The combination of U-Pb and Lu-Hf compositions measured in zircon crystals is a remarkably powerful isotopic couplet that provides measures on both the timing of mineral growth and the radiogenic enrichment of the sou...The combination of U-Pb and Lu-Hf compositions measured in zircon crystals is a remarkably powerful isotopic couplet that provides measures on both the timing of mineral growth and the radiogenic enrichment of the source from which the zircon grew.The U-Pb age documents the timing of zircon crystallization/recrystallization and Hf isotopes inform on the degree to which the host melt was derived from a radiogenic reservoir(e.g.depleted mantle) versus an unradiogenic reservoir(e.g.ancient continental crust),or some mixture of these sources.The ease of generating large quantities of zircon U-Pb and Lu-Hf data has been in large part facilitated by instrument advances.However,the dramatic increase in time constrained zircon Lu-Hf analyses in the Earth science community has brought to the fore the importance of careful data collection and reduction workflows,onto which robust geological interpretations may be based.In this work,we discuss the fundamentals of Lu-Hf isotopes in zircon,which then allows us to provide a robust,accessible,methodology for the assessment of data quality.Additionally,we discuss some novel techniques for:data visualization—that facilitates better transparency of data interpretation;integration of geographic information—that may reveal spatial trends where temporal trends were only apparent before;and some novel statistical evaluation tools—that may provide more rigorous interand intra-sample comparisons.展开更多
Detrital zircon U-Pb geochronology combined with Hf isotopic and trace element data from metasedimentary rocks of the Aracuai Belt in southeastern Brazil provide evidence for break-up of the Congo-Sao Francisco Craton...Detrital zircon U-Pb geochronology combined with Hf isotopic and trace element data from metasedimentary rocks of the Aracuai Belt in southeastern Brazil provide evidence for break-up of the Congo-Sao Francisco Craton. The U-Pb age spectra of detrital zircons from metasediments of the Rio Doce Group(RDG) range from 900-650 Ma and define a maximum depositional age of ca. 650 Ma. Zircon trace element and whole rock data constrain an oceanic island arc as source for the deposition setting of the protoliths to the metasediments. Zircon ε_(Hf)(t) values from these rocks are positive between +1 and +15, supporting previous evidence of a Neoproterozoic extensional phase and oceanic crust formation in a precursor basin to the Aracuai Belt. Recrystallization of detrital zircon at ca. 630 Ma is compatible with a regional metamorphic event associated with terrane accretion to the Paleoproterozoic basement after transition from an extensional to a convergent regime. The juvenile nature, age spectra and trace element composition recorded in detrital zircons of metasediments from the Aracuai Belt correspond with zircons from metasedimentary rocks and oceanic crust remnants of other orogenic belts to its south. This suggests that rifting and oceanic crust formation of the entire orogenic system, the so-called Mantiqueira Province, was contemporaneous, most likely related to the opening of a large ocean. It further indicates that the cratonic blocks involved in the orogenic evolution of the Mantiqueira Province were spatially connected as early as 900 Ma.展开更多
The Banshanping granitoid rocks distribute in the east of the North Qinling orogenic belt.It is a diorite-quartz diorite-granodiorite-granite series,spreading in a NW-SE direction,and intrudes into the Erlangping Grou...The Banshanping granitoid rocks distribute in the east of the North Qinling orogenic belt.It is a diorite-quartz diorite-granodiorite-granite series,spreading in a NW-SE direction,and intrudes into the Erlangping Group.The SiO2 content ranges from 57.04% to 76.56%,Na2O from 2.05% to 4.65%,K2O from 0.84% to 3.40%.Major element characteristics indicate that Banshanping granitoid rocks have properties of I type granotoids.SREE ranges from 36.51 ppm to 473.25 ppm,and LREE/ HREE ratios lie between 3.95 and 22.18.Negative Eu anomalies are not obvious in most samples,though there are obvious Nb,P and Ti positive anomalies.The zircon LA-ICP-MS ages of Banshangping granitoid rocks are 496.0±8.1 Ma-486.9±9.3 Ma.Hf isotope shows that 176Hf/177Hf ratios range from 0.282721 to 0.282876,εHf(t) values from 8.5 to 14,all positive,and corresponding modal ages (TDM2) range from 559 Ma to 908 Ma.Based on Hf isotope characteristics and existing SmNd and Rb-Sr isotope data,we consider that the Banshanping granitoid rocks originate from mantlederived material,i.e.the igneous rocks that formed in Neoproterozoic,and there may be a certain amount of crust-derived material during the formation of Banshanping granitoid rocks.展开更多
It is unclear whether the South China blocks have an affinity with continental Gondwana due to a lack of direct Pan-African magmatic and metamorphic features.In this study,we conducted U-Pb geochronological and Lu-Hf ...It is unclear whether the South China blocks have an affinity with continental Gondwana due to a lack of direct Pan-African magmatic and metamorphic features.In this study,we conducted U-Pb geochronological and Lu-Hf isotopic analyses for detrital zircons from a sandstone of the Chang'an Formation of the Nanhua Group in the Longsheng region of northern Guangxi,with the aim of constraining the timing of sedimentation and information as to its source,as well as seeking evidence for Pan-African events in the South China blocks.The results show that the ages of detrital zircons peaked at 654.7±6.2 Ma,773.2±4.1 Ma and 821.9±6.5 Ma,with some at 920–870 Ma;the youngest age indicates the existence of the Pan-African thermal event.The ε_(Hf)(t)and T_(DM2) values demonstrate that the study area has experienced three stages of crustal growth at 3.0–2.4 Ga,2.1–1.5 Ga and 1.3–0.9 Ga.With intensively distributed Neoproterozoic mafic-ultramafic and granitic plutons emplaced at 830–810 Ma along the southwestern section of the Jiangnan Orogenic Belt and positiveεHf(t)values from a large group of zircon grains,it is proposed that the sediments of the Chang'an Formation(of Nanhua Group)were largely sourced from the southeastern margin of the Yangtze block.Comparison with the zircon age spectra of the Cathaysian block shows that about 79%of the Pan-African aged detrital zircon grains that have TDM2=1352–1031 Ma andεHf(t)=3.68–8.79,were sourced from the recycled Grenvillian crust of the Cathaysian block,suggesting that the Cathaysian block had a close connection with Gondwana.展开更多
