New Evidence of Detrital Zircon Ages for the Final Closure Time of the Paleo-Asian Ocean in the Eastern Central Asian Orogenic Belt(NE China)

Objective The NE China is located in the eastern segment of the Central Asian Orogenic Belt（CAOB）,which is a large accretionary orogen between the Siberian Craton and the North China Craton（NCC）.Many researches have discussed about the evolution of the Paleo-Asian Ocean（PAO）in the eastern CAOB.However,

Age and Origin of Paleogene Granitoids from Western Yunnan Province,China:Geochemistry,SHRIMP Zircon Ages,and Hf-in-Zircon Isotopic Compositions

We report geochemical data, SHRIMP zircon ages and Hf-in-zircon isotopic compositions for Cenozoic granitoids from major fault systems in the Tethyan belt in western Yunnan Province, southwestern China.Four magmatic pulses occurred in the Paleogene, namely at ca.57 Ma, ca.50 Ma, 45–40 Ma, and 38–34 Ma.Early magmatism of this episode（57–50 Ma） produced S-type granites whose zircons yielded εHf（t） values of-5.0 to-0.3.In contrast, late magmatism of this episode reflects heterogeneous sources.Zircons from a granite porphyry along the Ailaoshan-Red River fault system have slightly positive εHf（t） values suggesting derivation from relatively young crust and/or a juvenile source.However, zircons from a granite along the Gaoligong fault system have strongly negative εHf（t） values and suggest derivation from a Paleoproterozoic crustal source.The composition of the granitoids varies with age（from ca.57 Ma to ca.34 Ma） from peraluminous to metaluminous and also suggests a change from syn-collisional to late-orogenic tectonic setting.A new tectonic model, impacting lithospheric wedge（ILW） is shown for the origin of Paleogene granitoids in this paper.

The Late Cretaceous Crustal Magmatism of the Geza Arc Metallogenic Belt in Yunnan Province,and Zircon Ages and Hf Isotopic Evidence of the Porphyry Cu-Mo Mineralization

Objective The Geza arc in Yunnan Province,located in the southern Yidun arc,is an important part of the Sanjiang tectonic-magmatic belts in southwestern China and is a newly discovered copper polymetallic ore-concentrating district.Recent studies show that the newly discovered Yanshanian porphyry Cu-Mo polymetallic mineralization superimposed in the Indosinian porphyry copper belt in this area.

The Early Breakup of Rodinia Supercontinent in the Northeastern Margin of the Yangtze Plate： New Evidence from SIMS Zircon Ages of the Granitic Gneiss from the Chaolian Island, Shandong Peninsula

The amalgamation and breakup mechanisms of the Rodinia supercontinent during the Meso- and Neoproterozoic have been the focus of much research. However, few studies have examined the response of Neoproterozoic tectonics and magmatism along the northeastern margin of the Yangtze Plate to synchronous global events. The Qianliyan Uplift is located on the eastern margin of the Sulu orogenic belt in the ocean, but the tectonic affinity of the uplift and its relationship to the Sulu orogenic belt remains unclear. In this study, we investigated the formation age, geochemical characteristics, genesis type, and affinity of the granitic gneiss on Chaolian Island of the Qianliyan uplift and its tectonic significance.

Field Relationships,Geochemistry,Zircon Ages and Evolution of a Late Archaean to Palaeoproterozoic Lower Crustal Section in the Hengshan Terrain of Northern China

