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Generation of Nb-enriched mafic rocks and associated adakitic rocks from the southeastern Central Asian Orogenic Belt:Evidence of crust-mantle interaction

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Geoscience Frontiers 2022年第2期13卷 255-274页

作者： Yan Jing Wenchun Ge M.Santosh Yu Dong Hao Yang Zheng Ji Junhui Bi Hongying Zhou Dehe Xing College of Earth Sciences Jilin UniversityChangchun 130061China Key Laboratory of Mineral Resources Evaluation in Northeast Asia Ministry of Land and Resources of ChinaChangchun 130026China School of Earth Sciences and Resources China University of Geosciences BeijingBeijing 100083China Department of Earth Science University of AdelaideAustralia Tianjin Center China Geological SurveyTianjin 300170China Shenyang Center China Geological SurveyShenyang 110034China

melting of subducting oceanic lithosphere and associated melt-mantle interactions in convergent plate margins require specific geodynamic environment that allows the oceanic slab to be abnormally *** we focus on the Early Mesozoic mafic rocks and granite porphyry,which provide insights into slab melting processes associated with final closure of the Paleo-Asian *** granite porphyry samples are calc-alkaline and distinguished by high Sr contents,strong depletion of heavy rare earth elements,resulting in high(La/Yb);and Sr/Y ratios,and negligible Eu *** on their high Na_(2)O and Mg O,low K_(2)O contents,positiveε_(Hf)(t)andε_(Nd)(t)and low(^(87)Sr/^(86)Sr)ivalues,we propose that the granite porphyry was likely derived from partial melting of subducting Paleo-Asian oceanic *** Nb-enriched mafic rocks are enriched in Rb,Th,U,Pb and K,and depleted in Nb,Ta,Ba,P and Ti,corroborating a subduction-related *** heterogeneous Sr-Nd-Hf-O isotopic compositions and other geochemical features suggest that they were likely derived from partial melting of peridotitic mantle wedge interacted with oceanic slab-derived adakitic *** element and isotope modeling results and elevated zirconδ^(18)O values suggest variable subducting sediments input into the mantle wedge,dominated by terrigenous *** the widely-developed bimodal rock associations,conjugated dikes,thermal metamorphism,tectonic characteristics,paleomagnetic constraints,and paleogeographical evidence along the Solonke-Changchun suture zone,we identify a slab window triggered by slab break-off,which accounts for slab melting and formation of the Nb-enriched mafic rocks and associated adakitic granite porphyry in southeastern Central Asian Orogenic Belt.

关键词： Early-Middle Triassic Solonker-Changchun suture zone Nb-enriched mafic rocks Adakitic granite porphyry slab melting

Geological characteristics of the Nankai Trough subduction zone and their tectonic significances

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Acta Oceanologica Sinica 2020年第10期39卷 81-95页

作者： Jie Zhang Ling Chen Zihua Cheng Limei Tang Key Laboratory of Submarine Geosciences Ministry of Natural Resources/Second Institute of OceanographyMinistry of Natural ResourcesHangzhou 310012China Key Laboratory of Marine Mineral Resources Guangzhou Marine Geological SurveyMinistry of Natural ResourcesGuangzhou 510760China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519080China Key Laboratory of Ocean and Marginal Sea Geology South China Sea Institute of OceanologyChinese Academy of SciencesGuangzhou 510301China

The Nankai Trough subduction zone is a typical subduction system characterized by subduction of multiple geological units of the Philippine Sea Plate(the Kyushu-Palau Ridge,the Shikoku Basin,the Kinan Seamount Chain,and the Izu-Bonin Arc)beneath the Eurasian Plate in the southwest of *** study presents a geophysical and geochemical analysis of the Nankai Trough subduction zone in order to determine the features and subduction effects of each geological *** results show that the Nankai Trough is characterized by lowgravity anomalies(–20 mGal to–40 mGal)and high heat flow(60–200 mW/m2)in the middle part and low heat flow(20–80 mW/m2)in the western and eastern *** crust of the subducting plate is 5–20 km *** mantle composition of the subducting plate is progressively depleted from west to *** of aseismic ridges(e.g.,the Kyushu-Palau Ridge,the Kinan Seamount Chain,and the Zenisu Ridge)is a common process that leads to a series of subduction effects at the Nankai ***,aseismic ridge or seamount chain subduction may deform the overriding plate,resulting in irregular concave topography along the front edge of the accretionary ***,it may have served as a seismic barrier inhibiting rupture propagation in the 1944 Mw 8.1 and 1946 Mw 8.3 *** addition,subduction of the Kyushu-Palau Ridge and hot and young Shikoku Basin lithosphere may induce slab melting,resulting in adakitic magmatism and the provision of ore-forming metals for the formation of porphyry copper and gold deposits in the overriding Japan *** on comparisons of their geophysical and geochemical characteristics,we suggest that,although the Izu-Bonin Arc has already collided with the Japan Arc,the Kyushu-Palau Ridge,which represents a remnant arc of the Izu-Bonin Arc,is still at the subduction stage characterized by a single-vergence system and a topographic boundary with the Japan Arc.

