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The Early Cretaceous Guojialing-type granodiorites in northwestern Jiaodong terrane carry significant records for strong mantle–crust interaction during the destruction of North China Craton (NCC); however, the definite petrogenetic mechanism and detailed magmatic process remain an enigma. Titanite in igneous rocks can serve as an effective petrogenetic indicator. Here, we present integrated geochronological and geochemical studies on titanites from Guojialing-type granodiorites and their dioritic enclaves to constrain their petrogenesis. Titanites from granodiorites (G-type) and plagioclase-rich dioritic enclaves (E-type-I) present an identical U–Pb age (~ 130 Ma) and an indistinguishable wide range of Zr and total REEs contents, and Th/U ratios. However, these two types of titanites exhibit distinct micro-scale textures and geochemical compositions. G-type titanites are characterized by oscillatory zonings with two Light BSE zones (LBZ) and two or three dark BSE zones, whereas E-type-I titanites are marked by core–mantle–rim zonings. Drastic increase of LREEs, Zr, Hf, and Fe and decrease of Nb, Ta, Al, and F contents are observed in LBZ of G-type titanites, whereas remarkable reduction of LREEs, Zr, and Hf and elevation of F contents are observed from the cores to the mantles of E-type-I titanites. Based on Zr-in-titanite thermometry, G-type titanites are interpreted to have experienced twice notable temperature increase, while E-type-I titanites are inferred to have undergone a rapid cooling process. Furthermore, we suggest that the drastic chemical changes in G-type and E-type-I titanites are ascribed to early-stage magma mixing between a colder felsic magma and a Fe-, REE-rich hotter dioritic magma. Compared to G-type and E-type-I titanites, titanites from plagioclase-poor dioritic enclaves (E-type-II) are characterized by their occurrence in interstitial space and present a relatively younger U–Pb age (~ 128 Ma) and much narrower and lower range of Zr, total REEs contents, and Th/U ratios, but reveal high F contents (0.35–0.76 wt.%) and extreme high Nb/Ta ratios (up to 65.6). Such titanites are perceived to record late-stage mingling, during which F-rich and REE-poor hybrid granodioritic magma squeezed into the incompletely consolidated dioritic enclaves with accompanying fluid–rock interaction. Combining our results with previous isotopic studies, a new genetic model for Guojialing-type granodiorites is envisaged, which involves multi-stage magma mixing between Archean lower crust-derived felsic magma and mafic lower crust-derived dioritic magma, triggered by mantle-derived mafic magma underplating during the course of asthenospheric upwelling in Early Cretaceous. Such process further implicates the reactivation of Jiaodong lower crust during the destruction of NCC. [ABSTRACT FROM AUTHOR]

Abstract: The late Mesozoic granitoids widely distributed in the northwestern Jiaodong Terrane are important markers of cratonic destruction and lithospheric thinning of the eastern North China Craton (NCC). Here we investigate the Late Jurassic Linglong and Luanjiahe granites and report zircon U–Pb emplacement ages of 157–159Ma. These rocks also contain abundant late Archean, Paleoproterozoic, Neoproterozoic, early Paleozoic and Triassic inherited zircons, suggesting the involvement of continental crustal materials from both the NCC and Yangtze Craton in magma tectonics. The rocks investigated in this study show high Na2O+K2O and low MgO and are peraluminous, with enrichment in LREEs and LILEs (Rb, Ba, U, and Sr) and depletion in HFSEs (Nb, Ta, P, and Ti). They also display low εHf(t) values and high Sr/Y ratios, comparable to adakitic rocks, suggesting that the Linglong and Luanjiahe granitoids formed under relatively high pressure conditions and were likely derived from the partial melting of the thickened lower crust of the NCC. The Guojialing granodiorites were emplaced in the early Cretaceous (129Ma), and also contain abundant late Archean and Paleoproterozoic inherited zircons. The rocks possess high CaO, TFe2O3 and MgO, and are metaluminous, with enrichment in LREEs and LILEs and depletion in HFSEs. They are also characterized by high Sr/Y ratios, and have higher εNd(t) and εHf(t) values than the Late Jurassic granitoids, suggesting the involvement of mantle components in the magmatic source. We correlate the magma tectonics with the processes accompanying the subduction of the Pacific Plate beneath the NCC and the associated asthenospheric upwelling. [Copyright &y& Elsevier]

