Great Hinggan Range Research Articles

Geochemistry and Sr‐Nd‐Pb Isotopes of the Granites from the Hashitu Mo Deposit of Inner Mongolia, China: Constraints on Their Origin and Tectonic Setting

AbstractThe Hashitu molybdenum deposit is located in the southern part of the Great Hinggan Range, NE China. Molybdenum mineralization is hosted by and genetically associated with monzogranite and porphyritic syenogranite. Sr‐Nd‐Pb isotopes of the intrusions show that the porphyritic syenogranite has initial 87Sr/86Sr ratios of 0.70418–0.70952, εNd(t) values of 1.3 to 2.1 (t=143 Ma), 206Pb/204Pb ratios of 19.191–19.573, 207Pb/204Pb ratios of 15.551–15.572, and 208Pb/204Pb ratios of 38.826–39.143. The monzogranite has initial 87Sr/86Sr ratios of 0.70293–0.71305, εNd(t) values of 1.1 to 2.0 (t=147 Ma), 206Pb/204Pb ratios of 19.507–20.075, 207Pb/204Pb ratios of 15.564–15.596, and 208Pb/204Pb ratios of 39.012–39.599. The calculated Nd model ages (TDM) for monzogranite and porphyritic syenogranite range from 866 to 1121 Ma and 795 to 1020 Ma, respectively. The granitic rocks in the Hashitu area have the same isotope range as granites in the southern parts of the Great Hinggan Range. The isotope composition indicates that these granites are derived from the partial melting of a juvenile lower crust originating from a depleted mantle with minor contamination by ancient continental crust. The integrating our results with published data and the Late Mesozoic regional tectonic setting of the region suggest that the granites in the Hashitu area formed in an intra‐continent extensional setting, and they are related to the thinning of the thickened lithosphere and upwelling of the asthenosphere.

Geochemistry, zircon U–Pb and molybdenite Re–Os dating of the Taolaituo porphyry Mo deposit in the Central Great Hinggan Range: implications for the geodynamic evolution of northeastern China

AbstractThe Taolaituo porphyry‐type molybdenum deposit is located in the eastern Inner Mongolia Autonomous Region in China. The mineralization occurs mainly as veins, lenses and layers within the host porphyry. To better understand the link between the mineralization and the host igneous rocks, we studied samples from the underground workings and report new SHRIMP II zircon U–Pb and Re–Os molybdenite ages, and geochemical data from both the molybdenites and the porphyry granites. Five molybdenite samples yield a Re–Os isochron weighted mean age of 133.0 ± 0.82 Ma, whereas the porphyry granitoids samples yield crystallization ages of 133 ± 1 Ma and 130.4 ± 1.3 Ma. The U–Pb and Re–Os ages are similar, suggesting that the mineralization is genetically related to the Early Cretaceous porphyry emplacement. Re contents of the molybdenites range from 21.74 to 42.45 ppm, with an average of 32.69 ppm, whereas δ34S values vary between 3.7‰ and 4.2‰, which is typical of mantle sulphur. The 206Pb/204Pb, 207Pb/ 204Pb and 208Pb/204Pb vary in the ranges of 18.276–18.385, 15.566–15.580 and 38.321–38.382, respectively. The Taolaituo Early Cretaceous granitoids are A‐type granites. These observations indicate that the molybdenites and the porphyry granites were derived from a mixed source involving young accretionary materials and enriched subcontinental lithospheric mantle. A synthesis of geochronological and geological data reveals that porphyry emplacement and Mo mineralization in the Taolaituo deposit occurred contemporaneously with the Early Cretaceous tectonothermal events associated with lithospheric thinning, which was caused by delamination and subsequent upwelling of the asthenosphere associated with intra‐continental extension in northeast China. Copyright © 2015 John Wiley & Sons, Ltd.

