The Dongchuang gold deposit in the Xiaoqinling area is an orogenic-type lodegold deposit. It is one of the few superlarge (>100 t Au) deposits in China. Although it has beenargued that it was formed in the Mesozoic...The Dongchuang gold deposit in the Xiaoqinling area is an orogenic-type lodegold deposit. It is one of the few superlarge (>100 t Au) deposits in China. Although it has beenargued that it was formed in the Mesozoic, related isotopic age data have not been reported inprevious studies. Based on detailed geological study, the authors have carried out isotopic datingon various metallogenic generations. The ore-forming process of the Dongchuang gold deposit consistsof four stages: coarse-grained pyrite-bearing quartz veins (stage I), fine-grained pyrite-quartzveinlets (stage II), multi-sulfides (stage III) and carbonate-quartz veinlets (stage IV). Ar-Ardating on mineral separates of stages I, II and III yields plateau ages of 142.9 +- 2.9 Ma, 132.2 +-2.6 Ma and 128.3 +- 6.2 Ma, respectively. Sericite separates from stage II assemblage also yield anAr-Ar isochron age of 132.6 +- 2.7 Ma, similar to the Ar-Ar plateau age. These results suggest thatthe Dongchuang gold deposit was mainly formed during 143-128 Ma, coinciding with the authors'geological observations and previous hypothesis. This ore formation is coeval with theregional-tectonic transition from collisional compression to extension, strongly showing that thedecompression-geothermal increase regime during compression-to-extension transition is the mostconducive geodynamic environment to orogenic-type gold mineralization.展开更多
Orogenically-derived gold deposits of the Zhongchuan area in the western Qinling are distributed in the exo-contact thermal metamorphic zone. The country rocks hosting the deposits are predominantly of Devonian age wi...Orogenically-derived gold deposits of the Zhongchuan area in the western Qinling are distributed in the exo-contact thermal metamorphic zone. The country rocks hosting the deposits are predominantly of Devonian age with low-grade metamorphism and strong deformation with the ore deposits directly controlled by multi-level tectonic systems. Three types of inclusions from these deposits have been recognized: CO2-H2O, CO2-rich, and aqueous. The ore-forming fluids were mainly CO2-NaCl-H2O type characterized by rich CO2, low salinity, high temperature and immiscibility. Incorporated with earlier isotopic data, the regional geological setting and features of diagenesis and metallogeny, it can be concluded that the ore-forming fluids were derived from deep magma and mixed with meteoric and metamorphic water. The deposits formed during an intra-continent collisional orogeny, and some of the materials derived from the deep might have been involved in the ore-forming process.展开更多
Based on palaeomagnetic studies of the Precambrian gold deposits in the Xiong'ershan area, Henan Province, the authors infer that the ore-forming processes of the Beiling alteration-type gold ore deposit and the D...Based on palaeomagnetic studies of the Precambrian gold deposits in the Xiong'ershan area, Henan Province, the authors infer that the ore-forming processes of the Beiling alteration-type gold ore deposit and the Dianfang breccia-type gold ore deposit started in the Proterozoic, and was superimposed by later mineralization, whereas the mineralization age of the Jiguanshan quartz- vein type gold ore deposit is Yanshanian.展开更多
Studying the metallogenic age of Dapinggou gold deposit may provide important material not only for the study of metallization and the further prospecting of gold deposits but also for research into tectonic evolution...Studying the metallogenic age of Dapinggou gold deposit may provide important material not only for the study of metallization and the further prospecting of gold deposits but also for research into tectonic evolution in the Altun area. In this study, we used Rb-Sr isotopic dating method of fluid inclusion in the Au-bearing quartz, combining field investigation, REE, sulfur isotopes, lead isotopes, strontium isotopes and hydrogen-oxygen isotope, to determine the metallogenic age of the Dapinggou gold deposit. The only newly-discovered medium-sized gold deposit in the northern Altun area, Dapinggou gold deposit, is controlled by a ductile shear zone. It is characterized by mainly altered mylonite-types with a little K-feldspar quartz vein-types. Data from REE, sulfur isotopes, lead isotopes and strontium isotopes show that the source materials of the deposit were derived mainly from the metamorphic rocks. The data from the inclusion and hydrogen-oxygen isotope indicate that the ore-forming fluid came mainly from dynamic metamorphic water and partly from remelting magmatic water, with a little influence from meteoric water. The density of the ore-forming fluid is 0. 791 - 0. 971g/cm^3 and it contains 2.36 %-5.5 % salinity, The gold deposit was formed at 1.61-2.68 km below the surface at a temperature of 198--290 ℃ and a pressure of （420-700） × 10^5 Pa. The isotopic age from the Rb-Sr isochron of fluid inclusion in quartz is 487 Ma, which indicates that the mineralization occurred in the early Caledonian epoch. The study on the metallogenic age of Dapinggou gold deposit may provide important material not only for the study of metallization and the further prospecting of gold deposits but also for research into tectonic evolution in the Altun area.展开更多
