bluuebunny/crossref_metadata_2025_split huggingface dataset:
Geodynamic processes that control the global distribution of giant gold deposits
Authors: Leahy K. , Barnicoat A. C. , Foster R. P. , Lawrence S. R. , Napier R. W. 
Published: April 2008

Abstract
This paper address the question of why giant gold deposits are so unevenly spread over the continents, what processes control their distribution, and how more might be found? Using the source-migration-trap paradigm, it is proposed that the regional distribution of gold deposits is controlled by fluid access to gold sources on a regional scale, and by large-scale migration mechanisms. Local distribution is controlled by migration and trap processes, not discussed in this paper. Our current levels of understanding of gold suggest a strong geodynamic control in the generation of enriched source rocks and the fluids that may carry gold, particularly the influence of subduction and accretion during orogeny. A new six-fold geodynamic classification system that emphasizes subduction and accretion processes has been used here qualitatively to assess the potential for gold-bearing source areas. The resulting classification is compared to the distribution of 181 known giant gold deposits (those with more than 100 t contained gold). The results confirm the proposition that the distribution of giant gold deposits is ultimately a function of the amount of oceanic crust consumed during the orogenic episode that built that part of the crust. Of the six geodynamic classes described, large ocean closure orogens were found to contain the most gold, with nearly half of the world’s gold held in known giant deposits. Implications for understanding ore genesis, exploration for other giant deposits, and for other empirical explanations of the distribution of gold are discussed further.
Properties of fault damage zones in siliclastic rocks: a modelling approach
Authors: Odling N. E. , Harris S. D. , Vaszi A. Z. , Knipe R. J. 
Published: April 2008

Abstract
Major faults are surrounded by damage zones of minor faults that, in siliclastic rocks, can form barriers to flow in their own right. Reservoir flow simulation — now a routine part of reservoir management — requires equivalent hydraulic parameters on the scale of the whole fault, while reservoir geological models, from which flow simulator grids are generated, require information on the 3D characteristics of fault populations. Here, a stochastic model of fault damage zone architecture is generated and used to explore the impact of damage zone architecture on extrapolation from 1D (fault throw) and 2D (fault length) to 3D fault population characteristics. Sampling of the simulated damage zone models shows that clustering of faults causes deviations from simple laws relating particularly 1D samples to 3D population power-law exponents, with differences between expected and observed values of up to 0.25. The stochastic model is used to generate input for a 2D discrete fracture flow model for the case where minor (isotropic) fault permeability is four orders of magnitude lower than that of the host rock and, thus, forms partial barriers to flow. The flow model is used to explore the impact of fault damage zones on bulk fault permeability. The damage zone is shown to be around 50% efficient, i.e. a simple estimate of bulk permeability can be made using the harmonic average of fault rock and host-rock permeability weighted by thickness in 1D traverses (e.g. core, well logs), where only half the observed thickness of fault rock in the fault damage zone is assumed. Considering the contributions of the damage zone and the major slip zone, the fault damage zone is likely to make a significant contribution to the bulk permeability of the fault as a whole when the permeability of minor faults in the damage zone is similar to, or at most, one order of magnitude greater than that of the slip zone fault rocks.
Anomalous diffusion in simulations of pumping tests on fractal lattices
Authors: Sellers Shaun , Barker John A. 
Published: April 2008

Abstract
The recent interest in fractals in the geosciences literature has led to several proposed theoretical models for the hydraulic testing of fractured-rock systems that exhibit a fractal-like geometric structure. There is, however, no agreement on the correct form of the resulting model equations. In order to gain some insight into the range of possible behaviours to be expected from pumping tests on such systems, as well as the type of theoretical models needed, extensive simulations of pressure diffusion for transient groundwater flow, modelled by random walks on both deterministic and random fractal lattices were performed. For simplicity, the focus was on measurements of the random-walk dimension for generalized Sierpinski carpets, a proposed model for porous and fractured media. In addition to the expected anomalous slow down in diffusion in fractals as measured by the random-walk dimension, the simulations show further novel and unexpected anomalous behaviour due to the presence of internal boundaries at all scales. None of the proposed theoretical models for pumping tests on fractals appears consistent with all of the observed anomalous behaviours. The simulations suggest that interpretation of experimental pumping tests in terms of well-defined non-integer dimensions can be difficult, even when finite-size effects are negligible.
Models of tracer breakthrough and permeability in simple fractured porous media
Authors: Johnston P. B. , Atkinson T. C. , Odling N. E. , Barker J. A. 
Published: April 2008

