Great Xing’an Range Research Articles

Overprinting Mineralization in the Huoluotai Porphyry Cu (Mo) Deposit, NE China: Evidence from K-Feldspar Ar-Ar Geochronology and S-Pb Isotopes

The Great Xing’an Range (GXR) is a significant belt of polymetallic deposits located in the eastern segment of the Central Asian Orogenic Belt. The recently found Huoluotai porphyry Cu (Mo) deposit is situated in the northern GXR region in northeastern (NE) China. The deposit has been studied extensively using field geology and geochronological methods, which have identified two distinct mineralization events. These events include an early occurrence of porphyry-type Cu (Mo) mineralization and a later occurrence of vein-type Cu mineralization. Prior geochronology investigations have determined an approximate age of 147 Ma for the early porphyry-type Cu (Mo) mineralization. 40Ar/39Ar dating of K-feldspar of the altered Cu-mineralized quartz diorite porphyry veins for the overprinting vein-type Cu mineralization provides plateau ages of 123.1 ± 1.5 Ma, 122.3 ± 2.8 Ma, and 122.2 ± 0.4 Ma. Sulfide S-Pb isotope compositions of the two mineralization events suggest that both have a magmatic source. The origin of ore-forming metals displays the features of a crust–mantle mixing origin. The regional extensional tectonic setting in NE China during the Early Cretaceous was caused by large-scale lithosphere delamination and upwelling of the asthenospheric mantle. These processes were triggered by the rollback of the Paleo-Pacific Plate. The tectonic event in question resulted in the lithospheric thinning, significant magmatic activity, and mineralization in NE China.

Coupling Between Exhumation and Subduction: A Case Study From the Southern Great Xing'an Range, NE Asia

AbstractThe link between subduction and continental exhumation is explored using high‐resolution thermal histories from southern Great Xing'an Range (GXR), NE Asia and integrated with a regional low‐temperature thermochronology data synthesis from the NE Asian continental margin. The GXR thermal histories are constrained by multiple thermo‐, geochronometers (zircon, titanite, apatite U‐Pb, zircon, apatite (U‐Th)/He and apatite fission track). These data yield a large range in U‐Pb ages (292–119 Ma) with enhanced exhumation mainly during the early Cretaceous (ca. 155–110 Ma) in an extensional regime linked to roll‐back of the Paleo‐Pacific Ocean and consequent lithospheric thinning and delamination. Integrated with Cretaceous‐Cenozoic low‐temperature thermochronological data from the NE Asian continent margin, three regional phases of exhumation are recognized, which can be linked to changes in the geometry and kinematics of the subduction systems of the Paleo‐Pacific and Pacific oceans, demonstrating coupling between the subducting plate and the continental margin at active plate boundaries.

Fluid evolution and ore genesis of the Weilasituo Li-Sn-Cu-Zn polymetallic deposit in Inner Mongolia: Evidence from fluid inclusion and C-H-O-Li isotopes

The Weilasituo Li-Sn-Cu-Zn polymetallic deposit is located in the southwestern Great Xing'an Range (GXR), and crypto-explosive breccia-type and hydrothermal vein-type mineralization are developed in the mining area. With the Early Cretaceous amazonite granite as the mineralization center, the greisen-type Li(-Rb) mineralization is developed in the crypto-explosive breccia pipe above the granite, and the quartz vein-type Sn(-W-Mo) and Cu-Zn(-Ag) mineralization is successively developed in the surrounding Paleoproterozoic Xilinguole complex, forming mineralization zoning. The polymetallic metallogeny comprises early Li (Rb) through Sn(-W-Mo) to late Cu-Zn(-Ag) mineralization, and can be divided into six stages: (I) zinnwaldite–topaz–fluorite, (II) quartz–arsenopyrite–cassiterite–sphalerite–wolframite, (III) quartz–molybdenite–polymetallic sulfides, (IV) quartz–arsenopyrite–pyrite–chalcopyrite, (V) quartz–chalcopyrite–pyrrhotite–sphalerite–galena ± pyrite, and (VI) quartz–calcite–fluorite.Fluid inclusions (FIs) in the zinnwaldite, topaz and fluorite of Li(-Rb) ore phase contain high-temperature medium-salinity (348–404℃; 5.09–9.60 wt%) vapor–liquid two–phase aqueous type (vapor–liquid ratio: 35–70 %), similar to intermediate-density (ID) type FIs, and represent a single-phase fluid directly exsolved from the magma; FIs in the Sn(-W-Mo) ore phase quartz contain daughter mineral-bearing three-phase (SVL), vapor (V), vapor-rich two-phase aqueous (LV) and liquid-rich two-phase aqueous (VL) type, reflecting fluid boiling; FIs in the Cu-Zn(-Ag) ore phase quartz contain CH4 ± CO2 two-phase FIs and VL-type FIs, indicating fluid immiscibility. Lithium isotope data show that the Li ore-forming material was crustal derived, while H-O isotope data indicate that the ore fluid was derived from magmatic water and mixed with meteoric water in the late Cu-Zn(-Ag) ore phase; Carbon isotope data suggest that the CH4 and CO2 in the FIs were sourced from the fluid-rock reaction between the hydrothermal fluid and with the Xilinguole Complex graphite-bearing wallrocks. Raman spectroscopy shows that stage Ⅱ-Ⅴ FIs contain CH4 and CO2, whose content increased markedly from the Sn(-W-Mo) to Cu-Zn(-Ag) stage, indicating that CH4 and CO2 are enriched continuously with fluid migration and fluid-rock reaction.We conclude tha the initial single-phase ID Li-Rb-W-Sn-rich fluid was exsolved from the magma, and formed the Li(-Rb) mineralization in the crypto-explosive breccia pipe as the temperature dropped. Subsequently, the fluid entered the faults and the pressure dropped, causing fluid boiling, and triggered the proximal Sn(-W-Mo) vein-type mineralization. With the fluid migration and more water–rock reaction, CH4 and CO2 are continuously enriched and fluid immiscibility occurred, forming the distal Cu-Zn(-Ag) vein-type mineralization.

