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
Lamprophyres, widely distributed in the Laowangzhai gold orefield, Yunnan province, China, and closely related to gold mineralization in time and space, can be distinguished into three kinds: the fresh (weakly altered...Lamprophyres, widely distributed in the Laowangzhai gold orefield, Yunnan province, China, and closely related to gold mineralization in time and space, can be distinguished into three kinds: the fresh (weakly altered ), the altered, and the mineralized lamprophyres. These lamprophyres in the orefield are similar in the range of BEE contents and REE patterns, but definitely different in parameters of LRE/HRE, NLa/Yb etc. The geochemistry of REE in fresh lamprophyre shows flat the rock is a product of different partial melting of the enriched mantle. Calculation results of mass balance of REE activity regularity in the process of alteration and mineralization of the lalnprophyres in the orefield shows that the altering fluids and mineralizing fluids contain REE, and these fluids are mainly [he products of mantle degassing and magma degassing during the lamprophyric magmatism.展开更多
This paper systematically reports geochemical data of lamprophyres which are temporally andspatially related to Au mineralization in the Laowangzhai gold deposits, Yunnan Province. Majorelements show that lamprophyres...This paper systematically reports geochemical data of lamprophyres which are temporally andspatially related to Au mineralization in the Laowangzhai gold deposits, Yunnan Province. Majorelements show that lamprophyres in the orefield are alkalic series and potassic calc-alkaline lam-prophyres. Chondrite-normalized transition element patterns of the lamprophyres are "W" shapedwhich suggest that the rocks are mantle-derived. The lamprophyres are enriched in large ionlithophile elements (LlLE ), high field strength elements (HFSE ) and rare earth elements(REE), and have high 87Sr/86Sr but low 143Nd/144Nd ratios. All the characteristics above and cal-culation modelling suggest that the source of the lamprophyres is incompatible element-enrichedmetasomatic mantle.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
The Laowangzhai super-large gold orefield, which is situated in northern Mt. Ailaotectonic zone, Yunnan Province, is a typical gold orefield where lamprophyres are temporallyand spatially related to gold mineratizatio...The Laowangzhai super-large gold orefield, which is situated in northern Mt. Ailaotectonic zone, Yunnan Province, is a typical gold orefield where lamprophyres are temporallyand spatially related to gold mineratization. Major element data show that lamprophyres in theorefield are of alkalic series and can be divided into potassic and K-rich calc-alkaline lamprophyres. The rocks are enriched in rare-earth elenlents as compared with the primary mantle andmid-ocean ridge basalts(MORB). Modelled calculations by the least squares method of Petrological Mixing show that the mantle source for the lamprophyres is enriched in rare-earth elements. The geotectonic development of western Yunnan, Sr and Nd isotopic compeitions, incompatible element patterns and linear programing calculations indicate that the fluids were de-rived from dehydration of submaine sediments which are enriched in ALK, LREE and incompatible elements and then were carried to mantle wedges as a result of plate subduction. That isthe main factor leading to the formation of a metasomatic fertile mantle in the area studied.展开更多
Widely-distributed lamprophyres in the Laowangzhai gold deposit were associated closely with gold ores. Phlogopite ^(40)Ar/^(39)Ar dating suggests that the emplacement age of lampro-phyric magma ranges from (30.8±...Widely-distributed lamprophyres in the Laowangzhai gold deposit were associated closely with gold ores. Phlogopite ^(40)Ar/^(39)Ar dating suggests that the emplacement age of lampro-phyric magma ranges from (30.8±0.4) to (34.3±0.2) Ma, and gold mineralization took place at (26.4±0.2) Ma. PGE geochemical tracing indicates that gold in the gold deposit did not come from the primitive lamprophyric magma. The tempo-spatial paragenesis between lamprophyres and mesothermal gold deposits along the Jinsha-Red River belt may be attributed to the fact that they formed in the same tectonic setting.展开更多
