The Khondalite Belt (KB) is a Paleoproterozoic collisional orogen within the North China Craton (NCC), but its pre-collisional tectonic evolution remains poorly constrained. In this study, we conducted integrated geochronological, in-situ Hf isotopic, and whole-rock geochemical analyses of the mafic–intermediate intrusions exposed in the Daqingshan area of the central KB to determine their formation ages, petrogenesis, and tectonic setting, thereby further constraining the late Paleoproterozoic tectonic evolution of the KB. Zircon U-Pb dating results show that these rocks crystallized at ∼1.97–1.96 Ga and subsequently underwent metamorphism at ∼1.94–1.92 Ga. These rocks are enriched in light rare earth elements and depleted in high field strength elements, exhibiting geochemical affinities comparable to those of continental margin arc basalts and island arc basalts. In-situ zircon Hf isotopic analyses yield positive εHf(t) values. The available data suggest that the mafic–intermediate intrusions were derived from a hybrid mantle source dominated by asthenospheric mantle and metasomatized by fluids derived from a subducted slab and experienced fractional crystallization of olivine, clinopyroxene, Fe-Ti oxides and apatite. Overall, these findings suggest that the KB was in a subduction-related tectonic setting at ∼1.97–1.96 Ga. Subsequent continent–continent collision at ∼1.95 Ga resulted in metamorphism of both the magmatic rocks and the Khondalite Series at ∼1.94–1.92 Ga.

The western Yunnan is tectonically located in the southeastern margin of the Tethys tectonic domain, with intensive Cenozoic magmatism. The understanding of the genesis and dynamic background of the Cenozoic granites in this area remains controversial. We conducted zircon U-Pb geochronology, whole-rock major and trace elements, and zircon Hf isotope analyses upon the Cenozoic Changning and Yunxian monzogranites in the northern part of the Lincang granite batholith. The results show that the Changning monzogranites crystallized at similar to 46Ma. Geochemically, they belong to calc-alkaline series, and characterized by high potassium and low calcium contents with A/CNK ratios ranging from 1.07 to 1.08, and enriched in light rare earth elements and large ion lithophile elements relative to high field strength elements. The epsilon(Hf)(t) values range from -4.93 to -2.20, with the two-stage model ages from 1.43Ga to 1.26Ga, belonging to adakitic affinity. The source rocks of the monzogranites are originated from partial melting of the thickened ancient lower crust. By contrast, the Yunxian monzogranites is formed at similar to 27Ma. They belong to strongly peraluminous sereies and featured by high-K calc-alkaline with low magnesium contents, and enriched in light rare earth elements and large ion lithophile elements and depleted in high field strength elements. The epsilon(Hf)(t) values and two-stage model ages (t(DM2)) of analysized samples range from -5.97 to -2.34 and 1.99Ga to 1.26Ga respectively. The sources rocks of this pluton are of highly differentiated S-type granite characteristics, and are generated by dehydration melting of metapelitic rocks. Combined with regional geological data, we propose a two-stage model to explain the formation of these monzogranites: (1) due to the rollback of the subducted Neo-Tethys slab, the lithospheric mantle underwent convective thinning, inducing asthenosphere upwelling and partial melting of the thickened ancient lower crust and formed the Changning monzogranites; (2) subsequently, the shear heating which derived from the large-scale strike-slip shearing activities in the Cenozoic induced dehydration melting of the continental crust and generated the Yunxian monzogranites.

