The newly discovered Changkeng Au-Ag deposit is a new type of sediment-hostedprecious metal deposit. Most of the previous researchers believed that the deposit was formed bymeteoric water convection. By using a high v...The newly discovered Changkeng Au-Ag deposit is a new type of sediment-hostedprecious metal deposit. Most of the previous researchers believed that the deposit was formed bymeteoric water convection. By using a high vacuum quadrupole gas mass spectrometric system, ninelight hydrocarbons have been recognized in the fluid inclusions in ore minerals collected from theChangkeng deposit. The hydrocarbons are composed mainly of saturated alkanes C_(1-4) and unsaturatedalkenes C_(2-4) and aromatic hydrocarbons, in which the alkanes are predominant, while the contentsof alkenes and aromatic hydrocarbons are very low. The sum alka/sum alke ratio of most samples ishigher than 100, suggesting that those hydrocarbons are mainly generated by pyrolysis of kerogens insedimentary rocks caused by water-rock interactions at medium-low temperatures, and themetallogenic processes might have not been affected by magmatic activity. A thermodynamiccalculation shows that the light hydrocarbons have reached chemical equilibrium at temperatureshigher than 200 deg C, and they may have been generated in the deep part of sedimentary basins(e.g., the Sanzhou basin) and then be transported by ore-forming fluids to a shallow position of thebasin via a long distance. Most of the organic gases are generated by pyrolysis of the type IIkerogens (kukersite) in sedimentary host rocks, only a few by microorganism activity. Thecompositions and various parameters of light hydrocarbons in gold ores are quite similar to those insilver ores, suggesting that the gold and silver ores may have similar metallogenic processes.Based on the compositions of organic gases in fluid inclusions, the authors infer that the Changkengdeposit may be of a tectonic setting of continental rift. The results of this study support fromone aspect the authors' opinion that the Changkeng deposit is not formed by meteoric waterconvection, and that its genesis has a close relationship with the evolution of the Sanzhou basin,so it belongs to the sedimentary hot brine transformed deposit.展开更多
According to Ihe combinations of mctallogcnetic elements and minerals assemblages,the Au-Ag deposits in the Middle-Upper Proterozoic Suberathcm of the middle of northern margin of Yangtze Platform could be classified ...According to Ihe combinations of mctallogcnetic elements and minerals assemblages,the Au-Ag deposits in the Middle-Upper Proterozoic Suberathcm of the middle of northern margin of Yangtze Platform could be classified into four types,(l)Au-Ag-Pb-Zn type,(2)Au-Ag-Te type,(3)Au-quartz vein type,(4)Au-Ag-Pb-Zn-Ba type.The Yangpin formation and the upper Dangyuhe subformation,which belong to Wudangshan group,are regarded as favorable strata for Au-Ag mineralization by systematic assessments for Au-Ag bearing ability of the strata,as well as the felsic rocks of Bikou group.The mctallogcnetic physicochemical conditions and the stable isotopic compositions(S.Pb,H.O,C)have been studied in this paper.The sources of metallogenetic materials,origins of fluids and genesis of various deposits have also been studied.展开更多
This paper presents the brief geological and mineralogical characteristics of the Dorozhnoye mesothermal gold ore deposit (Magadan Region, Russia). The gold and silver minerals are represented by electrum (530‰ - 700...This paper presents the brief geological and mineralogical characteristics of the Dorozhnoye mesothermal gold ore deposit (Magadan Region, Russia). The gold and silver minerals are represented by electrum (530‰ - 700‰), freibergite, stephanite, pyrargyrite and Bi-diaphorite. The homogeneous fluid inclusions enable one to determine that the quartz-molybdenite veins were formed at a temperature of 340°C to 140°C, and that the quartz-sulfide gold ore veins were formed at a temperature of 165°C to 125°C. It is assumed that the fluid