The Hengshan complex forms part of the central zone of the North China Craton and consists predominantly of ductilely-deformed late Archaean to Palaeoproterozoic high-grade, partly migmatitic, granitoid orthogneisses, intruded by mafic dykes of gabbroic composition. Many highly strained rocks were previously misinterpreted as supracrustal sequences and represent mylonitized granitoids and sheared dykes. Our single zircon dating documents magmatic granitoid emplacement ages between 2.52 Ga and 2.48 Ga, with rare occurrences of 2.7 Ga gneisses, possibly reflecting an older basement. A few granitic gneisses have emplacement ages between 2.35 and 2.1 Ga and show the same structural features as the older rocks, indicating that the main deformation occurred after -2.1 Ga. Intrusion of gabbroic dykes occurred at -1920 Ma, and all Hengshan rocks underwent granulite-facies metamorphism at 1.88-1.85 Ga, followed by retrogression, sheafing and uplift. We interpret the Hengshan and adjacent Fuping granitoid gneisses as the lower, plutonic, part of a late Archaean to early Palaeoproterozoic Japan-type magmatic arc, with the upper, volcanic part represented by the nearby Wutai complex. Components of this arc may have evolved at a continental margin as indicated by the 2.7 Ga zircons. Major deformation and HP metamorphism occurred in the late Palaeoproterozoic during the Luliang orogeny when the Eastern and Western blocks of the North China Craton collided to form the Trans-North China orogen. Shear zones in the Hengshan are interpreted as major lower crustal discontinuities post-dating the peak of HP metamorphism, and we suggest that they formed during orogenic collapse and uplift of the Hengshan complex in the late Palaeoproterozoic （〈1.85 Ga）.

Polymetamorphism of the ultrahigh-temperature granulites in the Rauer Group,East Antarctica:new evidence from zircon SHRIMP U-Pb ages

The Rauer Group is located on the eastern margin of the early Paleozoic Prydz Belt in East Antarctica,and the typical ultrahigh-temperature(UHT,>900℃)granulites outcrop on Mather Peninsula.However,the timing of UHT metamorphism and P–T path of the UHT granulites have long been debated,which is critical to understanding the tectonic nature and evolution history of the Prydz Belt.Thus,both a sapphirine-bearing UHT metapelitic granulite and a garnet-bearing UHT mafic granulite are selected for zircon SHRIMP U-Pb age dating.The results show that metamorphic zircon mantles yield weighted mean^(206)Pb/^(238)U ages of 918±29 Ma and 901±29 Ma for the metapelitic and mafic granulites,respectively,while zircon rims and newly grown zircons yield weighted mean^(206)Pb/^(238)U ages of 523±9 Ma and 532±11 Ma,respectively.These new zircon age data suggest that the UHT granulites may have experienced polymetamorphism,in which pre-peak prograde stage occurred in the early Neoproterozoic Grenvillian orogenesis(1000–900 Ma),whereas the UHT metamorphism occurred in the late Neoproterozoic to early Paleozoic Pan-African orogenesis(580–460 Ma).This implies that P–T path of the UHT granulites should consist of two separate high-grade metamorphic events including the Grenvillian and Pan-African events,which are supposed to be related to assembly of Rodinia and Gondwana supercontinents respectively,and hence the overprinting UHT metamorphic event may actually reflect an important intracontinental reworking.

Detrital zircon ages of Oligocene to Miocene sandstone suites of the Southern Apennines foreland basin system,Italy

U-Pb spot ages on detrital zircons from turbidite quartzarenites,quartz-feldspathic and volcaniclastic sandstones of the Tufiti di Tusa(TTF),Numidian Flysch(NF),Bifurto(BF),Gorgoglione(GF)and Serra Palazzo(SPF)formations,exposed in southern Italy,were detected to define their provenance signatures aiming to contribute to reconstructing the complex geodynamic evolution of the southern Apennine chain.The deposition ages of these sandstones range from Rupelian(TTF),Burdigalian p.p.-Early Langhian(NF and BF)and Langhian-Serravallian-Early Tortonian(GF and SPF).The detrital zircon ages in each deposit show different clusters.In TTF,the zircon age clusters are:610±6 Ma;390±4 Ma;287±3 Ma;157±2 Ma;78±1 Ma and 67±1 Ma;33±1 Ma.In NF and BF formations,the prevalent zircon ages are clustered at 661±10 Ma,607±8 Ma and 547±8 Ma.In GF sandstones,the ages of detrital zircons are clustered around 672±28 Ma,458±9 Ma,297±8 Ma and 24±1 Ma.The sandstones of SPF contain zircons showing age clusters at649±10 Ma,486±7 Ma and 315±5 Ma.Zircons and lithic fragments from TTF display a dominant provenance from Oligocene calc-alkaline effusive products located on western domains of the Mesomediterranean Microplate,and minor detritus from granitoids and metamorphic rocks of Variscan ages.Zircons of NF and BF indicate a provenance of detritus from the African Craton without evidence of Variscan or Alpine signatures.Zircons from GF and SPF show a provenance from both Variscan crystalline basement rocks forming the Alpine chain(Calabria-Peloritani Terranes)and Variscan magmatic and metamorphic rocks unaffected by Alpine tectonics,similar to Sardinia-Corsica(pro-parte)block.In addition,the Oligocene magmatic component dated at 24 Ma in GF sandstones is evidence for the maximum age of sedimentation for these deposits.In light of the recent and preliminary geochronological data acquired,a revised paleogeographic restoration could be inferred for the location of sedimentary basins during the Apennines tectonic evolution.The Rupelian sedimentation age of TTF suggests that the deposition domains of the Numidian sequences and the successive deposits of GF and SPF,were located in a more complex paleogeographic scenario along the orogenic system.

