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Zhou L.-L.,CAS Institute of Geology and Geophysics | Zhou L.-L.,University of Aarhus | Zeng Q.-D.,CAS Institute of Geology and Geophysics | Liu J.-M.,CAS Institute of Geology and Geophysics | And 4 more authors.
Journal of Asian Earth Sciences | Year: 2014

The Daheishan giant porphyry Mo deposit is located at the eastern segment of the CAOB, NE China. The ore-bearing intrusion of Daheishan deposit is a Jurassic granitic complex that includes Changgangling biotite granodiorite, Qiancuoluo seriate granodiorite, and Qiancuoluo granodioritic porphyry. Mineralization consists of disseminated, breccia and veined types. The hydrothermal fluids show significant magmatic signatures, as evidenced by the hydrogen and oxygen isotopic compositions of quartz and sulfur isotopic characteristics of ores. Consistence of lead isotopic compositions of the sulfides and the Daheishan intrusive complex further indicate a close relationship between the mineralization and magma. The fluid inclusions in quartz comprise of predominant aqueous two-phase as well as gas-rich fluid inclusions and a small number of daughter mineral-bearing inclusions. The gas species in the fluid inclusions are H2O, CO2, N2, CH4, C2H6, Ar* and minor H2S; the liquid compositions are SO4 2 -, Cl-, Na+, K+, Ca2+ and Mg2+. Raman spectroscopy on individual fluid inclusions reveals a main gaseous composition of H2O, minor H2S and CO2. The fluid system in Daheishan Mo deposit can be described as NaCl-KCl-H2O type. Fluid inclusion microthermometry reveals subsolidus homogenization temperatures for fluid inclusions in the magmatic quartz phenocrysts (T h =400-450°C, salinities=∼21eq. wt.%), suggesting an obliteration of higher temperature history of the porphyry system by the superimposed processes. Most of the mineralization occurred at temperature range of 220-360°C, or higher. The temperature and salinity decreased to 100-170°C and 0-15eq. wt.%, respectively, when the hydrothermal fluid activities were gradually ending. No distinct evolution pattern based on the homogenization temperature or stable isotopic analyses is observed among the different mineralization stages. Mineralization was supposed to be related to the multi-phased boiling of fluids, instead of the gradual cooling of fluids. Pressure may be more critical than temperature in controlling the precipitation of molybdenite. © 2014 Elsevier Ltd.

Zhou L.-L.,CAS Institute of Geology and Geophysics | Zhou L.-L.,University of Aarhus | Zeng Q.-D.,CAS Institute of Geology and Geophysics | Liu J.-M.,CAS Institute of Geology and Geophysics | And 4 more authors.
International Geology Review | Year: 2014

Daheishan giant porphyry Mo deposit is located in the Lesser Xingan-Zhangguangcai Ranges, Jilin Province, NE China. Mineralization is closely related to the Daheishan intrusive complex, which can be divided into Changganglin biotite granodiorite, Qiancuoluo biotite granodiorite, and Qiancuoluo granodioritic porphyry. Four stages of mineralization are distinguished, based on the cross-cutting relationships of mineralized veins. LA-ICPMS zircon U-Pb analysis yields 206Pb/238U ages of 177.9 ± 2.3 Ma for the Changganglin biotite granodiorite, 169.9 ± 2.3 Ma for the Qiancuoluo biotite granodiorite, and 166.6 ± 4.0 Ma for the Qiancuoluo granodioritic porphyry. Hydrothermal fluids responsible for mineralization evolved from different magmas. Six molybdenite samples yield Re-Os model ages of ~167 Ma. Muscovite from the last mineralization stage gives a 40Ar/39Ar plateau age of 163.6 ± 0.9 Ma. Geochronology data indicate that the entire magmatic system lasted for about 10 million years, and the total duration of hydrothermal activity was less than 4 million years. The εHf(t) values of zircons obtained from the Changganglin biotite granodiorite, Qiancuoluo biotite granodiorite, and Qiancuoluo granodioritic porphyry range from 4.5 to 9.1, 5.7 to 10.9, and 4.4 to 7.1, respectively, indicating that they were mainly derived from the depleted mantle, although contaminated by crustal materials to a greater or lesser extent. The formation of the Daheishan porphyry Mo deposit was temporally and spatially related to the amalgamation of Jiamusi Massif and Songliao terrane in the Palaeo-Pacific Ocean regime. Regional Hf isotopic compositions of zircon suggest an episode of crustal growth in the Phanerozoic in the Lesser Xingan-Zhangguangcai Ranges. Regional Mo mineralization ages suggest a peak of porphyry Mo mineralization in the Jurassic in the Lesser Xingan-Zhangguangcai Ranges. © 2014 Taylor & Francis.

