Based on petrological studies of the wall rocks, mineralizing rocks, ores and veins from the Laowangzhai gold deposit, it is discovered that along with the development of silication, carbonation and sulfidation, a kin...Based on petrological studies of the wall rocks, mineralizing rocks, ores and veins from the Laowangzhai gold deposit, it is discovered that along with the development of silication, carbonation and sulfidation, a kind of black opaque ultra-microlite material runs through the spaces between grains, fissures and cleavages. Under observations of the electron microprobe, scanning electronic microscopy and energy spectrum, this kind of ultra-microlite material is confirmed to consist of ultra microcrystalline quartz, silicate, sulfides and carbonates, as well as rutile, scheelite and specularite （magnetite）, showing characters of liquation by the analyses of SEM and energy spectrum. The coexistence of immiscibility and precipitating co-crystallization strongly suggests that the mineralizing fluid changed from the melt to the hydrothermal fluid. Combined with the element geochemical researches, it is realized that the ultra-microlite aggregate is the direct relics of the mantle fluid behaving like a melt and supercritical fluid, which goes along with the mantle-derived magma and will escape from the magma body at a proper time. During the alteration process, the nature of the mantle fluid changed and it is mixed with the crustal fluid, which are favorable for mineralization in the Loawangzhai gold deposit.展开更多
Based on the petrological studies of wall rocks, mineralized rocks, ores and veins from the Laowangzhai gold deposit, it is discovered that with the development of silification, carbonation and sulfidation, a kind of ...Based on the petrological studies of wall rocks, mineralized rocks, ores and veins from the Laowangzhai gold deposit, it is discovered that with the development of silification, carbonation and sulfidation, a kind of black opaque ultracrystalline material runs through the space between grains and amphibole cleavages, which is the product of fast condensing consolidation with magma mantle fluids turning into hydrothermal crustal fluids in the process of mineralization and alteration. It is thought that the water in ore-forming fluids mainly derived from magmatic water through research on H-O isotopes, and C as well as S isotopic compositions, has clear mantle-derived characteristics, and rock (mine) stones contain high 87Sr/86 Sr ratios, low 143Nd/144 Nd ratios and high 206Pb/204 Pb ratios, which also reflects the ore-forming fluids were derived from the metasomatically enriched mantle. In combination with the features of H-O-C-S isotopes and Sr-Nd-Pb isotopes described above, the ore-forming fluids of the Laowangzhai gold deposit in the northern part of the Ailao Mountains were derived mainly from the deep interior of the mantle, and their properties were transformed from magma fluids to hydrothermal fluids in the course of metasomatism and alteration, which initiated crust-mantle contamination simultaneously to be in favor of 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
Three special types of xenoliths have recently been found in an aegirine-augite syenite porphyry in Liuhe, Yunnan, China. Petrographical, petrochemical, electron microprobe, and scanning electron microscopy studies in...Three special types of xenoliths have recently been found in an aegirine-augite syenite porphyry in Liuhe, Yunnan, China. Petrographical, petrochemical, electron microprobe, and scanning electron microscopy studies indicate that pure calcite xenocrysts and quartz-bearing topaz pegmatite xenoliths result from the degassing of mantle fluids during their migration, and that black microcrystalline iron-rich silicate-melt xenoliths are the product of the extraction of mantle fluids accompanying degassing and are composed dominantly of quartz, chlorite, and iron-rich columnar and sheet silicate minerals with characteristic minerals, such as native iron, apatite, and zircon. According to the bulk-rock chemical and mineral compositions and crystallization states, the microcrystalline melt xenoliths are not the product of conventional magmatism, and especially the existence of native iron further proves that the xenoliths were mantle fluid materials under reduction or anoxic conditions. The study of the special xenoliths furnishes an important deep-process geochemical background of polymetallic mineralization in different rocks and strata in the study area.展开更多
: This paper, taking the finely disseminated gold deposits in southwestern Guizhou and northwestern Guangxi as examples, discusses the difference between the occurrence of primary ores and that of oxidized ores, analy...: This paper, taking the finely disseminated gold deposits in southwestern Guizhou and northwestern Guangxi as examples, discusses the difference between the occurrence of primary ores and that of oxidized ores, analyzes the occurrence mechanism in terms of crystallochemistry and geochemistry, and especially studies the chemical model for supergene leaching transformation of clay minerals in the two types of ores. This study proposes a new idea for dressing and smelting technology for primary gold ores.展开更多
基金supported by the National Natural Science Foundation of China (Grants No. 40473027 and 40773031)the Foundation of Doctoral Supported by the Ministry of Education (20105122110010 and 20115122110005)+1 种基金the Foundation of Open Subjects of State Key Laboratory for Mineral Deposits Research,Nanjing University (14-08-3)the Project of the State Key(Preparation Support) Disciplines of Mineralogy,Petrology and Mineral Deposit Geology of Sichuan Province (SZD0407)
文摘Based on petrological studies of the wall rocks, mineralizing rocks, ores and veins from the Laowangzhai gold deposit, it is discovered that along with the development of silication, carbonation and sulfidation, a kind of black opaque ultra-microlite material runs through the spaces between grains, fissures and cleavages. Under observations of the electron microprobe, scanning electronic microscopy and energy spectrum, this kind of ultra-microlite material is confirmed to consist of ultra microcrystalline quartz, silicate, sulfides and carbonates, as well as rutile, scheelite and specularite （magnetite）, showing characters of liquation by the analyses of SEM and energy spectrum. The coexistence of immiscibility and precipitating co-crystallization strongly suggests that the mineralizing fluid changed from the melt to the hydrothermal fluid. Combined with the element geochemical researches, it is realized that the ultra-microlite aggregate is the direct relics of the mantle fluid behaving like a melt and supercritical fluid, which goes along with the mantle-derived magma and will escape from the magma body at a proper time. During the alteration process, the nature of the mantle fluid changed and it is mixed with the crustal fluid, which are favorable for mineralization in the Loawangzhai gold deposit.