Synchronous formation of the‘forearc’Bay of Islands ophiolite and its basal high-temperature metamorphic sole constrained by U-Pb zircon ages

The welded metamorphic sole at the base of the Bay of Islands Ophiolite Complex(BOIC)in the Northern Appalachians of Newfoundland shows a typical inverted pressure-temperature(P-T)metamorphic gradient from HT-MP granulite to LT-LP greenschist facies.It incorporates mafic volcanic/plutonic protoliths mixed with pelagic,hemi-pelagic and coarser epiclastic sedimentary protoliths.New LA-ICP-MS U–Pb concordia ages,trace elements,and Ti-in-zircon geothermometry for -250 zircon analyses from three metabasites of the upper HT sole amphibolites with N-MORB-like protoliths are reported.Two samples collected within meters of the ophiolite peridotite-sole contact of the Blow Me Down Mountain and North Arm Mountain massifs yielded the oldest comparable concordia ages of 487.7±2.6 Ma and 489.1±3.1 Ma,respectively,that are both within error of the igneous age of 488.3±1.5 Ma of the directly overlying BOIC ophiolite,which formed at a supra-subduction zone(SSZ)forearc spreading center.A third slightly younger age of 484.2±2.4 Ma was obtained for an upper HT amphibolite sample with similar phase assemblages but collected30 m below the peridotite contact of the Table Mountain massif.Zircon crystals analyzed have similar size and morphologies,subparallel rare earth element(REE)variation patterns,and steep heavy REE-enrichments((Lu/Gd)_(cn)>20),significant positive Ce anomalies(dominantly>5)and slight positive to dominantly negative Eu anomalies(1.2–0.4).Zircon shows Th/U mean values of 0.37–0.48 with little to no rim to core variation.Minimum Ti-in-zircon mean crystallization temperatures range from764–787℃.These neocrystallized zircon crystals appear to be derived from thin leucosomes within the three amphibolites.Two other samples also from the upper HT sole show evidence of inherited detrital zircon with core dates spanning the Cambrian Notre Dame Arc through older Laurentian-like basement and rift age ranges.Subcretion of the sole took place below a hot forearc asthenospheric wedge,that is,a consequence of the newly-formed BOIC forearc spreading center extending from the back arc to a triple junction along the westward-(or paleo-northward)verging trench of the Notre Dame arc.The early HT sole formation age at ca.489–488 Ma is long prior to initiation of obduction at ca.470 Ma and long after initiation of subduction beneath the paleo-northward verging Notre Dame peri-Laurentian arc at ca.514 Ma.This indicates Newfoundland sole ages of the BOIC and St.Anthony Complex are correlated with the age of SSZ spreading,but not necessarily subduction initiation because previously existing and self-sustaining subduction was ongoing.Sole ages are then not correlated with the younger age of obduction-related orogenic events(e.g.,proposed Taconic I and II)in the Newfoundland Appalachians.