Abstract
Tailing and bimodal behaviour of tracer breakthrough curves from tracer tests conducted in fractured porous media are commonly presented as ‘deviations’ from the Fickian model for homogeneous porous media. Tailing is mainly attributed to: (1) tracer storage brought about by diffusion between mobile and static regions of fluid; (2) a concentration of flow towards the wider (aperture) and, thus, more permeable fracture zones; and (3) the high variance in fracture conductivity and consequent mixing of tracer. Bi- (or multi-) modality has been attributed to solute following a few highly permeable flow paths. Systematic numerical simulations of flow and transport in geometrically simple fractured porous media were conducted using a 2D finite difference flow code and a particle tracking transport model. As a simplification only advective dispersion was considered. The modelling study produced a large variety of tracer breakthrough curves, including two patterns commonly seen in field data — the backward tailed uni-modal type and the Gaussian type. The study demonstrates that different types of breakthrough might be characteristic of particular sets of conceptual models for heterogeneities and, as such, may provide a useful pointer in the application and interpretation of tracer tests.
Mineral resources and their economic significance in national development: Bangladesh perspective
Authors: Akhtar Afia 
Published: April 2008

Abstract
Modern urbanization, industrialization, transportation and communication systems are the achievements of worldwide sustainable mineral resource development and their proper utilization in various sectors. Sustainable mineral resources have played, and are still playing, a vital role in shaping the modern civilized industrial world. This means that the sustainable socio-economic infrastructure of any country is an indication of its richness in natural resources, its technological know how, its ability to explore and exploit mineral resources, and, finally, its wisdom in utilizing those resources properly in the development activities of the nation. In development activities, countries of the developing world are generally far behind compared with countries in the developed world. This is mainly due to a lack of adequate natural resources, properly educated human resources and good socio-economic conditions. Although Bangladesh is a small country, it has a number of mineral resources such as natural gas, oil, coal, hard rock, limestone, white clay, glass sand and mineral sand. At present, natural gas is the only mineral commodity significantly contributing to the national economy. More than 90% of the country’s energy needs are met by gas, total reserves of which are 21.35 trillion cubic feet (TCF) and 12.43 TCF, respectively. Huge reserves of hard rock (granodiorite, quartzdiorite, gneiss) and coal in northwest Bangladesh will help, in the near future, to meet the growing demand for construction materials and energy for the ever-growing population. Total coal reserves are 1753 million tons (MT), the market value of which is more than US$110 billion. Hard rock reserves are 115 million tons, valued at over US$3 billion. Fully fledged extraction of these resources would help to alleviate the country’s poverty through industrialization. It is expected that coal will soon be extracted on a commercial basis, of which 70 to 80% will be used in power generation. The mineral resources so far found in Bangladesh are meagre in comparison to its high population. To meet the growing demand of the population, more mineral resources need to be discovered and developed, otherwise sustainable development cannot be achieved. However, it is difficult for developing countries like Bangladesh to carry out the necessary activities for exploration and exploitation of hidden mineral resources without foreign assistance. This is a major drawback for Bangladesh. To progress towards an endurable sustainable society, a nation such as Bangladesh must give priority to the development of its existing mineral resources, which can play a major role in helping to reshape the country’s socio-economic infrastructure.
Obstacles in the sustainable development of artisanal and small-scale mines in Pakistan and remedial measures
Authors: Husain Viqar 
Published: April 2008