The in situ zircon U-Pb-Lu-Hf isotope records from end-Permian volcanic interlayers in southwest China,integrated with previous studies,restructure the evolutionary history of the Yangtze Craton from Precambrian to La...The in situ zircon U-Pb-Lu-Hf isotope records from end-Permian volcanic interlayers in southwest China,integrated with previous studies,restructure the evolutionary history of the Yangtze Craton from Precambrian to Late Paleozoic.This includes early continental crust formation before 3.0 Ga and massive juvenile crustal growth at 2.6-2.4 Ga;large-scale crustal reworking at 2.1-1.7 Ga;Neoproterozoic crust addition at 1.1 to 0.7 Ga;collision and subduction along the craton margin between 700-541 Ma;Early Ordovician to Late Silurian magmatism;and large tectono-thermal events in the Middle Carboniferous to end-Permian.Some zircons with T(MD2)ages from 4.40 to 4.01 Ga and lower initial176Hf/177Hf values of 0.280592 to 0.280726 may imply the existence of Hadean crust relics beneath the Yangtze Craton and their provenances could be associated with Hadean crustal remelting.This study further clarifies that the Precambrian-age zircons between the end-Permian volcanic interlayers,the complexes in the western margin of the Yangtze Craton,and the sedimentary Kangdian Basin,may share an affinity based on similar U-Pb age spectra and Hf isotope features.It also shows that the Neoproterozoic tectono-thermal event may be associated with large-scale tectono-rifting activity,which is different from the Grenville-age continental collision between Yangtze and Cathaysia blocks in South China.The above findings support the inference of a widespread Archean basement extending to the western Yangtze Craton and a provenance in the Kangdian Basin that is derived from the weathering and erosion of Paleoproterozoic continental crust.展开更多
In situ zircon U-Pb geochronological and Lu-Hf isotope studies of detrital zircons from Late Mesoproterozoic to Early Neoproterozoic sedimentary units on the southwestern margin of the Yangtze Block have important imp...In situ zircon U-Pb geochronological and Lu-Hf isotope studies of detrital zircons from Late Mesoproterozoic to Early Neoproterozoic sedimentary units on the southwestern margin of the Yangtze Block have important implications for the tectonic evolution of the Yangtze Block.The Huili Group contains zircons whose ages are mainly Late Archean to Mesoproterozoic(2650-2450,2100-1800,and 1350-1150 Ma).The Dengxiangying Group has one major age population of 1900-1600 Ma,and two subordinate age populations of 1350-1100 and 2300-2000 Ma.Yanbian Group sedimentary rocks have a zircon age population mainly in the range of 970-850 Ma,contemporaneous with the ages of widespread arc-related magmatism in the western Yangtze Block.Combining these results with previous work,the Huili and Dengxiangying groups were most likely deposited during ca.1160 to 1000 Ma in an intra-continental rift basin setting,while the Yanbian Group accumulated during>920 to 782 Ma in a back-arc basin setting at the southwestern margin of the Yangtze Block.In addition,all these results further suggest a tectonic transition from a continental rift basin to a convergent environment at the southwestern margin of the Yangtze Block at 1000-970 Ma.展开更多
The East Kunlun Orogenic Belt(EKOB) provides an important link to reconstruct the evolution of the Proto-Tethys and Paleo-Tethys realm. The EKOB is marked by widespread Early Paleozoic magmatism.Here we report the pet...The East Kunlun Orogenic Belt(EKOB) provides an important link to reconstruct the evolution of the Proto-Tethys and Paleo-Tethys realm. The EKOB is marked by widespread Early Paleozoic magmatism.Here we report the petrology, bulk geochemistry, zircon Ue Pb dating and, Lue Hf and SreN d isotopic data of the Early Paleozoic granitic rocks in Zhiyu area of the southern EKOB. Based on the zircon U-Pb dating, these granitoids, consisting of diorite, granodiorite and monzogranite, were formed during 450 -430 Ma the Late Ordovician to Middle Silurian. The diorite and granodiorite are high Sr/Y ratio as adakitic affinities, and the monzogranite belongs to highly fractionated I-type. Their(^(87)Sr/^(86)Sr)ivalues range from 0.7059 to 0.7085, εNd(t) values from -1.6 to -6.0 and the zircon εHf(t) values show large variations from +9.1 to -8.6 with Hf model ages(T_(DM2)) about 848 Ma and 1970 Ma. The large variations of whole-rock Nd and zircon Hf isotopes demonstrate strong isotopic heterogeneity of the source regions which probably resulted from multi-phase underplating of mantle-derived magmas. Geochemical and isotopic studies proved that the diorite and granodiorite had been derived from partial melting of heterogeneous crustal source with variable contributions from ancient continental crust and juvenile components, and the monzogranites were representing fractional crystallization and crustal contamination for arc magma. The Early Paleozoic adakitic rocks and high-K calc-alkaline granitoids in the southern EKOB were likely emplaced in a continental marginal arc setting possibly linked to the southwards subduction of the Paleo Kunlun Ocean and the magma generation is linked to partial melting of thickened continental crust induced by underplating of mantle-derived magmas.展开更多
On the southwestern margin of the Yangtze Block, the Dongchuan Group consists of slightly metamorphosed sedimentary rocks, including silty slate, argillaceous slate, clayey slate, arkose, dolomite, and minor volcanic ...On the southwestern margin of the Yangtze Block, the Dongchuan Group consists of slightly metamorphosed sedimentary rocks, including silty slate, argillaceous slate, clayey slate, arkose, dolomite, and minor volcanic rocks. To date, it is still a controversy over the depositional age and stratigraphic sequence of the Dongchuan Group. In this study, we analyzed five samples of meta-sedimentary rocks and one sample of meta-tuff from the Yinmin, Luoxue and Etouchang Formations of the Dongchuan Group in the Yuxi region for detrital zircon U-Pb ages and Lu-Hf isotope. The detrital zircon ages of the meta-sediments vary from 3073 to 1703 Ma, mainly clustered at three periods, from 1889 to 1840, 2490 to 2008 and 2878 to 2844 Ma. The youngest age peak of all the samples is ~1859 Ma, with the εHf(t) values of the zircons ranging from-20.3 to +4.3 and more than 90% being negative, indicating that the Paleoproterozoic crustal accretion on the southwestern margin of the Yangtze Block was dominated by reworking of the ancient crustal materials involved in the assembly and breakup of the Columbia supercontinent. Another important age range is between 2490 Ma and 2008 Ma, with εHf(t) values from-14.7 to +8.9 and 70% of them are negative, suggesting that the magmatism in the source area was also dominated by reworking and recycling of the ancient crustal materials, with minor juvenile mantle substances added. The detritus was probably derived from the Paleoproterozoic crystalline basement in the southern Yuxi region. The oldest peak age is ~2847 Ma and the εHf(t) values are from-7.7 to +7.0 with 50% of both positive and negative values, demonstrating a possible ~2.85 Ga ancient continental nucleus on the southwestern margin of the Yangtze Block and substantial growth in juvenile crust materials during this period. Besides, the weighted average age of the zircons from the meta-tuff of the Etouchang Formation is 1677 ± 14 Ma. Combining the previous research data and this study, we can constrain the depositional age of the Dongchuan Group in central Yunnan Province to the period from the late Paleoproterozoic to early Mesoproterozoic, slightly earlier than that of the Dongchuan Group in the Dongchuan area near to the southwestern Sichuan Province. The depositional age of the Dongchuan Group is older than that of the Kunyang Group.展开更多