Cretaceous Volcanic Events in Southeastern Jilin Province,China:Evidence from Single Zircon U-Pb Ages

Mesozoic volcanic rocks in southeastern Jilin Province are an important component of the huge Mesozoic volcanic belt in the northeastern area. Study of the age of their formation is of great significance to recognize Mesozoic volcanic rule in northeastern China. Along with the research of rare Mesozoic biota and extensive Mesozoic mineralization in western Liaoning, a number of researchers have focused on Mesozoic volcanic events. The authors studied the ages of the Cretaceous volcanic rocks in southeastern Jilin Province using single Zircon U-Pb. The result shows that the Sankeyushu Formation volcanic rocks in the Tonghua area are 119.2 Ma in age, the Yingcheng Formation in the Jiutai area 113.4±3.1 Ma, the Jinjiatun Formation in Pinggang Town of Liaoyuan City and the Wufeng volcanic rocks in the Yanji area 103.2±4.7 Ma and 103.6±1 Ma, respectively. Combined with the data of recent publication on volcanic rocks ages; the Cretaceous volcanic events in southeastern Jilin Province can be tentatively subdivided into three eruption periods： 119 Ma, 113 Ma and 103 Ma. The result not only provides important chronology data for subdividing Mesozoic strata in southeastern Jilin Province, establishing Mesozoic volcanic event sequence, discussing geological tectonic background, and surveying the relation between noble metals to the Cretaceous volcanic rocks, but also offers important information of Mesozoic volcanism in northeastern China.

Discovery of rhyolitic tuffaceous slate in the southwestern margin of Yangtze Craton:Zircon U-Pb ages(2491 Ma)and tectonic-thermal events

The Mesoproterozoic Dongchuan Group that is widely exposed in Yimen area,central Yunnan Province is a series of sedimentary sort of low-grade metamorphic rocks interbedded with volcanic rocks,which are closely related to the early tectonic evolution of the Earth.However,its formation era,sedimentary filling sequence,and geotectonic characteristics have always been in dispute.In this study,several rhyolitic tuffaceous slate interlayers with a centimeter-level thickness were found in the previously determined Heishan Formation of the Dongchuan Group located to the western part of Yimen-Luoci fault zone.This paper focuses on the study of the rhyolitic tuffaceous slate in Qifulangqing Village,Tongchang Township,Yimen County.LA-ICP-MS zircon dating was conducted,achieving the crystallization age of magma of 2491±15 Ma and the metamorphic ages of about 2.3 Ga,2.0 Ga,and 1.8 Ga for the first time.Meanwhile,according to in-situ Hf isotope analysis,the zirconεHf(t)values were determined to range from−3.0 to 7.6,with an average of 2.7.Furthermore,the first-stage Hf model age(TDM1)was determined to be 2513−2916 Ma,indicating that the provenance of the rhyolitic tuffaceous slate is the depleted mantle or juvenile crust between the Middle Mesoarchean and the Late Neoarchean.Therefore,it is believed that the strata of the slate were deposited in the Late Neoarchean,instead of the Mesoproterozoic as determined by previous researchers.Accordingly,it is not appropriate to group the strata into the Mesoproterozoic Dongchuan Group.Instead,they should be classified as the Maolu Formation of the Neoarchean Puduhe Group given the lithologic association and regional information.Furthermore,the magma ages of 2491±15 Ma are highly consistent with the eras of the large-scale Late Neoarchean orogenic magmatic activities on the northern margin of the Yangtze Craton,and thus reflect the orogenic process consisting of subduction and collision from Late Neoarchean to Early Paleoproterozoic.The magmatic activities during this period were possibly caused by the convergence of the supercontinent Kenorland.Meanwhile,the metamorphic ages of 2.3 Ga,2.0 Ga,and 1.8 Ga are highly consistent with three metamorphic ages of 2.36 Ga,1.95 Ga,and 1.85 Ga of the northern margin of the Yangtze Craton,indicating that the strata experienced Paleoproterozoic tectonic-thermal events.The study area is located on the eastern margin of Qinghai-Tibet Plateau,and thus was possibly re-transformed by magmatism subjected to the subduction of the Meso-Tethys Ocean during the Early Cretaceous.The discoveries made in this study will provide strong petrological and chronological evidence for analyzing the early crustal evolution of the Yangtze block.