Duan X.-X.,CAS Institute of Geology and Geophysics | Duan X.-X.,University of Chinese Academy of Sciences | Zeng Q.-D.,CAS Institute of Geology and Geophysics | Yang Y.-H.,CAS Institute of Geology and Geophysics | And 4 more authors.
International Geology Review | Year: 2015

The Laojiagou Mo deposit is a newly discovered porphyry Mo deposit located in the Xilamulun Mo metallogenic belt, Northeast China. Mo mineralization mainly occurred within the monzogranite and monzogranite porphyry. Re-Os isochron dating of molybdenites indicate a mineralization age of 234.9 ± 3.1 Ma. Zircon LA-ICP-MS U-Pb analysis for monzogranite porphyry and monzogranite yield 206Pb/238U ages of 238.6 ± 1.8 and 241.3 ± 1.5 Ma, respectively, indicating that Laojiagou Mo mineralization is related to Middle Triassic magmatism. Hf isotopic compositions of zircons from both monzogranite porphyry and monzogranite are characterized by positive εHf(t) values [εHf(t) = 2.9-7.3 and 1.5-7.9, respectively] and young TDM2 model ages, which implies that the magma was derived from juvenile crust created during accretion of the Central Asian Orogenic Belt (CAOB). Identification of the Laojiagou Mo deposit adds another important example of Triassic Mo mineralization in the Xilamulun Mo metallogenic belt where most Triassic Mo deposits in northeast China cluster around the northern margin of North China Craton. Based on the regional geological setting and geochronological and Hf isotope characteristics, we propose that Triassic Mo deposits and related magmatic rocks in northeast China formed during the last stages of evolution of the CAOB. These deposits formed during post-collisional extension after the closure of the Palaeo-Asian Ocean and amalgamation of the North China-Mongolian Block with the Siberian Craton. © 2014 Taylor & Francis.

Duan X.X.,CAS Institute of Geology and Geophysics | Duan X.X.,University of Chinese Academy of Sciences | Liu J.M.,CAS Institute of Geology and Geophysics | Wang Y.B.,CAS Institute of Geology and Geophysics | And 8 more authors.
Acta Petrologica Sinica | Year: 2012