Abstract: The North China Craton (NCC) has figured prominently in recent reconstructions on the Paleoproterozoic supercontinent Columbia. Here we report abundant carbonatitic and mafic dykes from around the giant Bayan Obo rare earth element deposit in the northern margin of the NCC, and present geochemical and isotope geochronological data. The carbonatite (1354±59Ma) and mafic dykes (1227±60Ma) have comparable whole rock Sm–Nd isochron ages and Sr–Nd isotope compositions, suggesting a common source characteristic. Their geochemical characters including major and trace elements as well as REE patterns also attest to a common tectonic environment of magma generation and emplacement within a continental margin rift. The extensive mafic and carbonatitic magmatisms are associated with an extensional event that resulted in the formation of the Bayan Obo rift in the northern margin of the NCC, which we correlate with the final stages of fragmentation of the Columbia supercontinent amalgam. [ABSTRACT FROM AUTHOR]

Paleoproterozoic granites, divided into alkali-feldspar granite and albite granite, were newly discovered in the Changyi area of the Jiao-Liao-Ji Belt from the Eastern Block of the North China Craton. LA–ICP-MS zircon U–Pb dating shows that the alkali-feldspar granite was emplaced at 2193 Ma, whereas the albite granite intruded at 2171 Ma. These granites have high SiO 2 , Na 2 O + K 2 O, Zr, Nb, Ga, Y and HREE contents and show remarkably low CaO, Eu, Ba and Sr concentrations, strongly suggesting their A-type affinities. Zircon saturation thermometry and Al T -in-biotite geobarometer indicate that the alkali-feldspar granite crystallized at temperatures of 823–856 °C (averaging at 839 °C) and pressures of 1.54–2.73 kbar (averaging at 2.05 kbar) while the albite granite was cooled at the temperatures of 851–853 °C and the pressures of 2.34–2.64 kbar (averaging at 2.45 kbar). Combined with such high temperatures and low pressures, the crustal-like Nd–Hf isotopic compositions ( ɛ Nd ( t ) = −5.3 to −4.4, ɛ Hf ( t ) = −7.0 to −3.8.) support their derivation from the shallow melting of Archean crustal rocks under high heat flow. However, the contrasted K 2 O and Na 2 O compositions between the alkali-feldspar granite (K 2 O = 4.76–5.14 wt.%, Na 2 O = 4.76–5.14 wt.%) and the albite granite (K 2 O = 0.29–0.44 wt.%, Na 2 O = 6.15–6.56 wt.%) imply that they may have been derived from distinct source rocks or have undergone different magmatic processes. Genetic modeling suggests that the alkali-feldspar granite was originated from melting of granodioritic rocks. The albite granite, however, was most likely derived from the reworking of plagioclase-rich layers after the extraction of A-type melts. Coupled with other studies on sedimentary and volcanic successions in the Jiao-Liao-Ji Belt, the unusual association of the A-type alkali-feldspar granite and albite granite indicates that the southern segment of the Jiao-Liao-Ji Belt experienced continental rifting during 2.1–2.2 Ga. [ABSTRACT FROM AUTHOR]

