bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural reconstruction and mineral resource evaluation at Zinkgruvan Mine, Sweden
Authors: Annels A. E. , Ingram S. , Malmstrom L.
Published: April 2008

The use of geostatistics in ore evaluation studies is based on the relationship between point values and their spatial distribution. When an orebody is deformed the syn-depositional spatial relationship between control points is altered and it is extremely difficult to represent these points on a single plan suitable for ore reserve estimation. To overcome this problem, deformed orebodies could be dissected into a number of individual units and analysed separately, but this results in a reduction of control points available for analysis. An alternative to orebody dissection is to unroll the deposit so as to return control points back as close as possible to their original relative spatial locations.

This paper describes attempts to reconstruct the Nygruvan orebody structurally at Knalla mine, Zinkgruvan, Sweden, which is operated by Vieille-Montagne Sverige. The deposit is located in the Bergslagen geological province of south-central Sweden, and has features in common with stratiform volcanogenic massive Zn-Pb sulphides and sediment hosted exhalative Zn-Pb deposits. Nygruvan is essentially a thin (5–20 m) tabular deposit of large lateral extent, dipping at 60–80° to the northeast, which was folded and faulted during the Svecofennian orogeny.

Current ore resource evaluation methods employ the polygon method for global resources using diamond drill information, and the extrapolation of chip sample data between mine levels to produce reserves of mining blocks. These methods do not take account of orebody structure, assuming it to be a planar structure of variable thickness.

Structural reconstructions of thrust belts and deformed basins are usually achieved by drawing sections in the plane containing the movement vector. Sectional reconstruction methods do not, however, give consideration to transverse movements. If strain is triaxial, a two dimensional restoration using cross sections is not appropriate, instead a three dimensional method should be used. To date little work has been done on the development of a suitable method applicable to deformed orebodies

A small area of the mine has been selected for preliminary studies and a variety of manual methods applied in order to develop a suitable computerized restoration algorithm (these include two dimensional sectional and triaxial methods). A new Datamine unrolling package, which will be tested on this deposit, is described. A geostatistical study will be undertaken to generate a block reserve model once the deposit has been unrolled satisfactorily.
The application of geostatistical techniques to
in situ
resource estimation in the sand and gravel industry
Authors: Arthur J. , Annels A. E.
Published: April 2008

In June 1990, a research project was commenced at a site in Southern England, in which sands and gravels of the Kesgrave Formation are overlain by Anglian boulder clay. This site was, at the time, under evaluation by RMC (UK) Ltd as a potential new source of natural aggregate.

The primary aim of the research was to ascertain whether standard geostatistical techniques could be applied to Quaternary fluvio-glacial sand and gravel deposits. Comparisons would then be possible with the results of evaluations carried out using inverse distance weighting and digital terrain modelling techniques.

The data used in the project were collected by shell and auger drilling on a localized detailed drilling grid (25 m spacing), and a less regular grid (100 m hole spacing) covering the whole site. The latter was carried out as part of a standard site evaluation. The variables used in the study included mineral and overburden thickness, size gradings as defined by BS:812, and petrography.

The work has highlighted the need for improved methods of drilling and sampling in unconsolidated deposits. Loss of fine (<75 μm) material and poor sampling of the coarser (> 40 mm) fraction had resulted in excessively high nugget variances which caused difficulties in the modelling of semi-variograms for these size fractions.

This paper presents the results of the geostatistical modelling of the above parameters using a range of methods including indicator variography and kriging. In particular, the deviation of the kriged block values from specific British Standards was assessed in order to determine the potential end use of the
in situ
material, before or after selective blending/processing.
Database management at the Lisheen deposit, Co. Tipperary, Ireland
Authors: Barry J. , Guard J. , Walton G.
Published: April 2008

The Lisheen Zn-Pb-Ag deposit was discovered by the Chevron Mineral Corporation of Ireland/Ivernia West Plc Joint Venture in 1990. The mineral resource estimate is 20.5 Mt grading 13.3% Zn, 2.3% Pb and 35 g/t Ag. Massive sphalerite-galena-pyrite mineralization occurs at the base of the dolomitized, lower Carboniferous Waulsortian limestones and is bounded to the south by a shallow-dipping normal fault. The deposit is subdivided into three areas: the Main, North and Derryville Zones.

