Stress in the lithosphere: Inferences from steady state flow of rocks   总被引：9，自引：0，他引：9  

Jean-Claude C. Mercier  Douglas A. Anderson  Neville L. Carter 《Pure and Applied Geophysics》1977,115(1-2):199-226

Mechanical data and flow processes from steady state deformation experiments may be used to infer the state of stress in the lithosphere and asthenosphere. Extrapolations of flow equations to a representative geologic strain rate of 10^–14/sec. for halite, marble, quartzite, dolomite, dunite and enstatolite are now warranted because the steady state flow processes in the experiments are identical to those in rocks and because the geotherms are reasonably well established. More direct estimates are obtained from free dislocation densities, subgrain sizes and recrystallized grain sizes all of which are functions only of stress. Using the last of these techniques, we have estimated stress profiles as a function of depth from xenoliths in basalts and kimberlites, whose depths of equilibration were determined by pyroxene techniques, from four different areas of subcontinental and suboceanic upper mantle. The results are similar and indicate stress differences of about 200 to 300 bars at 40 to 50 km, decaying to a few tens of bars at depths betow 100 km. These stresses are reasonable and are in accord with extrapolations of the mechanical data provided that allowance is made for a general increase in strain rate and decrease in viscosity with depth.  相似文献   

Genetic implications of the isotope and trace element variations in the eastern Sicilian volcanics     

S.R. Carter  L. Civetta 《Earth and Planetary Science Letters》1977,36(1):168-180

Sr- and Pb-isotope compositions and Rb, Sr, Ce, Nd and K₂O contents have been determined for the Iblean Mountain and Mt. Etna volcanics in eastern Sicily. Isotope variations within each of these regions have been interpreted as reflecting the heterogeneous nature of the source regions in the upper mantle. The⁸⁷Sr/⁸⁶Sr ratios of all these volcanics are less than 0.705, which is taken to indicate that their source regions evolved with lower Rb/Sr ratios than the bulk earth.⁸⁷Sr/⁸⁶Sr and Ce/Nd ratios determined in the Mt. Etna tholeiites are positively correlated suggesting that fractionation(s) in Rb/Sr are accompanied by fractionation(s) in light REE in the source regions of these volcanics. Pb-isotope compositions form a linear array in the²⁰⁷Pb/²⁰⁴Pb-²⁰⁶Pb/²⁰⁴Pb plot which has a negative age slope. This array represents either a very recent U/Pb fractionation in the source regions, or a mantle mixing line. Imperfect correlation between the Sr- and Pb-isotope compositions of these volcanics suggests that U/Pb and Rb/Sr have not always increased or decreased in unison during the differentiation of these source regions.  相似文献   

Oligocene uplift of the Western Greater Caucasus: an effect of initial Arabia–Eurasia collision     

Stephen J. Vincent  Andrew C. Morton  Andrew Carter  Samantha Gibbs  Teimuraz G. Barabadze 《地学学报》2007,19(2):160-166

The Greater Caucasus is Europe's largest mountain belt. Significant uncertainties remain over the evolution of the range, largely due to a lack of primary field data. This work demonstrates that depositional systems within the Oligocene–Early Miocene Maykop Series on either side of the Western Greater Caucasus (WGC) display a similar provenance and divergent palaeocurrents away from the range, constraining a minimum age for the subaerial uplift of the range as early Early Oligocene. An Eocene–Oligocene hiatus, basal Oligocene olistostromes and a marked increase in nannofossil reworking also point to initial deformation in the earliest Oligocene. The initial uplift of the WGC occurred during the final assembly of the Tethysides to its south. Uplift commenced after the Late Eocene final suturing of northern Neotethys and during the initial collision of Arabia with the southern accreted margin of Eurasia. This suggests that compressional deformation was rapidly transferred across the collision zone from the indenting Arabian plate to its northern margin.  相似文献   

A composite Fe,Ni‐FeS and enstatite‐forsterite‐diopside‐glass vitrophyre clast in the Larkman Nunatak 04316 aubrite: Origin by pyroclastic volcanism     

Klaus KEIL  Timothy J. McCOY  Lionel WILSON  Jean‐Alix BARRAT  Doug RUMBLE  Matthias M. M. MEIER  Rainer WIELER  Gary R. HUSS 《Meteoritics & planetary science》2011,46(11):1719-1741