The Qingchengzi orefield which lies in geotectogene of Liaodong rift is an important polymetallie mineral district in northern China for its clustering several large Pb-Zn, Ag and Au deposits. A phase of Late Triassic magmalism, represented by Shuangdinggou biotite monzogranite and Xinling granite, is intimately related to polymetallie mineralization. LA-ICPMS zircon U-Pb age of 224.2 ± 1.2Ma was obtained for the Shuangdinggou intrusion. Geochemical data for the Shuangdinggou intrusion reveal SiO 2 content of 69.07% ∼71.31%, while K 2O accounts for 3.53% ∼5.22% and Na 2O for 3.87% ∼4.14%, indicating it belongs to high K calc-alkaline series. Al 2O 3 content ranges between 12.46% ∼ 14.48% and A/CNK < 1 suggest metaluminous feature. Trace element geochemistry of the biotite monzogranite displays high total REE content and demonstrate strong fractionation between light and heavy REE elements [ ( La/Yb) N = 35.43 ∼ 79.01, LREE/HREE = 23.09 ∼ 35.10 ] and minor negative Eu anomalies ( δEu = 0.68 ∼0.97). The biotite monzogranite also shows LILE (such as Rb, Th, K, Pb) enrichment and HESE (including Nb, Ta, P, Ti) depletion, with unusual high Ba and Sr, low Y and Yb abundances manefesting adakitic geochemical signature. Based on above-stated petrological and geochemical data it is inferred that the biotite monzogranilic magma might be derived Irom the partial melting of a thickened lower crust with prominent garnet and rutile retained in the residual assemblages, and magma mixing is probably involved based on the unusually high Nb/Ta ratio (18.4∼21.2). It is suggested that slab break-off during the process of Yangtze Craton and North China Craton continental deep subduction in Late Triassic may be responsible for the ore-related magmatism.

Zhang Z.L.,China Railway Resources Exploration Co. | Zhang Z.L.,CAS Institute of Geology and Geophysics | Liu J.M.,CAS Institute of Geology and Geophysics | Chu S.X.,CAS Institute of Geology and Geophysics
Acta Petrologica Sinica | Year: 2012

The Yangchang Mo deposit is located in the Xilamulun molybdenum metallogenic belt on northern margin of North China Craton, Inner Mongolia. The mineralization is occurred within the NW- to NNW- trending faults and fractures hosted by the Yanshanian biotite monzogranite. The ore-forming hydrothennal process can be subdivided into four stages: quartz vein stage ( I ), quartz-pyrite stage ( II-1), quartz-pyrite-molybdenite-ehaleopyrite-galena- sphalerite stage ( II-2) and carbonate stage (III). Three types of fluid inclusions are observed in quartz crystals, i. e. liquid-rich ( VH2O < 50% ) inclusion, gas-rich ( VH2O =50% ∼90% ) inclusion and vapor inclusions. Homogenizalion temperatures of I, II-1, II-2 stages are 173 ∼ 280°C, 180∼467°C, 151 ∼ 366°C, respectively. From I stage to II-1 stage the temperatures become higher, suggesting the magmatic water was introduced into the mineralizing system. Salinities of I, II-1, II-2 stages are in the range of 4.03%∼10.61% NaCleqv, 2.07%∼10.36% NaCleqv, 2.41%∼9.98% NaCleqv, respectively. The composition of the hydrothennal fluids at different stages are mainly H2O ( >94.39mol% ), with minor CO2 N2, CH4, C2H6, Ar, H 2S, and Na+, HS-, Cl- ions. These suggest the Yangchang Mo deposit was formed in reduction condition and the ore-forming fluids were ot the NaCl-H2O ± CO2 system. Hydrogen and oxygen isotopes ol fluid inclusions in various mineralization stages are - 119.66‰ ∼-98.79‰ and -0.08‰ ∼1.90‰ respectively, indicating that the ore-forming fluids were the mixture of magmatic water and meteoric water. It is suggested that the mixing of different fluids with distinct natures might be responsible for the precipitation of molybdenite.

Liu Y.,China University of Geosciences | Yang L.,China University of Geosciences | Guo L.,China Railway Resources Exploration Co. | Li R.,China University of Geosciences | And 4 more authors.
Acta Petrologica Sinica | Year: 2014

