| The North China Craton（NCC）participated in the assembly-breakup process of the Columbia Supercontinent in the late Paleoproterozoic.This process resulted in three distinct tectonic belts,namely,the Jiao-Liao-Ji belt（JLJB）in the Eastern Block,the Khondalite belt in the Western Block,and the Trans-North China Orogen situated between these two blocks.The JLJB primarily composed of extensive Paleoproterozoic metamorphic volcanic-sedimentary rocks sequences and intrusive rocks.The abundant sedimentary sequences and magmatic activities within the JLJB provide critical information about Columbia Supercontinent’s evolution.They offer substantial insights into regional tectonic evolution of the NCC during Paleoproterozoic.However,controversies persist regarding the tectonic setting of the Paleoproterozoic metamorphic volcanic-sedimentary rocks and intrusive rocks,as well as the Paleoproterozoic tectonic evolution models.The central point of contention is whether the early（2.2–2.1 Ga）rifting event occurred in a back-arc or continental setting,and whether the JLJB in the late Paleoproterozoic period experienced subduction-collision processes.This study focuses on the South Jilin province,located in the northeastern segment of the JLJB,and examines the Paleoproterozoic metamorphic volcanic-sedimentary rocks sequences（including the Guanghua Group,Ji’an Group,and Laoling Group）and intrusive rocks in this area.Utilizing a systematic approach that includes petrology,zircon U-Pb geochronology,geochemistry,and Sr-Nd-Hf isotopic analysis,our goal is to decipher the Paleoproterozoic tectonic evolution processes within the JLJB.Detrital zircon dating holds substantial implications across various aspects,including determining the age of Precambrian strata lacking biofossils and authigenic sedimentary minerals such as xenotime,tracing sediment provenance,and reconstructing the temporal framework of tectonic thermal events.Hence,in this study,we conducted a systematic detrital zircon U-Pb age test for each Formation within the Guanghua,Ji’an and Laoling Groups in the southern Jilin area.The dating results indicated that the youngest detrital zircons from the Guanghua Group is 2083 Ma,while the youngest ages of detrital zircons from the Formations of Mayihe,Huangchagou and Dadongcha of the Ji’an Group are2142 Ma,2036 Ma,and 1983 Ma,respectively.For the Laoling Group,the youngest ages of detrital zircons from the Formations of Dataishan,Zhenzhumen,Huashan,Linjiang,and Dalizi are 2074 Ma,2030 Ma,1979 Ma,1966 Ma,and 1947 Ma,respectively.These strata have experienced regional metamorphism,with recorded metamorphic ages ranging between 1.95 Ga to 1.80 Ga and a primary metamorphic age peak at 1.90 Ga,which is the upper limit of the depositional time,consistent with the regional metamorphic age reported by previous studies.Detrital zircon ages from the above formations display age peaks at 2.5 Ga,2.18–2.17 Ga,and 2.1–2.0 Ga,indicate that the provenance comes from the ancient basement of the Longgang and Nangrim Blocks,volcanic rocks from the rifting stage and igneous rocks,respectively.Notably,detrital zircon ages from the Dataishan Formation display a single peak at 2.5 Ga,consistent with detrital zircon ages from the Langzi Formation.Both formations are coarse clastic rock assemblages that developed along the margin of the Archean basement within the JLJB.They likely represent sedimentary products from the early rift stage and can be compared.The Mayihe and Li’eryu Formations are a set of boron-bearing volcanic-sedimentary assemblages characterized by bimodal volcanic rocks,indicating that they are rifting products.The Huangchagou（Ji’an Group）,Zhenzhumen（Laoling Group）,Gaojiayu and Dashiqiao（Laohe Group）Formations primarily consist of graphite-bearing detrital rocks and thick magnesium-rich carbonate rock assemblages.These formations reflect a stable tectonic environment during sedimentation,likely representing a passive