Paleozoic and Mesozoic magmatism in the Gaodi porphyry Mo-Cu deposit: Implications for the evolution of the Mongol-Okhotsk Ocean in the northern Great Xing'an Range, NE China

The newly discovered "460 Gaodi porphyry Mo–Cu deposit" (with Re-Os age of 179.6 ± 3.6 Ma) is located 30 km west of Hanjiayuanzi town in the northern Great Xing’an Range (GXR), NE China. The intrusive rocks in the deposit area can be classified into four periods: (1) Early Ordovician, which includes a high-K calc-alkaline monzodiorite (480 Ma) indicating significant crustal contamination, and a “syntectic” I-type granodiorite (479 Ma) with low Mg# values (34–38) and εHf(t) values (−4.4 to +0.9) show mixing of mantle-crust derived materials, which is related to post-orogenic event between the Ergun and Xing’an blocks; (2) Late Triassic, which includes an adakitic granodiorite porphyry (220 Ma) related to partial melting of the lower part of a thickened crust (C-type adakitic) with low Na2O/K2O ratio (1.27–1.49), Cr and Ni contents, with εHf(t) values of −0.7 to +3.3; (3) early Early Jurassic, which includes a differentiated I-type monzogranite (198 Ma) and syenogranite (196 Ma) with negative Eu anomaly (0.06–0.74), low Mg# (9–37) and high Rb/Sr (0.84–5.07). The εHf(t) values of them are −3.3 to 1.8 and −3.0 to +2.3, respectively, indicating the same source areas originated from partial melting of juvenile lower crust; (4) late Early Jurassic, which includes an ore-related C-type adakitic granite porphyry (182 Ma) with relative low Mg# (36–38), and low Na2O/K2O (0.65–0.81), strongly peraluminous quartz porphyry (181 Ma) with highly differentiated characteristics, and post-collisional gabbroic diorite (180 Ma). The ore-related granite porphyry yields εHf(t) values ranging from −4.1 to −0.4, suggesting partial melting of juvenile lower crust. The 460 Gaodi deposit formed in a late-collisional setting related to the Mongol-Okhotsk Ocean system. A post-collisional stage about 182 to 163 Ma immediately following the main collision is proposed.

Cretaceous source to sink system reconstruction of northeastern Asian continental margin: Insight from integrated detrital geochronology in NE China

The Cretaceous sedimentary successions in NE China are largely incomplete as the basins are inverted and younger strata are eroded. Except for the Songliao Basin, whose depositional record has remained relatively intact, the burial record to the east was interrupted in the late Early or Late Cretaceous. There is still controversy on the possible connection between the Songliao Basin and the eastern basin group, as well as the extent of the previously suggested “pan-Sanjiang” proto-basin that covered most current eastern satellite basins. To address these questions, we studied modern river catchments of variable sizes from sediment-supplying basement highs that cover most of eastern NE China to track the intense denudation events and provenance changes through the Cretaceous. We found a great inconsistency between detrital age patterns of the modern river sands and the spatial proportions of the source units. The detrital age distributions allow to re-evaluate the basement units that are mostly composed of the Triassic–Jurassic igneous suite and some metasedimentary units with Paleozoic ages, but the contribution from Proterozoic formations is negligible. Combining the newly dated modern catchment detrital U-Pb ages, the region-wide compilation of the basement emplacement ages, and the U-Pb ages in the Cretaceous formations in NE China, we systematically refine the Cretaceous provenance history. In the Early Cretaceous, the eastern satellite basins accumulated sediments from the Lesser Xing’an range (LXR) in the west, Zhangguangcai range (ZGCR) in the south, and the Nadanhada terrane (NT) in the east. The sediment of the southern Songliao Basin derived from the North China Craton (NCC) and from ZGCR but barely from the Great Xing’an Range (GXR). The Jiamusi uplift (JU) did not provide sediments to the eastern satellite basins and the Songliao Basin.In the Late Cretaceous, the eastern satellite basins received sediments from the exhumed JU but barely from ZGCR and LXR. The Songliao Basin still accumulated the sediments from the NCC, some south part of ZGCR, and GXR but minor from the central and northern ZGCR and LXR. Between the latest Early Cretaceous and early Late Cretaceous, a much wider proto-basin was suggested in NE China than previously assumed. It covered during its maximum extension period the current Songliao Basin, the eastern satellite basins, the LXR, ZGCR, JU, and partial GXR basement areas. The provenance change is induced by the Paleo-Pacific plate motion change, i.e., with the subduction direction change, the roll-back, and two-stage limited flat slab subduction trigged the formation of the basin-and-range system in NE China since the Early Cretaceous. Moreover, we suggest conducting modern sand provenance analysis to detect, verify or re-classify the ages of the zircon-bearing units, especially at a reconnaissance prospecting on areas covered by imprecise large-scale geological maps only to reveal the catchment better.