The Gaosongshan epithermal gold deposit in the Lesser Hinggan Range of the Heilongjiang Province, NE China: Implications for Early Cretaceous mineralization

The newly discovered and large ca. 99Ma Gaosongshan gold deposit is located in the Lesser Hinggan (or Xinggan) Range to the west of the Jiamusi Massif. The deposit is located at the border of the Great Hinggan Range–Mongolian Orogen with the Circum-Pacific tectonic belt and has a resource of ~22t @ 6.3g/t Au. Gaosongshan is classified as an adularia–sericite epithermal deposit associated with the large tensional Shaqihe Fault and has a low-sulfide content with a high concentration of gold hosted by pure chalcedonic quartz, which makes the deposit both unique and economically important in the area. Early Cretaceous volcanic rocks host the deposit as well as other gold deposits in the region. The mineralization at Gaosongshan includes Au, Ag, Mo, Sb, As, Pb and Hg. Stable isotope studies of fluid inclusions associated with the mineralization suggest that the mineralizing fluid had a meteoric origin (DV-SMOW: −129 to −111‰; 18Ofluid: 7.9 to 13.8‰). Fluid inclusion thermography indicates that the mineralized fluid was between 150° and 310°C and had a low salinity (0.7–3.71wt.% NaCl), low density (0.48–0.94g/cm3), shallow metallogenic depth (430–1270m), and a large amount of reducing gaseous components (CH4, C2H6, CO, N2, and CO2). The presence of large quantities of flaky quartz, adularia, gas-rich fluid inclusions, low-sulfide minerals and pure gold-bearing chalcedonic quartz suggests that fluid boiling was the principal mechanism for the gold precipitation. Sulfur isotopic data (δ34S: ~ −2.4 to 2.9‰) indicate a deep magmatic origin for the mineralization, and the Pb isotopes (206Pb/204Pb: 18.14–18.46; 207Pb/204Pb: 15.51–15.57; 208Pb/204Pb: 38.01–38.40) also indicate that the metallogenic source of the deposit contained a significant mantle component. The mineralizing fluid interacted with a Late Paleozoic (ca. 260–253Ma) substrate and ca. 141–91Ma volcanic host rocks. The geological and geochemical characteristics of the deposit, and the Tuanjiegou, Dongan, Sandaowanzi and other large gold deposits represent an Early Cretaceous (114–80Ma) epithermal mineralizing events in the Lesser Hinggan Range. The belt is controlled by the volcanic Sunwu–Jiayin Basin formed in a back-arc extensional setting along an active continental margin in East China, and the gold deposits in the belt have the same genesis as porphyritic Au(–Cu) deposits along the continental margin in eastern Jilin and Heilongjiang provinces. It is here proposed that the mineralization in both regions is related to the subduction of the Paleo-Pacific plate.

Gold-telluride-sulfide association in the Sandaowanzi epithermal Au-Ag-Te deposit, NE China: implications for phase equilibrium and physicochemical conditions

The Sandaowanzi gold-telluride deposit, with a total reserve of ≥ 25 t of Au and an average grade of 15 g/t, is located in the Great Hinggan Range Metallogenic Belt in NE China. This deposit is the first reported case of a dominantly Au (±Ag)-telluride deposit in this area and it reveals highly economic bonanza Au- and Ag-telluride ores. Ore bodies principally occur in quartz veins and stockworks and minor in disseminations hosted by trachyandesites and andesitic breccias. Four paragenetic stages of mineralization are identified, demonstrating an early deposition of sulfides and subsequent precipitation of tellurides, which are mainly composed by petzite, sylvanite and to a lesser extent, hessite, calaverite, altaite, unnamed telluride (Au1.8Ag0.2Te), krennerite, empressite, stutzite and coloradoite. Abundant telluride assemblages identified from Sandaowanzi ores are mostly attributed to breakdown of early tellurium-bearing phases (i.e., γ- and χ-phases) during cooling. The deposition of substantial Au-Ag-Te minerals are constructed under physicochemical conditions of T = 240 to 280 °C, pH = 4.39 to 5.64, logfO2 =–44.8 to –41.8, logfTe2 =–9.75 to –9.43, logαAu+(aq)/αAg+(aq) = −6.87 to –6.56, and gold is mostly scavenged from a HTe−-dominant ore-forming fluid. The unusually high Te concentrations in the Sandaowanzi epithermal system are likely attributed to alkaline to calc-alkaline magmatic degassing.

