Mesoproterozoic (ca. 1.3 Ga) A-Type Granites on the Northern Margin of the North China Craton: Response to Break-Up of the Columbia Supercontinent

: Mesoproterozoic (ca. 1.3 Ga) magmatism in the North China Craton (NCC) was dominated by mafic intrusions (dolerite sills) with lesser amounts of granitic magmatism, but our lack of knowledge of this magmatism hinders our understanding of the evolution of the NCC during this period. This study investigated porphyritic granites from the Huade–Kangbao area on the northern margin of the NCC. Zircon dating indicates the porphyritic granites were intruded during the Mesoproterozoic between 1285.4 ± 2.6 and 1278.6 ± 6.1 Ma. The granites have high silica contents (SiO 2 = 63.10–73.73 wt.%), exhibit alkali enrichment (total alkalis = 7.71–8.79 wt.%), are peraluminous, and can be classified as weakly peraluminous A2-type granites. The granites have negative Eu anomalies ( δ Eu = 0.14–0.44), enrichments in large-ion lithophile elements (LILEs; e.g., K, Rb, Th, and U), and depletions in high-field-strength elements (HFSEs; e.g., Nb, Ta, and Ti). ε Hf (t) values range from –6.43 to +2.41, with t DM2 ages of 1905–2462 Ma, suggesting the magmas were derived by partial melting of ancient crustal material. The geochronological and geochemical data, and regional geological features, indicate the Mesoproterozoic porphyritic granites from the northern margin of the NCC formed in an intraplate tectonic setting during continental extension and rifting, which represents the response of the NCC to the break-up of the Columbia supercontinent


Introduction
The assembly and break-up of supercontinents are fundamental processes in Earth's history and have affected continent formation and destruction, the global climate, biological evolution, and large-scale mineralization events.Over the past two decades, this field has become an important area of research [1,2].Geological records indicate the past occurrence of at least four supercontinents: Kenorland, Columbia, Rodinia, and Pangaea [3][4][5].The Columbia supercontinent was assembled by a series of global-scale collisional events during 2.1-1.8Ga [6,7] and was subsequently affected by rifting from the Paleoproterozoic to Mesoproterozoic (1.8-1.3Ga), followed by break-up at 1.3-1.2Ga [2,6].During this period, Columbia experienced extensive rifting, mafic magmatism, and numerous tectonothermal events [2,8,9].
The North China Craton (NCC) was a key part of the Columbia supercontinent and encompassed both the Palaeoproterozoic Khondalite Belt (ca.1.95 Ga) and the Central

Geological Setting
The NCC is located in eastern China and is bordered by the Xingmeng orogenic belt to the north and the Qinling-Dabie orogenic belt to the south (Figure 1).The NCC is one of the oldest cratons in the world and consists primarily of Precambrian crystalline basement that is overlain by thick sedimentary cover rocks [22,23].The formation of the crystalline basement of the NCC involved mainly three processes: (1) the formation of multiple dispersed continental nuclei; (2) the amalgamation of micro-blocks; and (3) cratonization [24,25].The Eastern and Western blocks collided along the Trans-North China orogen at ca. 1.85 Ga, leading to the final assembly of the NCC basement and its incorporation into Columbia.The Precambrian basement consists mainly of Neoarchaean-Palaeoproterozoic TTG (Tonalite-Trondhjemite-Granodiorite) rocks and 2.6-2.5 Ga granulites, amphibolites, and mafic-ultramafic intrusions [18,26].The NCC was located on the edge of the Columbia supercontinent and adjacent to the Indian Craton [3].During the middle to late Proterozoic, the NCC underwent large-scale extension.During this period, a radial swarm of mafic dykes formed during 1.78-1.68Ga, and there were multiple periods of rifting, including the formation of the Yanliao, Xiong'er, and Zhaertei-Baiyunebo-Huade rifts in the NCC.The NCC experienced a period of magmatic quiescence at 1.6-1.4Ga.The magmatism in the NCC at 1.4-1.3Ga is mainly represented by dolerite sills and granites.The dolerite sills occur primarily in the Yanliao region, over an area that is >600 km long and 200 km wide, constituting a mafic large igneous province.The 1.3 Ga granites in the NCC are located mainly in the Shangdu area, Inner Mongolia [2].The present study area is located at the northern margin of the NCC.Sedimentary rocks that crop out in the north of this area include the Mesoproterozoic Baoyintu Group, and lower Permian Sanmianjing and Elitu formations.Sedimentary rocks that crop out in the south of this area include the Mesoproterozoic Huade Group, with smaller exposures of the Middle Jurassic Tuchengzi Formation and Lower Cretaceous Zhangjiakou Formation.The Mesoproterozoic intrusions are located mainly in the northern area and trend NE-SW.Some of the intrusions have been mylonitized due to the activity of ENE-WSWtrending ductile shear zones (Figure 2).The present study area is located at the northern margin of the NCC.Sedimentary rocks that crop out in the north of this area include the Mesoproterozoic Baoyintu Group, and lower Permian Sanmianjing and Elitu formations.Sedimentary rocks that crop out in the south of this area include the Mesoproterozoic Huade Group, with smaller exposures of the Middle Jurassic Tuchengzi Formation and Lower Cretaceous Zhangjiakou Formation.The Mesoproterozoic intrusions are located mainly in the northern area and trend NE-SW.Some of the intrusions have been mylonitized due to the activity of ENE-WSW-trending ductile shear zones (Figure 2).The present study area is located at the northern margin of the NCC.Sedimentary rocks that crop out in the north of this area include the Mesoproterozoic Baoyintu Group, and lower Permian Sanmianjing and Elitu formations.Sedimentary rocks that crop out in the south of this area include the Mesoproterozoic Huade Group, with smaller exposures of the Middle Jurassic Tuchengzi Formation and Lower Cretaceous Zhangjiakou Formation.The Mesoproterozoic intrusions are located mainly in the northern area and trend NE-SW.Some of the intrusions have been mylonitized due to the activity of ENE-WSWtrending ductile shear zones (Figure 2).