Lisheen diamond drill hole data are stored in a relational database management system called
techbase
with graphical output to AutoCad. Coding and in particular ‘nested’ coding facilitates data filtering and efficient editing and interrogation of data. The coding system has the flexibility to evolve as the multi-disciplined and multi-sourced data at Lisheen become more complex. Routine tasks which require frequently-used sequences of commands such as the generation of stick sections and data reports are automated by the use of macros (runlogs). Faster processing and editing of data considerably increases the generating speed of sections, maps and data reports which results in faster, and more accurate calculation of mineral resource estimations. ‘Technicn’ is a facility withing
techbase
which permits parameter substitution within macros through a simple memo-driven user interface.
Laboratory evaluation of kaolin: a case study from Zambia
Authors: Mitchell C. J.
Published: April 2008

Kaolin is principally used as a white pigment in the manufacture of paper and whiteware ceramics and in paints, rubbers and plastics. The desirable properties of kaolin in these end uses include chemical purity, high kaolinite content, fine particle size, euhedral kaolinite platelets, high brighteness values and appropriate rheology. This paper outlines the laboratory evaluation of a kaolin from Chilulwe, near Serenje, Central Province of Zambia. The kaolin occurs in a hydrothermally-altered feldspar pegmatite within a granite-gneiss basement. Initial laboratory characterization of the kaolin showed it to consist mainly of microcline feldspar (80%) with 17% kaolinite and trace quantities of muscovite, beryl and tourmaline. A kaolinite concentrate, produced by wet screening and hydrocloning, contained 79–87% kaolinite, with a clay (< 2 µm) content of 58%, a brightness of 70–76% (86–870n firing) and a viscosity concentration of 68%. Transmission electron microscopy showed the kaolinite to consist of rolled and hexagonal crystals. The results of this study showed that the Chilulwe kaolin, and by-product K-feldspar, have potential as a raw material for manufacture of ceramic products.
Basaltic volcanism associated with extensional tectonics in the Taiwan-Luzon island arc: evidence for non-depleted sources and subduction zone enrichment
Authors: Knittel Ulrich , Dietmar Oles
Published: April 2008

Primitive basalts were erupted from more than 100 monogenetic eruption centres within the Macolod Corridor, an extensional structure which cross-cuts the Taiwan-Luzon volcanic arc. The composition of early phenocrysts, HFSE systematics and relatively high Al
2
O
3
, TiO
2
and Na
2
O contents of these rocks suggest that they are derived from sources comparable to the sources of MORB and back-arc basin basalts. This is in contrast to many other arc magmas which appear to be derived from more depleted sources. High LILE abundances and high LILE/HFSE ratios indicate the presence of slab-derived components in the magmas, although the Macolod Corridor is no longer underlain by an actively subducting slab.
Arc volcanism in an extensional regime at the initiation of subduction: a geochemical study of Hahajima, Bonin Islands, Japan
Authors: Taylor Rex N. , Nesbitt Robert W.
Published: April 2008

Hahajima represents an Eocene forearc volcanic centre produced during the initiation of subduction within an intra-oceanic domain of the western Pacific. The Eocene-Oligocene Izu-Bonin arc-forearc is envisaged as a broad region of volcanism generated in an extensional tectonic regime. The forearc is likely to have consisted of a series of small rift basins, punctuated and bordered by coherent volcanic edifices. Hahajima represents one such edifice at the southern termination of the Chichijima-Mukojima rift basin.

Major element, trace element and isotopic data are presented for representative volcanic rocks from Hahajima. The volcanic sequence comprises porphyritic basalt and andesite breccias and flows intercalated with tuffaceous sandstones. All lavas contain high proportions of plagioclase phenocrysts (20–36%) and comparatively low mafic mineral contents. The andesite suite is typified by the presence of magnetite and orthopyroxene phenocrysts and pseudomorphs after olivine. Basalts are dominated by an assemblage of plagioclase, clinopyroxene and olivine. Nodules and xenocrysts typical of the andesites are found in the basalts and vice versa, suggesting an intimate relationship between the two magmas during volcanism.

The basaltic suite follows a tholeiitic fractionation path (iron enrichment) while the andesites are more representative of calc-alkaline magma evolution. These trends are found to be clearer when corrections are made for the excess proportions of plagioclase in the whole rock. Trace element differences between the suites can not be reconciled by a straightforward crystallization model, but can be related to a similar parental magma if the shallow level magma evolution involves a combination of open and closed system fractionation processes.

Comparisons of volcanic suites within and between each site sampled along the Izu-Bonin forearc indicate that each eruptive centre has an individual trace element signature. This suggests that variations within each site can be explained by melting and/or shallow-level fractionation processes, while differences between localities are related to heterogeneities in the composition, trace element and isotopic enrichment, and thermal characteristics of the source. The Hahajima volcanic rocks contrast with the more recent arc magmas of the Izu-Bonin system in that they share some features, such as high-Mg and elevated Zr/Y, with the contemporaneous boninitic lavas.
Concomitant evolution of tectonic environment and magma geochemistry, Ambrym volcano (Vanuatu, New Hebrides arc)
Authors: Picard C. , Monzier M. , Eissen J.-P. , Robin C.
Published: April 2008

