Jiamusi Massif Research Articles

Geochronology (U-Pb and Re-Os) and H[sbnd]O[sbnd]S isotopes reveal ore fluid origin and crucial role of meteoric water for Laozuoshan quartz-vein-hosted gold metallogeny in Jiamusi, NE China

The Laozuoshan auriferous sulfide-quartz veins, which are hosted in the granodiorite, monzogranite, and quartz diorite, are the only Early Cretaceous gold deposit discovered in the central Jiamusi Massif, but its origin and ore-forming processes remain unclear. Here, we integrate mineralogy, HOS isotopes, and U-Pb and Re-Os geochronology to unravel the formation of the Laozuoshan quartz-vein gold mineralization. Zircon and molybdenite from the monzogranite wallrock and gold ores yield weighted mean U-Pb and isochron Re-Os dates of 259.9 ± 2.1 Ma and 103.3 ± 2.3 Ma, respectively. Our radiometric dating suggests that the Laozuoshan quartz-vein gold mineralization was coeval with the quartz diorite (105–103 Ma) but after the monzogranite emplacement. Quartz grains from the auriferous veins of different stages yielded scattered δ18O values (5.4 to 13.0 ‰), with the δD values (fluid inclusions) ranging from –99.9 to –74.9 ‰. The δ18O values of quartz (10.9–13.3 ‰) and feldspar (9.4–11.0 ‰) from the unaltered wallrocks are similar to those (δ18Oquartz = 11.2–13.2 ‰ and δ18Ofeldspar = 10.0–10.4 ‰) from the potassic alteration halos. Meanwhile, the sericite-altered rocks have δ18O values of 12.4–12.9 ‰ (quartz) and 3.4–5.2 ‰ (sericite). Sulfides from the gold ores yielded decreasing δ34S values from 5.3 to 6.9 ‰ (early stage), through 1.0–3.5 ‰ (intermediate stage), to –4.9 to –4.4 % (late stage). The isotope data reflect a largely magmatic source for the early ore fluids, whilst the sulfur was possibly derived from the Mashan Group migmatite. The results, in combination with geologic evidence, indicate that the Laozuoshan quartz-vein gold mineralization was spatially, temporally, and genetically related to the Early Cretaceous quartz diorite, and thus can be classified as intrusion-related, magmatic-hydrothermal-vein type. In the ore-forming processes, the ascending Early Cretaceous magma may have acquired most of their sulfur and gold through assimilation of the Mashan Group migmatite. The early ore fluids derived from the quartz diorite magma may have initially focused into narrow cracks/fractures in the quartz diorite margin and then flow along the fracture system. Subsequently, meteoric water incursion led to temperature drop, boiling, oxygen fugacity increase, and chemical exchange of the resultant fluids, which facilitated gold scavenging by bismuth-rich melts and rapid precipitation as arsenopyrite-hosted electrum and gold-bismuth mineral eutectic assemblage. This study highlights the crucial role of meteoric water in formation of the magmatic-hydrothermal-vein type gold deposit.

Trace element and Nd isotope analyses of apatite in granitoids and metamorphosed granitoids from the eastern Central Asian Orogenic Belt: Implications for petrogenesis and post-magmatic alteration

We present in situ trace element and Nd isotopic data of apatites from metamorphosed and metasomatized (i.e., altered) and unaltered granitoids in the Songnen and Jiamusi massifs in the eastern Central Asian Orogenic Belt, with the aim of fingerprinting granitoid petrogenesis, including both the magmatic and post-magmatic evolution processes. Apatites from altered granitoids (AG) and unaltered granitoids (UG) are characterized by distinct textures and geochemical compositions. Apatites from AG have irregular rim overgrowths and complex internal textures, along with low contents of rare earth elements (REEs), suggesting the re-precipitation of apatite during epidote crystallization and/or leaching of REEs from apatite by metasomatic fluids. εNd(t) values of the these apatites are decoupled from zircon εHf(t) values for most samples, which can be attributed to the higher mobility of Nd as compared to Sm in certain fluids. Apatites from UG are of igneous origin based on their homogeneous or concentric zoned textures and coupled Nd-Hf isotopic compositions. Trace element variations in igneous apatite are controlled primarily by the geochemical composition of the parental melt, fractional crystallization of other REE-bearing minerals, and changes in partition coefficients. Sr contents and Eu/Eu* values of apatites from UG correlate with whole-rock Sr and SiO2 contents, highlighting the effects of plagioclase fractionation during magma evolution. Apatites from UG can be subdivided into four groups based on REE contents. Group 1 apatites have REE patterns similar to the host granitoids, but are slightly enriched in middle REEs, reflecting the influence of the parental melt composition and REE partitioning. Group 2 apatites exhibit strong light REE depletions, whereas Group 3 apatites are depleted in middle and heavy REEs, indicative of the crystallization of epidote-group minerals and hornblende before and/or during apatite crystallization, respectively. Group 4 apatites are depleted in heavy REEs, but enriched in Sr, which are features of adakites. Some unusual geochemical features of the apatites, including the REE patterns, Sr contents, Eu anomalies, and Nd isotopic compositions, indicate that inherited apatites are likely to retain the geochemical features of their parental magmas, and thus provide a record of small-scale crustal assimilation during magma evolution that is not evident from the whole-rock geochemistry.