Undulating electrical lithosphere–asthenosphere boundary beneath Northeast China; as revealed by long–period magnetotelluric data

The geometry of continental lithosphere–asthenosphere boundary (LAB) significantly affects the movements of tectonic plates and flow of the upper mantle. However, the properties and geometry of this boundary beneath tectonically active regions in Phanerozoic continents are mysterious and elusive. Ninety–three long–period magnetotelluric (LMT) observations across Northeast China (NEC) provide a unique opportunity to image the shape of the LAB. Probabilistic resistivity–depth model inversion was employed to obtain the one–dimensional resistivity structure beneath each LMT site. The depth of the electrical LAB is constrained by the most probable interface at which the resistivity changes rapidly from high to low. The inversion results show that the electrical LAB is undulating beneath NEC. The North–South Gravity Lineament marks the transition from deep to shallow LAB. The thickest lithosphere occurs beneath the Great Xing'an Range (GXAR), where the LAB is ∼200 km deep. The electrical lithosphere is relatively thin in the east, with the thinnest lithosphere (∼50 km) being found beneath the Changbai Mountain volcano. We speculate that melt depletion, together with possible mantle downwelling are the likely causes for the formation of the thick GXAR lithosphere. The unresolved lithosphere beneath the northern Songliao Basin could be ascribed to the strong attenuation of electromagnetic waves in highly conductive sedimentary layers or the weak difference in the resistivity of the lithosphere and asthenosphere. The lithosphere steps that can form the edge-driven convection in the asthenosphere may play key roles in forming the widely-spread intraplate magmatism in NEC.

Protracted extraction of high-silica melts from an upper-crustal magma reservoir recorded by the Wuchagou volcanic rocks in central Great Xing'an Range, NE China

High-silica volcanic rocks and their plutonic counterparts carry critical information concerning the evolution of shallow magmatic systems and construction of silicic upper continental crust, yet their origins remain debatable. Here, we examine high-silica volcanic rocks from the Lower Cretaceous Manitu and Baiyin'gaolao formations of the Wuchagou volcanic field, central Great Xing'an Range (GXR), to constrain the genesis of these high-silica volcanic rocks and the evolution of the Wuchagou magmatic system. Geochronological data suggest that the Manitu and Baiyin'gaolao volcanic rocks represent a prolonged eruption from the Wuchagou magmatic system, spanning Period I (135–129 Ma ) and Period II (127–122 Ma ) magmatism in the central GXR. Their slightly depleted ε Nd (t) values and relatively young model ages coincide with a juvenile crustal origin. We suggest that the Manitu and Baiyin'gaolao high-silica volcanic rocks are the evolved compositions of their coexisting intermediate rocks given the similarities in both formation age and Sr-Nd isotopic composition and systematic geochemical variations. Clinopyroxene- and amphibole-based thermobarometers respectively yield low average pressures of ~3.3 kbar and ~ 1.8 kbar with low temperatures of ~1013 °C and 875 °C. Also, Clinopyroxene- and amphibole-based hygrometry yield relatively high H 2 O contents of ~2.7–4.1 wt% and ~ 3.1–4.6 wt%. Together, they indicate the presence of a hydrous upper-crustal magma reservoir feeding the eruptions of the Manitu and Baiyin'gaolao high-silica volcanic rocks. Combining the behavior of highly incompatible elements (Rb and Th) with trace element modeling results, we show that the Wuchagou high-silica volcanic rocks formed by protracted extraction of high-silica melts in the upper crust, with complementary residual cumulates partially disguised in the Early Cretaceous felsic plutons in the central GXR. Our results highlight the significance of prolonged upper-crustal differentiation of magmas derived from juvenile crust in the development of the high-silica upper continental crust. • High-silica volcanic rocks extracted from a long-lived upper-crustal reservoir. • Complementary residual cumulates disguised in contemporaneous felsic plutons. • Crystal-melt segregation contributed to development of high-silica upper crust.

Age and genesis of the Lamahanshan Ag-Pb-Zn deposit, southern Great Xing'an Range, northeastern China: Constraints from sphalerite Rb-Sr dating, fluid inclusions and H-O-S-Pb isotopes

The Lamahanshan deposit in the eastern Central Asian Orogenic Belt (CAOB) is a newly-discovered Ag-Pb-Zn vein deposit in the southern Great Xing'an Range (GXR). Vein-type Ag-Pb-Zn orebodies are mainly hosted in the fracture zones of gneissic plagiogranite, granite porphyry, and quartz porphyry. Mineralization comprises four stages: (I) quartz-magnetite, (II) quartz-pyrite-chalcopyrite, (III) quartz-polymetallic sulfides, and (IV) quartz ± sphalerite. Sphalerite Rb-Sr dating yielded an isochron age of 137.7 ± 6.1 Ma, coeval with the regional Late Jurassic-Early Cretaceous Pb-Zn polymetallic mineralization. Three types of fluid inclusions (FIs), namely vapor-rich two-phase (LV-type), liquid-rich two-phase (VL-type), and daughter mineral-bearing three-phase (SL-type), are distinguished at Lamahanshan. Stage I and II contain all FI types with homogenization temperatures (Th) of 383–418 °C and 350–392 °C and salinities of 0.9–38.1 wt% and 0.7–35.0 wt%, respectively, whereas stage III contain VL- and LV-type FIs with Th = 318–349 °C and salinity = 0.7–10.5 wt%. Only VL-type FIs occur in stage IV, with Th of 271–320 °C and salinities of 4.3–7.8 wt%. The microthermometric and H-O isotope data (δ18OH2O = −9.4 to 0.9‰ and δD = −137.0 to −124.7‰) indicate that the ore-forming fluids were initially magmatic with later meteoric water incursion. Fluid boiling, cooling, fluid-rock reactions, and meteoric water mixing were the major ore precipitation mechanisms at Lamahanshan. The sulfide S (δ34S = 4.0–6.7‰), Sr ((87Sr/86Sr)i = 0.698957–0.700069), and Pb (206Pb/204Pb = 17.230–18.193, 207Pb/204Pb = 15.440–15.627, and 208Pb/204Pb = 37.664–38.407) isotopes also support that the metals were magmatic-derived. Integrating the available geological, mineralization, fluid inclusion, and H-O-S-Sr-Pb isotope evidence, we propose that the Lamahanshan deposit shares many similar features with distal magmatic-hydrothermal vein-type ores, and was formed in an extensional setting related to the Early Cretaceous Paleo-Pacific subduction rollback.

