bluuebunny/crossref_metadata_2025_split huggingface dataset:
Miocene high-pressure metamorphic rocks of Crete, Greece: rapid exhumation by buoyant escape
Authors: Thomson Stuart N. , Stöckhert Bernhard , Brix Manfred R. 
Published: September 2007

Abstract

The pre-Neogene thrust sheets of Crete, Greece, accreted during Oligocene and Early Miocene time, can be divided into two main groups juxtaposed by a Miocene extensional detachment. Oligo-Miocene high pressure-low temperature (HP-LT) metamorphic rocks crop out in the lower plate to the detachment, and rocks that show no evidence of Tertiary metamorphism in the upper plate. Detailed pressure, temperature and structural information from the HP-LT metamorphic rocks combined with new fission-track data from the upper plate reveal that the lower plate rocks were subducted, then pervasively deformed and metamorphosed at their maximum depth of burial (30–35 km, 300–400°C) between
c.
24 and 19 Ma and then exhumed to less than 10 km depth at rates >4 km Ma
−1
before
c.
17 Ma. Microstructural studies reveal that during exhumation the lower plate acted as a coherent block, with deformation and retrograde metamorphism localized along the extensional detachment. The rocks of the upper plate can be shown to have remained in the upper 4–7 km of the crust since at least Eocene time. After cessation of movement along the main extensional detachment, both the upper and lower plates were subjected to brittle extension and increased erosion initiated at
c.
16–17 Ma. These boundary conditions imply continuous subduction retreat since at least Eocene time along the Aegean segment of the Hellenic convergent plate boundary. A tectonic model is presented where exhumation is driven by positive buoyancy of the subducted continental crust following lithospheric delamination. We propose that the subducted microcontinent was exhumed by a process of ‘oblique buoyant escape’ and entered the space created by the retreating subducting oceanic slab.
Spatial and temporal variations in exhumation of the central Swiss Alps and implications for exhumation mechanisms
Authors: Schlunegger Fritz , Willett Sean 
Published: September 2007

Abstract

Information about the structural and thermal evolution of the Alps, interpreted through thermal and mechanical models, provides an improved understanding of the processes that led to the exhumation of the Alps. We synthesize published thermochronometric data, analyse these data in terms of cooling rates and interpret the spatial and temporal patterns of cooling. Cooling rates are interpreted in terms of exhumation rates, aided by the use of a one-dimensional thermal model. Our study reveals that rapid exhumation of the Lepontine core occurred during the interval of 35-20 Ma. Existing data cannot determine whether this was by rapid erosion at rates exceeding 1 km Ma
−1
or by a relatively brief period of tectonic exhumation, although the correlation between extensional fault motion and high cooling rates supports the tectonic exhaumation hypothesis. Peripheral regions of the Alps cooled at rates consistent with low to moderate exhumation rates of 400–500 m Ma
−1
, initiating later than cooling of the Lepontine core, consistent with outward growth of the orogen. Outward growth of the orogen is potentially the result of either lower exhumation rates or higher rates of crustal accretion as demonstrated by a two-dimensional, coupled erosion-deformation model. In particular, the growth of the Southern Alps after
c.
20 Ma is evidence for a decrease in the exhumation rate relative to the crustal accretion rate. This could represent a decrease in exhumation rate after cessation of normal faulting, or it could reflect initiation of accretion of a larger fraction of the European crust.
Exhumation of migmatites in two collapsed orogens: Canadian Cordillera and French Variscides
Authors: Vanderhaeghe Olivier , Burg Jean-Pierre , Teyssier Christian 
Published: September 2007

Abstract
The Shuswap Metamorphic Core Complex in the Canadian Cordillera and the Velay Dome in the French Massif Central are examples of metamorphic core complexes formed in the hinterland of collapsed orogens. They display structural sections which allow the assessment of the efficiency of various exhumation mechanisms at different crustal levels. Erosion affected the relief generated during crustal thickening and redistributed the upper level of the mountain belt into nearby extensional basins or larger foreland basins. Faulting accommodated horizontal extension and laterla sliding of the upper crust. A detachment zone separates the upper brittle crust from ductilely deformed lower crust and achieved mechanical decoupling between these two major crustal layers. Below the detachment zone, the major fabric of high-grade rocks developed in the presence of melt and indicates vertical thinning along with horizontal extension. The lowest structural level exposed consists of migmatites which rose during crustal-scale boudinage of the overlying units and appear in the cores of dome-shaped culminations. The combination of these various exhumation mechanisms within a period of a few million years brought into close proximity migmatites which formed at depth of about 20–25 km and sediments deposited at the surface.
Geological and geochronological constraints on the exhumation of a high-pressure metamorphic terrane, Oman
Authors: Miller J. McL. , Gregory R. T. , Gray D. R. , Foster D. A. 
Published: September 2007