Revisiting the Late Paleozoic–Mesozoic tectonic evolution of epicontinental eastern Central Asian Orogenic Belt on the basis of detrital zircon

The eastern Central Asian Orogenic Belt (CAOB) is a natural laboratory for studying and interpreting the evolution of accretionary collages. The CAOB contains several micro-landmasses whose tectonic evolution during the Late Paleozoic–Mesozoic is a matter of debate. Here, we revisited detrital zircon data in relevant areas and present new detrital zircon U–Pb age data from the Hulin Complex and Wandashan Accretionary Complex (consisting of the Raohe and Yuejinshan complexes) in the eastern CAOB. The youngest zircon peak age of mica-quartz schist from the Hulin Complex constrains the timing of deposition to after ∼153.5 Ma. Sandy slate and fine sandstone from the Wandashan Accretionary Complex have youngest ages of ∼135.7 and ∼254.7 Ma, respectively. These data, together with detrital zircon data in the epicontinental eastern CAOB, suggest that there was a transformation from an extensional to convergent tectonic setting in the eastern CAOB around the Late Permian–Early Triassic. The Khanka Massif may have been adjacent to the Songnen and Jiamusi massifs to the west and north respectively, during the Late Paleozoic–Mesozoic. Between the Songnen and Jiamusi massifs, the Mudanjiang Ocean initially opened in the Late Paleozoic and closed after the Late Jurassic (∼153.5 Ma) and produced the Heilongjiang Complex. The Paleo-Yuejinshan back-arc basin underwent extension in the Permian and finally closed after ∼216 Ma, forming the Yuejinshan Complex at ∼210–180 Ma. The Raohe Complex was accreted at ∼169–133 Ma and emplaced at ∼133–131 Ma. The large-scale sinistral strike-slip movement of the Dunmi Fault started later than ∼153.5 Ma and partially displaced the Heilongjiang Complex from the Mudanjiang area to the present-day Hulin Complex. The eastern CAOB was under a superimposed tectonic regime of the Paleo-Pacific Ocean and Paleo-Asian Ocean in the Late Paleozoic.

Age, petrogenesis, and tectonic setting of granitic gneiss and amphibolite from the Weizigou gold deposit, Heilongjiang Province, NE China: Constraints from geochronology and geochemistry

The Weizigou gold deposit is located in the western Jiamusi Massif, Northeast China. Gold mineralization is hosted in the amphibolite, which intruded the granitic gneiss. Although the deposit shows similarities to iron-oxide–copper–gold deposits, the detailed ore-forming process remains uncertain. To determine the formation age, petrogenesis, and tectonic setting of the granitic gneiss and amphibolite, LA–ICP–MS zircon, titanite, and monazite UPb dating, whole-rock major- and trace-element analyses, and LA–ICP–MS in situ zircon Hf isotope analyses were conducted on samples from these rocks. The granitic gneiss yielded two age populations of 951–882 Ma, and ca. 500 Ma, with a monazite UPb concordia age of 501.5 ± 5.1 Ma. The amphibolite yielded a crystallization age of 292 Ma, consistent with the results for magmatic titanite UPb dating, and a metamorphic age of 272–258 Ma. The granitic gneiss contains typical aluminum-rich minerals, such as garnet and muscovite, mean SiO2 = 73.31 wt%, and molar ratio Al2O3/(CaO + K2O + Na2O) values of 1.02–1.07, indicating an S-type granite protolith. The amphibolite belongs to the tholeiitic basalt series and has low SiO2 and high MnO contents. These results, together with εHf(t) values and two-stage model ages ranging from −9.5 to 2.3 and − 0.3 to 5.7, and from 2010 to 1659 Ma and from 1331 to 947 Ma, respectively, allow us to infer that the parental magmas of the granitic gneiss and amphibolite were derived from the partial melting of Paleoproterozoic lower crust and the partial melting of metasomatized depleted mantle, respectively. The granitic gneiss is characterized by positive Th and Hf anomalies, and negative Nb, Ta, Sr and Ti anomalies, whereas the amphibolite is enriched in K, Rb, and depleted in Ba, Nb, Ti, and Zr. These geochemical features suggest that the S-type granite was formed in an active continental margin during the Neoproterozoic and underwent granulite-facies metamorphism during the early Paleozoic. The protolith of the amphibolite was gabbro that formed in an extensional setting (e.g., a backarc basin) associated with westward subduction of the Paleo-Pacific oceanic plate beneath the eastern Jiamusi Massif during the early Permian. The gold mineralization can most likely be attributed to contact metasomatic metamorphism of gabbro during the middle–late Permian.