A synthesis of geochemistry of Mesozoic igneous rocks in NE China and tectonic superposition and transformation of the easternmost Central Asian Orogenic Belt

As the product of the amalgamation of multiple microcontinental massifs, Northeast China is located in the easternmost segment of the Central Asian Orogenic Belt (CAOB), which underwent multi-stage tectonic superposition in Mesozoic. Extensive and intensive igneous activities occurred throughout northeast China and the related igneous rocks can be considered as an effective probe for constraining tectonic evolution. In this study, numerous available ages and geochemical data are collected from published literature. The spatial-temporal distribution, rock assemblage, and geochemical characteristics of Mesozoic igneous rocks are systematically reassessed and summarized. A conclusion is drawn that NE China experienced the superposition and transformation of the Paleo-Asian Ocean (PAO) domain, the Mongol-Okhotsk Ocean (MOO) domain, and the Paleo-Pacific Ocean (PPO) domain in Mesozoic and detailed tectonic evolution is presented as follows. Firstly, NE China was under the joint effect of the MOO and the PAO during Early-Middle Triassic (ca. 252–237 Ma). Arc-type igneous rocks in the Erguna-Xing’an Block were induced by the southward subduction of the MOO Plate and adakites with high Sr/Y and (La/Yb)N ratios in the south segment of NE China were emplaced in the post-collision orogenic environment related to the closure of the PAO. Secondly, during Late Triassic, the influence of the PAO domain was gradually weakened, and igneous activities developed sporadically along the Solonker-Xar Moron-Changchun-Yanji suture zone. The MOO continued to subduct south until the Early Jurassic (ca. 220–190 Ma), and continental igneous rocks with arc-like features were widely distributed in the Erguna-Xing’an Block. During ca. 220–200 Ma, the Jiamusi-Khanka Massif was slipped away from the Songnen-Zhangguangcai Range Massif and this progress may be related to the PPO domain. Thirdly, in the Early Jurassic-Early Cretaceous (ca. 200–120 Ma), NE China came under the joint influence of the MOO and PPO tectonic domains. The subduction and closure of the MOO Plate and corresponding thickening of the lower crust resulted in widespread and intensive igneous activities in the Erguna and the Great Xing’an Range (GXAR). Two-stage subduction of the PPO and between which a period of change of subduction direction, induced the two-stage arc igneous activities of ca. 185–164 Ma and ca. 135–120 Ma, and the magmatic hiatus between ca. 163.5–135 Ma in the Zhangguangcai Range (ZGCR) and its east. Fourthly, the influence of the MOO domain was completed at ca. 120 Ma and numerous volcanic rocks corresponding chemically to A-type granite began to erupt violently, due to the rollback of the Paleo-Pacific oceanic slab. Since then, NE China has been completely under the control of the PPO domain.

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.

Early Cretaceous rapid exhumation processes in the southern Great Xing’an Range, NE China: implications for extensional geodynamics

ABSTRACT The Mesozoic-Cenozoic geological evolution of the southern Great Xing’an Range (GXR) has long been controversial since it is located in the superposed region of different tectonic regimes and involves complex interactions. Here, we present low-temperature thermochronological data from granitoids emplaced in multiple magmatic stages to delineate the tectono-thermal history and further understand the geodynamic process. Most zircon and apatite (U-Th)/He ages, within error, indicate Early Cretaceous: the zircon average (U-Th)/He ages range from 146.7 ± 8.7 to 120.0 ± 7.1 Ma, except for the oldest data (162.5 ± 9.6 Ma) and the apatite (U-Th)/He ages vary from 138.7 ± 8.2 to 94.8 ± 7.5 Ma, except for the youngest age (70.8 ± 4.3 Ma). Systematic numerical modelling reveals that a rapid cooling and exhumation process with rates of 2.5-10 oC/Ma and 0.07-0.29 mm/yr occurred in the southern GXR during the early Cretaceous (145–110 Ma). We propose that the rapid uplift and exhumation of intrusive rocks during the early Cretaceous is also a manifestation of the extensional regime in the southern GXR, which is dominated by the rollback of the subducted Paleo-Pacific oceanic plate superposed by the post-orogenic extensional collapse of the Mongol-Okhotsk belt. In addition, the slow exhumation process since the late Cretaceous (~0.01 mm/yr) suggests that the Paleo-Pacific Ocean tectonic regime has a weak impact on the southern GXR area.

