Sedimentary response to the paleogeographic and tectonic evolution of the southern North China Craton during the late Paleozoic and Mesozoic

With the aim of constraining the influence of the surrounding plates on the Late Paleozoic–Mesozoic paleogeographic and tectonic evolution of the southern North China Craton (NCC), we undertook new U–Pb and Hf isotope data for detrital zircons obtained from ten samples of upper Paleozoic to Mesozoic sediments in the Luoyang Basin and Dengfeng area. Samples of upper Paleozoic to Mesozoic strata were obtained from the Taiyuan, Xiashihezi, Shangshihezi, Shiqianfeng, Ermaying, Shangyoufangzhuang, Upper Jurassic unnamed, and Lower Cretaceous unnamed formations (from oldest to youngest). On the basis of the youngest zircon ages, combined with the age-diagnostic fossils, and volcanic interlayer, we propose that the Taiyuan Formation (youngest zircon age of 439 Ma) formed during the Late Carboniferous and Early Permian, the Xiashihezi Formation (276 Ma) during the Early Permian, the Shangshihezi (376 Ma) and Shiqianfeng (279 Ma) formations during the Middle–Late Permian, the Ermaying Group (232 Ma) and Shangyoufangzhuang Formation (230 and 210 Ma) during the Late Triassic, the Jurassic unnamed formation (154 Ma) during the Late Jurassic, and the Cretaceous unnamed formation (158 Ma) during the Early Cretaceous. These results, together with previously published data, indicate that: (1) Upper Carboniferous–Lower Permian sandstones were sourced from the Northern Qinling Orogen (NQO); (2) Lower Permian sandstones were formed mainly from material derived from the Yinshan–Yanshan Orogenic Belt (YYOB) on the northern margin of the NCC with only minor material from the NQO; (3) Middle–Upper Permian sandstones were derived primarily from the NQO, with only a small contribution from the YYOB; (4) Upper Triassic sandstones were sourced mainly from the YYOB and contain only minor amounts of material from the NQO; (5) Upper Jurassic sandstones were derived from material sourced from the NQO; and (6) Lower Cretaceous conglomerate was formed mainly from recycled earlier detritus.The provenance shift in the Upper Carboniferous–Mesozoic sediments within the study area indicates that the YYOB was strongly uplifted twice, first in relation to subduction of the Paleo-Asian Ocean Plate beneath the northern margin of the NCC during the Early Permian, and subsequently in relation to collision between the southern Mongolian Plate and the northern margin of the NCC during the Late Triassic. The three episodes of tectonic uplift of the NQO were probably related to collision between the North and South Qinling terranes, northward subduction of the Mianlue Ocean Plate, and collision between the Yangtze Craton and the southern margin of the NCC during the Late Carboniferous–Early Permian, Middle–Late Permian, and Late Jurassic, respectively. The southern margin of the central NCC was rapidly uplifted and eroded during the Early Cretaceous.     

Provenance of Late Carboniferous bauxite deposits in the North China Craton: New constraints on marginal arc construction and accretion processes

The North China Craton (NCC) is bounded by two Paleozoic accretionary arc terranes: the North Qinling terrane to the south and the Bainaimiao terrane to the north. The timing of arc accretion to the NCC and the architecture of the Bainaimiao arc remain unclear. During the building and accretion of the arcs along its margins, the NCC experienced a long sedimentary hiatus since the Ordovician, which ended with the deposition of bauxite-bearing sediments in the Late Carboniferous. In this paper we report the U–Pb and Hf isotopes of detrital zircons from the Late Carboniferous bauxite layer and use these data to constrain the tectonic evolution of the margin of the NCC. The detrital zircons yield a minimum U–Pb age of ca. 310 Ma and a prominent age peak at ca. 450 Ma. Zircon crystals with ages of ca. 330 Ma and ca. 1900 Ma are more common in the bauxite samples from the northern part of the NCC than in those from the central part. The εHf(t) values of the ca. 450 Ma detrital zircon crystals of the bauxite samples from the NCC are similar to those of the contemporaneous detrital zircon crystals from the North Qinling arc terrane to the south, but different from those of the contemporaneous detrital zircon crystals from the Bainaimiao arc terrane to the north. The ca. 450 Ma detrital zircon crystals in the ca. 310 Ma bauxite deposits are therefore interpreted to have been derived from the North Qinling arc terrane. The source of the ca. 330 Ma detrital zircon crystals of the bauxite deposits is interpreted to be the northern margin of the NCC, where intermediate-felsic plutons formed at ca. 330 Ma are common. The results from this study support the interpretation that the Paleozoic continental arc terranes and their concomitant back-arc basins were developed along the margins of the NCC before ca. 450 Ma, and the arc complexes were subsequently accreted to the craton in the Late Carboniferous. This was then followed by the formation of a walled continental basin within the NCC.     