The Early Permian assembly of the Jiamusi Massif and Khanka Massif: Evidence from sediment sources

The Jiamusi‐Khanka Massif is an important tectonic unit of the Central Asian Orogenic Belt in North‐east China. Its Late Palaeozoic tectonic properties and the timing of assembly have restricted the understanding of the tectonic evolution process at the eastern segment of the Central Asian Orogenic Belt for a long time. Based on the study of clastic rock petrology and zircon U–Pb chronology of the Early Permian Erlongshan Formation in Mishan, it is clear that the zircon age of the Early Permian Erlongshan Formation in Mishan is mainly Late Palaeozoic, with a major age peak at 300 ± 3 Ma and secondary age peaks at 356 ± 7 Ma and 475 ± 10 Ma. The provenance mainly comes from the magmatic arc source area, and Early Palaeozoic (500–420 Ma) detrital zircons mainly come from the south‐east margin of Jiamusi Massif, Late Palaeozoic (400–270 Ma) detrital zircons mainly come from the eastern margin of Jiamusi Massif and the northern margin of Khanka Massif. Among them, detrital zircons of a special age group 330–310 Ma come from the north of Khanka Massif, while 490–470 Ma detrital zircons which are common in the Early‐Middle Permian strata of Khanka Massif come from Jiamusi Massif. Combined with the evidence of petrology and palaeontology, this paper believes that the Early Permian Jiamusi Massif and Khanka Massif should be a unified Massif, that is, Jiamusi‐Khanka Massif.

Metamorphism of the Yilan amphibolites from the Heilongjiang Complex and deformation of the granodioritic mylonites from the Jiamusi Massif, Northeastern China

The Heilongjiang Complex records the evolution history of the Mudanjiang Ocean, which is of great significance to constrain the amalgamation process of the Jiamusi and Songnen‐Zhangguangcai Range massifs. We carried out petrological, chronological, geochemical, mineral chemical and electron backscatter diffraction (EBSD) fabric analyses on the Heilongjiang Complex in the Yilan area. The latest zircon U–Pb dating results show that the protolith ages of the amphibolite are 261.3 ± 3.0 Ma and 261.8 ± 3.3 Ma, while that of the granodioritic mylonite is 207.8 ± 2.2 Ma. The amphibolites and granodioritic mylonite are enriched in large‐ion lithophile elements (e.g., Rb, Ba, and Sr) and light rare earth elements, with depletion in high‐field‐ strength elements (e.g., Nb, Ta, Zr, and Hf), indicating that the formation of the protoliths of the amphibolites and granodioritic mylonite is related to the subduction of the Mudanjiang oceanic plate under the Songnen‐Zhangguangcai Range Massif. The amphibolites and granodioritic mylonite both experienced two periods of metamorphic and deformation events. The metamorphic degree of the early period of metamorphism is low amphibolite facies, which records a clockwise P–T path from early increased temperature and pressure to a late isothermal depressurization. The P–T path reveals that this period of metamorphism is associated with the collision between two massifs. The later period of metamorphism reaches low greenschist facies, accompanied by deformation, which may be related to the rapid exhumation of the Heilongjiang Complex. This study provides a new perspective for exploring the collision and collage process of the Jiamusi and Songnen‐Zhangguangcai Range massifs.

Detrital zircon U-Pb ages of the Cretaceous strata in the southern Songliao Basin, NE China: Constraints on basin-and-range evolution

The basin-and-range evolution of Northeast China could provide a comprehensive understanding of the subduction of the Paleo-Pacific Plate. The Songliao Basin preserved the essential and complete records of the Cretaceous tectonic evolution. The systematic detrital zircon UPb geochronological study was conducted on the Cretaceous sequences in the southern Songliao Basin, including Yingcheng Formation, Denglouku Formation, Quantou Formation, Qingshankou Formation, Yaojia Formation, Nenjiang Formation from bottom to up, providing new insights of provenances and tectonic evolution of the basin-range system. The Aptian and Albian sequences with the dominant age populations at ca. 133–125 Ma were derived from the Great Xing'an Range (GXAR). The Cenomanian and Early Turonian sequences with the distinct age populations at ca. 243–227 Ma received the source from the southernmost part of the Zhangguangcai Range (ZGCR). The Late Turonian to Campanian sequences experienced the gradual provenance transition to the GXAR. The main interim period with the dominant peaks at ca.1.8 and 2.5 Ga, and subdominant peaks at ca. 277 Ma, reveals the provenances from the southern margin, including the Inner Mongolia Paleo-Uplift (IMPU) and northern North China craton (NNCC) during the Late Turonian to Early Santonian. Since then, the provenance was skewed towards the GXAR manifesting the distinct age populations at ca. 139 Ma. The multi-provenance transitions reveal two orogeneses of the GXAR and ZGCR with the difference of 9 Ma. The gradual uplift from north to south in the Jiamusi Massif and the ZGCR at ca. 120–90 Ma was related to magmatic activity under the transition from the low angle subduction to slab rollback of the Pacific-Plate. The integral uplift of the GXAR at ca. 90–83.8 Ma was related to the transient compression due to the changes in direction and convergence rate of the Paleo-Pacific Plate. The compression-induced uplift was more intense than magmatism-induced uplift. Our findings can contribute to a better understanding of the basin-and-range evolution of Northeast China and the response to the subduction of the Paleo-Pacific Plate.