Based on detailed geologic study, the important role of structuring in the formation of gold deposits in the area is discussed with special reference to structural evolution. Syngenetic faulting contemporaneous with t...Based on detailed geologic study, the important role of structuring in the formation of gold deposits in the area is discussed with special reference to structural evolution. Syngenetic faulting contemporaneous with tectonic-volcanic events is thought to be responsible for providing the ore-forming material at depth. The lithofacies formed by highly alternating deposition of terrestrial and carbonate detritus is chemically characterized by the assemblage of Au-Sb-As,constituting a favorable source bed for the activation and enrichment of gold. This gold source bed has undergone four major stages of structural deformation, accompanied by multi-staged alteration and mineralization.展开更多
Abstract This paper deals with characteristics of silicon isotope compositions and siliceous cathodoluminescence of host rocks, ores and hydrothermal silicified quartz of the Carlin-type ore deposits in the Yunnan-Gui...Abstract This paper deals with characteristics of silicon isotope compositions and siliceous cathodoluminescence of host rocks, ores and hydrothermal silicified quartz of the Carlin-type ore deposits in the Yunnan-Guizhou-Guangxi triangle area. The study shows that primary silicified quartz is nonluminescent but quartz in host rocks and secondary silicified quartz are luminescent by the action of cathode rays. Correspondingly, silicon isotope compositions of host rocks, ores and hydro6thermal quartz veins are clearly distinguished. In strata from the Middle Triassic to the “Dachang” host bed, δ30Si of the host rocks ranges from 0.0% ?0.3%, while that of primary ore-forming silicified fluids from ?0.1% to ?0.4%; in the Upper Permian and Lower Carboniferous strata and Indosinian diabase host beds, δ30Si of the host rocks is from ?0.1% to ?0.2% and that of the primary silicified quartz veins from 0.3 % ?0.5 %. This pattern demonstrates the following geochemical mineralization process, primary ore-forming siliceous fluids migrated upwards quickly along the main passages of deep-seated faults from mantle to crust and entered secondary faults where gold deposits were eventually formed as a result of permeation and replacement of the siliceous ore-forming fluids into different ore-bearing strata. This gives important evidence for the fact that ore-forming fluids of this type of gold deposits were mainly derived from upper mantle differentiation and shows good prospects for deep gold deposits and geochemical background for large and superlarge gold deposits.展开更多
In order to understand the mechanism(s) of gold precipitation in the anorthosite-hosted Sangchon gold deposits in the Hadong area, Korea, chemical speciation and reaction path calculations were accomplished by geochem...In order to understand the mechanism(s) of gold precipitation in the anorthosite-hosted Sangchon gold deposits in the Hadong area, Korea, chemical speciation and reaction path calculations were accomplished by geochemical modeling. The modeling consisted of three-step procedures: reaction with anorthosite, then the simple cooling of the reacted fluid, and finally the boiling of metalliferous fluid. The principal vein minerals of the Sangchon deposits consist of quartz, sericite, kaolinite, pyrite, galena, chalcopyrite, sphalerite and acanthite. The sulfide mineralization is typically zoned from pyrite (preferentially at vein margins) to galena and sphalerite (toward vein center). Electrum is intimately associated with pyrite ± chalcopyrite and sphalerite. By comparing the results of modeling with the observed mineral assemblages and paragenesis, the most appropriate evolution path of ore fluids was suggested as follow: reaction of a single fluid with anorthosite at 300℃, then the isobaric cooling of the fluid at temperatures from 250° to 100℃, and then the boiling and cooling of the fluid due to the decrease of pressure and temperature. Calculations also show that all of the observed alteration minerals formed due to fluid-anorthosite interaction at early period, whereas most of sulfides and electrum were precipitated mainly due to cooling. The abundance of gold in veins depends critically on the ratio of total base metals plus iron to sulfide in the aqueous phase, because gold is transported as Au(HS) 2 -whose solubility is very sensitive to the sulfide activity. Our results of geochemical modeling generally fit to the observed mineral assemblages and mineral composition, indicating the usefulness of numerical simulation for elucidating the genesis of gold deposits.展开更多
The depth is important for ore finding in Jiaodong gold deposit. However, many geologists are still discussing how to confirm the depth for the tectonic and metallogenesis formation. The authors of this paper propose ...The depth is important for ore finding in Jiaodong gold deposit. However, many geologists are still discussing how to confirm the depth for the tectonic and metallogenesis formation. The authors of this paper propose a new method-the correction of metallogenic depth via its structure to calculate the depth. This method, based on the crust rock in a solid stress state, emphasizes the elastic pattern rather than the static fluid pattern. In addition, this method is more appropriate to the actual situation in the crust than the method of weight/special weight. The authors of this paper illustrating, with the Jiaodong gold deposit as an example, the metallogenic depth correction via structure conclude that the depth of the most deposits, lower than 4-6 km, is often 2.5 km. Therefore, the authors suggest that there exists a second enrichment belt and that ore resources are more potential at the belt of Jiaodong area. These results have been demonstrated by years of exploration.展开更多
基金This study was financially supported by the National Sciencc Foundation of China(No.49972035).