A geotraverse across two paleo-subduction zones in Tien Shan,Tajikistan

We present first LA-ICP-MS U–Pb zircon ages as well as geochemical and Sr–Nd–Pb isotope data for 14 magmatic rocks collected along ca. 400 km profile across the Chatkal-Kurama terrane in the Mogol-Tau and Kurama ranges and the Gissar Segment of the Tien Shan orogen in Tajikistan. These new data from supra-subduction and post-collisional magmatic rocks of two Late Paleozoic active margins constrain a tectonic model for terrane motions across two paleo-subduction zones: (1) The 425 Ma old Muzbulak granite of the Mogol-Tau range formed in a supra-subduction setting at the northern margin of the Turkestan Ocean. The north-dipping plate was subducted from the Early Silurian to the earliest Middle Devonian. Thereafter the northern side of the Turkestan Ocean remained a passive margin until the Early Carboniferous. (2) In the Early Carboniferous, subduction under the northern margin of the Turkestan Ocean resumed and the 315 to 305 Ma old Kara-Kiya, Muzbek, and Karamazar intrusions formed in a supra-subduction setting in the Mogol-Tau and Kurama ranges. (3) At the same time, in the Early Carboniferous, rifting of the southern passive margin of the Turkestan Ocean formed the short-lived Gissar Basin, separated from the Turkestan Ocean by the Gissar micro-continent. North-dipping subduction in the Gissar Basin is documented by the 315 Ma Kharangon plagiogranite and the voluminous ca. 321–312 Ma Andean-type supra-subduction Gissar batholith. The Kharangon and Khanaka gabbro-plagiogranite intrusions of the southern Gissar range have geochemical and Sr–Nd isotopic compositions (⁸⁷Sr/⁸⁶Sr(t) 0.7047–0.7056, εNd of + 1.5 to + 2.3) compatible with mantle-derived origin typical for plagiogranites associated with ophiolites. The supra-subduction rocks from the Gissar batholith and from the Mogol-Tau Kurama ranges have variably mixed Sr–Nd–Pb isotopic signatures (⁸⁷Sr/⁸⁶Sr(t) 0.7057–0.7064, εNd of − 2.1 to − 5.0) typical for continental arcs where mantle-derived magmas interact with continental crust. (4) In the latest Carboniferous, the Turkestan Ocean and the Gissar Basin were closed. The Early Permian Chinorsay (288 Ma) and Dara-i-pioz (267 Ma) post-collisional intrusions, emplaced in the northern part of the Gissar micro-continent after a long period of amagmatic evolution, have intraplate geochemical affinities and isotopic Sr–Nd–Pb isotopic compositions (⁸⁷Sr/⁸⁶Sr(t) 0.7074–0.7086, εNd of − 5.5 to − 7.4) indicating derivation from Precambrian continental crust which is supported by old Nd model ages (1.5 and 1.7 Ga), and by the presence of inherited zircon grains with ages 850–500 Ma in the Chinorsay granodiorite. The post-collisional intrusions in the southern Gissar and in the Mogol-Tau and Kurama ranges (297–286 Ma), emplaced directly after supra-subduction magmatic series, have geochemical and isotopic signatures of arc-related magmas. The distinct shoshonitic affinities of post-collisional intrusions in the Mogol-Tau and Kurama ranges are explained by the interaction of hot asthenospheric material with subduction-enriched wedge of lithospheric mantle due to slab break-off at post-collisional stage. Despite origination from different tectonic environments, all magmatic rocks have relatively old Nd model ages (1.7–1.0 Ga) indicating a significant proportion of Paleoproterozoic or older crustal material in their sources and their model ages are similar to those of post-collisional intrusions from the Alai and Kokshaal Segments of the South Tien Shan.     

Spatial–temporal relationships of Mesozoic volcanic rocks in NE China: Constraints on tectonic overprinting and transformations between multiple tectonic regimes

LA-ICP-MS zircon U–Pb ages and geochemical data are presented for the Mesozoic volcanic rocks in northeast China, with the aim of determining the tectonic settings of the volcanism and constraining the timing of the overprinting and transformations between the Paleo-Asian Ocean, Mongol–Okhotsk, and circum-Pacific tectonic regimes. The new ages, together with other available age data from the literature, indicate that Mesozoic volcanism in NE China can be subdivided into six episodes: Late Triassic (228–201 Ma), Early–Middle Jurassic (190–173 Ma), Middle–Late Jurassic (166–155 Ma), early Early Cretaceous (145–138 Ma), late Early Cretaceous (133–106 Ma), and Late Cretaceous (97–88 Ma). The Late Triassic volcanic rocks occur in the Lesser Xing’an–Zhangguangcai Ranges, where the volcanic rocks are bimodal, and in the eastern Heilongjiang–Jilin provinces where the volcanics are A-type rhyolites, implying that they formed in an extensional environment after the final closure of the Paleo-Asian Ocean. The Early–Middle Jurassic (190–173 Ma) volcanic rocks, both in the Erguna Massif and the eastern Heilongjiang–Jilin provinces, belong chemically to the calc-alkaline series, implying an active continental margin setting. The volcanics in the Erguna Massif are related to the subduction of the Mongol–Okhotsk oceanic plate beneath the Massif, and those in the eastern Jilin–Heilongjiang provinces are related to the subduction of the Paleo-Pacific Plate beneath the Eurasian continent. The coeval bimodal volcanic rocks in the Lesser Xing’an–Zhangguangcai Ranges were probably formed under an extensional environment similar to a backarc setting of double-direction subduction. Volcanic rocks of Middle–Late Jurassic (155–166 Ma) and early Early Cretaceous (145–138 Ma) age only occur in the Great Xing’an Range and the northern Hebei and western Liaoning provinces (limited to the west of the Songliao Basin), and they belong chemically to high-K calc-alkaline series and A-type rhyolites, respectively. Combined with the regional unconformity and thrust structures in the northern Hebei and western Liaoning provinces, we conclude that these volcanics formed during a collapse or delamination of a thickened continental crust related to the evolution of the Mongol–Okhotsk suture belt. The late Early Cretaceous volcanic rocks, widely distributed in NE China, belong chemically to a low- to medium-K calc-alkaline series in the eastern Heilongjiang–Jilin provinces (i.e., the Eurasian continental margin), and to a bimodal volcanic rock association within both the Songliao Basin and the Great Xing’an Range. The volcanics in the eastern Heilongjiang–Jilin provinces formed in an active continental margin setting related to the subduction of the Paleo-Pacific Plate beneath the Eurasian continent, and the bimodal volcanics formed under an extensional environment related either to a backarc setting or to delamination of a thickened crust, or both. Late Cretaceous volcanics, limited to the eastern Heilongjiang–Jilin provinces and the eastern North China Craton (NCC), consist of calc-alkaline rocks in the eastern Heilongjiang–Jilin provinces and alkaline basalts in the eastern NCC, suggesting that the former originated during subduction of the Paleo-Pacific Plate beneath the Eurasian continent, whereas the latter formed in an extensional environment similar to a backarc setting. Taking all this into account, we conclude that (1) the transformation from the Paleo-Asian Ocean regime to the circum-Pacific tectonic regime happened during the Late Triassic to Early Jurassic; (2) the effect of the Mongol–Okhotsk suture belt on NE China was mainly in the Early Jurassic, Middle–Late Jurassic, and early Early Cretaceous; and (3) the late Early Cretaceous and Late Cretaceous volcanics can be attributed to the subduction of the Paleo-Pacific Plate beneath the Eurasian continent.     

