Search

Research on the Zanhuang Complex has been one of the hotspots in the Neoarchean–Palaeoproterozoic tectonic evolution of the Trans‐North China Orogen (TNCO) in the North China Craton (NCC). Here, we present data from petrology, geochemistry, zircon U–Pb geochronology, and Lu–Hf isotopes on a suite of granite, diorite, TTG gneiss, and amphibolite in the Zanhuang Complex to characterize these rocks and understand their genesis. Zircon U–Pb data yield magmatic ages of 2,607 Ma for granite, 2,599 Ma for diorite and 2,561 Ma for TTG gneiss, with subsequent thermal event ages of 2,530 and 2,471 Ma. Lu–Hf isotopes show εHf(t) values ranging from 0.04 to 7.11 and crustal model ages of 2,700–3,100 Ma for the diorite, indicating a Meso‐ to Neoarchean mantle source with minor input of crustal components. The granite and TTG gneiss have the characteristics of volcanic‐arc granite, with low Sr/Y and (La/Yb)N, high Cr and Ni contents, positive Pb and K anomalies and negative Nb, Ta, P, and Ti anomalies. The amphibolite and diorite are similar to island arc basalt, with low K2O, Sr/Y, (La/Yb)N, and high FeOT, positive Pb anomaly, negative Nb, Ta, and Ti anomalies and absence of obvious Ce anomaly. These signatures indicate that these rocks were likely formed in a subduction setting. We have proposed a model of subduction–collision process in the TNCO, including subduction at ca. 2.70–2.55 Ga, arc–continent collision at ca. 2.55–2.45 Ga, extension and rifting at ca. 2.30–2.05 Ga, and continent–continent collision at ca. 1.90–1.75 Ga. Our results are consistent with the previous models on the tectonic evolution in the NCC and provide further insights into the Neoarchean–Palaeoproterozoic tectonic history of the craton. [ABSTRACT FROM AUTHOR]

Granite–greenstone successions and associated tonalite–trondhjemite–granodiorite (TTG) suites constitute dominant components of Precambrian cratons. Here, we present petrology, geochemistry, zircon U–Pb geochronology, and Lu–Hf isotopes on monzonite, granodiorite, granite, and amphibolite from the Dengfeng Complex in the southern part of the North China Craton (NCC). Zircon U–Pb data yield weighted mean 207Pb/206Pb ages of 2498 ± 6 Ma for monzonite, 2481 ± 16 Ma for granodiorite, and 2475 ± 21 Ma for granite. Lu–Hf isotope systematics show εHf(t) values ranging from 1.3 to 6.7 and crustal model ages ( T DM C ) in the range of 2584–2934 Ma for the rocks. The monzonite, granodiorite, and granite show moderate total rare-earth element (REE) contents, enrichment in light REEs (LREE) and depletion in heavy REEs (HREE), negative Nb, Ta, and Ti anomalies, high Al2O3, Sr/Y, and (La/Yb)N ratios, with low Cr and Ni, indicating that the magma was possibly sourced from partial melting of the lower crust. The geochemical features of amphibolites are characterized by low SiO2, Na2O, K2O, Sr/Y, (La/Yb)N and high FeO, low total REEs values, limited LREE/HREE fractionation, and absence of obvious Ce anomaly, showing similarity to island arc magmatic rocks. Our results are consistent with the model of subduction and arc–continent collision in the Trans-North China Orogen during the Neoarchean to Paleoproterozoic. [ABSTRACT FROM AUTHOR]