continental margin environment.Detrital zircon ages commonly display age peaks between 2.2–2.1 Ga,indicating that volcanic rocks from the rift stage gradually became a significant source of sediments during this period.The Dadongcha（Ji’an Group）,Huashan-Linjiang-Dalizi（Laoling Group）and Gaixian（Liaohe Group）Formations primarily consist of aluminum-rich fine clastic rock assemblages with complex age peaks and relatively young detrital zircons.Given that these strata also lack carbonate rock assemblages,they potentially represent sedimentary products of either a residual basin during the subduction-collision stage.Zircon U-Pb dating results indicate that magmatic rocks in the Ji’nan region can be classified into three periods,i.e.,2.2–2.1 Ga,1.90 Ga,and 1.87–1.84 Ga,include 2.2–2.16Ga Qianzhuogou granites,～2.1 Ga Chibosong basic rocks,～1.9 Ga Shanchengzi granites,～1.87 Ga Qinghe diorites and～1.85 Ga Shuangcha granites.The 2.2–2.16 Ga Qianzhuogou granites primarily consist of monzogranite with relatively high contents of Si O2,K2O,Zr,Ga,Nb,Y,as well as A/NK and A/CNK ratios,and low Mg O and Sr contents.These characteristics suggest that they are typical A-type granites,with the majority of theirεHf（t）values being positive,andεNd（t）values ranging between-1.49 to1.28,and Nd and Hf two-stage model ages between 2.4 and 2.8 Ga,suggesting that the magma likely originated from partial melting of TTG rocks within the basement under high-temperature and low-pressure conditions.The～2.1 Ga Chibosong basic rocks mainly consist of diorites and amphibolites and display relatively low Si O2 and Na2O+K2O content and elevated TFe2O3 and Mg O content,exhibiting geochemical characteristics of tholeiitic basalts.Samples have elevated 87Sr/86Sr ratios and lowεNd（t）values,with Nb/La ratios below 1,indicating that these mafic rocks were contaminated by the crust,resulting in the depletion of elements such as Nb,Ta,and Ti.Major elements such as TFe O,Mg O,Al2O3,along with trace elements like Zr,Y/Zr exhibit characteristics of either continental or intraplate tholeiitic basalts.Thus,both the 2.2–2.16 Ga Qianzhuogou A-type granites and the～2.1 Ga Chibosong mafic rocks suggest that the Ji’nan region was situated within an intracontinental rift environment during the early Paleoproterozoic.The～1.9 Ga Shanchengzi granites primarily consist of monzogranite and exhibit typical geochemical characteristics of adakitic rocks,including high Sr content（120–806ppm）,low Y（1.03–4.02 ppm）and Yb（0.07–0.49 ppm）contents,and relatively high Sr/Y（38.43–798.57）and（La/Yb）N（15.92–53.53）ratios.They possess lower Mg O,Ni,Yb,and Y contents,negativeεHf（t）values ranging from-6.24 to-0.60,and negativeεNd（t）values between-5.20 to-3.99.The two-stage Hf model ages(TDM2)range between 2572 to 2882Ma,and the depleted mantle Nd model ages(TDM)between 2700 to 2795 Ma,suggesting that the parent magma originated from partial melting of the thickened lower crust.The obvious positive Eu anomalies（δEu=3.23–14.74）,high Sr/Y ratios,low Y and Yb contents,and lower Nb/Ta values indicate the presence of residual garnets within the magma source,and without plagioclase or biotite.The～1.9 Ga Shanchengzi adakitic granites should have formed at pressures betwenn 1.0–1.5 GPa（equivalent to depths of approximately 30–50 km）,which are comparable to the peak metamorphic age and pressure of pelitic and mafic granulites with clockwise P-T paths from the Ji’an Group,indicating that these granites represent magmatic products associated with the collisional phase.The～1.87 Ga Qinghe diorites have low Si O2（48.96–53.49 wt.%）and Y（31.77–36.25 ppm）contents,high Mg O（5.14–5.74 wt.%）,Cr（70.28–103.64 ppm）,Sr（585–1067ppm）,and Ba（755–1509 ppm）contents,along with Mg#values between 49–52,displaying geochemical characteristics of sanukite.Low initial(87Sr/86Sr)i and(143Nd/144Nd)i isotope ratios with negativeεNd（t）andεHf（t）values suggest that the magma originated from the enriched mantle and rocks retain signatures of arc magmatism,possibly influenced by early subduction fluids within the continental lithospheric mantle.The～1.85 Ga Shuangcha granites are porphyritic garnet-bearing granites with high Al2O3content（13.77–16.99 wt.