Geology, geochemistry and tectonic setting of the Indosinian Mo deposits in southern Great Hinggan Range, NE China

The southern Great Hinggan Range in northeast China, mainly bounded by the Kangbao–Chifeng Fault to the south and the Hegenshan–Heihe Suture to the north, is a Palaeozoic subduction‐related accretionary belt added to the northern margin of the North China Craton. The area has been considered as a Yanshanian metallogenic province, with more than 20 Mo deposits being discovered. Recently, six of the Mo deposits were proven to have formed during the Indosinian (Triassic) Orogeny, indicating the significance of the Indosinian mineralization, orogeny and magmatism. In this contribution, we summarize available data of the Indosinian Mo deposits, and show that Triassic Mo mineralization occurred in the time range of 248–232 Ma, coincident with a regional granitic event, and was presented as porphyry and intrusion‐related quartz vein systems. The Indosinian ore‐related granitoids show geochemical features of high‐K calc‐alkaline metaluminous–peraluminous and adakitic rocks, and have been formed by partial melting of thickened lower crust in a post‐subduction tectonic setting. Rhenium contents of molybdenite crystals and sulphur–lead isotopic compositions indicate that the ore‐forming materials originated from continental crust with some mantle components involved. Copyright © 2014 John Wiley & Sons, Ltd.

S–Pb isotopic geochemistry, U–Pb and Re–Os geochronology of the Huanggangliang Fe–Sn deposit, Inner Mongolia, NE China

The Huanggangliang Fe–Sn deposit is located in the eastern section of the Central Asian Orogenic Belt (CAOB) and in the southern segment of the Great Hinggan Range polymetallic belt. This deposit is the largest tin-based polymetallic ore deposit in the northern part of the North China plate. The Fe–Sn mineralization principally occurs in skarn zones, which formed in the contact areas between granite intrusions and marbles. Twenty-one δ34SV-PDB values for sulfides from the Huanggangliang Fe–Sn deposit range from −2.3 to +2.7‰, with an average of +0.38‰, and these values are interpreted to reflect a deep magmatic source of the sulfur contained within the ore minerals of the deposit. The distribution of lead isotopic compositions from sulfides in the Huanggangliang Fe–Sn deposit exhibits a generally concentrated field, indicating that those sulfides have homogeneous lead isotopes and may derive from the same metallic source. The existence of such identical Pb isotopic compositions of sulfides and host granites suggests that granitic magmatism was probably largely responsible for the Huanggangliang mineralization.Zircon LA-ICP-MS U–Pb dating from the Huanggangliang granite exhibits a tight cluster on the Concordia plot and yields a weighted mean 206Pb/238U age of 139.96±0.87Ma, which is considered to be the best estimate of the crystallization age of the Huanggangliang granite. Results obtained from the molybdenite Re–Os isotopic analysis indicate Re–Os model ages of 133.6 to 141.5Ma and a weighted mean age of 135.1±2.3Ma. The molybdenite Re–Os dating yields an isochron age of 134.9±5.2Ma and an initial 187Os/188Os ratio of −0.22±0.35. The molybdenite Re–Os isochron age is largely consistent with the zircon U–Pb age, indicating that both granite intrusion and Fe–Sn mineralization were associated with the Mesozoic magmatism in NE China.Based on ore deposit geology, isotope geochemistry and geochronology of the Huanggangliang Fe–Sn deposit and regional geodynamic evolution, the formation of this deposit is believed to be related to lithospheric thinning, which was caused by delamination and subsequent upwelling of the asthenosphere under the intra-continental extension in NE China. The dynamic setting for the geological processes should be linked to the NNW subduction of the Izanagi plate beneath the Eurasian plate during the Mesozoic. This subduction triggered intensive magmatism and mineralization events in the Great Hinggan Range of NE China, making this district an important Cu–Mo–Sn–Fe–Ag–Pb–Zn metallogenic province.