The Mianning-Dechang (MD) rare earth element (REE) belt, located in the northern Kangdian axis (KDA) in the western margin of the Yangtze platform, is one of the most economically significant REE mineral belts i...The Mianning-Dechang (MD) rare earth element (REE) belt, located in the northern Kangdian axis (KDA) in the western margin of the Yangtze platform, is one of the most economically significant REE mineral belts in China. REE mineralization is associated with Himalayan carbonatite- alkaline complexes. The Lizhuang nordmarkite occurred in the northern part of the MD REE belt. The majority of zircons from the Lizhuang nordmarkite are characterized by pronounced positive Ce yet slightly negative Eu anomalies and high U/Yb. Moreover, all zircons have stable Hf isotopic compositions with initial 176Hf/177Hf ratios ranging from 0.282739 to 0.282808 and an average value of 0.282773. The negative Lu/Hf and positive till(t) range from -0.98 to -0.94 (average value of -0.96) and from -0.56 to 1.89 (the majority is positive, with an average of 0.66), respectively. These characteristics indicate that the rock is derived from an enriched mantle and subducted material. LA-ICP-MS analysis of the zircons from the intrusion yields a weighted mean 2~6pb/23SU age of 28.57~0.61Ma. During this period, the tectonic activity in the KDA is not plate subduction but an intraplate tectonic exhibiting fold-thrust and strike-slip behaviors in the western marginal zone of the Yangtze platform (WMYB). We suggest the possibility of an existing eastward old slab subduction under WMYB combined with a regional tectonic evolution. The Lizhuang nordmarkite may be derived from an enriched mantle beneath the western part of the Yangtze craton, which originated from the remelting of the Tethys subducting slab, because of the Himalayan strike-slip that formed a special type of REE deposit called strike-slip-type REE deposits.展开更多
The Neoproterozoic evolution of the Jiangnan Orogen is important for understanding the tectonic history of South China.As a volcanic-sedimentary sequence developed in the Nanhua rift,the Banxi Group preserves the reco...The Neoproterozoic evolution of the Jiangnan Orogen is important for understanding the tectonic history of South China.As a volcanic-sedimentary sequence developed in the Nanhua rift,the Banxi Group preserves the records of important magmatic and tectonic events linked to the assembly and breakup of the Rodinia supercontinent.In this study,we report the results from whole-rock major-and trace-element concentrations,with zircon LA-(MC)-ICP-MS U-Pb ages,trace elements and Lu-Hf isotopic compositions of sandstones from the Banxi Group.The rocks are characterized by high SiO_(2)(65.88%–82.76%,with an average of 75.50%)contents,moderate(Fe_(2)O_(3)^(T)+MgO)(1.81%–7.78%,mean:3.79%)and TiO_(2)(0.39%–0.54%,mean:0.48%),low K_(2)O/Na_(2)O(0.03–0.40,mean:0.10)ratios and low Al_2O_(3)/SiO_(2)(0.11–0.24,mean:0.15)ratios.The sandstones have highΣREE contents(mean:179.1 ppm),with chondrite-normalized REE patterns similar to the upper crust and PAAS,showing enriched LREE((La/Yb)_N mean:14.85),sub-horizontal HREE curves and mild Eu(Eu/Eu^(*):0.75–0.89,mean:0.81)negative anomalies.Their geochemical characteristics resemble those of passive continental margin sandstones.Most of the zircons are magmatic in origin and yield a U-Pb age distribution with three peaks:a major age peak at 805 Ma and two subordinate age peaks at 1990 Ma and 2470 Ma,implying three major magmatic sources.The Neoproterozoic zircons haveε_(Hf)(t)values ranging from-47.4 to 12.4(mostly-20 to 0),suggesting a mixture of some juvenile arc-derived material and middle Paleoproterozoic heterogeneous crustal sources.The Hf model ages of middle Paleoproterozoic zircons(~1990 Ma)with negativeε_(Hf)(t)values(-12.65 to-6.21,Ave.=-9.8)concentrated around the Meso-Paleoarchean(mean T_(DM)^(C)=3.3–3.1 Ga).For late Neoarchean detrital zircons(~2470 Ma),ε_(Hf)(t)values are divided into two groups,one with negative values(-9.16 to-0.6)with model ages of 3.5–2.9 Ga,the other featuring positive values(1.0 to 3.9)with model ages of 2.9–2.7 Ga,recording a crustal growth event at~2.5 Ga.Neoproterozoic zircons show volcanic arc affinities with partly intraplate magmatic features.We propose that the Banxi Group formed in a rift basin within a passive continental margin setting,which derived detritus from felsic to intermediate rocks from the Yangtze Block and a small amount of arc volcanic rocks.The middle Paleoproterozoic detrital zircon data suggest Columbia-aged basement lies beneath the western Jiangnan orogen.展开更多
Radiogenic isotopic dating and Lu–Hf isotopic composition using laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS)of the Wude basalt in Yunnan province from the Emeishan large igneous province(ELI...Radiogenic isotopic dating and Lu–Hf isotopic composition using laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS)of the Wude basalt in Yunnan province from the Emeishan large igneous province(ELIP)yielded timing of formation and post-eruption tectonothermal event.Holistic lithogeochemistry and elements mapping of basaltic rocks were further reevaluated to provide insights into crustal contamination and formation of the ELIP.A zircon U–Pb age of 251.3±2.0 Ma of the Wude basalt recorded the youngest volcanic eruption event and was consistent with the age span of 251-263 Ma for the emplacement of the ELIP.Such zircons hadε_(Hf)(t)values ranging from7.3 to+2.2,identical to those of magmatic zircons from the intrusive rocks of the ELIP,suggesting that crust-mantle interaction occurred during magmatic emplacement,or crust-mantle mixing existed in the deep source region prior to deep melting.The apatite U–Pb age at 53.6±3.4 Ma recorded an early Eocene magmatic superimposition of a regional tectonothermal event,corresponding to the Indian–Eurasian plate collision.Negative Nb,Ta,Ti and P anomalies of the Emeishan basalt may reflect crustal contamination.The uneven Nb/La and Th/Ta values distribution throughout the ELIP supported a mantle plume model origin.Therefore,the ELIP was formed as a result of a mantle plume which was later superimposed by a regional tectonothermal event attributed to the Indian–Eurasian plate collision during early Eocene.展开更多
In order to understand the petrogenesis and tectonic setting of diorite and diabase units on Doumer Island, Antarctic Peninsula, this paper reports new laser ablation-inductively coupled plasma-mass spectrometry(LA-IC...In order to understand the petrogenesis and tectonic setting of diorite and diabase units on Doumer Island, Antarctic Peninsula, this paper reports new laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS) zircon U-Pb, geochemical, and Lu-Hf isotopic data for the magmatism. The diorite and diabase samples yielded zircon U-Pb ages of 55.4 ± 0.3 and 52.8 ± 0.4 Ma, respectively. These samples are enriched in the large ion lithophile elements and the light rare earth elements, and are depleted in the high field strength elements. The zircons in these samples yield eHf(t) values from 9.03 to 11.87 and model ages(TDM2) of 342–524 Ma. The major, trace, rare earth element(REE), and Hf isotopic data for the diorites indicate that these units were formed by the mixing of magmas generated by(a) the partial melting of mantle wedge material that experienced fluid-metasomatism in a subduction zone setting, and(b) the melting of juvenile crustal material induced by the upwelling of mantle-derived magmas in a subduction–collision setting. The diabase units contain higher total REE concentrations than the diorite, indicating they were derived from a different source region. These samples also have higher Mg~# values and contain lower concentrations of Cr and Ni than the diorites, and have weakly negative Nb and Ta anomalies with Nb/Ta values of <3. The zircons in these samples yield eHf(t) values from 9.08 to 11.11 and model ages(TDM2) of 389–503 Ma. The major, trace, REE, and Hf isotopic compositions of the diabase units indicate that that they were derived from the mixing of depleted mantle-derived magmas with magmas generated by the melting of juvenile crustal material which was induced by the upwelling of the mantle into the crust. Overall the Cenozoic diorite and diabase on Doumer Island is related to subduction environment.展开更多