Abstract
Pakistan is a large country with diverse geology and geography. It possesses many industrial rocks and minerals, including precious stones, marble and granite. Some metallic mineral deposits, and large reserves of coal/lignite, oil and natural gas also occur. Pakistan’s mining industry is dominated by thousands of artisanal and small-scale mines, which lack capital, technical know how, modern equipment and trained manpower. Further, local mining practices cause much damage to mineral deposits and are very hazardous to the health of mine workers and the environment. The mining sector is backward due to lack of political will and pragmatic mining laws, and absence of technical and financial support by the government agencies to the small mining units. Moreover, the narrow base of the domestic mineral industry leads to poor demand in the local market and low mineral production. Additionally, the lack of infrastructure and the poor law and order situation adversely affect the mineral industry. Further, mineral-rich districts of the country are socio-economically backward due to hilly terrain or arid climate and, hence, less suitable for agriculture. Sustainable development of artisanal and small-scale mines is possible if the necessary legal, technological, financial, commercial, social and environmental support is provided on a long-term basis.
Mining and environmental problems in the Ib valley coalfield of Orissa, India
Authors: Mishra P. Paramita 
Published: April 2008

Abstract
The exploitation of mineral resources through surface and underground mining has in the past caused a wide range of environmental problems such as health degradation, air, water and noise pollution, decline in agricultural production, deforestation, displacement and other socio-economic impacts. However, over the past number of years, stakeholders in the industry have been striving to avoid and mitigate the potential detrimental effects of mining on fragile ecosystems and local communities. Governments are increasingly formulating and adopting policies to ensure the sustainable development of their country’s mining industry and mining companies are striving to be better environmental citizens. Environmental groups have become increasingly involved in mining disputes. However, a lot has to be achieved to ensure mining in carried out in a sustainable way. This paper concentrates on the environmental effects of coal mining in the Ib valley coalfield of Orissa, India. Background to the increasing awareness of the environmental issues associated with mining is provided in the first section of this paper. The second section discusses the general problems associated with mining, with particular reference to the Ib valley coalfield. In addition, measures undertaken by the companies operating the Ib valley coalfield to deal with environmental problems are presented.
System dynamics modelling: a more effective tool for assessing the impact of sustainable development policies on the mining industry
Authors: O’Regan B. , Moles R. 
Published: April 2008

Abstract
The high mobility of mining investment is frequently cited in the literature. Consequently, the concept of relative attractiveness is particularly important. This paper describes a detailed computer simulation ‘feedback’ model. The model provides a means of examining the effects of varied environmental, fiscal and corporate policies on the flow of investment funds and mineral resources between a number of simulated mining firms and competing countries. Through a quantitative analysis of existing data, the model exposes, within the context of sustainable development, the underlying assumptions used as a basis for corporate decisions. Through the compression of time, the model provides a means of taking these assumptions to their logical conclusions. Exposing assumptions in this way leaves less room for misinterpretation and provides a solid basis for enhancing the understanding of system structure. It is by better understanding system structure that more effective sustainable development policies may be designed and implemented. An outline of the system dynamics method is also presented.
Flow events on a hyper-arid alluvial fan: Quebrada Tambores, Salar de Atacama, northern Chile
Authors: Mather Anne E. , Hartley Adrian 
Published: April 2008