The Dayingezhuang gold deposit, located in the central section of the Zhaoping Fault Zone, northwestern Jiaodong Peninsula, within the phyllic zone in the footwall of main fault. Wall-rock alteration is intense and has a variety of types that include potash feldspathization, silication, sericitization, pyritization, chloritization and carbonatation. Amongst these alterations, silication, sericitization and pyritization are considered more closely related with the gold mineralization. Based on the cutting relations of veins and paragenesis of ore minerals, we determined three major mineralization stages: gold-quartz-pyrite, gold (silver) -quartz-polymetallic sulfides, quartz-calcite-pyrite. Employing the decrepitation thermometry to the ore quartz, we identified three concentrated ranges: 330-510°C, 240-330°C and 240-330°C, which are corresponding with each of the mineralization stage above. The ore-forming fluids in the Dayingezhuang gold deposit are characterized by medium temperature and rich in CO2content, contain a small amount of volatile gases, such as CH4, C2H6and H2S. The scheme of NaCl-H2O-CO2and the high level content of C2H6existed in all of mineralization stages indicate that the ore-forming fluids mostly are the metamorphic water. Even though the gas-liquid content from different mineralization stages are similar with each other, we still observed certain rules along the ore-forming evolution. The trend of increasing N2content indicates that the ore-forming fluids system switch to an open system in the late stage, and atmospheric water began to take part in the ore-forming fluids. The high quantity of H2S in the early gold mineralization indicates that the gold possibly was migrated as Au-S complex. The climbing ratios of C1-/SO2- 4and Na+/K+show that the ore-forming system convert from the CO2-H2O-K2SO4into CO2-H2O-NaCl system with the evolving process. The concentration of Na+, C1-, K+and SO2- 4decreased from early stage to later stage indicates that the salinity of ore-fluid declined. The higher ratio of H2O/CO2in the later stage represents that the fluid boiling may occurred in the middle stage. Overall, we think that a variety of fluid processes, including change of fluid inclusion types and fluid boiling, have been suggested for gold precipitation.

Yang X.,China University of Geosciences | Mingqi W.,China University of Geosciences | Yuyan G.,China Railway Resources Exploration Co. | He Z.,China University of Geosciences
Geochemistry: Exploration, Environment, Analysis | Year: 2015

The ‘Metals in Soil Gas’ (MSG) survey has proven to be a useful tool for mineral exploration under exotic overburden. Tracing the source of these metals with Pb isotopes is helpful to understand the formation of MSG. Lead isotope ratios in MSG samples were determined by ICP-MS (Model HP4500); the Pb isotope ratios in loess, red soil, wall rocks and ores were measured following decomposition and separation using a VG-354 thermal ionization mass spectrometer (TIMS) for comparison. The results of the study of samples collected over the Jiaolongzhang base metal deposit show that the Pb isotope ratios of MSG background samples are markedly distinct from those ratios of any medium (loess, red soil layer, wall-rocks and ores) in the vicinity of the deposit. The Pb isotope ratios in the MSG anomalous samples (206Pb/204Pb = 18.34–18.56, 207Pb/204Pb = 15.622–15.809 and 208Pb/204Pb = 38.184–38.691) are totally different from those in the samples of background areas (206Pb/204Pb = 16.46–17.68, 207Pb/204Pb = 13.985–14.945 and 208Pb/204Pb = 34.199–36.884). The Pb isotope ratios of MSG anomalous samples scatter near the ratios of the mineralized wall-rocks (206Pb/204Pb = 18.554– 18.874, 207Pb/204Pb = 15.618–15.755 and 208Pb/204Pb = 38.629–39.126) and sulphides (206Pb/204Pb = 18.130–18.251, 207Pb/204Pb = 15.671–15.767 and 208Pb/204Pb = 38.350–38.582). It can be concluded that some of the Pb in MSG anomalous samples originates from deep sulphide mineralization and Pb isotope ratios of MSG anomalous samples indicate that an MSG survey can detect the deeply concealed mineral deposits under exotic cover. © 2014 AAG/The Geological Society of London.