Geochronology and Sr-Nd-Pb-Hf isotopic geochemistry of middle-late Permian granitic and volcanic rocks within the eastern margin of the Khanka Massif: petrogenesis and implications for the tectonic nature

ABSTRACT The Khanka Massif forms the easternmost part of the Central Asian Orogenic Belt (CAOB) and represents an ideal location for examination of the timing and processes involved in the transition from the Palaeo-Asian to Palaeo-Pacific Ocean tectonic systems. However, it is obstructed because the late Palaeozoic tectonic attributes of the eastern margin of this massif remain unclear. In this paper, we provide zircon U-Pb ages and Hf isotopic, as well as the whole-rock Sr-Nd-Pb-Hf isotopic data for Permian granitic and volcanic rocks within the eastern margin of the Khanka Massif, with the aim of exploring the petrogenesis and their geodynamics significance. These data suggest that the Permian magmatism within the eastern margin of the Khanka Massif, composed of monzogranites and rhyolites, can be split into two stages; i.e. middle (ca. 264 to ca. 263 Ma) and late (ca. 252 Ma) Permian. The highly fractionated middle Permian monzogranites are formed in an N-S extensional setting and represent the magmatic response to the amalgamation of the Khanka and Jiamusi massifs. Middle-late Permian rhyolites with decoupled Nd-Hf isotopic compositions were derived from partial melting of metasedimentary crustal rocks. Their moderate-high zircon saturation temperatures (796–817°C) are thought to represent the involvement of ridge subduction of the Palaeo-Asian Ocean beneath the western margin of the Khanka Massif. Our findings further reinforce the existence of the ridge subduction of the Palaeo-Asian Ocean at the western margin of Khanka Massif in the Permian, while excluding the possibility of Permian Palaeo-Pacific oceanic plate subduction occurred beneath the eastern margin of the Khanka Massif in the Permian.

Discovery of granulite‐facies metamorphic rocks in the Yilan area, Heilongjiang Province, China: Geochronology, geochemistry, metamorphic characteristics, and geological implications

The Mashan Complex of the Jiamusi Massif was traditionally considered as the oldest stratigraphic sequence in eastern NE China. However, the metamorphic degree of the Mashan Complex is different in different areas, which can be divided into Jixi–Mishan–Hulin granulite facies belt and Luobei–Huanan–Mudanjiang amphibolite facies belt. Here, we investigated the Mashan Complex in the Yilan area and present lots of new petrological, mineral chemical, geochemical, and U–Pb geochronological data, in addition to phase equilibria modelling, to constrain the timing of metamorphism, P–T conditions, and the P–T path of the Mashan Complex, and furthermore to deduce the crustal evolution of the Jiamusi Massif. The protoliths of the Mashan Complex in the Yilan area are greywackes and felsic sandstones, whose provenance is dominantly felsic rocks formed from a continental island arc. Petrographic observations, traditional thermobarometry, and quantitative phase equilibria modelling of the studied samples reveal P–T conditions from M2 to M3 of ~7.2 kbar/760–800°C and 4.5–5.0 kbar/585–610°C, respectively, which together define a clockwise P–T path involving decompressional cooling (M3) that followed the peak granulite‐facies metamorphism (M2). It reveals essential information related to the collision orogeny and post‐collision process. Zircon U–Pb dating of two felsic rocks yielded the peak of the granulite‐facies metamorphism in the Yilan area of the Jiamusi Massif that might have occurred at ~500 Ma. The overall deposition of the metamorphic rocks was later than ~760 Ma and that most of the detrital materials came from late Mesoproterozoic and early Neoproterozoic source rocks.

ХАНКАЙСКИЙ МАССИВ: ГЕТЕРОГЕННОСТЬ ФУНДАМЕНТА И РЕГИОНАЛЬНЫЕ КОРРЕЛЯЦИИ

The results of geochronology studies on metagranitoids (U-Pb SIMS) and ophiolites (Sm-Nb) from the Khanka massif are considered. New and published data define the Early Neoproterozoic Matveevka-Nakhimov terrane with early suprasubduction magmatism of 935 and 915 Ma, intraplate and Pacific-type transform margin magmatism of 850-880 and 757 Ma, and the Late Neoproterozoic-Early Cambrian Dvoryan and Tafuin terranes with suprasubduction magmatism of 543, 520, 517 and 513 Ma. Between these two parts of the massif there is a suture (Voznesenka and Spassk terranes) formed by Ediacaran-Cambrian shelf deposits and a Cambrian accretionary prism with ophiolites older than 514 Ma. The greater part of the Khanka massif formed late in the Cambrian with the Kordonka island arc terrane accreted at the end of the Silurian. The Sergeevka terrane of the Ordovician island arc joined it through Early Cretaceous strike-slip movements. Heterogeneous structures of the main part of the Khanka massif can be traced to the north by the analogous stages of magmatism and metamorphism, where the Jiamusi massif (including the East Bureya terrane) is an Early Neoproterozoic block and the eastern Songnen massif (including the West Bureya terrane) is a Late Neoproterozoic-Cambrian block. Between these two blocks is the Spassk-Wuxingzhen-Melgin suture formed by their collision late in the Cambrian. The Bureya-Songnen-Jiamusi-Khanka superterrane formed as a part of the Gondwana supercontinent about 500 Ma ago through orogeny and accretion of the Rodinia supercontinent fragments.

