The No. 6 Coal-bed from the Heidaigou Mine, Jungar Coalfield, Inner Mongolia is a super-large Ga deposit. The dominant carrier of Ga is boehmite in coal. The study of coal facies may provide genetic enrichment information of Ga and its carrier (boehmite) in the Ga deposit. On the basis of study on coal petrology and mineralogy, it was found that the No. 6 Coal-bed from the Heidaigou Mine of Jungar was enriched in inertinites and the microlitho-types were dominated by clarodurite. The maceral morphological features and association indicate that the coal-bed was formed in a dry sedimentary environment or in a periodic dry sedimentary environment caused by the alternating variations of groundwater level. The optimum conditions for the enrichment of Ga and its particular carrier (boehmite) were dominated by four transitional conditions: (1) the upper delta plain which was the transitional zone between alluvial and lower delta plains, (2) the transitional zone between the dry and wet forest swamps, being slightly apt to the dry one, (3) the transitional tree density between the thick and loose ones, and (4) the low moor that was the transitional zone between two high moors during peat accumulation.
DAI ShiFeng REN DeYi LI ShengSheng ZHAO Lei ZHANG Yong
Mineralogy and geochemistry of the four main workable coal seams (No.6, No.7, No.8, and No.11) of Late Permian age from the Songzao Coalfield, Chongqing, Southwest China, were examined using in- ductively coupled plasma-mass spectrometry (ICP-MS), X-ray fluorescence spectrometry (XRF), cold-vapor absorption spectrometry (CV-AAS), ion-selective electrode (ISE), scanning electron mi- croscopy equipped with an energy-dispersive X-ray spectrometer (SEM-EDX), and X-ray diffraction analysis (XRD). The results showed that the main workable No.8 Coal that accounts for about 60% of the total coal reserves in the Songzao Coalfield was not enriched in hazardous trace elements. The No.11 Coal has high concentrations of alkaline elements, Be (9.14 μg/g), Sc (12.9 μg/g), Ti (9508 μg/g), Mn (397 μg/g), Co (23.7 μg/g), Cu (108 μg/g), Zn (123 μg/g), Ga (32 μg/g), Zr (1304 μg/g), Nb (169 μg/g), Hf (32.7 μg/g), Ta (11.4 μg/g), W (24.8 μg/g), Hg (0.28 μg/g), Pb (28.1 μg/g), Th (24.1 μg/g), and rare earth elements (509.62 μg/g). The concentration of Nb and Ta in the No. 11 Coal is higher than the industrial grade, and their potential utilization should be further studied. Besides pyrite, quartz, calcite, and clay minerals, trace minerals including chalcopyrite, marcasite, siderite, albite, mixed-layer clay minerals of illite and smectite, monazite, apatite, anatase, chlorite, and gypsum were found in the No.11 Coal. It should be noted that alabandite of hydrothermal origin and anatase occurring as cement were identi- fied in coal. In addition, the clayey microbands derived from alkaline volcanic ashes were identified in the coal. The dominant compositions of these clayey microbands were mixed-layer clay minerals of illite and smectite, which were interlayered with organic bands. The modes of occurrence of alkaline volcanic ash bands indicate that the volcanic activities were characterized by the multiple eruptions, short time interval and small scale for each eruption during peat accumulation. The alkaline volcanic a
DAI ShiFeng1,2, ZHOU YiPing3, REN DeYi1, WANG XiBo1, 2, LI Dan1, 2 & ZHAO Lei1, 2 1 State Key Laboratory of Coal Resources and Safe Mining (China University of Mining and Technology), Beijing 100083, China