Zircon U–Pb and molybdenite Re–Os geochronology, and whole-rock geochemistry of the Hashitu molybdenum deposit and host granitoids, Inner Mongolia, NE China

The Hashitu deposit is a newly-discovered Mo deposit in the southern part of the Great Hinggan Range, NE China. Molybdenum mineralization occurs as quartz-sulfide veins within the Hashitu granite-porphyry composite pluton. The sulfide assemblage in the veins is dominated by molybdenite, with minor amounts of galena, sphalerite, chalcopyrite, pyrite and marcasite. The associated gangue minerals are quartz, fluorite, calcite, sericite, chlorite and epidote. Whole-rock chemical compositions show that the Hashitu granites belong to the A2-type. The U–Pb ages of zircons from the Hashitu granite and porphyry units are 147±1Ma and 143±2Ma, respectively. The Re–Os isochron age of molybdenites from the deposit is 150±4Ma. The molybdenite Re–Os model ages vary from 144 to 150Ma, with a weighted mean of 147±1Ma. The results show that the ages of zircon crystallization and Mo mineralization are similar, mostly within analytical uncertainties, and that the host granite pluton is one of many late-Jurassic plutons in the Great Hinggan Range. The formation of the late-Jurassic granitic plutons in this region coincides with the subduction of the Pacific plate beneath the North China block which took place ∼2000km to the east at the time. The occurrence of abundant late-Jurassic granitoids with compositions similar to the Hashitu pluton in the Great Hinggan Range is a positive sign for more discoveries of Mo deposits in this region.

Geochronology and isotopic geochemistry of the A-type granites from the Huanggang Sn–Fe deposit, southern Great Hinggan Range, NE China: Implication for their origin and tectonic setting

The Huanggang Sn–Fe deposit, Inner Mongolia, is located in southern Great Hinggan Range metallogenic belt. LA-ICP-MS zircon U–Pb dating show that the K-feldspar granite and granite-porphyry in the Huanggang mine were formed at 136.7±1.1Ma and 136.8±0.57Ma, respectively. Sr–Nd–Pb isotope of the rocks and In situ zircon Hf isotopic systematics show that (87Sr/86Sr)i values range from 0.70211 to 0.70729, close to the (87Sr/86Sr)i of oceanic basalts and lower than those of continental crust. The εNd(t) values and Nd model ages (TDM) vary from −0.8 to 0.9 and 855 to 993Ma, respectively. The Pb isotopic compositions are also variable with 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb values of 18.974–26.107, 15.554–15.914 and 38.894–39.890, respectively, suggesting that the lead is derived from a mixed source. The 176Hf/177Hf values range from 0.282744 to 0.282922, with corresponding εHf(t) values ranging from 1.9 to 18.3, and two-stage Hf model ages (TDM2) of between 561 and 888Ma. The isotope composition shows that Huanggang granites were derived from partial melting of juvenile lower crust that originated from depleted mantle, perhaps contaminated by small amounts of ancient continental crust. Younger Nd, Hf isotope model ages imply that an important crustal growth event took place in this area during the Neoproterozoic. Integrating our data with previously published results and the Late Mesozoic regional tectonic setting, we conclude that the Huanggang granites were generated in an intraplate tectonic–magmatic setting. Asthenospheric mantle upwelling due to lithospheric delamination and magma underplating, caused the partial melting of a mantle wedge metasomatized by the fluids released from subducted oceanic crust or by decompression of depleted mantle. This resulted in remelting, differentiation and a continued evolution of the mafic juvenile crust, producing a large quantity of granitic magma. The tectonic setting for these processes may be linked to the NNW subduction of the Pacific plate (Izanagi) in the Mesozoic, which affected most of eastern China.