Genesis of the Weizigou Au Deposit, Heilongjiang Province, NE China: Constraints from LA-ICP-MS Trace Element Analysis of Magnetite, Pyrite and Pyrrhotite, Pyrite Re-Os Dating and S-Pb Isotopes

The Weizigou Au deposit in Heilongjiang Province, NE China, located in the southern Jiamusi Massif, shows similarities to IOCG deposits. To determine the mineralization age, sources of ore-forming materials and genetic type, pyrite Re-Os dating, S-Pb isotopic analysis, in situ sulfur analysis and LA-ICP-MS analysis of trace elements in magnetite, pyrite and pyrrhotite were conducted. Four pyrite samples yielded a Re-Os isochron age of 197 ± 11 Ma, implying the occurrence a metallogenic event in the Early Jurassic. The δ34S values of sulfides display a relatively narrow range from 4.70‰ to 12.83‰ (mainly 9.90‰ to 12.83‰), which may be accounted for the extensively exposed granitic gneiss and meta-gabbro, with δ34S values of 7.44‰ to 8.44‰ and 4.37‰ to 10.54‰, respectively. Sulfide lead isotopic compositions have 206Pb/204Pb = 18.605–20.136, 207Pb/204Pb = 15.637–15.710 and 208Pb/204Pb = 38.534–39.129, indicating that the lead was derived from a mixed source. Magnetite has the characteristics of a lower Ti content and higher Zn content, indicating that it should be of hydrothermal origin, which may be related to IOCG-type mineralization. Pyrite and pyrrhotite have a Co/Ni ratio greater than 1 and a lower As content, indicating that they are of magmatic hydrothermal origin. Integrating the above analysis results, we inferred that the Weizigou Au deposit experienced the IOCG-type mineralization in the Middle-Late Permian, associated with magmatic-hydrothermal mineralization in the Early Jurassic.

Detrital Zircon U‐Pb Geochronology of the Xilin Group: Constraints for the Early Paleozoic Tectonic Evolution of the Songliao Massif

AbstractThe Xilin Group, composed of the Chenming, Laodaomiaogou, Qianshan and Wuxingzhen formations, is one of the Early Paleozoic terranes in the eastern Songliao Massif, mainly consisting of thick layers of fine clastic and carbonate rocks. This study presents LA‐ICP‐MS zircon U‐Pb geochronological data for the Laodaomiaogou and Qianshan formations, further constraining their provenance and the Early Paleozoic tectonic evolution of the Songliao Massif on the eastern Central Asian Orogenic Belt. Most zircons from the Laodaomiaogou and Qianshan formations show magmatic oscillatory zoning and high Th/U ratios (0.26–2.41). Zircon U‐Pb dating results indicate that the detrital zircons from the silty mudstone of the Laodaomiaogou Formation yield peak ages of 634 Ma, 775 Ma, 820 Ma, 880 Ma and 927 Ma, as well as multi‐episodic Archean to Paleoproterozoic and Mesoproterozoic ages (1405–643 Ma), implying its deposition time is younger than ∼634 Ma. Furthermore, the occurrence of Early Cambrian fossils indicates that the Laodaomiaogou Formation was deposited during the late stage of the Early Cambrian (∼514 Ma). The zircons from the K‐bentonite of the Qianshan Formation show four peak ages of 444 Ma, 471 Ma, 489 Ma and 518 Ma and the youngest age peak of 444 ± 4 Ma (n= 6) indicates that the Qianshan Formation was deposited during the Late Ordovician. In addition, the peak ages of the detrital zircons in the silty mudstone of the Qianshan Formation are 472 Ma and 498 Ma, as well as two other concordant points with207Pb/206Pb apparent ages of 1824 Ma and 1985 Ma. The dating results in this study, together with published data, indicate the absence of Pan‐African magmatic events in the Songliao Massif prior to the initial deposition of the Xilin Group, in contrast to those distributed widely in the Jiamusi Massif. Taken together, we conclude that the depositional provenance of the Laodaomiaogou and Qianshan formations was derived from the Songliao Massif. Furthermore, the characteristics of the detrital zircon age composition and rock associations indicate that the Laodaomiaogou Formation formed in a passive continental margin environment, in contrast to the Qianshan Formation, which formed in an active continental margin environment. The above results also imply that the Songliao and Jiamusi massifs might not have collided before the Late Ordovician.

