The Gejiu tin polymetallic deposits are located in the southeastern part of Yunnan Province in China. A detailed electronic microprobe study has been carried out to document geochemical compositions of tourmalines fro...The Gejiu tin polymetallic deposits are located in the southeastern part of Yunnan Province in China. A detailed electronic microprobe study has been carried out to document geochemical compositions of tourmalines from the deposits. The results indicate a systematic change of mineral geochemical compositions, which might be used as a mineral geochemical tracer for post-magmatic hydrothermal fluid, basin fluid and their mixture. The tourmalines from granite are schori with Fe/ （Fe＋Mg） ratios of 0.912-1.00 and Na/（Na＋Ca） ratios of 0.892-0.981. Tourmalines as an inclusion in quartz from the ore bodies are dravite with Fe/（Fe＋Mg） ratios of 0.212-0.519 and Na/（Na＋Ca） ratios of 0.786--0.997. Tourmalines from the country rocks are dravite with Fe/（Fe＋Mg） ratios of 0.313--0.337 and Na/（Na＋Ca） ratio of 0.599-0.723. Tourmalines from cassiterite-tourmaline veins that occur in crannies within the country rocks show distinct optical zoning with alternate occurrence of dravite and schorl, Fe/（Fe＋Mg）=0.374-0.843, Na/（Na＋Ca）=0.538-0.987. It suggests that schorl in granite and dravite in carbonatite are related to magmatic fluid and basin fluid respectively. When magmatic fluid rose up and entered into crannies of the country rocks, consisting mainly of carbonatite, basin fluid would be constantly added to the magmatic fluid. The two types of fluid were mixed in structural crannies of the sedimentary basin accompanied with periodic geochemical oscillations to form material records in chemical composition zonings of tourmalines.展开更多
The Longtoushan hydrothermal gold deposit is located in the southwestern region of the Dayaoshan Uplift.Tourmaline is widespread in the Longtoushan gold deposit and is mainly distributed in the rhyolite porphyry and a...The Longtoushan hydrothermal gold deposit is located in the southwestern region of the Dayaoshan Uplift.Tourmaline is widespread in the Longtoushan gold deposit and is mainly distributed in the rhyolite porphyry and associated cryptoexplosive breccia. The spatial distribution of tourmaline enrichment is similar to that of the gold orebody. Feldspar has been largely replaced by tourmaline in the rhyolite porphyry and cryptoexplosive breccia.Electron microprobe analysis revealed that tourmalines in the Longtoushan deposit belong mainly to the alkali group and partly to the X-vacant group; they mostly fell in the schorl-dravite series field. Two distinct sets of dominant substitutions were observed: MgFe_(-1) and Al□(NaR2+)-1,where R = Fe, Mg. In addition, minor substitutions include(CaMg)(NaAl)_(-1) and FeAl_(-1). The calculated d11 B value for the mineralizing fluids ranged from-12.8 to-9.7%,which is typical of S-type granites, and boron-enriched fluids predominantly derived from rhyolitic melt. Part of the tourmaline from the rhyolite porphyry crystallized during the magmatic-hydrothermal stage, whereas most tourmalines from the deposit formed in the post-magmatic hydrothermal stage. The tourmalines were deposited from a relatively reduced and acidic fluid system, and the gold predominantly precipitated during the post-magmatic hydrothermal stage in the Longtoushan deposit.展开更多
Tourmaline occurs as a minor but important mineral in the alteration zc,ne of the Archean orogenic gold deposit of Guddadarangavanahalli （G.R.Halli） in the Chitradurga greenst^ne belt of the western Dharwar craton, ...Tourmaline occurs as a minor but important mineral in the alteration zc,ne of the Archean orogenic gold deposit of Guddadarangavanahalli （G.R.Halli） in the Chitradurga greenst^ne belt of the western Dharwar craton, southern India. It occurs in the distal alteration halo of the G.R.Halli golcl deposit as （a） clusters of very fine grained aggregates which form a minor constituent in the natrix of the