bluuebunny/crossref_metadata_2025_split huggingface dataset:
The application of heavy indicator mineralogy in mineral exploration with emphasis on base metal indicators in glaciated metamorphic and plutonic terrains
Authors: Averill Stuart A. 
Published: April 2008

Abstract
Indicator mineralogy is used to explore for a wide variety of mineral commodities. The method utilizes minerals which are sufficiently heavy to be readily concentrated in the laboratory, often colourful and possess other useful physical and chemical properties. The minerals also must be source specific. Some indicator minerals are true resistate minerals. The others, although less resistant, are stable in oxidized glacial drift and many non-glacial sediments. A few, such as gold grains, are silt sized but most are coarse grained. Grain size has a major impact on indicator mineral dispersal patterns in glacial drift.
The coarse-grained indicator minerals are of two main types: (1) kimberlite indicator minerals (KIMs); and (2) metamorphosed or magmatic massive sulphide indicator minerals (MMSIMs). KIMs are enriched in Mg and Cr and most MMSIMs are enriched in Mg, Mn, Al or Cr. These indicator elements cannot be diagnosed geochemically in anomalous heavy mineral concentrates because the concentrates contain other, more plentiful non-indicator minerals containing the same elements in the same chemical form. Chalcopyrite is also a very useful MMSIM but the number of surviving grains in a dispersal train is too low for detection by selective geochemical analysis.
MMSIMs are derived from three main types of base metal deposits and their associated alteration or reaction zones: (1) volcanosedimentary massive sulphides (encompassing volcanogenic, Sedex and Mississippi Valley subtypes) in medium to high grade regional metamorphic terrains; (2) skarn and greisen deposits; and (3) magmatic Ni-Cu sulphides. The variety of MMSIMs associated with Ni-Cu deposits is astonishing, apparently reflecting mineral hybridization related to assimilation of sulphurous sedimentary rocks by ultramafic magmas. Cr-diopside is one of the best indicators of fertile Ni-Cu environments although not necessarily of the actual Ni-Cu deposits.
Heavy indicator mineralogy is much more sensitive than heavy mineral geochemical analysis and offers many exploration benefits in regional exploration programs including: (1) sampling efficiencies; (2) enlargement of both the bedrock target and dispersal train; (3) coverage of a wider range of mineral commodities; (4) undiminished sensitivity in areas of overabundant non-indicator heavy minerals; (5) visual evidence of points of origin of dispersal trains; and (6) indications of the economic potential of the source mineralization. It is most effective as a reconnaissance exploration tool and is particularly well suited for testing gneissic volcanosedimentary and plutonic terranes where base and precious metal deposits are highly modified and difficult to recognize by other prospecting methods.
Lake sediment geochemical methods in the Canadian Shield, Cordillera and Appalachia
Authors: Cook Stephen J. , McConnell John W. 
Published: April 2008

Abstract

Lake sediment geochemistry has been used in Canada since the 1970s for mineral exploration and resource evaluation in glaciated regions of Appalachia, the Canadian Shield and the western Cordillera which are of low to moderate relief. Geochemical signatures of bedrock and mineralization within a lake’s catchment basin are commonly reflected in the chemical constituents of the organic-rich Holocene sediment which has been transported from source by a combination of mechanical and hydromorphic processes. Lake sediment geochemical surveys have been used successfully to discover base metal, Au, Mo, W, Sb, Sn, U, and REE mineralization. The scale of such surveys determines the size and density of lake sediment sampling. In regional surveys, large lithological targets such as greenstone belts or chemically distinctive intrusives can be identified by low density (
c.
1 per 10–15 km
2
) sampling of relatively larger lakes. Smaller targets such as mineralized areas require higher density (
c.
1 per 4–5 km
2
) sampling using a greater number of smaller lakes. Regional surveys are typically helicopter-borne, and employ a tubular grab sampler which permits rapid reconnaissance-scale coverage of large areas. Centre-basin profundal lake sediment, or gyttja, is an ideal sample medium because of its homogeneity and abundance of fine-grained organic matter, which complexes with many trace elements. Multi-element analytical techniques in common use include inductively coupled plasma emission spectrometry (ICP-ES), ICP mass spectrometry (ICP-MS) and instrumental neutron activation analysis (INAA). Reliability of data is assessed by analysis of known standards, site duplicates and sample splits. PC statistical software packages facilitate the interpretation of geochemical data, and desktop GIS packages aid in further interpretation and generation of multi-layer maps.
Regional and local-scale gold grain and till geochemical signatures of lode Au deposits in the western Abitibi Greenstone Belt, central Canada
Authors: McClenaghan M. Beth 
Published: April 2008