Archean tonalite-trondhjemite-granodiorite (TTG) suite and K-rich granitoids provide direct evidence of the generation and differentiation of the Archean continental crust. Within the North China Craton (NCC), the Anshan area serves as an exceptional natural laboratory, preserving a geological record spanning from 3.8 to 2.5 Ga. Here, we conducted comprehensive geochemical, geochronological, and zircon Hf-O isotopic analyses for the Paleoarchean-Mesoarchean granitoids from the Anshan region. Zircon U-Pb dating suggest that these granitoids formed during 3.3-3.1 Ga. The ca. 3.3 Ga monzogranitic gneisses exhibit high SiO2 and K2O, low Mg# values, negative Eu anomalies, unradiogenic Hf isotopes (i.e., epsilon Hf(t) values = -5.16-+0.08, TDM and "mantle-like" 518O values (up to + 5.64 %o). Geochemical features divide them into two distinct groups, both are recycling products of pre-existing Eoarchean TTGs. Group 1 and Group 2 originated from 10 %-20 % and 20 %-30 % partial melting of pre-existing Eoarchean TTGs at depths of 1.25-1.75 GPa and 0.5-0.75 GPa, respectively. The ca. 3.3 Ga trondhjemite gneisses show high SiO2, low Mg# values, low Sr/Y and (La/Yb)N ratios. Their epsilon Hf(t) values range from + 0.91 to + 1.10, with TDM 2 ages of 3682-3665 Ma. In contrast, the ca. 3.3 Ga monzonitic gneisses have lower SiO2 contents, higher Al2O3, total alkali (Na2O + K2O), and Sr/Y and (La/Yb)N ratios. Their epsilon Hf(t) values range from -2.69 to + 0.50, with TDM 2 ages of 4040-3750 Ma. The ca. 3.1 Ga trondhjemite gneisses display higher Sr/Y and (La/Yb)N ratios, enriched LREEs and depleted HREEs. Magmatic zircons yield 518O values of 3.87-6.52 %o and epsilon Hf(t) values of -2.39 to + 0.95, with TDM 2 ages of 3881-3550 Ma. The geochemical and Hf-O isotope characteristics suggest that both the 3.3-3.1 Ga trondhjemite gneisses and the ca. 3.3 Ga monzonitic gneisses originated from partial melting of mafic rocks at variable depths. During 3.3-3.1 Ga, the NCC experienced intensive crustal growth and rework/recycling. Two magmatic events (ca. 3.3 Ga and ca. 3.1 Ga) and subsequent tectono-thermal events were induced by multi-stage magmatic underplating of mantle upwelling within a plume-related tectonic setting.

The Songliao-Xilinhot block (SXB) in the eastern part of the Central Asian Orogenic Belt (CAOB) is a Precambrian continental block that provides clues to the evolution of the CAOB. However, its structural relationship with adjoining terranes and cratons, and its role in past supercontinent cycles remain unclear. Here, we describe the whole-rock geochemistry, zircon U-Pb ages, and Sr-Nd-Hf isotopic data of Neoarchean granitoid rocks in the Longjiang area of the SXB, NE China. Zircon U-Pb dating indicates that tonalite-trondhjemite-granodiorites (TTGs) and monzogranites were formed at 2.56-2.55 and 2.55-2.51 Ga, respectively. The TTGs have low MgO, Y, and Yb, and high Sr contents. Their Sr/Y and (La/Yb)N ratios and YbN values vary widely, with epsilon Hf( t ) values of -2.8 to + 3.1 and a epsilon Nd( t ) value of + 2.4. Thus, the TTGs are medium- and low-pressure types, possibly formed by partial melting of middle Archean basic lower crust. The monzonitic granites have high K2O contents, high K2O/Na2O, Sr/Y, and (La/Yb)N ratios, low MgO contents and Mg# values, and variable epsilon Hf ( t ) and epsilon Nd ( t ) values (-3.1 to + 6.3 and -0.9 to + 2.8). The geochemical characteristics and Hf-Nd isotopic compositions of then monzogranites indicate that their parental magmas were formed by partial melting of thickened lower crust derived from heterogeneous sources. Thickening of the lower crust during the late Neoarchean may have promoted the formation of the TTGs and monzogranites. U-Pb and Lu-Hf isotopic data for magmatic zircons from Precambrian intrusive rocks, and detrital zircons from Meso-Neoproterozoic metasedimentary rocks in the SXB were studied to elucidate the origin of the Precambrian SXB. Results indicate a close affinity of the SXB with Laurentia in the Precambrican, while geological evidence and the presence of 1.4 Ga A-type granite in the SXB preclude most cratons as being the source of the Precambrian SXB. Precambrian magmatic events, sedimentary sequences, and significant changes in zircon Hf isotopic compositions within the Precambrian SXB indicate that the block responded to the assembly of the Nuna supercontinents. It underwent a change in tectonic environment from long-term subduction and extension to short-term collision during the breakup of Nuna and subsequent amalgamation with Rodinia.