altered metabasalt （AMB tourmaline） and （b） in quartz-carbonate veins （vein tourmaline）. ~[＇he vein tourmaline, based upon the association of specific carbonate minerals, is further grouped as （i） albite-tourmaline-ankerite-quartz veins （vein-1 tourmaline） and （ii） albite-tourmaline-calcite-quartz veins （vein-2 tourmaline）. Both the AMB tourmaline and the vein tourmalines （vein-I and vein-2） belong to the alkali group and are clas- sified under schorl-dravite series. Tourmalines occurring in the veins are zoned while the AMB tour- malines are unzoned. Mineral chemistry and discrimination diagrams 1eveal that cores and rims of the vein tourmalines are distinctly different. Core composition of the ve：n tourmalines is similar to the composition of the AMB tourmaline. The formation of the AMB tourmaline and cores of the vein tour- malines are proposed to be related to the regional D1 deformational event associated with the emplacement of the adjoining ca. 2.61 Ga Chitradurga granite whilst rims of the vein tourmalines vis-a- vis gold mineralization is spatially linked to the juvenile magmatic accretion （2.56-2.50 Ga） east of the studied area in the western part of the eastern Dharwar craton.展开更多
The occurrences of excess ^40Ar within a hydrothermal tourmaline is discussed in term of the analysis data of syngenetic muscovite and tourmaline from the Lushui hydrothermal tin-tungsten deposit in western Yunnan, Ch...The occurrences of excess ^40Ar within a hydrothermal tourmaline is discussed in term of the analysis data of syngenetic muscovite and tourmaline from the Lushui hydrothermal tin-tungsten deposit in western Yunnan, China, using the ^40Ar-^39Ar stepwise heating technique. About 80% excess ^40 Ar was released in the last step when the tourmaline was fused, corresponding to a release of only -3% ^39 Ar （K）, which indicates that most excess ^40 Ar was held in the mineral lattice rather than in the channels parallel to the Z-axis. This suggests that the excess ^40 Ar was incorporated during crystallization and not diffused into the tourmaline during the post-crystallization history.展开更多
基金supported by "Technology of Comprehensive Prospecting and Exploitability for Elements in Crisis Mines" (Grant No. 2008EG115074)a special fund managed by the Ministry of Science and Technology for technical R&D of scientific research institutions, and the Key Laboratory of Ore Deposit Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences
文摘The Gejiu tin polymetallic deposits are located in the southeastern part of Yunnan Province in China. A detailed electronic microprobe study has been carried out to document geochemical compositions of tourmalines from the deposits. The results indicate a systematic change of mineral geochemical compositions, which might be used as a mineral geochemical tracer for post-magmatic hydrothermal fluid, basin fluid and their mixture. The tourmalines from granite are schori with Fe/ （Fe＋Mg） ratios of 0.912-1.00 and Na/（Na＋Ca） ratios of 0.892-0.981. Tourmalines as an inclusion in quartz from the ore bodies are dravite with Fe/（Fe＋Mg） ratios of 0.212-0.519 and Na/（Na＋Ca） ratios of 0.786--0.997. Tourmalines from the country rocks are dravite with Fe/（Fe＋Mg） ratios of 0.313--0.337 and Na/（Na＋Ca） ratio of 0.599-0.723. Tourmalines from cassiterite-tourmaline veins that occur in crannies within the country rocks show distinct optical zoning with alternate occurrence of dravite and schorl, Fe/（Fe＋Mg）=0.374-0.843, Na/（Na＋Ca）=0.538-0.987. It suggests that schorl in granite and dravite in carbonatite are related to magmatic fluid and basin fluid respectively. When magmatic fluid rose up and entered into crannies of the country rocks, consisting mainly of carbonatite, basin fluid would be constantly added to the magmatic fluid. The two types of fluid were mixed in structural crannies of the sedimentary basin accompanied with periodic geochemical oscillations to form material records in chemical composition zonings of tourmalines.