Zircon U–Pb ages of the metamorphic supracrustal rocks of the Xinghuadukou Group and granitic complexes in the Argun massif of the northern Great Hinggan Range, NE China, and their tectonic implications

The basement of the Argun massif in the northern Great Hinggan Range consists of the metamorphic supracrustal rocks of the Xinghuadukou Group and associated granitic complexes. The metamorphic supracrustal rocks were previously interpreted as Paleoproterozoic, while the granitic complexes were considered Mesoproterozoic in age. This paper presents new zircon LA-MC-ICP-MS U–Pb ages of biotite-plagioclase leptynite and biotite schist from the Xinghuadukou Group in the Lulin Forest area, Heilongjiang Province; zircon SHRIMP U–Pb ages of biotite-plagioclase gneiss from the Xinghuadukou Group in Lulin Forest; and quartz diorite and monzogranite from the granitic complexes in Mohe County, Heilongjiang Province. New geochronological data from the three metasedimentary rock samples of the Xinghuadukou Group can be preliminarily divided into five groups: (1) 2017–2765Ma, (2) 1736–1942Ma, (3) 1359–1610Ma, (4) 749–1239Ma, and (5) 448–716Ma. Except for the zircons of the 448–716Ma group belonging to a metamorphic origin, the other age groups had the youngest age of 749±17Ma, indicating that the Xinghuadukou Group formed during the Neoproterozoic era (at least <749Ma). These detrital zircon ages cluster at ca. 2.0–1.8Ga and ca. 1.0–0.80Ga, suggesting that the Argun massif had connections with both Columbia and Rodinia and implying that the provenance of the Xinghuadukou Group metamorphosed sediments must be characteristic of felsic–intermediate igneous rocks with ages of ca. 2.0–1.8Ga and ca. 1.0–0.80Ga. The quartz diorite and monzogranite from the granitic complexes of the basement within the Argun massif yielded weighted mean ages of 516±10Ma and 504±9Ma, respectively, indicating that these rocks emplaced in the Early Paleozoic. Considering the geochemical and chronological data together, we propose that the Xinghuadukou Group was most likely deposited in a back-arc basin environment, whereas the granitic complexes emplaced in a post-collisional setting. A wide age spectrum of detrital zircons ranging from 749±9 to 2765±11Ma with ages clustering approximately 2.0–1.8Ga and 1.0–0.80Ga suggests that the basement rocks of the Argun massif are chiefly composed of the Neoproterozoic metasedimentary sequence and Early Paleozoic granitic complexes, with a few Meso- to Paleoproterozoic and even Neoarchean metamorphic rocks.

Geochemistry and Genesis of the Late Jurassic Granitoids at Northern Great Hinggan Range: Implications for Exploration

Abstract:The Longgouhe and Ershiyizhan intrusions of the Late Jurassic, located in the Upper Heilongjiang Basin of the northern Great Hinggan Range, are closely related to porphyry Cu‐Au mineralizations. In lithology the intrusions are quartz diorite, quartz monzodiorite and granodiorite of high‐K calc‐alkaline series, with minor aspects of shoshonite series. Their SiO2 and Al2O3 contents range from 61.37% to 66.59% and 15.35% to 17.06%, respectively. The MgO content ranges from 2.02% to 3.47%, with Mg# indices of 44–59. The (La/Yb)N and Eu/Eu* values range from 16.85 to 81.73 and 0.68 to 0.93, respectively, showing strong differentiation rare earth element (REE) patterns similar to those of adakites. The rocks are enriched in Ba, Sr and light REE (LREE), obviously depleted in Nb and Ta, slightly depleted in Rb and Ti, and poor in Yb and Y, with Yb and Y contents of 0.31–1.32 ppm and 4.32–12.07 ppm, respectively. As indicated by Sr/Y ratios of 67.74–220.60, the rocks are characterized by low‐Y and high‐Sr contents, which characterize the adakites in the world. Holistically, geochemical tracers suggest that the interested intrusions are adakitic rocks. Given that the Paleo‐Asian Ocean and Mongol‐Okhotsk Ocean were closed in the Late Paleozoic and Permian‐Middle Jurassic, respectively, the interested intrusions should be formed by partial melting of delaminated crust, which had been thickened during collisional orogeny between the Siberian and Mongolian‐Sinokorean continents.