The evolution and differentiation of early continental crust remain a fundamental research frontier, with potassic granitoids providing critical insights into these processes. This study investigates the petrogenesis and tectonic setting of Late Mesoarchean (3.0-2.9 Ga) potassic granitoids in the Anshan area of the North China Craton (NCC) through comprehensive geochronological, geochemical, and zircon Hf-O isotopic analyses. Zircon U-Pb dating reveals the studied Late Mesoarchean potassic granitoids include ca. 2.95 Ga Tiejiashan biotite monzograniticquartz monzonitic gneisses and ca. 3.0 Ga Donganshan monzogranitic gneisses. The Tiejiashan potassic granitoids exhibit high SiO2 (68.47-75.28 wt%), K2O (4.32-4.93 wt%) contents, K2O/ Na2O (1.19-1.53) ratios, low Mg# (23-25) values and strongly negative Eu anomalies (delta Eu = 0.19-0.31), with metaluminous and ferroan affinities, classifying them as A-type granites. Magmatic zircons yield delta 18O values of+4.66 %o-+6.10 %o and epsilon Hf(t) values of-10.61 to-6.34, with TDM 2 ages of 4.43-3.99 Ga. The geochemical and Hf-O isotope characteristics suggest that Tiejiashan potassic granitoids originated from partial melting of Eo-Paleoarchean TTGs (3.8-3.3 Ga) under shallow crustal conditions. In contrast, the Donganshan monzogranitic gneisses display higher SiO2 (75.69-76.14 wt%) and peraluminous signatures, with pronounced LREE-HREE fractionation, moderately negative Eu anomalies (delta Eu = 0.69-0.80) and unradiogenic Hf isotopes (i.e., epsilon Hf(t) values =- 0.85-+1.87, TDM 2 age = 3.63-3.39 Ga), indicating Donganshan monzogranitic gneisses originated from partial melting of short-residence TTGs with garnet and amphibole residues. The emplacement of these potassic granitoids records a crustal recycling process, while primary magmatic fabrics (i.e. L >> S, L = S) in the ca. 2.95 Ga Tiejiashan pluton suggest high-temperature plastic flow linked to magma underplating. These findings highlight a Late Mesoarchean crustal reworking/recycling process of NCC, driven by the remelting of ancient crust due to magma underplating associated with mantle upwelling in an extensional setting.

Flood disasters can have a serious impact on people's production and lives,and can cause huge losses in lives and property security.Based on multi-source remote sensing data,this study established decision tree classification rules through multi-source and multi-temporal feature fusion,classified ground objects before the disaster and extracted flood information in the disaster area based on optical images during the disaster,so as to achieve rapid acquisition of the disaster situation of each disaster bearing object.In the case of Qianliang Lake,which suffered from flooding in 2020,the results show that decision tree classification algorithms based on multi-temporal features can effectively integrate multi-temporal and multi-spectral information to overcome the shortcomings of single-temporal image classification and achieve ground-truth object classification.

Identifying the processes responsible for the generation and evolution of the Archean continental crust is crucial for understanding the tectonic regimes present on early Earth. A major episode of continental growth during the early Neoarchean has been identified in many cratons worldwide. Indeed, early Neoarchean magmatism has been recognized in several terranes within the North China Craton over the past decade, although the geodynamic regime in which such activity occurred remains highly debated. Here, we focus on newly recognized early Neoarchean mylonitic trondhjemite and granodiorite from the southern Jilin terrane, China, to address this knowledge gap. Zircon U-Pb geochronology reveals that these granitoids formed at ca. 2.7 Ga. They display adakitic geochemical characteristics, such as high Sr/Y and LaN/YbN ratios. Their low MgO, Cr, and Ni contents, along with low delta 18 O values (4.19%0-5.39%0) and positive pound Hf( t ) (0.7-6.5) and pound Nd( t ) (2.0-2.6) values, indicate that they originated from thickened juvenile lower continental crust. Thermodynamic modeling further constrains the ca. 2.7 Ga granitoids to have been generated from partial melting driven by amphibole breakdown under granulite-facies P-T conditions of 10-15 kbar and 800-900 degrees C, with garnet and amphibole as the major residual minerals. Combined with previous studies, we suggest that the North China Craton underwent significant crustal growth during the early Neoarchean, which was likely attributed to the synergistic effects of waning mantle plume activity and the coeval onset of plate tectonics.