The essential shallow crust structural factors controlling the formation of Laowangzhai gold deposit include favorable tectonic and regional structural site, the release site of a great deal of the earth energy, favor...The essential shallow crust structural factors controlling the formation of Laowangzhai gold deposit include favorable tectonic and regional structural site, the release site of a great deal of the earth energy, favorable ore controlling structure system, abundant and favorable source rocks for gold, ductile shearing, abundant minerogenetic materials source in extensive crust and mantle. And the essential deep seated crust mantle structure factors dominating the formation of the ore deposit include intracrustal low velocity len, high velocity bodies in the lower part of middle crust and lower crust, the steps on the slope of Moho, connecting site of mantle rises, the crust mantle transition layer, upwelling of asthenosphere and the low velocity plume. It is concluded that the fundamental reason that controls the formation of Laowangzhai superlarge gold deposit lies in the coupling between deep and shallow crust mantle structure factors controlling the formation of the deposit and their coupling with the lithospheric evolution and geological event.展开更多
THE Laowangzhai superlarge gold deposit was found in 1984. Although studies on regional structure, geology of deposits and lamprophyres, which are temporally and spatially related to gold mineralization,have been carr...THE Laowangzhai superlarge gold deposit was found in 1984. Although studies on regional structure, geology of deposits and lamprophyres, which are temporally and spatially related to gold mineralization,have been carried out, the views on the source of ore-forming materials have been different. Thisnote summarized the characteristics of lead isotopic composition of the deposits, and probed further intothe source of ore-forming materials. 1 Geological setting The Laowangzhai gold deposit, located in the north of the Ailaoshan fault zone, consists of Donggualin and Laowangzhai ore block. The strata in the orefield include Paleozoic （Pz<sub>3</sub>） epimetamorphic ma-展开更多
Lamprophyres are widely spread over the Laowangzhai gold orefield in northern Mt. Ailao structure zone, Yunnan Province. Lamprophyres in the orefield are temporally and spatially related to gold mineralization. Lampro...Lamprophyres are widely spread over the Laowangzhai gold orefield in northern Mt. Ailao structure zone, Yunnan Province. Lamprophyres in the orefield are temporally and spatially related to gold mineralization. Lamprophyres in the orefield have anomalous Sr and Nd isotopic compositions, e.g. the 87Sr/ 86Sr ratios (0.706 665-0.707 960, the 87Sr/ 86Sr ratio of sample YLW-44 is 0.709 041) are higher than the modern value of the original mantle (0.704 5), the 143Nd/ 144Nd ratios (0.512 463-0.512 551) are lower than the modern value of the original mantle (0.512 638), and the calculated values ε Sr>0 (28.1-63.7) and ε Nd<0 (-1.34--3.07). The results of investigation indicate that lamprophyres in the Laowangzhai gold orefield with anomalous Sr and Nd isotopic compositions would not be produced as a result of contamination of the primary magma with the isotopic features of MORB by the crust materials high 87Sr/ 86Sr ratios and low 143Nd/ 144Nd ratios in the processes of rising or in the magma chamber, but the result of metasomatism of source mantle.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the National Outstanding Young Scientist Foundation !49625304 the Ministry of Science and Technologyof China!95-pre-39
文摘Lamprophyres, widely distributed in the Laowangzhai gold orefield, Yunnan province, China, and closely related to gold mineralization in time and space, can be distinguished into three kinds: the fresh (weakly altered ), the altered, and the mineralized lamprophyres. These lamprophyres in the orefield are similar in the range of BEE contents and REE patterns, but definitely different in parameters of LRE/HRE, NLa/Yb etc. The geochemistry of REE in fresh lamprophyre shows flat the rock is a product of different partial melting of the enriched mantle. Calculation results of mass balance of REE activity regularity in the process of alteration and mineralization of the lalnprophyres in the orefield shows that the altering fluids and mineralizing fluids contain REE, and these fluids are mainly [he products of mantle degassing and magma degassing during the lamprophyric magmatism.
文摘This paper systematically reports geochemical data of lamprophyres which are temporally andspatially related to Au mineralization in the Laowangzhai gold deposits, Yunnan Province. Majorelements show that lamprophyres in the orefield are alkalic series and potassic calc-alkaline lam-prophyres. Chondrite-normalized transition element patterns of the lamprophyres are "W" shapedwhich suggest that the rocks are mantle-derived. The lamprophyres are enriched in large ionlithophile elements (LlLE ), high field strength elements (HFSE ) and rare earth elements(REE), and have high 87Sr/86Sr but low 143Nd/144Nd ratios. All the characteristics above and cal-culation modelling suggest that the source of the lamprophyres is incompatible element-enrichedmetasomatic mantle.