Neoarchean convergent margin tectonics associated with microblock amalgamation in the North China Craton: Evidence from the Yishui Complex

Archean tectonic history of the North China Craton (NCC) involved complex processes of amalgamation of microcontinents along multiple subduction zones prior to the consolidation of the major crustal blocks and their assembly into unified cratonic architecture. Here we report a suite of granitoids, diabase, metabasalts, volcanic tuff, banded iron formations and quartzite from the Yishui Complex along the southern margin of the Jiaoliao microblock within the Eastern Block of the NCC. The geochemical features of the magmatic suite are consistent with calc-alkaline magmatism in a convergent margin setting. In tectonic discrimination diagrams, the mafic suite shows variable IAB, MORB and OIB affinities typical of rocks formed in an arc-related subduction environment. Zircon grains in most of the rocks from Yishui Complex display core–rim texture with the cores showing magmatic crystallization and the narrow structureless rims corresponding to metamorphic overgrowth. The ²⁰⁷Pb/²⁰⁶Pb ages of magmatic zircons show 2504 ± 19 Ma for the volcanic tuff, 2581 ± 21 Ma for the granitoid, 2501 ± 19 Ma for the metavolcanics, 2537 ± 38 Ma for the pyroxenite, and 2506 ± 13 Ma for the diabase. Metamorphism is constrained from the 2451 ± 18 Ma and 2466 ± 23 Ma age groups in the metavolcanics and (meta-) pyroxenites. Zircons from BIF show multiple population with the oldest showing a spot age of 2503 Ma, followed by a number of distinct groups of Paleoproterozoic zircons corresponding to later thermal events. The oldest population of magmatic zircons from the quartzite shows ²⁰⁷Pb/²⁰⁶Pb mean age of 2495 ± 24 Ma. The dominantly positive εHf(t) values of the magmatic zircons from the Yishui suite are broadly consistent with a depleted mantle source with only minor input of crustal components. Their Hf crustal residence ages (T_DM^C) range from 2586 to 3181 Ma and Hf depleted mantle model ages (T_DM) are in the range of 2548–2927 Ma. The data indicate that magma production involved Meso- to Neoarchean juvenile sources within a continental arc setting, suggesting the Jiaoliao microblock as one of the ancient continental nuclei in the NCC. We trace the continuity of a Neoarchean subduction system along the western and southern margins of the Jiaoliao microblock with convergence of the Qianhuai and Xuhuai microblocks towards the Jiaoliao microblock with subduction–accretion–collision during the Archean–Proterozoic transition.     

Detrital zircon U-Pb-Hf isotopes and provenance of Late Neoproterozoic and Early Paleozoic sediments of the Simao and Baoshan blocks,SW China: Implications for Proto-Tethys and Paleo-Tethys evolution and Gondwana reconstruction

Early Paleozoic evolution of the northern Gondwana margin is interpreted from integrated in situ U-Pb and Hf-isotope analyses on detrital zircons that constrain depositional ages and provenance of the Lancang Group, previously assigned to the Simao Block, and the Mengtong and Mengdingjie groups of the Baoshan Block. A meta-felsic volcanic rock from the Mengtong Group yields a weighted mean ²⁰⁶Pb/²³⁸U age of 462 ± 2 Ma. The depositional age for the previously inferred Neoproterozoic Lancang and Mengtong groups is re-interpreted as Early Paleozoic based on youngest detrital zircons and meta-volcanic age. Detrital U-Pb zircon analyses from the Baoshan Block define three distinctive age peaks at older Grenvillian (1200–1060 Ma), younger Grenvillian (~ 960 Ma) and Pan-African (650–500 Ma), with εHf(t) values for each group similar to coeval detrital zircons from western Australia and northern India. This suggests that the Baoshan Block was situated in the transitional zone between northeast Greater India and northwest Australia on the Gondwana margin and received detritus from both these cratons. The Lancang Group yields a very similar detrital zircon age spectrum to that of the Baoshan Block but contrasts with that for the Simao Block. This suggests that the Lancang Group is underlain by a separate Lancang Block. Similar detrital zircon age spectra suggest that the Baoshan Block and the Lancang Block share common sources and that they were situated close to one another along the northern margin of East Gondwana during the Early Paleozoic. The new detrital zircon data in combination with previously published data for East Gondwana margin blocks suggests the Early Paleozoic Proto-Tethys represents a narrow ocean basin separating an “Asian Hun superterrane” (North China, South China, Tarim, Indochina and North Qiangtang blocks) from the northern margin of Gondwana during the Late Neoproterozoic-Early Paleozoic. The Proto-Tethys closed in the Silurian at ca. 440–420 Ma when this “Asian Hun superterrane” collided with the northern Gondwana margin. Subsequently, the Lancang Block is interpreted to have separated from the Baoshan Block during the Early Devonian when the Paleo-Tethys opened as a back-arc basin.     

Proto-Andean evolution of the Eastern Cordillera of Peru

The Eastern Cordillera of Peru represents one of the longest (> 1200 km) Paleozoic metamorphic and magmatic belts exposed along the western Andean margin of South America. In this study, we examine the tectonothermal evolution of a key segment of the metasedimentary basement of the Eastern Cordillera of Peru (the Huaytapallana Complex) and demonstrate that it has experienced a hitherto undocumented high-grade orogenic event at 260 Ma (latest Middle Permian) based on U–Pb and Th–Pb monazite age data from paragneisses and U–Pb dating of zircon rims from leucosomes. These ages are interpreted as recording crystallization and are consistent with 255 Ma rutile growth in lower-grade units. U–Pb apatite data (c. 260–230 Ma) in all units are consistent with slow cooling from this 260 Ma metamorphic peak. U–Pb zircon geochronology of pre-tectonic plutons yield ages ranging from c. 302 Ma to c. 260 Ma. These geochronological data are augmented by new U–Pb apatite age data from other segments along the Eastern Cordillera of Peru. A regional synthesis of existing geochronological constraints from the Eastern Cordillera of Peru demonstrates that the margin has experienced a polycyclic orogenic history. Deformation and magmatism occurred at c. 480 Ma and c. 435 Ma during the Famatinian orogenic cycle, was followed by a Late Silurian to Early Carboniferous (c. 420–350 Ma) magmatic and metamorphic gap, and terminated with Gondwanide magmatism and metamorphism at c. 315 Ma and c. 260 Ma. These Famatinian and Gondwanide orogenic phases can be correlated into the Proto-Andean margin of Argentina and Chile and are thus of regional extent. The evolution of the Proto-Andean margin is thus best explained by changes in tectonic plate reorganization in a long-lived Paleozoic accretionary orogen which was undergoing phases of advance and retreat, resulting in magmatic pulses and orogenic phases which can be correlated along the length of the plate boundary.     