Metapelitic gneiss (sillimanite-biotite-garnet gneiss) and S-type granites have been identified in the Khondalite Belt (KB), located in the northeastern margin of the North China Craton (NCC), which has traditionally been considered closely related to the Sao Francisco-Congo Craton (SFCC). Zircon U-Pb-Hf isotopic experiments on these rocks revealed two distinct late Paleoproterozoic age groups: 2.00-1.95 and 1.93-1.90 Ga. The 2.00-1.95 Ga magmatic zircon cores displayed epsilon Hf(t) values ranging from -1.94 to +7.48, with two-stage Hf model ages between 2.28 and 2.71 Ga. The 1.93-1.90 Ga ages obtained from the S-type granites were interpreted as late Paleoproterozoic anatectic magmatism, which coincides with the metamorphism and anatexis ages derived from the metapelitic gneisses. The 1.93-1.90 Ga anatectic zircon rims exhibited significantly lower 176Lu/177Hf and 176Hf/177Hf values compared to the inherited magmatic zircon cores, indicating that the Lu-Hf isotope compositions were reset during anatexis. A comparative study suggests that the similarities between the khondalite rocks (or granitic rocks in KB) of the NCC and SFCC, such as related mineral paragenesis and reactions, provenance, tectonic setting, depositional age, nearby P-T conditions, and metamorphism age, indicate a potential genetic correlation of these rocks. Therefore, the late Paleoproterozoic metamorphic and anatectic events align with global orogenic events recorded in several continental fragments, suggesting a connection to the Columbia supercontinent.

Zircon U-Pb geochronology, geochemistry and Hf isotope analysis of supracrustal rocks in the Anshan-Benxi area in the northeastern part of the North China Craton can help constrain their petrogenesis and tectonic background, providing evidence for a further investigation of the late Neoarchaean tectonic environment in the Anshan-Benxi area. The primary rock types observed among the supracrustal rocks in the Anshan-Benxi area comprise amphibolite, metamorphic rhyolite, metamorphic sandstone, chlorite schist, actinolite schist, among others. SHRIMP zircon U-Pb dating indicates that magmatic zircons from the amphibolite (GCN-1) formed at 2553 +/- 18Ma. Similarly, LA-ICP-MS zircon U-Pb dating reveals that magmatic zircons from the metamorphic rhyolite (G2304-1) were formed at 2457 +/- 35Ma. The peak age of the metamorphic sandstone is determined to be approximately 2500Ma, suggesting that the supracrustal rocks in the Anshan-Benxi area originated in the late Neoarchaean. The protoliths of sericite quartz schist and metamorphic rhyolite are identified as rhyolitic volcanic rocks, displaying a right-leaning distribution pattern of rare earth elements (REEs). On the other hand, actinolite schist, chlorite schist and amphibolite are classified as basaltic volcanic rocks, exhibiting a flat REE pattern with a weak negative Eu anomaly. The epsilon Hf(t) value of metamorphic rhyolite ranges between -1.19 and -1.47, with a two- stage depleted mantle model age of tDM2(Ma) = 2922-3132 Ma. The protolith magma of sericite quartz schist and metamorphic rhyolite originates from partial melting of 3.0Ga basaltic crust, while the source of actinolite schist, chlorite schist and amphibolite are mainly derived from the mantle. In summary, the findings suggest that plate already existed in the late Neoarchaean or earlier, with magmatism in the Anshan-Benxi area likely occurring within an arc tectonic environment linked to plate subduction.

The North China Craton (NCC) preserves a wide range of Neoarchean magmatic rocks, which provide valuable insights into the origins of magmatic diversity and associated tectonic processes that occurred on the early Earth. Here, we examine three lithologies from the southern Jilin terrane, a major component of the NCC: potassic granites, sanukitoids (granodiorite and diorite), and mafic enclaves (amphibolite and hornblendite). Zircon U-Pb geochronology confirms that these units crystallized around 2510 Ma. The potassic granites exhibit typical geochemical characteristics of crust-derived rocks, indicating that their magma source was related to partial melting of early-formed TTG rocks within a thickened lower crust. Whole-rock geochemistry, Nd isotopes, and zircon Hf isotope data reveal that the amphibolite enclaves formed from mafic magmas derived from partial melting of an enriched lithospheric mantle. In contrast, the hornblendite enclaves are interpreted as altered cumulates that formed through low-pressure (0.6-1.0 GPa) fractionation of 25-45 vol% clinopyroxene and olivine from the amphibolite parental magmas. The sanukitoids contain abundant mafic microgranular enclaves and exhibit disequilibrium textures. These characteristics, together with hybrid geochemical signatures, suggest a magma mixing origin. Geochemical modelling further indicates that the granodiorite and diorite resulted from mixing 70-50 vol% syenogranite with 30-50 vol% amphibolite. These findings, together with previous studies, provide evidence for a Neoarchean subduction-collision-dominated geodynamic mechanism leading to the evolution of continental crust in the northeastern NCC, with localized contributions from mantle plumes.