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The Laowangzhai super-large gold orefield, which is situated in northern Mt. Ailaotectonic zone, Yunnan Province, is a typical gold orefield where lamprophyres are temporallyand spatially related to gold mineratization. Major element data show that lamprophyres in theorefield are of alkalic series and can be divided into potassic and K-rich calc-alkaline lamprophyres. The rocks are enriched in rare-earth elenlents as compared with the primary mantle andmid-ocean ridge basalts(MORB). Modelled calculations by the least squares method of Petrological Mixing show that the mantle source for the lamprophyres is enriched in rare-earth elements. The geotectonic development of western Yunnan, Sr and Nd isotopic compeitions, incompatible element patterns and linear programing calculations indicate that the fluids were de-rived from dehydration of submaine sediments which are enriched in ALK, LREE and incompatible elements and then were carried to mantle wedges as a result of plate subduction. That isthe main factor leading to the formation of a metasomatic fertile mantle in the area studied.
基金the Chinese National Key Project for Basic Research on Tibetan Plateau (G1998040800). the National Natural Science Foundation of China (Grant Nos. 49972026. 49472100). the National Climbing Project (95-Y-25), CAS's Projects (KZCX2-101, KZ952-J1-408) and
文摘Widely-distributed lamprophyres in the Laowangzhai gold deposit were associated closely with gold ores. Phlogopite ^(40)Ar/^(39)Ar dating suggests that the emplacement age of lampro-phyric magma ranges from (30.8±0.4) to (34.3±0.2) Ma, and gold mineralization took place at (26.4±0.2) Ma. PGE geochemical tracing indicates that gold in the gold deposit did not come from the primitive lamprophyric magma. The tempo-spatial paragenesis between lamprophyres and mesothermal gold deposits along the Jinsha-Red River belt may be attributed to the fact that they formed in the same tectonic setting.
文摘The essential shallow crust structural factors controlling the formation of Laowangzhai gold deposit include favorable tectonic and regional structural site, the release site of a great deal of the earth energy, favorable ore controlling structure system, abundant and favorable source rocks for gold, ductile shearing, abundant minerogenetic materials source in extensive crust and mantle. And the essential deep seated crust mantle structure factors dominating the formation of the ore deposit include intracrustal low velocity len, high velocity bodies in the lower part of middle crust and lower crust, the steps on the slope of Moho, connecting site of mantle rises, the crust mantle transition layer, upwelling of asthenosphere and the low velocity plume. It is concluded that the fundamental reason that controls the formation of Laowangzhai superlarge gold deposit lies in the coupling between deep and shallow crust mantle structure factors controlling the formation of the deposit and their coupling with the lithospheric evolution and geological event.
文摘THE Laowangzhai superlarge gold deposit was found in 1984. Although studies on regional structure, geology of deposits and lamprophyres, which are temporally and spatially related to gold mineralization,have been carried out, the views on the source of ore-forming materials have been different. Thisnote summarized the characteristics of lead isotopic composition of the deposits, and probed further intothe source of ore-forming materials. 1 Geological setting The Laowangzhai gold deposit, located in the north of the Ailaoshan fault zone, consists of Donggualin and Laowangzhai ore block. The strata in the orefield include Paleozoic （Pz<sub>3</sub>） epimetamorphic ma-
文摘Lamprophyres are widely spread over the Laowangzhai gold orefield in northern Mt. Ailao structure zone, Yunnan Province. Lamprophyres in the orefield are temporally and spatially related to gold mineralization. Lamprophyres in the orefield have anomalous Sr and Nd isotopic compositions, e.g. the 87Sr/ 86Sr ratios (0.706 665-0.707 960, the 87Sr/ 86Sr ratio of sample YLW-44 is 0.709 041) are higher than the modern value of the original mantle (0.704 5), the 143Nd/ 144Nd ratios (0.512 463-0.512 551) are lower than the modern value of the original mantle (0.512 638), and the calculated values ε Sr>0 (28.1-63.7) and ε Nd<0 (-1.34--3.07). The results of investigation indicate that lamprophyres in the Laowangzhai gold orefield with anomalous Sr and Nd isotopic compositions would not be produced as a result of contamination of the primary magma with the isotopic features of MORB by the crust materials high 87Sr/ 86Sr ratios and low 143Nd/ 144Nd ratios in the processes of rising or in the magma chamber, but the result of metasomatism of source mantle.