Mesoproterozoic magmatic events in the eastern North China Craton and their tectonic implications: Geochronological evidence from detrital zircons in the Shandong Peninsula and North Korea

Whether any Grenvillian magmatic records are preserved in the North China Craton (NCC) is a key issue to understand the Proterozoic tectonic evolution of the NCC and its correlation to the supercontinent Rodinia. Meso- to Neo-proterozoic sedimentary series is well exposed in the NCC, but magmatic events in this period, especially of 1.3–1.0 Ga, have seldom been reported. New U–Pb isotopic dating and Hf isotopic composition analyses have been carried out in this study using SIMS and LA–ICP-MS methods on detrital zircons from sandstones of the Tumen Group in the Shandong Peninsula and quartz sandstones of the Sangwon System in the Phyongnam Basin, North Korea. The age populations of the detrital zircons of the Tumen Group are at ~ 2.5 Ga, ~ 1.85 Ga, ~ 1.7 Ga, ~ 1.58 Ga, ~ 1.5 Ga, ~ 1.36 Ga and ~ 1.2 Ga and those of the Sangwon System are at 1.88–1.86 Ga, ~ 1.78 Ga, 1.62–1.58 Ga, 1.46–1.41 Ga, ~ 1.32 Ga, ~ 1.17 Ga and ~ 980 Ma. Most of the age peaks of Neoarchean and Proterozoic correspond to the significant tectonic-magmatic-thermal events previously recognized in the NCC, revealing that the main provenances of the Tumen Group and the Sangwon System are Early Precambrian basement and Late Paleo- to Meso-proterozoic magmatic rocks of the NCC. Furthermore, the youngest detrital zircon ages of ~ 1.1 Ga from the Tumen Group and 984 Ma from the Sangwon System, as well as 910 Ma Rb–Sr whole rock isochron age of a limestone from the Tumen Group and 899 Ma mafic sills intruding the Sangwon System suggest that both groups were deposited in the Neoproterozoic, coevally with the Qingbaikou System in the Yanliao Aulacogen. The common zircon ages of 1.3–1.0 Ga from the Tumen Group and the Sangwon System, as well as the contemporaneous Penglai and Yushulazi Group in the eastern margin of the NCC, indicate that during the deposition of these sediments there have been significant contributions from Grenvillian magmatic rocks in the eastern NCC. This may provide clues to understand the possible relationship of the NCC and the supercontinent Rodinia. Moreover, the positive εHf (t) and ~ 2.8 Ga crust model ages of detrital magmatic zircons of 2.8–2.4 Ga suggest that there have been significant crustal growth at ~ 2.8 Ga in the eastern margin of the NCC, same as in other areas of the NCC.     

Mesozoic magmatism and metallogenesis associated with the destruction of the North China Craton: Evidence from U–Pb geochronology and stable isotope geochemistry of the Mujicun porphyry Cu–Mo deposit

The North China Craton (NCC) provides a classic example of lithospheric destruction and refertilization. The timing and duration of magmatism and related metallogenesis associated with the destruction process are pivotal to understanding the geodynamic controls. In this study, we present zircon U–Pb and Hf data, Re–Os ages, and He, Ar, Pb and S isotope data from the Mujicun porphyry Cu–Mo deposit in the northern Taihang Mountains within the Central Orogenic Belt of the NCC. We constrain the timing of magmatism as 144.1 ± 1.2 Ma from zircon U–Pb data on the diorite porphyry that hosts Cu–Mo mineralization. Another U–Pb age of 139.7 ± 1.4 Ma was obtained from an epidote skarn that is located in the contact zone between the porphyry and its wall rocks. These data and five Re–Os molybdenite ages that range from 142.7 ± 2.0 Ma to 138.5 ± 1.9 Ma suggest that magmatism and mineralization occurred in about five million year duration from ~ 143 Ma to ~ 138 Ma. The He, Ar, Pb and, Hf data suggest that magmatism involved recycled Neoarchean lower crustal components, with input of heat and volatiles from an upwelling mantle. The Mujicun porphyry and associated mineralization provide a typical example for magmatism and metallogeny associated with lithospheric thinning in the NCC.     

Chronology and geochemistry of Mesozoic granitoids in the Bengbu area,central China: Constraints on the tectonic evolution of the eastern North China Craton

We performed zircon U–Pb dating and analyses of major and trace elements, and Sr–Nd–Pb isotopes for granitoids in the Bengbu area, central China, with the aim of constraining the magma sources and tectonic evolution of the eastern North China Craton (NCC). The analyzed zircons show typical fine-scale oscillatory zoning, indicating a magmatic origin. Zircon U–Pb dating reveals granitoids of two ages: Late Jurassic and Early Cretaceous (²⁰⁶Pb/²³⁸U ages of 160 Ma and 130–110 Ma, respectively). The Late Jurassic rocks (Jingshan intrusion) consist of biotite-syenogranite, whereas the Early Cretaceous rocks (Huaiguang, Xilushan, Nushan, and Caoshan intrusions) are granodiorite, syenogranite, and monzogranite. The Late Jurassic biotite-syenogranites and Early Cretaceous granitoids have the following common geochemical characteristics: SiO₂ = 70.35–74.56 wt.%, K₂O/Na₂O = 0.66–1.27 (mainly < 1.0), and A/CNK = 0.96–1.06, similar to I-type granite. The examined rocks are characterized by enrichment in light rare earth elements, large ion lithophile elements, and U; depletion in heavy rare earth elements, Nb, and Ta; and high initial ⁸⁷Sr/⁸⁶Sr ratios (0.7081–0.7110) and low ε_Nd (t) values (? 14.40 to ? 22.77), indicating a crustal origin.The occurrence of Neoproterozoic magmatic zircons (850 Ma) and inherited early Mesozoic (208–228 Ma) metamorphic zircons within the Late Jurassic biotite-syenogranites, together with the occurrence of Neoproterozoic magmatic zircons (657 and 759 Ma) and inherited early Mesozoic (206–231 Ma) metamorphic zircons within the Early Cretaceous Nushan and Xilushan granitoids, suggests that the primary magmas were derived from partial melting of the Yangtze Craton (YC) basement. In contrast, the occurrence of Paleoproterozoic and Paleoarchean inherited zircons within the Huaiguang granitoids indicates that their primary magmas mainly originated from partial melting of the NCC basement. The occurrence of YC basement within the lower continental crust of the eastern NCC indicates that the YC was subducted to the northwest beneath the NCC, along the Tan-Lu fault zone, during the early Mesozoic.     