Field Outcrops, and Petrology, and Mineralogy
Granitic samples were collected from the Huade area in Inner Mongolia and the Kangbao area in Hebei Province.Field investigations were conducted on the Xiaoyingtu, Chahan, and 1488 Highland intrusions in the study areas.These intrusions are stocks, with irregular elliptical shapes and spheroidal weathering (Figure 3a-e).Elliptical diorite xenoliths occur within the intrusions (Figure 3d).

Field Outcrops, and Petrology, and Mineralogy
Granitic samples were collected from the Huade area in Inner Mongolia and the Kangbao area in Hebei Province.Field investigations were conducted on the Xiaoyingtu, Chahan, and 1488 Highland intrusions in the study areas.These intrusions are stocks, with irregular elliptical shapes and spheroidal weathering (Figure 3a-e).Elliptical diorite xenoliths occur within the intrusions (Figure 3d).

Xiaoyingtu Pluton
The Xiaoyingtu pluton consists mainly of porphyritic granodiorite and is located in the central-eastern part of the study area over an exposed area of 18.30 km 2 (Figure 3b).The granodiorite is grey-yellow in color with a porphyritic texture and massive structure and consists mainly of plagioclase (50 vol.%),K-feldspar (25 vol.%), quartz (20 vol.%), and biotite and muscovite (5 vol.%).The samples are plotted in the granodiorite and quartz monzonite fields on the granite total alkalis-SiO2 (TAS) diagram.Plagioclase phenocrysts range in size from 0.5 × 0.8 to 1 × 2 cm and are euhedral-subhedral, and they exhibit occasional multiple twinning.The quartz in the matrix is granular with a grain size of 2-4 mm.Plagioclase is euhedral-subhedral with grain sizes of 1 × 3 to 2 × 5 mm, and the distribution of biotite defines banding in the granodiorite (Figure 3f).

Xiaoyingtu Pluton
The Xiaoyingtu pluton consists mainly of porphyritic granodiorite and is located in the central-eastern part of the study area over an exposed area of 18.30 km 2 (Figure 3b).The granodiorite is grey-yellow in color with a porphyritic texture and massive structure and consists mainly of plagioclase (50 vol.%),K-feldspar (25 vol.%), quartz (20 vol.%), and biotite and muscovite (5 vol.%).The samples are plotted in the granodiorite and quartz monzonite fields on the granite total alkalis-SiO 2 (TAS) diagram.Plagioclase phenocrysts range in size from 0.5 × 0.8 to 1 × 2 cm and are euhedral-subhedral, and they exhibit occasional multiple twinning.The quartz in the matrix is granular with a grain size of 2-4 mm.Plagioclase is euhedral-subhedral with grain sizes of 1 × 3 to 2 × 5 mm, and the distribution of biotite defines banding in the granodiorite (Figure 3f).