Numerous questions regarding the formation and evolution of Earth's early continental crust remain unresolved. Ancient rocks are essential to understanding these early geological processes. This study provides new geochronology, geochemistry, and zircon Hf-O isotope data from recently discovered Eoarchean granitoids in the Anshan area of the North China Craton (NCC). Zircon U-Pb dating indicates that these granitoids formed at ca. 3.8 Ga and include both trondhjemitic and monzogranitic gneisses. The trondhjemitic gneisses are characterized by high SiO2 and Na2O contents, low magnesium number (Mg#), low Sr/Y and (La/Yb)N ratios, and slightly negative Eu anomalies. These rocks exhibit enrichment in light rare earth elements (LREE) with flat heavy rare earth element (HREE) patterns. Their zircon epsilon(Hf)(t) values range from -3.34 to + 1.09, with two-stage model ages (T-DM(2)) between 4.43 and 3.99 Ga. The magmatic zircons show delta O-18 values of + 5.33 parts per thousand - +6.98 parts per thousand. These geochemical and Hf-O isotope features suggest that the trondhjemitic gneisses, classified as low-pressure type, likely formed through the partial melting of Hadean to early Eoarchean mafic proto-crust under upper-amphibolite facies conditions. In comparison, the monzogranitic gneisses display higher SiO2 and K2O levels, lower Sr/Y, (La/Yb)(N), and (Gd/Yb)(N) ratios, and more pronounced negative Eu anomalies. These monzogranitic gneisses are enriched in Rb, Th, and U and depleted in Ba, Sr, Nb, P and Ti. Such geochemical traits classify them as highly differentiated granites. Zircon Hf isotope data reveal radiogenic values, with T-DM(2) ages between 4.23 and 4.01 Ga and epsilon(Hf)(t) values ranging from -1.60 to + 0.85. These evidences suggest that the monzogranitic gneisses were derived from the partial melting of ancient felsic source and underwent fractional crystallization during the late stages of magma evolution. The diversity of the ca. 3.8 Ga granitoids indicates the presence of a highly evolved continental crust in the NCC during the early Eoarchean. Hf isotope data show that the earliest crust grew primarily through the partial melting of juvenile crust derived from a depleted mantle, accompanied by certain reworking or recycling of pre-existing continental material. The ca. 3.8 Ga trondhjemitic and monzogranitic gneisses likely formed in an extension environment, such as intraplate rifting setting. Continental crust evolution in the NCC during early Eoarchean was primarily driven by magma underplating associated with asthenospheric mantle upwelling, potentially linked to mantle plume activity. [GRAPHICS] .

The application of zircon U-Pb geochronology, geochemistry, and Hf isotope analysis to the granitoid complex in the Laoling area of southern Jilin Province (SJP) in the northeastern part of the North China Craton can provide valuable insights into its petrogenesis and tectonic setting. The predominant rock types found in SJP granitoid complex encompass monzonitic granite, tonalite, and various other varieties. The zircon U-Pb dating results indicate that the monzonitic granite (N20HT-1-1) crystallized at 2499 +/- 4.2 Ma, the tonalite (N20HT-2-1) at 2722 +/- 30 Ma, and the mylonitized tonalite (PH01-14-2) at 2505 +/- 15 Ma, the monzonitic granite (DA19-3) at 2563 +/- 16 Ma. Through the analysis of Hf isotopes, two-stage depleted mantle model ages, and elemental geochemistry, the inference can be made that tonalite enriched with the residual magmatic zircon are originally formed by the partial melting of similar to 3.4 Ga basaltic crust. Besides, the magmas of the monzonitic granite and mylonitized tonalite were sourced from the partial melting of potassium-rich basaltic rocks and a small amount of metasedimentary units and TTG suite rocks within the lower crust of the Meso- to Neoarchaean (3.1-2.7 Ga) continental framework. Based on this study and previous findings, it can be concluded that there are primarily three phases of magmatic activity in SJP: During the Mid Neoarchaean period (similar to 2.7 Ga), the basaltic crust underwent partial melting due to the tectonic influence of a mantle plume, resulting in the formation and emplacement of tonalite-trondhjemitic magma. In the Late Neoarchaean period (similar to 2.6 Ga), a transition occurred from mantle plume to plate subduction. It was during this time that monzonitic granite began to develop, suggesting the initiation of the plate tectonic system. At the End Neoarchaean period (similar to 2.5 Ga), a significant amount of potassium-rich granite erupted as a result of plate subduction processes. Furthermore, it is worth noting that the tectonic setting for monzonitic granite in SJP indicates a post-orogenic extensional environment, implying that felsic magmatism during this phase is associated with dynamic processes related to arc-continent collision caused by plate subduction followed by subsequent post-collision extension.