Re–Os ages for molybdenum mineralization in the Fengning region of northern Hebei Province,China: New constraints on the timing of mineralization and geodynamic setting

A recently recognized molybdenum (Mo) metallogenic belt is present within and adjacent to the northern part of the North China Craton (NCC). More than 20 Mo deposits are present in the belt, including the Sadaigoumen and Dacaoping porphyry deposits located in the Fengning region of the northern part of Hebei Province. The Sadaigoumen deposit has a Re–Os molybdenite weighted mean age of 236.5 ± 2.2 Ma (MSWD = 1.4, n = 6), which is more reliable than existing dates and is interpreted as the precise age for formation of the deposit. The Dacaoping Mo deposit is about 100 million years younger, with a Re–Os molybdenite isochron age of 140.1 ± 3.4 Ma (2σ, MSWD = 0.26, n = 5), which is within error of the weighted mean age of 139.4 ± 0.9 Ma. The ages of the two deposits show that there are at least two episodes of Mo porphyry formation in the Fengning region. In combination with the regional geological evolution of this part of the craton margin, we propose that the Triassic Mo event at Sadaigoumen is associated with a collisional event during the closure of the ancient Asian Ocean, whereas the Early Cretaceous Mo event at Dacaoping is associated with lithospheric thinning of the NCC.     

Growth and reworking of the early Precambrian continental crust in the North China Craton: Constraints from zircon Hf isotopes

We synthesize more than 2600 Hf isotope data on the Archean-Paleoproterozoic zircons from the North China Craton (NCC). Recalculation of the data based on single stage and two-stage Hf model ages of the Eastern Block of the NCC shows peak ages of 3902 ± 13 Ma and 3978 ± 18 Ma, respectively, and also small peaks at 3.5–4.0 Ga. The majority of zircon ε_Hf(t) values are positive, suggesting the possibility of the crust and the mantle differentiation at ca. 3.9–4.0 Ga in the Eastern Block of the NCC. Most magmatic zircons from the whole of NCC have their Hf model age range of 2.4–2.9 Ga, and the single stage model ages is cluster at 2698 ± 4 Ma, whereas the two-stage model ages concentrate at 2714 ± 5 Ma, implying that the protoliths were juvenile crustal rocks. The most prominent peak at 2.7 Ga indicates that this period marks the most important stage of the crust-mantle differentiation and crust formation of the NCC. The widespread 2.5 Ga rocks in the NCC and the absence of the 2.5 Ga peaks in Hf model ages are consistent with the partial melting and reworking of the juvenile rocks at 2.5 Ga. Furthermore, the 2.5–1.7 Ga zircon Hf isotope features are also related to the reworking of the crustal rocks. Our results from the integration of a large database suggest that the Eastern Block and the Trans-North China Orogen have undergone similar crust-mantle differentiation and magmatism, leading to the conclusion that the essential cratonization of the North China took place at the end of Neoarchean.     

Discovery of Neoarchean suprasubduction zone ophiolite suite from Yishui Complex in the North China Craton

The Archean tectonic realm of the North China Craton (NCC) is considered in recent models as a collage of several microblocks which were amalgamated along zones of ocean closure during late Neoarchean. Here we report the finding of a dismembered ophiolite suite from the southern margin of the Jiaoliao microblock in the interior of the unified Eastern Block of the NCC. The suite is composed of lherzolite, pyroxenite, noritic and hornblende gabbro, and hornblendite intruded by veins and sheets of leuco granite. Together with transposed layers and bands of metavolcanics and amphibolites, banded iron formation (BIF), and diabase dykes in the adjacent locations, the Yishui complex corresponds well with a dismembered suprasubduction zone ophiolite suite. Clinopyroxene in the pyroxenite and gabbroic rocks is Mg rich and range in composition from augite to diopside. Among orthopyroxenes, those in lherzolite show the highest X_Mg of 0.84–0.85. Plagioclase in hornblende gabbro shows high anorthite content (An_50–64). Calcic amphiboles in the gabbroic rocks range in composition from ferropargasite to ferro-edenite, edenite and pargasite. Spinel inclusions in lherzolite are Cr-rich magnesiospinel. Geochemically, the mafic rocks from Yishui complex show subalkaline basaltic source, whereas the granitoids show volcanic arc affinity. The hornblende gabbro and gabbro, lherzolite and hornblendite show compositional similarity to E-MORB and N-MORB respectively. The lherzolite and hornblendite possess arc-related ultramafic cumulate nature, with overall features straddling the fields of IAT and IAT-MORB. The geochemical features are consistent with evolution in a suprasubduction regime with no significant crustal contamination. The majority of zircon grains in the Yishui suite exhibit magmatic texture and high Th/U ratios. Zircon grains from hornblendite define ²⁰⁷Pb/²⁰⁶Pb upper intercept age of 2538 ± 30 Ma. Zircons from the granite show ages of 2538 ± 16 Ma and 2503 ± 21 Ma, and those from the gabbros yield ages of 2503 ± 16 Ma and 2495 ± 10 Ma. The well defined major age peak at 2500 Ma is broadly coeval with Neoarchean ages reported from the microblocks in the North China Craton. The zircon Lu–Hf data from the Yishui suite display εHf(t) values between − 2.5 and 5.0, with corresponding model ages suggesting magma derivation from Neoarchean juvenile sources together with limited reworked Paleo-Mesoarchean crustal components.Our study is the first report of Neoarchean suprasubduction-type ophiolites from a locality far from the margins of the major crustal blocks and suture zones in the NCC and strengthens the concept that the craton is a mosaic of several microblocks with intervening oceans that closed along multiple subduction zones. We envisage that the amalgamation between the Xuhuai and the Jiaoliao microblocks resulted in the accretion of the Yishui suprasubduction zone ophiolitic assemblages onto the southern margin of the Jiaoliao microblock. The Neoarchean microblock amalgamation in the North China Craton provides new insights into continental growth in the early Earth and confirms that modern style plate tectonics might have been initiated early in the history of our planet.     