Chahan Intrusion
The Chahan intrusion crops out over an area of 20.47 km 2 in the central part of the study area and consists of fine-medium-grained porphyritic biotite syenogranite and medium-coarse-grained porphyritic biotite syenogranite.The biotite syenogranite is light grey-brown in color with a porphyritic texture and massive structure.The phenocrysts are K-feldspar, which are subhedral and have grain sizes of 0.4 × 1 to 0.5 × 2.5 cm and comprise ~10 vol.% of the sample.The matrix consists predominantly of K-feldspar (50 vol.%), plagioclase (15 vol.%), quartz (20 vol.%), and biotite (5 vol.%), with grain sizes of 2-4 mm.K-feldspar is subhedral and primarily microcline.Plagioclase is subhedraleuhedral and zoned, while biotite exhibits localized chloritization (Figure 3g-h).

Highland Intrusion
The 1488 Highland intrusion is located in the central part of the study area and is a stock that has an outcrop area of 7.07 km 2 .The intrusion consists mainly of fine-grained porphyritic biotite monzogranite and itself has been intruded by the Chahan intrusion.The sample is yellow-brown in color and has a porphyritic texture and massive structure.It consists of K-feldspar (35 vol.%), plagioclase (40 vol.%), quartz (20 vol.%), biotite (5 vol.%), and minor muscovite and garnet.The phenocrysts are primarily subhedral microcline and minor amounts of plagioclase, which have grain sizes of 5-10 mm.Plagioclase occurs as subhedral crystals with grain sizes of 2-5 mm that occasionally exhibit zoning.Biotite has a weak shape-preferred orientation and a grain size of 0.2-2.0mm (Figure 3i).

Sampling and Methodology
Whole-rock geochemical and zircon U-Pb dating and Hf isotope analyses were carried out on samples of the Xiaoyingtu, Chahancun, and 1488 Highland intrusions.

Whole-Rock Geochemistry
Whole-rock geochemical analysis was undertaken at the Regional Geological and Mineral Survey Institute, Hebei, China, using national standards and relevant industry analytical techniques.The analyzed samples were silicate rock samples, along with standards and blanks.Approximately 50 mg of representative sample material was weighed and placed in the inner container of a closed sample digestion vessel.Subsequently, 1 mL of HF and 0.5 mL of HNO 3 were added to the sample.The vessel was sealed and placed in an oven at a temperature of 190 • C for 24 h.After cooling, the inner container was removed and heated to 200 • C on a hotplate to evaporate the acids.Finally, 0.5 mL of HNO 3 was added and evaporated.This step was repeated and then an extra 5 mL of HNO 3 was added and the container was sealed and held at 130 • C for 3 h.After cooling, the container was opened, and the contents were transferred to a cleaned plastic bottle and diluted with 50 mL of water.The mixture was shaken thoroughly before determining the trace element contents by inductively coupled plasma-mass spectrometry (ICP-MS).
The major elements were determined by X-ray fluorescence spectrometry.Approximately 0.8 g of sample was weighed into a 25 mL porcelain crucible, along with an 8 g mixture of anhydrous lithium tetraborate and lithium fluoride.The mixture was then transferred into a Pt-Au crucible and melted and cooled into a fused glass disc.For the Fe analyses, ~0.3 g of sample was weighed and placed in a Pt crucible.The sample was wetted with water, and 5 mL of HF and 10 mL of H 2 SO 4 were added.The crucible was covered, placed in a pre-heated electric furnace, heated and boiled for 10 min, removed from the furnace, and immediately placed in 200 mL of water containing 25 mL of saturated boric acid.For the loss-on-ignition analyses, 15 mL of thiophosphoric acid and two drops of 1% sodium diphenylamine sulfonate solution were added.Approximately 1.0 g of the sample was weighed into a porcelain crucible.The crucible was placed in a muffle furnace and heated at 980 • C for 2 h.After heating, the crucible was removed, transferred to a desiccator, allowed to cool to room temperature for 30 min, and then weighed.The ignition process was then repeated for an additional 30 min and the crucible weighed again until a constant weight was achieved.

