Northeastern North China Craton Research Articles

Neoarchean granitoid magmatism and geodynamic process in the northeastern North China craton

The composition of Archean granitoid rocks changed from predominantly tonalite-trondhjemite-granodiorite (TTG) gneisses in the early Archean (4−3 Ga) to diversified granitoid rock assemblages in the late Archean (3.0−2.5 Ga), marking a crucial transformation in the geodynamic processes of early Earth. However, the reason for this major transition remains enigmatic because the petrogenetic features of different granitoid assemblages and their crust-mantle interactions during different periods are poorly understood. We use variations in the spatial-temporal distribution, lithological association, chemical composition, and petrogenesis of Neoarchean (2.7−2.5 Ga) granitoids and inferred correlative crust-mantle interactions in the Eastern Liaoning Range (ELR) of the northeastern North China craton to explore this geodynamic transition. The early Neoarchean (ca. 2.7 Ga) ELR granitoids were dominated by TTG gneisses, and the late Neoarchean (2.6−2.5 Ga) ELR granitoid typology and compositions became more complex, changing into TTGs and more K2O-rich granitoid rocks. The TTGs can be subdivided into a high-Ca group and a low-Ca group: The 2.71−2.68 Ga high-Ca group TTG magma originated from partial melting of subducted juvenile oceanic crust, and the low-Ca group TTG magma was derived from fractionation crystallization of the high-Ca group TTG magma. The chemical composition of the magmatic sources played a dominant role on the 2.60−2.50 Ga TTG magmatism: the high-Ca and low-Ca group TTG magmas came from low-K mafic rocks and tonalites, respectively. The 2.58−2.49 Ga K2O-rich granitoids can be divided into three petrogenetic series: (1) The high-Ca-Mg group K2O-rich granitoid magma originated from partial melting of high-K mafic rocks, (2) the low-Ca-Mg group K2O-rich granitoid magma was derived from partial melting of sedimentary rocks, and (3) the transition group K2O-rich granitoid magma was sourced from metagreywackes. The 2.71−2.68 Ga TTGs were generated in an island arc belt, and subducted slab melting and subsequent magmatic differentiation were the dominant mechanisms of the TTG magmatism. The 2.60−2.50 Ga diversified granitoids were formed in the oceanic-continental subduction process under the active continental margin; the complicated oceanic slab subduction and arc-arc and arc-continent collisions contributed to the diversity of late Neoarchean granitoid magmatism.

Late Neoarchean-early Paleoproterozoic K-rich granitoid rocks and mafic dykes from the Liaodong Bay Depression, Bohai Sea Basin: Implications for cratonization of the North China Craton

Late Neoarchean to early Paleoproterozoic potassic granites and mafic dykes are widely distributed across the Eastern Block (EB) of the North China Craton (NCC), which provide important information about the geodynamic origin and tectonic evolution of Archean terranes. Here, we are first to report the zircon U–Pb–Hf isotopic and whole-rock compositions of potassic granites and mafic dykes from the Liaoxi Rise of the Liaodong Bay Depression (LBD) in the offshore Bohai Sea Basin (OBSB) of the northeastern NCC. The potassic granites have crystallization ages of 2499–2460 Ma and are characterized by variable SiO2 content (63.2 to 72.3 wt%) and high K2O (3.27–6.88 wt%). In addition, they show geochemical features akin to post-collisional related granites and possess positive zircon εHf(t) values of 0.9 to 4.95, suggesting that they mainly originated from the partial melting of high-K mafic rocks and formed under the post-collisional setting. The mafic dykes have a crystallization age of 2485 Ma. They show high Nb (8.64–9.39 ppm) and high Nb/U ratio (10.3–14.8), as well as radiogenic initial zircon Hf isotopes (﹢1.26–﹢4.39). These values indicate affinities with Nb-enriched basalts and that they originated from mantle-derived magma under a subduction-related back-arc extensional setting. Combined with previous research results, we believed that magmatic rocks of the LBD area may have formed under remote effects of oceanic slabs being subducted from the northwest to southeast of the eastern Hebei–western Liaoning Province back-arc basin system during the late Neoarchean to early Paleoproterozoic. Meanwhile, the K-rich granitoid rocks and coeval mafic dyke sequences imply the increased maturity of the continental crust and late Neoarchean to early Paleoproterozoic basement initiation of cratonization in the NCC.

