Southern Margin Of North China Craton Research Articles

An Ediacaran glacial deposit in southern margin of the North China Craton: The Luoquan Formation—sedimentology, geochronology and provenance

The end of the Neoproterozoic global ice age has promoted the evolution of the Earth's surface system and initiated the ‘Great Explosion of Life’. Glaciation deposits provide valuable insights into the extreme climate conditions. In the southern margin of the North China Craton (NCC), an Ediacaran glacial deposit named ‘Luoquan Formation’ has been recently described in Luonan County, Shaanxi Province. It has significant characteristics of dark grey and black glacial deposits. Through extensive research in sedimentology, geochemistry and geochronology, the glacial sedimentary evolution sequence of the Luoquan Formation has been established. This research also help to define the age of the formation and reveal its provenance and sedimentary environment. The study reveals that four lithofacies associations were identified in the Luoquan Formation: diamictites, carbonates, dropstone‐bearing rock and black shale. The Luoquan Formation has experienced three cycles of glacial advance–retreat. Sedimentological evidence suggests that the sedimentary environments of the Luoquan Formation evolved from subglacial (diamictite) to intertidal, then to intertidal lagoon, or from subglacial deposits to shoreface (inner shelf, subtidal), then to deep water basin and fine‐grained turbidite and ice‐rafting. The age of the Luoquan Formation is estimated to be 562–550 Ma constrained by indirect chronological and paleontological data, maybe representing an Upper Ediacaran glaciation that occurred later than the Gaskiers glaciation. The overall age profile of detrital zircons from the Luoquan Formation can be divided into six groups, ranging from 1.1 to 1.6, 1.85 to 1.95, ~2.1, ~2.3, ~2.5 and 2.65 to 2.9 Ga. These age groups are consistent with the Archean to Meso‐Neoproterozoic magmatic–tectonic events in the southern margin of NCC, indicating they are ascribed to an origination directly from the southern margin of NCC. The Luoquan Formation exhibits the characteristics of isochronous and different sedimentary facies, with the glacial front moving from north to south. The discovery of Luoquan Formation in Lianshuigou section not only reflects the important significance of the restoration and reconstruction of the Ediacaran ice age, paleoenvironment and palaeogeography of the NCC but also provides significant evidence to support the further subdivision and correlation within the Ediacaran glacial deposits globally.

Petrogenesis and geodynamic implications of the Cretaceous anorogenic granitoids in east Qingling orogen

We report systematical zircon U–Pb datings, Hf isotopic data, major and trace element date on the Zhangshiying (ZSY) and the Taishanmiao (TSM) two plutons at the southern margin of the North China Craton (NCC), in order to investigate their petrogenesis and geological evolution. LA-ICP-MS U–Pb zircon of the ZSY and TSM granites dating yield a weighted mean 206Pb/238U age of 122.8 ± 1.5 Ma and 112.1 ± 3.2 Ma. The ZSY quartz syenite enriched in SiO2 (65.59–68.1 wt.%), Al2O3 (15.39–15.64 wt.%), high Sr (468–666 ppm), Sr/Y (35–45), (La/Yb)N (20.1–22.1) ratios, low Y(13.1–16.6 ppm), Yb (1.46–1.77 ppm), depleted in Nb, Ta, P, Ti, Mg, Y and negligible Eu anomalies, which suggesting that the quartz syenite are similar to adakitic rocks. Zircons from this pluton give εHf(t) values from −17.6 to −5.7 with an average of −15.2, and their TDM2 ages (1.29–1.91 Ga) are much younger than the basement rocks of the south margin of the NCC, which indicate that the ZSY quartz syenite were generated by partial melting of thickened lower crust with minor involvement of mantle-derived materials. The TSM pluton has characteristic of A-type granite, such as, high SiO2 (69.7–71.87 wt.%), total alkalis (Na2O + K2O = 8.5 to 9.41 wt.%), HFSE (Zr, Nb, Ga, Y), low CaO (0.27–1.25 wt.%), Ba, Sr and Eu. Their εHf(T) values ranges from −12.4 to −1.6 with an average of −7.6 and TDM2 ranges from 1.10 to 1.63 Ga with an average of 1.38 Ma. We propose that the TSM granites results from partial melting of tonalitic crustal sources with a plagioclase-rich residual at high temperatures and low pressure. Materials input from the mantle also is involved for the higher εHf(t) values than tonalitic crustal at the southern margin of NCC and high temperatures. Our results suggested that the thickened LCC at the south margin of the NCC is still existence before the intrusive of the ZSY adakitic rocks (∼123 Ma). During the intrusive of the TSM granites (∼112 Ma) it turns to extensional environment. This extensional event reflects the background of lithospheric thinning and decratonization of NCC.