Red sand is widely distributed on the west coast of Africa, south of the Sahara, and is an essential material for local engineering construction. Red sand possesses orthostasis and high sensitivity to water, exhibiting characteristics that are different from ordinary sandy soil. Laboratory and in-situ tests were conducted to assess its engineering characteristics, including collapsibility, shear characteristics, and bearing capacity. The water sensitivity of red sand was analyzed along with the images from a scanning electron microscope. The findings indicate that red sand can be classified as silty sand. It demonstrates strong collapsibility, with the collapsibility coefficient decreasing as water content increases. The critical water content for red sand to avoid collapsibility is 13%. The shear strength, internal friction angle, and cohesion of undisturbed and remolded red sand decrease with increasing water content. The critical water content for red sand to lose cohesion is 13%. The bearing capacity and deformation modulus of red sand decrease with increasing water content. Red sand exhibits a softening property, with a softening coefficient of 0.4. The water sensitivity of red sand can be attributed to the cementing effects of fine-grained clay minerals adhering to the surface of large particles or aggregating at particle contacts.

The southward extension of the Bangong-Nujiang Suture and the late Mesozoic tectonic affinity of the Tengchong Block have been subject to debate, and the Early Cretaceous magmatism in the eastern Tengchong Block provides a crucial window to address these issues. This paper reports comprehensive petrographic, geochemical, geochronological, and isotopic data of Early Cretaceous granitic rocks from the eastern Tengchong Block. Results show that these granitic rocks consist of monzogranites and granodiorites, with zircon U-Pb ages of 120.4–113.9 Ma. These granitic rocks are characterized by enrichments in large ion lithophile elements (e.g. Rb, U, K) and light rare earth elements, but depleted in high field strength elements (e.g. Nb, Ta, P, Ti), and have negative apatite εNd(t) values (−10.4 to −6.7) and negative zircon εHf(t) values (−11.7 to −1.2). The molar [Al2O3/(CaO + K2O + Na2O)] (A/CNK) values and whole-rock zircon saturated temperatures of the studied monzogranites of 1.04–1.09 and 714–799°C, respectively, indicate that they have I-type granite affinity. The presence of biotite indicative of I-type granite and the observation that P2O5 decrease with increasing SiO2 further indicated that the monzogranites have affinities of I-type granites. The petrography, geochemical and isotopic signatures of the studied monzogranites indicate that they originated from partial melting of mafic lower crustal rocks. The Na-rich granodiorites have elevated Na2O/K2O ratios and Na2O contents of 1.19–2.04 and 3.12–3.47 wt.%, respectively. These granodiorites also have relatively high Mg# values and the transition metal element Cr of 53.3–54.5 and up to 100 ppm, respectively. According to these isotopic and geochemical features and the occurrence of magnesiohornblende, we propose that the Na-rich granodiorites were derived from partial melting of ancient basaltic lower crust, with certain inputs of mantle materials in the magma source. Considering these results as well as published data, we finally propose that the Tengchong Block was likely the southeastern extension of the Lhasa Block and that these Early Cretaceous granitic rocks were formed in the setting of the volcanic arc due to westward subduction of the Bangong-Nujiang Tethys oceanic lithosphere beneath the Tengchong Block.

A previously unidentified overthrust system has recently been discovered in the Ondor Sum area at the boundary between the Solonker - Xar Moron Suture Zone (SXSZ) and the Early to Mid - Paleozoic Subduction - accretion Belt to the south. The overthrusting occurred during the middle Permian and was overprinted by late Permian to Middle Triassic dextral shearing. The overthrusting (D1) was characterized by the development of WSW - ENE-trending folds and reverse faults, implying NNW - SSE shortening. The later deformation (D2) involved WSW - ENE dextral strike-slip shearing with a minor reverse component, as indicated by slightly plunging striae on slickensides. A comparison of geochronological and structural data for ophiolites in the SXSZ suggests that the overthrust system formed in response to the closure of the Solonker Ocean and the collision along the SXSZ. The earlier NNW - SSE shortening and later WSW - ENE dextral shearing indicate that a tectonic transformation took place along the SXSZ from the middle Permian to the Late Triassic. Dextral and sinistral strike-slip faults are, respectively, distributed to the south and northwest of the Songliao - Xilinhot Block to the north of the SXSZ, implying eastward extrusion of the Songliao - Xilinhot Block after the closure of Solonker Ocean. The tectonic transformation and extrusion might have been a part of the intracontinental tectonic transformation of the eastern segment of the southern Central Asian Orogenic Belt.