Zircon U-Pb Ages and Lu-Hf Isotopic Compositions
The zircon grains were separated and analyzed at the Hebei Regional Geological and Mineral Survey Institute.Subsequently, the zircons were subjected to cathodoluminescence (CL) imaging, U-Pb dating, and in situ Lu-Hf isotopic analysis at the Tianjin Geological Survey Center, China Geological Survey, Tianjin, China.The U-Pb dating was undertaken with a laser ablation (LA) system coupled to an ICP-MS (Agilent 7900) instrument (Agilent Technologies, Santa Clara, CA, USA).A RESOlution LR (ASI) LA system comprising a 193 nm ArF excimer laser was used for the analyses.Ages and concordia diagrams were obtained with Isoplot 3.0 [27].Hafnium isotopes were determined with an LA-multiplecollector-ICP-MS (LA-MC-ICP-MS) system.The LA system was a 193 nm ArF excimer laser (model UP193-FX; ESI Company, Santa Rosa, CA, USA).The MC-ICP-MS was a Neptune Plus (a product of Thermo Fisher Scientific, which is headquartered in Waltham, MA, USA).The Hf isotope data were processed using ICPMSDataCal 9.2 software.The laser beam diameter was 50 µm, the laser energy density was 3.5 J/cm 2 , and the laser frequency was 8 Hz.The ablation time was 40 s, and the ablated material was transported into the mass spectrometer using He gas.
Minerals 2023, 13, x FOR PEER REVIEW 6 of 20 process was then repeated for an additional 30 min and the crucible weighed again until a constant weight was achieved.

Zircon U-Pb Ages and Lu-Hf Isotopic Compositions
The zircon grains were separated and analyzed at the Hebei Regional Geological and Mineral Survey Institute.Subsequently, the zircons were subjected to cathodoluminescence (CL) imaging, U-Pb dating, and in situ Lu-Hf isotopic analysis at the Tianjin Geological Survey Center, China Geological Survey, Tianjin, China.The U-Pb dating was undertaken with a laser ablation (LA) system coupled to an ICP-MS (Agilent 7900) instrument.A RESOlution LR (ASI) LA system comprising a 193 nm ArF excimer laser was used for the analyses.Ages and concordia diagrams were obtained with Isoplot 3.0 [27].Hafnium isotopes were determined with an LA-multiple-collector-ICP-MS (LA-MC-ICP-MS) system.The LA system was a 193 nm ArF excimer laser (model UP193-FX; ESI Company, USA).The MC-ICP-MS was a Neptune Plus (a product of Thermo Fisher Scientific, which is headquartered in Waltham, United States).The Hf isotope data were processed using ICPMSDataCal 9.2 software.The laser beam diameter was 50 µm, the laser energy density was 3.5 J/cm², and the laser frequency was 8 Hz.The ablation time was 40 s, and the ablated material was transported into the mass spectrometer using He gas.
The U-Pb ages exhibit limited variations (Figure 5).The U-Pb ages for sample U-Pb2020054 range between 1270 ± 14 and 1285 ± 13 Ma, with a weighted mean age of 1282.2 ± 3. The CL images reveal oscillatory zoning, indicative of a magmatic origin.The U and Th contents are 248.93-769.10 and 17.91-308.87ppm, respectively, with Th/U = 0.07-0.51,which are also consistent with a magmatic origin [28].The U-Pb ages exhibit limited variations (Figure 5).The U-Pb ages for sample U-Pb2020054 range between 1270 ± 14 and 1285 ± 13 Ma, with a weighted mean age of 1282.

Major Elements
The SiO2 contents of the analyzed samples range from 63.10 to 73.73 wt.%.The total alkali (K2O + Na2O) contents are 6.28-8.79wt.% (Figure 6a).The results are listed in Table A2.The Al2O3 contents are 12.04-17.64wt.%, with an average of 14.54 wt.%.The A/CNK ratios are >1.0 (1.07-1.90;average = 1.22).Sample 2021037 has A/CNK > 1.90, potentially due to late-stage metamorphism, which led to the development of metamorphic minerals such as andalusite and sillimanite.The A/NK values range from 1.24 to 2.33, with an average of 1.54.All samples are plotted in the peraluminous field in an A/CNK versus A/NK diagram (Figure 6b).In a SiO₂-FeOT/(FeOT + MgO) diagram (Figure 6c), most samples are plotted in the magnesian granite field.In a SiO₂-K₂O diagram (Figure 6d), the samples are plotted in the shoshonite field.