Timing and ore formation of the Xiaokele porphyry Cu (–Mo) deposit in the northern Great Xing’an Range, NE China: Constraints from geochronology, fluid inclusions, and H–O–S–Pb isotopes

The Xiaokele Cu (–Mo) deposit is a newly discovered porphyry deposit in the northern Great Xing’an Range (GXR) of northeast China. The multiphase hydrothermal superposition on the Xiaokele Cu (–Mo) deposit obscures temporal relationships between quartz veins/veinlets in different mineralization stages, and consequently limits the understanding of the origin and evolution of the ore-forming fluids and metal precipitation mechanism. In this study, we document detailed descriptions of alteration and vein mineral paragenesis in the Xiaokele Cu (–Mo) deposit, present LA–ICP–MS zircon U–Pb and molybdenite Re–Os geochronology, the microthermometry and laser Raman spectroscopy of the fluid inclusions (FIs), and H–O–S–Pb isotope compositions. Four mineralization stages are identified, with stage II being the main Cu mineralization stage. The molybdenite Re–Os dating yielded a weighted average age of 148.7 ± 0.9 Ma (MSWD = 0.52), which is similar to the LA–ICP–MS zircon U–Pb age of 149.3 ± 0.9 Ma (MSWD = 0.15) yielded by the granodiorite porphyry. The δ34SV–CDT values of the sulfides (–1.2 to 2.4‰) conform the recognized magmatic sulfur values, indicating that the sulfur may have a magmatic origin. The Pb isotope compositions of the sulfides (206Pb/204Pb = 18.280–18.386, 207Pb/204Pb = 15.549–15.588, and 208Pb/204Pb = 38.153–38.359) coincide well with those of the Xiaokele granodiorite porphyry. These results indicate that the Xiaokele Cu (–Mo) deposit has a close genetic relationship with the granodiorite porphyry, and the ore-forming materials likely originated from the granodiorite porphyry. Petrographic/compositional characteristics of FI assemblages suggest that the ore-forming fluids belong to an H2O–NaCl–CO2 system in stage I and an H2O–NaCl system from stages II to IV, and fluid boiling occurred from stages I to III. The FI homogenization temperatures show a decreasing trend from stages I to IV. The δ18OH2O values (6.4 to 7.7‰) of quartz in stages I and II are similar to typical magmatic water values, but the δD (–142.5 to –125‰) and δ18OH2O (–1.1 to 3.4‰) of quartz in stages III and IV are significantly lower than magmatic water values, indicating that the ore-forming fluids were magmatic in origin and gradually mixed with meteoric water from stages III to IV. Microthermometric data show that Cu-bearing sulfides in stage II were mainly deposited at a temperature below 400 °C, indicating that fluid cooling was the primary factor that controlled Cu precipitation in the Xiaokele Cu (–Mo) deposit. Our research on the Xiaokele porphyry Cu (–Mo) deposit will help to provide a scientific basis for future prospecting of this deposit and even the Late Jurassic porphyry deposits in the northern GXR.

Fluid inclusion and isotopic constraints on the origin of the Ag-Pb-Zn polymetallic mineralization at Biliya, Great Xingan Range, NE China

The Biliya Ag-Pb-Zn polymetallic (SLZP) deposit (16.5 Mt, @ 52.9 g/t Ag, 2.6% Pb and 2.3% Zn) lies in the Great Xing’an Range, Northeast China. Breccia-, veinlet- and vein-type Ag-Pb-Zn ore bodies are primarily hosted in the quartz porphyry, trachyandesite and rhyolitic tuff. They are spatially and temporally related to andesitic porphyry. Three mineralization processes are identified: stage I: grey quartz - pyrite + tawny sphalerite (high Cd2+), stage II: grayish white quartz - pyrite + grey sphalerite (high Fe2+) + galena + argentite + tetrahedrite, stage III: white quartz-pyrite. The alterations consist of quartz + sericite, illite + quartz, fluorite + calcite + opal and chlorite zone. The silver-lead–zinc mineralization primarily corresponds to stage II. Five sulfide samples from stage II yielded a well-fitted isochron age of 131.3 ± 2.4 Ma (MSWD = 2.4), marking the timing of Ag-Pb-Zn polymetallic mineralization. CO2-bearing NaCl-H2O (C), gaseous CO2 (V); vapour-liquid H2O-NaCl (WL) and fluid-phase H2O-NaCl (L)-type of fluid inclusions were distinguished. Their petrographic and microthermometric features and H-O isotopic data suggest that the hydrothermal fluids were initially originated from magmatic source, with intensive mixing with meteoric water and that their temperatures and salinities are 254–130 ℃ and 7.15–1.22 wt% NaCl eqv, respectively, belonging to a reduced fluid (CO2-H2O-NaCl ± CH4) system. In-situ S and bulk Pb isotope analyses indicate that the metal materials were related to andesitic magma from the lower crust. The deposit geology, fluid inclusions, stable isotopes and chronology results suggest that the Biliya deposit belongs to a low-sulfidation (LS) epithermal SLPZ deposit. Boiling and fluid immiscibility coupled with suddenly decreasing in temperature, pressure, logfS2 of the hydrothermal fluids are likely to play important roles in Biliya SLPZ ore deposition.