Yang M.,China University of Petroleum - Beijing | Li L.,Sinopec | Zhou J.,Bureau of Mineral Resources | Jia H.,Sinopec | And 3 more authors.
Acta Geologica Sinica | Year: 2015

The hydrocarbon potential of the Hangjinqi area in the northern Ordos Basin is not well known, compared to the other areas of the basin, despite its substantial petroleum system. Restoration of a depth-converted seismic profile across the Hangjinqi Fault Zone (HFZ) in the eastern Hangjinqi area shows one compression that created anticlinal structures in the Late Triassic, and two extensions in Middle Jurassic and Late Early Cretaceous, which were interrupted by inversions in the Late Jurassic-Early Early Cretaceous and Late Cretaceous, respectively. Hydrocarbon generation at the well locations in the Central Ordos Basin (COB) began in the Late Triassic. Basin modeling of Well Zhao-4 suggests that hydrocarbon generation from the Late Carboniferous-Early Permian coal measures of the northern Shanbei Slope peaked in the Early Cretaceous, predating the inversion in the Late Cretaceous. Most source rocks in the Shanbei Slope passed the main gas-migration phase except for the Hangjinqi area source rocks (Well Jin-48). Hydrocarbons generated from the COB are likely to have migrated northward toward the anticlinal structures and traps along the HFZ because the basin-fill strata are dipping south. Faulting that continued during the extensional phase (Late Early Cretaceous) of the Hangjinqi area probably acted as conduits for the migration of hydrocarbons. Thus, the anticlinal structures and associated traps to the north of the HFZ might have trapped hydrocarbons that were charged from the Late Carboniferous-Early Permian coal measures in the COB since the Middle Jurassic. © 2015 Geological Society of China.

Chen X.,Chinese Academy of Geological Sciences | Ye H.,Chinese Academy of Geological Sciences | Wang H.,China Railway Resources Exploration Corporation Ltd.
Journal of Asian Earth Sciences | Year: 2014

The Leimengou Mo deposit is located in the East Qinling-Dabie metallogenic Mo belt, located at the southern margin of the North China Craton. The deposit is hosted within the Mesozoic Leimengou granite porphyry pluton and at the contact between the granite and Late Archean gneisses. In light of mineral assemblage and crosscutting relationships among veinlets, the mineralization and alteration can be classified in four distinct stages: (1) a Mo-barren pre-mineralization stage of alteration characterized by massive K-feldspar alteration of the granite porphyry; (2) a K-feldspar-quartz vein stage that formed veinlets with minor molybdenite; (3) a quartz-sulfide veinlet stage, which is the main stage of mineralization; and (4) post-mineralization quartz-calcite vein stage.Stage 1 alteration is associated with fluid inclusions of low-medium salinity (2.4-13.1wt.% NaClequiv) that homogenized at medium to high temperatures (238-476°C). Stage 2 mineralization is associated with fluid inclusions that homogenized at 201-389°C and that have salinities of 2.0-13.6wt.% NaClequiv. Fluid inclusions that formed during stage 3 have homogenization temperatures of 205-370°C and corresponding salinities of 1.0-17.6wt.% NaClequiv to 31.4-40.6wt.% NaClequiv, indicative of fluid immiscibility and mixing of hydrothermal fluids with meteoric water. Stage 4 H2O-NaCl fluids were trapped at lower temperatures (148-246°C) and have salinities of 1.7-7.9wt.% NaClequiv.Stages 1 to 4 have calculated δ18Ofluid values of 3.6-4.3‰, 2.7-2.8‰, 0.6-2.3‰, and -3.2‰ to -3.8‰, respectively, with δDfluid values of -72‰ to -80‰, -83‰ to -90‰, -68‰ to -82‰, and -81‰ to -90‰, respectively. These results are consistent with the fluid inclusion data outlined above and suggest that early fluids were exsolved from the granitic magma and underwent progressive mixing with meteoric water. Molybdenum was initially transported from the crystallizing magma in a hot, alkaline, and oxidized fluid, while decreasing temperatures and pH, water-rock interaction, and fluid immiscibility during fluid ascent resulted in its precipitation and deposition. © 2013.

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