Trace Elements
The total rare earth element (∑REE) contents of the analyzed samples vary between 168.85 and 690.06 ppm, with an average of 374.64 ppm and significant variations between samples.The samples exhibit enrichments in light REE and depletions in heavy REE (Figure 7a), with ratios of light to heavy REE of 7.46-24.0.(La/Yb)N ratios vary from 5.37 to 61.49, with an average of 22.87.The chondrite-normalized REE patterns exhibit negative Eu anomalies (δEu = 0.14-0.54),indicative of plagioclase fractionation.In a primitive-mantle-normalized multi-element diagram (Figure 7b), the samples are enriched in large-ion lithophile elements (LILEs; e.g., K and U) and exhibit small negative Zr and large negative Ti anomalies.In general, the trace element patterns of the studied granites are similar, indicating the granites are cogenetic.[32]).Literature data from Zhang Shuanhong, 2014 [33]; Meng Baohang, 2016 [34]; Phase Vibration Group, 2020 [14].

Trace Elements
The total rare earth element (∑REE) contents of the analyzed samples vary between 168.85 and 690.06 ppm, with an average of 374.64 ppm and significant variations between samples.The samples exhibit enrichments in light REE and depletions in heavy REE (Figure 7a), with ratios of light to heavy REE of 7.46-24.0.(La/Yb) N ratios vary from 5.37 to 61.49, with an average of 22.87.The chondrite-normalized REE patterns exhibit negative Eu anomalies (δEu = 0.14-0.54),indicative of plagioclase fractionation.In a primitive-mantle-normalized multi-element diagram (Figure 7b), the samples are enriched in large-ion lithophile elements (LILEs; e.g., K and U) and exhibit small negative Zr and large negative Ti anomalies.In general, the trace element patterns of the studied granites are similar, indicating the granites are cogenetic.[35].Literature data from Zhang Shuanhong, 2014 [33]; Meng Baohang, 2016 [34]; Phase Vibration Group, 2020 [14].

Zircon Hf Isotopes
Hafnium isotopic compositions were determined for zircons in one granite sample (2021055).The results are listed in Table A3.The geochemical properties of Hf are similar to those of Zr, and Hf readily substitutes for Zr in the zircon crystal lattice, which results in low zircon Lu/Hf ratios.As such, the 176 Hf/ 177 Hf ratio changes little over time due to the in situ Minerals 2024, 14, 622 9 of 19 decay of 176 Lu.Therefore, magmatic zircon effectively retains the initial 176 Hf/ 177 Hf ratio of the melt it crystallizes from [36].The zircon 176 Lu/ 177 Hf ratios (Figure 8b) range between 0.0004 and 0.0017, and 176 Hf/ 177 Hf ratios vary between 0.281807 and 0.282080. 176Yb/ 177 Hf ratios are 0.0155-0.0671.Zircon f Lu/Hf and ε Hf (t) values and T DM1 and T DM2 ages vary from -0.98 to -0.95, -6.43 to +2.41, 1676 to 2022 Ma, and 1905 to 2462 Ma (Figure 8a), respectively.

Zircon Hf Isotopes
Hafnium isotopic compositions were determined for zircons in one granite sample (2021055).The results are listed in Table A3.The geochemical properties of Hf are similar to those of Zr, and Hf readily substitutes for Zr in the zircon crystal lattice, which results in low zircon Lu/Hf ratios.As such, the 176 Hf/ 177 Hf ratio changes little over time due to the in situ decay of 176 Lu.Therefore, magmatic zircon effectively retains the initial 176 Hf/ 177 Hf ratio of the melt it crystallizes from [36].The zircon 176 Lu/ 177 Hf ratios (Figure 8b) range between 0.0004 and 0.0017, and 176 Hf/ 177 Hf ratios vary between 0.281807 and 0.282080. 176Yb/ 177 Hf ratios are 0.0155-0.0671.Zircon fLu/Hf and εHf(t) values and TDM1 and TDM2 ages vary from -0.98 to -0.95, -6.43 to +2.41, 1676 to 2022 Ma, and 1905 to 2462 Ma (Figure 8a), respectively.