Abstract

New
40
Ar-
39
Ar age data from high-pressure former continental shelf rocks, now structurally beneath the Samail ophiolite, support a two-stage exhumation process for these rocks. High-
P
rocks occur as stacked fold-nappes within a less deformed upper plate and a strong to intensely deformed lower plate separated by a major, ductile, crustal discontinuity. The highest-grade lower plate rocks yield
40
Ar-
39
Ar ages that range from 82 to 131 Ma. The majority of these ages are inferred to represent cooling by the progressive emplacement of colder units during convergent margin tectonism, before emplacement to higher structural levels. In the lower plate, 82–79 Ma
40
Ar-
39
Ar ages are associated with lower-grade assemblages defining both transposition fabrics and C’-type shear bands which overprint the high-
P
assemblages during a NE-directed shearing event. Partial exhumation of these lower plate sequences resulted in the formation of regional closures by folding and transposition of earlier high-pressure fabrics. The lower plate closures are truncated by the structural break separating the two plates. Emplacement of the lower plate units to shallower crustal levels may have occurred before, or synchronously with, peak metamorphism of the upper plate units. The lower plate
40
Ar-
39
Ar cooling(?) ages are older than mica crystallization ages of 76–70 Ma from the upper plate. These upper plate micas grew in axial surface fabrics associated with regional-scale fold-nappes which formed during the exhumation of the upper plate units and their transport over the higher-grade lower plate units. This nappe-forming event was possibly synchronous with structurally higher low-angle normal faulting and/or rapid erosion of the nappe pile before the deposition of Maastrichtian autochthonous units at
c.
67–68 Ma.
Quantifying tectonic exhumation in an extensional orogen with thermochronology: examples from the southern Basin and Range Province
Authors: Foster David A. , John Barbara E. 
Published: September 2007

Abstract

The Colorado River extensional corridor is a region of large-scale crustal attenuation, where the integration of thermochronological techniques illuminates processes of extension and exhumation. Biotite and K-feldspar
40
Ar-
39
Ar, and zircon and apatite fission-track ages from metamorphic core complexes in the corridor consistently young in the displacement directions of detachment faults. The onset of rapid extension is denoted by an abrupt change, at
c.
22–21 Ma, in cooling rate derived from age-closure temperature plots, and in slope of age-distance gradients in footwalls. Linear age-distance trends with slopes of
c.
3–8 km Ma
−1
, for low-temperature thermochronometers, give time-averaged displacement rates on detachment faults. Gradients of mineral age across thick tilted hanging wall fault blocks reveal palaeotemperature gradients when the angle of tilting is known. Pre-extensional thermal gradients for tilted blocks in the southern Basin and Range province were
c.
20–25°C km
−1
, 17° ± 5°C km
−1
, and
c.
20–24°C km
−1
. Thermochronological data from the footwall of the Chemehuevi detachment fault reveal a trend of increasing temperature, in the known slip direction, from ≤200° to 350–400°C over an exposed distance of 23 km, at the onset of extension. The gradual increase in temperature constrains the Chemehuevi detachment fault to have had an original dip of
c.
15–30°, within the brittle upper crust.
The kinematics of back-arc basins, examples from the Tyrrhenian, Aegean and Japan Seas
Authors: Jolivet Laurent , Faccenna Claudio , D’Agostino Nicola , Fournier Marc , Worrall Dan 
Published: September 2007

AbstractThree classical examples of marginal basins are explored to show the respective contributions of body forces and far-field stresses to the extension mechanism. Extensional stresses can be provided by: (1) the slab-pull force, which induces a retreat of the slab and which originates in the density contrast between the subducting slab (oceanic or continental) and the asthenosphere; (2) by lateral density contrasts within the crust (due to crustal thickening), which induce crustal spreading; and (3) by far-field stresses due to intra-continental deformation (continent-continent collision, for example). Slab pull is probably the most efficient extensional force to provide but its effects are modulated by the contributions of the two other forces. The Japan Sea opened along the eastern margin of the Eurasian continent because extensional boundary conditions were provided by the retreating Pacific subduction zone. The opening stopped as soon as the central Japan triple junction was established in its present position which resulted in a more efficient coupling between the Pacific and Eurasian Plates through the Philippine Sea Plate. The geometry of opening was further controlled by large-scale dextral strike-slip faults that run oblique to the subduction zone along >2500 km, and which are far-field effects of the India-Asia collision. The Northern Tyrrhenian Sea opened because of the retreat of the Adriatic continental slab. The strong slab-pull force is probably due to phase changes within the subducting lower crust. Crustal delamination leads to a warm lower crust which localizes the extensional strain. This extending domain migrated with time from west to east as the delamination and slab retreat proceeded. Upper crustal units incorporated in the Apennines accretionary wedge were later exhumed in the collapsing back-arc domain where their deformation andP-Thistory can now be observed. A similar history with an outward migration can be proposed for the Aegean Sea with, however, a stronger influence of crustal collapse over a larger domain. Here too continental collision (the Arabia-Eurasia collision) controlled the geometry of opening through the westward propogation of the North Anatolian Fault.
Taconian seismogenic deformation in the Appalachian Orogen and the North American Craton
Authors: Rast Nicholas , Ettensohn Frank R. , Rast Diana E. 
Published: September 2007