The Southwest China was tonically situated in the northern margin of Gondwana continent during the Early Paleozoic, thus the Early Paleozoic magmatic records in this area were closely related to geodynamic evolution of the Proto-Tethys Ocean. In this paper, we present petrography, whole-rock major- and trace-element, LA-ICP-MS zircon U-Pb ages, zircon in situ Hf and apatite Nd isotopic compositions for the Early Paleozoic granites in the Pingda area of Baoshan Block in Southwest Yunnan to decipher their petrogenesis, magma source, and geodynamic mechanism. The LA-ICP-MS U-Pb isotopic analyses of zircons from the granites of Pingda pluton in Baoshan Block show that they were formed during 465.9 similar to 454.9Ma, representing the product of Middle-Late Ordovician magmatic activities. The Pingda pluton is dominantly composed of monzogranite, with main mineral compositions of plagioclase, quartz and alkaline feldspar (perthite and orthoclase), and minor biotite and muscovite. Geochemical analyses show that these monzogranite samples in the Pingda region have high SiO2 (72.16%similar to 76.87%) and Al2O3 (12.50%similar to 14.36%) contents, low MgO (0.12%similar to 0.64%), Mg-# values (20.9 similar to 35.9), Cr and Ni contents, as well as high Rb/Sr and Rb/Ba ratios. Together with their relatively high A/CNK values (1.06 similar to 1.45), these monzogranites belong to the weakly peraluminous to strongly peraluminous series, indicating a S-type granite affinity. In addition, the monzogranite samples of Pingda pluton have low Al2O3/TiO2 ratios and varying CaO/Na2O, Rb/Sr and Rb/Ba ratios, indicating that the studied granites represent partial melting products of heterogeneous sources with variable proportions of pelite and psammite rocks. Furthermore, these monzogranite samples have variable zircon epsilon(Hf)(t) values (-11.10 similar to-4.05), apatite epsilon(Nd)(t) values (-8.76 similar to-6.96), and heterogeneous two-stage model ages (2140 similar to 1704Ma), indicating that their magma source was dominant by Paleoproterozoic pelite and psammite rocks. Combined with widely distributed Early Paleozoic magmatic rocks and contemporaneous ophiolitic melange records in this area, we argue that the Early Paleozoic S-type granites in the Baoshan Block were originated from partial melting of crustal sedimentary rocks, indicating an active continental margin setting related to westward subduction of the Proto-Tethys Ocean.

Abstract The geodynamic processes that formed Earth’s earliest continents are intensely debated. Particularly, the transformation from ancient crustal nuclei into mature Archaean cratons is unclear, primarily owing to the paucity of well-preserved Eoarchaean–Palaeoarchaean ‘protocrust’. Here, we report a newly identified Palaeoarchaean continental fragment—the Baishanhu nucleus—in northeastern North China Craton. U–Pb geochronology shows that this nucleus preserves five major magmatic events during 3.6–2.5 Ga. Geochemistry and zircon Lu–Hf isotopes reveal ancient 4.2–3.8 Ga mantle extraction ages, as well as later intraplate crustal reworking. Crustal architecture and zircon Hf–O isotopes indicate that proto-North China first formed in a stagnant/squishy lid geodynamic regime characterised by plume-related magmatic underplating. Such cratonic growth and maturation were prerequisites for the emergence of plate tectonics. Finally, these data suggest that North China was part of the Sclavia supercraton and that the Archaean onset of subduction occurred asynchronously worldwide.

The geodynamic regime that governed the crustal evolution of Earth during the early Archean remains intensely debated. The North China Craton (NCC) preserves a geological history spanning 3.8-2.5 Ga, particularly in the Anshan area, making it an ideal natural laboratory for probing the formation and evolution of the NCC and its associated geodynamic regime. Here, we document new geochronology, geochemistry, and zircon Hf-O isotope data from newly discovered Paleoarchean meta -mafic rocks in the Anshan area. Based on their whole -rock geochemistry, these unit can be divided into tholeiitic and komatiitic series. Of which, the komatiitic rocks are characteristic by high MgO contents (up to 20.6 wt%). Zircon U-Pb dating shows that all meta -mafic rocks formed contemporaneously, with crystallization ages of ca. 3.3 Ga. Most of the studied meta -mafic rocks display radiogenic zircon Hf isotopes, with T DM1 ages ranging from 3592 to 3346 Ma and epsilon Hf ( t ) values from -1.94 to + 3.49. They also exhibit mantle -like zircon delta 18 O values (+4.92 %o to + 5.98 %o). These zircon Hf-O isotope data indicate that the protoliths of the ca. 3.3 Ga meta -mafic rocks originated from the partial melting of a depleted mantle without significant crustal contamination. Furthermore, the parental magmas of the komatiitic rocks and some of tholeiitic rocks were generated from 20 % and 5-10 % partial melting of spinel-lherzolite, respectively, whereas other tholeiitic rocks were the result of a low degree (1-5 %) of partial melting of spinel-garnet lherzolite. The ca. 3.3 Ga tholeiitic-komatiitic rocks were most likely formed in an intraplate rifting setting, associated with a mantle plume.