The Hongseong area of the Hongseong-Imjingang Belt in the central-western Korean Peninsula forms part of a subduction-collision system that is correlated with the Qinling-Dabie-Sulu Belt in China. Several serpentinize...The Hongseong area of the Hongseong-Imjingang Belt in the central-western Korean Peninsula forms part of a subduction-collision system that is correlated with the Qinling-Dabie-Sulu Belt in China. Several serpentinized ultramafic bodies carrying blocks of metamorphosed mafic rocks occur in this area. Here we investigate zircon grains in serpentinites from Bibong(BB) and Wonnojeon(WNJ), and high-pressure(HP) mafic granulite from Baekdong(BD) localities based on U-Pb, REE and Lu-Hf analyses. The zircons from BD HP mafic granulite show distinct age peaks at 838 Ma, 617 Ma and 410 Ma, with minor peaks at1867 Ma, 1326 Ma and 167 Ma. The Neoproterozoic age peaks in these rocks as well as in the serpentinites suggest subduction-related melt-fluid interaction in the mantle wedge at this time. The older zircon grains ranging in age from the Early to Middle Paleoproterozoic might represent detrital grains from the basement rocks transferred to the wedge mantle through sediment subduction. The BD HP mafic granulite shows a Middle Paleozoic age peak(Devonian; 410 Ma). The 242-245 Ma age peaks in the compiled age data of zircon grains serpentinites from BB and WNJ correspond to a major Triassic event that further added melts and fluids into the ancient mantle wedge to crystallize new zircons. In the chondrite normalized rare earth element diagram, the magmatic zircon grains from the studied rocks show LREE depletion and HREE enrichment with sharply negative Eu and Pr anomalies and positive Ce and Sm anomalies. The REE patterns of hydrothermal zircons show LREE enrichment, and relatively flat patterns with negative Eu anomaly. Zircon Hf signature from the WNJ serpentinite show negative εHf(t)(-18.5 and-23.5) values indicating an enriched mantle source with TDM in the range of 1614 Ma and1862 Ma. Zircons from the BD HP mafic granulite also show slightly negative εHf(t)(average-4.3) and TDM in the range of 1365-1935 Ma. Our study provides evidence for multiple zircon growth in an evolving mantle wedge that witnessed melt and fluid interaction during different orogenic cycles.展开更多
The Sulu Orogen preserves the Neoproterozoic tectonic-magmatic events,corresponding to the breaking up of the Rodinia supercontinent.The ages and petrogenesis of meta-igneous rocks in the Liansandao area in the northe...The Sulu Orogen preserves the Neoproterozoic tectonic-magmatic events,corresponding to the breaking up of the Rodinia supercontinent.The ages and petrogenesis of meta-igneous rocks in the Liansandao area in the northern Sulu Orogen are not well-constrained.This study reports zircon U-Pb ages and Hf isotopes of these rocks from the Liansandao area.Three meta-igneous rock samples give similar weighted mean 206 Pb/238 U ages of 744±11,767±12,and 762±15 Ma,respectively,indicating the Neoproterozoic crystallization ages.These rocks formed coevally with the Wulian and Yangkou intrusions that located along the Yantai-Qingdao-Wulian fault zone.The Neoproterozoic ages indicate that the meta-igneous rocks from the Liansandao area have affinity to the Yangtze Block.The three samples haveεHf(t)values of-7.2–-10.5,-6.0–-17.5,and-6.8–-12.0,respectively.These negativeεHf(t)values indicate a primarily crustal source.However,the widely variousεHf(t)values that are higher than the continental crust,suggesting magma mixing between mantle-derived materials and the continental crust or source heterogeneity.Combined with the Hf model ages and geochemical characteristics,the monzodiorite(sample LSD-2)is most likely to be mantle-derived magma then interacted with ancient continental crust,and the granitic protolith(samples LSD-1 and LSD-3)in the Liansandao area might derive from the re-melting of a Paleoproterozoic continental crust at^750 Ma,resulting from the upwelling and underplating of mantle-derived magma formed in an extensional setting due to the break-up of the Rodinia supercontinent.展开更多
The Wuliangshan Group occurs to the east of the Lancang giant igneous zone in SW Yunnan, and is mainly composed of low-grade metamorphosed sedimentary rocks. The group has been considered as the syn-orogenic product o...The Wuliangshan Group occurs to the east of the Lancang giant igneous zone in SW Yunnan, and is mainly composed of low-grade metamorphosed sedimentary rocks. The group has been considered as the syn-orogenic product of the Baoshan with Simao-Indochina blocks. However, its depositional time and provenance remain to be poorly constrained. This paper presents zircon U-Pb dating and Lu-Hf-isotopic data for five representative sandstone samples from the Wuliangshan Group. The detrital grains yield a major age-peak at ~259 Ma, and four subordinary age-peaks at ~1 859, ~941, ~788, and ~447 Ma, respectively. Our results suggest that the Wuliangshan metasedimentary sequence was deposited after Middle Triassic rather than previously-thought Cambrian. The detrital zircon age spectrum, along with in-situ Lu-Hf isotopic data suggest that the Wuliangshan Group might be a syncollisional sedimentary product related to the collision of Baoshan with Simao-Indochina blocks. It is inferred that the provenance of the Wuliangshan Group is mainly from the Simao/Yangtze blocks to the east rather than the Baoshan Block or Lancang igneous zone to the west.展开更多
基金funded via an Australian Geophysical Observing System grant providedfunding from the Australian Research Council LIEF program(LE150100013)。
文摘The combination of U-Pb and Lu-Hf compositions measured in zircon crystals is a remarkably powerful isotopic couplet that provides measures on both the timing of mineral growth and the radiogenic enrichment of the source from which the zircon grew.The U-Pb age documents the timing of zircon crystallization/recrystallization and Hf isotopes inform on the degree to which the host melt was derived from a radiogenic reservoir(e.g.depleted mantle) versus an unradiogenic reservoir(e.g.ancient continental crust),or some mixture of these sources.The ease of generating large quantities of zircon U-Pb and Lu-Hf data has been in large part facilitated by instrument advances.However,the dramatic increase in time constrained zircon Lu-Hf analyses in the Earth science community has brought to the fore the importance of careful data collection and reduction workflows,onto which robust geological interpretations may be based.In this work,we discuss the fundamentals of Lu-Hf isotopes in zircon,which then allows us to provide a robust,accessible,methodology for the assessment of data quality.Additionally,we discuss some novel techniques for:data visualization—that facilitates better transparency of data interpretation;integration of geographic information—that may reveal spatial trends where temporal trends were only apparent before;and some novel statistical evaluation tools—that may provide more rigorous interand intra-sample comparisons.