文摘The Dongchuang gold deposit in the Xiaoqinling area is an orogenic-type lodegold deposit. It is one of the few superlarge (>100 t Au) deposits in China. Although it has beenargued that it was formed in the Mesozoic, related isotopic age data have not been reported inprevious studies. Based on detailed geological study, the authors have carried out isotopic datingon various metallogenic generations. The ore-forming process of the Dongchuang gold deposit consistsof four stages: coarse-grained pyrite-bearing quartz veins (stage I), fine-grained pyrite-quartzveinlets (stage II), multi-sulfides (stage III) and carbonate-quartz veinlets (stage IV). Ar-Ardating on mineral separates of stages I, II and III yields plateau ages of 142.9 +- 2.9 Ma, 132.2 +-2.6 Ma and 128.3 +- 6.2 Ma, respectively. Sericite separates from stage II assemblage also yield anAr-Ar isochron age of 132.6 +- 2.7 Ma, similar to the Ar-Ar plateau age. These results suggest thatthe Dongchuang gold deposit was mainly formed during 143-128 Ma, coinciding with the authors'geological observations and previous hypothesis. This ore formation is coeval with theregional-tectonic transition from collisional compression to extension, strongly showing that thedecompression-geothermal increase regime during compression-to-extension transition is the mostconducive geodynamic environment to orogenic-type gold mineralization.
文摘Orogenically-derived gold deposits of the Zhongchuan area in the western Qinling are distributed in the exo-contact thermal metamorphic zone. The country rocks hosting the deposits are predominantly of Devonian age with low-grade metamorphism and strong deformation with the ore deposits directly controlled by multi-level tectonic systems. Three types of inclusions from these deposits have been recognized: CO2-H2O, CO2-rich, and aqueous. The ore-forming fluids were mainly CO2-NaCl-H2O type characterized by rich CO2, low salinity, high temperature and immiscibility. Incorporated with earlier isotopic data, the regional geological setting and features of diagenesis and metallogeny, it can be concluded that the ore-forming fluids were derived from deep magma and mixed with meteoric and metamorphic water. The deposits formed during an intra-continent collisional orogeny, and some of the materials derived from the deep might have been involved in the ore-forming process.
基金the Youth Fund of the Chinese Academy of Geological Science (No.9011)
文摘Based on palaeomagnetic studies of the Precambrian gold deposits in the Xiong'ershan area, Henan Province, the authors infer that the ore-forming processes of the Beiling alteration-type gold ore deposit and the Dianfang breccia-type gold ore deposit started in the Proterozoic, and was superimposed by later mineralization, whereas the mineralization age of the Jiguanshan quartz- vein type gold ore deposit is Yanshanian.
文摘Studying the metallogenic age of Dapinggou gold deposit may provide important material not only for the study of metallization and the further prospecting of gold deposits but also for research into tectonic evolution in the Altun area. In this study, we used Rb-Sr isotopic dating method of fluid inclusion in the Au-bearing quartz, combining field investigation, REE, sulfur isotopes, lead isotopes, strontium isotopes and hydrogen-oxygen isotope, to determine the metallogenic age of the Dapinggou gold deposit. The only newly-discovered medium-sized gold deposit in the northern Altun area, Dapinggou gold deposit, is controlled by a ductile shear zone. It is characterized by mainly altered mylonite-types with a little K-feldspar quartz vein-types. Data from REE, sulfur isotopes, lead isotopes and strontium isotopes show that the source materials of the deposit were derived mainly from the metamorphic rocks. The data from the inclusion and hydrogen-oxygen isotope indicate that the ore-forming fluid came mainly from dynamic metamorphic water and partly from remelting magmatic water, with a little influence from meteoric water. The density of the ore-forming fluid is 0. 791 - 0. 971g/cm^3 and it contains 2.36 %-5.5 % salinity, The gold deposit was formed at 1.61-2.68 km below the surface at a temperature of 198--290 ℃ and a pressure of （420-700） × 10^5 Pa. The isotopic age from the Rb-Sr isochron of fluid inclusion in quartz is 487 Ma, which indicates that the mineralization occurred in the early Caledonian epoch. The study on the metallogenic age of Dapinggou gold deposit may provide important material not only for the study of metallization and the further prospecting of gold deposits but also for research into tectonic evolution in the Altun area.
