The Tuolugou cobalt deposit is the first independent large-scale Co- and Au-bearing deposit discovered in northwestern China. It is located in the eastern Kunlun orogenic belt in Qinghai Province, and occurs conformab...The Tuolugou cobalt deposit is the first independent large-scale Co- and Au-bearing deposit discovered in northwestern China. It is located in the eastern Kunlun orogenic belt in Qinghai Province, and occurs conformably in low-grade metamorphic volcano-sedimentary rock series with well-developed Na-rich hydrothermal sedimentary rocks and typical hydrothermal sedimentary ore fabrics. Fluid inclusions and isotopic geochemistry studies suggest that cobalt mineralizing fluid is dominated by NaCI-H20 system, accompanied by NaCI-CO2-H20-N2 system responsible for gold mineralization. Massive, banded and disseminated pyrite ores have similar compositions of He and Ar isotopes from the mineralizing fluid, with 3He/4He range between 0.10 to 0.31Ra （averaging 0.21Ra）, and 4~Ar/36Ar between 302 and 569 （averaging 373）, which reflects that Co mineralizing fluids derived dominantly from meteoric water deeply circulating. ~34S values of pyrite approaches to zero （~34S ranging from -4.5%o to ＋1.5%o, centering around -1.8%o to -0.2%o）, reflecting its deep source. Ore lead is characterized by distinctly high radiogenesis, with 2~6pb/2~4pb〉19.279, 2~7pb/2~4pb〉15.691 and 2~spb/2~4pb〉39.627, and its values show an increase trend from country rocks, regional Paleozoic volcanic rocks to ores. This may have suggested that high radiogentic ore Pb derived mainly from country rocks by leaching meteoric water-dominated hydrothermal fluid during its circulation at depth. Cobalt occurs mainly in sulfide phase （such as pyrite）, but cobalt enrichment, and presence and increasing contents of Co-bearing minerals have a positive correlation with metamorphic degree. The Tuolugou deposit and other typical strata-bound Co-Cu-Au deposits have striking similarities in the geological features and metallogenic pattern of primary cobalt. All of them are syngenetic hydrothermal exhalative sedimentation in origin.展开更多
Ore forming process of the Dongshengmiao, Huogeqi, Tanyaokou and Jiashengpan deposits in Langshan Zhaertai Mesoproterozoic SEDEX metallogenic belt is closely related to the syndepositional volcanic activities based ...Ore forming process of the Dongshengmiao, Huogeqi, Tanyaokou and Jiashengpan deposits in Langshan Zhaertai Mesoproterozoic SEDEX metallogenic belt is closely related to the syndepositional volcanic activities based on the following facts: (1) The Sm Nd isochron age of the basic volcanic rocks varies from 1 491 Ma to 1 824 Ma (more than or close to the model age of the lead isotope of all sulfide minerals) in these deposits, with ε (Nd, t ) =(3.48-6.40)±0.80, whose REE composition is enriched in LREE and depleted in HREE, indicating that these volcanic rocks were derived from the mantle or lower crust. (2) The REE composition of some Pb Zn Py ores is also enriched in LREE and depleted in HREE. The chondrite normalized REE patterns are similar to those of the basic volcanic rocks. (3) In the lead isotope composition diagram of Doe and Zartman, most of sphalerite, galena, pyrite, pyrrhotite and chalcopyrite are plotted on both sides of the line for the mantle or between the lines for the mantle and lower crust. (4) Cobalt content of some pyrites is much higher than their nickel content ( w (Co)/ w (Ni)= 11.91- 12.19). (5) Some volcanic blocks and debrises have been picked out from some pyrite and pyrrhotite ores. (6) All Zn Pb Cu Fe sulfide orebodies in these deposits occur in the strata overlying the metamorphic volcanic rocks in the only second ore bearing formation. The Jiashengpan deposit lacks in syndepositional volcanic rocks in the host succession, only Pb and Zn occur without Cu, but the Dongshengmiao, Tanyaokou and Huogeqi deposits with syndepositonal volcanic rocks in the host succession contain Cu, indicating the relatively high ore forming temperatures, besides Pb and Zn. The syndepositional volcanic eruption directly supplied some ore forming metals and resulted in the secular geothermal anomaly favorable for the circulation of the submarine convective hydrothermal system, and in the precipitation of deep mineralizing fluids exhaling into the anoxide basins along the syndep展开更多