High positive carbonate carbon isotope excursion identified in the North China Craton: Implications for the Lomagundi–Jatuli Event

AbstractRecords of the Lomagundi–Jatuli Event (LJE) are well preserved globally, but high δ13Ccarb carbonates have not been identified in the North China Craton (NCC). Our results on ~3–4 km thick carbonates from the newly confirmed Palaeoproterozoic successions in Fanhe Basin in the northeastern NCC show that the ~2.20–2.06 Ga carbonates have positive carbon isotope excursion and those deposited after 2.06 Ga have normal carbon isotope. Specially, carbonates from the Daposhan Formation have δ13Ccarb values of 10.2‰–11.8‰, which is the largest positive carbon isotope excursion in the NCC. The ~2.20–2.06 Ga carbonates in Fanhe Basin have similar δ13Ccarb values as those contemporaneously deposited in other cratons and their δ13Ccarb values exhibit a decreasing trend from ~2.20 Ga to 2.06 Ga. Our identification of carbonates with high positive δ13Ccarb values in Fanhe Basin not only casts new lights on records of the LJE in the NCC, but also provides important constraints on global significance of the positive δ13Ccarb excursion of LJE.

The isotope geochemistry of host rocks of the late Archean Guandi and Banshigou banded iron formations, southern Jilin Province: temporal and tectonic significance

The Guandi and Banshigou iron deposits of southern Jilin Province, China, are Algoma-type banded iron formations (BIFs) located in the Eastern Block of the North China Craton (NCC). LA–ICP–MS U–Pb dating shows the magmatic zircons in plagioclase amphibolite from the Guandi BIF (PA–GD) and plagioclase hornblende gneiss from the Banshigou BIF (PHG–BSG) were crystallised at 2556 ± 17 Ma and 2545 ± 27 Ma, respectively, representing the formation age of the BIFs. Metamorphic overgrowth zircons from both samples gave two U–Pb ages of 2452 ± 23 Ma and 2446 ± 70 Ma, indicating the age of metamorphism. The zircon εHf(t) values of PA–GD (–1.3 to +2.8) and PHG–BSG (–1.5 to +2.7) indicate that the magma source was derived from depleted mantle with contamination of crustal material. According to our study, the PA–GD and PHG–BSG were formed in an island arc setting and support previously proposed subduction zone tectonic models for the northeastern NCC during the Neoarchean.

Identification of metasomatic components in lithospheric mantle under multiple tectonic regimes: Insights from Early Cretaceous mafic rocks in the northeastern North China Craton

Identification of mantle metasomatic components under multiple tectonic regimes is crucial for reconstructing the subduction history of multiple plates. Representative Early Cretaceous (125–122 Ma) gabbroic diabase from the northeastern North China Craton (NCC), provides a geochemical record to explore the genetic relationship between mantle metasomatic agents and tectonic evolution. Samples from gabbroic diabase exhibit low SiO2 and high MgO contents as well as arc-like trace element patterns, suggesting a sub-continental lithospheric mantle (SCLM) origin. Their inherited zircons and isotope variations indicate the existence of two crustal components with different tectonic affinities that were recycled into the SCLM: Paleo-Asian oceanic crust and Yangtze Craton continental crust. The metasomatic signatures of the two crustal components are previously imprinted on the geochemical compositions of the studied mafic rocks. Subsequently, the melting of the metasomatic SCLM is triggered by the subduction of the Paleo-Pacific Plate. Based on the identification of mantle metasomatic components in this study and previous geological evidence, the spatial extents of the subduction influence of the Paleo-Asian oceanic plate and Yangtze Craton on the SCLM beneath the northeastern NCC are broader than previously considered. These new findings signify a critical role of the mantle metasomatic components that can effectively identify the geological relics of the previous plate subduction. Thus we believe that the former mantle metasomatism and latter mantle melting for mafic rocks suggest two geological implications.

Mafic–felsic igneous rocks in the north‐eastern North China Craton, eastern Jilin, NE China: Petrogenesis and implications for regional geodynamic evolution during the Cretaceous

We present zircon U–Pb ages, major and trace element analyses and zircon Hf isotope data on the Cretaceous mafic–felsic igneous rocks in the north‐eastern North China Craton (NCC) of NE China. These data have been used to discuss the petrogenesis of the mafic–felsic igneous rocks in order to constrain the geodynamical and magmatic evolution of the region. Zircon U–Pb dating results indicate that these igneous rocks crystallized during the Cretaceous (ca. 123–90 Ma). These mafic igneous rocks display low SiO2 contents, high MgO contents and marked enrichments in large‐ion lithophile elements (LILEs) and depletions in high‐field‐strength elements (HFSEs), combined with their εHf(t) values and La/Nb versus La/Ba diagram, suggesting they were derived from lithospheric mantle that experienced gradually increasing fluid metasomatism from 123 to 90 Ma. The felsic igneous rocks with high SiO2 values are metaluminous to weakly peraluminous and belong to the high–K calc–alkaline series. These felsic igneous rocks are all enriched in light rare earth elements (LREEs) and LILEs and relatively depleted in HFSEs, with barely negative Eu anomalies, combined with their εHf(t) values, these felsic igneous rocks were derived from partial melting of a lower crust. A synthesis of these new data with previous researches shows that the subduction and rollback of the Palaeo‐Pacific slab played a major role in the destruction of the north‐eastern NCC. The diagenetic temperatures of igneous rocks indicate that the mechanism of destruction of the NCC may be heterogeneous, most likely a thermal erosion mechanism in eastern Jilin area and a delamination mechanism in Liaodong Peninsula.

