陆相热水沉积与超大型锗矿床的成因——以临沧锗矿床为例

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	陆相热水沉积与超大型锗矿床的成因——以临沧锗矿床为例
其他题名	Continental Hydrothermal sedimentation and the genesis of superlarge germanium deposit: taking lincang germanium deposit as an example
	戚华文
	2002
学位授予单位	中国科学院地球化学研究所
学位授予地点	中国科学院地球化学研究所
学位名称	博士
学位专业	矿床地球化学
关键词	褐煤硅质岩花岗岩热水沉积成矿机理锗矿床临沧滇西
摘要	该文以产在滇西临沧县境内、以二云母花岗岩为在底的帮卖含煤碎屑岩盆地中的临沧超大型锗矿床（包括大寨和中寨两个矿床）为例,利用化学全分析、元素分析、ICP-MS、X射线衍射、透射电子显微镜、傅立叶变换红外光谱、同位素质谱等多种分析方法和手段,系统研究了临沧锗矿床不同含煤段中褐煤、第一含煤段中的层状硅质岩、薄层含碳硅质灰岩的岩石化学、微量元素、稀土元素和碳、氧同位素的组成特征.在调查清楚临沧锗矿床中褐煤、层状硅质岩与基底的二云母花岗岩关系的基础上,结合模拟实验研究结果,初步探讨了临沧超大型锗矿床的成因.
其他摘要	As a typical dispersed element, independent mineralization of germanium is rarely known for a long time. But two superlarge germanium deposits, hosted in coal seams (the Lincang germanium deposit and the Wulantuga germanium deposit ) , with unusual concentration, scale and independent commercially- worthwhile value, have been discovered recently in China. The Lincang germanium deposit, include Dazhai germanium deposit and Zhongzhai germanium deposit, is located in the coal-bearing clastic Bangmai basin with two-mica granites as the basement rock in the Lincang county, western Yunnan Province. Using chemical analysis, elemental analysis, ICP-MS, X-ray diffraction, TEM-EDX, FTIR spectra and isotope analysis techniques, we systematically studied the major element, trace element, rare earth element, δ ~(13)C andδ ~(18)O composition of lignite, siliceous rock and carboniferous siliceous limestone samples in different coal-bearing cycles of Lincang germanium deposit. Based on the investegation of the relationship between lignite, siliceous rock and the two-mica granite in the basement, and comparison with the result of simulative experiments, the genesis of the Lincang germanium deposit is discussed. The conclusions have been summarized as follows: 1.Germanium mainly concentrated at the top of the coal seams and in the deep coal seams in the first coal-bearing cycle (N_(1b)~2) of the Dazhai germanium deposit, while it mainly concentrated at the bottom of the coal seams and in the shallow coal seams in N_(1b)~2 of Zhongzhai germanium deposit. The relation between siliceous rocks, carboniferous sileceous rocks and germanium mineralization is obvious, when they appeared, the content of germanium in lignite obviously increased. The distribution of germanium-rich sections in coal seams, syndepositional faults and siliceous rocks are accordant with each other. 2. The geochemical commonness and difference was found in the lignite of the first (N_(1b)~2 and the second (N_(1b)4) coal-bearing cycle. Nb and HREE obviously concentrated in the germanium-rich coal. Nb can be regarded as the indicating element of germanium mineralization. Reductive condition is propitious to germanium mineralization. The trace elements and REEs of germanium-rich coals, non-germanium coals and granitic clastic rocks came from two-mica granite in the basement. Except the similar material source with non-germanium coals , another source trace elements and REEs mixed into the germanium-rich coals. Non-germanium coals in the second coal-bearing cycle (N_(1b)~4 was formed under ordinary sedimentary peat-swamp phase environment, but germanium-rich coals in Nib2 was formed under rapid falling peat-swamp phase environment, in which there were hydrothermal water activities. 3.TEM-EDX has been used for the first time to study the existing form of germanium in coal, results show that germanium in high concentration samples mainly occurs in huminite, not in minerals (include pyrite. kaolinite, ilite, gypsum and iron-bearing mineral etc.) . FTIR spectra studies demonstrate that germanium is mainly complex with O. C. N and H of different function-groups in coal. The concentration of function-groups drops during germanium mineralization. Abundant hydrothermal sedimentary structures and plant frag fossil have been found for the first time in the layered siliceous rocks. The geochemical characters of the layered siliceous rocks and the thin-bedded carboniferous siliceous limestone in Nib2 are similar to hydrothermal sediments. So. the layered siliceous rocks and the thin-bedded carboniferous siliceous limestone are hydrothermal sediments. Their trace element and REE composition are similar to those of the two-mica granites in the basement, imply that their trace element and REE came from the basement two-mica granites. The hydrothermal water activity and coal-forming process happened basically at the same time. The interaction between peat, different coal with respect to vitrinite reflectance, and germanium was studied at temperatures from 25 to 100°C in acid (pH=2.96) to alkaline (pH=12.08) solutions. Results indicate that high temperature, high initial germanium concentration and less mature degree of coal is propitious to the absorb of germanium over a wide range of pH (4~10). The adsorption of lignite is as a function of temperature. After the interaction, the pH of the germanium-bearing solution increased and the IR spectrum of coal changed. Germanium is possibly complex with the organic matter in peat and coal. 6.The genesis of Lincang germanium deposit belongs to hydrothermal sedimentation. The germanium hosted in coal seams of Lincang germanium deposit came from the basement granites, was brought by hydrothermal water symbolized by siliceous rock and carboniferous siliceous limestone. The hydrothermal water, caused by syndepositional faults, leached abundant germanium from the basement granites, and brought them into the coal-forming basin, where germanium been Fixed by organic matters in coal, at last leaded to the germanium mineralization in coal of the Lincang germanium deposit.
页数	101
语种	中文
文献类型	学位论文
条目标识符	http://ir.gyig.ac.cn/handle/352002/3606
专题	研究生_研究生_学位论文矿床地球化学国家重点实验室
推荐引用方式 GB/T 7714	戚华文. 陆相热水沉积与超大型锗矿床的成因——以临沧锗矿床为例[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,2002.

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