Abstract Late Mesozoic granitoids are widely distributed in the Jiaobei Terrane, southeastern North China Craton (NCC) and crucial to understanding the processes and mechanisms of the lithospheric thinning. Here we present petro-geochemical, zircon U Pb, Lu Hf and O isotopic constrains on three stages of granitoids, building an integrated model of lithospheric thinning from beginning through peak to waning stages. The early stage Linglong granite (166–158 Ma) is geochemically comparable to adakitic rocks with negative ɛ Nd (t) (−21.3 to −19.2), zircon ɛ Hf (t) (−26.8 to −18.7), and high zircon δ18O (6.7–8.3‰). It was originated from the subduction-thickened lower crust of the eastern NCC, with minor contribution from the subducted Yangtze Block, in an extensional setting, representing the beginning of lithospheric thinning. The middle stage Guojialing granodiorite (130–128 Ma), characterized by higher Sr/Y, Ba (898–5075 ppm), Sr (657–2256 ppm), ɛ Nd (t) (−19.1 to −11.5), zircon ɛ Hf (t) (−19.0 to −11.6) and δ18O (7.5–8.7‰) than the Linglong granite, addressing a fluid-metasomatized lithospheric mantle and extensive crust-mantle interaction in the Paleoproterozoic crustal source, is coeval with peak lithospheric thinning due to roll-back of the subducted Pacific plate. The late stage Aishan complex (118–115 Ma), which is composed of granodiorite, syenogranite, porphyritic quartz syenogranite, alkali granite and monzodiorite, exhibits slightly lower ɛ Nd (t) (−17.9 to −16.2), zircon ɛ Hf (t) (−21.4 to −15.3) and δ18O (6.6–7.9‰) than the Guojialing granodiorite. It was derived from the melting of Neoarchean- Paleoproterozoic crust with limited crust-mantle interaction and experienced crustal assimilation and fractional crystallization, indicating an extended process associated with the waning stage of lithospheric thinning. We document the magmatic responses to the lithospheric thinning at different stages which account for the genesis and evolution of the continental adakitic rocks and decratonization of the NCC. Graphical Abstract Unlabelled Image Highlights • Three Mesozoic granites mark the beginning, peak and waning lithospheric thinning. • Extensive crust-mantle interaction occurred during the peak lithospheric thinning. • Crustal assimilation and fractional crystallization occurred in Aishan magma. • High Ba Sr contents of Guojialing granite are due to metasomatic mantle components. [ABSTRACT FROM AUTHOR]

The Hujiayu Cu deposit, located in the Zhongtiao Mountains district of southern North China Craton, is hosted by graphite schist and dolomitic marble with disseminated to veinlet (stage I) and thick vein (stage II) mineralization. Stage I mineralization, characterized by stratabound, disseminated pyrite and chalcopyrite within the graphite schist host rock, formed at the syn-metamorphic stage. Graphite geothermometry showed that the host rock was subjected to an upper-greenschist to lower amphibolite metamorphism at a temperature range of 486 to 596 °C, averaging of 546 ± 35 °C (1 σ, n = 19). Stage II mineralization, consisting of brecciated dolomitic thick veins cemented by quartz-sulfide assemblages, was a product of metamorphic hydrothermal activity. This thick vein was subdivided into an early hydrothermal dolomitic alteration composing of dolomitic breccia with some cobaltiferous pyrite (stage IIa) and a late siliceous-copper mineralization consisting of quartz-sulfide assemblages (stage IIb). A clausthalite–siegenite–sphalerite–chalcopyrite mineral assemblage was observed in stage IIb, constraining the sulfur fugacity and selenium fugacity within − 18.7 to − 11.7 and − 21.7 to − 14.7, respectively. It was inferred stage IIb was marked by a drop in sulfur fugacity and a substantial increase in selenium fugacity after the major chalcopyrite precipitation. Calculations based on the compositions of cobaliterous pyrite and sphalerite reveal that the mineral assemblage at stage IIa formed at an approximately temperature range of 400 to 300 °C, whereas the minerals in stage IIb occurred at temperature of 256 ± 9 °C (1 σ, n = 7). Sulfides from stage I have δ 34 S value ranging from 10.1 to 22.2‰ with an average value of 16.9 ± 3.4‰ (1 σ, n = 27), supporting the model that sulfides precipitated through thermochemical reduction of sulfate at sedimentary stage followed by metamorphic homogenization of δ 34 S isotopic signatures. Sulfides from the stage II have δ 34 S values in highly variable ranging from 3.4 to 19.2‰, indicating a rather complex source. Four chalcopyrite samples yielded a weighted model age of 1952 ± 39 Ma (1 σ, MSWD = 1.5), suggesting that the copper mineralization formed synchronously with regional metamorphism (1970–1850 Ma) and hence a Paleoproterozoic metamorphogenic copper mineralization is implicated. Therefore, we envisaged disseminated-veinlet mineralization formed during a metamorphic peak and the major hydrothermal copper mineralization occurred during the retrograde cooling. [ABSTRACT FROM AUTHOR]