Magma Sources and Evolution
There are eight main hypotheses regarding the origins of A-type granites [39]: (1) differentiation of alkaline magmas derived from the mantle, resulting in residual A-type granitic melts [38,40]; (2) extreme differentiation of tholeiitic magma derived from the mantle or low-degree partial melting of tholeiitic rocks [41][42][43]; (3) interaction of alkali magmas derived from the mantle with crustal materials, leading to the formation of a syenitic magma source area, which is further differentiated or mixed with crustal materials [44,45]; (4) partial melting of F-rich granulite residue after extraction of I-type granitic magma from the lower crust [37]; (5) direct melts of igneous crustal rocks (i.e., tonalite and granodiorite) [46]; (6) melting of crustal rocks due to magmatic underplating [47,48]; (7) partial melting of lower crustal rocks due to the addition of volatiles from the mantle [49]; and (8) mixing between crust-and mantle-derived magmas [50].
The absence of coeval (ultra)mafic rocks precludes the involvement of mantle-derived (alkali) basalt magma.The granite samples have high SiO 2 and Na 2 O + K 2 O contents, and low TiO 2 , total Fe 2 O 3 , and MgO contents.A/CNK ratios indicate the granites are strongly peraluminous.The depletions in Nb, Ta, Sr, and Ti and enrichments in K, Rb, Th, and U in the granites suggest their parental melt(s) were derived from the crust [51].ε Hf (t) values of -1.08 to -6.43 (except one analysis of 2.41) are indicative of a crustal source.The zircon T DM1 ages of 1676-2022 Ma (average = 1864 Ma) correspond to a period of uplift and rifting of NCC basement, and anorogenic magmatism.The zircon T DM2 ages of 1905-2462 Ma are consistent with the timing of development of the Palaeoproterozoic orogenic belt in the NCC [52].Harker diagrams (Figure 10) exhibit negative linear correlations for TiO 2 , MgO, and Al 2 O 3 .Furthermore, the trace element patterns all exhibit depletions in Ba, Nb, Ta, Sr, Ti, and Eu, indicating the sources of the granites were similar and that the generated magmas underwent significant fractional crystallization.In conclusion, the Mesoproterozoic granites were generated by the melting of crustal rocks due to magmatic underplating, and the parental magmas underwent significant crystal fractionation.
magmas derived from the mantle with crustal materials, leading to the formation of a syenitic magma source area, which is further differentiated or mixed with crustal materials [44,45]; (4) partial melting of F-rich granulite residue after extraction of I-type granitic magma from the lower crust [37]; (5) direct melts of igneous crustal rocks (i.e., tonalite and granodiorite) [46]; (6) melting of crustal rocks due to magmatic underplating [47,48]; (7) partial melting of lower crustal rocks due to the addition of volatiles from the mantle [49]; and (8) mixing between crust-and mantle-derived magmas [50].
The absence of coeval (ultra)mafic rocks precludes the involvement of mantle-derived (alkali) basalt magma.The granite samples have high SiO2 and Na2O + K2O contents, and low TiO2, total Fe2O3, and MgO contents.A/CNK ratios indicate the granites are strongly peraluminous.The depletions in Nb, Ta, Sr, and Ti and enrichments in K, Rb, Th, and U in the granites suggest their parental melt(s) were derived from the crust [51].εHf(t) values of -1.08 to -6.43 (except one analysis of 2.41) are indicative of a crustal source.The zircon TDM1 ages of 1676-2022 Ma (average = 1864 Ma) correspond to a period of uplift and rifting of NCC basement, and anorogenic magmatism.The zircon TDM2 ages of 1905-2462 Ma are consistent with the timing of development of the Palaeoproterozoic orogenic belt in the NCC [52].Harker diagrams (Figure 10) exhibit negative linear correlations for TiO2, MgO, and Al2O3.Furthermore, the trace element patterns all exhibit depletions in Ba, Nb, Ta, Sr, Ti, and Eu, indicating the sources of the granites were similar and that the generated magmas underwent significant fractional crystallization.In conclusion, the Mesoproterozoic granites were generated by the melting of crustal rocks due to magmatic underplating, and the parental magmas underwent significant crystal fractionation.