A synthetic geochemical and geochronological dataset of the Mesoproterozoic sediments along the southern margin of North China Craton: Unraveling a prolonged peripheral subduction involved in breakup of Supercontinent Columbia

Controversial issues on the Paleo-Mesoproterozoic tectonic setting of the southern margin of North China Craton (NCC) restricted our understanding of its role in breaking up the Columbia/Nuna Supercontinent. Existing models are still arguing on whether the southern margin was an intra-continental rift or active continental margin. Previous studies mainly focused on the magmatic records in the Paleoproterozoic Xiong’er Group, while the overlain sedimentary series and their depositional nature and the related tectonic environment were not yet well constrained. In this study, we scrutinized the comprehensive geochronological and geochemical dataset for the Mesoproterozoic sedimentary rocks along the southern margin of NCC. Our new results, together with the previous geochemical data show that the interior part of NCC southern margin (e.g. Wufoshan Group of the Song-Ji area) is dominated by the materials from the mature continental crust. Approaching the marginal area of southern NCC (e.g. Gaoshanhe and Guandaokou Groups of the Xiaoqinling-Luanchuan area), sediments are more enriched in magmatic arc fragments and unfractionated materials. Detrital zircon geochronological results revealed a progressive younging tendency from the northern Song-Ji to southern Xiaoqinling-Luanchuan areas. Together with the newly-reported zircon hafnium data, the synthesized dataset in this study favors the hypothesis that the southern NCC during the Paleo-Mesoproterozoic was in an active continental arc setting under a prolonged peripheral subduction regime, which was surrounding the marginal areas of the Columbia/Nuna Supercontinent.

Zircon U-Pb geochronology of tuffite beds in the Baishugou Formation: Constraints on the revision of Ectasian System at the southern margin of the North China Craton

The Xiamaling Formation of 1.4–1.35 Ga in Jixian Section and adjoining areas represents a unique Ectasian Period (Mesoproterozoic) sedimentary sequence in the North China Craton (NCC). Studies carried out during the last decade have contributed significantly in improving our understanding about the Ectasian sedimentation tectonics in the NCC during this transitional interval between the breakup of Supercontinent Columbia and the assembly of Rodinia. The present study reports, for the first time, tuffite beds interlayered with carbonaceous-siliceous slate-phyllite in the upper Baishugou Formation (western Henan Province), at the southern margin of NCC. The LA-MC-ICPMS U-Pb geochronology of zircons from two tuffite samples has yielded almost identical ages of 1330±10 Ma (MSWD=0.43, N=38) and 1332±10 Ma (MSWD=0.90, N=24), that constrain a 1.33 Ga depositional age (Ectasian Period) for the Baishugou Formation. A close similarity in lithological characteristics and their respective superimposed lithostratigraphic relationships of the Baishugou and Xiamaling formations, underline a comparable depositional environment for them. The high-precision geochronology data on the Baishugou Formation would stimulate a relook into the Meso-Neoproterozoic chronostratigraphic framework of the NCC, and further research would lead to a comprehensive understanding of the geological evolution of the NCC during Ectasian Period and its correlation with analogous global events.

Geochronology, Geochemistry and Hf Isotope of the Late Mesozoic Granitoids from the Lushi Polymetal Mineralization Area: Implication for the Destruction of Southern North China Craton