The Tongshi intrusive complex from the southeastern margin of the North China Craton is composed of syenite and monzonite, and was emplaced at ca. 180 Ma. Apatite from the syenite and monzonite were analyzed to better understand the petrogenesis of the complex and its mineralization potential. The cathodoluminescence images of some apatites from the monzonite exhibit core–rim texture, whereas the apatites from the syenite display uniform inner texture. The core and rim domains of the apatites exhibit distinct Sr isotopes and major–trace element compositions, whereas only little variation is displayed by the oxygen isotopes. The core portions of the apatites were inferred to be inherited from the protolith of the monzonite during remelting process. The calculated δ 18 O values of the syenite range from 3.5‰ to 4.1‰ with an average of 3.8‰ (SE = 0.21), which is significantly lower than that of the monzonite sample (with a range of 6.4–6.9‰, and mean at 6.7‰). In conjunction with the heterogeneity of Nd isotopic compositions (with normalized 143 Nd/ 144 Nd ratios varying from 0.51151 to 0.51236, and ε Nd ( t = 180 Ma) values from −20.3 to −4.8) of the apatites from the syenite, it is proposed that the syenite melts may have been contaminated by crustal components which were earlier hydrothermally altered at high temperature. Based on element diffusion theory, we calculate the temperature of this crustal contamination to be higher than 637 °C, the closure temperature of Sm–Nd isotopic diffusion in apatite, and estimate that the duration of this process is probably shorter than 0.13 Ma. The oxygen fugacity of the syenite and monzonite calculated by apatite Mn content indicate that high oxidization state of the syenite magma can enhance the metallic mineralization potential. In contrast, the lower oxygen fugacity of the monzonite melt was unfavorable for metal enrichment, thus leading to insignificant mineralization. Our study recommends more focus for gold exploration in the rocks with syenitic affinities in this region. [ABSTRACT FROM AUTHOR]

The Guilaizhuang deposit is the largest gold producer in the southwestern Shandong Province with a unique Au–Te mineralization feature different from the other gold deposits in the adjacent Jiaodong Peninsula. The Tongshi alkaline intrusive complex, which is composed of syenites and monzonites with a crystallization age of ~ 180 Ma, is the main magmatic unit in this area, and considered to represent post-collisional magmatism. The syenite intruded into the sedimentary carbonate sequence in the Guilaizhuang district, cryptoexploded and was altered by fluorine-rich fluid. The intensely mineralized cryptoexplosive breccias along the EW-trending fault are extensively cemented by fluorite and calcite minerals. The intrusive age of the syenite should mark the lower limit of the gold mineralization age, whereas the formation age of the fluorite and calcite would represent the upper limit. In this study, we analyzed zircons from the altered syenite in the open-pit, and the results show U–Pb ages of 179–180 Ma consistent with those of the Tongshi intrusive complex. We also present a Sm–Nd isochron age from the fluorite–calcite mineral pair that shows 181 Ma. Based on those results, we infer the timing of gold mineralization to be approximately 180 Ma, coeval with the intrusion of the Tongshi complex. A correlation with the regional tectonic milieu shows that the Guilaizhuang gold deposit was located in a post-collision setting at this time, following the amalgamation between the North China Craton and the Yangtze Craton. Thus, the Guilaizhuang deposit should mark an important alkaline rock-related gold-forming event within the eastern margin of the North China Craton in a post-collisional setting associated with the collision of the North China Craton and Yangtze Craton during late Triassic to Early Jurassic, and is obviously different from the Early Cretaceous intensive gold mineralization in the adjacent Jiaodong Peninsula. [ABSTRACT FROM AUTHOR]