基金funding from CNPq(401334/2012-0-302058/2015-0-402852/2012-5)FAPEMIG(APQ03943-RPQ-0067-10-RDP00063-10)grants
文摘Detrital zircon U-Pb geochronology combined with Hf isotopic and trace element data from metasedimentary rocks of the Aracuai Belt in southeastern Brazil provide evidence for break-up of the Congo-Sao Francisco Craton. The U-Pb age spectra of detrital zircons from metasediments of the Rio Doce Group(RDG) range from 900-650 Ma and define a maximum depositional age of ca. 650 Ma. Zircon trace element and whole rock data constrain an oceanic island arc as source for the deposition setting of the protoliths to the metasediments. Zircon ε_(Hf)(t) values from these rocks are positive between +1 and +15, supporting previous evidence of a Neoproterozoic extensional phase and oceanic crust formation in a precursor basin to the Aracuai Belt. Recrystallization of detrital zircon at ca. 630 Ma is compatible with a regional metamorphic event associated with terrane accretion to the Paleoproterozoic basement after transition from an extensional to a convergent regime. The juvenile nature, age spectra and trace element composition recorded in detrital zircons of metasediments from the Aracuai Belt correspond with zircons from metasedimentary rocks and oceanic crust remnants of other orogenic belts to its south. This suggests that rifting and oceanic crust formation of the entire orogenic system, the so-called Mantiqueira Province, was contemporaneous, most likely related to the opening of a large ocean. It further indicates that the cratonic blocks involved in the orogenic evolution of the Mantiqueira Province were spatially connected as early as 900 Ma.
基金granted by China Geological Survey Projects (1212011120160, 1212010918007, 1212010818090, 1212010611803, 1212010711816)Special Project of Deep Exploration and Experimental Study–Pre-study of Scientific Drilling in Mineralized Cluster Area in Eastern China (SinoProbe-05-05)National Science Foundation Project (40921001, 49772106,40472034,40672049)
文摘The Banshanping granitoid rocks distribute in the east of the North Qinling orogenic belt.It is a diorite-quartz diorite-granodiorite-granite series,spreading in a NW-SE direction,and intrudes into the Erlangping Group.The SiO2 content ranges from 57.04% to 76.56%,Na2O from 2.05% to 4.65%,K2O from 0.84% to 3.40%.Major element characteristics indicate that Banshanping granitoid rocks have properties of I type granotoids.SREE ranges from 36.51 ppm to 473.25 ppm,and LREE/ HREE ratios lie between 3.95 and 22.18.Negative Eu anomalies are not obvious in most samples,though there are obvious Nb,P and Ti positive anomalies.The zircon LA-ICP-MS ages of Banshangping granitoid rocks are 496.0±8.1 Ma-486.9±9.3 Ma.Hf isotope shows that 176Hf/177Hf ratios range from 0.282721 to 0.282876,εHf(t) values from 8.5 to 14,all positive,and corresponding modal ages (TDM2) range from 559 Ma to 908 Ma.Based on Hf isotope characteristics and existing SmNd and Rb-Sr isotope data,we consider that the Banshanping granitoid rocks originate from mantlederived material,i.e.the igneous rocks that formed in Neoproterozoic,and there may be a certain amount of crust-derived material during the formation of Banshanping granitoid rocks.
基金This project was funded by the Chinese National Natural Science Foundation(Grants#41572191 and 42072259)the Guangxi Natural Science Foundation(Grants 2017GXNSFBA198166,2018GXNSFAA281248,2018GXNSFFA281009 and 2019GXNSFDA245009).
文摘It is unclear whether the South China blocks have an affinity with continental Gondwana due to a lack of direct Pan-African magmatic and metamorphic features.In this study,we conducted U-Pb geochronological and Lu-Hf isotopic analyses for detrital zircons from a sandstone of the Chang'an Formation of the Nanhua Group in the Longsheng region of northern Guangxi,with the aim of constraining the timing of sedimentation and information as to its source,as well as seeking evidence for Pan-African events in the South China blocks.The results show that the ages of detrital zircons peaked at 654.7±6.2 Ma,773.2±4.1 Ma and 821.9±6.5 Ma,with some at 920–870 Ma;the youngest age indicates the existence of the Pan-African thermal event.The ε_(Hf)(t)and T_(DM2) values demonstrate that the study area has experienced three stages of crustal growth at 3.0–2.4 Ga,2.1–1.5 Ga and 1.3–0.9 Ga.With intensively distributed Neoproterozoic mafic-ultramafic and granitic plutons emplaced at 830–810 Ma along the southwestern section of the Jiangnan Orogenic Belt and positiveεHf(t)values from a large group of zircon grains,it is proposed that the sediments of the Chang'an Formation(of Nanhua Group)were largely sourced from the southeastern margin of the Yangtze block.Comparison with the zircon age spectra of the Cathaysian block shows that about 79%of the Pan-African aged detrital zircon grains that have TDM2=1352–1031 Ma andεHf(t)=3.68–8.79,were sourced from the recycled Grenvillian crust of the Cathaysian block,suggesting that the Cathaysian block had a close connection with Gondwana.
