论文部分内容阅读
The Jinman deposit is a Ag-bearing copper vein deposit located at the north marginof the Lanping-Simao back-arc basin in West Yunnan. Systematic studies of fluid inclusions andstable isotopes are presented in this paper. The filling-replacement stage and the boiling-exhala-tive precipitation stage of mineralization took place at T1 = 140 - 280℃ and T2 = 94 - 204℃under pressure of (600 - 1200) ×105 Pa. The salinity of ore-forming solutions ranges from 5 wt%-20. 8 wt% (NaCl). Sulphide δ34S(CDT) values are in the rang of - 9.6‰ - + 11.03% witha range of 22. 66‰ showing an apparent “pagoda”-shaped distribution in histogram. Mean-while, the δ34S values of the various sulphides are consistent with the characters of isotope equi-librium fractionation, i. e., δ34SPy>δ34 SCp> δ34SBn. The TS/TOC ratios of the ores are widelyvariable between 0.16 and 5. 54 with no correlation of any kind can be established. Accirding to themodel of Ohmoto, the oxidation-reduction ratios of sulfur species in ore-forming solutions at the twomineralization stages were calculated to be R’1 = 2. 16×10(-17) and R’2 = 1. 55×104. δ13CCO2 (PDB)values obtained from fluid inclusions in calcite and quartz are between - 8.12‰ - - 3. 18‰, av-eraging - 5. 26‰, which are comparable with the isotopic composition of mantle-derived CO2.Inclusions in quartz yield δ13CCH4(PDB) between - 32. 11‰ and - 22. 04‰ (averaging- 26. 69‰),similar to that of methane in modern geothermal gases. For the ore-forming soutions, δ18OH2O(SMOW) values are between - 10. 57‰ and + 9. 77‰ and δDH2O(SMOW) are between - 51‰and - 135‰. Considering the effect of isotope exchange during waterrock reactions, most ofthe data are plotted along or close to the line defined by the reaction of meteoric water withclastic rocks, while a small part of the points fall near the reaction line of magmatic water withclastic rocks. In δ13C vs. δ18O diagram, the ore-forming soutions are plotted for the most partinto the mixing area between the meteoric fluid and the deep-seated fluid and partially on themixing line of P = 1.
The Jinman deposit is a Ag-bearing copper vein deposit located at the north margin of the Lanping-Simao back-arc basin in West Yunnan. Systematic studies of fluid inclusions and ready isotopes are presented in this paper. The filling-replacement stage and the boiling- exhala-tive precipitation stage of mineralization took place at T1 = 140-280 ° C and T2 = 94-204 ° C under pressure of (600-1200) x 105 Pa. The salinity of ore-forming solutions ranges from 5 wt% -20. 8% (NaCl). Sulphide δ34S (CDT) values are in the rang of - 9.6 ‰ - + 11.03% witha range of 22. 66 ‰ showing an apparent “pagoda” - shaped distribution in histogram. Mean-while, the δ34S values of the various sulphides are consistent with the characters of isotope equi-librium fractionation, ie, δ34SPy> δ34 SCp> δ34SBn. The TS / TOC ratios of theores are widely variable between 0.16 and 5. 54 with no correlation of any kind can be established. Accirding to themodel of Ohmoto, the oxidation-reduction ratios of sulfur species in ore-forming solutions at the twomineralization stages were calculated to be R’1 = 2. 16 × 10 (-17) and R’2 = 1. 55 × 104. δ13CCO2 (PDB) values obtained from fluid inclusions in calcite and quartz are between - 8.12 ‰ - - 3. 18 ‰, av-eraging - 5. 26 ‰, which are comparable with the isotopic composition of mantle-derived CO2.Inclusions in quartz yield δ13CCH4 (PDB) between - 32. 11 ‰ and - 22. 04 ‰ (averaging- 26. 69 ‰), similar to that of methane in modern geothermal gases. For the ore-forming soutions, δ18OH2O (SMOW) values are between -10.57 ‰ and + 9. 77 ‰ and δDH2O (SMOW) are between - 51 ‰ and - 135 ‰. Considering the effect of isotope exchange during waterrock reactions, most of the data are plotted along or close to the line defined by the reaction of meteoric water withclastic rocks, while a small part of the points fall near the reaction line of magmatic water with clastic rocks. In δ13C vs. δ18O diagram, the ore-forming soutions are plotted for the most parti nto the mixing area between the meteoric fluid and the deep-seated fluid and partially on themixing line of p = 1.