Episodic Mesozoic thickening and reworking of the North China Archean lower crust correlated to the fast-spreading Pacific plate

A central target in Earth sciences is to understand the processes controlling the stabilization and destruction of Archean continents. The North China craton (NCC) has in part lost its dense crustal root after the Mesozoic, and thus it is a key region to test models of crust–mantle differentiation and subsequent evolution of the continental crust. However, the timing and mechanisms responsible for its crustal thickening and reworking have been long debated. Here we report the Early Cretaceous Yinan (eastern NCC) adakitic granites, for which major/trace elemental models demonstrate that they are complementary to the analogy of the documented eclogitic relicts within the NCC. Based on their Late Archean inherited zircons, depleted mantle Nd model ages of ∼2.8 Ga, large negative ε_Nd(t) values (−36.7 to −25.3) and strongly radiogenic initial ⁸⁷Sr/⁸⁶Sr ratios (0.7178–0.7264), we suggest that the Yinan adakitic granites were potentially formed by the dehydration melting of a thickened Archean mica-bearing mafic lower crust during the Early Cretaceous (ca. 124 Ma), corresponding to a major period (117–132 Ma) of the NCC Mesozoic intrusive magmatism. Combined previous results, it is shown that the thickening and reworking of the North China Archean lower crust occurred largely as two short-lived episodes at 155–180 Ma and 117–132 Ma, rather than a gradual, secular event. These correlated temporally with the superfast-spreading Pacific plate during the Mesozoic. The synchroneity of these events suggests rapid plate motion of the Pacific plate driving the episodic NCC crustal thickening and reworking, resulting in dense eclogitic residues that became gravitationally unstable. The onset of lithospheric delamination occurred when upwelling asthenosphere heated the base of lower crust to form coeval felsic magmas with or without involvement of juvenile mantle material. Collectively, the circum-Pacific massive crustal production could be attributed to the unusually rapid motion of Pacific at 155–180 Ma and 117–132 Ma.     

Microblock amalgamation in the North China Craton: Evidence from Neoarchaean magmatic suite in the western margin of the Jiaoliao Block

The Archaean Earth is considered to have been characterized by microcontinents that formed, dominantly, through the accretion of oceanic arcs and plateaus. The North China Craton (NCC) provides a typical case where at least seven ancient microcontinental nuclei with distinct lithological features and independent tectonic histories were amalgamated into the cratonic framework at the end of the Archaean. Here we investigate a suite of magmatic rocks developed at the periphery of one of these microblocks, the Jiaoliao Block that forms part of the composite Eastern Block of the NCC. We present petrological, geochemical and zircon U–Pb geochronological data from the Taipingzhai charnockite suite, and associated amphibolites, metagabbros and orthogneisses from the Qianxi Complex. Geochemically the rocks show a wide range of SiO₂ (charnockite suite: 52.57–75.50 wt.%; metagabbro: 43.71 wt.%; amphibolite: 50.24 wt.%; garnet-bearing biotite: 63.73 wt.%), and MgO (charnockite suite: 0.89–5.01 wt.%; metagabbro: 3.99 wt.%; amphibolite: 6.23 wt.%; garnet-bearing biotite: 2.08 wt.%). The composition of the felsic units straddle from diorite through syeno-diorite to granite with both alkalic and subalkalic affinity, with dominantly magnesian composition and arc-related features. Their immobile trace element relationships suggest calc-alkaline affinity. They show positive Pb, Ba, La, Nd, and Gd and negative Nb, Ta, Sr, Th and Ti anomalies with slightly negative anomalies of Ce and Y, attesting to arc-related features. In tectonic classification diagrams, the rocks plot in the VAG + syn-COLG field or the VAG area suggesting subduction-related origin.The dominant population of zircons in all these rocks displays magmatic crystallization features including high Th/U values with core-rims textures indicating subsequent thermal events. The zircon U–Pb data yield upper intercept ages of 2587 ± 10 Ma to 2543 ± 17 Ma and ²⁰⁷Pb/²⁰⁶Pb mean ages of 2578 ± 7.3 Ma to 2536 ± 8 Ma for the charnockite suite, marking the timing of emplacement of the arc magmas. The overgrowth rims as well as discrete neoformed grains are interpreted as dating subsequent metamorphism and yield ²⁰⁷Pb/²⁰⁶Pb ages between 2533 Ma to 2490 Ma. Zircons in the metagabbro preserve upper intercept ages of 2556 ± 20 Ma representing the crystallization age of this rock. The younger ages of 2449 ± 58 Ma (upper intercept age) and 1845 ± 25 Ma (²⁰⁷Pb/²⁰⁶Pb spot age) are interpreted to represent subsequent multiple thermal events in this area. Zircons in the amphibolite preserve the ²⁰⁷Pb/²⁰⁶Pb mean age of 2539 ± 9 Ma, representing the crystallization age of this rock. The garnet-bearing biotite gneiss shows an upper intercept age of 2562 ± 10 Ma (MSWD = 0.66; N = 36) and the ²⁰⁷Pb/²⁰⁶Pb mean age of 2561 ± 9 Ma (MSWD = 0.63; N = 33) which is taken to represent the crystallization age of this rock. Some inherited zircons are also identified with ²⁰⁷Pb/²⁰⁶Pb ages of 2664 ± 26 Ma and 2628 ± 26 Ma. Zircon Lu–Hf data show dominantly positive εHf(t) values and combined with crustal residence ages, the results suggest Mesoarchean to Neoarchean juvenile crust formation in the NCC. We interpret the data presented here to represent a phase of major late Neoarchaean arc magmatism along the western margin of the Jiaoliao Block related to the birth of microcontinental nuclei within the NCC. Our data suggest that the Western and Eastern Blocks might not have existed as discrete crustal blocks, and that the construction of the NCC is a result of the assembly of several microblocks or terranes at the end of Archaean. Similar Archean cratonic nuclei in other regions of the world might have formed part of a primitive supercontinent in the early Earth.     

