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Xiao S.,University of Science and Technology Beijing | Wu S.-C.,University of Science and Technology Beijing | Gao Y.-T.,University of Science and Technology Beijing | Han G.,University of Science and Technology Beijing | And 3 more authors.
Gongcheng Kexue Xuebao/Chinese Journal of Engineering | Year: 2015

With the south slope (footwall) of an open pit in Zambia as a research subject, the Rosenbluth point estimation method (PEM) coupled with the jointed finite element method (JFEM) was applied to this jointed rock slope stability evaluation. A probability model was established, which puts the mean and standard deviation of rock material strength parameters (friction angle and cohesive) as input variables and the safety factors as output variables, and the point estimation state functions were solved by the jointed finite element method. According to on-site joints and structural surface surveys, a jointed slope model was built to solve the safety factors, and then the probability distribution of the safety factors was obtained. The results of probability analysis are consistent with the instability situation on site. Since the uncertainty of rock materials and the properties of rock joints are taken into account, this method fully reflects the role of the non-linear relationship among rock layers and makes the rock slope stability estimation more reasonable. ©, 2015, The Editorial Board of CHINESE JOURNAL OF ENGINEERING. All right reserved. Source

Li J.,CAS Institute of Tibetan Plateau Research | Qin K.,CAS Institute of Geology and Geophysics | Li G.,CAS Institute of Geology and Geophysics | Cao M.,CAS Institute of Geology and Geophysics | And 8 more authors.
Mineralogy and Petrology | Year: 2012

The Yulong porphyry copper deposit (6.5 Mt at 0.46 % Cu) in eastern Tibet was formed in a post-collisional setting. New zircon U-Pb and U-Th/He ages, apatite U-Th/He ages and in-situ zircon Hf isotopic and trace element data for the Yulong ore-bearing adakitic porphyries elucidate the thermal history and petrogenesis of the deposit. Zircon U-Pb ages range from from 41.2 Ma to 40.7 Ma, indicating an Eocene formation age. Combined with the zircon U-Th/He age of 37.5 ± 1.2 Ma, results suggest that magmatic-hydrothermal evolution lasted up to 5 m. y. The apatite U-Th/He age of 33.4 ± 0.9 Ma reflects Yulong deposit exhumation during the ~33-30 Ma Tibetan uplift. Moreover, the high εHf(t)-values (7.1 ~ 12.2) zircon yield the highest ΣREE content, higher Y/Hf, lower Ce/Ce* and higher Th/U ratios compared to inherited zircon or magmatic zircon suggesting that the high εHf(t) zircon crystallized from another magma, and that magma mixing probably contributed to the adakitic porphyries at Yulong. In addition, inherited and magmatic zircon with the lowest εHf(t) values (-20.6 ~ -4.4) suggest crustal contamination. The positive zircon εHf(t) values indicate a source in the juvenile arc lower crust. Significantly, the juvenile arc lower crust inherited arc magma characteristics (abundant F, Cl, Cu and high oxidation state), which are now found in the porphyry Cu-Mo deposits. © 2012 Springer-Verlag. Source

Li J.-X.,CAS Institute of Tibetan Plateau Research | Li J.-X.,Chinese Academy of Sciences | Qin K.-Z.,CAS Institute of Geology and Geophysics | Li G.-M.,CAS Institute of Geology and Geophysics | And 5 more authors.
Geological Journal | Year: 2016

The Duolong porphyry Cu-Au deposit (5.4Mt at 0.72% Cu, 41t at 0.23g/t Au) was recently discovered in the southern Qiangtang terrane, central Tibet. Here, new whole-rock elemental and Sr-Nd-Pb isotope and zircon Hf isotopic data of syn- and post-ore volcanic rocks and barren and ore-bearing granodiorite porphyries are presented for a reconstruction of magmas associated with Cu-Au mineralization. LA-ICP-MS zircon U-Pb dating yields mean ages of 117.0±2.0 and 120.9±1.7Ma for ore-bearing granodiorite porphyry and 105.2±1.3Ma for post-ore basaltic andesite. All the samples show high-K calc-alkaline compositions, with enrichment of light rare earth elements (LREE) and large ion lithophile elements (LILE: Cs and Rb) and depletion of high field strength elements (HFSE: Nb and Ti), consistent with the geochemical characteristics of arc-type magmas. Syn- and post-ore volcanic rocks show initial Sr ratios of 0.7045-0.7055, εNd(t) values of -0.8 to 3.6, (206Pb/204Pb)t ratios of 18.408-18.642, (207Pb/204Pb)t of 15.584-15.672 and positive zircon εHf(t) values of 1.3-10.5, likely suggesting they dominantly were derived from metasomatized mantle wedge and contaminated by southern Qiangtang crust. Compared to mafic volcanic rocks, barren and ore-bearing granodiorite porphyries have relatively high initial Sr isotopic ratios (0.7054-0.7072), low εNd(t) values (-1.7 to -4.0), similar Pb and enriched zircon Hf isotopic compositions [εHf(t) of 1.5-9.7], possibly suggesting more contribution from southern Qiangtang crust. Duolong volcanic rocks and granodiorite porphyries likely formed in a continental arc setting during northward subduction of the Bangong-Nujiang ocean and evolved at the base of the lower crust by MASH (melting, assimilation, storage and homogenization) processes. © 2016 John Wiley & Sons, Ltd. Source