had a mixed composition and evolved from K-chloride and K-carbonate to Na-chloride. The hypergenesis zone contains: high fineness gold (800‰ - 950‰), petrovskaite (AgAuS) and uytenbogaardtite (Ag3AuS2) associated with goethite and melanterite. The surface waters contain: Ca++ up to 293 mg/L, HCO3 up to 125 mg/L, SO4 up to 777 mg/L;рН is 5.8 to 7.2. Thermodynamic calculations have been conducted and Eh-pH diagrams have been built for the Au-Ag-S-H2O system at 25°C and 100°C (p = 1 bar) to reveal gold and silver stability fields. Au-Ag sulfides at the Dorozhnoye deposit are formed under oxidizing conditions and an acidic environment with dominating sulfates.展开更多
为揭示熊耳山东草沟金矿床成矿流体性质和流体演化过程,以与金矿关系密切的石英为研究对象,开展了系统的野外调查以及流体包裹体岩相学和显微测温研究。结果表明,东草沟金矿体分布主要受构造控制,成矿期次可分为3个阶段:早期石英+绢云母...为揭示熊耳山东草沟金矿床成矿流体性质和流体演化过程,以与金矿关系密切的石英为研究对象,开展了系统的野外调查以及流体包裹体岩相学和显微测温研究。结果表明,东草沟金矿体分布主要受构造控制,成矿期次可分为3个阶段:早期石英+绢云母+黄铁矿阶段、中期石英+多金属硫化物阶段、晚期石英+碳酸盐岩。主要存在5种类型的流体包裹体:D型,含子矿物包裹体;C型,含CO 2水溶液包裹体;LV型,气液两相包裹体;L型,单水溶液包裹体;V型,单水蒸气相包裹体。根据升温过程中子矿物与气泡消失的先后情况,D型包裹体可进一步分为Da型(子矿物先消失)和Db型(气泡先消失)。Da型包裹体子矿物融化温度为211~240℃,均一温度为216~391℃,盐度值32.4%~34.1%;Db型气液相均一温度为172~267℃,盐度值为30.6%~35.8%。C型包裹体笼合物融化温度为-1.9~8.7℃,盐度为2.6%~17.3%,均一温度为276~310℃。LV型包裹体在第1阶段、2a阶段、2b阶段、3阶段LV型均质温度分别为138~310℃、148~403℃、130~255℃、113~199℃;盐度为1.2~11.5 w t%,2.1~21.7 wt%,1.6~15.3 w t%,10.6~15.3 w t%,0.2~13.2 w t%。分析认为,矿区存在不同性质的成矿流体,且初始流体为岩浆热液系统,后期流体不断演化,流体不混溶是金沉淀的主要诱因,而流体混合则导致了银铅锌等的沉淀。展开更多
Changkeng Au-Ag deposit is a newly-discovered new type precious metal deposit. N2-Ar-He systematics studies and 3He/4He and δD-δ180 composition analyses show that the ore-forming fluid of the deposit is composed mai...Changkeng Au-Ag deposit is a newly-discovered new type precious metal deposit. N2-Ar-He systematics studies and 3He/4He and δD-δ180 composition analyses show that the ore-forming fluid of the deposit is composed mainly of formation water (sedimentary brine) but not of meteoric water, which was thought to be source of the ore-forming fluid by most previous researchers. The content of mantle-derived magmatic water in the ore-forming fluid is quite low, usually lower than 10% . According to the source of the ore-forming fluid, the Changkeng Au-Ag deposit should belong to sedimentary brine transformed deposits. From the Late Jurassic to the Early Cretaceous Period, with deposition and accumulation of thick sediments in Sanzhou Basin, the formation water in the sedimentary layers was expelled from the basin because of overburden pressure and increasing temperature. The expelled fluid moved laterally along sedimentary layers to the margin of the basin, and finally moved upward along a gently-dipping interlayer fault. Because of a decline in pressure and temperature, ore minerals were deposited in the fault.展开更多
ORGANIC matters in the ore-forming fluids are composed mainly of light hydrocarbons. Because of the small amount of hydrocarbons in fluid inclusions, it is quite difficult to study their behavior in mineralizing proce...ORGANIC matters in the ore-forming fluids are composed mainly of light hydrocarbons. Because of the small amount of hydrocarbons in fluid inclusions, it is quite difficult to study their behavior in mineralizing processes, excepting methane （CH<sub>4</sub>）. In this work, we used a high vacuum quadrupole gas massspectrometer system to determine the content and composition of light hydrocarbons (C<sub>1-7</sub>) in fluid inclusions in minerals collected from Changkeng Au-Ag deposit. The geological significance of the new data forgenesis of the deposit has been discussed briefly.展开更多
基金supported by the National Natural Science Foundation of China(Nos.49773195 and 49502029)the Visiting Scholar Foundation of Labs in Universities,Research Foundation of the State Key Laboratory of Metallogenesis in Nanjing University+1 种基金Research Foundation of Youth Teachers of National Educational Department and the Training Program of Medium-youth Teachers supported by the Lingnan Foundationsupported by the“Trans-century Training Programme Foundation for the Talents”by the Ministry of Education.