Felsic Igneous Rocks in the Hua'aobaote Pb‐Zn‐Ag Polymetallic Orefield, Southern Great Xing'an Range: Genesis, Metallogenetic and Tectonic Significance

AbstractThe Hua'aobaote Pb‐Zn‐Ag Polymetallic orefield is situated in the southern section of the Great Xing'an Range (GXAR), which has experienced extensive magmatism. Since the Paleozoic, there are two stages of magmatism in Hua'aobaote orefield occurred in the Paleozoic and Mesozoic. The Mesozoic magmatism is of great significance for the Pb‐Zn‐Ag Polymetallic mineralization in Hua'aobaote orefield. In this study, new geochemical data was obtained to discuss the timing and petrogenesis of the magmatic rocks and its geodynamic and metallogenic significance. Zircon U‐Pb ages reveal that the felsic igneous rocks from the Hua'aobaote orefield were formed in the Early Permian (294.8 ± 3.2 Ma) and Early Cretaceous (132.6 ± 1.4 Ma). Geochemically, the Early Permian granodiorite porphyrite is characterized by high Sr/Y (42–63) ratios and Mg#(62.24–70.74) values and low heavy rare earth element (HREE) (5.09–6.79 ppm) contents. The granodiorite porphyrite is also characterized by depleted Sr–Nd initial isotopic signatures [∊Nd(t) = 5.91–7.59, (87Sr/86Sr)i= 0.7029–0.7030], exhibiting adakitic characteristics. The Early Cretaceous granite porphyry and rhyolite are A‐type felsic igneous rocks, and demonstrate high SiO2, Na2O + K2O and rare earth element (REE) contents, low CaO and MgO contents, low (87Sr/86Sr)iratios (0.7044–0.7058), and positive∊Nd(t) values (2.57–4.65). Whole‐rock Pb isotopic compositions in granodiorite porphyrite are:206Pb/204Pb = 17.631–18.149,207Pb/204Pb = 15.422–15.450, and208Pb/204Pb = 37.325–37.729. The granite porphyry and rhyolite have initial206Pb/204Pb,207Pb/204Pb, and208Pb/204Pb ratios of 18.106–19.309, 15.489–15.539, and 37.821–38.05, respectively. Sr‐Nd‐Pb isotopic evidence suggests that the Early Permian granodiorite porphyrite is likely to derive from slab melts and modified by peridotitic mantle wedge in the subduction tectonic setting of the Paleo‐Asian Ocean. The Early Cretaceous A‐type felsic igneous rocks were derived from juvenile lower crust, accompanied by limited crustal contamination and various degree of fractional crystallisation during magma emplacement. The Early Cretaceous magmatism and related mineralization were formed in a post‐orogenic tectonic setting that attributed to the closure of the Mongol–Okhotsk Ocean. Pb isotopic data for the various rock units in the study area indicate that the Mesozoic magma source contributed substantial Pb, Zn, and Ag to the Hua'aobaote deposit.

Petrogenesis and Tectonic Setting of Early Cretaceous Intrusive Rocks in the Northern Ulanhot Area, Central and Southern Great Xing’an Range, NE China

Abundant Early Cretaceous magmatism is conserved in the central and southern Great Xing’an Range (GXR) and has significant geodynamic implications for the study of the Late Mesozoic tectonic framework of northeast China. In this study, we provide new high-precision U–Pb zircon geochronology, whole-rock geochemistry, and zircon Hf isotopic data for representative intrusive rocks from the northern part of the Ulanhot area to illustrate the petrogenesis types and magma source of these rocks and evaluate the tectonic setting of the central-southern GXR. Laser ablation inductively coupled plasma–mass spectrometry (LA-ICP-MS) zircon U–Pb dating showed that magmatism in the Ulanhot area (monzonite porphyry: 128.07 ± 0.62 Ma, quartz monzonite porphyry: 127.47 ± 0.36, quartz porphyry: 124.85 ± 0.34, and granite porphyry: 124.15 ± 0.31 Ma) occurred during the Early Cretaceous. Geochemically, monzonite porphyry belongs to the metaluminous and alkaline series rocks and is characterized by high Al2O3 (average 17.74 wt.%) and TiO2 (average 0.88 wt.%) and low Ni (average 4.63 ppm), Cr (average 6.69 ppm), Mg# (average 31.11), Y (average 15.16 ppm), and Yb (average 1.62 ppm) content with enrichment in Ba, K, Pb, Sr, Zr, and Hf and depletion in Ti, Nb, and Ta. The granitic rocks (e.g., quartz monzonite porphyry, quartz porphyry, and granite porphyry) pertain to the category of high-K calc-alkaline rocks and are characterized by high SiO2 content (>66 wt.%) and low MgO (average 0.69 wt.%), Mg# (average 31.49 ppm), Ni (average 2.78 ppm), and Cr (average 8.10 ppm) content, showing an affinity to I-type granite accompanied by Nb, Ta, P, and Ti depletion and negative Eu anomalies (δEu = 0.57–0.96; average 0.82). The Hf isotopic data suggest that these rocks were the product of the partial melting of juvenile crustal rocks. Notably, fractionation crystallization plays a crucial role in the process of magma emplacement. Combining our study with published ones, we proposed that the Early Cretaceous intrusive rocks in the Ulanhot area were formed in an extensional tectonic background and compactly related to the subduction of the Paleo-Pacific Ocean plate.