Zircon U-Pb ages and Hf isotopic characteristics of the Dehe biotite monzonitic gneiss pluton in the North Qinling orogen and their geological significance

The Dehe granitic pluton intruded the Xiahe Group which is in the core complex of the North Qinling Orogenic Belt(NQOB).It shows gneissic bedding and possesses typical S-type granite minerals such as muscovite and garnet.LA-ICP-MS U-Pb isotopic dating of the Dehe granite yielded a weighted average age of 925±23 Ma which represents the emplacement age of the pluton.Most of the εHf(t) values are negative,and the two-stage model ages are consistent with the age of the Qinling Group.The isotope data show that the Dehe granite was formed in the following geological setting:in the syn-collision setting of the NQOB in the Neoproterozoic,crustal thickening induced partial melting of materials derived from the Qinling complex,and then the maga upwelled and intruded into the Xiahe Group.The formation of the Dehe S-type granite implied the occurrence of a convergent event in the QOB during the Neoproterozoic.

Discovery of the Dagele Eclogite in East Kunlun,Western China and Its Zircon SHRIMP U-Pb Ages:New Constrains on the Central Kunlun Suture Zone

Objective Eclogites are important indicators of ancient plate boundaries or paleosuture zones. Despite their great geological significance, very few investigations have been carried out in the Kunlun region. The Central East Kunlun fault zone was believed to be an Early Paleozoic suture zone, but there has been no reliable evidence for this, though studies on ophiolite, granite, and basic granulite indicate that the Early Paleozoic orogeny occurred in the East Kunlun. This work focused on the Dagele eclogites in Central East Kunlun to provide new constraints for the Central East Kunlun suture zone.

Zircon U-Pb Ages of Bottom and Top Parts of the Zhangjiakou Formation in Lingyuan Area(West Liaoning Province) and Luanping Area (North Hebei Province) and Their Significance

In Lingyuan region of West Liaoning Province, the Zhangjiakou Formation (J_3z) and the Yixian Formation (K_1y) display an angular unconformity. That is, the Lower Mesozoic strata of the Zhangjiakou Formation are ENE (near E-W) oriented, while the overlying strata of the Yixian Formation exhibit an NNE orientation. The results of LA-ICP-MS zircon U-Pb ages show the Zhangjiakou Formation formed from about 130 Ma to 132 Ma in Lingyuan and 135 Ma to 136 Ma in Luanping (North Hebei Province), respectively. Three conclusions can be drawn: (1) The Zhangjiakou Formation in Lingyuan is comparable to that in Luanping, with the volcanic rocks of the Zhangjiakou Formation from Lingyuan being younger than those from Luanping. (2) 5-6 Ma difference between the top of the Zhangjiakou Formation and the bottom of the Yixian Formation in Lingyuan proves the angular unconformity between the two formations; and it reflects that the 5-6 Ma interval period is the main period of the transition of tectonic framework in Mesozoic in North Hebei and West Liaoning. In the interval period, the magmatic action went up to high tide in Mesozoic in the northeast of China. Moreover, after the interval period, the “Rehe fauna” developed into “erupted” period. This reflects that the interval period is also an important biological interface in Northern Hebei and Western Liaoning. (3) The Dabeigou Formation in Luanping should correspond to the upper part of the Zhangjiakou Formation, but not to the lower part of the Yixian Formation.

Geochemistry and zircon U-Pb ages of the Oligocene sediments in the Baiyun Sag, Zhujiang River Mouth Basin

