| 硒的矿物学、地球化学及成矿机制-以拉尔玛硒-金矿床和若干含硒建造为例 | |
温汉捷
| |
| 1999 | |
| Degree Grantor | 中国科学院地球化学研究所 |
| Place of Conferral | 中国科学院地球化学研究所 |
| Degree Name | 博士 |
| Degree Discipline | 地球化学，矿床地球化学 |
| Keyword | 硒矿物 含硒建造 含硒矿床 有机质有机质 有机成矿作用 改造作用 |
| Abstract | 以若干含硒矿床和含硒建造为例，系统研究了硒的矿物学、地球化学和成矿机制。从构造环境、岩性组合、元素组合、有机地球化学特征等方面系统阐述了含硒建造成的地质背景和地质地球化学特征。并且首次提出了“含硒建造”的概念。重点剖析了拉尔玛硒-金矿床的元素分布规律、矿物组合及硒的赋存状态，认为硒主要以有机结合态形式存在，提出了硒富集的热水沉积-有机质固定-后期改造-有机富集模式。 |
| Other Abstract | In this paper, taking mineralogy, geochemistry and mineralization of selenium as the main thread, and taking Laerma selenium-gold deposit and some selenium-bearing formations (SBFs) in china as samples, the deposit and SBFs are studied in detail. Main works include geological setting of mineralization, pre enrichment mechanism, forming condition and mineral assembly of selenium minerals, role of organic matters in the diagenetic and minerogenetic process, and redistribution of selenium in the later reforming. Achievements in this paper are shown as follow: The siliceous rock of the siliceous rock formation (SRF) in Laerma region is the result of hot water deposit with the special reference to the analysis of regional geology, tectonic environment, structure and texture of the siliceous rock, trace elements, REE elements, major elements, and Si, O isotope. Based on above all, it is put forward that the enrichment of multi-elements(Se、 Au、 U、 Cu、 Mo、 Sb、 PGE) is closely related to the genesis of the siliceous rock. It is summarized systematically about the selenium abundance and lithology dickite and stibnite. The study about the physics-chemical condition forming selenium minerals show that the temperature forming selenium minerals is 200 ℃ approximately, the fugacity logfse_2 and logfs_2 range -8.05 ～ -10.5 respectively. On the fugacity-fugacity diagram, the mineral assembly in the Laerma selenium-gold deposit is in equilibrium and stable. High fse_2, fse_2/fs_2 ratio, fo_2, low temperature and neutral-acidic condition are greatly advantage to formation of selenium minerals. At the same time a great deal of statistics show probability to form selenium minerals is maximal while S ＜ 0.5%, C_(org)(organic carbon) ＜1.5% and Se ＞ 10 * 10~(-6), which may be as a distinguished sign in the practice. The study of organic geochemistry to the Laerma selenium-gold deposit including the organic carbon abundance, souble organism, biological fossil, kerogen, confirms the role and status of organic matters in the minerogenetic process. By the study to the dispersed solid organic matter- kerogen of ores, the occurrence of selenium is firstly shown in this paper. In Laerma deposit selenium has the highest value of enrichment coefficient in kerogen, coming next are Ni, Ba, Mo, Au and Bi. 75% of selenium in the deposit is organic-bonded, with inorganic-bonded selenium accounting for the remaining 25%. The organic-inorganic proportion of selenium is varying depending on the stage of mineralization. The mode of occurrence of inorganic-bonded selenium includes independent minerals (selenides), isomorphism and adsorption on clay minerals. Based on biochemical evidence, organic-bonded ratio of different stage of mineralization, theoretical calculations and infrared spectra, the organic-bonded selenium probably forms covalent bonds with oxygen-bearing radicals or combines with organism by substituting for sulfur Geological facts, trace elements, REE elements, S, Pb, C isotopes and organic geochemical characters show the ore-forming material are derived from the Taiyangding group of the low Cambrian formation. The mineralization age assembly in four selenium-bearing formations (SBFs), including Laerma SBF, Ziyang SBF, Northwest Hunan SBF and West Hubei SBF. By the study on organic geochemistry and biomakers of above four SBFs, it is obvious that main organism contain the low and aquatic homonemeae in all these SBFs, and some biomakers indicate sedimentary environment may mainly be close and anoxic condition. At the same tie, based on geological facts, author considers that reductive sedimentary environment is advantageous to growth and preservation of homonemeae, and enrichment of selenium is closely relative to bloom of homonemeae. Associating mainly with the genesis of siliceous rock, origin of selenium may be related to sillcalite, however fixing of selenium may be closely related to organism in the SBF. It is noticeable that the concept-"Selenium-bearing formation (SBF)" is firstly brought forward in this paper, defined as: a set of lithology assembly containing the anomaly of selenium and other elements with the special character of the space-time distribution and lithology assemnly. The distributing rule of selenium is analyzed in detail to the Laerma selenium-gold deposit. As a whole, whether from the cross direction or from the vertical direction, the distribution of selenium is consistent with the distribution of gold, and there occur the correlatability between selenium and other elements, such as As, Hg, U, Sb et al. A few tens of selenides have been identified by microscopic and microprobe studies in the deposits. It seems that no similar example has ever known in the world in which so great number of selenium minerals are found. Tiemannite is the most important selenide in Laerma, others include S-antimonselite, Se-stibioluzonite, ferroselite in addition to small amounts of clausthalite, antimonselite, Se-Ni minerals and berzelianite. These selenides, associated mainly with quartz-barite veins formed in later stages of mineralization, may occur as:(1) Intergrowth with native gold, and/or stibnite; (2) Interstice or fissure fillings between or in quartz, barite and stibnite; and (3) Inclusions in barite, quartz, calculated by U-Pb, Ar-Ar, Pb-Pb isotope is approximately between 117Ma and 49Ma, corresponding to the late Yanshan period-Xishan period. The ore-forming fluid is mainly composed of the brine water of the middle-low temperature and middle-low salinity with a lot of organic gas. H-O isotope data implies that the ore-forming fluid is derived from the atmospheric water. With the above studies on the geology-geochemistry of the Laerma selenium-gold deposit, an ore-forming model is proposed of hydrothermal sedimentation-adsorption by organic matters- later reforming-enrichment by organic matters. Lastly, the geological setting and geochemical features of selenium-bearing deposits and classical selenium-bearing formations in china are summed up in this paper. Conditions of forming selenium-bearing formation include ① Enrichment of selenium is commonly formed in the rift, deep basin and syngenetic deep fault; ② Epoch of enrichment of selenium mainly is in the Cambrian and Permain, that is the stage of the abroad upgroth of the black shales in china; ③ There is the sillcalite of hydrothermal sedimentation in the SBF; ④ There is abundant organic matter that mainly is sapropel type in the SBF. Meanwhile, conditions of forming selenium-bearing deposits may include: ① There occur source beds (selenium-bearing formations) formed with the restriction of space-time and lithology; ② Selenium-bearing deposits occur in black shales; ③ Abundant organic matters take a share in whole minerogenetic process; ④ Enrichment of selenium is commonly formed in the rift, deep basin and syngenetic deep fault; ⑤ There is reforming mineralization in the last stage. |
| Pages | 116 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.gyig.ac.cn/handle/352002/3526 |
| Collection | 研究生_研究生_学位论文 矿床地球化学国家重点实验室 |
| Recommended Citation GB/T 7714 | 温汉捷. 硒的矿物学、地球化学及成矿机制-以拉尔玛硒-金矿床和若干含硒建造为例[D]. 中国科学院地球化学研究所. 中国科学院地球化学研究所,1999. |
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