%）,A/CNK values between 1.13–1.45,and exhibit peraluminous characteristics.εHf（t）values ranging from-3.36 to-0.93 and whole-rockεNd（t）values between-4.21 to-3.37 with several inherited zircons,and K2O content is considerably higher than Na2O,and potassium feldspar is typically developed,indicating that the source material for these granites may be aluminum-rich sedimentary rocks.Garnets within the granites are peritectic minerals,formed through biotite breakdown melting during near isothermal decompression（ITD）conditions.The～1.85 Ga Shuangcha granites are nearly contemporaneous with the ITD metamorphic stage of granulites from the Ji’an Group,representing alkaline,anhydrous,and non-orogenic A-type granites formed during the post-orogenic extensional stage.Combine our study of the Paleoproterozoic metamorphic-volcanic sedimentary rock series and magmatic events in the Liaodong-Southern Jilin area with previous studies,reveals that the JLJB underwent a tectonic process involving rifting,subduction,and collision.（1）Intracontinental rift-extension stage（2.2–2.1 Ga）:Intraplate extension and rifting triggered asthenospheric upwelling,resulting in widespread partial melting of middle-upper crustal rocks.This process formed 2.2–2.1 Ga A-type granites and contemporaneous bimodal volcanics（such as the Shuangmiao Formation of Guanghua Group and Mayihe Formation of Ji’an Group）,as well as deposited clastic sedimentary rocks of Dataishan and Langzishan Formations.（2）Passive continental margin to slab subduction stage（2.1–1.95 Ga）:As lithospheric extension continued,the environment transitioned from rifting to a passive continental margin.During this stage,massive clastic and carbonate rocks were deposited（such as those from Gaojiayu,Dashiqiao,Huangchagou,and Zhenzhumen Formations）,with an absence of magmatic activity.Subsequently,limited ocean basin expansion was hindered,and low-angle southward subduction commenced.Within this tectonic context,the Dadongcha,Huashan,Linjiang,and Dalizi Formations experienced extensive deposition of aluminum-rich terrigenous clastic facies.Subduction brought the surface sediments deep into the crust,which served as protoliths for high-pressure pelitic granulites following a clockwise P-T path.Owing to an absence of magmatic activity records during this period and geological evidence indicating widespread post-orogenic magmatism within the Nangrim Block,it can be inferred that southward subduction during this time may have been characterized by low-angle subduction.This hypothesis is consistent with the predominance of warm subduction during the Paleoproterozoic period.（3）Syn-collisional stage（1.95–1.87 Ga）:Collisional orogeny occurred between the Longgang and the Nangrim Blocks,resulting in crustal thickening and the formation of adakitic rocks（i.e.,Shanchengzi granites）under high-pressure conditions,as well as peak metamorphism of high-pressure granulites with clockwise P-T paths.（4）Post-collisional extension stage（1.87–1.84 Ga）:Within a post-collisional extensional setting,asthenospheric upwelling led partial melting of the lithospheric mantle modified by earlier subduction fluids to form sanukite（high-Mg diorites）.Additionally,partial melting of the middle and lower crust formed a series of extensional post-collisional magmatic rocks（such as Shuangcha granite）,accompanied by near-isothermal decompression during high-pressure granulites facies metamorphism.In summary,the Southern Jilin area within the JLJB underwent a complex tectonic evolution during the Paleoproterozoic period,involving rifting,subduction,and collision processes.This evolution represented a response from the NCC to Columbia Supercontinent’s assembly-breakup process. |