The most striking Lincang granitic batholith widely distributed in the Sanjiang Paleo-Tethys Orogen provides us a crucial window to understand the subduction, consumption, and associated geodynamic mechanism of the Paleo-Tethys Ocean during the late Paleozoic to early Mesozoic. In this study, we carry out an integrated study of petrology, zircon U-Pb geochronology, whole-rock major and trace elements, and in situ zircon Hf isotope of the Late Triassic granitic rocks from the Lincang granitic batholith, with the aim of investigating their geochronological framework, spatio-temporal variations, genetic mechanism, and tectonic significance. The granitic rocks presented in this study consist of granodiorite and monzogranite, with minor syenogranite. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U-Pb dating of these granitic rocks yield crystallization ages of 237.6-209.0 Ma, indicating multi-stage granitic magmatic activities during the Late Triassic. Geochemical analyses show that these granitic rocks belong to medium-K calc-alkaline and shoshonite series, and have metaluminous to peraluminous characteristics and low whole-rock zircon saturation temperature (726-834 degrees C). The Late Triassic granitic rocks show transitional characteristics and originate from different magma sources, indicative of transitional I-type and S-type granite affinities. The 237.6 Ma gneissic granodiorites belong to I-type granite and have typical continental arc granites of enrichments in large ion lithophile elements (Rb, K, Pb, and Th) and light rare earth elements (LREEs), and depletion in high field strength elements (Nb, Ta, Ba, Ti, and P) and heavy rare earth elements (HREEs), with parental magma derived from garnet amphibolite facies lower crust. Whereas the 222.7-209.0 Ma granitic rocks have S-type granite affinities with psammitic source. The transitional geochemical characteristics led us to favour that syn-collisional stage in response to final closure of the Paleo-Tethys Ocean in Southwestern Yunnan lasted at least until 237.6 Ma. Subsequent extensional mechanism and associated asthenosphere upwelling after final closure of the Paleo-Tethys Ocean induce large-scale partial melting of the middle-lower crust, resulting in voluminous generation of S-type and A-type granitic rocks and associated volcanic rocks in Southwestern Yunnan. [GRAPHICAL ABSTRACT]

The question of which specific tectonic regimes played an essential role in shaping the Neoarchean evolution of the North China Craton (NCC) has been a contentious and controversial topic. Mafic rocks, containing valuable geochemical information from the mantle and deep crust, serve as an important source of data to provide essential constraints on above issue. This study presents bulk-rock geochemistry, zircon U-Pb geochronology and Hf-Nd isotopes for the Neoarchean mafic rocks in the core area of the Longgang Block of the NCC. Petrographically, these mafic rocks are composed of the amphibolite and metadiabase. Zircon U-Pb dating results revealed that they were synchronously emplaced at ca. 2.5 Ga. Geochemically, the amphibolites belong to subalkaline tholeiite series, exhibiting enrichment in light rare earth elements (LREEs), intensely negative Nb, Ta and Ti anomalies, and slightly enriched Nd and relatively variable zircon Hf isotopic compositions. These geochemical and isotopic features show large affinity to arc-like magmatism, implying that they were derived from subduction-related metasomatized lithospheric mantle. In contrast, the metadiabases exhibit high-Ti alkaline basalt affinities, OIB-like REE, and trace element patterns. They also show clearly positive Nb, Ta and Ti anomalies, indicating that they originated from a mantle plume-related tectonic environment. The new geochemical and isotopic data reveal that these Neoarchean mafic rocks could have resulted from coexisting mantle plume and subduction processes. Combined with available regional structural, geochemical, and metamorphic data, it is likely that during the Neoarchean, both a mantle plume and subduction jointly controlled the crustal growth and tectonic evolution of the Longgang Block in the eastern NCC.