Late Mesozoic magmatism and tectonic significance of the Kelihe Area in the northern Great Xing'an Range

The Central Asian Orogenic Belt (CAOB) is the largest accretionary orogenic belt in the world and its formation involved a complicated process of arc–continent collision. Large‐scale Mesozoic volcanic activity in the Great Xing'an Range (GXAR) in northeastern China, which constitutes part of the eastern CAOB, has received much recent research attention. However, the petrogenesis and formation mechanism of the late Mesozoic igneous rocks remain enigmatic. This paper investigates the geochronology, petrogenesis, and formation mechanism of late Mesozoic magmatic rocks in the Kelihe area of the GXAR based on zircon U–Pb dating, petrology, and geochemistry. Late Mesozoic magmatism in the Kelihe area occurred during the Late Jurassic (165–155 Ma) and Early Cretaceous (130–120 Ma). These igneous rocks generated by this magmatism are characterized by high SiO2 (69.97–75.49 wt%) and low MgO (0.11–0.68 wt%), Cr (10–30 ppm), Co (0.2–2.6 ppm), and Ni (0.5–1.6 ppm) contents. Trace elements show enrichment in Rb, Th, U, Zr, and K, and depletion in Ba, P, Nb, and Ti. These features indicate that the rocks were derived from partial melting of the crust. Furthermore, the rhyolites have high Na2O (5.02–5.44 wt%) and K2O (3.94–4.88 wt%) contents, similar to those of melts formed by the partial melting of basaltic crust. Combining the present results with the findings of previous studies, it is inferred that the Mesozoic igneous rocks formed in a post‐collisional extensional setting related to lithospheric thinning and asthenospheric upwelling after the closure of the Mongol–Okhotsk Ocean.

Products of an Early Cretaceous extensional mechanism in the central Great Xing'an Range: Felsic plutons in the Zhalantun area and their parental magma compositions and diagenetic processes

Late Mesozoic extensional mechanisms in the Great Xing'an Range (GXR) and relevant crust–mantle interactions are complicated, which result in widespread magmatisms with diverse parental origins and petrogenesises. In this paper, we present the lithology, whole‐rock geochemistry, and zircon U–Pb–Lu–Hf isotopes for granodiorite‐monzogranite rocks (GM) and their enclaves of quartz monzodiorites in the Zhalantun area, east of central GXR. Zircon U–Pb dating results reveal that both GM rocks and their enclaves of quartz monzodiorites yield a nearly identical crystallization age of ~125 Ma. The GM rocks exhibit weak peraluminous and high‐K calc‐alkaline compositions with high SiO2, Na2O + K2O, and Al2O3 contents, and low MgO, Mg#, Fe2O3T, and TiO2 contents, which are characterized by fractionated REE patterns, relatively strong negative Eu anomalies, enrichments of LILEs (e.g., Rb, Ba, and K), and depletions of Nb, Ta, P, and Ti. The parental origins for GM samples were juvenile crustal materials, with positive zircon εHf(t) values of +2.5 to +12.9. The whole‐rock and zircon geochemical simulations limit slightly lower GM magma crystallization temperatures (TTi‐Zrn) of 683–824°C and relatively more oxidizing conditions (log(fO2) = FMQ+7.6–FMQ‐6.8), and further confine that they were probably formed by ~10–35% degrees of fluid‐present partial melting of lower to middle crustal materials, with fractional crystallization and/or residual mineral phases of plagioclase, amphibole, clinopyroxene, and garnet. By contrast, the enclaves of quartz monzodiorites possess lower SiO2 and Na2O + K2O compositions, but higher MgO, Mg#, Fe2O3T, and TiO2 values, which are consistent with metaluminous–weak peraluminous and high‐K calc‐alkaline series. All quartz monzodiorites exhibit sub‐parallel right‐declined REE patterns, negligible to none Eu anomalies, enrichments of LILEs, and depletions of Nb, Ta, and Ti. Combined with mineral morphology and disequilibrium structures, the whole‐rock geochemical and Hf isotopic simulations imply that parental magmas for quartz monzodiorites were hybrid mixtures between ~50% host GM acid magmas and ~50% ancient crust compositions, with a wide range of zircon εHf(t) of +14.0 to −7.7, slightly higher TTi‐Zrn of 710–835°C, and lower log(fO2) of FMQ+8.2–FMQ‐10.5. Taken together, felsic plutons in the Zhalantun area correspond to an episode of extensional mechanism‐related crust–mantle interactions, which might be induced by either the Mongol‐Okhotsk domain or Palaeo‐Pacific tectonic domain, or both of them.

Early Cretaceous crust–mantle interaction linked to rollback of the Palaeo-Pacific flat-subducting slab: constraints from the intermediate–felsic volcanic rocks of the northern Great Xing’an Range, NE China