Early Precambrian mafic dykes in western Shandong province, North China Craton: constraints on the chronology, genetic model and tectonic significance

AbstractIn the Late Neoarchaean, the lithosphere of the North China Craton (NCC) experienced a strong extensional event, which is of great significance for understanding the evolution of the continental crust in the Precambrian. In this study, a suite of mafic dykes from Shandong province in the northeastern NCC were investigated to determine the nature, timing and source of rift-related magma activities using zircon U–Pb data, whole-rock geochemistry and Nd–Hf isotopes. Zircon U–Pb dating of four dolerites by laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) yielded weighted mean 207Pb/206Pb ages in the range 2509 ± 6.1 to 2537 ± 6.2 Ma (2σ, 95 % confidence interval). The mafic dykes are classified as alkaline rocks based on their K2O + Na2O contents (6.78–7.21 wt %) and belong to the shoshonitic series according to their K2O contents (3.23–3.36 wt %). The dolerites show low concentrations of light rare earth elements ((La/Yb)N between 7.17 and 8.55), positive Eu anomalies (Eu/Eu* between 1.12 and 1.27), positive Ba, K, Pb, Sr, Eu, Dy and Lu anomalies, and depleted U, Nb, Pr, Ta, P, Nd and Ti anomalies. The dykes are characterized by low initial (87Sr/86Sr)i (∼0.6969), positive εNd(t) values (0.2–0.8) and εHf(t) values (0.5–8.6) and relatively old mean Nd and Hf model age (2.73 Ga). Collectively, the data suggest that the mafic dykes were derived from the partial melting (10–20 %) of an isotope-depleted garnet–lherzolite mantle source that was hybridized through interaction with subducted lower crustal material. The parental magmas of these dykes underwent a certain number of crustal contaminations during magma ascent. The mafic magmatism represented in the form of the dyke swarms is considered to be a response to widespread lithospheric extension which affected the NCC at c. 2.5 Ga during the Neoarchaean.

The newly recognized ca. 1.23–1.21 Ga dolerite sills and flood basalts from Fanhe Basin in the northeastern North China Craton: Petrogenesis and tectonic implications

The Ectasion Period (1400–1200 Ma) represents a transition stage from Columbia (Nuna) to Rodinia supercontinents. LIPs and mafic magmatic events during this period can provide important constraints on deep processes and paleogeographic reconstructions during this transition. In this paper, we firstly reported some ca. 1.23–1.21 Ga flood basalts coeval with mafic sills from the Fanhe Basin in the northeastern North China Craton (NCC). New zircon/baddeleyite U-Pb/Pb-Pb dating on dolerite sills emplaced into the Fanhe Group yields emplacement ages from 1231 ± 9 Ma to 1206 ± 20 Ma. Whole-rock 40Ar/39Ar dating of two basalts from the Erdaogou Formation yields approximate total gas ages of ca. 1250 Ma and ca. 1210 Ma. These new geochronological results revealed that the Erdaogou basalts are coeval with some dolerite sills emplaced into the Kuangzhuangzi, Guanmenshan and Tongjiajie Formations and the dolerite sills emplaced into the Hutouling and Erdaogou Formations. These newly recognized ca. 1.23–1.21 Ga mafic rocks can be linked to the broader Licheng LIP of the previous studies. The ca. 1.23–1.21 Ga mafic rocks in the Fanhe basin can be divided into alkaline and sub-alkaline series and these two series exhibit distinct trace element and Nd isotopic compositions. The alkaline rocks show strongly fractionated chondrite-normalized REE patterns with high LaN/YbN values of 12.69–15.05. The sub-alkaline samples display less fractionated REE patterns with lower LaN/YbN values of 2.74–10.13. The alkaline rocks have OIB-like trace element patterns and slightly negative to positive εNd(t) values from −0.7 to 0.7. An OIB-like, asthenospheric mantle source is suggested as the source of the alkaline rocks. In contrast, the sub-alkaline rocks exhibit low negative εNd(t) values from −10.9 to −4.6 and are interpreted to be derived from a subduction-modified subcontinental lithospheric mantle. By comparisons with the coeval mafic magmatism in other parts of the NCC and other cratons, we suggest that the ca. 1.23–1.21 Ga mafic magmatism or LIP in the NCC was either related to the mantle plume that resulted in the Marnda Moorn LIP in Western Australia or related to a back-arc extension prior to the formation of a Grenvillian orogen located in another continent connected to the southeastern margin of the NCC during assembly of the Rodinia supercontinent.