基金supported by the National Natural Science Foundation of China(Grant Nos.40739903 and 41872137)。
文摘The in situ zircon U-Pb-Lu-Hf isotope records from end-Permian volcanic interlayers in southwest China,integrated with previous studies,restructure the evolutionary history of the Yangtze Craton from Precambrian to Late Paleozoic.This includes early continental crust formation before 3.0 Ga and massive juvenile crustal growth at 2.6-2.4 Ga;large-scale crustal reworking at 2.1-1.7 Ga;Neoproterozoic crust addition at 1.1 to 0.7 Ga;collision and subduction along the craton margin between 700-541 Ma;Early Ordovician to Late Silurian magmatism;and large tectono-thermal events in the Middle Carboniferous to end-Permian.Some zircons with T(MD2)ages from 4.40 to 4.01 Ga and lower initial176Hf/177Hf values of 0.280592 to 0.280726 may imply the existence of Hadean crust relics beneath the Yangtze Craton and their provenances could be associated with Hadean crustal remelting.This study further clarifies that the Precambrian-age zircons between the end-Permian volcanic interlayers,the complexes in the western margin of the Yangtze Craton,and the sedimentary Kangdian Basin,may share an affinity based on similar U-Pb age spectra and Hf isotope features.It also shows that the Neoproterozoic tectono-thermal event may be associated with large-scale tectono-rifting activity,which is different from the Grenville-age continental collision between Yangtze and Cathaysia blocks in South China.The above findings support the inference of a widespread Archean basement extending to the western Yangtze Craton and a provenance in the Kangdian Basin that is derived from the weathering and erosion of Paleoproterozoic continental crust.
基金financially supported by the China Geological Survey(Nos.DD20190370 and 121201111120117).
文摘In situ zircon U-Pb geochronological and Lu-Hf isotope studies of detrital zircons from Late Mesoproterozoic to Early Neoproterozoic sedimentary units on the southwestern margin of the Yangtze Block have important implications for the tectonic evolution of the Yangtze Block.The Huili Group contains zircons whose ages are mainly Late Archean to Mesoproterozoic(2650-2450,2100-1800,and 1350-1150 Ma).The Dengxiangying Group has one major age population of 1900-1600 Ma,and two subordinate age populations of 1350-1100 and 2300-2000 Ma.Yanbian Group sedimentary rocks have a zircon age population mainly in the range of 970-850 Ma,contemporaneous with the ages of widespread arc-related magmatism in the western Yangtze Block.Combining these results with previous work,the Huili and Dengxiangying groups were most likely deposited during ca.1160 to 1000 Ma in an intra-continental rift basin setting,while the Yanbian Group accumulated during>920 to 782 Ma in a back-arc basin setting at the southwestern margin of the Yangtze Block.In addition,all these results further suggest a tectonic transition from a continental rift basin to a convergent environment at the southwestern margin of the Yangtze Block at 1000-970 Ma.
基金financially sponsored by The National Key Research and Development Program of China (Grant No. 2016YFC0600502)the Program of the China Geological Survey (Grant Nos. 1212011121260, 1212011220920)111 Project (B07011)
文摘The East Kunlun Orogenic Belt(EKOB) provides an important link to reconstruct the evolution of the Proto-Tethys and Paleo-Tethys realm. The EKOB is marked by widespread Early Paleozoic magmatism.Here we report the petrology, bulk geochemistry, zircon Ue Pb dating and, Lue Hf and SreN d isotopic data of the Early Paleozoic granitic rocks in Zhiyu area of the southern EKOB. Based on the zircon U-Pb dating, these granitoids, consisting of diorite, granodiorite and monzogranite, were formed during 450 -430 Ma the Late Ordovician to Middle Silurian. The diorite and granodiorite are high Sr/Y ratio as adakitic affinities, and the monzogranite belongs to highly fractionated I-type. Their(^(87)Sr/^(86)Sr)ivalues range from 0.7059 to 0.7085, εNd(t) values from -1.6 to -6.0 and the zircon εHf(t) values show large variations from +9.1 to -8.6 with Hf model ages(T_(DM2)) about 848 Ma and 1970 Ma. The large variations of whole-rock Nd and zircon Hf isotopes demonstrate strong isotopic heterogeneity of the source regions which probably resulted from multi-phase underplating of mantle-derived magmas. Geochemical and isotopic studies proved that the diorite and granodiorite had been derived from partial melting of heterogeneous crustal source with variable contributions from ancient continental crust and juvenile components, and the monzogranites were representing fractional crystallization and crustal contamination for arc magma. The Early Paleozoic adakitic rocks and high-K calc-alkaline granitoids in the southern EKOB were likely emplaced in a continental marginal arc setting possibly linked to the southwards subduction of the Paleo Kunlun Ocean and the magma generation is linked to partial melting of thickened continental crust induced by underplating of mantle-derived magmas.
基金financially supported by the Geological Survey Project of the China Geological Survey(DD20190370)。
文摘On the southwestern margin of the Yangtze Block, the Dongchuan Group consists of slightly metamorphosed sedimentary rocks, including silty slate, argillaceous slate, clayey slate, arkose, dolomite, and minor volcanic rocks. To date, it is still a controversy over the depositional age and stratigraphic sequence of the Dongchuan Group. In this study, we analyzed five samples of meta-sedimentary rocks and one sample of meta-tuff from the Yinmin, Luoxue and Etouchang Formations of the Dongchuan Group in the Yuxi region for detrital zircon U-Pb ages and Lu-Hf isotope. The detrital zircon ages of the meta-sediments vary from 3073 to 1703 Ma, mainly clustered at three periods, from 1889 to 1840, 2490 to 2008 and 2878 to 2844 Ma. The youngest age peak of all the samples is ~1859 Ma, with the εHf(t) values of the zircons ranging from-20.3 to +4.3 and more than 90% being negative, indicating that the Paleoproterozoic crustal accretion on the southwestern margin of the Yangtze Block was dominated by reworking of the ancient crustal materials involved in the assembly and breakup of the Columbia supercontinent. Another important age range is between 2490 Ma and 2008 Ma, with εHf(t) values from-14.7 to +8.9 and 70% of them are negative, suggesting that the magmatism in the source area was also dominated by reworking and recycling of the ancient crustal materials, with minor juvenile mantle substances added. The detritus was probably derived from the Paleoproterozoic crystalline basement in the southern Yuxi region. The oldest peak age is ~2847 Ma and the εHf(t) values are from-7.7 to +7.0 with 50% of both positive and negative values, demonstrating a possible ~2.85 Ga ancient continental nucleus on the southwestern margin of the Yangtze Block and substantial growth in juvenile crust materials during this period. Besides, the weighted average age of the zircons from the meta-tuff of the Etouchang Formation is 1677 ± 14 Ma. Combining the previous research data and this study, we can constrain the depositional age of the Dongchuan Group in central Yunnan Province to the period from the late Paleoproterozoic to early Mesoproterozoic, slightly earlier than that of the Dongchuan Group in the Dongchuan area near to the southwestern Sichuan Province. The depositional age of the Dongchuan Group is older than that of the Kunyang Group.