Abstract

The Tambores alluvial fan is located within the hyper-arid Atacama Desert of northern Chile. We examine evidence of the range of flow processes operative in this environment from a combination of Pleistocene-Holocene fan deposits and a recent (2001) flood event (16 m
3
s
−1
) in the fan feeder channel and upper alluvial-fan area. The field evidence suggests that peak flows recorded in the older deposits generated extensive sheetflood events dominated by antidune deposition in the upper fan area. These extreme, supercritical flows were generated by floods with sustained high sediment and water discharges and high stream power. Easily erodable alluvial source materials ensured high sediment discharge could be maintained within flood events. High stream power was ensured as a function of the tectonically exacerbated gradients within the source area. The 2001 event indicates the rapid rheological changes that can occur within an individual flood event, ranging from hyperconcentrated streamflow to mudflow. The flow deposits vary little in maximum clast size either between the varying flood events in the upper fan area, or down the fan gradient. This is due to a limited calibre of sediment being produced from the source area. The study highlights: (1) the range of flow rheologies that can be generated from a hyper-arid catchment both within and between flood events of varying magnitude and the associated difficulties in generating a reliable stratigraphy from the resultant deposits; (2) the high stream power and sediment discharge associated with major flood events and thus the nature of flood hazard in the catchment and on the fan; and (3) the limitations of sedimentological information such as maximum clast size as an indicator of peak flow characteristics in ancient deposits.
Fans with forests: contemporary hydrogeomorphic processes on fans with forests in west central British Columbia, Canada
Authors: Wilford D. J. , Sakals M. E. , Innes J. L. , Sidle R. C. 
Published: April 2008

Abstract
Alluvial and colluvial fans with forest cover are common in the valleys of west central British Columbia, Canada. Given the low population density of the region, most of these fans are uninhabited and the primary land use is forestry. The fans are desirable for timber harvesting due to the combination of the relatively easy access to their valley-bottom locations and their high-quality timber. However, they are also sites influenced by debris flows, debris floods and floods, and the interaction between conventional forest practices and these natural hydrogeomorphic processes has led to substantial financial costs and disturbance to forests and stream channels. Basic watershed morphometrics can be used to predict the dominant hydrogeomorphic process influencing forested fans. The hydrogeomorphically active zones of forested fans have characteristic site and stand features, and are referred to as the hydrogeomorphic riparian zone. Features within these zones can be used to determine the frequency and disturbance extent of hydrogeomorphic events. Appropriate management strategies can be developed to limit the effect of forestry activities on natural hydrogeomorphic processes.
The fluvial megafan of Abarkoh Basin (Central Iran): an example of flash-flood sedimentation in arid lands
Authors: Arzani Nasser 
Published: April 2008

Abstract

The Abarkoh Basin is situated in central part of the NW-SE-trending Gavkhoni-Sirjan depression of Central Iran. The studied fluvial megafan represents a Quaternary fan, which is located in the western part of this intermontane, extensional basin. This fan covers an area of 940 km
2
and with a gentle slope (about 0.5°) over a 45 km-length terminates in a playa lake in the centre of the Abarkoh Basin. Its catchment is the Abadeh Basin (> 2000 km
2
), which is a NW-SE-trending intermontane basin and mainly floored with the Quaternary alluvial-fan sediments. The studied megafan was built by stream-dominated processes, as revealed by the presence of thick-bedded, clast-supported gravels-sandy gravels (gravelly-sandy conglomerates) in the proximal-fan areas that grade into thick marls with sinuous, lenticular channel-filled, grain-supported, imbricated, pebbly conglomerates in the proximal-medial fan regions. Thick calcareous marls and lenticular, single channel-fill sandstone-conglomerate deposits characterize the distal part of the fan and pass laterally into sediments of the playa lake fringe. The aim of this paper is to present an example of a fluvial megafan in an arid-semi-arid setting, to highlight the flash-flood, sheetflood-channelized sedimentation in megafans, and to stress their importance in water resources in arid lands. Fluvial fans are frequently identified in the rock record. The fluvial megafan of the Abarkoh Basin represents one of only a few described, large-scale, stream-dominated, Quaternary megafans in arid-semi-arid settings.
Climate and tectonically controlled river style changes on the Sajó-Hernád alluvial fan (Hungary)
Authors: Gábris Gyula , Nagy Balázs 
Published: April 2008