Abstract
This paper is an overview of drift exploration methods for lode Au deposits in areas of thin and thick cover of glacial sediments within the Abitibi Greenstone Belt of central Canada. It summarizes a large volume of data produced by government regional surveys and case studies as well as that from industry-led gold exploration programs. Regional till surveys can be used as targeting mechanisms for further Au exploration. Anomalies are defined by a series of samples with elevated Au concentrations that lie along significant bedrock structures, occurring in clusters or as isolated samples in areas of low sample density. Thresholds between background and anomalous Au grain abundances or Au concentrations are variable and depend on location within the Abitibi Greenstone Belt. Case studies around known deposits provide examples of geochemical and mineralogical signatures of Au deposits that can be expected in till down-ice. These serve as sources of information on appropriate sampling methods and size fractions to analyse, and on ice flow patterns, local glacial stratigraphy and suitable till units for sampling. Two methods for measuring the Au content of till are commonly used: (1) a count of visible Au grains and (2) geochemical elemental analysis. Close to source, till contains thousands to hundreds of thousands ppb Au and several hundred Au grains. The Au grains vary from coarse sand to silt sizes and have pristine shapes. The presence of high Au concentrations in till indicates that the ore zones subcrop and that glacial processes have produced Au dispersal trains down-ice.
Development of the continental margins of the Labrador Sea: a review
Authors: Chalmers James A. , Pulvertaft T.C.R. 
Published: April 2008

AbstractThe Labrador Sea is a small oceanic basin that developed when the North American and Greenland plates separated. An initial period of stretching in Early Cretaceous time formed sedimentary basins now preserved under the continental shelves and around the margins of the oceanic crust. The basins subsided thermally during Late Cretaceous time and a second episode of tectonism took place during latest Cretaceous and early Paleocene time, before the onset of sea-floor spreading in mid-Paleocene time. Around the northern Labrador Sea, Davis Strait and in southern Baffin Bay, voluminous picrites and basalts were erupted at and shortly after the commencement of sea-floor spreading. Volcanism occurred again in early Eocene time at the same time as sea-floor spreading commenced in the northern North Atlantic. Farther southeast, along the Labrador and southern West Greenland margins, oceanic crust is separated from continental crust by highly stretched but non-magmatic transition zones which developed before sea-floor spreading. A complex transform zone, which developed during sea-floor spreading in late Paleocene and early Eocene time, separates continental and oceanic crust along the Baffin Island margin. The Greenland and Labrador ocean-continent transitions are asymmetric across the only available conjugate cross-sections. However, a cross-section through the Labrador margin farther north resembles the Greenland cross-section in the conjugate pair more than it does the Labrador cross-section of this pair. Consideration of the geological history of the area suggests that the non-magmatic transition zones may have formed by slow extension of a few millimetres per year through a period of 53 Ma during Cretaceous and early Paleocene time.
Rifting along non-volcanic passive margins: stratigraphic and seismic evidence from the Mesozoic successions of the Alps and western Iberia
Authors: Wilson R.C.L. , Manatschal G. , Wise S. 
Published: April 2008

Abstract
The paper examines aspects of the sedimentology and stratigraphy of rift basins that evolved in deep marine settings near the ocean-continent transition. It focuses on the applicability of a low-angle extensional detachment model developed in the Alps to the West Iberian margin, and on difficulties of objectively identifying syn-rift stratigraphic intervals in both areas. The paper examines evidence obtained from Ocean Drilling Program holes drilled in the Iberia Abyssal Plain. Despite the fact that all the holes were sited above highs in the acoustic basement and so did not penetrate a complete sedimentary record of rifting, they do provide some constraints on the age and mechanism of rifting. We suggest that published identifications of syn-rift intervals in distal basins off West Iberia and in the Southern Alps have not demonstrated, using objective criteria, the occurrence of syn-rift stratigraphic intervals. They have, therefore, probably overestimated the duration of rifting by as much as 20 Ma. The absence of syn-rift related stratal divergence towards fault footwalls may be due to resedimentation of syn-rift sediments towards basin centres, lack of significant hanging-wall rotation along flat detachment faults, or the syn-rift interval being too thin to resolve on seismic data. The syn-rift episode beneath the deep Galicia margin postdates Tithonian-Berriasian shallow-water carbonates, and predates Late Valanginian turbiditic sediments. Drilling results from the Iberia Abyssal Plain suggest a similar age because Tithonian siliciclastic mudrocks are overlain by Berriasian pelagic chalks. It seems likely that in both regions rifting lasted for <5 Ma, probably from late Berriasian to early Valanginian. At Site 1068 in the Iberia Abyssal Plain, the interpretation from seismic reflection data, of a low-angle detachment dipping about 10° west, was confirmed by drilling, which revealed sedimentary and tectonic breccias containing clasts of lower-crustal rocks overlying a fault zone below which occurs serpentinized periodotite showing a downward decrease in deformation. At least 20.5 km of displacement is interpreted to have occurred along this fault, but it is not accompanied by large-amplitude, rift-related topography. This paradox is resolved if the detachment developed as a deepening-downwards, rolling-hinge fault.
Serpentinization and magmatism during extension at non-volcanic margins: the effect of initial lithospheric structure
Authors: Pérez-Gussinyé M. , Reston T.J. , Phipps Morgan J. 
Published: April 2008