The North China Craton (NCC) is the best example of an Archean craton that has lost its stability in the Late Mesozoic. Although the cratonic destruction is generally considered to have occurred in the Eastern Block and reached a peak in the Early Cretaceous, the exact areal extent of cratonic destruction is debated, especially the southern and northern margin of the NCC. Here we report geochronology, geochemical and Hf isotopic data of the Late Mesozoic granitoids from Lushi polymetal mineralization area (LPMA) in the southern margin of NCC. These results provide new insights into the destruction in the southern margin of the NCC during the Late Mesozoic. Zircon U-Pb dating indicates that eight granitoids intruded in the Late Jurassic to Early Cretaceous (136.8-154.1 Ma), respectively. Geochemical signatures define these granitoids being A-type or I-type granite that formed in an extension setting. In addition, Hf isotopic compositions of zircons from these granitoids vary in a relatively large range, with eHf(t) values and TDM2 ages ranginge from -26.1 to +15.2 and 215 to 2 849 Ma, respectively. The parental magmas were likely derived from diverse sources, including materials of the partial melting of ancient lower crust and mantle-derived mafic magmas in various proportions. Combining with previous studies on the contemporaneous magma-tectonic activities in circum of NCC, we suggest that the rim of NCC was already unstabilized from the Late Jurassic in the LPMA. The subduction of the Paleo-Pacific Plate was the main trigger to the destruction of the southern margin of NCC, which was responsible for the lithospheric extension and thinning, extensive magmatism and mineralization.

The multiple granitic magmatism in the giant Huayangchuan uranium polymetallic ore district: Implications for tectonic evolution of the southern margin of North China Craton in the Qinling Orogen

The giant Huayangchuan U–Nb–Pb deposit in the Qinling Orogen is a newly verified carbonatite-hosted deposit in the southern margin of the North China Craton (NCC), central China. Granitic magmatism is extensively developed in the Huayangchuan deposit area, but their ages and petrogenesis are not well constrained. The exposed granitic rocks are mainly biotite monzogranite porphyry, granite pegmatite, granodiorite, and biotite monzogranite with zircon U–Pb ages of 1808 ± 10 Ma, 1807 ± 14 Ma, 233 ± 1.4 Ma, and 132 ± 0.6 Ma, respectively. The Paleoproterozoic biotite monzogranite porphyry belongs to shoshonite and metaluminous series, showing enrichment of LREE and LILE and depletion of HREE and HFSE, with high Zr + Y + Nb + Ce values and Ga/Al ratios, which are consistent with A-type granite. Whereas, the contemporaneous granite pegmatite dykes with weak mineralization are also cala-alkaline to shoshonite and peraluminous series, enriched in Rb, Ba, and LREE, and depleted in Nb, Ta, Ti and HREE. The shoshonite and weakly peraluminous Triassic granodiorite is slightly enriched in LREE with flat HREE patterns, enriched in Ba and Sr and depleted in Nb, Ta, P, and Ti, with similar geochemical characteristics to adakite-like rocks. The Early Cretaceous biotite monzogranite is characterized by LREE enrichment and flat HREE patterns, belonging to shoshonite and metaluminous to weakly peraluminous I-type granite, with U and LILE enrichment, and HFSE-depleted. The high initial 87Sr/86Sr ratios and enriched Nd (εNd(t) = −17.5 to −17.1) and Hf (εHf(t) = −33.2 to −14.6) isotopes reveal that the Huayangchuan granitic rocks are obviously sourced from crustal-derived magmas. Combined with regional geology and this study, we proposed that: (1) the Paleoproterozoic biotite monzogranite porphyry and granite pegmatite were generated from ancient lower crust during post-collisional extension setting; (2) the granodiorite was likely sourced from partial melting of thickened lower crust with pelagic sediments materials addition during the Triassic although the mineralization-related carbonatite having similar age with granodiorite may derive from mantle; and (3) the Early Cretaceous biotite monzogranite was mainly sourced from the partial melting of lower crust induced by the underplating of the mafic magma. We suggest that the first phase of magma occurred in the Huayangchuan district during the Paleoproterozoic following the amalgamation of the Eastern and Western blocks along the Trans-North China Orogen. Since the Mesozoic, the ongoing northward subduction of the Yangtze Craton (YZC) resulted in the crust thickening, developing the Triassic granitic magmatism and major mineralization associated with carbonatite. The widespread Cretaceous granite and deposit in the southern margin of NCC indicate that intracontinental extension and lithospheric thinning occurred in response to the tectonic regime transition from NS-trending to EW-trending subduction.