In this study,element geochemistry and zircon chronology are used to analyze the Oligocene sediments in the Baiyun Sag,Zhujiang River Mouth Basin.The experimental results are discussed with respect to weathering conditions,parent rock lithologies,and provenances.The chemical index of alteration and the chemical index of weathering values of mudstone samples from the lower Oligocene Enping Formation indicate that clastic particles in the study area underwent moderate weathering.Mudstone samples exhibit relatively enriched light rare earth elements and depleted heavy rare earth elements,"V"-shaped negative Eu anomalies,and negligible Ce anomalies.The rare earth element distribution curves are obviously right-inclined,with shapes and contents similar to those of post-Archean Australian shale and upper continental crust,indicating that the samples originated from acid rocks in the upper crust.The Hf-La/Th and La/Sc-Co/Th diagrams show this same origin for the sediments in the study area.For the samples from the upper Enping deltas,the overall age spectrum shows four major age peaks ca.59–68 Ma,98–136 Ma,153–168 Ma and 239–260 Ma.For the Zhuhai Formation samples,the overall age spectrum shows three major age peaks ca.149 Ma,252 Ma and 380 Ma.The detrital zircon shapes and U-Pb ages reveal that during Oligocene sedimentation,the sediments on the northwestern margin of the Baiyun Sag were supplied jointly from two provenances:Precambrian-Paleozoic metamorphic rocks in the extrabasinal South China fold zone and Mesozoic volcanic rocks in the intrabasinal Panyu Low Uplift,and the former supply became stronger through time.Thus,the provenance of the Oligocene deltas experienced a transition from an early proximal intrabasinal source to a late distal extrabasinal source.

First Report of Zircon U-Pb Ages from Lubei Cu-Ni Sulfide Deposit in East Tianshan of Central Asian Orogenic Belt, NW China

Objective The East Tianshan mafic-ultramafic rocks belt mainly produced in the eastern Jueluotage belt is an important part of the Central Asia Orogenic Belt （CAOB）. The well- known deposits including Huangshan, Huangshandong, Tulaergen, Hulu, Xiangshan were have been consecutively discovered in this belt （Duan Xingxing et al., 2016）. The new discovery of the Lubei Cu-Ni sulfide deposit in recent years, which locates in the west of Jueluotage belt, has great significance to the westward extension of the East Tianshan Cu-Ni metallogenic belt. To determine whether the mineralization age of the Lubei Cu-Ni sulfide deposit is consistent with other typical deposits, this study conducted zircon U-Pb geochronology on the diorite from the Lubei Cu-Ni sulfide deposit in order to provide new information for further exploring direction of Cu-Ni prospecting in East Tianshan.

U-Pb Ages and Hf Isotope of Zircons from a Carbonatite Dyke in the Bayan Obo Fe-REE Deposit in Inner Mongolia: its Geological Significance

Detailed studies on U-Pb ages and Hf isotope have been carried out in zircons from a carbonatite dyke associated with the Bayan Obo giant REE-Nb-Fe deposit,northern margin of the North China Craton(NCC),which provide insights into the plate tectonic in Paleoproterozoic.Analyses of small amounts of zircons extracted from a large sample of the Wu carbonatite dyke have yielded two ages of late Archaean and late Paleoproterozoic(with mean 207 Pb/206 Pb ages of 2521±25 Ma and 1921±14 Ma,respectively).Mineral inclusions in the zircon identified by Raman spectroscopy are all silicate minerals,and none of the zircon grains has the extremely high Th/U characteristic of carbonatite,which are consistent with crystallization of the zircon from silicate,and the zircon is suggested to be derived from trapped basement complex.Hf isotopes in the zircon from the studied carbonatite are different from grain to grain,suggesting the zircons were not all formed in one single process.Majority ofεHf(t)values are compatible with ancient crustal sources with limited juvenile component.The Hf data and their TDM2 values also suggest a juvenile continental growth in Paleoproterozoic during the period of 1940–1957 Ma.Our data demonstrate the major crustal growth during the Paleoproterozoic in the northern margin of the NCC,coeval with the assembly of the supercontinent Columbia,and provide insights into the plate tectonic of the NCC in Paleoproterozoic.

Relationship between Granite and Eclogite on the Southern Margin of the Qilian Mountains: Evidence from Zircon SHRIMP Agesof the Aolaoshan Granite

Zircon SHRIMP ages of the Aolaoshan granite on the south margin of the QilianMts. range from 445 + - 15.3 to 496 + - 7.6 Ma (averaging 473 Ma), belonging to the EarlyOrdovician. Geochemically, the granite is similar to I-type granite and, tectonically, was formed inan island-arc environment based on relevant diagrams for structural discriminations. Consideringalso the regional geology, the authors suggest that the granite is part of an ultrahigh-pressurebelt on the south margin of the Qilian Mts. and that its formation bears a close relationship tothis belt.