Late Neoarchean TTG and monzogranite in the northeastern North China Craton: Implications for partial melting of a thickened lower crust

The petrogenesis and dynamic setting of Archean tonalite–trondhjemite–granodiorite (TTG) is widely debated. As a typical Archean terrane in the northeastern North China Craton (NCC), the southern Jilin Province area underwent multi-stage magmatism during the Neoarchean and is therefore a promising region in which to track the Neoarchean evolution of the NCC. This study investigates the petrogenesis of late Neoarchean TTGs and associated monzogranites and their tectonic implications. Zircon U–Pb dating results suggest that the TTGs and monzogranites have emplacement ages of 2.55–2.52 and 2.53–2.51 Ga, respectively. The TTGs have variable SiO2 (61.7–73.3 wt%) and MgO (0.66–2.74 wt%) contents and Mg# values of 33–50. Most have high Sr and low Y and Yb contents, with high Sr/Y and (La/Yb)N ratios. The TTGs have variable εHf(t) (+0.7 to + 8) and εNd(t) (−2.77 to + 2.79) values. These characteristics, together with the results of thermodynamic partial-melting modelling, indicate that the TTGs can be classified as medium- and low- pressure types and were likely generated by amphibole-breakdown partial melting of 2.9–2.7 Ga juvenile basaltic rocks under P–T conditions of 1.0 ± 0.1 GPa and 880 ± 50 °C. The monzogranites have higher SiO2 (66.1–76.0 wt%) and K2O (4.03–5.06 wt%) and lower TFe2O3 (0.89–4.97 wt%) and MgO (0.21–1.27 wt%) contents. They also have high Sr/Y and (La/Yb)N ratios and variable εHf(t) (+0.6 to + 5.4) and εNd(t) (−3.47 to − 0.15) values. The geochemical and Hf–Nd isotopic compositions of the monzogranites indicate that the parental magmas may have been derived through the partial melting of thickened lower crust with heterogeneous sources. The high thermal gradient (>730 °C/GPa−1), anticlockwise metamorphic P–T paths, and 3.4–3.2 Ga remanent zircons in the region suggest that a late Neoarchean thickened lower crust was the likely geodynamic setting for the generation of the TTGs and monzogranites.

Petrogenesis of newly identified Neoarchean granitoids in the Qingyuan of NE China: Implications on crustal growth and reworking of the North China Craton

• A new ca. 2.7–2.5 Ga granitoid suite was identified in the Qingyuan, NE China. • The 2.68 Ga TTG was derived from ancient lower crust as well as juvenile crust. • Qingyuan granitoids record two periods of crustal growth and reworking events. Discovery of ca. 2.7 Ga tonalite-trondhjemite-granodiorite (TTG) in the North China Craton (NCC) can provide the key clue to understanding the Neoarchean crustal evolution. Most recently, we mapped out ca. 2.7 Ga TTGs from the northern Qingyuan at the northeastern margin of NCC. Together with the associated ca. 2.6–2.5 Ga high-K granites and high-Mg diorites, this study provides new constraints on crustal growth and reworking during the Neoarchean. Zircon U–Pb dating indicates that the TTGs, high-K granites and high-Mg diorites were formed at ca. 2.68 Ga, ca. 2.56 Ga and ca. 2.54 Ga, respectively. All of these lithologies exhibit enrichments in large ion lithophile elements (e.g., Rb and Ba) but depletions in high field strength elements (e.g., Nb and Ta), with positive εHf(t) and εNd(t) values. The TTGs have moderate SiO 2 , low Al 2 O 3 and variable MgO contents with high Sr/Y and (La/Yb) N ratios. They were likely derived from partial melting of mafic lower crust. High SiO 2 and K 2 O but low MgO and Cr contents as well as high Sr/Y and (La/Yb) N ratios reflect an origin of recycling of ancient crustal rocks (e.g., pre-existing TTGs) for the high-K granites. The high-Mg diorites have high MgO and Cr contents but low Sr/Y and (La/Yb) N ratios, which indicate that they could be sourced from partial melting of metasomatized mantle peridotite. Combined with previous studies, the northeastern NCC experienced two major periods of ca. 2.7 Ga and ca. 2.6–2.5 Ga crustal growth and reworking events.