Ambrym volcano lies in the central part of the New Hebrides island arc near the latitude where the D’Entrecasteaux Zone is colliding with the arc. It is a 35 km × 50 km, mainly basaltic stratovolcano constructed in four distinct parts: (i) well-preserved remnants of an old edifice in the north; (ii) a N100°-aligned, oval-shaped basal Hawaiian-type shield volcano; (iii) a pyroclastic cone, cut by a concentric 12 km wide caldera; and (iv) post-caldera basaltic suites, both intra- and extra-caldera. Considering K
2
O, La and Zr variations, three major trends characterize the geochemistry of Ambrym; one medium-K (MK) to high-K (HK) tholeiitic to calc-alkaline basaltic trend, and two more evolved trends, respectively MK and HK, from basaltic to dacitic and rhyodacitic compositions. These magmatic suites correspond to several volcanic phases: (1) older MK basalts forming the Tuvio-Vetlam-Dalahum edifice; (2) MK to HK basalts forming the basal shield volcano; (3) MK andesites and rhyodacites forming the first pyroclastic sequence of the Ambrym Pyroclastic Series (APS), which probably initiated the formation of the caldera; (4) MK to HK basalts and andesites forming Surtseyan then Strombolian pyroclastic sequences 2, 3 and 4 of the APS; and (5) post-caldera MK to HK basalts forming the recent olivine porphyritic- and plagioclase-porphyritic suites, locally associated with more evolved HK andesitic volcanic rocks in the eastern part of the caldera. (La/Yb)
n
and (La/K)
n
ratios (2–5.9 and 1.3–2.2, respectively) and Zr contents indicate that the parental magmas originated from incremental batch melting or fractional melting (21–25%) during uplift of a single spinel lherzolite source (from at least 60 to 45 km depth) in response to modifications in the tectonic environment due to ongoing collision with the D’Entrecasteaux Zone. However, K and La contents require prior enrichments by possible mantle metasomatism associated with subduction. Fractionation of olivine, plagioclase, clinopyroxene and Fe-Ti oxides explain most of the major and trace element variations in the resulting liquids and interaction between magmas rising from two distinct chambers combined with massive introduction of seawater into the edifice appear to be the major causes of the giant eruption leading to caldera formation. More recent activity of the volcano is principally related to shallow incremental batch melting or fractional melting and to fractionation in magma chambers associated with N100° rifting.
Gamilaroi Terrane: A Devonian rifted intra-oceanic island-arc assemblage, NSW, Australia.
Authors: Aitchison J. C. , Flood P. G.
Published: April 2008

The Gamilaroi terrane comprises part of the New England orogen of eastern Australia and contains Devonian strata preserving evidence of their development in a variety of arc-related environments. Radiolarian studies provide new and more precise constraints on stratigraphy and together with geochemistry allow development of a new model for evolution of the terrane. A diverse suite of volcaniclastic sedimentary rocks intercalated with regionally extensive extrusive and high level intrusive meta-felsic igneous rocks of low-K and calc-alkaline volcanic affinity is present. These rocks constitute the oldest
in-situ
volcanic rocks in the Gamilaroi terrane and are similar to those found in modern intra-oceanic volcanic island-arc settings. Basaltic intrusions and lavas occur at higher stratigraphic levels. Major and trace element compositions, together with relatively flat chondrite-normalized REE distributions, resemble those from rocks formed in modern intra-oceanic island-arc rift zones.

The close spatial association of these rock types together with an absence of continent-derived detritus is consistent with interpretation of development of the Gamilaroi terrane in an intra-oceanic island arc which experienced local rifting. This interpretation is a departure from previous models for the New England orogen, which interpret the Gamilaroi terrane as a forearc basin that developed above a long-lived (Cambrian to Permian), west-dipping subduction zone fringing the continental margin of Gondwana. By analogy with modern arc-continent collision zones in which crust between colliding continents and island arcs is preferentially subducted beneath the approaching arc, we suggest that oceanic crust intervening between Gamilaroi terrane and Gondwana was subducted eastwards under the western margin of the Gamilaroi terrane arc. During a latest Devonian collision event the Gamilaroi terrane was obducted onto the Gondwana margin. This resulted in subduction flip and subsequent development of an east-facing continental margin arc system on top of the Gamilaroi terrane.
Diverse shoshonite magma series in the Kamchatka Arc: relationships between intra-arc extension and composition of alkaline magmas
Authors: Kepezhinskas Pavel
Published: April 2008

High-potassium magmas were erupted in the western and eastern volcanic zones of the northern segment of the Kamchatka arc (Russia) during late Eocene to Pliocene time. Shoshonite suites of similar age show across-arc trends in major and trace element chemistry suggesting their derivation from different mantle sources. Low-Ti shoshonites from the western (rear-arc) volcanic zone are thought to have been generated in a refractory mantle wedge affected by the addition of an LILE- and LREE-enriched component possibly identified as the slab-derived hydrous fluid. High-Ti shoshonites from the eastern (frontal arc) volcanic zone were probably derived through partial melting of a more fertile source modified by the addition of a high-Na component as suggested by major and trace element systematics and radiogenic isotope relationships. This component is compositionally similar to a felsic trondhjemitic melt generated during partial melting of the hot downgoing slab in the amphibolite facies. The volcanism in the northeastern zone of the Kamchatka arc is associated with the subduction of hot oceanic lithosphere of the Komandor Basin which was generated during two stages of extension (late Eocene-Oligocene and late Miocene-Pliocene). Slab-derived melts (adakites) were erupted along with Neogene high-Ti shoshonites in the eastern volcanic zone of the northern Kamchatka arc.

