bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural reconstruction and mineral resource evaluation at Zinkgruvan Mine, Sweden
Authors: Annels A. E. , Ingram S. , Malmstrom L. 
Published: April 2008

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract

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

Abstract
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

Abstract

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

Abstract

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

Abstract
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

Abstract

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

Abstract
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

Abstract
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.