Abstract: With the discovery of rare metal deposits in large coal measures, wide attention has been paid to the study of trace elements in coal. However, rare element study in the northwest China coal measures is still limited. In this paper, we selected the eastern Junggar coalfield in northeastern Xinjiang as the research object to study the distribution, occurrence and enrichment mechanism of gallium in coal, by analyzing coal quality and trace element data. The results showed: (1) gallium is obviously enriched in the Middle Jurassic coal seams in the eastern Junggar coalfield, with Ga contents averaged at 20.7847.98 μg/g in twelve coal mines, which are higher than or close to the boundary grade of gallium in coal (30 μg/g). (2) the distribution regularity of gallium in coal is  apparent: on plane, gallium content is higher around the basin rim than in the center; in the northeastern and southwestern coalfields especially, gallium content is abnormally high (partly exceeding 60 μg/g) due to effect of the Kelameili and Bogda Mountains. In contrast, in the central coal mines (ZD10740, ZD10464, ZD10407 and ZD10841), gallium contents are gradually enriched from the edge to the center. Vertically, gallium contents in most of coal mines studied decrease upward from bottom in the Middle Jurassic coal seams, whereas affected by the early Yanshan movement, ZD10740 near the Bogda Mountain showed the opposite trend. And (3) kaolinite was the main carrier of gallium in coal, and gallium also partly existed in organic matters of coal. Gallium was transported to the sedimentary basin mainly in finegrained material form (colloid or organic complex), and accumulated under wet sedimentary conditions.

Key words:  eastern Junggar coalfield, Middle Jurassic coal seams, gallium, distribution regularity, occurrence, enrichment mechanism