Two types of shoshonites can be found in volcanic arcs. Low-Ti shoshonites are related to the temporal evolution of the subduction zone and occur at the latest stages of its development following predicted depth-K relationships. High-Ti shoshonites are associated with melting of a slab-modified mantle during the earliest stages of intra-arc rifting followed by the eruption of high-Na, Nb-enriched arc basalts. Nb-enriched arc basalts and high-Ti shoshonites are spatially and temporally associated with slab melts (adakites) in the northern segment of the Kamchatka arc.
Forward and reverse modelling of rift basin formation
Authors: Kusznir Nick J. , Roberts Alan M. , Morley Chris K.
Published: April 2008

The McKenzie model of continental lithosphere extension describes the first-order lithosphere responses of crustal thinning and geothermal gradient increase following rifting, which lead to syn- and post-rift basin subsidence. At the sub-basin scale, seismic data show the fundamental importance of major basement faults in controlling the geometry and subsidence of rifted sedimentary basins. Reflection and earthquake seismology data show that these faults are generally planar and extend down 10–15 km to mid-crustal level. Below this depth deformation gives way to distributed ductile shear in the lower crust and mantle. Extensional faulting leads not only to hanging wall subsidence but also to footwall uplift. It can be successfully modelled using elastic dislocation, visco-elastic finite element and thin plate flexural-isostasy (flexural cantilever) theories. For extension on multiple faults, interference of footwall uplift and hanging wall collapse gives rise to the familiar block rotations of rift tectonics. Mathematical forward models of rifting, incorporating upper crustal faulting, lower crust/upper mantle plastic stretching, lithosphere thermal perturbation and re-equilibration, sediment loading and flexural isostasy have been developed and applied to both syn- and post-rift stages of basin evolution. The models allow the effects on basin geometry and subsidence of fault spacing, fault polarity and extension magnitude, as well as sediment fill and footwall erosion, to be explored. Reverse post-rift modelling from present day sections may be used to constrain
β
stretching estimates and to predict palaeobathymetry and topography. Both forward and reverse models have been successfully applied to many rift basins worldwide, including the Viking Graben, North Sea and the East African Rift System, both of which are documented here. The forward model is also capable of simulating the first-order geometry of metamorphic core-complexes and so-called ‘detachment faults’ documented from the Basin-and-Range Province of the western USA.
Reservoir architecture of syn-rift lacustrine turbidite systems, early Cretaceous, offshore South Gabon
Authors: Smith R. D. A.
Published: April 2008

The Lucina Formation of offshore South Gabon comprises deep lacustrine facies deposited in an early Cretaceous rift lake. Both channellized and non-channellized turbidite sandbodies occur enclosed in deep-lacustrine mudstones. These sandbodies provide reservoirs in the Lucina and Lucina West Marine fields. Dramatic changes in sandstone body thickness occur from SW to NE across the strike of the rift lake. This was a consequence of the confinement of high-density sandy turbidity currents in fault-related lake-floor depressions. Limited palaeoccurrent data from orientated core indicate sediment transport from the SW towards the NE. This represents supply from the ramp margin of the lake towards the fault system bounding the lake along its northeastern margin. The modern Lake Malawi provides an analogue in terms of genetic elements and sediment distribution patterns. In addition, ancient marine turbidite systems such as those of the Oligo-Miocene fill of the Tertiary Piedmont Basin, Northwest Italy, provide insights into the relationships between topography in the receiving basin and sandbody geometries.
A survey of rift basin source rocks
Authors: Katz Barry J.
Published: April 2008

Various studies reveal that rift basins contain a disproportionate amount of petroleum based on their area and sediment volume. In part, this results from the excellent petroleum source rocks found in many of these basins. The presence of these sources not only influences the petroleum potential of the rift sequence, but may also influence the petroleum potential the post-rift succession. These high quality source rocks can be partially explained by the low width: depth ratios and high subsidence rates associated with rift basins. However, not all rifts contain these organic-rich deposits, nor are all the organic-rich deposits volumetrically significant. Other factors, such as climate and sedimentation rate, strongly influence the deposition of these organic-rich sediments. Within individual basins sub-basins may display dramatically different oil- vs gas-prone tendencies due to different subsidence rates. High subsidence rates favour oil source rock development, while low subsidence rates favour gas source development. Many, but not all, of these petroleum source rock systems are lacustrine. Restricted marine source rocks are also present within rift sequences. This study focuses on three elements of rift basin source rocks: (1) their distribution; (2) the factors controlling their deposition, distribution and quality; and (3) their geochemical attributes.
Rift to drift evolution in Permian-Jurassic basins of East Africa
Authors: Kreuser Thomas
Published: April 2008

Intracratonic Permo-Triassic grabens developed in eastern Africa (Tanzania, Mozambique, Zimbabwe) in five stages. Isostatic uplift after the demise of the Gondwana glaciation resulted in block faulting and erosion during the Sakmarian in some basins. Initial rift extension occurred at the Artinskian/Kungurian boundary. Half-grabens developed during the Kazanian in deep and shallow water rift lake environments, divided by accommodation zones and limited by alternating boundary faults and flexural margins. The rifts filled up during the Tatarian, separated from the Lower Triassic by a regional unconformity including a hiatus. The Triassic is characterized by increased extension rates during the final thermal subsidence phase, terminated either by abortion or basaltic outflows from Mid-Triassic to Liassic. Tilting, faulting and erosion occurred during the Miocene to recent uplift of the East African Rift margins. A two-phase rifting is witnessed in the Rukwa Basin.