基金supported by the National Natural Science Foundation of China (Grant Nos. 40773031 and 40473027)the Ph.D. Programs Foundation of Ministry of Education of China (Grant Nos. 20105122110010 and 20115122110005)the Project of the State Key (Preparation Support) Disciplines of Mineralogy, Petrology and Mineral Deposit Geology of CDUT (Grant No. SZD0407)
文摘Based on the petrological studies of wall rocks, mineralized rocks, ores and veins from the Laowangzhai gold deposit, it is discovered that with the development of silification, carbonation and sulfidation, a kind of black opaque ultracrystalline material runs through the space between grains and amphibole cleavages, which is the product of fast condensing consolidation with magma mantle fluids turning into hydrothermal crustal fluids in the process of mineralization and alteration. It is thought that the water in ore-forming fluids mainly derived from magmatic water through research on H-O isotopes, and C as well as S isotopic compositions, has clear mantle-derived characteristics, and rock (mine) stones contain high 87Sr/86 Sr ratios, low 143Nd/144 Nd ratios and high 206Pb/204 Pb ratios, which also reflects the ore-forming fluids were derived from the metasomatically enriched mantle. In combination with the features of H-O-C-S isotopes and Sr-Nd-Pb isotopes described above, the ore-forming fluids of the Laowangzhai gold deposit in the northern part of the Ailao Mountains were derived mainly from the deep interior of the mantle, and their properties were transformed from magma fluids to hydrothermal fluids in the course of metasomatism and alteration, which initiated crust-mantle contamination simultaneously to be in favor of 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.
基金supported by National Natural Science Foundation of China grant 40473027 and 40773031Foundation of Open Subjects of the State Key Laboratory of Geological Processes and Mineral Resources of the China University of Geosciences grant GPMR0509 and GPMR200705the Project of the State Key(Preparation Support)Disciplines of Mineralogy,Petrology and Mineral Deposit Geology of Sichuan Province.
文摘Three special types of xenoliths have recently been found in an aegirine-augite syenite porphyry in Liuhe, Yunnan, China. Petrographical, petrochemical, electron microprobe, and scanning electron microscopy studies indicate that pure calcite xenocrysts and quartz-bearing topaz pegmatite xenoliths result from the degassing of mantle fluids during their migration, and that black microcrystalline iron-rich silicate-melt xenoliths are the product of the extraction of mantle fluids accompanying degassing and are composed dominantly of quartz, chlorite, and iron-rich columnar and sheet silicate minerals with characteristic minerals, such as native iron, apatite, and zircon. According to the bulk-rock chemical and mineral compositions and crystallization states, the microcrystalline melt xenoliths are not the product of conventional magmatism, and especially the existence of native iron further proves that the xenoliths were mantle fluid materials under reduction or anoxic conditions. The study of the special xenoliths furnishes an important deep-process geochemical background of polymetallic mineralization in different rocks and strata in the study area.
文摘: This paper, taking the finely disseminated gold deposits in southwestern Guizhou and northwestern Guangxi as examples, discusses the difference between the occurrence of primary ores and that of oxidized ores, analyzes the occurrence mechanism in terms of crystallochemistry and geochemistry, and especially studies the chemical model for supergene leaching transformation of clay minerals in the two types of ores. This study proposes a new idea for dressing and smelting technology for primary gold ores.