文摘Based on detailed geologic study, the important role of structuring in the formation of gold deposits in the area is discussed with special reference to structural evolution. Syngenetic faulting contemporaneous with tectonic-volcanic events is thought to be responsible for providing the ore-forming material at depth. The lithofacies formed by highly alternating deposition of terrestrial and carbonate detritus is chemically characterized by the assemblage of Au-Sb-As,constituting a favorable source bed for the activation and enrichment of gold. This gold source bed has undergone four major stages of structural deformation, accompanied by multi-staged alteration and mineralization.
文摘Abstract This paper deals with characteristics of silicon isotope compositions and siliceous cathodoluminescence of host rocks, ores and hydrothermal silicified quartz of the Carlin-type ore deposits in the Yunnan-Guizhou-Guangxi triangle area. The study shows that primary silicified quartz is nonluminescent but quartz in host rocks and secondary silicified quartz are luminescent by the action of cathode rays. Correspondingly, silicon isotope compositions of host rocks, ores and hydro6thermal quartz veins are clearly distinguished. In strata from the Middle Triassic to the “Dachang” host bed, δ30Si of the host rocks ranges from 0.0% ?0.3%, while that of primary ore-forming silicified fluids from ?0.1% to ?0.4%; in the Upper Permian and Lower Carboniferous strata and Indosinian diabase host beds, δ30Si of the host rocks is from ?0.1% to ?0.2% and that of the primary silicified quartz veins from 0.3 % ?0.5 %. This pattern demonstrates the following geochemical mineralization process, primary ore-forming siliceous fluids migrated upwards quickly along the main passages of deep-seated faults from mantle to crust and entered secondary faults where gold deposits were eventually formed as a result of permeation and replacement of the siliceous ore-forming fluids into different ore-bearing strata. This gives important evidence for the fact that ore-forming fluids of this type of gold deposits were mainly derived from upper mantle differentiation and shows good prospects for deep gold deposits and geochemical background for large and superlarge gold deposits.
文摘In order to understand the mechanism(s) of gold precipitation in the anorthosite-hosted Sangchon gold deposits in the Hadong area, Korea, chemical speciation and reaction path calculations were accomplished by geochemical modeling. The modeling consisted of three-step procedures: reaction with anorthosite, then the simple cooling of the reacted fluid, and finally the boiling of metalliferous fluid. The principal vein minerals of the Sangchon deposits consist of quartz, sericite, kaolinite, pyrite, galena, chalcopyrite, sphalerite and acanthite. The sulfide mineralization is typically zoned from pyrite (preferentially at vein margins) to galena and sphalerite (toward vein center). Electrum is intimately associated with pyrite ± chalcopyrite and sphalerite. By comparing the results of modeling with the observed mineral assemblages and paragenesis, the most appropriate evolution path of ore fluids was suggested as follow: reaction of a single fluid with anorthosite at 300℃, then the isobaric cooling of the fluid at temperatures from 250° to 100℃, and then the boiling and cooling of the fluid due to the decrease of pressure and temperature. Calculations also show that all of the observed alteration minerals formed due to fluid-anorthosite interaction at early period, whereas most of sulfides and electrum were precipitated mainly due to cooling. The abundance of gold in veins depends critically on the ratio of total base metals plus iron to sulfide in the aqueous phase, because gold is transported as Au(HS) 2 -whose solubility is very sensitive to the sulfide activity. Our results of geochemical modeling generally fit to the observed mineral assemblages and mineral composition, indicating the usefulness of numerical simulation for elucidating the genesis of gold deposits.
文摘The depth is important for ore finding in Jiaodong gold deposit. However, many geologists are still discussing how to confirm the depth for the tectonic and metallogenesis formation. The authors of this paper propose a new method-the correction of metallogenic depth via its structure to calculate the depth. This method, based on the crust rock in a solid stress state, emphasizes the elastic pattern rather than the static fluid pattern. In addition, this method is more appropriate to the actual situation in the crust than the method of weight/special weight. The authors of this paper illustrating, with the Jiaodong gold deposit as an example, the metallogenic depth correction via structure conclude that the depth of the most deposits, lower than 4-6 km, is often 2.5 km. Therefore, the authors suggest that there exists a second enrichment belt and that ore resources are more potential at the belt of Jiaodong area. These results have been demonstrated by years of exploration.