Pericratonic rift evolution (Tanzania, Mozambique, Madagascar, Ethiopia) started at the Lower Jurassic and continued until the Bajocian/Bathonian breakup unconformity at 165 Ma. Drifting is associated with onlapping deltaic to restricted marine, evaporitic and also with open marine carbonates and the formation of oceanic crust.

Organic geochemistry shows a fair source rock potential for the intracratonic rift basins (i.e. the Ruhuhu and Rukwa Rifts) with favourable maturity levels. Coal macerals (liptinites) and bitumen (exsudatinite) indicate a limited liquid hydrocarbon potential for the dominantly gas prone Type III kerogens. The pericratonic coastal basins of eastern Africa and the Madagascar Rift Basins exhibit only a limited source rock potential.
Hydrocarbon habitat in the rift graben of the Central Sumatra Basin, Indonesia
Authors: Williams Harold H. , Eubank Roger T.
Published: April 2008

The geological history of the Central Sumatra Basin, situated between the Bila River to the north and the Kampar River to the south, is discussed. The structural style in Central Sumatra is produced by a tensional regime strongly overprinted by a dextral wrench component. Compression does not appear to have been a dominant force; most compression observed in the Tertiary section can be ascribed to that component of wrench tectonics. Factors that have contributed to the prolific oil production of the Central Sumatra Basin include presence of graben sequences with thick organic-rich lacustrine shales, an overlying marine sag sequence with excellent reservoirs, development of early structures and high basin heat flows. The shallow Pre-Tertiary basement and thin sediments of the Central Sumatra Basin are characterized by a very high geothermal gradient, with an average gradient of 6.1°C/100 m (3.38°F/100′).

Distribution of the oilfields in the Central Sumatra Basin is largely fault controlled. The oil has migrated vertically out of the Eocene-Oligocene age Pematang Group shales and laterally up the flanks of the graben, generally in an easterly direction, filling younger, Miocene age Sihapas Formation reservoirs. Hydrocarbon accumulations are also present within the rift-fill sequence. Migration distance is generally short, ranging up to 20 km. Models are presented to explain the structural evolution and depositional history of the Pematang graben.

Oil, and most of the gas, in the Central Sumatra Basin has been generated from organic-rich shales of lacustrine origin within the Palaeogene Pematang Group. During Palaeogene time, large freshwater lake systems developed within structurally controlled rift graben. Palynology indicates freshwater conditions prevailed, however, occurrences of slightly saline conditions suggest minor climatic changes, chemical stratification, or occasional marine incursions.

Tropical climatic conditions without an annual lake turnover favoured lacustrine anoxia and deposition of non-marine hydrocarbon source beds. Climatic changes strongly influence the stratigraphic position of oil-prone source material in the Pematang Brown Shale Formation. Differences in oils, however, appear to reflect the different depositional and environmental histories of the individual lake systems. Geochemical analyses are used in the identification of source beds, interpretation of their depositional environments, oil to source rock correlations and determining the maturation history of the source rock. Systematic variations in organic matter reflect different depositional environments and largely determine the composition of the hydrocarbons generated.
Application of sequence stratigraphy to coal-bearing coastal plain successions: implications for the UK Coal Measures
Authors: Flint Stephen , Aitken John , Hampson Gary
Published: April 2008

Advances in the understanding of coal depositional environments have led to the notion that thick, low ash deposits in close proximity to siliciclastic sediment inputs are most commonly restricted to the products of raised mires. These mires are initiated, sustained and preserved in conditions of slowly rising base level (relative sea-level). Hence it is possible to consider the stratigraphic significance of economic coal seams within the concept of unconformity bounded depositional sequences (sensuVailet al.). Time-equivalent clastic deposits tend to be minor (commonly with a heterolith fill) channel deposits, with brackish to freshwater lake and crevasse splay sediments, excluded from the peat mire either via the topographically raised nature of the mire or by the landward dislocation of fluvial facies. In this paradigm, spatially related major fluvial channel deposits, major seam splits and even washout deposits may not be time-equivalent to the coal seam. Regional correlations suggest that thick coal seams are time-correlative to significant flooding surfaces at the coeval coastline. Thus coals may be correlated with initial flooding surfaces over incised valley systems and sometimes with parasequence and parasequence set boundaries. This factor may be important in coal exploration. Application of these ideas to the classic Westphalian ‘Coal Measures’ of England indicates that the ‘marine bands’ may be regarded as flooding surfaces or condensed sections, with several being good candidates for maximum flooding surfaces. Between these marine bands the stratigraphy is punctuated by thick, stacked, regionally extensive fluvial units, incised into previously deposited sediments. These are interpreted as incised valley complexes. Systems tract assignment, based on changing accommodation space, indicates that the main coal zones fall dominantly within transgressive systems tracts.
Sedimentary facies of the coal-bearing Westphalian A and B north of the Wales-Brabant High
Authors: Guion Paul D. , Fulton Iain M. , Jones Neil S.
Published: April 2008