Petrogenesis delineation of the felsic intrusive rocks in the eastern North China Craton: Implications for crustal evolution and geodynamic regimes

As the dominant component of the continental crust, Archean intrusive granitoids can provide significant insights into the growth and evolution of the early crust. In this study, we report a systematic geochronological and geochemical study on a tonalite-trondhjemite-granodiorite (TTG 1 )-granites (G 2 )-quartz monzonite (QM) assemblage in the northeastern North China Craton (NCC). Zircon U-Pb dating shows that they were emplaced during 2506–2549 Ma. Their geochemical features, such as REE concentrations, patterns and ratios, superchondritic Nb/Ta ratios, and similarity to the HP–MP TTGs, suggest residues of garnet-amphibolite- to eclogite-facies. TTGs in Group I show high Sr and low Y concentrations and negligible/pronounced negative Eu anomalies, reflecting rare or a small quantity of plagioclase residue. Positive Eu anomalies of Group II possibly indicate involvement of varying amount of accumulative plagioclase, and that garnet fractionation also plays a role. High MgO, Mg # , Cr and Ni, and positive ɛ Hf ( t ) varying from juvenile to evolved signatures, suggest that the TTGs were generated under a continental arc setting. The granitic rocks (G 2 -QM) were generated by melting of predominant TTGs and subordinate metasedimentary rocks, with late-early Neoarchean TTGs, Mesoarchean TTGs, and Eoarchean crustal material in the NCC involved. Isotopic evidence shows that 2.7–2.9 Ga crustal reworking predominates the formation process of the granitoids. The study area witnessed a long period of crust extraction from Eoarchean to the end of Neoarchean. Subduction-related magmatisms at late Neoarchean are widespread in the world. • The TTGs in the SJP were formed under a continental arc setting. • Meso- and Eo-archean crust materials contribute to the generation of granitic rocks. • Neoarchean subduction was widespread around the globe.

Sulfide micro-textures and in-situ compositions from the Wulong gold deposit, northeastern North China Craton: Implication for ore-forming processes

Lode gold deposits in the North China Craton (NCC) form the only known giant late Mesozoic gold province in the world’s Precambrian cratons. Understanding the ore genesis for these deposits is of great scientific and economic importance. In order to provide constraints on the ore-forming processes, this study presents a combination of micro-textures and in-situ compositions of sulfide from the Wulong gold deposit (80 t @ 5.35 g/t Au; 127–122 Ma), northeastern NCC. Five sub-generations of pyrite (Py1–Py5) are identified based on micro-textural observations and EPMA results. In-situ trace elemental concentrations show that pyrite from the stage 1 (Py1) has high Co and Ni contents but no Au (<0.02 ppm). In contrast, euhedral Py2 and porous Py3 from stage 2 exhibit much higher Au (average 3.08 ppm and 1.66 ppm), As (average 1400 ppm and 946 ppm), and Ag (average 2.81 ppm and 3.21 ppm). Anhedral Py4 from stage 3 shows lower Au (average 0.31 ppm) and As (average 337 ppm) concentrations when compared to Py3. However, Py5 from stage 3 exhibits significant increases of As (average 7102 ppm) and Au (average 5.46 ppm) again and is featured by the alternation of Co-Ni- and Au-As-rich zones. Other sulfides, including pyrrhotite, chalcopyrite, and sphalerite, are poor in Au and As. Apart from visible gold grains related to Bi-rich melts, LA-ICP-MS spot and mapping analyses reveal that invisible gold hosted in Py2 to Py5 occurs dominantly as lattice-bound solid solutions (Au+). Direct gold precipitation from anomalously As-rich auriferous fluids induced by fluid immiscibility is proposed as the dominant mechanism of invisible gold enrichment. In-situ δ34S values of Py1 to Py4 exhibit narrow ranges of 1.0 to 3.8 ‰, indicating a deep-seated magmatic sulfur source. The elevated δ34S values (2.3–6.3 ‰) of Py5 are ascribed to some wall-rock contributions during fluid-rock interaction. These findings shed new light on the link between multistage fluid immiscibility and the chemical and micro-textural fingerprints of pyrites and the role of fluid immiscibility in the deposition of invisible gold.