文摘The newly discovered Changkeng Au-Ag deposit is a new type of sediment-hostedprecious metal deposit. Most of the previous researchers believed that the deposit was formed bymeteoric water convection. By using a high vacuum quadrupole gas mass spectrometric system, ninelight hydrocarbons have been recognized in the fluid inclusions in ore minerals collected from theChangkeng deposit. The hydrocarbons are composed mainly of saturated alkanes C_(1-4) and unsaturatedalkenes C_(2-4) and aromatic hydrocarbons, in which the alkanes are predominant, while the contentsof alkenes and aromatic hydrocarbons are very low. The sum alka/sum alke ratio of most samples ishigher than 100, suggesting that those hydrocarbons are mainly generated by pyrolysis of kerogens insedimentary rocks caused by water-rock interactions at medium-low temperatures, and themetallogenic processes might have not been affected by magmatic activity. A thermodynamiccalculation shows that the light hydrocarbons have reached chemical equilibrium at temperatureshigher than 200 deg C, and they may have been generated in the deep part of sedimentary basins(e.g., the Sanzhou basin) and then be transported by ore-forming fluids to a shallow position of thebasin via a long distance. Most of the organic gases are generated by pyrolysis of the type IIkerogens (kukersite) in sedimentary host rocks, only a few by microorganism activity. Thecompositions and various parameters of light hydrocarbons in gold ores are quite similar to those insilver ores, suggesting that the gold and silver ores may have similar metallogenic processes.Based on the compositions of organic gases in fluid inclusions, the authors infer that the Changkengdeposit may be of a tectonic setting of continental rift. The results of this study support fromone aspect the authors' opinion that the Changkeng deposit is not formed by meteoric waterconvection, and that its genesis has a close relationship with the evolution of the Sanzhou basin,so it belongs to the sedimentary hot brine transformed deposit.
文摘According to Ihe combinations of mctallogcnetic elements and minerals assemblages,the Au-Ag deposits in the Middle-Upper Proterozoic Suberathcm of the middle of northern margin of Yangtze Platform could be classified into four types,(l)Au-Ag-Pb-Zn type,(2)Au-Ag-Te type,(3)Au-quartz vein type,(4)Au-Ag-Pb-Zn-Ba type.The Yangpin formation and the upper Dangyuhe subformation,which belong to Wudangshan group,are regarded as favorable strata for Au-Ag mineralization by systematic assessments for Au-Ag bearing ability of the strata,as well as the felsic rocks of Bikou group.The mctallogcnetic physicochemical conditions and the stable isotopic compositions(S.Pb,H.O,C)have been studied in this paper.The sources of metallogenetic materials,origins of fluids and genesis of various deposits have also been studied.