U–Pb age and Hf isotopes of detrital zircons from the Southeastern North China Craton: Meso- to Neoarchean episodic crustal growth in a shifting tectonic regime

The North China Craton (NCC) represents one of only a few cratonic nuclei on the globe with a geological history extending back to the Eoarchean. However, extensive ca. 2.5 Ga crustal reworking has destroyed a considerable portion of the pre-existing crustal record, hindering the investigation of tectonothermal evolution prior to 2.5 Ga. The Huoqiu Complex (HQC), located at the southeastern margin of the NCC, preserves the vestiges of crustal components that survived the ca. 2.5 Ga tectonothermal events, which provide the opportunity to investigate the Meso- to Neoarchean episodic crustal evolution of the NCC. Here we present results from in-situ detrital zircon U–Pb dating and Hf isotope analyses on zircons from three paragneisses in three drill cores that cut through the basement of the HQC. In combination with published data, the concordant age spectra of the detrital zircons in the paragneisses yield ²⁰⁷Pb/²⁰⁶Pb ages of 2343–3997 Ma that cluster into two principal age populations with peaks at 3015 and 2755 Ma. One zircon grain dated at 3997 ± 8 Ma with 98% concordance provides new evidence for 4.0 Ga components in the NCC. The ε_Hf(t) values of all zircons range from − 5.2 to + 6.5, with most of the spots (n = 31 of 47) showing positive values, indicating at least two episodes of juvenile continental crustal growth at 3.01 Ga and 2.75 Ga. The older episode is recorded only in few ancient cratons, suggesting limited crustal accretion occurred globally at a time of subdued mantle-derived magmatism. In contrast, the younger episode is coincident with a global rise in magmatic activity in the early Neoarchean. The geochemical and geochronological data suggest that the 3.01 Ga juvenile crust was likely generated in an island-arc subduction system, whereas the 2.75 Ga crustal rocks were probably formed during magmatic underplating and subsequent partial melting of lower crustal mafic rocks. Consequently, a tectonic transition is suggested from a compressive to an extensional setting along the southeastern margin of the NCC between 3.01 and 2.75 Ga. This sequence of events heralds a shift, from a mixture of net crustal growth and crustal reworking during multiple short-lived magmatic pulses, to fragmentation and dispersal of the early continental nucleus within 260 Ma.     

Recent advances in the study of the Mesoproterozoic geochronology in the North China Craton

The Mesoproterozoic successions in the North China Craton (NCC) and the Qinling–Qilian–Kunlun Orogens have been revised using the new and highly reliable age data. Many Proterozoic strata in the Qinling–Qilian–Kunlun Orogens, such as the Qinling, Jinshuikou and Beidahe groups that have been ascribed to be Paleoproterozoic are actually of Mesoproterozoic Era. The most significant advances are recent geochronological studies on the Mesoproterozoic stratigraphy and magmatic events in the NCC. The boundary age between the Dahongyu Formation and the overlying Gaoyuzhuang Formation is well constrained to be ∼1600 Ma, corresponding to the boundary age between Statherian and Calymmian. The boundary between the Tieling Formation and the overlying Xiamaling Formation is best positioned at ∼1400 Ma, which is coeval with the boundary between Calymmian and Ectasian, and is about 400 Myrs older than the conventional value of 1000 Ma originally defined by the All China Commission of Stratigraphy. Hence the Jixianian System, including the Gaoyuzhuang, Yangzhuang, Wumishan, Hongshuizhuang and Tieling formations in ascending order, is comparable with the Calymmian System in the International Stratigraphic Chart. The lower boundary of the Changchengian System, the first system of the Mesoproterozoic in China Regional Stratigraphic Chart, also needs revision from the conventional 1800 Ma to ∼1650 Ma well constrained by the zircon U–Pb ages 1673 ± 10 Ma (LA-MC-ICP-MS) and 1669 ± 20 Ma (SHRIMP) of a granite-porphyry dike that was overlain unconformably by the basal conglomerate of the Changzhougou Formation, the first formation of the Changchengian System. Therefore, the earliest Mesoproterozoic sequence in the NCC represented by the Changchengian and Jixianian Systems in the Yanliao Aulacogen is identical to that of the Vindhyan Supergroup in Central Indian and the Riphean Series in Russia. On the other hand, a series of 1.8–1.6 Ga anorogenic magmatic records were well-preserved around the NCC, which marked the initial rifting of the Columbia Supercontinent in the NCC. The magmatic events can thus be subdivided into three phases with peaks at ca 1.77 Ga, ca 1.70 Ga and ca 1.63 Ga, respectively. In addition to 1.8–1.6 Ga magmatic events, some minor volcanic eruptions at ca 1.56 Ga and 1.44 Ga, and wide-spread bi-modal magmatic intrusions at 1.35–1.32 Ga have been recognized in the northern NCC, marking the continued rifting of the Columbia Supercontinent since ∼1.8 Ga.     

Electron microprobe U–Th–Pb monazite dating of the Transamazonian metamorphic overprint on Archean rocks from the Amapá Block,southeastern Guiana Shield,Northern Brazil

The Amapá Block, southeastern Guiana Shield, represents an Archean block involved in a large Paleoproterozoic belt, with evolution related to the Transamazonian orogenic cycle (2.26 to 1.95 Ga). High spatial resolution dating using an electron-probe microanalyzer (EPMA) was employed to obtain U–Th–Pb chemical ages in monazite of seven rock samples of the Archean basement from that tectonic block, which underwent granulite- and amphibolite-facies metamorphism. Pb–Pb zircon dating was also performed on one sample.Monazite and zircon ages demonstrate that the metamorphic overprinting of the Archean basement occurred during the Transamazonian orogenesis, and two main tectono-thermal events were recorded. The first one is revealed by monazite ages of 2096 ± 6, 2093 ± 8, 2088 ± 8, 2087 ± 3 and 2086 ± 8 Ma, and by the zircon age of 2091 ± 5 Ma, obtained in granulitic rocks. These concordant ages provided a reliable estimate of the time of the granulite-facies metamorphism in the southwest of the Amapá Block and, coupled with petro-structural data, suggest that it was contemporaneous to the development of a thrusting system associated to the collisional stage of the Transamazonian orogenesis, at about 2.10–2.08 Ga.The later event, under amphibolite-facies conditions, is recorded by monazite ages of 2056 ± 7 and 2038 ± 6 Ma, and is consistent with a post-collisional stage, marked by granite emplacement and coeval migmatization of the Archean basement along strike-slip shear zones.     