Silicate melt inclusions (SMIs) in magmatic minerals provide key information on the chemical and mineralogical evolution of source magmas. The widespread Cretaceous mafic dikes in the Jiaojia region of the eastern North China Craton contain abundant SMIs within clinopyroxene phenocrysts. The daughter minerals in these SMIs include amphibole, plagioclase, pyrite and ilmenite, together with CO 2 + CH 4 and CH 4 as the major volatile phase. The total homogenization temperatures of the SMIs range between 1280 and 1300 °C. The host clinopyroxene phenocrysts in these dolerite dikes are dominantly augite with minor diopside. From LA-ICPMS analyses of the SMIs, we identify two compositional groups: (1) low-MgO (6.0–7.6 wt.%) SMIs and (2) high-MgO (11.2–13.9 wt.%) SMIs. The Low-MgO group exhibits higher concentrations of TiO 2 , Al 2 O 3 , Na 2 O, P 2 O 5 and lower CaO and CaO/Al 2 O 3 ratio as compared to the high-MgO SMIs. The trace element patterns of the two types of SMIs are similar to those of the host mafic dikes. However, the low-MgO SMIs and host mafic dikes are clearly more enriched in all the trace elements as compared to the high-MgO type, especially with regard to the highly incompatible elements. The estimated capture temperatures and pressures are 1351–1400 °C and 1.6–2.1 GPa for the high-MgO SMIs and 1177–1215 °C and 0.6–1.1GPa for the low-MgO type. The high-MgO and low-MgO SMIs were trapped at depths of ∼51–68 km and ∼20–35 km, respectively. Computations show that the parental melt is mafic with SiO 2 content 49.6 wt% and Mg # 80.0 with relatively low total alkali contents (1.35 wt% Na 2 O + K 2 O) and high CaO (15.2 wt%). Exploratory runs with the program MELTS and pMELTS show that the low-MgO and high-MgO SMIs were derived from the same parental melt through different degrees of crystallization. Clinopyroxene and a small amount of olivine were the fractionating phases during the evolution from parental melts to high MgO melts, while the low MgO melts experienced significant fractional crystallization of olivine and clinopyroxene. We postulate the newly accreted lithospheric clinopyroxenite as the major source for the Jiaojia dolerite dikes, with melting of the source at a depth of ∼68–80 km. [ABSTRACT FROM AUTHOR]

Abstract: The Changyi banded iron formation (BIF) in the eastern North China Craton (NCC) occurs within the Paleoproterozoic Fenzishan Group. The BIF shows alternating quartz-rich light and magnetite-rich dark bands with magnetite (15–65vol.%), quartz (25–65vol.%) and amphibole (15–30vol.%) constituting the major minerals. Minor garnet, epidote, chlorite, calcite, biotite and pyrite occur locally. The BIF bands are interlayered with amphibolite, hornblende gneiss, biotite quartz schist, garnet biotite schist, biotite gneiss and leptynite, and are intruded by granites. LA-ICP-MS U–Pb dating on zircons separated from the BIF bands and the wallrocks constrains the depositional age as 2240–2193Ma and metamorphic age as ~1864Ma. The dominant composition of SiO2 +Fe2O3 T (average value of 92.3wt.%) of the BIF bands suggests their formation mainly through chemical precipitation. However, the widely varying contents of major elements such as Al2O3 (0.58–6.99wt.%), MgO (1.00–3.86wt.%), CaO (0.22–4.19wt.%) and trace elements such as Rb (2.06–40.4ppm), Sr (9.36–42.5ppm), Zr (0.91–23.6ppm), Hf (0.04–0.75ppm), Cr (89.1–341ppm), Co (2.94–30.4ppm), and Ni (1.43–52.0ppm) clearly indicate the incorporation of clastics, especially continental felsic clastics, as also confirmed by the presence of ancient detrital zircons in the BIF bands. When normalized against Post Archean Average Shale (PAAS), the seawater-like signatures of REE distribution patterns, such as LREE depletion, positive La and Y anomalies, and superchondritic Y/Ho ratios (average value of 36.3), support the deposition in seawater. Strong positive Eu anomalies (Eu/Eu*PAAS =1.14–2.86) also suggest the participation of hydrothermal fluids. In addition, the sympathetic correlation between Cr, Co and Ni as well as the Co+Ni+Cu vs. ∑REE and the Al2O3 vs. SiO2 relations further indicates that the iron and silica mainly originated from hydrothermal fluids. Combined with regional geological investigation and protolith restoration of the wallrocks, a continental rift environment is suggested for the Changyi BIF deposition. The appearance of negative CePAAS anomalies might suggest the influence of the Great Oxidation Event at the time of deposition. The Changyi BIF witnessed the major Paleoproterozoic rifting–collision events in the NCC and their unique distribution in the NCC contrasts with other examples elsewhere in the world. [Copyright &y& Elsevier]

