凡口铅锌矿床同位素地球化学证据

Isotope Geochemical Evidence of the Fankou Lead and Zinc Deposit

对凡口铅锌矿床不同成矿阶段进行矿物包裹体温度、硫和铅同位素测定，获得成矿第Ⅰ阶段温度为300±50℃，第Ⅱ、Ⅲ阶段温度为250±50℃；并获得矿床硫化物的S同位素组成为2．1‰～26．5‰，具有δ^34SPy〉δ^34SSp〉δ^34SCn；第Ⅰ阶段硫化物的硫同位素组成随赋存层位由老到新硫同位素有逐渐减小趋势；第Ⅱ阶段硫化物的δ^34S为14．3‰～23．8‰；第Ⅲ阶段硫化物的δ^34S为5．7‰～15．7‰，具有从早阶段至晚阶段硫同位素组成变化范围从大至小的减小趋势。分析获得68件铅同位素数据，其中硫化物的^206Pb／^204Pb比值为18．023-18．847；^207Pb／^204Pb比值为15．700-15．820；^208Pb／^204Pb比值为38．056-39．796。灰岩全岩的^206Pb／^204Pb比值为18．230-18．860；^207Pb／^204Pb比值为15．640～16．000；^208Pb／^204Pb比值为38．714～39．760。辉绿岩的^206Pb／^204Pb比值为18．570～18．650；^207Pb／^204Pb比值为15．260～15．620；^208Pb／^204Pb比值为38．650～38．960。第Ⅰ阶段占δ^18OH2O为12．3‰～13．1‰，δD为-50．2‰～-61．5‰；第Ⅱ阶段δ^18OH2O为-2．4‰～＋10．8‰，δD为-50．2‰～-63．2‰；第Ⅲ阶段占δ^18OH2O为-4．9‰～-14．3‰，δD为-59．0‰～-61．0‰。

The determination of mineral inclusions for their temperature, sulfur and lead isotopes at different ore- forming stages in the Fankou lead and zinc detx）sit shows that the temperatures are 300 ± 50℃ at the first stage and 250 ± 50℃ at the second and third stages. The isotope comtx）sitions are 2.1‰-26.5‰, with δ^34Spy〉δ34SSP〉δ^34SGn. The isotope compositions of sulfides at the first stage tend to decrease from the older to younger strata. δ^34S values are 14.3‰ -23.8‰ for sulfides at Stage Ⅱ , and δ^34S are 5.7‰- 15.7‰ for sulfides at Stage Ⅰ with the tendency of varying in a decreasing range and becoming smaller in value. The lead isotope data obtained from 68 samples are 18. 023 - 18.847, ^207Pb/^204Pb ratios are 15. 700 - 15. 820, and ^208Pb/^204Pb ratios are 38. 056- 39. 796. ^206Pb/^204Pb ratios of the whole rock of limestone are 18. 230-18. 860,^207Pb/^204Pb ratios are 15. 640-16. 000, and ^208Pb/^204Pb ratios are 38. 714-39. 760. ^206Pb/^204Pb ratios of diabase are 18. 570 - 18. 650, ^207Pb/^204Pb ratios are 15. 260- 15. 620, and ^208Pb/^204Pb ratios are 38. 650-38. 960. δ18OH2O values of the first stage are 12.3‰- 13.1‰, and δD are - 50.2‰ - 61.5‰. δ^18OH2O of the second stage are - 2.4‰- ＋ 10.8‰ ,and δD are - 50.2‰ - - 63.2‰. δ^18OH2O of the third stage are - 4.9‰ - - 14.3‰, and δD are - 59.0‰ - - 61.0‰.