Hao Huidi, Jiu Bo, Huang Wenhui, Sun Mingzhe
Key Laboratory for Marine Reservoir Evolution and Hydrocarbon Abundance Mechanism, Beijing 100083, China; School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China.
Key Laboratory for Marine Reservoir Evolution and Hydrocarbon Abundance Mechanism, Beijing 100083, China; School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China; Peking University Ordos Research Institute of Energy, Ordos 017010, China.
Sci Total Environ. 2024 Oct 10;946:174362. doi: 10.1016/j.scitotenv.2024.174362. Epub 2024 Jun 30.
Niobium has been considered to be enriched in high-Al-Ga in north China coal and coal-hosted Nb(Ta)-Zr(Hf)-REY-Ga polymetallic deposits in the southwestern region of China. However, modes of occurrence and influencing factors of Nb in Al-Ga-rich coal in North China are rarely reported. This study investigated the distribution characteristics of Nb in the No.6 high-Al-Ga coal of the Jungar Coalfield in North China. The in-situ Nb concentration of selected minerals, including kaolinite, Ti-oxides, boehmite, and zircon, is further quantitatively characterized based on multiscale in-situ elemental analyses, including SEM-EDS and LA-ICP-MS spot and mapping analyses. The results showed that Nb is rich in the tonstein and mudstone partings among bulk samples and is highly concentrated in Ti-oxides, followed by zircon among the minerals. A certain amount of Nb is associated with kaolinite and boehmite with different modes of occurrence: vermicular kaolinite (65.94 ppm) > clastic kaolinite (25.43 ppm) > altered K-bearing kaolinite (18.11 ppm) > cryptocrystalline kaolinite (17.03 ppm) > clastic boehmite (9.08 ppm) > cryptocrystalline boehmite (7.97 ppm). The Nb-Nb/Ta and Zr/Hf-Nb/Ta ratios suggest that the primary source of Nb in the No.6 coal is the altered felsic volcanic ash and bauxite deposit. The high-Fe concentration in Ti-bearing minerals indicates that anatase may originate from the alteration of ilmenite with a process of Fe depletion and Nb enrichment. The enrichment of Nb in coal is attributed to the substitution of Nb for Ti in isomorphism in all Ti-oxides, high-Ti, and Ti-bearing minerals.
铌被认为在中国北方煤以及中国西南地区富铝 - 镓煤系铌（钽） - 锆（铪） - 稀土元素 - 镓多金属矿床中含量较高。然而，华北地区富铝 - 镓煤中铌的赋存状态及影响因素鲜有报道。本研究调查了华北准格尔煤田6号富铝 - 镓煤中铌的分布特征。基于多尺度原位元素分析，包括扫描电子显微镜 - 能谱仪（SEM - EDS）以及激光剥蚀电感耦合等离子体质谱（LA - ICP - MS）点分析和成像分析，进一步定量表征了选定矿物（包括高岭石、钛氧化物、勃姆石和锆石）中的原位铌浓度。结果表明，在块状样品中，铌在夹矸和泥岩夹层中含量较高，在矿物中高度富集于钛氧化物，其次是锆石。一定量的铌以不同赋存状态与高岭石和勃姆石相关联：蠕虫状高岭石（65.94 ppm）＞碎屑状高岭石（25.43 ppm）＞蚀变含钾高岭石（18.11 ppm）＞隐晶质高岭石（17.03 ppm）＞碎屑状勃姆石（9.08 ppm）＞隐晶质勃姆石（7.97 ppm）。铌 - 铌/钽和锆/铪 - 铌/钽比值表明，6号煤中铌的主要来源是蚀变的长英质火山灰和铝土矿矿床。含钛矿物中高铁浓度表明，锐钛矿可能源于钛铁矿的蚀变过程，伴随着铁的亏损和铌的富集。煤中铌的富集归因于在所有钛氧化物、高钛和含钛矿物中铌以类质同象形式替代钛。