Modification of the lithospheric mantle induced by recycled crustal components: Insights from Early Cretaceous appinites from the Liaodong Peninsula, NE China

AbstractThe term “appinites” refers to amphibolerich mafic rocks, as one of the most typical products of partial melting of a metasomatic lithospheric mantle. This paper presents results of integrated geochemical and isotopic analyses for six Early Cretaceous (125–119 Ma) appinitic plutons from the Liaodong Peninsula, northeastern North China Craton (NCC), to not only investigate the properties of the metasomatic lithospheric mantle induced by variable recycled crustal components but also to discuss a hydrous mantle source. The appinites originated from partial melting of sub-continental lithospheric mantle (SCLM), and can be geochemically categorized into three groups distinguished by the input of different recycled crustal components (e.g., terrigenous sediments and delaminated lower continental crust) on the basis of two distinct Hf-O isotopic arrays. Based on the occurrence of voluminous amphiboles (50–60 vol%) and minor clinopyroxene remnants, a petrogenetic model was proposed to interpret the formation of appinites. Asthenospheric upwelling caused by the subduction and roll-back of the Paleo-Pacific plate firstly resulted in partial melting of the SCLM to yield basaltic magmas. Subsequently, numerous hydration reactions between early anhydrous minerals (e.g., olivine and pyroxene) of basaltic magmas and hydrous melts derived from terrigenous sediments and delaminated lower continental crust occurred to produce the studied appinites. Ultimately, the recycled crustal materials can serve as the metasomatic agent not only to transfer the enriched isotopic signatures into the studied appinites but also to represent hydrous components to play the part of hydrous reactions. The high abundance of amphibole in the studied appinites is indicative of a hydrous lithospheric mantle beneath the eastern NCC.

Magma assembly and evolution of the Early Cretaceous Sanguliu pluton in the Liaodong Peninsula, NE China

• Influx of two magmas from the ancient crust constructed the zoned Sanguliu pluton . • Mafic magma provided primarily heat but little material for the Sanguliu granites . • Magma mingling occurred during the magma ascent and emplacement processes. Zoned granitic plutons and mafic microgranular enclaves (MMEs) contain important information on magma assembly, mixing, and evolution. The Sanguliu pluton in the northeastern North China Craton (NCC) consists of fine-/medium-grained monzogranite in the outer zone and coarse-grained syenogranite-monzogranite in the inner zone, with MMEs being found in both zones. These rocks have similar zircon U-Pb ages of ∼ 130 Ma. The granites in both the outer and inner zones display variably enriched isotopic compositions of ( 87 Sr/ 86 Sr) i (0.7147–0.7163), εNd(t) (−18.6 to −20.8), and zircon εHf(t) (−18.0 to −24.3), indicating that they were mainly sourced from the ancient lower crust with minor depleted mantle contributions. Zircons in the outer-zone MMEs are subhedral-anhedral with patchy zoning in the CL images and have a narrow εHf(t) range (−16.2 to −20.9) similar to zircons from the host granites. In contrast, zircons in the inner-zone MMEs are mainly euhedral with core-rim structure, and have a wider εHf(t) range (−0.3 to −20.8). The complex morphology and internal structure of these zircons are ascribed to the metasomatism and growth during magma mingling processes. The varying zircon εHf(t) values indicate that these MMEs were derived from the depleted mantle and had been isotopically modified by the host granitic magma.

Neoarchean granitoids and tectonic regime of lateral growth in northeastern North China Craton

The Archean Eastern Liaoning metamorphic basement block is located in the northeastern North China Craton (NCC), in which ∼2.9 to 3.8 Ga lithological assemblages are well developed. The region which exposed these ancient lithological assemblages is usually called as an ancient continental nucleus. Toward north from the northeastern margin of the ancient continental nucleus, ∼2.5 to 2.7 Ga lithological assemblages continuously developed, forming abundant ∼2.5 Ga tonalite- trondhjemite- granodiorite (TTG) and high-K granitoids. Some ∼2.7 Ga TTG gneisses and metamorphic calk-alkaline volcanic rocks have also been documented recently in the Eastern Liaoning to the Southern Jilin of northeastern NCC. Our geological investigations found that many big ∼2.7 Ga TTG gneiss enclaves are preserved in the ∼2.5 Ga granitoids in the northeastern NCC. The early Neoarchean (∼2.7 Ga) TTG gneisses are exposed in the Waitoushan-Baishan areas, together with many contemporaneous subduction-related metamorphic calk-alkaline volcanic rocks in the Helong area of Southern Jilin province, constituting a nearly E-W-trending ∼2.7 Ga island arc belt in the northeastern NCC. However, the ∼2.7 Ga geological record is absent within the Anshan-Benxi-Waitoushan ancient microblock (ABWN) domain, suggesting that the ∼2.7 Ga arc belt was formed far away from the ABWN domain. The petrogenesis of ∼2.52–2.59 Ga TTG and sanukitoid gneisses, integrating with contemporaneous top-to-the-NE thrusting structural features, indicate that the new oceanic crust in the Waitoushan-Weiziyu-Jiubing (WWJ) area subducted to the southwest from ∼2.53–2.60 Ga. At the Archean end, the northern Liaoning-eastern Hebei intraoceanic arc system subducted to the southeast, which led to the final amalgamation among the ABWN, WWJ and northern Liaoning areas. Subsequently (∼2.50–2.53 Ga), the subducted slab broke off and the collisions between the arc and ancient continental nucleus, as well as the arc and arc, resulted in the generation of extensive crust-derived high-K granitoids.