Potassic magmatic rocks provide significant insights in understanding of mantle composition, evolution, and interaction with crust. Potassic magmatism along the Jinshajiang–Ailaoshan Paleo‐Tethyan suture has drawn much attention. Whereas igneous intrusion in the Simao terrane, west to Jinshajiang–Ailaoshan potassic magmatic belt has rarely been investigated. Hence, we present zircon U–Pb ages and Lu–Hf isotope and whole‐rock geochemistry for the Lianhuashan pluton. Zircon U–Pb dating from monzonite and quartz monzonite porphyry yield ages of 33.6 ± 0.2 and 33.5 ± 0.3 Ma, respectively. Monzonites are characterized by high K2O (4.93–5.16%) and K2O/Na2O (1.46–1.71), high Y (22.90–23.80 ppm), and Yb (1.87–2.21 ppm), relatively enrichment of light rare earth element (LREE). Zircons from monzonites show εHf(t) values ranging from −1.1 to +0.6 and crustal model ages (TDMC) between 1.04 and 1.15 Ga. These geochemical features suggest that parent magmas of the rocks originated from a metasomatized lithospheric mantle. Quartz monzonite porphyries are characterized by high Sr (836.00–1,529.00 ppm), Sr/Y (70.85–99.93) and La/Yb (32.31–49.83), low Y (11.80–15.60 ppm), and Yb (0.95–1.30 ppm), enrichment in LREE and depletion in heavy rare earth elements (HREE). Quartz monzonite porphyries have higher Mg#, MgO, Ni, and Cr contents than the lower crust‐derived adakite‐like rocks. It is suggested that they were derived by variable degree of mixing between lower‐crustal melts and mafic magmas. Based on petrology and geochemistry features, the following evolution process are concluded. During the Neoproterozoic, metasomatic‐enriched mantle magma resulted from the bisubduction of oceanic plate; meanwhile, the crust thickened, and juvenile lower crust formed. During late Eocene, hot asthenosphere upwelled and K‐rich mafic magmas resulted from the decompression of delamination, followed by magmatism emplacing, crystallizing, and the forming of the Lianhuashan pluton. [ABSTRACT FROM AUTHOR]

As the north part of Simao Terrane, Lanping Basin is located between the Sanjiang Tethys Orogen (STO) and Yangtze Block, also the junction zone between the Gondwanaland and Cathaysian old land (Pan Huaxia mainland), which includes Yangtze and Cathaysian Blocks. The aim of this study is to decipher the provenance of the sedimentary units in the Lanping Basin and affiliation of Simao Terrane by the U-Pb ages, Hf isotope of detrital zircons and whole-rock geochemistry. The whole-rock geochemistry and the mineral composition indicate that most of the Triassic–Paleocene sedimentary rocks are derived from the upper crust and exhibit recycled orogen features. The detrital zircon U-Pb ages from the North Simao Terrane are consistent with the magmatic events during Early Neoproterozoic and Permian in the Western Yangtze Block. And the detrital zircons ages from North Simao Terrane show same distribution features as the Permian–Triassic magmatic rocks, which are distributed in the Simao Terrane and along major sutures. These comparisons suggest that the clastic sediments in Lanping Basin (North Simao Terrane) are derived from Early Neoproterozoic and Permian magmatic rocks from Western Yangtze Block, Permian–Triassic magmatic rocks from Simao Terrane, along Jinshajiang, Garz-Litang and Ailaoshan Sutures. The comparison of the detrital zircon age distributions shows that Simao Terrane and Yangtze Block exhibited similarity tectonic setting in the evolution history, especially during Paleoproterozoic–Late Paleozoic. This suggests that the Simao Terrane is part of Cathaysian old land, although Simao Terrane was separated from Yangtze Block for short period during Early Paleozoic. Besides, the Hf mapping, stratigraphic succession, paleogeography and paleomagnetism in SW China support that Simao Terrane has a Cathaysian old land-affinity, rather than one involving Gondwanaland. [ABSTRACT FROM AUTHOR]