Phanerozoic amalgamation of the Alxa Block and North China Craton: Evidence from Paleozoic granitoids,U–Pb geochronology and Sr–Nd–Pb–Hf–O isotope geochemistry

The North China Craton (NCC) has been considered to be part of the supercontinent Columbia. The nature of the NCC western boundary, however, remains strongly disputed. A key question in this regard is whether or not the Alxa Block is a part of the NCC. It is located in the vicinity of the inferred boundary, and therefore could potentially resolve the issue of the NCC's relationship to the Columbia supercontinent. Some previous studies based on the Alxa Block's geological evolution and detrital zircon ages suggested that it is likely not a part of the NCC. The lack of evidence from key igneous rock units, however, requires further constraints on the tectonic affinity of the western NCC and Alxa Block and on the timing of their amalgamation.In this study, new zircon U–Pb age and Hf–O isotopes and whole-rock geochemical and Sr–Nd–Pb isotopic data for the Paleozoic granitoids in or near the eastern Alxa Block were used to constrain the petrogenesis of these rocks and the relationship between the Alxa Block and NCC. Secondary ion mass spectrometry (SIMS) U–Pb zircon dating indicates that the Bayanbulage, Hetun, Diebusige and South Diebusige granitoids were formed at ca. 423 Ma, 345 Ma, 345 Ma and 337 Ma, respectively. The Late Silurian (Bayanbulage) quartz diorites have variable SiO₂ (58.0–67.9 wt.%), and low Sr/Y (20–24) values, while the Early Carboniferous (Hetun, Diebusige and South Diebusige) monzogranites have high SiO₂ (71.5–76.7 wt.%) and Sr/Y (40–94) values. The Late Silurian quartz diorites display relatively homogeneous and high zircon δ¹⁸O (8.5–9.1‰) and ε_Hf(t) (− 8.6 to − 5.3) values, high whole-rock ε_Nd(t) values (− 9.2 to − 7.6) and highly radiogenic Pb isotopes (²⁰⁶Pb/²⁰⁴Pb = 18.13–18.25), whereas the Early Carboniferous monzogranites exhibit relatively low and variable zircon δ¹⁸O (5.7–7.2‰) and ε_Hf(t) (− 23.1 to − 7.4) values, low whole-rock initial ⁸⁷Sr/⁸⁶Sr (0.7043–0.7070) and ε_Nd(t) (− 19.1 to − 13.5) values and variable Pb isotopes (²⁰⁶Pb/²⁰⁴Pb = 16.06–18.22). The differences in whole rock Nd model ages and Pb isotope compositions of the Paleoproterozoic–Permian rocks in either side of the west fault of the Bayanwulashan–Diebusige complexes suggest that the Alxa Block is not a part of the NCC, and that the western boundary of the NCC is probably located on this fault. Furthermore, the linear distribution of the Early Paleozoic–Early Carboniferous granitoids, the high zircon δ¹⁸O values of the Late Silurian quartz diorites, the Early Devonian metamorphism and the foreland basin system formed during the collision between the Alxa Block and the NCC indicate that a Paleozoic cryptic suture zone likely existed in this area and records the amalgamation of the Alxa Block and North China Craton. Together with detrital zircon data, the initial collision was considered to have possibly occurred in Late Ordovician.     

Tectonic implications of Early Cretaceous low-Mg adakitic rocks generated by partial melting of thickened lower continental crust at the southern margin of the central North China Craton

This paper reports new whole-rock geochemical, Sr–Nd–Pb isotopic, and zircon U–Pb and Hf isotopic data for Early Cretaceous intrusive rocks in the Sanmenxia–Houma area of central China, and uses these data to constrain the petrogenesis of low-Mg adakitic rocks (LMAR) and the spatial extent of the influence of the deeply subducted Yangtze slab during the Triassic evolution of this region. New zircon laser-ablation inductivity coupled plasma mass spectrometry (LA-ICP-MS) U–Pb data indicate that the early- and late-stage southern Quli, Qiligou, and Gaomiao porphyritic quartz diorites, the Canfang granodiorite, and the northern Wangmao porphyritic quartz monzodiorite were emplaced during the Early Cretaceous (~ 130 Ma) and the late Early Cretaceous (~ 116 Ma). These rocks are characterized by high Na₂O/K₂O, Sr/Y, and (La/Yb)_n ratios as well as high Sr concentrations, low Mg^# [molar 100 × Mg/(Mg + Fe^2 +_tot)] values, and low heavy rare earth element and Y concentrations, all of which indicate an LMAR affinity. The samples have relatively high initial ⁸⁷Sr/⁸⁶Sr ratios (0.7054–0.7095), and low ε_Nd(t) (− 11.90 to − 22.20) and ε_Hf(t) (− 16.7 to − 32.7) values, indicative of a lower continental crust origin. The presence of Neoproterozoic (754–542 Ma) and inherited Late Triassic (220 Ma) metamorphic zircons within the late Early Cretaceous LMAR and the relatively high ²⁰⁶Pb/²⁰⁴Pb ratios of these rocks suggest that they formed from primary magmas derived from partial melting of Yangtze Craton (YC) basement material that had undergone ultrahigh-pressure metamorphism. In contrast, the presence of Paleoproterozoic and Archean inherited zircons within early Early Cretaceous LMAR in this area and the relatively low ²⁰⁶Pb/²⁰⁴Pb ratios of these rocks are indicative of derivation from primary magmas generated by partial melting of the thickened lower continental crust of the North China Craton (NCC). These rocks may have formed in an extensional environment associated with the upwelling of asthenospheric mantle material. The presence of YC basement material within the NCC in the Sanmenxia–Houma area suggests that the deeply subducted Yangtze slab influenced an area of ~ 100 km in lateral extent within the southern margin of the central NCC during the Triassic.