Petrogenesis of the Chaihulanzi Gneiss and its Tectonic Implications for the North China Craton

AbstractThe Chaihulanzi area in eastern Inner Mongolia is tectonically situated on the northern margin of the North China Craton (NCC). The main Precambrian lithologies of the area have been referred to the Archean Jianping Group meta‐supracrustal sequences. Based on field observations, petrographic, whole‐rock geochemical, and zircon U‐Pb geochronological results, a magmatic origin for the units is proposed. Our results show that the Chaihulanzi gneisses are mainly of granitic, dioritic and granodioritic compositions, and show typical magmatic rock textures and mineral assemblages. The dioritic and granodioritic gneisses show Na‐rich tonalite–trondhjemite–granodiorite (TTG)‐like affinity with zircon U‐Pb dates of ca. 2.57–2.59 Ga, representing a juvenile continental growth for the northeastern NCC. The granitic gneiss is indeed potassic granite and yielded a zircon U‐Pb date of ∼2.50 Ga, which is contemporaneous with the Jining–Jiaoliao microblock collision (2.53–2.49 Ga), implying another crustal growth event. The well‐developed gneissosity in 2.57–2.59 Ga dioritic and granodioritic gneisses together with the 2.5 Ga potassic granite, which crosscuts the gneissosity implies a 2.57–2.50 Ga (mainly 2.53–2.51 Ga) collisional orogeny, probably related to the Jining–Jiaoliao microblock collision. Our new geology and chronological results provide new evidence for the early Precambrian tectonic evolution of the NCC.

Ages of the Proterozoic strata in Fanhe Basin revisited: Implications for geological records of the Great Oxidation Event in the North China Craton

The Great Oxidation Event (GOE) and Lomagundi-Jatuli Event (LJE) during Paleoprterozoic Era represent significant global environmental changes in Earth’s history and their geological records have been identified from many ancient cratons. However, reliable records of GOE and LJE are rare in the North China Craton (NCC) due to high-grade metamorphism on Paleoproterozoic strata during Orosirian Period and poor age constraints. Weakly metamorphosed to unmetamorphosed Proterozoic strata termed as Fanhe Group of around 8 km thick are well preserved in Fanhe Basin in the Archean Longgang Block in northeastern NCC and the Guanmenshan Formation from the lower part of the Fanhe Group is characterized by positive δ13Ccarb excursion of around +5‰. Since the Fanhe Group was usually considered as Meso-Neoproterozoic in ages, the reasons for positive δ13Ccarb excursions in the lower Fanhe Group are unclear. Our new LA-(MC-)ICP-MS U-Pb dating on a dolerite sill intruding into the Guanmenshan Formation yields two upper intercept 207Pb/206Pb ages of 2065 ± 20 Ma (95% confidence, MSWD = 1.4, N = 26) and 2062 ± 22 Ma (95% confidence, MSWD = 1.05, N = 22), respectively. Combined with the weighted mean 207Pb/206Pb age of the youngest detrital zircon population of the Daposhan Formation (2199 ± 19 Ma, 95% confidence, N = 8, MSWD = 0.47) and their contact relations, the deposition ages of the Daposhan, Kangzhaungzi, Guanmenshan and Tongjiajie formations from the lower part of Fanhe Group were constrained to be Rhyacian Period from ca. 2200 Ma to ca. 2060 Ma, not Mesoproterozoic Era as previously regarded. These new age constraints provide solid evidence for the existence of weakly metamorphosed stratigraphic records of GOE and LJE in lower part of Fanhe Group in the NCC. Stratigraphic correlations with other ancient cratons show that the Guanmenshan Formation in Fanhe Basin in the northeastern NCC can be correlated with the Dashiling Formation of the Hutuo Group in the central NCC, the Lucknow Formation in West Australia, the Upper Pretoria Formation in South Africa, the Gordon Lake Formation in North America and the Tulomozero and Kuetsjärvi formations in Fennoscandia, and therefore the Fanhe Group provides excellent stratigraphic records to study GOE and LJE in the NCC.

