bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contrasting glacial sedimentation processes and sea-level changes in two adjacent basins on the Pacific margin of Canada
Authors: Barrie J. Vaughn , Conway Kim W. 
Published: April 2008

Abstract

During the late Wisconsin Fraser Glaciation on the Pacific Margin of Canada, ice moved offshore from the Coast Mountains of the Canadian Cordillera and south into the Strait of Georgia, reaching a maximum extent at about 14 000
14
C
bp
. Most of the strait was ice-free by 11 300
14
C
bp
. Deglaciation was very rapid with regional downwasting and widespread stagnation. This resulted in a stratigraphy of thick till (30–60 m), overlain by ice-proximal glacimarine sediments and a thin and discontinuous ice-distal glacimarine unit. Glaciation of Queen Charlotte Basin reached a maximum sometime after 21 000
14
C
bp
. Deglaciation in this region began sometime after 16 000 to 15 000
14
C
bp
and ice had retreated fully onto mainland British Columbia by 13 500
14
C
bp
. Deglaciation was rapid, with the eastward retreat of an ice shelf. This resulted in a stratigraphy of a till up to 50 m in thickness, usually turbated by iceberg scour and overlain in some areas by thin, ice-proximal glacimarine sediments and much thicker (20 m) widespread ice-distal glacimarine sediments. A significant difference between these two regions is the deglacial relative sea-level history. Rapid regression of the outer Queen Charlotte Islands shelf occurred between approximately 14 600 and 12 500
14
C
bp
, primarily due to rapid isostatic rebound and contemporaneous with deglaciation of the continental shelf. Sea-level reached a maximum lowstand of greater than 150 m and remained low until approximately 12 400
14
C
bp
. In Georgia Basin, sea-level was at a relative high stand of 50 to 200 m during initial deglaciation, falling to between 0 to 50 m below present sometime after 10 000
14
C
bp
. We suggest that rapid emergence on the northern margin of the outer shelf was due to forebulge effects. Further, the very limited extent of glacial ice on the Queen Charlotte Islands and the exposure to the open Pacific forced the retreat of the Cordilleran ice-sheet margin eastwards thereby resulting in dominantly ice-distal glacimarine sedimentation. In contrast, the initial relative sea-level highstand during deglaciation between the Vancouver Island and Cordilleran glaciers in the Strait of Georgia resulted in significant ice-proximal deposition and limited ice-distal glacimarine deposition.
Developing high-resolution chronologies in glacimarine sediments: examples from southeastern Alaska
Authors: Jaeger John M. 
Published: April 2008

Abstract

Glacial systems release sediment to the marine environment over a range of time periods, including short-term seasonal, tidal, and diurnal scales. Often, the sedimentary record providing the highest temporal resolutions of short-term processes is found in relatively inaccessible areas such as proximal to glacier termini or below floating ice sheets. To assess the importance of short-term glacial and oceanographic processes in creating glacimarine strata, it is necessary to evaluate strata production over similar time scales. Time-series coring, sediment traps, or bathymetric profiles may be difficult to perform in these harsh settings. Coupling the observations of sedimentary structures seen in core X-ray radiographs with sound chronologies allows for the evaluation of short-term glacimarine sedimentation. For seasonal time-scales, the highly particle-reactive radioisotope
234
Th (24 day half-life) can be used to measure the rates of strata production under both steady and non-steady sediment deposition. To create appropriate age-depth relationships, two approaches are used: a rigorous and exacting mathematical model developed from a steady-state transport-reaction equation; and the less exacting CIC (constant initial concentration) and CRS (constant rate of supply or constant flux) point transformations. These methods are used for developing chronologies of cores collected in 1995 in Icy Bay, Alaska at 4, 12, and 32 km from the tidewater terminus of the Guyot Glacier. Examples are given of the boundary conditions that must be satisfied to use each approach in developing age-depth relationships. For the two cores collected closest to the terminus, age-depth relationships can be generated using all three approaches, whereas the presence of bioturbation in the most ice-distal sample severely complicates matters. The high (∼0.5 cm d
−1
) but non-steady sedimentation rates at the ice-proximal station create a high-resolution sedimentary record. The controls on sedimentation at this location are evaluated by examining sedimentary structures (alternating light and dark laminae and beds) seen in digitized X-ray radiographs. The CRS method is used to convert depth to time in X-ray radiographs. The down-core pixel intensities of the grey-scale X-ray radiograph positives are used to create a time series of sedimentation reflected in proxy data (the bulk density of the sediments). By using Blackman-Tukey spectral analyses and relatively new wavelet techniques to evaluate periodic processes, sedimentation at this location can be related to seasonal variability in meltwater production, fortnightly tidal influences on particle settling rates, and episodic precipitation-induced sediment deposition.
Retreat signature of a polar ice stream: sub-glacial geomorphic features and sediments from the Ross Sea, Antarctica
Authors: Shipp Stephanie S. , Wellner Julia S. , Anderson John B. 
Published: April 2008