Wang Y.M.,University of Science and Technology Beijing | Huang M.Q.,University of Science and Technology Beijing | Wu A.X.,University of Science and Technology Beijing | Yao G.H.,China Nonferrous Metal Mining Group Co. | Hu K.J.,University of Science and Technology Beijing
Applied Mechanics and Materials | Year: 2013

Goafs formed in mine-out areas threat the underground mines owing to possibilities of rock burst and surface subsidence. This paper aims to discuss the feasibility, design and construction of waste rock backfill in abandoned stopes. Based on goafs distribution and stabilities in the White Bull Mine, rock backfill system with a total volume of 362,000 m3 in 8 gobs was designed and carried out. The system included technologically and economically feasible stopes, conveying equipments of tramcars, rock transfer by electric rakes, haulage network and mining workings. Field effects showed that rock backfill was applicable to control potential hazards. With rock filling, goaf utilization rates ranged from 60% to 70%, which helped to control adjacent rock movement, eliminate rock burst and surface subsidence. Additionally, backfill construction reduced the lift and transportation costs of rocks by about 50%, which further lowered the land usage of surface dumping. © (2013) Trans Tech Publications, Switzerland. Source

Jiang S.-H.,Chinese Academy of Geological Sciences | Bagas L.,Chinese Academy of Geological Sciences | Bagas L.,University of Western Australia | Hu P.,China Nonferrous Metal Mining Group Co. | And 4 more authors.
Lithos | Year: 2016

The Shamai tungsten deposit is located in the eastern part of the Central Asian Orogenic Belt (CAOB). Tungsten mineralization is closely related to the emplacement of fine- to medium-grained biotite monzogranite (G1) and porphyritic biotite monzogranite (G2) in the Shamai Granite. NW-trending joints and faults host orebodies in the Shamai Granite and Devonian hornfels. The mineralization is characterized by a basal veinlet zone progressing upwards to a thick vein zone followed by a mixed zone, a veinlet zone, and a thread vein zone at the top. The ore-related alteration typically consists of muscovite, greisen, and hornfels.In order to constrain the timing of the Shamai mineralization and discuss the ore genesis, muscovite Ar-Ar, molybdenite Re-Os, and zircon U-Pb geochronological, geochemical, and Sr-Nd-Hf isotopic studies were completed on the deposit. The U-Pb zircon dating yielded weighted mean ages of 153. ±. 1. Ma for G1 and 146. ±. 1. Ma for G2. Muscovite from a wolframite-bearing quartz vein yielded an Ar-Ar plateau age of 140. ±. 1. Ma, whereas two molybdenite samples yielded identical Re-Os model ages of 137. ±. 2. Ma. These two ages are younger than the two monzogranites, suggesting a prolonged magmatic-hydrothermal interaction during tungsten mineralization.Major and trace element geochemistry shows that both G1 and G2 are characterized by high SiO2 and K2O contents, high A/CNK values (1.08-1.40), a spectacular tetrad effect in their REE distribution patterns, and non-CHARAC (charge-and-radius-controlled) trace element behavior. This suggests that both G1 and G2 are highly differentiated peraluminous rocks with strong hydrothermal interaction. The Nd-Hf isotope data for the Shamai Granite (εNd(t) between -1.9 and +7.4, e(open)Hf(t) from 5.2 to 12.8) are largely compatible with the general scenario for much of the Phanerozoic granite emplaced in the CAOB. It is here suggested that the Shamai Granite originated from partial melting of a juvenile lower crust with minor input of upper crustal material caused by the underplating of mafic magma in an extensional setting. It can also be concluded that the prolonged fractional crystallization and magmatic-hydrothermal interactions have contributed to the formation of the Shamai tungsten deposit. © 2015 Elsevier B.V. Source

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