Lithospheric structure beneath the boundary region of North China Craton and Xing Meng Orogenic Belt from S-receiver function analysis

The boundary region of the North China Craton (NCC) and Xing-Meng Orogenic Belt (XMOB), including the northern boundary of the NCC and the southern XMOB, is the ideal area to investigate the spatially uneven lithospheric deformation and associated tectonic evolution in the boundary region of the craton and orogen. The depths and structures of the lithosphere–asthenosphere boundary (LAB) and mid-lithosphere discontinuity (MLD) are the key information to describe the nature and deformation pattern of the lithosphere, and thus can provide basic constraints on the associated tectonic processes and mechanism of the lithospheric deformation. Based on waveform data collected from 226 broadband seismic stations, high resolution spatial variations in the LAB and MLD depths were obtained by using the wave equation migration method for the S-receiver functions. The migrated images show a lateral variation in the LAB depth from 100–120 km in the northern boundary of the NCC to 120–140 km in the southern XMOB. The imaged LAB within the NCC is much shallower than that revealed by mantle xenoliths enclosed in the nearby Early Paleozoic kimberlites (~180 km), suggesting that the cratonic lithosphere of the area may have undergone significant thinning during the Phanerozoic evolution. Furthermore, a coherent MLD is identified at depths of 70–90 km beneath the northeastern NCC, which corroborates the speculation that the MLD probably existed in the eastern NCC before lithospheric destruction in the Mesozoic. The spatial variations in the LAB and MLD depths probably reflect complex lithospheric deformation and thinning around the boundary region of NCC and XMOB. The properties, including the gradient thickness and S-wave velocity contrast, of the two discontinuities further indicate that lithospheric deformation and thinning might be related to partial melting induced by the Big Mantle Wedge associated with the subducting Paleo-Pacific plate and its stagnation during the Late Mesozoic.

Geochemistry of apatites from Mesozoic granitoids in the northeastern North China Craton and their petrogenetic implications

We report geochemical data of apatites from Mesozoic granitoids in the northeastern North China Craton (NCC), and discuss the relationship between apatite and whole-rock compositions with the aim of using apatite geochemical data to constrain granitoid petrogenesis. Measured Sr contents and Sr/Y ratios of apatites exhibit positive correlations with those of their host rocks, and εNd(t) values of apatites display a strong linear relationship with εHf(t) values of zircons in the granitoids. In addition, apatites exhibit similar rare-earth element (REE) distribution patterns with their host rocks, although apatites have much higher REE contents. Sr/Y–Y variation diagram for apatite is proposed to distinguish adakitic rock from non-adakitic. The REE patterns of apatites, together with other geochemical indexes, can also be used to discriminate highly fractionated granitoids from unfractionated I-type granite or other type granite. The geochemical and Nd isotopic compositions of apatites have well revealed the magma source of Mesozoic granitoids in the northeastern NCC. In conclusion, we highlight that apatite geochemistry reflects the whole-rock geochemical characteristics of granitoids and has the potential to track granite detritus.

Petrogenesis of Early Cretaceous volcanic rocks of the northeastern North China Craton: Constraints from elemental and Sr–Nd–Pb isotope geochemistry

This study examines the geochemical and whole-rock Sr–Nd–Pb isotopic compositions of Early Cretaceous volcanic rocks of the southern Jilin Province (Tonghua and Huanren areas) and Liaodong Peninsula (Xiuyan, Dandong, and Guiyunhua areas), northeastern North China Craton (NCC). Two groups of volcanic rocks are recognized in the northeastern NCC. The geochemistry and isotopic compositions of the intermediate-acid volcanic rocks indicate that a systematic decrease in whole-rock εNd(t) is accompanied by an increase of Zr/Nb. Modeling results suggest that those intermediate-acid volcanic rocks experienced the assimilation-fractional crystallization (AFC) process with different lower continental crust (LCC) components, indicating the heterogeneity of LCC in the northeastern NCC. As for basic volcanic rocks, they are characterized by “weakly enriched” isotopic signatures, i.e., moderately radiogenic Sr (0.7062–0.7082), unradiogenic Nd (−5.29 to −1.14), and highly radiogenic Pb compositions. The narrow scope of Sr–Nd–Pb isotopic compositions of whole-rock indicates insignificant crustal assimilation. Instead, the high Th/Yb ratios were largely inherited from source enrichment through the input of subducted sediment. Furthermore, element-isotopic modeling suggests that the “weakly enriched” mantle-derived rocks have resulted from a depleted mantle source metasomatized via the sediment-derived melt. Our results provide powerful petrological and geochemical evidence on the Early Cretaceous subduction of the Paleo-Pacific plate beneath the northeastern NCC and suggest the metasomatic process by subducted sediment-derived melt may play an important role in depleted mantle enrichment.