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Liu X.,CAS Institute of Geology and Geophysics | Fan H.R.,CAS Institute of Geology and Geophysics | Qiu Z.J.,CAS Institute of Geology and Geophysics | Qiu Z.J.,University of Chinese Academy of Sciences | And 4 more authors.
Acta Petrologica Sinica | Year: 2015

Zhongtiao Mountain region, located at the southern edge of the North China Craton (NCC), contains voluminous outcrops of Early Proterozoic rocks, and it has been considered as an important area for investigating the tectonic evolution of the NCC. Jiangxian Group consisting of metamorphosed continental clastic to volcanic rocks and Zhongtiao Group comprising metamorphosed terrestrial clastic rocks and carbonate are the two major rock units within this region, and their formation ages remains elusive. We report new results of U-Pb dating on zircons from two intercalated plagioclase amphibolites by secondary ion mass spectrometry (SIMS), which suggest the Jiangxian and Zhongtiao groups were formed at ca. 2160 ∼ 2190Ma and ca. 2059 ∼ 2086Ma, respectively. Combing other evidences, including rock assemblages and mineralization styles, we favor the idea that Zhongtiao Mountain region experienced two episodes of rifting during the Early Proterozoic period.

Qiu Z.,CAS Institute of Geology and Geophysics | Qiu Z.,University of Chinese Academy of Sciences | Fan H.,CAS Institute of Geology and Geophysics | Liu X.,CAS Institute of Geology and Geophysics | And 6 more authors.
Acta Geologica Sinica | Year: 2015

The Hujiayu Cu deposit, representative of the "HuBi-type" Cu deposits in the Zhongtiao Mountains district in the southern edge of the North China Craton, is primarily hosted in graphite-bearing schists and carbonate rocks. The ore minerals comprise mainly chalcopyrite, with minor sphalerite, siegenite [(Co, Ni)3S4], and clausthalite [Pb(S,Se)]. The gangue minerals are mainly quartz and dolomite, with minor albite. Four fluid inclusion types were recognized in the chalcopyrite-pyrite-dolomite-quartz veins, including CO2-rich inclusions (type I), low-salinity, liquid-dominated, biphase aqueous inclusions (type II), solid-bearing aqueous inclusions (type III), and solid-bearing aqueous-carbonic inclusions (type IV). Type I inclusion can be further divided into two sub-types, i.e., monophase CO2 inclusions (type Ia) and biphase CO2-rich inclusions (with a visible aqueous phase), and type III inclusion is divided into a subtype with a halite daughter mineral (type IIIa) and a subtype with multiple solids (type IIIb). Various fluid inclusion assemblages (FIAs) were identified through petrographic observations, and were classified into four groups. The group-1 FIA, consisting of monophase CO2 inclusions (type Ia), homogenized into the liquid phase in a large range of temperatures from -1 to 28°C, suggesting post-entrapment modification. The group-2 FIA consists of type Ib, IIIb and IV inclusions, and is interpreted to reflect fluid immiscibility. The group-3 FIA comprises type II and IIIa inclusions, and the group-4 FIA consists of type II inclusions with consistent phase ratios. The group-1 and group-2 FIAs are interpreted to be entrapped during mineralization, whereas group-3 and group-4 FIAs probably represent the post-mineralization fluids. The solid CO2 melting temperatures range from -60.6 to 56.6° C and from -66.0 to -63.4° C for type Ia and type IV inclusions, respectively. The homogenization temperatures for type II inclusions range from 132 to 170°C for group-3 FIAs and 115 to 219°C for group-4 FIAs. The halite melting temperatures range from 530 to 562°C for type IIIb and IV inclusions, whereas those for type IIIa inclusions range from 198 to 398°C. Laser Raman and SEM-EDS results show that the gas species in fluid inclusions are mainly CO2 with minor CH4, and the solids are dominated by calcite and halite. The calcite in the hosting marble and dolomite in the hydrothermal veins have δ13CV-PDB values of -1.2 to 1.2‰ and -1.2 to -6.3‰, and δ18OV-SMOW values of 14.0 to 20.8 ‰ and 13.2 to 14.3 ‰, respectively. The fluid inclusion and carbon-oxygen isotope data suggest that the ore-forming fluids were probably derived from metamorphic fluids, which had reacted with organic matter in sedimentary rocks or graphite and undergone phase separation at 1.4-1.8 kbar and 230-240°C, after peak metamorphism. It is proposed that the Hujiayu Cu deposit consists of two mineralization stages. The early stage mineralization, characterized by disseminated and veinlet copper sulfides, probably took place in an environment similar to sediment-hosted stratiform copper mineralization. Ore minerals formed in this precursor mineralization stage were remobilized and enriched in the late metamorphic hydrothermal stage, leading to the formation of thick quartz-dolomite-sulfides veins. © 2015 Geological Society of China.