Abstract

At several non-volcanic margins serpentinized peridotites occur within a wide continent-ocean transition (COT) and beneath the edge of the thinned continental crust. However, other margins such as the Woodlark Basin appear to have a sharp COT and no reported serpentinites. We investigate the thermal, magmatic and rheological evolution of margins during extension as a function of initial lithospheric structure, rift duration and stretching factor. For cratonic and old orogen models, the entire crust should become brittle at stretching factors
c.
3–4. The resultant crust-cutting faults allow water to reach and serpentinize the mantle, leading to the development of serpentinite décollements at the crust-mantle boundary and exhumation of mantle at the COT. Our predictions are consistent with the spatial limit and thickness of serpentinites at the SW Greenland and West Iberia margins, and the Rockall Trough. They also explain the absence of a broad zone of unroofed, serpentinized mantle at the COT of the Woodlark Basin: here the crust was too thick and hot for serpentinites to form before break-up. Larger melt production than in the West Iberia type margins and concentration of the lithospheric strength in the crust leads to synchronous crustal separation and lithospheric failure, yielding a sharp COT.
Three-dimensional GPR analysis of various Quaternary gravel-bed braided river deposits (southwestern Germany)
Authors: Heinz J. , Aigner T. 
Published: April 2008

Abstract
Closely spaced (1 m) ground penetrating radar (GPR) profiles were used for a three-dimensional characterization and comparison of glaciofluvial gravel-bed deposits in palaeodischarge zones of the Würmian Rhine glacier (southwestern Germany). Previous sedimentological outcrop investigations revealed three regionally reoccurring architectural styles of gravel bodies. For each of these styles a three-dimensional GPR dataset has been acquired in active gravel pits in order to calibrate the radar profiles with outcrop walls and to analyse, in three dimensions, the depositional elements and their stacking pattern in the subsurface.
The GPR data were interpreted by mapping reflection terminations in order to delineate genetically related units. In particular, radar facies types and radar sequence boundaries were used to define and map depositional elements. Both accretionary and cut-and-fill depositional elements could be identified. Accretionary elements are characterized by horizontally to low-angle inclined (1–3°) and moderately continuous reflections (5–30 m) terminating on flat sequence boundaries; they represent the deposits of gravel sheets and traction carpets. In contrast, cut-and-fill elements are characterized by low to steeply inclined (3–25°), often discontinuous reflections terminating on concave to trough-shaped lower truncation boundaries; these are interpreted as scour-pool fills and small dissection elements (e.g. chutes and lobes).
The three basic architectural styles of gravel bodies can be distinguished on the basis of the size and proportion of cut-and-fill elements mapped within the radar images. One type of gravel body is composed of an amalgamation of large cut-and-fill elements whereas the other two types are dominated by accretionary elements and differ by the proportion of smaller cut-and-fill elements.
The results show that GPR is an adequate technique to illuminate the sedimentary architecture of the various types of gravel bodies. GPR data allow detailed three-dimensional reconstruction of depositional elements and their stacking pattern in the subsurface.
Cenozoic sedimentation and tectonics in Borneo: climatic influences on orogenesis
Authors: Hall Robert , Nichols Gary 
Published: April 2008

Abstract
The volume of sediment deposited in the basins around Borneo indicates that at least 6 km of crust has been removed by erosion during the Neogene. The amount of tectonic uplift implied by this is not reflected in a large area of high mountains on the island, which has an average elevation much lower than that of the Alps or Himalayas. High weathering and erosion rates in the tropical climate of SE Asia are likely to have been an important factor governing the formation of relief in Borneo, and consequently, controlled the structural development of the orogenic belt. Very rapid removal of material by erosion prevented tectonic denudation by fauling: around Borneo there was no lithospheric flexure due to thrust loading and no true foreland basins were developed. The sediment was deposited adjacent to the orogenic belt in older, deep oceanic basins. In terms of sediment yield, the Borneo mountains are comparable in importance to mountain ranges such as the Alps or Himalayas. However, the differences in elevation and structural style suggest that mountain belts formed in regions of high erosion rates may be different from those formed in other settings and the effects of climate need to be considered to understand orogenic evolution.
Filling and cannibalization of a foredeep: the Bradanic Trough, Southern Italy
Authors: Tropeano Marcello , Sabato Luisa , Pieri Piero 
Published: April 2008