AbstractLate Mesozoic igneous rocks are important for deciphering the Mesozoic tectonic setting of NE China. In this paper, we present whole-rock geochemical data, zircon U–Pb ages and Lu–Hf isotope data for Early Cretaceous volcanic rocks from the Tulihe area of the northern Great Xing’an Range (GXR), with the aim of evaluating the petrogenesis and genetic relationships of these rocks, inferring crust–mantle interactions and better constraining extension-related geodynamic processes in the GXR. Zircon U–Pb ages indicate that the rhyolites and trachytic volcanic rocks formed during late Early Cretaceous time (c. 130–126 Ma). Geochemically, the highly fractionated I-type rhyolites exhibit high-K calc-alkaline, metaluminous to weakly peraluminous characteristics. They are enriched in light rare earth elements (LREEs) and large-ion lithophile elements (LILEs) but depleted in high-field-strength elements (HFSEs), with their magmatic zircons ϵHf(t) values ranging from +4.1 to +9.0. These features suggest that the rhyolites were derived from the partial melting of a dominantly juvenile, K-rich basaltic lower crust. The trachytic volcanic rocks are high-K calc-alkaline series and exhibit metaluminous characteristics. They have a wide range of zircon ϵHf(t) values (−17.8 to +12.9), indicating that these trachytic volcanic rocks originated from a dominantly lithospheric-mantle source with the involvement of asthenospheric mantle materials, and subsequently underwent extensive assimilation and fractional crystallization processes. Combining our results and the spatiotemporal migration of the late Early Cretaceous magmatic events, we propose that intense Early Cretaceous crust–mantle interaction took place within the northern GXR, and possibly the whole of NE China, and that it was related to the upwelling of asthenospheric mantle induced by rollback of the Palaeo-Pacific flat-subducting slab.

The granite porphyry hidden in the Shuangjianzishan deposit, southern Great Xing’an Range, NE China: geochronology, isotope geochemistry and tectonic implications

AbstractThe Shuangjianzishan vein-type Ag-Pb-Zn deposit in the southern Great Xing’an Range (GXR), NE China, is hosted in the slate of the Lower Permian Dashizhai Formation intruded by granite porphyry. In this paper, U–Pb zircon ages and bulk-rock and isotope (Sr, Nd, Pb and Hf) compositions are reported to investigate the derivation, evolution and geodynamic setting of this granite porphyry. It is closely associated with Pb-Zn-Ag mineralization in the southern GXR and contains important geological information relating to regional tectonic evolution. Laser ablation – inductively coupled plasma – mass spectrometry (LA-ICP-MS) zircon U–Pb dating yields an emplacement age of 131 ± 1 Ma for the granite porphyry. Bulk-rock analyses show that the Shuangjianzishan granite porphyry is characterized by high Si, Na and K contents but low Mg and Fe contents, and that the enrichment of Zr, Y and Ga suggests an A-type granite affinity. Most of the studied samples have relatively low 87Sr/86Sr values (0.70549–0.70558), with positive ϵNd(t) (0.71–0.88) and ϵHf(t) (4.9–6.9) values. The Sr–Nd isotope modelling results, in combination with the young TDM2 ages of Nd and Hf (850–864 and 668–778 Ma, respectively), reveal that the Shuangjianzishan granite porphyry may be derived from the melting of mantle-derived juvenile component, with minor lower crustal components; this finding is also supported by Pb isotopic compositions. Considering the widespread presence of granitoids with coeval volcanic rocks and regional geology data, we propose that the Shuangjianzishan granite porphyry formed in a post-orogenic extensional environment related to the upwelling of asthenospheric mantle following the closure of the Mongol–Okhotsk Ocean.

Late Mesozoic magmatism at Xiaokelehe Cu[sbnd]Mo deposit in Great Xing'an Range, NE China: Geodynamic and metallogenic implications

Multiphase Late Mesozoic magmatism is clearly recorded at the Xiaokelehe porphyry CuMo deposit in NE China, including the syn-ore granodiorite porphyry, and post-ore diorite, gabbro, monzonite (porphyry), and granite porphyry. In this study, we present new geological, LA-ICP-MS zircon UPb geochronological and geochemical data on these intrusive units to unravel the tectonic evolution of the Late Mesozoic Great Xing'an Range (GXR). Zircon UPb dating indicates that the multiphase magmatism extended from the Late Jurassic to Early Cretaceous, i.e., 149.4 ± 4.0 Ma (diorite), 148.9 ± 1.4 Ma (granodiorite porphyry), 146.9 ± 4.1 Ma (monzonite), 140.6 ± 3.8 Ma (gabbro), and 139.9 ± 4.3 Ma (monzonite porphyry).Geochemical data indicate that the syn-ore granodiorite porphyry is adakie-like, featured by relatively LILE-enrichments (Rb, Ba, K, Pb, LREEs), high Sr contents (1065–1130 ppm), and elevated Sr/Y (129.9–171.8) and (La/Yb)N (35.12–47.07) ratios, but with HFSE-depletions (Nb, Ta, Ti, HREEs), low Y (6.2–8.7 ppm) and Yb (0.48–0.67) contents. The granodiorite porphyry has relatively higher Mg# values (41–47), depletion of Nb and Ta, low Cr (29.0–31.0 ppm) and Ni contents (9.4–12.6 ppm), as well as enriched SrNd isotope features, indicating that the granodiorite porphyry was derived from an enriched mantle (garnet-bearing) refertilized by subduction-related melts in a post-collision setting, and the magmas were subsequently fractionated during their ascent. The diorite and gabbro may have also derived from the refertilized lithospheric mantle (but without garnet), whereas the monzonite and its porphyry were derived from the lower crust at >40 and < 40 km depths, respectively. Meanwhile, fractionation and crustal assimilation have been important for the diorite, gabbro, and monzonite (porphyry) formation. Combined our study with published ones, we concluded that: (1) the Mongol-Okhotsk Ocean was finally closed in the GXR before the Late Jurassic; and (2) Late Mesozoic magmatism and porphyry CuMo mineralization in the GXR likely occurred in the compressive-to-extensional transition after the collision between the Mongol-SinoKorea and Siberia plates.