young ocean basins, forming single-track subduction. The closures of Neo-Tethys Oceans were likely triggered by plumes in the south, forming northward subductions. Interestingly, the Indian plate kept on moving northward more than 50 Ma after the collision between the Indian and Eurasian continents and the break-off of the subducted oceanic slab attached to it. This strongly suggests that slab pull is not the main driving force of plate tectonics, whereas slab sliding is.
- Published
- 2020
46. Significant δ44/40Ca variations between carbonate- and clay-rich marine sediments from the Lesser Antilles forearc and implications for mantle heterogeneity
- Author
-
Fang Liu, Zhaofeng Zhang, Hongli Zhu, Xiao-Yun Nan, Xin Li, Weidong Sun, Yajun An, Fang Huang, and Long Du
- Subjects
010504 meteorology & atmospheric sciences ,Isotope ,Subduction ,Lithology ,Geochemistry ,Drilling ,010502 geochemistry & geophysics ,01 natural sciences ,Deep sea ,Mantle (geology) ,chemistry.chemical_compound ,chemistry ,Geochemistry and Petrology ,Carbonate ,Forearc ,Geology ,0105 earth and related environmental sciences - Abstract
Calcium isotopes can potentially be used to trace many geological processes. Characterizing the Ca isotopic compositions of marine sediments is a precondition for using Ca isotopes to trace the recycling of marine sediments into the mantle and mantle-derived rocks. The best way to achieve this goal is to investigate different types of marine sediments that are adjacent to subduction zones and would undergo subduction in the future. Here, we present high-precision Ca isotopic data for marine sediments from the Deep Sea Drilling Project (DSDP) Sites 543 and 144 along the Lesser Antilles forearc region, to constrain the Ca isotope signatures of marine sediments with various components and assess their possible effects on δ44/40Ca of the local mantle and arc lavas via subduction. Our results show that the δ44/40Ca values of these marine sediments vary from 0.10 to 1.21‰ and depend on lithology. Carbonate-rich sediments from Site 144 exhibit δ44/40Ca values in the range of 0.10–0.58‰ with a weighted average value of 0.36‰, which is ∼0.6‰ lower than that of the mantle. In comparison, δ44/40Ca of clay-rich sediments from Site 543 range from 0.79 to 1.21‰ with a mantle-like mean value of 0.96‰. The data obtained here suggest that carbonate- and clay-rich marine sediments differ significantly both in Ca isotopic compositions and CaO contents. Recycling of these sediments will result in different effects on the isotopic compositions of the local mantle and probably affect the local arc lavas. Specifically, carbonate-rich sediments from Site 144 with high CaO contents and light Ca isotopic compositions can alter the local mantle to lower δ44/40Ca signatures, which is expected in the southern Lesser Antilles arc lavas.
- Published
- 2020
47. Petrogenesis and tectonic implications of cambrian Nb-enriched I- and aluminous A-type granites in the North Qilian suture zone
- Author
-
Yuxiao Chen, Tangfu Xiao, Shuguang Song, Weidong Sun, Kai Wu, and Ying Cui
- Subjects
Subduction ,020209 energy ,Mantle metasomatism ,Geochemistry ,Geology ,02 engineering and technology ,010502 geochemistry & geophysics ,01 natural sciences ,Tectonics ,Continental margin ,0202 electrical engineering, electronic engineering, information engineering ,Suture (geology) ,0105 earth and related environmental sciences ,Petrogenesis - Abstract
Granitoids in active continental margins are probes of sub-arc magmatic processes and are crucial for the understanding of crust–mantle interaction during subduction. Here we report data for the mi...
- Published
- 2020
48. Calcium isotopic fractionation during plate subduction: Constraints from back-arc basin basalts
- Author
-
Zhaofeng Zhang, Xin Li, Weidong Sun, Long Du, and Hongli Zhu
- Subjects
010504 meteorology & atmospheric sciences ,Lau Basin ,Subduction ,Partial melting ,Geochemistry ,010502 geochemistry & geophysics ,01 natural sciences ,Mantle (geology) ,Geochemistry and Petrology ,Back-arc basin ,Slab ,Igneous differentiation ,Metasomatism ,Geology ,0105 earth and related environmental sciences - Abstract
Subduction related metasomatism has been proposed to be one of the most important processes that may cause Ca isotopic heterogeneities in the mantle. Back-arc basin basalts (BABBs) affected by different contributions of subducted materials have various geochemical compositions ranging from MORB-like to arc-like, so that they are ideal media to investigate the behavior of Ca isotopes during plate subduction. Here we report Ca isotopic compositions of a series of BABBs from the Lau Basin, Woodlark Basin and Coriolis Troughs in the southwestern Pacific. Our results show that δ44/40Ca of all the BABBs exhibit a narrow range of 0.73 ± 0.07 to 0.89 ± 0.06‰ with an average of 0.80 ± 0.08‰ (2SD, N = 21), which are lower than the estimated value of the Bulk Silicate Earth (BSE, 0.94 ± 0.05‰), but are similar to that of MORBs reported in the literature (0.83 ± 0.11‰, 2SD, N = 21). Even though the mantle sources of BABBs studied here have been influenced by various amounts of slab-derived fluids and/or sediments, there is no systematic variation of δ44/40Ca with indicators of subduction contributions (e.g., Ce/Pb, Nb/U, Ba/La, Th/Yb, 87Sr/86Sr and 143Nd/144Nd). This suggests that either there is no Ca isotopic discrepancy between subducted components and mantle, and/or the amount of Ca that is transferred from the subducting Pacific slab to the studied BABB mantle sources is insignificant. Water depths at which subducting sediments were deposited control the components of marine sediments that may be subducted, which in turn determine how subduction affects Ca isotopic composition of the mantle. Because the southwestern Pacific has deeper water depths than the carbonate compensation depth, pelagic clays dominate the contribution from the subducted slab rather than carbonates, which leads to the negligible Ca isotopic fractionation during subduction along these trenches. The lack of correlations of δ44/40Ca with geochemical indicators of magma differentiation (e.g., MgO, CaO/Al2O3, Sr/Nd, Eu/Eu*) suggests that intermediate-mafic magma differentiation has insignificant effects on Ca isotopic compositions of BABBs. Therefore, we conclude that the observed offset of δ44/40Ca (∼0.14‰) between the mantle and BABBs studied here should be primarily controlled by Ca isotopic fractionation during partial melting without significant contributions from subducted materials.