文摘The Mianning-Dechang (MD) rare earth element (REE) belt, located in the northern Kangdian axis (KDA) in the western margin of the Yangtze platform, is one of the most economically significant REE mineral belts in China. REE mineralization is associated with Himalayan carbonatite- alkaline complexes. The Lizhuang nordmarkite occurred in the northern part of the MD REE belt. The majority of zircons from the Lizhuang nordmarkite are characterized by pronounced positive Ce yet slightly negative Eu anomalies and high U/Yb. Moreover, all zircons have stable Hf isotopic compositions with initial 176Hf/177Hf ratios ranging from 0.282739 to 0.282808 and an average value of 0.282773. The negative Lu/Hf and positive till(t) range from -0.98 to -0.94 (average value of -0.96) and from -0.56 to 1.89 (the majority is positive, with an average of 0.66), respectively. These characteristics indicate that the rock is derived from an enriched mantle and subducted material. LA-ICP-MS analysis of the zircons from the intrusion yields a weighted mean 2~6pb/23SU age of 28.57~0.61Ma. During this period, the tectonic activity in the KDA is not plate subduction but an intraplate tectonic exhibiting fold-thrust and strike-slip behaviors in the western marginal zone of the Yangtze platform (WMYB). We suggest the possibility of an existing eastward old slab subduction under WMYB combined with a regional tectonic evolution. The Lizhuang nordmarkite may be derived from an enriched mantle beneath the western part of the Yangtze craton, which originated from the remelting of the Tethys subducting slab, because of the Himalayan strike-slip that formed a special type of REE deposit called strike-slip-type REE deposits.
基金financially supported by the Natural Science Foundation of China(Grant No.41972198)the Cooperation Foundation of the Key Laboratory of Mineralogy and Metallogeny,Chinese Academy of Sciences(Grant No.KLMM20180201)the Scientific Research Starting Foundation of Central South University。
文摘The Neoproterozoic evolution of the Jiangnan Orogen is important for understanding the tectonic history of South China.As a volcanic-sedimentary sequence developed in the Nanhua rift,the Banxi Group preserves the records of important magmatic and tectonic events linked to the assembly and breakup of the Rodinia supercontinent.In this study,we report the results from whole-rock major-and trace-element concentrations,with zircon LA-(MC)-ICP-MS U-Pb ages,trace elements and Lu-Hf isotopic compositions of sandstones from the Banxi Group.The rocks are characterized by high SiO_(2)(65.88%–82.76%,with an average of 75.50%)contents,moderate(Fe_(2)O_(3)^(T)+MgO)(1.81%–7.78%,mean:3.79%)and TiO_(2)(0.39%–0.54%,mean:0.48%),low K_(2)O/Na_(2)O(0.03–0.40,mean:0.10)ratios and low Al_2O_(3)/SiO_(2)(0.11–0.24,mean:0.15)ratios.The sandstones have highΣREE contents(mean:179.1 ppm),with chondrite-normalized REE patterns similar to the upper crust and PAAS,showing enriched LREE((La/Yb)_N mean:14.85),sub-horizontal HREE curves and mild Eu(Eu/Eu^(*):0.75–0.89,mean:0.81)negative anomalies.Their geochemical characteristics resemble those of passive continental margin sandstones.Most of the zircons are magmatic in origin and yield a U-Pb age distribution with three peaks:a major age peak at 805 Ma and two subordinate age peaks at 1990 Ma and 2470 Ma,implying three major magmatic sources.The Neoproterozoic zircons haveε_(Hf)(t)values ranging from-47.4 to 12.4(mostly-20 to 0),suggesting a mixture of some juvenile arc-derived material and middle Paleoproterozoic heterogeneous crustal sources.The Hf model ages of middle Paleoproterozoic zircons(~1990 Ma)with negativeε_(Hf)(t)values(-12.65 to-6.21,Ave.=-9.8)concentrated around the Meso-Paleoarchean(mean T_(DM)^(C)=3.3–3.1 Ga).For late Neoarchean detrital zircons(~2470 Ma),ε_(Hf)(t)values are divided into two groups,one with negative values(-9.16 to-0.6)with model ages of 3.5–2.9 Ga,the other featuring positive values(1.0 to 3.9)with model ages of 2.9–2.7 Ga,recording a crustal growth event at~2.5 Ga.Neoproterozoic zircons show volcanic arc affinities with partly intraplate magmatic features.We propose that the Banxi Group formed in a rift basin within a passive continental margin setting,which derived detritus from felsic to intermediate rocks from the Yangtze Block and a small amount of arc volcanic rocks.The middle Paleoproterozoic detrital zircon data suggest Columbia-aged basement lies beneath the western Jiangnan orogen.
基金the National Natural Science Foundation of China(91962106,41702069)the National Key Research Program(2019YFA0708603)+4 种基金the Fundamental Research Funds for the Central Universities,China(2652018125)the 111 Project of the Ministry of Science and Technology,China(BP0719021)the China International Science and Technology Cooperation Award and the Overseas Experts Exchange Project of the Ministry of Science and Technology,China(G20190001257)the Beijing Nova Program(No.Z201100006820097)the National Natural Science Foundation of China.
文摘Radiogenic isotopic dating and Lu–Hf isotopic composition using laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS)of the Wude basalt in Yunnan province from the Emeishan large igneous province(ELIP)yielded timing of formation and post-eruption tectonothermal event.Holistic lithogeochemistry and elements mapping of basaltic rocks were further reevaluated to provide insights into crustal contamination and formation of the ELIP.A zircon U–Pb age of 251.3±2.0 Ma of the Wude basalt recorded the youngest volcanic eruption event and was consistent with the age span of 251-263 Ma for the emplacement of the ELIP.Such zircons hadε_(Hf)(t)values ranging from7.3 to+2.2,identical to those of magmatic zircons from the intrusive rocks of the ELIP,suggesting that crust-mantle interaction occurred during magmatic emplacement,or crust-mantle mixing existed in the deep source region prior to deep melting.The apatite U–Pb age at 53.6±3.4 Ma recorded an early Eocene magmatic superimposition of a regional tectonothermal event,corresponding to the Indian–Eurasian plate collision.Negative Nb,Ta,Ti and P anomalies of the Emeishan basalt may reflect crustal contamination.The uneven Nb/La and Th/Ta values distribution throughout the ELIP supported a mantle plume model origin.Therefore,the ELIP was formed as a result of a mantle plume which was later superimposed by a regional tectonothermal event attributed to the Indian–Eurasian plate collision during early Eocene.