Abstract
Originally the paradigm of plate tectonics was largely based on seismological interpretation of earthquakes. It therefore behoves that geological literature should pay more attention to the detection of seismic activity in ancient rocks. The effects of earthquakes on relatively young Tertiary and Holocene deposits have been recognized, commonly in the context of engineering works. In this paper, observational evidence for seismogenic structures in the Lower Palaeozoic carbonate belt of E. North America is presented. The structures range from minor faults and liquefaction effects to breccias and melanges. It is sometimes possible to suggest the dynamics of faults on which earthquakes occurred. Although most of the deformation happened at the margins of the craton and the growing orogenic belt, intracratonic faulting, earthquakes and synsedimentary deformation also took place.
The Northern Sacramento Mountains, southwest United States. Part I: Structural profile through a crustal extensional detachment system
Authors: Pease V. , Argent J. 
Published: September 2007

Abstract
Miocene exhumation of the Sacramento Mountains metamorphic core complex in the Colorado River extensional corridor, southwest United States, produced a range of deformational fabrics: pervasive, synthetic ductile deformation (with associated syntectonic intrusion) occurred at depth, discrete antithetic ductile through to brittle extensional shear zones developed at intermediate crustal levels and brittle cataclasis occurred at upper crustal levels. The region divides into three structural domains on the basis of these fabrics: (1) the eastern domain is dominated by a penetrative, ductile fabric with a consistent mineral alignment and stretching lineation, and sense of shear synthethic with detachment fault motion (top-to-northeast); (2) the central domain is characterized by a continuum of overprinting ductile through to brittle extensional shear zones with motion antithetic (topto-southwest) to detachment faulting; and (3) the western domain, where deformation occurred entirely by brittle cataclasis. Structural and petrofabric data from the Sacramento Mountains suggest that increasing structural depth/temperature is exposed in the direction of tectonic transport (N60E), consistent with detachment faulting. This region is interpreted as a profile through a crustal-scale shear zone in which the central domain of discrete antithetic shear zones formed in response to a combination of non-coaxial shear and vertical shortening, and represents an exhumed brittle-ductile transition. Rapid uplift and cooling of the northern Sacramento Mountains in the Miocene facilitated the preservation of this relatively transient regime.
Structural and magmatic segmentation of the Tertiary East Greenland Volcanic Rifted Margin
Authors: Karson Jeffrey A. , Brooks C. Kent 
Published: September 2007

Abstract

The Tertiary East Greenland Volcanic Rifted Margin is characterized by massive magmatic construction that produced a distinctive crustal architecture including: (1) a thick pile of flood basalts continuing offshore as seismically imaged ‘seaward-dipping reflector sequences’; (2) an extensive margin-parallel mafic dyke swarm; and (3) shallow crustal gabbroic plutons and deeper crustal ‘underplated’ material. These igneous units developed in the framework of an asymmetrical, crustal-scale fold, or ‘flexure’, that accommodated major subsidence along the continent-ocean transition. Extensive exposures along the margin reveal that the flexure and associated igneous structures define rift segments separated by various types of structural discontinuities. First-order segments occur between major triple-rift junctions as at Kangerlussuaq. At an intermediate scale, second-order accommodation zones bound margin segments
c.
100 km in length with long-lived structural and/or magmatic expressions. Third-order discontinuities, spaced at tens of kilometres, correspond to smaller accommodation zones at abrupt along-strike changes fault or magmatic structures. Outcrop-scale transfer and transform faults occur at still smaller scales. Some of the larger accommodation zones appear to be related to pre-existing Precambrian structures and may have helped localize relatively late, post-flexure alkalic intrusions. The style of segmentation provides a link between similar segmentation patterns in continental rifts and mid-ocean ridge spreading centres that persist long after continental separation.
Technical note: Thermal insulations for hot water cylinders: a review and a conceptual evaluation
Authors: Omer S.A. , Riffat S.B. , Qiu G. 
Published: September 2007