- Published
- 2020
49. High oxygen fugacity magma: implication for the destruction of the North China Craton
- Author
-
Ming-Xing Ling, Zhe-Kun Zhang, Weidong Sun, Sai-Jun Sun, and Lipeng Zhang
- Subjects
Craton ,geography ,geography.geographical_feature_category ,Subduction ,Mantle wedge ,Geochemistry and Petrology ,Lithosphere ,Magmatism ,Geochemistry ,Intraplate earthquake ,Mantle (geology) ,Geology ,Zircon - Abstract
The mechanism of lithospheric removal and destruction of the North China Craton (NCC) has been hotly debated for decades. It is now generally accepted that the subduction of the (Paleo)-Pacific plate played an important role in this process. However, how the plate subduction contributed to the craton destruction remains unclear. Here we report high oxygen fugacity (fO2) characteristics of the Yunmengshan granite, e.g., hematite–magnetite intergrowth supported by zircon Ce4+/Ce3+ ratios and apatite Mn oxygen fugacity indicator. High fO2 magmas are widely discovered in Late Mesozoic (160–130 Ma) adakitic rocks in central NCC. The origin of high fO2 magma is likely related to the input of the “oxidized mantle components”, which shows a close connection between plate subduction and destruction of the craton. The research area is ~ 1500 km away from the current Pacific subduction zone. Considering the back-arc extension of Japan Sea since the Cretaceous, this distance may be shortened to ~ 800 km, which is still too far for normal plate subduction. Ridge subduction is the best candidate that was responsible for the large scale magmatism and the destruction of the NCC. Massive slab-derived fluids and/or melts were liberated into an overlying mantle wedge and modified the lithospheric mantle. Rollback of the subducting plate induced the large-scale upwelling of asthenospheric mantle and triggered the formation of extensive high fO2 intraplate magmas.
- Published
- 2020
50. Investigation of an oceanic plateau formation and rifting initiation model implied by the Caroline Ridge on the Caroline Plate, western Pacific
- Author
-
Weidong Sun, Yongliang Bai, Dongdong Dong, Zhengyi Zhang, and Guangxu Zhang
- Subjects
Rift ,020209 energy ,Geology ,Oceanic plateau ,02 engineering and technology ,010502 geochemistry & geophysics ,01 natural sciences ,Seafloor spreading ,Paleontology ,Lithosphere ,Hotspot (geology) ,0202 electrical engineering, electronic engineering, information engineering ,0105 earth and related environmental sciences - Abstract
The rifting of oceanic plateaus is an important mechanism for initiating lithospheric break-up and subsequent seafloor spreading. In this study, we present the latest multichannel seismic data investigating the Caroline Ridge and provide one of the typical cases for initial oceanic plateau evolution. We reveal that a smooth basement reflector (R2), as the top of the lava flows, is subparallel to the sediments with horizontal seismic reflections over the surface of the Caroline Ridge. Thick layer-parallel lava flows beneath the R2 appear within the crust. Large seamounts in the Sorol Trough possess abundant saucer-shaped intracrustal reflectors, and the overlying sediments were destroyed by intrusive bodies. The overlying sedimentary sequences, basement, and thick lava flows on the Caroline Ridge flanks were faulted by opposing normal fault sets, and the eruptions of the seamounts deformed the strata. A widespread bright horizontal reflector (R1), as an unconformity inside the Caroline Ridge sediments, truncates the lower tilted sediment layers and is itself cut by normal faults in the flank strata. Furthermore, we propose that subaerial lava flows extended laterally from the hotspot magmatism localizing in the Sorol Trough and led to Caroline Ridge formation. The initial rifting of the Caroline Ridge occurred during the Early-Middle Miocene. Limited volcanoes concentrate only in the Sorol Trough due to the attenuated thermal effect. It is suggested that dome uplifting and far-field force could have jointly caused initial rifting process of the Caroline Ridge.
- Published
- 2020
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