Abstract
Based on geomorphological field investigations, sediment analysis, radiocarbon and palynological data, changes in fluvial style have been recognized on one of the most important low-angle fluvial-dominant alluvial fans on the margin of the Great Hungarian Plain (Hungary). Late Pleistocene and Holocene climatic and tectonic controls are reflected partly by meandering and anastomosed channel pattern changes, and partly by erosional step features on the cone that mark erosional and accumulational phases. This work has led to the surface mapping of a ‘horizontal stratigraphy’ as part of a larger research project in the Tisza region.
Upper Cretaceous-Palaeocene basin-margin alluvial fans documenting interaction between tectonic and environmental processes (Provence, SE France)
Authors: Leleu S. , Ghienne J.-F. , Manatschal G. 
Published: April 2008

Abstract
Upper Cretaceous-Palaeocene alluvial-fan conglomerates exposed along the northern margin of the Arc Basin (Provence, SE France) preserve a continuum between undeformed basinal deposits and syntectonic alluvial-fan deposits. Based on the distribution of facies associations and growth structures in the alluvial-fan deposits, and using marker levels and erosional surfaces, the tectono-sedimentary evolution of the basin margin is discussed. On a long timescale, the stratigraphic pattern in the alluvial-fan deposits mainly records the tectonic activity in the catchment, and subordinate out-of-syncline thrusts in the basin margin. On an intermediate timescale, evolution in the drainage area controls the spatial evolution of the alluvial fans and some minor changes in depositional facies. High-frequency cycles record aggradation-stabilization sequences, resulting in vertically superimposed alluvial-fan bodies more probably tectonically controlled, whereas alternation between conglomerates-siltstones at the scale of interbedding most probably reflects climatic cycles.
Lower Cretaceous (Berriasian-Aptian) biostratigraphy of the Neuquén Basin
Authors: Aguirre-Urreta M. Beatriz , Rawson Peter F. , Concheyro G. Andrea , Bown Paul R. , Ottone Eduardo G. 
Published: April 2008

Abstract
The Berriasian-Aptian succession in the Neuquén Basin is mainly marine in the lower part and non-marine in the upper portion. A detailed ammonite zonation is presented for the Berriasian-?Early Barremian interval. While some ammonite taxa are endemic, others are widely distributed and there are several levels where correlation can be suggested with the ‘standard’ stages and zones of the Tethyan Mediterranean area. Several nannofossil bioevents are recognized, and these provide evidence for correlation with Tethyan areas. Correlations suggested by both groups are reasonably consistent. Berriasian-Aptian palynomorphs include both terrestrial and marine forms. Several terrestrial assemblages can be recognized, but the marine forms are mainly long-ranging taxa, especially in the Agrio Formation.
Sedimentology of the tide-dominated Jurassic Lajas Formation, Neuquén Basin, Argentina
Authors: McIlroy Duncan , Flint Stephen , Howell John A. , Timms Nick 
Published: April 2008

Abstract
Tidal depositional systems are often interpreted as lowstand/transgressive estuarine deposits within sequences that are either wave or river dominated during highstand times. The Middle Jurassic Lajas Formation of the Neuquén Basin, Argentina, comprises 600 m of well-exposed tide-dominated facies deposited within four unconformitybounded sequences, spanning approximately 4.5 Ma. Facies associations include tidedominated deltas, sandy-heterolithic tidal channel fills and extensive progradational tidal-flat successions, which are locally cut by heterolithic tidal channel fills. Despite the narrow bathymetric depositional range and the complex facies variability, flooding surfaces can be defined and mapped along a 48 km-long outcrop belt. These flooding surfaces allow definition of three distinct types of parasequence that exhibit coarsening-upwards, finingupwards and coarsening- to fining-upwards motifs. Sequence boundaries are marked by widespread, but shallow, incision, and the juxtaposition of stacked fluvial/tidal channel fills on a variety of subtidal and intertidal facies. Unconventional grain-size changes at sequence boundaries can occur where basinward facies shifts are marked by juxtaposition of heterolithic-argillaceous intertidal/supratidal mudflat deposits on subtidal sandflat facies. The maintenance of macrotidal conditions through complete base-level cycles is interpreted as being due to the structural topography inherited from rifting, causing the whole sub-basin to behave as a structurally controlled embayment.