| 其他摘要 | In recent ten years, with the application of multiple collector inductively coupled plasma-mass spectrometry (MC-ICP-MS) and the improvement of analytical methods, researches on non-traditional stable isotopes, such as Cu, Zn, Fe, Se, Mo, Cd, Cr and Hg, have developed rapidly. These isotopes have been widely applied to cosmochemistry, mineral deposit, environmental science, marine science, and planetology. Since Ge isotope is a new nontraditional isotope, the accumulated Ge isotope literatures are quite limited, and application of Ge isotope in ore genesisis study is close to empty. Two typical Ge-enriched ore deposits were selected as the objects of this study, based on systemically studies on the analytical methods, fractionationand tracing theories of Ge isotopes, try to explore the mechanism of germanium isotope fractionation of complex systems and their the main controlling factors, the coupling relationship between Ge isotope fractionation and extraordinary enrichment of ore-forming elements. The main findings obtained were listed as follows: In this thesis, we carried out detailed studies of Ge isotopes. We developed the analytical method of Ge isotopes in geological samples such as Ge-bearing lignite, sandstones, and sulfides, particularly assessed the preparation method to ensure the application range of Ge isotopes. Taking Wulantuga Ge deposit of Inner Mongolia as an example, Ge isotopes of Ge-rich coal were used to discuss the enrichment mechanism of Ge and the fractionation mechanism of Ge isotopes, providing direct evidences for unusual enrichement of Ge in Ge-rich coal deposit. Germanium isotopes of sulfides from the Jinding and Huize Pb-Zn deposits of Yunnan and Shanshulin and Tianqiao Pb-Zn deposits of Guizhou were also used to discuss the fractionation mechanism of Ge during Pb-Zn mineralization processes, accumulating the Ge isotope data of sulfides particularly sphalerite from different types of Pb-Zn deposits and providing a new orientation for studying the deposit. Based on these, the main conclusions are listed as follows. (1) The chemical purification and preconcentration method of Ge istopes in geological samples was first developed at home. The recoveries of Ge in sulfides during one step anion-exchange separation were quantitatively assessed by the standard-addition method and reach one hundred percents. Germanium yields a recovery of >95% when the weights of pyrite, chalcopyrite, sphalerite, and galena are less than 150 mg. The proposed method can effectively removed most matrix elements. But amounts of Sb were remained in Ge-bearing solutions acquired by dissolution of sphalerite and galena, which was possibly due to similar partition coefficients of Sb and Ge in acid media. (2) Single element addition method was used to evaluate the effects of the matrix elements such as Cu, Sn, W, Zn, Pb, and Sb on the recoveries of Ge. There are no obvious isotope biases for Ge-bearing solutions containing significant amounts of Cu, Sn, and W. However, δ74Ge values show obvious shifts if the solutions contain high Zn, Pb, and Sb, which was possibly attributed to suppression of germane formation that fractionates Ge isotopes. Therefore, the method of single step anion resin purification method is suitable for Ge isotope analysis of natural sulfides determined by HG-MC-ICP-MS. (3) The proposed method of determining Ge isotopes by hydride generation (HG) coupled with MC-ICP-MS and mass discrimination correction by sample-standard bracketing (SSB) yielded a good reproducibility. The δ74Ge values of Spex standard solutions are consistent with those of previous studies. Ge isotope composition of Merck standard solutions was first measured. The calculated δ74Ge value of sphalerite standard based on doping experiments is indistinguishable from those of sphalerite without doping. (4) The lignite samples of Wulantuga Ge deposit display large variations in Ge isotope composition that reach 9.63‰. The relative en |
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