摘要
Analyses of fluid\|inclusion leachates from ore deposits show that Na/Br ratios are within the range of 75-358 and Cl/Br 67-394, respectively, and this variation trend coincides with the seawater evaporation trajectory on the basis of the Na/Br and Cl/Br ratios. The average Cl/Br and Na/Br ratios of mineralizing fluids are 185 and 173 respectively, which are very close to the ratios (120 and 233) of the residual evaporated seawater past the point of halite precipitation. It is suggested that the original mineralizing brine was derived from highly evaporated seawater with a high salinity. However, the inclusion fluids have absolute Na values of \{69.9\}-\{2606.2\} mmol kg\+\{-1\} and Cl values of \{106.7\}-\{1995.5\} mmol kg\+\{-1\}. Most of the values are much less than those of seawater: Na, 485 mmol kg\+\{-1\} and Cl, 566 mmol kg\+\{-1\}, respectively; the salinity measured from fluid inclusions of the deposits ranges from \{2.47 wt%\} to \{15.78 wt%\} NaCl equiv. The mineralizing brine has been diluted. The \{δ\{\}\+\{18\}O\} and δD values of ore\|forming fluids vary from \{-8.21‰\} to \{9.51‰\} and from \{-40.3‰\} to \{-94.3‰\}, respectively. The δD values of meteoric water in this region varied from \{-80‰\} to \{-100‰\} during the Jurassic. This evidenced that the ore\|forming fluids are the mixture of seawater and meteoric water. Highly evaporated seawater was responsible for leaching and extracting Pb, Zn and Fe, and mixed with and diluted by descending meteoric water, which resulted in the formation of ores.
Analyses of fluid-inclusion leachates from ore deposits show that Na/Brratios are within the range of 75 -358 and Cl/Br 67-394, respectively, and this variation trendcoincides with the seawater evaporation trajectory on the basis of the Na/Br and Cl/Br ratios. Theaverage Cl/Br and Na/Br ratios of mineralizing fluids are 185 and 173 respectively, which are veryclose to the ratios ( 120 and 233) of the residual evaporated seawater past the point of haliteprecipitation. It is suggested that the original mineralizing brine was derived from highlyevaporated seawater with a high salinity. However, the inclusion fluids have absolute Na values of69. 9 -2606. 2 mmol kg^(-1) and Cl values of 106. 7 - 1995. 5 mmol kg^(-1). Most of the values aremuch less than those of seawater; Na, 485 mmol kg^(-1) and Cl, 566 mmol kg^(-1), respectively; thesalinity measured from fluid inclusions of the deposits ranges from 2.47 wt% to 15. 78 wt% NaClequiv. The mineralizing brine has been diluted. The δ ^(18)O and Δd values of ore-forming fluidsvary from -8. 21 per thousand to 9. 51 per thousand and from -40.3 per thousand to -94.3 perthousand, respectively. The Δd values of meteoric water in this region varied from-80 per thousandto-100 per thousand during the Jurassic. This evidenced that the ore-forming fluids are the mixtureof seawater and meteoric water. Highly e-vaporated seawater was responsible for leaching andextracting Pb, Zn and Fe, and mixed with and diluted by descending meteoric water, which resulted inthe formation of ores.
基金
ThisresearchprojectwasfundedbytheNationalNaturalScienceFoundationofChina (No .4 0 1 72 0 39)