Detrital zircon U–Pb geochronology of Xilin Group: Constraints for the early Paleozoic tectonic evolution of the Songliao Massif

The Xilin Group, composed of the Chenming, Laodaomiaogou, Qianshan and Wuxingzhen formations, is one of the Early Paleozoic terranes in the eastern Songliao Massif, mainly consisting of thick layers of fine clastic and carbonate rocks. This study presents LA-ICP-MS zircon U-Pb geochronological data for the Laodaomiaogou and Qianshan formations, further constraining their provenance and the Early Paleozoic tectonic evolution of the Songliao Massif on the eastern Central Asian Orogenic Belt. Most zircons from the Laodaomiaogou and Qianshan formations show magmatic oscillatory zoning and high Th/U ratios (0.26–2.41). Zircon U-Pb dating results indicate that the detrital zircons from the silty mudstone of the Laodaomiaogou Formation yield peak ages of 634 Ma, 775 Ma, 820 Ma, 880 Ma and 927 Ma, as well as multi-episodic Archean to Paleoproterozoic and Mesoproterozoic ages (1405–643 Ma), implying its deposition time is younger than ∼634 Ma. Furthermore, the occurrence of Early Cambrian fossils indicates that the Laodaomiaogou Formation was deposited during the late stage of the Early Cambrian (∼514 Ma). The zircons from the K-bentonite of the Qianshan Formation show four peak ages of 444 Ma, 471 Ma, 489 Ma and 518 Ma and the youngest age peak of 444 ± 4 Ma (n = 6) indicates that the Qianshan Formation was deposited during the Late Ordovician. In addition, the peak ages of the detrital zircons in the silty mudstone of the Qianshan Formation are 472 Ma and 498 Ma, as well as two other concordant points with 207Pb/206Pb apparent ages of 1824 Ma and 1985 Ma. The dating results in this study, together with published data, indicate the absence of Pan-African magmatic events in the Songliao Massif prior to the initial deposition of the Xilin Group, in contrast to those distributed widely in the Jiamusi Massif. Taken together, we conclude that the depositional provenance of the Laodaomiaogou and Qianshan formations was derived from the Songliao Massif. Furthermore, the characteristics of the detrital zircon age composition and rock associations indicate that the Laodaomiaogou Formation formed in a passive continental margin environment, in contrast to the Qianshan Formation, which formed in an active continental margin environment. The above results also imply that the Songliao and Jiamusi massifs might not have collided before the Late Ordovician.

Late Paleozoic–Mesozoic subduction and accretion of the Paleo-Pacific Plate: Insights from ophiolitic rocks in the Wandashan accretionary complex, NE China

The Wandashan accretionary complex (AC), consisting of the Raohe and Yuejinshan complexes, is located on the continental margin of Northeast Asia and represents an excellent source of information about Paleo-Pacific subduction and accretion. However, the protolith nature and tectonic evolution of the Wandashan AC are under debate. This contribution reports new geochronological, geochemical, and Sr-Nd-Pb-Hf isotopic data for ophiolitic rocks from the Wandashan AC. The 169–166 Ma plagioclasites and homogeneous gabbros from the Raohe complex are OIBs while 228–214 Ma homogeneous gabbros are continental VABs. Cumulate gabbros from the Yuejinshan complex formed at 280–278 Ma and ~220 Ma and have similar characteristics with E-MORB and N-MORB, respectively. They are BABBs and their primary magma was derived from a source region between EMI and EMII that was affected by continental crustal contamination as well as subduction-zone metasomatism. Combined with previous studies, we suggest that the onset of subduction of the Paleo-Pacific Plate was in the Early Permian. Subsequently, a back-arc basin, whose present suture is on the eastern margin of the Jiamusi Massif, formed and widened during 280–232 Ma, after which the basin closed and BABBs were emplaced to form the Yuejinshan complex during 210–180 Ma. The formation of VABs of the Raohe complex is coincident with the closure of the back-arc basin, and together with the 169–166 Ma OIBs, they constitute a major part of the Raohe complex. The accretionary process was completed during 133–131 Ma. Taken together, the ophiolitic rocks indicating multistage magmatism in the Paleo-Wandashan region recorded the formation-closure process of back-arc basin and the accretionary process of the Wandashan AC, during the westward subduction of the Paleo-Pacific plate. The back-arc basin identified in our study sheds new lights on geodynamic evolution model of subduction and accretion of the Paleo-Pacific Plate on the continental margin of NE Asia.

Early Paleozoic magmatic events in the Bureya Continental Massif, Central Asian Orogenic Belt: Timing and tectonic significance

