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
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
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 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.