Abstract

Three research expeditions to the Ross Sea, Antarctica resulted in collection of a dataset of more than 270 km of side-scan and chirp-sonar data, more than 330 km of swath bathymetry and 3.5 kHz data, and 24 cores within a glacially-carved trough. The former ice-stream flow path is divided into six zones, covering a distance of approximately 370 km, distinguished by unique stratigraphic signatures and geomorphic features. An erosional surface with thin, patchy lodgement till characterizes Zone 1. This region is interpreted as having experienced relatively high basal shear stress conditions. Zones 2, 3, and 4 are characterized by an erosional surface and thin, time-transgressive subglacial and grounding-line proximal deposits that include back-stepping moraines, flutes, transverse moraines, and corrugation moraines. These zones represent the transition between erosional and depositional regimes under the expanded LGM ice sheet; material eroded from the inner shelf was transported toward the outer shelf, possibly as a thin deforming till layer. The two outer zones are depositional and include maximum grounding-line (Zone 5) and pro-glacial deposits that were overridden subsequently by the ice sheet (Zone 6). Surface features include mega-scale glacial lineations, corrugation moraines, and iceberg furrows. Ice in these zones is interpreted as having experienced relatively lower basal shear stress, an extensional regime, and faster flow. This advance may have destabilized the ice sheet, initiating local draw-down and production of icebergs that furrowed the sea floor. Corrugation moraines are thought to represent annual retreat moraines, constraining the retreat rate of the ice sheet across the continental shelf to a consistent 40 to 100 m a
−1
.
The timing and location of major ore deposits in an evolving orogen: the geodynamic context
Authors: Blundell Derek J. 
Published: April 2008

Abstract
Although it is possible to identify the potential controls on mineralization, the problem remains to identify the critical factors. Very large mineral deposits are rare occurrences in the geological record and are likely to have resulted from the combination of an unusual set of circumstances. When attempting to understand the mineralization processes that occurred to form a major ore deposit in the geological past, especially the reasons why the deposit formed at a particular time and location within an evolving orogenic system, it is instructive to look at mineralization in modern, active subduction complexes. There it is possible to measure and quantify the rates at which both tectonic and mineralizing processes occur. In a complex subduction system, regions of extension develop. For example, subduction hinge retreat is a process that creates extension and generates heat from the upwelling of hot asthenosphere ahead of the retreating slab, producing partial melting, magmatism and associated mineralization. Seismic tomography not only images mantle as it is now, but subduction slab anomalies can be interpreted in terms of the past history of subduction. This can be used to test tectonic plate reconstructions. Tectonic and magmatic events occur rapidly and are of short duration so that many are ephemeral and will not be preserved. Furthermore, they can be diachronous as is the case with the lithospheric slab tear clockwise around the Carpathian Arc during the Neogene.
If the tectonic setting is paramount in determining the onset of the mineralization process and generation of mineralizing fluids, the fluid transport system that localizes the mineralization in space and time and concentrates the metal charge is the key to finding when and where the ore deposits occur. Fault and fracture networks in the crust provide various mechanisms for the localized expulsion of fluid in pulses of short duration. Excess surface water flow following large earthquakes in the Basin and Range region of USA offers a modern analogue to quantify fluid flow related to extensional faulting. Evidence from the Woodlark basin, east of Papua New Guinea, suggests that similar conditions pertain in the oceanic environment. Whilst there are limits to the use of regions of active tectonism as modern analogues to explain the mineralization of ancient orogenic systems, they do provide the best opportunity to understand the mechanisms of mineral processes and the controls on the location and timing of major ore deposits.
Auriferous arsenopyrite-pyrite and stibnite mineralization from the Siflitz-Guginock area (Austria): indications for hydrothermal activity during Tertiary oblique terrane accretion in the Eastern Alps
Authors: Amann G. , Paar W. H. , Neubauer F. , Daxner G. 
Published: April 2008