关键词： Nankai Trough subduction zone velocity structure gravity modeling geochemistry petrology slab melting geological effect

Late Jurassic adakitic ore-bearing granodiorite porphyry intrusions in the Xiaokele porphyry Cu(–Mo)deposit,Northeast China:implications for petrogenesis and tectonic setting

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Acta Geochimica 2021年第5期40卷 702-717页

作者： Yonggang Sun Bile Li Zhonghai Zhao Qingfeng Ding Fanbo Meng Xusheng Chen Ye Qian Yujin Li College of Earth Sciences Jilin University2199 Jianshe StreetChangchun 130061China College of Mining Liaoning Technical UniversityFuxin 123000China Qiqihaer Institute of Geological Exploration Heilongjiang 161006China Key Laboratory of Mineral Resources Evaluation in Northeast Asia Ministry of Land and ResourcesChangchun 130061China

The Xiaokele Cu(–Mo)deposit is a recently discovered porphyry deposit in the northern Great Xing’an Range(GXR)of northeast *** ore bodies in this deposit are mainly hosted within granodiorite porphyry ***,phyllic,and propylitic alteration zones develop from center to *** this paper,we present zircon LA–ICP–MS U–Pb ages,zircon Hf isotopic compositions,and whole-rock geochemistry of the ore-bearing granodiorite porphyries from the Xiaokele Cu(–Mo)*** U–Pb dating suggests that the Xiaokele granodiorite porphyries were emplaced at 148.8±1.1 Ma(weighted-mean age;n=14).The Xiaokele granodiorite porphyries display high SiO2,Al2O3,Sr,and Sr/Y,low K2O/Na2O,MgO,Yb,and Y,belonging to high-SiO2 adakites produced by partial melting of the subducted oceanic *** sediments were involved in the magma source of the Xiaokele granodiorite porphyries,as indicated by enriched Sr–Nd isotopic compositions(eNd(-t)=-1.17–-0.27),low positive zircon eHf(t)values(0.4–2.2),and high Th contents(4.06–5.20).The adakitic magma subsequently interacted with the mantle peridotites during ascent through the mantle *** Xiaokele granodiorite porphyries were derived from slab melting during the southward subduction of the Mongol–Okhotsk Ocean.

关键词： Xiaokele porphyry Cu(–Mo)deposit Adakite slab melting Mongol–Okhotsk Ocean Northern Great Xing’an Range

Decoupling between Oxygen and Radiogenic Isotopes: Evidence for Generation of Juvenile Continental Crust by Partial melting of Subducted Oceanic Crust

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Journal of Earth Science 2021年第5期32卷 1212-1225页

作者： Xuan-Ce Wang Qiuli Li Simon A.Wilde Zheng-Xiang Li Chaofeng Li Kai Lei Shao-Jie Li Linlin Li Manoj K.Pandit School of Earth Sciences Yunnan UniversityKunming 650500China School of Earth Science and Resources Chang1 an UniversityXi'an 710054China State Key Laboratory of Lithospheric Evolution Institute of Geology and GeophysicsChinese Academy of SciencesBeijing 100029China ARC Centre of Excellence for Core to Crust Fluid Systems and The Institute for Geoscience Research Department of Applied GeologyCurtin UniversityPerth 6845Australia Department of Geology University of RajasthanJaipur 302004India

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 εHf(εHf(873 Ma)= +9.3 to +10.9) and whole-rock Nd(εNd(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 tonalitetrondhjemite-granodiorite suites.

关键词： zircon Hf-Nd and O isotopes decoupling slab melting Neoproterozoic continental crustal growth

Do Supercontinent-Superplume Cycles Control the Growth and Evolution of Continental Crust?

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Journal of Earth Science 2020年第10期31卷 1142-1169页

作者： Xuan-Ce Wang Simon A.Wilde Zheng-Xiang Li Shaojie Li Linlin Li School of Earth Sciences Yunnan UniversityKunming 650500China School of Earth Science and Resources Chang'an UniversityXi'an 710054China ARC Centre of Excellence for Core to Crust Fluid Systems(CCFS)and The Institute for Geoscience Research(TIGeR) Department of Applied GeologyCurtin UniversityPerth WA 6845Australia

The evolution of continental crust can be directly linked to the first-order supercontinent-superplume *** demonstrate that:(1)a mantle-like oxygen isotopic signature is not a diagnostic feature for distinguishing crustal addition from the reworking of pre-existing continental crust;(2)juvenile continental crust shows a wide range of whole-rock Hf isotopic compositions throughout Earth's history;and(3)detrital zircon Hf model ages cannot reliably determine the growth of continental ***,the wide use of zircon Hf model ages,based on zircon grains with mantle-like oxygen isotopes,is inappropriate for estimating the timing of continental crustal *** on an analysis of global Hf and O isotope and zircon age databases,we argue that the actual U-Pb crystallization ages of juvenile zircon grains provide the best opportunity to unravel crustal growth through time and to test its relationship with supercontinent-superplume ***,when the Hf isotopes of these juvenile grains plot within the field of juvenile continental crust,they correlate well with times of global mantle depletion as recorded by Os and He isotopes,plume activity as recorded by LIP events,and periods of crustal growth and the breakup of *** contrast,zircon grains crystallized from magmas that were produced by partial melting of pre-existing continental crust show U-Pb age peaks that correspond mainly to times of supercontinent assembly and crustal *** analysis shows the key role played by recycling of mafic crustal components in the generation of juvenile continental crust.

关键词： zircon age zircon Hf-O isotopes slab melting juvenile crust formation episodic continental crustal growth supercontinent-superplume cycles