Age, origin and significance of the Wugang BIF in the Taihua complex, Southern North China Craton

The Wugang BIF hosted in a Neoarchean Taihua complex (TH) in the Wugang area, at the southern margin of the North China Craton (NCC), is one of the important iron ore in Central Plain. In this study, we report new data on whole-rock compositions of iron ore sample, U-Pb isotopic compositions of detrital zircon from metasedimentary rocks (one BIF sample and two associated garnet paragneisses). In combination with literature data, they yielded a minimum age peak of 2.60 Ga for 110 detrital zircons of magmatic origin from the Tieshanmiao Formation (dominantly BIF-bearing strata) that we interpret as an upper limit age for the Wugang BIF depositional age. Thirty-six detrital zircons of metamorphic origin gave a maximum metamorphic age peak of 2.45 Ga, reflecting the lower limit age. Thus the depositional ages of Wugang BIF can constrained at 2.60–2.45 Ga. The presence of proximal detrital zircons in BIF samples, river-flux contributions, and some BIF samples have true negative Ce anomalies suggest that they were deposited in near-shore continental-shelf or back-arc basin environments, coinciding with that they are typically interbedded with marble, quartz arenite and other metasedimentary rocks, but lack of volcanic material. In particular, both hanging wall and footwall for Tiegukeng BIF orebody from Tieshanmiao Formation are marble, except for several diopside dykes (1943 Ma), orebody is dominantly composed of pyroxene-rich BIF, quartz-rich BIF and other metasedimentary rocks. The Wugang BIF displayed the weak positive Eu/Eu∗(SN) anomalies (average 1.74), associated with the low Cr (∼10 ppm) and V (<5 ppm) contents, similar to other Superior-type BIFs worldwide. All lines of evidence suggest that the Wugang BIF belongs to Superior-type. In combination with features of coeval counterpart, such as Huoqiu BIF and Xincai BIF in its southeast, it can be assumed that a relatively large Superior-type BIF belt presented at proto-continental margin, they deposited on proto-continental shelf or back-arc basin environments during Neoarchean-Paleoproterozoic. Geochemical evidence propose that the Wugang BIF originated from chemical deposition of carbonate and silica facies, its iron sourced from the mixture of seawater, hydrothermal fluid and river-flux, with trace continental detritus. Consequently, it is reasonable to predict that a great variety of BIFs may distribute between Wugang and Huoqiu area at the southern margin of NCC.

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 439Ma) formed during the Late Carboniferous and Early Permian, the Xiashihezi Formation (276Ma) during the Early Permian, the Shangshihezi (376Ma) and Shiqianfeng (279Ma) formations during the Middle–Late Permian, the Ermaying Group (232Ma) and Shangyoufangzhuang Formation (230 and 210Ma) during the Late Triassic, the Jurassic unnamed formation (154Ma) during the Late Jurassic, and the Cretaceous unnamed formation (158Ma) 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.

U-Pb ages and Hf isotopes for detrital zircons from quartzite in the Paleoproterozoic Songshan Group on the southwestern margin of the North China Craton

In situ U-Pb dating and Lu-Hf isotopic analysis were carried out for detrital zircons from quartzite in the Paleoproterozoic Songshan Group on the southern margin of the North China Craton (NCC). The results provide further constraints on the crustal formation and evolution history of NCC. Four 207Pb/206Pb age populations were obtained from 99 analyses, with clusters at ∼3.40 Ga, 2.77–2.80 Ga, ∼2.50 Ga and 2.34 Ga, respectively. The 3.40 Ga old zircons have similar Hf isotopic compositions to those from Archean rocks in the Jidong and Anshan areas of NCC. However, crustal remnants older than 3.6 Ga have been identified in the southern margin of NCC, the South China Craton, the northwestern part of the Qinling Orogen and its adjacent area. Thus, it is not easy to trace the source rock from which the 3.40 Ga detrital zircons were derived. It can be inferred that the crustal remnants older than 3.40 Ga might have been widely distributed in the North China Craton. The 2.77–2.80 Ga zircons make up a relatively small proportion and have the highest eHf (t) values (up to 6.1±1.6), consistent with the Hf isotopic composition of the depleted mantle at 2.83 Ga. Their single-stage Hf model age of 2.83 Ga is close to their crystallized age, suggesting that their source rocks were extracted from the contemporaneous depleted mantle. The ∼2.50 Ga zircon grains constitute about 85% of the total grain population and their Hf isotopic compositions indicate major growth of juvenile crust at ∼2.50 Ga but minor reworking of ancient crust. The youngest zircon dated in this study gave an U-Pb age of 2337±23 Ma, which can be considered the maximum depositional age of the formation of the Songshan Group.