Abstract
Polymetamorphic schists and marbles of the Austroalpine Kreuzeck-Goldeck Complex are the host to auriferous arsenopyrite-pyrite as well as stibnite mineralization. In the Siflitz-Guginock area both types of mineralization are closely related spatially, but restricted to different lithologies. The auriferous arsenopyrite-pyrite mineralization is either disseminated or bound to quartz veins and strongly silicified fault-zones hosted in phyllites to (garnet-) micaschists. Similar disseminations within marbles are of minor importance. A stockwork-like mineralization of stibnite-filled fractures with weak metasomatic replacement is limited to marbles.
Both types of mineralization in the Kreuzeck-Goldeck Complex are intimately related to roughly east-west-trending semi-ductile to brittle strike-slip faults which formed during orogen-parallel wrenching. Semi-ductile to brittle kinematic indicators point to dextral, as well as sinistral, modes of fault movements, coeval with the formation of pyrite-arsenopyrite-bearing quartz veins, as well as the intrusion of Oligocene lamprophyre dykes. Mineralizing fluids are suggested to be derived from devolatilization of the subducted Penninic upper crust. Fluid ascent and ore precipitation is controlled by a transpressive strike-slip regime related to oblique terrane accretion during the Late Eocene to Oligocene.
Subsequent development of a Late Oligocene-Early Miocene pure shear regime with contraction trending (N)NE-(S)SW led to the development of conjugate NW-SE dextral and NE-SW sinistral brittle strike-slip faults, and overprinting by ESE-WNW oriented extension. These later events are related to the formation of auriferous mineralization from within the metamorphic core complex of the Tauern Window to the north of the Kreuzeck-Goldeck Complex, hence implying a significant change in spatial, temporal and structural control of Tertiary auriferous mineralization in the Eastern Alps.
40Ar/39Ar geochronology of magmatism and hydrothermal activity of the Madjarovo base-precious metal ore district, eastern Rhodopes, Bulgaria
Authors: Marchev Peter , Singer Brad 
Published: April 2008

AbstractThe Madjarovo volcanic complex and ore district comprise alteration styles from potassium silicate, advanced argillic and sericite alteration to adularia-sericite alteration/mineralization with a close and unambiguous spatial relationship to specific magmatic events. New40Ar/39Ar laser fusion and incremental heating experiments on nine sanidine, biotite, adularia, K-feldspar, and alunite samples constrain the ages and time span of lavas and tephras comprising the complex and their relationship to the hydrothermal activity. These results demonstrate that high-K calc-alkaline to shoshonitic volcanic activity beganc.32.7 Ma and terminatedc.500 ka later with the extrusion of quartz latite lavas at 32.2 Ma. The final stage of volcanism was accompanied by intrusion of compositionally similar monzonite stocks and trachytic dykes (c.32.2–32.1 Ma) and associated barren advanced argillic and sericite alteration (lithocap) and adularia-sericite base/precious metal vein mineralization. A probable thermal event atc.12–13 Ma disturbed the ages of alunite and sericite-bearing alteration at low stratigraphic levels. However, field relations combined with a plateau age of 32.1 ± 0.2 Ma from adularia in low-sulphidation veins that cross-cut lithocap indicate that hydrothermal activity, including base- and precious-metal vein deposition, was coeval with the youngest magmatic activity.
Discrimination criteria for assigning ore deposits located in the Dinaridic Palaeozoic-Triassic formations to Variscan or Alpidic metallogeny
Authors: Jurković Ivan , Palinkaš Ladislav A. 
Published: April 2008

Abstract
Among the ore deposits located in the Palaeozoic-Triassic formations of the Dinarides, siderite (± ankerite) and barite mineralization hosted by Carboniferous and Lower Permian sediments as well as polymetallic deposits in the Mid-Bosnian Schist Mts (MB), caused a long standing dispute concerning their metallogenic affiliation.
1.05–1.01 Ga Sveconorwegian metamorphism and deformation of the supracrustal sequence at Sæsvatn, South Norway: Re-Os dating of Cu-Mo mineral occurrences
Authors: Stein H. J. , Bingen B. 
Published: April 2008

