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Department of Economic Development, Jobs, Transport and Resources, DSDBI The second and third authors are funded by the Australian Government Research Training Program (RTP) and the GHERG scholarship programme.
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"Indicator" slates have long been considered to represent a useful exploration guide for turbidite-hosted mesothermal lode gold mineralization in central Victoria. This assumption has been based on an apparent close spatial relationship between high gold grades and the proximity of thin, commonly pyritic and carbon-rich marker units, Detailed studies in a number of gold deposits throughout central Victoria, however, reveal that highest gold grades do not necessarily coincide with the presence of carbonaceous units. In many places where gold mineralization is associated with carbon-rich matter, the high C accumulations are the result of epigenetic remobilization during hydrothermal alteration and ore genesis. Petrographic, geochemical, and stable isotope IC. O, Si investigations into the origin and nature of the carbonaceous matter-mainly amorphous bitumens and pyrobitumen of organic origin, with biological fragments and rare graphite of both detrital and metamorphic origin-demonstrate that black shales within the Cambro-Ordovician succession ill central Victoria lacked the vital constituents to provide (1) a primary sink for precious metals, and (2) whereas the presence of carbonaceous matter was likely to affect the evolution of epigenetic hydrothermal fluids and, locally, may have facilitated gold enrichment, carbon-rich sedimentary rocks were not crucial for ore genesis on the deposit scale. Instead, the size of the hydrothermal cell, physicochemical conditions of the ascending fluids, and dynamic fault-valve behavior played far more significant roles in controlling gold precipitation. The importance of these processes has implications for exploration targeting sediment-hosted, lode- and disseminated-style gold mineralization in the western Lachlan orogen and in slate belt provinces elsewhere.
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This paper presents the results from the investigation of arsenopyrite oxidation via mechano-chemical activation, using a stirred mill. Water and hydrogen peroxide were chosen as the lixiviant and oxidant, respectively, and maintained at a relatively low temperature (50 °C). The milling media size, mill speed, slurry percent solids and amount of H2O2 added were all kept constant throughoust these experiments. The only operational variable for this investigation was the milling time, which results in increasing levels of specific energy provided by the mill. The products of activated arsenopyrite are characterised in terms of phase composition, particulate and structural characteristics, along with reactivity. Mechano-chemical activation of arsenopyrite under oxidizing conditions shows a maximum dissolution of around 9 wt% for iron and 7 wt% for arsenic after 2 h of milling. After 3 h of milling, the main phase present is found to be amorphous in nature.
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Despite the great potential of palaeo-environmental information to strengthen natural resource policy, science and practical outcomes naturally occurring archives of palaeo-environmental and ecosystem service information have not been fully recognised or utilised to inform the development of environmental policy. In this paper, we describe how Australian palaeo-environmental science is improving environmental understanding through local studies and regional syntheses that inform us about past conditions, extreme conditions and altered ecosystem states. Australian innovations in ecosystem services research and palaeo-environmental science contribute in five important contexts: discussions about environmental understanding and management objectives, improving access to information, improved knowledge about the dynamics of ecosystem services, increasing understanding of environmental processes and resource availability, and engaging interdisciplinary approaches to manage ecosystem services. Knowledge of the past is an important starting point for setting present and future resource management objectives, anticipating consequences of trade-offs, sharing risk and evaluating and monitoring the ongoing availability of ecosystem services. Palaeo-environmental information helps reframe discussions about desirable futures and collaborative efforts between scientists, planners, managers and communities. However, further steps are needed to translate the ecosystem services concept into ecosystem services policy and tangible management objectives and actions that are useful, feasible and encompass the range of benefits to people from ecosystems. We argue that increased incorporation of palaeo-environmental information into policy and decision-making is needed for evidence-based adaptive management to enhance sustainability of ecosystem functions and reduce long-term risks.
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Two massive, poorly sorted pyroclastic kimberlite deposits from the Fox and Koala pipes at the Ekati diamond mine, Northwest Territories, Canada present different styles of alteration. The first, at Fox, has an interstitial medium-alteration assemblage dominated by saponite, serpentine (lizardite), and microlitic diopside. The second, at Koala, has an alteration assemblage of serpentine (antigorite), carbonate, and minor saponite. They share the following sequence of events. Fine-grained matrix material has been serpentinized and replaced to varying degrees within each deposit, and the proportions of the preserved mineralogy of the interstitial medium reflect the nature and degree of alteration. Fine kimberlite ash is likely to have been hydrated and serpentinized soon after deposition by volcanic fluids percolating through the kimberlite vent fill deposits. Replacement, dissolution, and infilling of primary and secondary pore space are commonly observed textural features, and indicate that several phases of alteration have occurred, either as distinct episodes or, more likely, as part of a progressive sequence. The proportion of accessory lithic fragments contained within the deposits is much greater at Fox (15 to 35%) than at Koala (<10%) and has influenced the style of alteration in two ways. First, a greater proportion of cold lithic clasts acted as heat sinks and decreased the emplacement temperature of the Fox deposit as a whole. Second, a greater proportion of granodioritic lithic clasts, especially of smaller grain sizes, provided accessible sources of silica, aluminum, and calcium to the system, thus influencing the resulting alteration mineral assemblage.
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Victoria has yielded 2500 tonnes or almost 2 per cent of the world’s gold, mostly mined between 1851 and 1910. Some 55 per cent was placer gold from modern and palaeostream systems, and from eluvial deposits. The rest came from primary quartz vein-related deposits........
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Victoria has yielded 2500 tonnes or almost 2 per cent of the world’s gold, mostly mined between 1851 and 1910. Some 55 per cent was placer gold from modern and palaeostream systems, and from eluvial deposits. The rest came from primary quartz vein-related deposits........
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Borg Indrepollen is a coastal lake on the island of Vestvågøy, Lofoten, NW Norway. A sedimentary sequence spanning the last 4500 cal. yr BP was analysed for diatom, C/N and stable isotopes (
Description:
Borg Indrepollen is a coastal lake on the island of Vestvågøy, Lofoten, NW Norway. A sedimentary sequence spanning the last 4500 cal. yr BP was analysed for diatom, C/N and stable isotopes (
Naturally occurring potentially harmful elements in groundwater in makueni county, south‐eastern kenya : effects on drinking water quality and agriculture