Important coal deposits are present in Britain north of the Wales-Brabant High in the Pennine Basin, which was initiated by late Devonian to early Carboniferous extension. The formation of coals of sufficient thickness, quality and continuity to be commercially exploited was favoured during the latest Westphalian A (Langsettian) and much of the Westphalian B (Duckmantian), when deposition took place in an environment similar to an upper delta plain, with limited marine influence. During the early part of the Westphalian A, marine influence was important, with the consequence that the coals were thinner, less persistent and of inferior quality. By the late Westphalian, alluvial deposition became important, and coals of commercial quality are rare.

Accurate determination of facies, lithological attributes and geometry is an important tool in exploration and mine planning. Sedimentary facies have thus been rationalized into those that may be consistently recognizable in boreholes and mine workings. However, facies may be further subdivided when conditions allow, and intermediate facies exist, reflecting the complexities of depositional environments. The characteristics of the following facies are described here: mire, palaeosol, marine, lacustrine, lacustrine delta, major channel, minor channel, overbank and crevasse splay. Channel deposits have a number of adverse effects on mining and the range of channel-fill deposits reflects the operation of many different processes.

A model of sedimentation is presented which emphasizes that local sedimentary and autocyclic processes, local tectonics, subsidence and compaction were important in controlling the distribution of facies at a mine scale.
Determination of trace element affinities in coal by laser ablation microprobe-inductively coupled plasma mass spectrometry
Authors: Querol X. , Chenery S.
Published: April 2008

The occurrence, association and distribution of potentially toxic trace elements (PTTEs) in coal are basic criteria for predicting the forms and amounts of trace elements that are transferred to the environment during coal combustion processes. Previously, the determination of the affinities of PTTEs in coal was carried out by laborious density separation and subsequent analysis of the density fractions. This study has evaluated a new means of directly determining PTTE affinities in coal by laser ablation microprobe-inductively coupled plasma mass spectrometry (LAMP-ICP-MS). The affinities were determined by a rapid semiquantitative methodology. Additionally, some preliminary quantitative concentrations were obtained using a novel calibration strategy. The spatial resolution of the LAMP-ICP-MS technique allows the analysis of single grains of macerals and minerals in polished blocks, leading to a wide range of applications in coal geochemistry.
Review of borehole seismic methods developed for opencast coal exploration
Authors: Goulty N. R.
Published: April 2008

Evaluation of opencast coal reserves in the UK is accomplished by drilling boreholes on a grid spacing of 40–60 m, with even closer spacings across major fault zones and in areas of old mine workings. In spite of this intensive drilling effort, it is difficult to detect small faults with throws of less than about 2 m, which can still present a serious stability hazard at site boundaries. Borehole seismic methods could be used to detect small faults, to give structural detail across major fault zones and to locate old mine workings. Two techniques have been developed for this purpose: cross-hole seismic reflection surveying and hole to surface seismic reflection surveying. Although the cross-hole method produces sections of extremely high resolution, very close source and receiver element spacings are required to image close to the boreholes. Also the borehole separation should be less than half the length of the source and receiver arrays if complete coverage is required between the arrays. The hole to surface method produces high resolution sections and could be extended to three-dimensional surveys, but imaging is limited to a bell-shaped cross-section with its apex just below the water-table. Both methods can be used to yield continuous sections along lines of boreholes and are potentially of value in other applications.
Coal production and coal reserves of the Czech Republic and former Czechoslovakia
Authors: Pešek Jiří , Pešková Jarmila
Published: April 2008

Czechoslovakia, following the communist takeover in 1948, became a member of the former East European COMECON group of countries. Its industrial potential, together with the heavy industry of the former USSR, represented a strategic base for the whole communist block. Concentration on production, with a high energy consumption, created a considerably higher demand for energy raw materials, namely brown coal in the case of Czechoslovakia. Production increased about five times with respect to 1937 levels, whereas the production of bituminous coal increased by only 80%. This created a considerable depletion of coal reserves. Consequently, only 1.9 Gt of mineable reserves of bituminous coal and about 3.1 Gt of brown coal reserves were registered in the former Czechoslovakia by 1 January 1992. These mineable reserves, recorded in the energy balance, can be divided into reserves in recently mined coal deposits and those occurring in the so-called reserve coal fields. The actual volume of mineable reserves in operating mines is equivalent to 822.7 Mt of bituminous coal and 1799.4 Mt of brown coal. Mineable reserves of brown and bituminous coal in the operating mines and open pits of the Czech Republic will be exhausted in the years 2027 and 2031, respectively, taking into consideration both the present and anticipated future production and recovery of coal.
Exploration and exploitation of the East Pennine Coalfield
Authors: Allen M. J.
Published: April 2008

The East Pennine Coalfield is the most important of all British Coal’s resources. Exploration and exploitation are closely related and studies of the coalfield’s past history, present development and future potential are relevant to the whole coal industry in the UK. At a local level the geology is often variable with uncertainty attached to reserves assessments. However, the overall development of the coalfield is substantially controlled by large-scale and easily determined geological features such as the size of the deposit, seam thickness and depth of cover. Studies on a coalfield scale can therefore contribute to assessments of the future of the coal industry.

