GEOCHEMISTRY OF AUTOCHTHONOUS AND HYPAUTOCHTHONOUS SIDERITE DOLOMITE COAL-BALLS (FOORD SEAM, BOLSOVIAN, UPPER CARBONIFEROUS), NOVA-SCOTIA, CANADA

The 11-13 m thick Foord Seam in the fault-bounded Stellarton Basin, No va Scotia, is the thickest seam from the Euramerican floral province k nown to contain coal-balls. In addition to the first discovery of auto chthonous coal-balls in the Foord Seam, Nova Scotia, its shale parting also contains hypautochthonous coal-balls with histologically preserv ed plant structures. The coal-ball discovery helps fill a stratigraphi c gap in coal-ball occurrences in the upper Carboniferous (Bolsovian) of Euramerica. The autochthonous and hypautochthonous coal-balls have a similar mineralogical composition and are composed of siderite (81-1 00%), dolomite-ankerite (0-19%), minor quartz and illite, and trace am ounts of 'calcite'. Similar is also their permineralizing mineralogy, which consists of dolomite-ankerite and siderite. Their low pyrite con tent and carbonate mineralogy, and nonmarine origin, differentiates th e Foord Seam coal-balls from other Euramerican coal-ball occurrences. A preliminary geochemical model, which is based on oxygen and carbon i sotopic data, indicates that siderite in both the autochthonous and hy pautochthonous coal-balls is of very early diagenetic (nonmarine) orig in from C-13-enriched bicarbonate derived from bacterial methanogenesi s of organic matter.