Abstract
Re-Os dating of a suite of nine molybdenite samples from two small Cu-Mo mineral occurrences in the epidote-amphibolite facies Sæsvatn supracrustal sequence provides a temporal record of Sveconorwegian metamorphism and deformation. The sequence is situated in the western allochthonous lithotectonic domain of the Sveconorwegian orogen, the Rogaland-Hardangervidda terrane of south Norway. Onset of metamorphism occurred at about 1047 ± 2 Ma, as recorded in small gash veinlets, followed by a deformational peak at about 1032 ± 2 Ma, as recorded in mineralized breccia and mineralized metagabbro comprising a ductile shear zone constituting the Langvatn deposit. Deformation waned significantly by about 1017 ± 2 Ma, based on mineralization hosted in a brittle fault zone within stratigraphically higher metabasalts exposed at the Kobbernuten deposit. The origin of the mineralization at both deposits is most probably metamorphic with ore constituents provided by metasomatism of hosting basalt and gabbro. A metamorphic origin is supported by an array of Re-Os ages that can be related to structural features and the stratigraphic sequence, the absence of plutons related in time and space, the confinement of ore occurrences to mafic sequences in a bimodal supracrustal package that includes rhyolites and clastic units, and clear evidence for Cu mobility in mafic units. The ‘main’ Sveconorwegian orogenic event, probably a continent-continent collision involving imbrication, stacking, and burial of terranes took place at about 1.05 Ga and thereafter. Peak deformation in the Sæsvatn supracrustal sequence in the western part of the Sveconorwegian orogen (South Norway) may correlate with thermal metamorphism in the Idefjorden terrane in the eastern part of the orogen (SW Sweden), with a timing of about 1.03 Ga for both regions. The results of this study indicate that comparatively low grade domains in the orogen (greenschist to epidote-amphibolite facies), corresponding to upper crust, were deformed in a ductile fashion at about 1.03 Ga and were affected by brittle deformation as early as 1.025–1.015 Ga. In the high-grade domains (amphibolite to granulite facies), corresponding to middle and lower crust, ductile deformation is younger, beginning at about 1.025 Ga and persisting until 0.97 Ga.
Fluorine in orthoamphibole dominated Zn-Cu-Pb deposits: examples from Finland and Australia
Authors: Rajavuori Leena , Kriegsman Leo M. 
Published: April 2008

Abstract
Volcanogenic massive sulphide (VMS) deposits commonly occur within much larger fluorine (F)-bearing hydrothermal systems, where cordierite-orthoamphibole rocks are characteristic pathfinder assemblages. Here we report whole-rock and mineral F contents for orthoamphibole bearing rocks and associated rock types from Zn-Cu-Pb deposits in Finland (Orijärvi, Iilijärvi, Pyhäsalmi, Mullikkoräme) and central Australia (Oonagalabi). Textural and mineralogical data suggest that F influx predates peak metamorphism in these deposits.

The Mullikkoräme whole-rock data show positive correlations between F and X
Mg
= molar Mg/(Mg + Fe) and between F and elements of relatively low mobility (Ti, Al, Mg) and negative correlations between Fe and these elements. This suggests that iron was leached from silicate rocks by F-bearing fluids and was transferred to the Fe-rich sulphide ore. When normalized to immobile elements, F correlates positively with total metal content (Cu + Pb + Zn + Fe), consistent with the commonly observed increase of F content towards ore bodies.

Combining all microprobe data, hydrous minerals show the following order of decreasing F/(F + OH) ratio when coexisting: apatite > chondrodite > biotite > gedrite > (hornblende, muscovite, anthophyllite) > chlorite. The low- to medium-grade Finnish samples (Mullikkoräme: 500–560 °C at 1–3 kbar; Orijärvi: 550–650 °C at 3–5 kbar; Pyhäsalmi: 600–700 °C at 5–7 kbar) contain mainly F-poor anthophyllite, whereas F-rich gedrite is dominant in the higher grade Oonagalabi deposit (750–800 °C, 8–9 kbar). Temperature seems to have a significant, but X
Mg
a negligible influence on F partitioning between biotite and orthoamphiboles.
Continental growth in the Proterozoic: a global perspective
Authors: Windley Brian F. 
Published: April 2008