The future production from this coalfield depends on both the size of the resource and on the proportion that can be recovered. Historical recovery data are discussed and some of the geological features of the deposit that affect coal recovery are reviewed.

Although the East Pennine Coalfield is at a mature stage of exploitation, with output from deep mines currently at about 540f its peak level in the 1950s and 1960s, the resource has not yet been fully developed, even after major investments at Selby and Asfordby. Recent exploration results from the undeveloped eastern margin of the coalfield are briefly reviewed.
Structural geological factors in open pit coal mine design, with special reference to thrusting: case study from the Ffyndaff sites in the South Wales Coalfield
Authors: Gayer Rod , Hathaway Tanya , Davis John
Published: April 2008

A review of the shear strength characteristics of Coal Measures lithologies suggests that major structurally controlled discontinuities in mudrock or coal are likely to show near-residual shear strength values, with minimal cohesion and a friction angle of approximately 12°. The principal structurally controlled discontinuities are those associated with tilting, folding and faulting. The former result from bedding plane slip during flexural folding that smoothes the bedding planes and reduces cohesion. The latter are produced by fault movements that weaken the rock and produce a structural anisotropy in the fault surface. Both are likely to confine the movement of water through the rock, enhancing weathering and further weakening the surface. In open pit design, the stability of the highwall is discussed in relation to the orientation of the various types of structurally controlled discontinuity.

A case study from Ffyndaff Opencast Coal Site in the South Wales Coalfield is analysed, and shows that the major normal faults that cut the site intersect the highwall with a stable orientation. Regional dip in the site also has a stable orientation, but the site is affected by several major north-verging thrusts that have been investigated by computer analysis of borehole and coal extraction data. The results indicate that the thrusts have a ramp-flat geometry and are likely to imbricate upwards from a bed-parallel detachment in a coal seam. The thrusts have generally developed in a piggy-back sequence, although at least one formed as a break-back thrust. The thrust displacement (slip separation) variation along the thrusts is described and suggests a normal displacement gradient of 0.16–0.18. These geometrical characteristics are used to interpret the thrust structure of a potential site from exploratory borehole logs, where the predicted geometry limits the location of the bounding highwall.
Sequence stratigraphy and lithofacies geometry in an early Namurian coal-bearing succession in central Scotland
Authors: Read W. A.
Published: April 2008

High frequency glacial-eustatic allocycles have been identified in the upper part of the early Pendleian Limestone Coal Formation in the north-central Midland Valley of Scotland. Repeated eustatic oscillations caused extensive lateral migrations of a wide spectrum of depositional environments, ranging from quasi-marine to fluvial. This throws doubt on the assumptions that underlie some existing depositional models of similar late Carboniferous cyclic coal-bearing successions.

The study interval can be divided into three facies associations. The distal association was dominantly controlled by glacial-eustatic oscillations, which resulted in a remarkably regular ‘layer cake’ succession with laterally persistent coals. In the more sandy and variable transitional facies association, local episodic fluvial processes tended to obscure the underlying allocycles. Here coals may split and also amalgamate to form thick composite seams. The highly variable proximal association was dominantly controlled by irregular autocyclic fluvial sedimentary processes which largely obscured the background changes in relative sea level. Sequence stratigraphy is easy to apply to the distal facies association, harder to apply to the transitional association and very difficult to apply to the variable proximal association.
An introduction to the techniques, limitations and landmarks of carbonate oxygen isotope palaeothermometry
Authors: Corfield Richard M.
Published: April 2008

The fractionation of oxygen isotopes is temperature dependent. The ratio of the two commonest isotopes (
16
O and
18
O) in carbonate fossils can, in principle, be used to reconstruct the temperature of ancient oceans. Fossil foraminifera are commonly analysed in the Cenozoic and late Mesozoic and, when appropriately identified and separated, seasurface, deeper-water and bottom-water temperatures can be inferred. More ancient carbonate precipitating macrofossils (e.g. molluscs, brachiopods) have also been used, as well as inorganically precipitated carbonate cements. Drawbacks to the oxygen isotope method of palaeotemperature determination are the uncertainties in the isotopic composition of the water of ancient oceans, the occurrence of non-equilibrium fractionation in organically precipitated calcites (especially in macrofossils) and diagenetic alteration to the δ
18
O values of carbonate fossils.