Abstract– We studied the mineralogy, petrology, and bulk, trace element, oxygen, and noble gas isotopic compositions of a composite clast approximately 20 mm in diameter discovered in the Larkman Nunatak (LAR) 04316 aubrite regolith breccia. The clast consists of two lithologies: One is a quench‐textured intergrowth of troilite with spottily zoned metallic Fe,Ni which forms a dendritic or cellular structure. The approximately 30 μm spacings between the Fe,Ni arms yield an estimated cooling rate of this lithology of approximately 25–30 °C s^?1. The other is a quench‐textured enstatite‐forsterite‐diopside‐glass vitrophyre lithology. The composition of the clast suggests that it formed at an exceptionally high degree of partial melting, perhaps approaching complete melting, and that the melts from which the composite clast crystallized were quenched from a temperature of approximately 1380–1400 °C at a rate of approximately 25–30 °C s^?1. The association of the two lithologies in a composite clast allows, for the first time, an estimation of the cooling rate of a silicate vitrophyre in an aubrite of approximately 25–30 °C s^?1. While we cannot completely rule out an impact origin of the clast, we present what we consider is very strong evidence that this composite clast is one of the elusive pyroclasts produced during pyroclastic volcanism on the aubrite parent body ( Wilson and Keil 1991 ). We further suggest that this clast was not ejected into space but retained on the aubrite parent body by virtue of the relatively large size of the clast of approximately 20 mm. Our modeling, taking into account the size of the clast, suggests that the aubrite parent body must have been between approximately 40 and 100 km in diameter, and that the melt from which the clast crystallized must have contained an estimated maximum range of allowed volatile mass fractions between approximately 500 and approximately 4500 ppm.  相似文献   

The initial responses of hot liquid water released under low atmospheric pressures: Experimental insights     

Alistair Simon Bargery  Alexander Barrett  Lionel Wilson  Jennie S. Gilbert 《Icarus》2010,210(1):488-506

Experiments have been performed to simulate the shallow ascent and surface release of water and brines under low atmospheric pressure. Atmospheric pressure was treated as an independent variable and water temperature and vapor pressure were examined as a function of total pressure variation down to low pressures. The physical and thermal responses of water to reducing pressure were monitored with pressure transducers, temperature sensors and visible imaging. Data were obtained for pure water and for solutions with dissolved NaCl or CO₂. The experiments showed the pressure conditions under which the water remained liquid, underwent a rapid phase change to the gas state by boiling, and then solidified because of removal of latent heat. Liquid water is removed from phase equilibrium by decompression. Solid, liquid and gaseous water are present simultaneously, and not at the 611 Pa triple point, because dynamic interactions between the phases maintain unstable temperature gradients. After phase changes stop, the system reverts to equilibrium with its surroundings. Surface and shallow subsurface pressure conditions were simulated for Mars and the icy satellites of the outer Solar System. Freezing by evaporation in the absence of wind on Mars is shown to be unlikely for pure water at pressures greater than c. 670 Pa, and for saline solutions at pressures greater than c. 610 Pa. The physical nature of ice that forms depends on the salt content. Ice formed from saline water at pressures less than c. 610 Pa could be similar to terrestrial sea ice. Ice formed from pure water at pressures less than c. 100 Pa develops a low thermal conductivity and a ‘honeycomb’ structure created by sublimation. This ice could have a density as low as c. 450 kg m⁻³ and a thermal conductivity as low as 1.6 W m⁻¹ K⁻¹, and is highly reflective, more akin to snow than the clear ice from which it grew. The physical properties of ice formed from either pure or saline water at low pressures will act to reduce the surface temperature, and hence rate of sublimation, thereby prolonging the lifespan of any liquid water beneath.  相似文献   

Formation of an eroded lava channel within an Elysium Planitia impact crater: Distinguishing between a mechanical and thermal origin     

Debra M. Hurwitz  Caleb I. Fassett  James W. Head  Lionel Wilson 《Icarus》2010,210(2):626-634

A lava channel identified on the wall of an Elysium Planitia impact crater is investigated to identify the dominant erosion mechanism, mechanical vs. thermal, acting during channel formation. Observations of channel morphology are used to supplement analytical models of lava channel formation in order to calculate the duration of channel formation, the velocity of the lava flowing through the channel, and the erosion rate in each erosion regime considered. Results demonstrate that the channel observed in the Elysium Planitia impact crater formed primarily due to mechanical erosion. In a more general sense, results of this study suggest that lava channels can form primarily due to thermal erosion in the presence of more gradual slopes and more consolidated substrates whereas lava channels can form primarily due to mechanical erosion in the presence of more energetic flows on steeper slopes and more poorly consolidated substrates. Therefore, both erosion regimes must be considered when analyzing origins of eroded lava channels that cut through strata of different strengths.  相似文献   

Enhancing the relevance of Shared Socioeconomic Pathways for climate change impacts,adaptation and vulnerability research   总被引：1，自引：1，他引：0  