The Bureya Massif is one of the largest continental massifs in the eastern Central Asian Orogenic Belt. The reconstructions of tectonic scenarios for the evolution of this belt are mainly based on geochronological and geochemical data. However, relevant data from the Bureya Massif are scarce. Here, we report whole-rock geochemistry, zircon U-Pb geochronology, and Lu-Hf isotope data for Early Paleozoic granite intrusions to constrain the timing of the magmatic and tectonic processes in the Bureya Massif. Geochronological data yielded ages of 495 ± 5, 486 ± 8, 471 ± 6, 453 ± 2, and 426 ± 6 Ma for the granitoids in the Bureya Massif. The chemical composition of the Early Paleozoic granitoids mostly showed affinities to A-type (A2-subtype) granites. Furthermore, they have zircon εHf(t) values of −5.3 to +5.7, and two-stage model ages tHf(C) of 1.52–0.95 Ga. These results suggest that the parental magmas of the Early Paleozoic granitoids were derived either from melting of a dominantly Neo- and Mesoproterozoic crustal source. Early Paleozoic magmatism in the Bureya and Songnen–Zhangguangcai Range massifs was characterized by similar timing and identical Hf-in zircon isotope compositions. Additionally, both arrays contain early Neoproterozoic granitic intrusions and Early Cambrian and Ordovician sedimentary units, suggesting that they were part of a single continental massif at the beginning of the Cambrian or even in the Neoproterozoic. In this case, the tectonic nature of the Early Paleozoic magmatism in these two massifs should be the same and was probably related to the docking of the Jiamusi Massif.

Transition from a passive to active continental margin setting for the NE Asian continental margin during the Mesozoic: Insights from the sedimentary formations and paleogeography of the eastern Jiamusi Massif, NE China

Abstract The Mesozoic tectonic evolution of the NE Asian continental margin has received much attention in recent years. However, previous studies focused mainly on the petrogenesis of igneous rocks and their relationship with Mesozoic tectonics, and there have been few studies of the Mesozoic sedimentary formations of the NE Asian continental margin. We combined zircon U-Pb ages with Hf isotopic and biostratigraphic data to reconstruct the Mesozoic paleogeography of the NE Asian continental margin. The results indicate that Mesozoic strata of the eastern Jiamusi Massif, NE China, include the Upper Triassic Nanshuangyashan Formation (Norian), Lower Jurassic volcanic rocks, and Lower Cretaceous Longzhaogou Group. The Upper Triassic Nanshuangyashan Formation consists of a suite of alternating marine and terrestrial sedimentary rocks with abundant fossils that formed in a passive continental margin setting. The Lower Jurassic strata comprise a suite of calc-alkaline volcanic rocks that include basaltic andesites, andesites, and rhyolites that formed in an active continental margin setting related to initial subduction of the Paleo-Pacific Plate beneath Eurasia. The Lower Cretaceous Longzhaogou Group belong to alternating marine and terrestrial sedimentary formations that formed in an active continental margin setting related to subduction of the Paleo-Pacific Plate. Here, we integrate these data to reconstruct the Mesozoic tectonic history of the NE Asian continental margin, which comprises a Late Triassic passive continental margin, the initiation of subduction of the Paleo-Pacific Plate in the Early Jurassic, and westward subduction and rollback of the Paleo-Pacific Plate in the Early Cretaceous.

Metamorphic evolution of high-grade granulite-facies rocks of the Mashan Complex, Liumao area, eastern Heilongjiang Province, China: Evidence from zircon U–Pb geochronology, geochemistry and phase equilibria modelling

The nature and age of the Mashan Complex (or Mashan Group) in northeast China is key for determining the Precambrian geological evolution and origins of the Jiamusi Massif. Here we present a detailed investigation of high-grade granulite-facies rocks of the Mashan Complex from the Liumao area, Heilongjiang Province, China. This includes zircon U–Pb dating, petrological and geochemical analysis, geothermobarometry, phase equilibria modelling, and a P–T path. The metamorphic rocks consist mainly of two groups: pelitic and felsic granulites; amphibolite-facies Sil–Grt–Bi, Sil–Grt, and Grt–Bi gneisses. The protoliths of the metamorphic rocks were clay rocks and sandstones, which were derived dominantly from silicic rocks in a continental island arc setting. In the pelitic granulites, four metamorphic assemblages (M1–M4) were recognised. Three metamorphic assemblages (M2–M4) were identified in the felsic granulites. Geothermobarometric data and phase equilibria modelling indicate that the M2, M3, and M4 assemblages in the pelitic granulite were metamorphosed at 9.2 kbar/845–865 °C, 4.7–5.1 kbar/820–865 °C, and 4.0–4.8 kbar/660–720 °C, respectively. These features imply a collisional orogenic process with a clockwise P–T path with nearly isothermal decompression segments. Similar results were obtained for the felsic granulite, with the metamorphic P–T conditions of the peak assemblage (M2) evaluated as 9.0–9.2 kbar/845–870 °C. The similar P–T paths indicate that the rocks underwent an evolutionary process that started with crustal thickening (M2), followed by rapid crustal uplift (M3), and then final cooling (M4). Based on our new zircon U–Pb age data, the peak of granulite-facies metamorphism in the Liumao area of the Jiamusi Massif occurred at ca. 530 Ma and final cooling occurred at ca. 490 Ma.

