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开展了利用飞秒激光剥蚀多接收等离子体质谱进行硫化物矿物中Pb同位素原位微区分析技术研究,采用高温活化活性炭过滤载气中的Hg,使得Hg背景信号降低了48%,进一步降低检出限,分析过程的分馏效应及质量歧视效应校正采用内标Tl和外标NIST SRM 610相结合方式进行.利用研究建立的方法分析了都龙锡锌铟多金属矿带中的黄铜矿、黄铁矿和闪锌矿中Pb同位素组成.结果表明,该矿区不同硫化物矿物间及同一种硫化物不同颗粒间的Pb含量差异可达1000多倍,黄铁矿具有相对较高的Pb含量,而闪锌矿的Pb含量则偏低.高Pb含量的黄铁矿具有变化小且相对均一的Pb同位素组成,而低Pb含量的闪锌矿的Pb同位素组成变化极大,一方面它可能较易受后期热液叠加作用而改变,另一方面由于闪锌矿中铅含量较低,则其中所含微量铀的影响显著加大,因而由铀放射性衰变随时间积累起来的放射成因铅也可能是造成其Pb含量和同位素组成分布范围较大的原因之一.Pb含量高于10 ppm的黄铜矿和闪锌矿颗粒显示了一致的Pb同位素分布,而Pb含量高于100 ppm的所有硫化物颗粒均具有误差范围内一致的Pb同位素组成,且与化学法得到的结果误差范围内吻合,表明本研究方法的数据可靠.本研究还表明,只有Pb含量相对较高的硫化物矿物中的Pb同位素组成才能较真实地记录其成矿物质来源.而Pb含量偏低的硫化物矿物中的Pb同位素组成则可能受样品中微量铀的影响而具有高放射成因铅同位素比值,也可能代表了后期交代流体改造后的Pb同位素组成.
Carried out the use of femtosecond laser ablation ICP-MS for Pb isotope analysis of sulfide minerals in situ micro-area analysis of high-temperature activated carbon filter carrier gas Hg, Hg background signal is reduced by 48%, and further reduce the detection The analysis of the fractionation effect and quality discrimination effect of the analysis process was carried out by using a combination of internal standard Tl and external standard NIST SRM 610. The chalcopyrite in the Du Long Tin Zinc Indium polymetallic ore zone was analyzed by the established method, Pyrite and sphalerite.The results show that the Pb content of different sulfide minerals and different particles of the same sulfide in this mining area can reach more than 1000 times, pyrite has a relatively high Pb content , While the Pb content of sphalerite is low.The pyrite with high Pb content has a small and relatively uniform variation of Pb isotopic composition, while the Pb isotopic composition of sphalerite with low Pb content varies greatly, on the one hand it may Which is more susceptible to the superimposition of later hydrothermal fluids. On the other hand, due to the low content of lead in sphalerite, the influence of trace amounts of uranium contained therein is significantly increased, and thus the radiation accumulated by the radioactive decay of uranium over time Lead may also be responsible for the large range of Pb and isotopic composition distributions. Chalcopyrite and sphalerite particles with Pb concentrations above 10 ppm show consistent Pb isotopic distribution with Pb levels above 100 ppm of all sulfide particles have the same Pb isotopic composition within the error range and are in agreement with the results of the chemical method, indicating that the data in this study are reliable.The study also shows that only sulfide with a relatively high Pb content Pb isotopic compositions of minerals can more accurately record the source of metallogenic materials.The Pb isotope composition of sulfide minerals with low Pb content may be affected by the trace amount of uranium in the samples and have a high ratio of radiogenic lead to lead isotope, It may also represent the alteration of Pb isotope compositions after the fluid replacement.