Notwithstanding these limitations, trends in palaeotemperature and/or the δ
18
O of seawater, such as the Palaeozoic
18
O enrichment, the long-term Cretaceous and Tertiary climatic cooling, the middle Miocene
18
O enrichment, as well as the Pleistocene succession of glaciations, are discernible from appropriate studies of fossil carbonates.
Palaeo-oxygenation: effects and recognition
Authors: Allison Peter A. , Wignall Paul B. , Brett Carlton E.
Published: April 2008

Oxygen is a bio-limiting element for metazoa and one of the most important factors influencing species diversity and abundance in the marine realm. Equally, the absence of oxygen is generally considered to be essential for the inhibition of microbial decay and the formation of organic-rich sediments. As such, the determination of depositional palaeo-oxygenation values of ancient rocks has become a fundamental quest for the palaeoecologist and mudrock sedimentologist. In this paper the development of the tripartite anaerobic-dysaerobic-aerobic terminology for oxygen-related biofacies and the recent additions of the exaerobic and poikiloaerobic biofacies are reviewed. The new, non-genetic, oxygen-restricted biofacies (ORB) scheme is also presented. Chemosymbiotic life strategies have been suggested to be important in many extinct black shale taxa but a glance at modern chemosymbionts casts doubt on the significance of this mode of life in ORB. A review of lowest dysaerobic benthic forms throughout the Phanerozoic reveals the repeated occurrence of a few morphologies almost exclusively derived from the brachiopods and bivalves. Geochemical indices of palaeo-oxygen levels are also reviewed.

The recent renaissance in the development of criteria for the determination of palaeo-oxygen values has led to the recognition of a considerably greater variety of dysaerobic biofacies in the geological record. This is illustrated with two case studies, the first, from the celebrated Burgess Shale of British Columbia, shows a depositional environment dominated by a fluctuating oxycline. The second case study, from widely separated earliest Triassic marine sections, illustrates the possibility of a widespread (global) dysoxic event at this time.
Palaeoenvironmental interpretation using bryozoans: a review
Authors: Smith Abigail M.
Published: April 2008

Bryozoans are colonial marine organisms, found in the fossil record since the early Ordovician. They have many possible applications in palaeoenvironmental interpretation. Their presence or absence, diversity and abundance, zooid morphology, colonial plasticity, colonial growth form, and reef-like structures all provide information about habitat. Temperature, salinity, water energy, water depth, substrate character, sedimentation rate, and even tectonic stability, may be indicated by bryozoan faunas. Examples are given to show palaeoecological applications of bryozoans, from shelf and deep-sea sediment studies to interpretation of Tertiary limestones and Palaeozoic environments. Caution is needed, particularly in interpreting very ancient faunas, due to the confounding factors of sampling bias, interdependent controls, taxonomic evolution and taphonomic selectivity. Bryozoans are nevertheless a tool of considerable value in palaeoenvironmental interpretation, particularly if corroborated with other lines of evidence.
Microfossil indicators of ocean water masses, circulation and climate
Authors: Murray John W.
Published: April 2008

Circulation within oceans is closely linked to climate through feedback mechanisms and both are controlled by insolation and the rotation of the Earth. Because the distribution of organisms is related to the water masses in modern oceans their distribution in the fossil record can be used as a proxy of past water masses. For surface waters the main proxies are calcareous nannofossils, diatoms, radiolaria and planktonic foraminifera. Transfer functions have been derived to determine sea surface temperatures from planktonic microfossils from the Pleistocene and Pliocene. Upwelling regions have distinctive characteristics, notably a great abundance of diatoms and a high dominance of
Globigerina bulloides
d’Orbigny. For bottom waters the principal proxies are benthic foraminifera and, to a minor extent, ostracods. Some assemblages of epifaunal benthic foraminifera seem to be correlated with specific bottom-water masses, but this is not so for infaunal assemblages. The development of thermohaline circulation caused benthic taxa to adjust their depth distribution patterns; some species became extinct and were replaced by others. Changes in distribution patterns in the Neogene have been interpreted as indicating changes in bottom-water mass structure and distribution. For instance,
Nuttallides umboniferus
(Cushman) has been used by several authors to map the past distribution of Antarctic Bottom Water. Sometimes processes operating at the ocean surface produce effects on the ocean floor which override benthic processes. Examples of this include seasonal input of phytodetritus which leads to blooms of
Epistominella exigua
(Brady), and deposition of laminated diatom mats which inhibit bioturbators.
An analytical method for calculating the performance of heterogeneous reservoirs and its use in uncertainty analysis
Authors: Kjønsvik Dagrun , Alvestad Jostein
Published: April 2008

An efficient analytical method for performance calculations in heterogeneous models is developed, under assumptions of a viscous dominated displacement process and unit mobility ratio. The method provides a quantitative measure of the effects of heterogeneities on displacement characteristics and production performance. Results indicate that the method has a potential for ranking a set of geostatistical reservoir model realizations in terms of production performance, thereby providing a basis for selecting realizations for detailed numerical simulations.