Οργανική γεωχημεία και πετρολογία του λιγνιτικού κοιτάσματος Αμυνταίου

Abstract

The contribution of lignite to the total electric power output of Greece exceeds 75%. Most greek lignite deposits are located in the Florina-Ptolemais- Kozani basin, a large intensively exploited area, in northern Greece. This area is exploited by opencast mining and feeds nearby lignite-fired power stations. The elongated intermontaine Florina-Ptolemais-Kozani basin is a NNW-SSE trending graben system, that extends over a distance of 250 km from Bitola, in the Former Yugoslavian Republic of Macedonia to Servia, southeast of Kozani, Greece. The basement consists of metamorphic schists in the west and crystalline limestone in the east. The Amynteo basin is part of this graben, that opened in the late Miocene and was divided into sub-basins in the Pleistocene, and consists of rythmic alternations of lignite beds and lacustrine and fluvial sediments. Sampling represents the vertical and lateral differentiation of lignite beds in Amynteo field (Chapter 1). Coal petrological investigation along with proximate and elemental analyses were undertaken (Chapter 2) in order to determine the petrographic characteristics of the Amynteo lignites and their depositional environment. Thirty-eight samples (representing different lignite beds of the Amynteo deposit) were collected from a borehole. The Amynteo lignites have an euulminite B reflectance of Rr=0.21%, and in terms of lithotype belong to matrix soft brown coals. Huminite is the most abundant maceral group, and consists mostly of humodetrinite. Inertinite has relatively low percentages whereas liptinite concentrations are rather high. Ternary plots and facies indices were employed in order to reconstruct the palaeoenvironment. The depositional environment of the Amynteo-Apofysis lignites is not definitely ascribed to a forest swamp or a reed marsh environment. The high ash content of the analysed samples is a clear indication of a topogenous setting. Low TPI and high GI values are observed. High alkalinity and strongly reducing conditions may be inferred from the presence of syngenetic (framboidal) pyrite, the low TPI values which indicate high bacterial activity, and thus high pH conditions, and the preservation of gastropod shells and chlorophyllinite. High GI values indicates a constant influx of calcium rich waters into the coal swamp. The Apofysis lignite deposit may be interpreted to be autochthonous to hypoautochthonous. The peat accumulation was governed by a high groundwater level (wet telmatic to limno-telmatic facies) and a moderate subsidence rate. The high liptinite content of the samples makes them suitable for liquefaction and gasification and may also be useful in chemical industry due to the high extract yields.