Abstract
During Proterozoic time, growth of the continents took place by the addition of mantlederived, juvenile material to pre-existing continental blocks. This accretion took place largely within three tectonic environments: (1) most importantly, in accretionary orogens such as the Birimian, the Baltic Shield, the Arabian-Nubian Shield and the early Altaids in Central Asia-these orogens grew largely by the accretion of island arcs, oceanic plateaus, accretionary prisms and ophiolites; (2) in the juvenile parts of collisional orogens as in the Trans-Hudson and Grenville; (3) within supercontinents that underwent rifting and breakup, giving rise to continental flood basalts and mafic dyke swarms. In addition to plate tectonics, the role of plume tectonics is increasingly emphasized as a fundamental process in Earth evolution. A mantle superplume may increase the oceanic spreading rate, the subduction rate and thus the island-arc production rate. It may also be responsible for the formation of a supercontinent, thus preserving the juvenile parts of collisional orogens, and it may be instrumental in the fragmentation of a supercontinent, giving rise to juvenile continental flood basalts. The balance between these processes is still poorly understood, as are calculated growth rates of Proterozoic crust.
Proterozoic-Cambrian history of Dronning Maud Land in the context of Gondwana assembly
Authors: Bauer W. , Thomas R. J. , Jacobs J. 
Published: April 2008

AbstractDronning Maud Land contains a fragment of an Archaean craton covered by sedimentary and magmatic rocks of Mesoproterozoic age, surrounded by a Late Mesoproterozoic metamorphic belt. Tectonothermal events at the end of the Mesoproterozoic and in Late Neoproterozoic-Cambrian times (Pan-African) have been proved within the metamorphic belt. In western Dronning Maud Land a juvenile Mesoproterozoic basement was accreted to the craton atc.1.1 Ga. Mesoproterozoic rocks were also detected by zircon SHRIMP dating of gneisses in central Dronning Maud Land, followed by a long hiatus for which geochronological data are lacking, an amphibolite to granulite facies metamorphism and syntectonic granitoid emplacement of Pan-African age have been dated. During this orogeny older structures were completely overprinted in a sinistral tranpressive deformation regime, leading to the mainly coast-parallel tectonic structures of the East Antarctic Orogen. Putting Antarctica back in its Gondwana position, the East Antarctic Orogen continues northward in East Africa as the East African Orogen, whereas a connection to the marginal Ross Orogen at the Pacific margin of East Antarctica is suggested along the Shackleton Range. The East Antarctic-East African Orogen resulted from closure of the Mozambique Ocean and collision of West and East Gondwana, i.e. western Dronning Maud Land was part of West Gondwana. During this collision the lithospheric mantle probably delaminated, allowing the asthenosphere to underplate the continental crust and producing heat for the voluminous, typically anhydrous, Pan-African granitoids of central Dronning Maud Land.
A review of the evolution of the Mozambique Belt and implications for the amalgamation and dispersal of Rodinia and Gondwana
Authors: Grantham G. H. , Maboko M. , Eglington B. M. 
Published: April 2008

Abstract

Geochronological, isotopic, lithological and structural data from the Mozambique Belt, and its extensions in Antarctica, Sri Lanka, India and Madagascar, are summarized and reviewed within a Gondwana framework. Much of the southern Mozambique Belt is dominated by Rodinian-Grenvillian-age juvenile magmatism and crustal genesis, with a strong metamorphic overprint during the Pan-African. Magmatism at
c.
800 Ma, possibly related to Rodinian fragmentation, is restricted to the Zambesi Belt, a few examples in northern Mozambique, southern Malawi, Tanzania, Madagascar and the Rayner Complex in Antarctica. Significantly, no crust of this age is recognized in western Dronning Maud Land. Amalgamation of Gondwana initially involved the closure of the Mozambique Ocean between the Tanzanian-Congo Cratons and the Madagascar-India-Enderby Cratons forming the East African Orogeny between
c.
580 and
c.
800 Ma. This was followed by the
c.
500–580 Ma transpressional sinistral collision of the combined Kalahari-East Antarctic Cratons and associated Grenville-age belts in the south, with the northern block comprising the combined Tanzanian-Congo-Madagascar-India-Enderby Block.