This paper presents a review and evaluation of thermal insulation materials for application in hot water storage cylinders. A range of thermal insulation materials including organic foams, inorganic insulations, composite insulations and vacuum insulation panels have been evaluated. The evaluation addressed parameters such as effects of insulation thickness on the energy saving and system cost. Vacuum insulation panels offered the best results in terms of energy saving and annualised system cost, given that the vacuum could be maintained at a desirable level throughout system lifetime. The overall evaluation indicates that polyisocyanurate (PIR) foam is the best overall single insulation material that could be applied for hot water storage cylinders when all the parameters including cost, thermophysical properties and environmental impact are taken into account. Microporous silica aerogel is more expensive than any other single insulation material that could be applied for hot water storage cylinders, but offers excellent performance in terms of reduced thickness and weight. When used in conjunction with PIR in a composite form, the combination offers a competitive performance in comparison with some of the conventional insulation materials, e.g. EPS, PU and glass fibre. Practical applications: The paper provides a comprehensive and compact summary and information on a range of thermal insulation materials for application in hot water storage cylinders. Although, the discussion is confined to hot water storage, the information is useful for a wide range of industries including construction industry, domestic appliance industry, technicians working in the above two industries and more importantly to R&D institutions. R&D institutions could directly benefit from the information provided in this paper, where the basic information and data are required to short list materials that should be given attention for further investigation for a given research area. Trade names normally dominate the industry with regards to material use; the paper provides basic scientific background on the origin of the thermal insulation materials, which are commonly known only by trade names within the industry, manufacturing processes, relative cost, their properties and related environmental impact. The paper provides awareness of other alternative insulation materials; that could be considered for a given application.
Numerical studies of displacement natural ventilation in multi-storey buildings connected to an atrium
Authors: Ji Y. , Cook M.J. 
Published: September 2007

This paper describes computational fluid dynamics (CFD) simulations used to investigate displacement natural ventilation in simple multi-storey spaces connected to an atrium. The purpose of the work is to demonstrate the potential of CFD for modelling these airflows using solutions from simple mathematical models and salt bath experiments to provide an indication of the accuracy that can be attained. The storeys are connected to an atrium and air flows into them via top-down-chimneys. The driving force is provided by localised point heat sources on each floor which generate buoyant plumes that entrain the surrounding air and transport warm air upwards forming a warm, stratified layer in each storey. The mathematical models are used to describe the main flow features, such as stratification height, temperature gradient and ventilation flow rate. Results showed that, using the RNG k — ε turbulence model, the predicted airflow patterns, temperature profiles and ventilation flow rates agreed favourably with the mathematical models, demonstrating the potential of using CFD for modelling buoyancy-driven displacement ventilation in multi-storey spaces connected to an atrium. Practical applications: Computer simulation programs have become valuable tools in the building design process, particularly of innovative buildings. This paper looks at the ability of CFD techniques to model buoyancy-driven natural ventilation in simple multi-storey spaces. The methods used in this paper provide a basis for others to use CFD for predicting natural ventilation in more complex, realistic building structures and are useful for both building designers and CFD practitioners.
The impact of palliative care on cancer deaths in Hong Kong: a retrospective study of 494 cancer deaths
Authors: Tse D.M.W. , Chan K.S. , Lam W.M. , Leu KS , Lam P.T. 
Published: September 2007

Objectives: To study the utilization of public health care by advanced cancer patients in their last 6 months of life and their end-of-life process within the last 2 weeks of life. Methods: This was a retrospective study on 494 cancer deaths from four public hospitals in 2005. This sample was selected from all in-patient cancer deaths by the ratio of one in four. Data were collected by review of charts and an electronic data base. Results: A total of 494 cancer deaths were analysed. The mean age of all cancer patients (n = 494) was 72.6 years. Two-thirds of cancer patients received palliative care and half died in palliative care setting. Patients were categorized into three groups according to palliative care coverage and the place of death. The first group comprised of patients who received palliative care service and died in palliative care units (PCS-PCD group, n = 247); the second group of patients who received palliative care service within the last 6 months of life but died in non-palliative care wards (n = 86); and the third group of patients who never received palliative care and who died in non-palliative care wards (NPCS-NPCD group, n = 161). Differences among groups were tested by one way ANOVA. During the last 6 months of life, patients in the PCS-PCD group had less admission to acute care wards (P = 0.012), shorter duration of stay in acute care wards (P = 0.003), and less admission to an intensive care unit setting (P < 0.001). Within the last 2 weeks of life, the PCS-PCD group had fewer interventions initiated (P < 0.001); had higher number of symptoms documented in patient's record (P < 0.001); and were more likely to receive analgesics (P < 0.001), adjuvant analgesics (P < 0.001) and sedatives (P < 0.001). Patients in PCS-PCD group were more physically dependent in the last 2 weeks of life (P < 0.001), but mentally more alert at 72 hours before death (P < 0.001). Patients in the NPCS-NPCD group had fewer patients with a do not resuscitate order present (P < 0.001), and more patients with cardiopulmonary resuscitation performed (P < 0.001). Conclusion: Our results suggest that palliative care service has played a role in improving end-of-life cancer care in Hong Kong. Palliative Medicine 2007; 21 : 425—433