SHRIMP Zircon U-Pb Ages of the Wajilitag Igneous Complex: Constraints on the Origin of A-type Granitoids in the Tarim Large Igneous Province, NW China

Objective Large igneous provinces （LIPs） are sites of spatially contiguous, rapidly emplaced magmatic rocks, which represent the physical and chemical transfer of material from the mantle to the crust. Exposed within some continental LIPs are felsic and rnafic plutonic and volcanic rocks. Although their volumes are minor compared to the flood basalts, the plutonic rocks of continental LIPs are often associated with economic deposits of precious metals. Within the Permian Tarim LIP of NW China, there are at least two layered ultramafic-mafic intrusions （e.g. Wajilitag and Piqiang） contain economically important Fe- Ti-V oxide deposits. Spatially associated with these layered ultramafic-mafic intrusions are syenitic and granitic plutons, which have chemical characteristics of A- type granitoids.

The Tectonic Implications of the Hongliuhe-Xichangjing Ophiolitic Mélanges Belt in the Central Region of the Beishan Orogen, NW China——Constrained by the U-Pb Ages of Detrital Zircons of the Metasandstones

The tectonic attributes of different blocks within orogenic belts are of great significance for the study of accretionary processes and the evolution of Earth. The Hongliuhe-Niujianzi-Baiyunshan-Xichangjing ophiolitic mélange belt(HXOMB) is distributed in the heart of the Beishan Orogen, the Shuangyingshan and Minshui-Hanshan blocks being distributed in the south and north of the HXOMB respectively, and a large number of Early Paleozoic geological units are exposed on the blocks. According to the zircon age populations of the metasandstones in the Baiyunshan area recovered in this paper, when compared with the zircon age populations of the Paleozoic metasandstones reported in the Niujuanzi and Hanshan areas, we found that the metasandstones of the Shuangyingshan Block have age peaks at c. 598 Ma, 742 Ma, 828 Ma, 941 Ma, 990 Ma, 1168 Ma, 1636 Ma, 2497 Ma with non-significant age populations of 1500–1300 Ma, showing a possible affinity with the Tarim Craton;the metasandstones of the Minshui-Hanshan Block have age peaks at c. 606 Ma, 758 Ma, 914 Ma, 1102 Ma, 1194 Ma, 1304 Ma, 1672 Ma with significant age populations of 1500-1300 Ma, showing a possible affinity with the Chinese Central Tianshan Block. Therefore, the HXOMB of the Beishan Orogen is of great significance in plate segmentation, which separates the Tarim Craton in the south and the Chinese Central Tianshan Block in the north. Based on the evolutionary process of the Hongliuhe-Xichangjing ocean in the Beishan Orogen, we believe that break-up and convergence can be recognized as having occurred twice between the Chinese Central Tianshan Block and the Tarim Craton since the Mesoproterozoic in the Beishan area. This was related firstly to the break-up of the Columbia Supercontinent and the convergence of the Rodinia Supercontinent, mainly during the Middle Mesoproterozoic to Early Neoproterozoic, and secondly to the opening and closing of the Hongliuhe-Xichangjing ocean, mainly during the Early Paleozoic.

New Zircon U-Pb Ages of Granitic Rocks in Northeastern Jiagedaqi of the Da Hinggan Mountains and their Significance

Objective The research area is located in the north of the Xing＇an block and within the Ali River-Zhalantun granite belt in the eastern part of the Xingmeng orogenic belt. The geotectonic setting and geological evolution history of this area are complex with strong magmatic activity and extremely developed granite rocks. Since predecessors have not obtained accurate dating result, there is much controversy over the formation of granitic rocks. Therefore, this work conducted zircon U-Ph dating on alkali-feldspar granite and granite porphyry in the northeast of Jiagedaqi to provide age constraint. The age data shows that the forming age is the Early Cretaceous and provides age basis for the tectonic evolution of the Da Hinggan Mountains.