Abstract: The Laiwu quartz monzonite in the Luxi Block of eastern North China Craton (NCC) is characterized by the presence of abundant plagioclase amphibolite and gabbro–diorite enclaves. Here we present LA-ICPMS zircon U–Pb ages which show that the host quartz monzonite was emplaced at 129.8±1.0Ma, whereas the protolith of the plagioclase amphibolite enclaves formed during early Paleoproterozoic. The gabbro–diorite enclaves were produced simultaneously with or slightly earlier than the formation of the host quartz monzonite. Combined with the Archean and Paleoproterozoic zircons as well as the low εNd(0) values (−18.4 to −18.0) in the plagioclase amphibolite enclaves, the equilibrium temperature and pressure conditions (645–670°C and 4.8–6.5 Kb) suggest that the plagioclase amphibolite enclaves are fragments of the middle crust. The gabbro–diorite enclaves mainly originated from an enriched lithospheric mantle metasomatized by melts/fluids derived from the continental crust, as indicated by their low SiO2 (54.4–54.7wt.%) and high MgO (10.9–11.1wt.%) contents as well as the negative εNd(t) values (−13.5 to −10.7) and enrichment of LILEs (e.g., Ba and Sr) and depletion of HFSEs (e.g., Nb, Ta, P and Ti). Compared with the ancient crustal rocks and the mafic plutons considered to have been derived from lithospheric mantle in the Luxi Block, the moderate εNd(t) (−15.7 to −15.1) and εHf(t) (−20.7 to −13.0) values of the quartz monzonite in our study suggest that both mantle- and crust-derived melts were involved in the magma generation. Thus we propose a model involving magma mixing between mantle- and crust-derived melts for the formation of the quartz monzonite. Since significant crust–mantle interaction is recorded not only in the quartz monzonite and its enclaves in the Luxi Block but also in the other granitoids widespread in the NCC, it is considered that large-scale crust–mantle interaction and magmatic underplating were associated with the Mesozoic lithospheric mantle thinning and crustal reactivation in the eastern NCC. [Copyright &y& Elsevier]

Abstract: In situ zircon U–Pb ages and Hf isotopic data, major and trace elements, and Sr–Nd–Pb isotopic compositions are reported for the Longbaoshan alkaline intrusive complex in the western Shandong Province (Luxi Block), southeastern North China Craton. The Longbaoshan complex, which consists of quartz syenite, aegirine–augite syenite, hornblende syenite, monzonite, and syenodiorite, was emplaced at 129.4–131.7Ma. The complex is characterized by high concentrations of SiO2, K2O+Na2O, Al2O3, LILEs (e.g., Sr and Ba), and LREEs, and low concentrations of CaO, Fe2O3, MgO, and HFSEs (e.g., Nb, Ta, P and Ti). The Sr, Nd, Pb, and Hf isotopic values of this complex are similar to the nearby mafic rocks, which were derived from EM2-type lithospheric mantle, indicating that the Longbaoshan complex was mainly derived from partial melting of the EM2 source. Combined with geochemical and isotopic features, the high Nb/Ta ratios (average 19.2) of the Longbaoshan complex suggest that the EM2 source was induced by modification of crust-derived melts, which were in equilibrium with rutile-bearing eclogite. This was attributed to the subduction of the Yangtze continental crust. The presence of inherited zircons (2.51–2.64Ga) with positive εHf(t) values (0.2–6.2) suggest that the ancient crust of the North China Craton was also involved in the formation of the Longbaoshan complex. Magma mixing modelling shows that those 10–35% crustal materials were assimilated in the complex. This complex may have experienced hornblende, apatite/monazite, and titanite crystal fractionation before emplacement in the shallow crust level. Two stages of crust–mantle interaction can be identified through the formation of the Longbaoshan complex, including (1) the lithospheric mantle was metasomatized by the melts/fluids derived from the subducted crust and then transformed into an EM2 counterpart, and (2) magma derived from the EM2 source underplated the ancient crust and assimilated the crust-derived materials. We thus propose that multiple crust–mantle interactions are the essential mechanism for the destruction of the NCC. The first intensive crust–mantle interaction was aroused by crustal subduction and was responsible for the lithospheric mantle destruction, and the second major crust–mantle interaction was induced by mantle-derived magma underplating and was responsible for the crustal activation. [Copyright &y& Elsevier]