Li N.,CAS Guangzhou Institute of Geochemistry | Li N.,University of Chinese Academy of Sciences | Luo Y.,Nanyang Normal University | Guo S.,Zhongtiaoshan Non ferrous Metals Group Co. | And 5 more authors.
Acta Petrologica Sinica | Year: 2013

The formation time of the metamorphic quartz-monzonite porphyry associated with the Tongkuangyu porphyry copper deposit is still controversy. A set of zircon U-Pb geochronology and in-stiu Hf isotopic date was presented in this study for the metamorphic quartz-monzonite porphyry. The result show that the discordia upper intercept age 2121 ± 1OMa and 207Pb/Pb 206 age range from 2065Ma to 2196Ma, have a weighted average age 2117 ± 13Ma. This age (2117 ± 13Ma) is accounted as the formation time of the metamorphic quartz-monzonite porphyry from Tongluangyu porphyry copper deposit, and is approximately consistent with the extension of the North China Craton (NCC), especially the activity of Zhongtiao rift which is located in the southern part of NCC. In addition, zircons Hf isotopic characteristics (εHf(t) range from -7.79 to 0.39) indicate that the old crustal materials played an important role in the petrogenesis. So, we conclude that the Tongkuangyu porphyry Cu deposit is a typical porphyry Cu deposit formed in inner continental settings, which genetic with the large-scale extension of the NCC.

Jiang Y.,CAS Guangzhou Institute of Geochemistry | Jiang Y.,University of Chinese Academy of Sciences | Luo Y.,Nanyang Normal University | Niu H.,CAS Guangzhou Institute of Geochemistry | And 3 more authors.
Acta Petrologica Sinica | Year: 2013

Luojiahe copper deposit is located in the Luojiahe tectonic-erosion window, southeastern of Zhongtiao rift. Cumineralization occurs in the metamorphic volcanic-sediments of the Songjiashan Formation which is covered by Mesoproterozoic andesitic rocks of the Xiyanghe Group. This paper focuses on the study of fluid inclusions in ore-bearing quartz veins which are intergrowth with ore-body, to discuss the features of ore-forming fluids and the implications for Cu-mineralization. Based on systematically petrographic observation, fluid inclusions are classified into five types by phases: Pure vapor inclusions (I-type), pure aqueous inclusions (II-type), vapor-rich inclusions (Ill-type), aqueous-rich inclusions (IV-type) and daughter mineral-bearing inclusions (V-type). Il-type and IV-type inclusions are dominant in the upper orebody, and I-type and V-type inclusions are dominant in the lower orebody. The coexistence of V-type with I-type inclusions shows the features of boiling assemblage. Microthermometry data indicates that there are two different systems of CaCl2-NaCl-H2O system (IVal-type) and NaCl-H2O system (IVa2-type) in the liquid-rich aqueous inclusions (IVa types), corresponding to the upper quartz veins and the lower quartz veins. Both homogenization temperature (Th) and salinity of the two types are different, indicating that the ore-forming fluids might originate from two different fluid sources. The Th of IVal-type range from l00°C to 208°C and salinities range from 10. 24% to 20. 45% NaCleqv. It is suggest that the fluid of IVal-type is hot brine derived from sea water. In contrary, the IVa2-type is from magmatic fluid, with Th of 151 ∼ 306°C and salinities of 3. 39% ∼ 15. 07% NaCleqv, respectively. Th and salinities of the V-type inclusions are in range of 175 ∼300°C and 30. 7% ∼38. 16% NaCleqv. In this regards, we can infer that hot brine and magmatic fluids have different influences to Cu-mineralization. The former extracted metal elements from volcanic rocks, and then precipitated when loss of temperature and pressure. The later released metal elements by phase separation. Laser-Raman microspectroscopy analyses show that the vapour phase of the fluid inclusions is composed of H2O and a few C02. Regarding the regional tectonic setting, fluids channel, mechanism and the features of ore-forming fluids, we conclude that the Luojiahe Cu deposit is a volcanic-associated massive sulfide deposit of Precambrian.

Dong X.-L.,Zhongtiaoshan Nonferrous Metals Group Co.
Yejin Fenxi/Metallurgical Analysis | Year: 2011

The content of eight elements including copper, lead, selenium, antimonium, bismuth, arsenic, iron and nickel in copper anode mud sample were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) after dissolution of sample with hydrochloric acid and nitric acid. The determination conditions, such as sampling amount, sample dissolution, medium and the selection of analytical lines, were discussed. Under the optimized conditions, the matrix and coexisting elements had no interference in the determination of determined elements, so pre-separation was not necessary. The linear ranges of calibration curves of elements were as follows: 0-50 μg/mL for Cu, 0-20 μg/mL for Pb and Se, and 0-10 μg/mL for Sb, Bi, As, Fe and Ni. The correlation coefficients of calibration curves were 0.9991-0.9999. The proposed method had been applied to the analysis of copper anode mud in production and management. The determination results were consistent with those obtained by chemical method. The recoveries of standard addition were 97.1%-106.8%, and relative standard deviations (RSD) were in the range of 0.37%-2.7%.

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