Abstract: Surface waters in the Pine Creek Geosyncline (located in Australia's “Top End”, defined as the area of Australia north of 15 degrees S) are characterized by their low carbonate buffering capacity. These waters are buffered by silicate weathering and hence are slightly acidic, ranging in pH from 4.0 to 6.0. The Pine Creek Geosyncline contains most of the Top Ends' economic mineral deposits and characteristically shows no correlation between carbonate minerals and sulfidic orebodies hosting gold deposits (unlike uranium deposits). Thus many gold mines do not have ready access to carbonate minerals for buffering acid mine drainage (AMD). It is possible that locally available fast-weathering silicate minerals may be used to buffer AMD seeps. The buffering intensity of silicate minerals exceeds that of carbonate minerals, but their slow dissolution kinetics has ensured that these materials have received little attention in treating AMD. In addition, carbonate mineral dissolution is retarded when contacted with intense AMD solutions due to the formation of surface coatings of iron minerals. The lower pH range of silicate mineral dissolution may prevent the formation of such coatings. The Pine Creek Geosyncline consists of a complex geochemistry, and a number of fast-weathering silicate minerals have been noted in various areas. The difficulty in assessing such minerals for use in buffering AMD is the lack of kinetic data available under conditions prevalent AMD (i.e., low pH solutions saturated with aluminium and silica). This study sets out to evaluate the applicability of using such minerals to treat AMD surface seeps.

Abstract: Vor dem Hintergrund einer planmäßigen Tagebauentwicklung muss der das Gewinnungsfeld in Nord-Süd-Richtung durchquerende Fluss Inde Ende 2005 bergbaulich in Anspruch genommen werden. Als Ersatz wurde auf Grundlage des Planfeststellungsbeschlusses vom 10.09.1998 eine neue Inde auf einer Länge von rd. 12 km erstellt. Rund 10 km der neuen Inde liegt innerhalb des Tagebaufeldes. Hierzu musste eine Flusslandschaft angelegt werden. Im Gegensatz bisher anthropogen geprägten Inde, ist eine naturnahe und weiträumige Flusslandschaft vorgesehen. Die Gestaltung soll, in Verbindung mit den zahlreichen eingebrachten Landschaftselementen wie Flutmulden, Altarmansätzen und Kolke, eine artenreiche und ökologisch hochwertige Auenlandschaft ermöglichen. Die Flutung der neuen Inde erfolgt auf Grundlage eines dreiphasigen Gewässerumschlusskonzeptes. Im Anschluss an die Flutung soll ein Monitoring- Programm zur Dokumentation der hydrodynamischen, morphologischen und landschaftsökologischen Entwicklung der Indeflur durchgeführt werden. Against the background of the scheduled eastward development of the Inden opencast mine, the Inde river which runs there must make way for mining operations at the end of 2005. Prior to this, as a replacement for the riverbed, which is some 4.5 km long, a riverscape has had to be created as a bypass in the west, mainly within the scope of rehabilitation measures. The model built for this purpose based on historical records provides for a close-to-nature and spacious riverscape with hand- and soft-wood meadows, unlike the anthropogenically marked Inde of today, with a meandering mean water bed. This design, in conjunction with the many installed landscape elements, like flood hollows, creeks and potholes, aims at creating a diverse and ecologically high-quality meadow landscape. The main factors impacting the river's route were the opencast mine's geometry and progress, as well as the planned and existing utilization of the land surfaces outside the opencast field. Besides these constraints, there were stipulated vertical points due to hydraulic requirements. The Inde plains, taking account of the planned route, were created on the basis of a design template, which provides for a stable level, a sealing layer and a cultivatable meadow substrate layer. In addition, the meadow substrate layer protects the sealing layer from erosion thanks to its medium- and coarse-grained gravel content. The Inde was constructed in the opencast field within the scope of rehabilitation in spreader operations, meaning that it was possible to dump the material to be installed in line with the design template and given elevations. The flooding of the 'new' Inde was based on a three-phase waterway rerouting concept and provided for increasing discharge quantities. This enabled a bottom covering layer to be formed successively, and ailowed the aquatic fauna to gently adapt to the changed living conditions and further seed material to be flushed in.