基金supported by grant no K090 1 from the Scientific Research Fund of the China Central Non-Commercial Institutethe Program of Excellent Young Scientists from the Ministry of Land and Resources(200809)+1 种基金grant No40302019 from the National Natural Science Foundation of ChinaGeological Survey Program Grant 1212011085528 from the China Geological Survey
文摘The Tuolugou cobalt deposit is the first independent large-scale Co- and Au-bearing deposit discovered in northwestern China. It is located in the eastern Kunlun orogenic belt in Qinghai Province, and occurs conformably in low-grade metamorphic volcano-sedimentary rock series with well-developed Na-rich hydrothermal sedimentary rocks and typical hydrothermal sedimentary ore fabrics. Fluid inclusions and isotopic geochemistry studies suggest that cobalt mineralizing fluid is dominated by NaCI-H20 system, accompanied by NaCI-CO2-H20-N2 system responsible for gold mineralization. Massive, banded and disseminated pyrite ores have similar compositions of He and Ar isotopes from the mineralizing fluid, with 3He/4He range between 0.10 to 0.31Ra （averaging 0.21Ra）, and 4~Ar/36Ar between 302 and 569 （averaging 373）, which reflects that Co mineralizing fluids derived dominantly from meteoric water deeply circulating. ~34S values of pyrite approaches to zero （~34S ranging from -4.5%o to ＋1.5%o, centering around -1.8%o to -0.2%o）, reflecting its deep source. Ore lead is characterized by distinctly high radiogenesis, with 2~6pb/2~4pb〉19.279, 2~7pb/2~4pb〉15.691 and 2~spb/2~4pb〉39.627, and its values show an increase trend from country rocks, regional Paleozoic volcanic rocks to ores. This may have suggested that high radiogentic ore Pb derived mainly from country rocks by leaching meteoric water-dominated hydrothermal fluid during its circulation at depth. Cobalt occurs mainly in sulfide phase （such as pyrite）, but cobalt enrichment, and presence and increasing contents of Co-bearing minerals have a positive correlation with metamorphic degree. The Tuolugou deposit and other typical strata-bound Co-Cu-Au deposits have striking similarities in the geological features and metallogenic pattern of primary cobalt. All of them are syngenetic hydrothermal exhalative sedimentation in origin.
基金This study is supported by the State"973"High-Tech Project( No. G19990 43 2 15 ) and the Key Project of the Former Ministry o
文摘Ore forming process of the Dongshengmiao, Huogeqi, Tanyaokou and Jiashengpan deposits in Langshan Zhaertai Mesoproterozoic SEDEX metallogenic belt is closely related to the syndepositional volcanic activities based on the following facts: (1) The Sm Nd isochron age of the basic volcanic rocks varies from 1 491 Ma to 1 824 Ma (more than or close to the model age of the lead isotope of all sulfide minerals) in these deposits, with ε (Nd, t ) =(3.48-6.40)±0.80, whose REE composition is enriched in LREE and depleted in HREE, indicating that these volcanic rocks were derived from the mantle or lower crust. (2) The REE composition of some Pb Zn Py ores is also enriched in LREE and depleted in HREE. The chondrite normalized REE patterns are similar to those of the basic volcanic rocks. (3) In the lead isotope composition diagram of Doe and Zartman, most of sphalerite, galena, pyrite, pyrrhotite and chalcopyrite are plotted on both sides of the line for the mantle or between the lines for the mantle and lower crust. (4) Cobalt content of some pyrites is much higher than their nickel content ( w (Co)/ w (Ni)= 11.91- 12.19). (5) Some volcanic blocks and debrises have been picked out from some pyrite and pyrrhotite ores. (6) All Zn Pb Cu Fe sulfide orebodies in these deposits occur in the strata overlying the metamorphic volcanic rocks in the only second ore bearing formation. The Jiashengpan deposit lacks in syndepositional volcanic rocks in the host succession, only Pb and Zn occur without Cu, but the Dongshengmiao, Tanyaokou and Huogeqi deposits with syndepositonal volcanic rocks in the host succession contain Cu, indicating the relatively high ore forming temperatures, besides Pb and Zn. The syndepositional volcanic eruption directly supplied some ore forming metals and resulted in the secular geothermal anomaly favorable for the circulation of the submarine convective hydrothermal system, and in the precipitation of deep mineralizing fluids exhaling into the anoxide basins along the syndep