文摘This paper presents the brief geological and mineralogical characteristics of the Dorozhnoye mesothermal gold ore deposit (Magadan Region, Russia). The gold and silver minerals are represented by electrum (530‰ - 700‰), freibergite, stephanite, pyrargyrite and Bi-diaphorite. The homogeneous fluid inclusions enable one to determine that the quartz-molybdenite veins were formed at a temperature of 340°C to 140°C, and that the quartz-sulfide gold ore veins were formed at a temperature of 165°C to 125°C. It is assumed that the fluid had a mixed composition and evolved from K-chloride and K-carbonate to Na-chloride. The hypergenesis zone contains: high fineness gold (800‰ - 950‰), petrovskaite (AgAuS) and uytenbogaardtite (Ag3AuS2) associated with goethite and melanterite. The surface waters contain: Ca++ up to 293 mg/L, HCO3 up to 125 mg/L, SO4 up to 777 mg/L;рН is 5.8 to 7.2. Thermodynamic calculations have been conducted and Eh-pH diagrams have been built for the Au-Ag-S-H2O system at 25°C and 100°C (p = 1 bar) to reveal gold and silver stability fields. Au-Ag sulfides at the Dorozhnoye deposit are formed under oxidizing conditions and an acidic environment with dominating sulfates.
文摘为揭示熊耳山东草沟金矿床成矿流体性质和流体演化过程,以与金矿关系密切的石英为研究对象,开展了系统的野外调查以及流体包裹体岩相学和显微测温研究。结果表明,东草沟金矿体分布主要受构造控制,成矿期次可分为3个阶段:早期石英+绢云母+黄铁矿阶段、中期石英+多金属硫化物阶段、晚期石英+碳酸盐岩。主要存在5种类型的流体包裹体:D型,含子矿物包裹体;C型,含CO 2水溶液包裹体;LV型,气液两相包裹体;L型,单水溶液包裹体;V型,单水蒸气相包裹体。根据升温过程中子矿物与气泡消失的先后情况,D型包裹体可进一步分为Da型(子矿物先消失)和Db型(气泡先消失)。Da型包裹体子矿物融化温度为211~240℃,均一温度为216~391℃,盐度值32.4%~34.1%;Db型气液相均一温度为172~267℃,盐度值为30.6%~35.8%。C型包裹体笼合物融化温度为-1.9~8.7℃,盐度为2.6%~17.3%,均一温度为276~310℃。LV型包裹体在第1阶段、2a阶段、2b阶段、3阶段LV型均质温度分别为138~310℃、148~403℃、130~255℃、113~199℃;盐度为1.2~11.5 w t%,2.1~21.7 wt%,1.6~15.3 w t%,10.6~15.3 w t%,0.2~13.2 w t%。分析认为,矿区存在不同性质的成矿流体,且初始流体为岩浆热液系统,后期流体不断演化,流体不混溶是金沉淀的主要诱因,而流体混合则导致了银铅锌等的沉淀。
基金Project supported by the National Natural Science Foundation of China (Grant No. 49502029)the Natural Science Foundation of Zhongshan University Research Foundation of National Key Laboratory of Metallogenesis in Nanjing University (Grant No. 039
文摘Changkeng Au-Ag deposit is a newly-discovered new type precious metal deposit. N2-Ar-He systematics studies and 3He/4He and δD-δ180 composition analyses show that the ore-forming fluid of the deposit is composed mainly of formation water (sedimentary brine) but not of meteoric water, which was thought to be source of the ore-forming fluid by most previous researchers. The content of mantle-derived magmatic water in the ore-forming fluid is quite low, usually lower than 10% . According to the source of the ore-forming fluid, the Changkeng Au-Ag deposit should belong to sedimentary brine transformed deposits. From the Late Jurassic to the Early Cretaceous Period, with deposition and accumulation of thick sediments in Sanzhou Basin, the formation water in the sedimentary layers was expelled from the basin because of overburden pressure and increasing temperature. The expelled fluid moved laterally along sedimentary layers to the margin of the basin, and finally moved upward along a gently-dipping interlayer fault. Because of a decline in pressure and temperature, ore minerals were deposited in the fault.
文摘ORGANIC matters in the ore-forming fluids are composed mainly of light hydrocarbons. Because of the small amount of hydrocarbons in fluid inclusions, it is quite difficult to study their behavior in mineralizing processes, excepting methane （CH<sub>4</sub>）. In this work, we used a high vacuum quadrupole gas massspectrometer system to determine the content and composition of light hydrocarbons (C<sub>1-7</sub>) in fluid inclusions in minerals collected from Changkeng Au-Ag deposit. The geological significance of the new data forgenesis of the deposit has been discussed briefly.
