Occurrence of some valuable elements in the unique ‘high-aluminium coals’ from the Jungar coalfield, China

Abstract

In China, a unique type of coal with extremely high aluminium (Al) content commonly occurs in the southern region of the Yinshan Oldland, Jungar Basin. The typical Al2O3 content in the coal ash is ~45%, and exceeds 60% in some cases. This type of coal forms a league of its own and is named as ‘high-Al coal’. This high-Al coal, not only contains unusually high level of Al but also has high concentrations of Li, Ga, and REY (REE+Y). All these elements (i.e. Al, Li, Ga, REY) with high concentrations in this type of coal are very valuable source to various industries and therefor make perfect economic sense and add extra benefits into coal mines if they can be recovered by beneficiation processes.The mineral compositions in these coals mainly consist of kaolinite, boehmite, chlorite-group minerals, along with minor amounts of quartz, calcite, pyrite, siderite and amorphous clay materials. The Al and rare elements show different patterns of distribution and affinity relationships with organic and inorganic matter. The strong peraluminous granites and moyite from the Yinshan Oldland may be the main source of the Al and rare elements in the coals. Bauxite from the Benxi Formation may also be another source for the Al and rare elements in the coal of the Jungar coalfield.