基金financially supported by China Geological Survey (Grant no. DD20160060)the National Natural Science Foundation of China (Grant nos. 4153209, 41872135)
文摘In order to understand the petrogenesis and tectonic setting of diorite and diabase units on Doumer Island, Antarctic Peninsula, this paper reports new laser ablation-inductively coupled plasma-mass spectrometry(LA-ICP-MS) zircon U-Pb, geochemical, and Lu-Hf isotopic data for the magmatism. The diorite and diabase samples yielded zircon U-Pb ages of 55.4 ± 0.3 and 52.8 ± 0.4 Ma, respectively. These samples are enriched in the large ion lithophile elements and the light rare earth elements, and are depleted in the high field strength elements. The zircons in these samples yield eHf(t) values from 9.03 to 11.87 and model ages(TDM2) of 342–524 Ma. The major, trace, rare earth element(REE), and Hf isotopic data for the diorites indicate that these units were formed by the mixing of magmas generated by(a) the partial melting of mantle wedge material that experienced fluid-metasomatism in a subduction zone setting, and(b) the melting of juvenile crustal material induced by the upwelling of mantle-derived magmas in a subduction–collision setting. The diabase units contain higher total REE concentrations than the diorite, indicating they were derived from a different source region. These samples also have higher Mg~# values and contain lower concentrations of Cr and Ni than the diorites, and have weakly negative Nb and Ta anomalies with Nb/Ta values of <3. The zircons in these samples yield eHf(t) values from 9.08 to 11.11 and model ages(TDM2) of 389–503 Ma. The major, trace, REE, and Hf isotopic compositions of the diabase units indicate that that they were derived from the mixing of depleted mantle-derived magmas with magmas generated by the melting of juvenile crustal material which was induced by the upwelling of the mantle into the crust. Overall the Cenozoic diorite and diabase on Doumer Island is related to subduction environment.
基金supported by funding from Korea Institute of Geoscience and Mineral ResourcesChina University of Geosciences Beijing to M. Santosh+3 种基金supported by a Basic Research Project (GP2017-021Development of integrated geological information based on digital mapping) of the Korea Institute of Geoscience and Mineral Resources (KIGAM)funded by the Ministry of Science, ICTFuture Planning, Korea to S.W. Kim
文摘The Hongseong area of the Hongseong-Imjingang Belt in the central-western Korean Peninsula forms part of a subduction-collision system that is correlated with the Qinling-Dabie-Sulu Belt in China. Several serpentinized ultramafic bodies carrying blocks of metamorphosed mafic rocks occur in this area. Here we investigate zircon grains in serpentinites from Bibong(BB) and Wonnojeon(WNJ), and high-pressure(HP) mafic granulite from Baekdong(BD) localities based on U-Pb, REE and Lu-Hf analyses. The zircons from BD HP mafic granulite show distinct age peaks at 838 Ma, 617 Ma and 410 Ma, with minor peaks at1867 Ma, 1326 Ma and 167 Ma. The Neoproterozoic age peaks in these rocks as well as in the serpentinites suggest subduction-related melt-fluid interaction in the mantle wedge at this time. The older zircon grains ranging in age from the Early to Middle Paleoproterozoic might represent detrital grains from the basement rocks transferred to the wedge mantle through sediment subduction. The BD HP mafic granulite shows a Middle Paleozoic age peak(Devonian; 410 Ma). The 242-245 Ma age peaks in the compiled age data of zircon grains serpentinites from BB and WNJ correspond to a major Triassic event that further added melts and fluids into the ancient mantle wedge to crystallize new zircons. In the chondrite normalized rare earth element diagram, the magmatic zircon grains from the studied rocks show LREE depletion and HREE enrichment with sharply negative Eu and Pr anomalies and positive Ce and Sm anomalies. The REE patterns of hydrothermal zircons show LREE enrichment, and relatively flat patterns with negative Eu anomaly. Zircon Hf signature from the WNJ serpentinite show negative εHf(t)(-18.5 and-23.5) values indicating an enriched mantle source with TDM in the range of 1614 Ma and1862 Ma. Zircons from the BD HP mafic granulite also show slightly negative εHf(t)(average-4.3) and TDM in the range of 1365-1935 Ma. Our study provides evidence for multiple zircon growth in an evolving mantle wedge that witnessed melt and fluid interaction during different orogenic cycles.
基金financially supported by the Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology (No. MGQNLM201902)the National Natural Science Foundation of China (Nos. 41472155,41876037)+2 种基金the Scientific and Technological Innovation Project of the China Ocean Mineral Resources R & D Association (No. DY135-N2-1-04)the Scientific Research Foundation of Shandong University of Science and Technology for Recruited Talents (No. 2016RCJJ008)the SDUST Research Fund (No. 2015TDJH101).
文摘The Sulu Orogen preserves the Neoproterozoic tectonic-magmatic events,corresponding to the breaking up of the Rodinia supercontinent.The ages and petrogenesis of meta-igneous rocks in the Liansandao area in the northern Sulu Orogen are not well-constrained.This study reports zircon U-Pb ages and Hf isotopes of these rocks from the Liansandao area.Three meta-igneous rock samples give similar weighted mean 206 Pb/238 U ages of 744±11,767±12,and 762±15 Ma,respectively,indicating the Neoproterozoic crystallization ages.These rocks formed coevally with the Wulian and Yangkou intrusions that located along the Yantai-Qingdao-Wulian fault zone.The Neoproterozoic ages indicate that the meta-igneous rocks from the Liansandao area have affinity to the Yangtze Block.The three samples haveεHf(t)values of-7.2–-10.5,-6.0–-17.5,and-6.8–-12.0,respectively.These negativeεHf(t)values indicate a primarily crustal source.However,the widely variousεHf(t)values that are higher than the continental crust,suggesting magma mixing between mantle-derived materials and the continental crust or source heterogeneity.Combined with the Hf model ages and geochemical characteristics,the monzodiorite(sample LSD-2)is most likely to be mantle-derived magma then interacted with ancient continental crust,and the granitic protolith(samples LSD-1 and LSD-3)in the Liansandao area might derive from the re-melting of a Paleoproterozoic continental crust at^750 Ma,resulting from the upwelling and underplating of mantle-derived magma formed in an extensional setting due to the break-up of the Rodinia supercontinent.
基金supported by the National Natural Science Foundationof China(No.41190073)the National Basic Research Program of China(No.2014CB440901)the Fundamental Research Funds for the Central Universities to SYSU
文摘The Wuliangshan Group occurs to the east of the Lancang giant igneous zone in SW Yunnan, and is mainly composed of low-grade metamorphosed sedimentary rocks. The group has been considered as the syn-orogenic product of the Baoshan with Simao-Indochina blocks. However, its depositional time and provenance remain to be poorly constrained. This paper presents zircon U-Pb dating and Lu-Hf-isotopic data for five representative sandstone samples from the Wuliangshan Group. The detrital grains yield a major age-peak at ~259 Ma, and four subordinary age-peaks at ~1 859, ~941, ~788, and ~447 Ma, respectively. Our results suggest that the Wuliangshan metasedimentary sequence was deposited after Middle Triassic rather than previously-thought Cambrian. The detrital zircon age spectrum, along with in-situ Lu-Hf isotopic data suggest that the Wuliangshan Group might be a syncollisional sedimentary product related to the collision of Baoshan with Simao-Indochina blocks. It is inferred that the provenance of the Wuliangshan Group is mainly from the Simao/Yangtze blocks to the east rather than the Baoshan Block or Lancang igneous zone to the west.