基金supported by the Project of Innovation-driven Plan in Central South University (Project No. 2015CX008)the Fundamental Research Funds for the Central Universities of Central South University (Project No. 2015zzts071)
文摘The Longtoushan hydrothermal gold deposit is located in the southwestern region of the Dayaoshan Uplift.Tourmaline is widespread in the Longtoushan gold deposit and is mainly distributed in the rhyolite porphyry and associated cryptoexplosive breccia. The spatial distribution of tourmaline enrichment is similar to that of the gold orebody. Feldspar has been largely replaced by tourmaline in the rhyolite porphyry and cryptoexplosive breccia.Electron microprobe analysis revealed that tourmalines in the Longtoushan deposit belong mainly to the alkali group and partly to the X-vacant group; they mostly fell in the schorl-dravite series field. Two distinct sets of dominant substitutions were observed: MgFe_(-1) and Al□(NaR2+)-1,where R = Fe, Mg. In addition, minor substitutions include(CaMg)(NaAl)_(-1) and FeAl_(-1). The calculated d11 B value for the mineralizing fluids ranged from-12.8 to-9.7%,which is typical of S-type granites, and boron-enriched fluids predominantly derived from rhyolitic melt. Part of the tourmaline from the rhyolite porphyry crystallized during the magmatic-hydrothermal stage, whereas most tourmalines from the deposit formed in the post-magmatic hydrothermal stage. The tourmalines were deposited from a relatively reduced and acidic fluid system, and the gold predominantly precipitated during the post-magmatic hydrothermal stage in the Longtoushan deposit.
文摘Tourmaline occurs as a minor but important mineral in the alteration zc,ne of the Archean orogenic gold deposit of Guddadarangavanahalli （G.R.Halli） in the Chitradurga greenst^ne belt of the western Dharwar craton, southern India. It occurs in the distal alteration halo of the G.R.Halli golcl deposit as （a） clusters of very fine grained aggregates which form a minor constituent in the natrix of the altered metabasalt （AMB tourmaline） and （b） in quartz-carbonate veins （vein tourmaline）. ~[＇he vein tourmaline, based upon the association of specific carbonate minerals, is further grouped as （i） albite-tourmaline-ankerite-quartz veins （vein-1 tourmaline） and （ii） albite-tourmaline-calcite-quartz veins （vein-2 tourmaline）. Both the AMB tourmaline and the vein tourmalines （vein-I and vein-2） belong to the alkali group and are clas- sified under schorl-dravite series. Tourmalines occurring in the veins are zoned while the AMB tour- malines are unzoned. Mineral chemistry and discrimination diagrams 1eveal that cores and rims of the vein tourmalines are distinctly different. Core composition of the ve：n tourmalines is similar to the composition of the AMB tourmaline. The formation of the AMB tourmaline and cores of the vein tour- malines are proposed to be related to the regional D1 deformational event associated with the emplacement of the adjoining ca. 2.61 Ga Chitradurga granite whilst rims of the vein tourmalines vis-a- vis gold mineralization is spatially linked to the juvenile magmatic accretion （2.56-2.50 Ga） east of the studied area in the western part of the eastern Dharwar craton.
基金Financial supports came from the National Natural Science Foundation of China （40472048） ；the Chinese Academy of Sciences （KZCX2-SW117 and GIGCX-0301）.
文摘The occurrences of excess ^40Ar within a hydrothermal tourmaline is discussed in term of the analysis data of syngenetic muscovite and tourmaline from the Lushui hydrothermal tin-tungsten deposit in western Yunnan, China, using the ^40Ar-^39Ar stepwise heating technique. About 80% excess ^40 Ar was released in the last step when the tourmaline was fused, corresponding to a release of only -3% ^39 Ar （K）, which indicates that most excess ^40 Ar was held in the mineral lattice rather than in the channels parallel to the Z-axis. This suggests that the excess ^40 Ar was incorporated during crystallization and not diffused into the tourmaline during the post-crystallization history.