Abstract
The Bradanic Trough (southern Italy) is the Pliocene-present-day south Apennines foredeep. It is a foreland basin as subsidence due to westward subduction of the Adria Plate involves the continental crust of the Apulian domain. The infill succession of the Bradanic Trough is characterised by the presence of a long thrust sheet system (the so called ‘allochthon’) that occupied part of the accommodation space created on the foreland by subduction. The upper part of the infilling succession crops out along numerous sections. About 600 m of the 3–4 km basin-fill succession is exposed as the Bradanic Trough has experienced uplift during Quaternary times.
Outcropping successions are mainly characterized by shallow-marine deposits comprising carbonates of the Calcarenite di Gravina Formation, silty clay hemipelagites of the Argille subappennine Formation and coarse-grained bodies of the ‘Regressive coastal deposits’.
The Calcarenite di Gravina Formation (Middle-Late Pliocene-Early Pleistocene in age) crops out in a backstepping configuration onto the flanks of the Apulian Foreland highs. It displays evidence of strong transgression onto a karstic region previously dissected in a complex horst and graben system.

The Argille subappennine Formation (Late Pliocene-Middle Pleistocene in age) succeeds the carbonate sedimentation on the foreland side of the basin and represents the shallowing of the basin in the other sectors of the Bradanic Trough. Toward the Apennines chain, in the wedge-top area of the foredeep, the Argille subappennine Formation covers the allochthon, while in the depocentre (in the foredeep
sensu stricto
) the same formation overlays turbidite deposits. The latter characterize the deeper part of the successions, and are mainly buried below the allochthon.

The Regressive coastal deposits (Early-Late Pleistocene in age) represent the upper part of the succession. They consist of coarse-grained wedges that lie on the hemipelagites of the Argille subappennine Formation in, alternatively, conformable or erosional contact. The wedges of the Regressive coastal deposits stack in a downward-shifting configuration, which indicates deposition during uplift.
The Quaternary development of the Bradanic Trough differs from that of the central and northern Appennines foredeep. The latter is characterized by aggradation of shallow-marine and alluvial sediments in a subsiding remnant basin, whose filling records a basin-scale depositional regression. In contrast, the Bradanic Trough is characterized by a basin-scale erosional regression and the last evolutive phase of this sector of the Apennines foredeep is best defined as a cannibalization phase rather than a filling or overfilling phase.
Fluviatile sediment fluxes to the Mediterranean Sea: a quantitative approach and the influence of dams
Authors: Poulos S. E. , Collins M. B. 
Published: April 2008

Abstract

The Mediterranean drainage basin incorporates more than 160 rivers with a catchment >200 km
2
, of which only a few are larger than 50 × 10
3
km
2
: this observation emphasizes the role of the smaller rivers. The present investigation, incorporating the analysis of data sets from 69 rivers, has estimated a total sediment flux of some 1 × 10
9
tonnes (t) year
−1
; of this, suspended sediment contributes some two-thirds of the load, with the remaining third supplied by the combined dissolved and bed-load components. The magnitude of the sediment supply is best demonstrated by various observations: (i) some 46% of the total length of the Mediterranean coastline (46 133 km) has been formed by sediment deposition; (ii) many Mediterranean deltas have prograded in recent times by, at least, several metres per year; and (iii) Holocene coastal (inner shelf) deposits are some tens of metres in thickness. The construction of hundreds of dams around the Mediterranean Sea, especially over the last 50 years, has led to a dramatic reduction in the sediment supply- to approximately 50% of the potential (natural) sediment supply. Such a reduction is considered to be the primary factor responsible for the loss of coastal (mainly deltaic) land, with annual rates of erosion ranging from tens (Ebro, Po) to hundreds of metres (Nile).
Sedimentology: from single grains to recent and past environments: some trends in sedimentology in the twentieth century
Authors: Eugen  , Seibold Ilse 
Published: April 2008

AbstractBefore 1900, Henry Clifton Sorby, the ‘founder of sedimentary petrography’, covered many aspects of the study of sedimentary rocks. During the first half of the twentieth century, there followed numerous detailed descriptions of such rocks and actualistic ideas were increasingly introduced. Specialization began between the two World Wars. The use of single grains and their statistical evaluation, especially of heavy minerals, and the investigation of clay minerals, were stimulated by the needs of the oil industry, together with regional descriptions, including facies studies on land and on the sea bottom. Specialization further increased between 1945 and 1968, with an explosion of publications. Ongoing field and laboratory studies, and new concepts such as the origin of turbidites, or diagenesis — especially in carbonate rocks — were treated in much greater detail. Again the oil industry was one of the major driving forces. Since 1968, global aspects gained greater attention, as for example with the Deep-sea Drilling Project. Geophysics contributed to facies and basin analysis. Extraterrestrial factors such as variation in Earth’s orbit or bolide impacts, and their indications in sediments, came to be considered important for understanding world climates, and also evolution. Cross-disciplinary and international approaches have become, and continue to be, of growing importance.