• Zircon U–Pb ages range from 2753 ± 37 to 2476 ± 18 Ma in the Luxi Terrane. • Greenstone was derived from the Meso- to Neoarchean mantle contaminated by the crust. • TTGs were sourced from a Meso- to Neoarchean juvenile crust with older basement reworking. • Initial crustal growth at ca. 2750–2600 Ma, followed by more voluminous growth at ca. 2550–2450 Ma. Tonalite–trondhjemite–granodiorite (TTG) suites constitute dominant components of Precambrian continental crust and provide important insights into the crustal evolution history of the early Earth. Here we investigate a suite of TTGs and associated greenstones from the Luxi Terrane in the south–eastern part of the North China Craton (NCC). We present data from petrology, geochemistry, zircon U–Pb geochronology and Lu–Hf isotopes to characterize these rocks and understand their genesis. Mineral assemblage in the greenstones and TTGs suggests that the rocks have undergone amphibolite–facies metamorphism with regression under greenschist–facies. Zircon U–Pb data from the magmatic grains yield upper intercept ages of 2753 ± 37 and 2582 ± 40 Ma for greenstone, 2552 ± 13 Ma for TTG gneiss and 2476 ± 18 Ma for tonalite, and weighted mean 207Pb/206Pb age of 2507 ± 22 Ma for granodiorite. Lu–Hf isotope systematics show ε Hf (t) values ranging from −2.13 to 7.29 and crustal model ages (TC DM) in the range of 2603–3125 Ma for the TTGs, whereas the ε Hf (t) values are up to 8.53 with TC DM ages of 2644–3006 Ma for the greenstone. The results suggest that the protolith for the greenstone was derived from a Meso- to Neoarchean mantle contaminated by the crust source, whereas the TTGs were mostly sourced from juvenile crustal sources with reworking of older basement. The geochemical features of greenstone are similar to island arc basalt, with low Na 2 O, K 2 O and TiO 2 , low total rare earth elements (REEs) values, relative enrichment in light REEs and depletion in heavy REEs absence of obvious Ce anomaly, and negative Nb, Ta and Ti anomalies. The TTGs show similar features, except for the high K 2 O content and moderate total REEs values. We propose that the greenstone likely represent a part of the early and initial crustal growth at ca. 2750–2600 Ma, and the TTGs were generated subsequently at ca. 2550–2450 Ma. Our results are consistent with the previous models on the crustal growth models in the NCC and provide further insights into the Neoarchean to Paleoproterozoic tectonic history of the craton. [ABSTRACT FROM AUTHOR]

• Zircon U-Pb ages of 2776–2771 Ma mark a major phase of crust building. • Paleoproterozoic metamorphism dated as 1922–1915 Ma. • Amphibolite derived from partial melting of a metasomatic mantle source. • TTG gneiss derived from partial melting of juvenile lower crust. • Archean-Paleoproterozoic crustal accretion and reworking in the southern margin of the NCC. The North China Craton (NCC) preserves important records of Archean-Paleoproterozoic crustal evolution. Here we present results from petrology, geochemistry, zircon U-Pb dating and Lu-Hf isotopes of the Taihua Complex (THC) from the southern part of the NCC. Zircon U-Pb dating of the amphibolite yields the ages of 2776–2771 Ma representing the formation age, marking a major phase of late Archean crustal growth in the NCC. The 1922–1915 Ma ages represent the Paleoproterozoic metamorphism associated with the collisional assembly between the Eastern and Western Blocks. The amphibolites are characterized by low SiO 2 , Na 2 O + K 2 O, and Nb/Y, indicating a sub-alkaline basaltic protolith. These rocks show relatively high LILE/HFSE and LREE/HREE ratios, similar to E-MORB, low [Nb/La] PM , negative Nb-Ta anomalies and positive ε Hf (t) values indicating partial melting of a metasomatic mantle source. The TTG gneisses are characterized by high SiO 2 , Sr/Y, (La/Yb) N , Nb/Ta, Zr/Sm and Zr/Hf ratios, and low MgO, Cr, Ni, Y, Gd/Yb and Dy/Yb ratios, with positive Eu anomalies, indicating partial melting of juvenile lower crust with garnet-amphibolite residue. Our data are consistent with a tectonic setting within a volcanic arc in a convergent margin. Our study on the THC contributes to the Archean-Paleoproterozoic crustal accretion and reworking history along the southern margin of the NCC. [ABSTRACT FROM AUTHOR]