Tectonic Setting
The ca. 1.30 Ga magmatism along the northern margin of the NCC includes dolerite dykes and sills in the eastern part of the Yanliao rift, the Shangdu-Huade-Kangbao granite, and the Baiyun Obo carbonatite.Dolerite sills (1.33-1.30Ga) associated with

Tectonic Setting
The ca. 1.30 Ga magmatism along the northern margin of the NCC includes dolerite dykes and sills in the eastern part of the Yanliao rift, the Shangdu-Huade-Kangbao granite, and the Baiyun Obo carbonatite.Dolerite sills (1.33-1.30Ga) associated with continental rifting have intruded the Shimaling, Tieling, Wumoushan, and Gaoqizhuang formations in the northern NCC [5,9,14].In addition, 1.3 Ga carbonatite and mafic dykes occur in the Baiyun Obo area.Previous studies of carbonatites in the Baiyun Obo area, middle Mesoproterozoic granites, and large-scale dolerite sills from the northern margin of the NCC indicate that rifting persisted until the middle Mesoproterozoic [53,54].
The studied Mesoproterozoic granites are peraluminous A-type granites, and most studies consider that A-type granites form in extensional tectonic settings, such as those associated with post-orogenic extension, continental margins, and intraplate rifts.The Mesoproterozoic A-type granites have REE characteristics indicative of a crustal origin, similar to intraplate granites formed by the melting of continental crust.Eby [39] categorized A-type granites into two sub-types, A1 and A2.The A1 sub-type is thought to be derived by the differentiation of ocean island basalt magma, while the A2 sub-type may be derived by the interaction between mantle-derived magmas and continental crust.Granite samples from the study area plot in the A2 field in Nb-Y-Ce and Nb-Y-3Ga diagrams, indicating their formation in a stable extensional setting during the late stages of an orogeny.Pearce [55] used Yb + Ta-Rb, Nb + Y-Rb, Yb-Ta, and Y-Nb diagrams to identify the tectonic settings of granitic magmas.Most of the studied granites plot in the post-collisional to intraplate fields in these diagrams (Figure 11a-d).Therefore, the Mesoproterozoic granites were formed in an intraplate tectonic setting during continental extension and rifting.
derived by the differentiation of ocean island basalt magma, while the A2 sub-type may be derived by the interaction between mantle-derived magmas and continental crust.Granite samples from the study area plot in the A2 field in Nb-Y-Ce and Nb-Y-3Ga diagrams, indicating their formation in a stable extensional setting during the late stages of an orogeny.Pearce [55] used Yb + Ta-Rb, Nb + Y-Rb, Yb-Ta, and Y-Nb diagrams to identify the tectonic settings of granitic magmas.Most of the studied granites plot in the postcollisional to intraplate fields in these diagrams (Figure 11a-d).Therefore, the Mesoproterozoic granites were formed in an intraplate tectonic setting during continental extension and rifting.[55]).WPG-within plate granite; ORG-ocean ridge granite; VAGvolcanic arc granite; syn-COLG-syn-collision granite; Post-CEG-post collision granite.

Relationship to the Break-Up of Columbia
The ca. 1.3 Ga magmatism was global in extent, suggesting the extensional/rifting event during this period was a global phenomenon.Mafic dyke swarms ranging in age from 1.3 to 1.2 Ga have been identified in the Mackenzie Mountains in Canada, the Săo Francisco craton in southeastern Brazil, and Australia [16,56,57].In addition to mafic magmatism during the middle Mesoproterozoic along the northern margin of the NCC, granites were formed at this time in the study area and surrounding regions due to continental extension and rifting [8,[18][19][20]53].These late Mesoproterozoic dolerites, granites, and carbonatites form a bimodal magmatic assemblage in the NCC associated with the late-stage breakup of Columbia.Palaeomagnetic data for the period 1.77-1.50Ga have shown that the palaeomagnetic poles of the NCC closely resemble those of North America (Laurentia) and Siberia [58].However, during 1.35-1.20Ga, the palaeomagnetic poles of North China exhibited a ~90 • rotation relative to Laurentia (North America; [58]).Evans et al. [59] reconstructed the initial fragmentation of the Mesoproterozoic Columbia supercontinent based on tectonic, stratigraphic, and palaeomagnetic data for Siberia, Laurentia, and Baltica (Figure 12).Their findings indicate that the southern and eastern margins of Siberia were directly adjacent to the Urals margin of Baltica.Furthermore, they proposed the NCC may have fully separated from Columbia during the middle Mesoproterozoic (1.50-1.27Ga).