The metamorphic characteristics of metapelites of the Mashan Group in Mashan area, eastern Heilongjiang Province, China: Constraint on the crustal evolution of the Jiamusi Massif

Mashan Complex in the southeastern margin of the Jiamusi Massif has traditionally been interpreted to be the oldest stratigraphic sequence in eastern NE China. Here we investigated the Mashan Complex in the Ximashan area and present lots of new LA–ICP–MS zircon U–Pb, petrological and mineralogical chemical data, in addition with phase equilibria modeling, to constrain the timing of metamorphism, P–T conditions and the P–T path of the Mashan Complex, and furthermore to deduce the crustal evolution of the Jiamusi Massif. The protoliths of the metapelites from the Mashan Complex in the Ximashan area are clay rocks and sandstones, whose provenance is dominantly felsic rocks which formed from a continental island arc. Three metamorphic generation assemblages (M2–M4) are recognized in the studied samples: a peak granulite facies stage, a post-peak near-isothermal decompression stage, and a late near-isobaric cooling stage, which together define a clockwise P–T path. It reveals important information related to the collision orogeny, subsequent uplift, and post-collision process. Zircon U–Pb dating of two metapelitic samples yielded metamorphic ages of the older group varying from 535 ± 6 to 480 ± 5 Ma, which can be perfectly correlated with the age range (501 ± 6 to 498 ± 6 Ma) of magmatic activities recorded by the gneissic granite sample. The data presented here, together with those published, allow us to preliminarily infer that the peak of the granulite-facies metamorphism in the Ximashan area of the Jiamusi Massif might have occurred at 530–500 Ma. The younger of the metamorphic ages (476–453 Ma) should be regarded as the age of late stage. Therefore, a collision orogeny regime is favored to interpret the metamorphic evolution of metapelites of the Mashan Group in the Mashan area.

Magma mixing in Early Jurassic granites in the Lesser Xing'an Range, NE China: Evidence from petrology, geochronology, and Lu–Hf isotopes

The contribution of the mantle to the formation of granites with mantle‐like or juvenile crustal properties having positive εHf(t) and εNd(t) values remains ambiguous. We have carried out petrologic, geochemical, and zircon U–Pb–Hf–O isotope composition analyses on the Woniuhe and Yuantoupiao granites and associated enclaves with such properties in the northern and southern Lesser Xing'an Range, NE China to determine the crust–mantle interactions involved in the petrogenesis of these host granites and enclaves. The two host granites and their enclaves have identical crystallization ages of ~180–175 Ma within analytical error. The petrological, mineral microstructural, geochronological, Hf–O isotopic, and whole‐rock geochemical data imply that mixing between felsic and mafic magmas occurred in both the Woniuhe and Yuantoupiao plutons. The primary magmas of the enclaves in the two plutons most likely are both mantle‐derived. Hence, mantle materials were directly involved in the genesis of both the Woniuhe and Yuantoupiao host granites through the emplacement of mantle magmas. Combined with the published petro‐geochemical data, our data indicate that large‐scale underplating and emplacement of mantle magmas following crustal growth can occur and may be responsible for the magmatism in the region in the Early Jurassic. This underplating and emplacement might be related to the subduction of the oceanic plate between the Songliao and Jiamusi Massifs beneath the former.

Opening and closure history of the Mudanjiang Ocean in the eastern Central Asian Orogenic Belt: Geochronological and geochemical constraints from early Mesozoic intrusive rocks

The tectonic evolution of the ancient Mudanjiang Ocean within the Central Asian Orogenic Belt (CAOB), is strongly debated. The ocean played an important role in the amalgamation of the Songnen and Jiamusi massifs; however, the timings of its opening and closure have remained ambiguous until now. In this study, we analyzed early Mesozoic intrusive rocks from the eastern Songnen and western Jiamusi massifs in the eastern CAOB. The new zircon UPb ages, Hf isotope data, and whole-rock major and trace element data are used to reconstruct the tectonic evolution of the Mudanjiang Ocean. Zircon UPb dating indicates that early Mesozoic magmatism in the eastern Songnen Massif occurred in three stages: Early to Middle Triassic (ca. 250 Ma), Late Triassic (ca. 211 Ma), and Early Jurassic (ca. 190 Ma). The Triassic intrusive rocks typically consist of bimodal rock suites, which include gabbros, hornblende gabbros, and granitoids. The compositional information indicates an extensional environment that was probably related to the final closure of the Paleo-Asian Ocean. We integrated the results with observations from Triassic A-type granitoids and coeval sedimentary formations in the eastern Songnen Massif, as well as depositional ages of metasedimentary rocks from Heilongjiang Complex. We conclude that the opening of the Mudanjiang Ocean took place in the Early to Middle Triassic. The Early Jurassic intrusive rocks are bimodal and include olivine gabbros, hornblendites, hornblende gabbros, gabbro diorites, and granitoids. The bimodal rock suite indicates a back-arc style extensional environment. This setting formed in relation to westward subduction of the Paleo-Pacific plate beneath the Eurasia during the Early Jurassic. Following subduction, the closure of the Mudanjiang Ocean and subsequent amalgamation of the Songnen and Jiamusi massifs happened during the late Early Jurassic to Middle Jurassic. This sequence of events is further supported by ages of metamorphism and deformation acquired from the Heilongjiang Complex. Based on these observations, we conclude that the Mudanjiang Ocean existed between the Middle Triassic and Early Jurassic, making it rather short-lived.