Ga).
In summary, it can be inferred that the Mesoproterozoic dolerite dykes along the northern margin of the NCC represent magmas derived from the mantle during continental rifting, whereas the granites represent the melting of the ancient crust.Both types of magmatism were related to the break-up of Columbia.The initial fragmentation of Columbia in different cratons may have varied in time.However, the ca.1.30 Ga magmatic event in the study area likely corresponds to the last break-up phase of Columbia and highlights the response of the NCC to this final break-up event.In summary, it can be inferred that the Mesoproterozoic dolerite dykes along the northern margin of the NCC represent magmas derived from the mantle during continental rifting, whereas the granites represent the melting of the ancient crust.Both types of magmatism were related to the break-up of Columbia.The initial fragmentation of Columbia in different cratons may have varied in time.However, the ca.1.30 Ga magmatic event in the study area likely corresponds to the last break-up phase of Columbia and highlights the response of the NCC to this final break-up event.

1.
(Zircon U-Pb ages of porphyritic granites in the central part of the northern margin of the NCC range from 1285.4 ± 2.6 to 1278.6 ± 6.1 Ma; these are the same within error.

2.
The Mesoproterozoic granites are weakly peraluminous A2-type granites.Trace element data suggest they were formed by partial melting of ancient crustal materials and may have formed in an intraplate tectonic setting affected by continental extension and rifting.

3.
The Mesoproterozoic granites were formed in an extensional rift setting that also generated widespread coeval doleritic dykes in the NCC.These igneous rocks are also coeval with the 1.3-1.2Ga extensional events that occurred worldwide.Therefore, the extensional setting at the northern margin of the NCC reflects a response to the late break-up stage of the Columbia supercontinent.
Appendix A

Figure 2 .
Figure 2. Simplified geologic map of the Huade area, Inner Mongolia.

Figure 2 .
Figure 2. Simplified geologic map of the Huade area, Inner Mongolia.Figure 2. Simplified geologic map of the Huade area, Inner Mongolia.

Figure 2 .
Figure 2. Simplified geologic map of the Huade area, Inner Mongolia.Figure 2. Simplified geologic map of the Huade area, Inner Mongolia.

Figure 4 .
Figure 4. Cathode luminescence images of representative zircons from the Mesoproterozoic granites in the study area.Figure 4. Cathode luminescence images of representative zircons from the Mesoproterozoic granites in the study area.

Figure 4 .
Figure 4. Cathode luminescence images of representative zircons from the Mesoproterozoic granites in the study area.Figure 4. Cathode luminescence images of representative zircons from the Mesoproterozoic granites in the study area.

Figure 5 .
Figure 5. LA-ICP-MS zircon U-Pb concordia diagrams of the Mesoproterozoic granite samples in the study area.

Figure 5 .
Figure 5. LA-ICP-MS zircon U-Pb concordia diagrams of the Mesoproterozoic granite samples in the study area.

Figure 8 .
Figure 8. Correlation between Hf isotopic compositions and crystallization ages of porphyritic biotite monzogranite.

Figure 8 . 21 Figure 9 Figure 9 .Figure 9 .
Figure 8. Correlation between Hf isotopic compositions and crystallization ages of porphyritic biotite monzogranite.6. Discussion 6.1.Granite Petrogenesis The primary minerals in the Mesoproterozoic granites are alkali feldspar, plagioclase, quartz, and biotite, with K-feldspar megacrysts present in most samples.Samples are enriched in Ga (19.50-28.46ppm), with 1000 Ga/Al values of 2.64-3.10.Most samples are plotted in the A-type granite field on 10,000 Ga/Al-Ce, 10,000 Ga/Al-Zr, and 10,000 Ga/Al-K 2 O/MgO diagrams (Figure 9a-c; [37]).Similarly, on a Zr + Nb + Ce + Y-TFeO/MgO diagram (Figure 9d), all samples are plotted in the A-type granite field.In addition, the absence of inherited zircons in the Mesoproterozoic granites, which are typically present in S-type granites, indicates the source region of the Mesoproterozoic granites underwent high-temperature melting.This characteristic is typical of A-type granites.Most samples are plotted in the A2-type granite fields in Nb-Y-Ce and Nb-Y-3Ga ternary diagrams (Figure 9e-f).Minerals 2023, 13, x FOR PEER REVIEW 11 of 21

Table A1 .
LA-ICP-MS zircon U-Pb data of the volcanic rocks from the Mesoproterozoic granite-like zircon.

Table A3 .
Zircon in situ Hf isotope analysis results of medium-grained porphyritic biotite monzogranite.