Bas J. van Ruijven  Marc A. Levy  Arun Agrawal  Frank Biermann  Joern Birkmann  Timothy R. Carter  Kristie L. Ebi  Matthias Garschagen  Bryan Jones  Roger Jones  Eric Kemp-Benedict  Marcel Kok  Kasper Kok  Maria Carmen Lemos  Paul L. Lucas  Ben Orlove  Shonali Pachauri  Tom M. Parris  Anand Patwardhan  Arthur Petersen  Benjamin L. Preston  Jesse Ribot  Dale S. Rothman  Vanessa J. Schweizer 《Climatic change》2014,122(3):481-494

This paper discusses the role and relevance of the shared socioeconomic pathways (SSPs) and the new scenarios that combine SSPs with representative concentration pathways (RCPs) for climate change impacts, adaptation, and vulnerability (IAV) research. It first provides an overview of uses of social–environmental scenarios in IAV studies and identifies the main shortcomings of earlier such scenarios. Second, the paper elaborates on two aspects of the SSPs and new scenarios that would improve their usefulness for IAV studies compared to earlier scenario sets: (i) enhancing their applicability while retaining coherence across spatial scales, and (ii) adding indicators of importance for projecting vulnerability. The paper therefore presents an agenda for future research, recommending that SSPs incorporate not only the standard variables of population and gross domestic product, but also indicators such as income distribution, spatial population, human health and governance.  相似文献   

Avalanche and landslide simulation using the material point method: flow dynamics and force interaction with structures   总被引：3，自引：0，他引：3  

Carter M. Mast  Pedro Arduino  Gregory R. Miller  Peter Mackenzie-Helnwein 《Computational Geosciences》2014,18(5):817-830

In this paper, the material point method (MPM) is presented as a tool for simulating large deformation, gravity-driven landslides. The primary goal is to assess the interaction of these flow-like events with the built environment. This includes an evaluation of earthen mounds when energy dissipating devices are placed in the path of a snow avalanche. The effectiveness of the embankments is characterized using displacement, velocity, mass, and energy measures. A second example quantifies the force interaction between a landslide and a square rigid column. Multiple slide approach angles are considered, and various aspects of the impact force are discussed.  相似文献   

Towards a climate event stratigraphy for New Zealand over the past 30 000 years (NZ‐INTIMATE project)     

Brent V. Alloway  David J. Lowe  David J. A. Barrell  Rewi M. Newnham  Peter C. Almond  Paul C. Augustinus  Nancy A. N. Bertler  Lionel Carter  Nicola J. Litchfield  Matt S. McGlone  Jamie Shulmeister  Marcus J. Vandergoes  Paul W. Williams  NZ‐INTIMATE members 《第四纪科学杂志》2007,22(1):9-35

It is widely recognised that the acquisition of high‐resolution palaeoclimate records from southern mid‐latitude sites is essential for establishing a coherent picture of inter‐hemispheric climate change and for better understanding of the role of Antarctic climate dynamics in the global climate system. New Zealand is considered to be a sensitive monitor of climate change because it is one of a few sizeable landmasses in the Southern Hemisphere westerly circulation zone, a critical transition zone between subtropical and Antarctic influences. New Zealand has mountainous axial ranges that amplify the climate signals and, consequently, the environmental gradients are highly sensitive to subtle changes in atmospheric and oceanic conditions. Since 1995, INTIMATE has, through a series of international workshops, sought ways to improve procedures for establishing the precise ages of climate events, and to correlate them with high precision, for the last 30 000 calendar years. The NZ‐INTIMATE project commenced in late 2003, and has involved virtually the entire New Zealand palaeoclimate community. Its aim is to develop an event stratigraphy for the New Zealand region over the past 30 000 years, and to reconcile these events against the established climatostratigraphy of the last glacial cycle which has largely been developed from Northern Hemisphere records (e.g. Last Glacial Maximum (LGM), Termination I, Younger Dryas). An initial outcome of NZ‐INTIMATE has been the identification of a series of well‐dated, high‐resolution onshore and offshore proxy records from a variety of latitudes and elevations on a common calendar timescale from 30 000 cal. yr BP to the present day. High‐resolution records for the last glacial coldest period (LGCP) (including the LGM sensu stricto) and last glacial–interglacial transition (LGIT) from Auckland maars, Kaipo and Otamangakau wetlands on eastern and central North Island, marine core MD97‐2121 east of southern North Island, speleothems on northwest South Island, Okarito wetland on southwestern South Island, are presented. Discontinuous (fragmentary) records comprising compilations of glacial sequences, fluvial sequences, loess accumulation, and aeolian quartz accumulation in an andesitic terrain are described. Comparisons with ice‐core records from Antarctica (EPICA Dome C) and Greenland (GISP2) are discussed. A major advantage immediately evident from these records apart from the speleothem record, is that they are linked precisely by one or more tephra layers. Based on these New Zealand terrestrial and marine records, a reasonably coherent, regionally applicable, sequence of climatically linked stratigraphic events over the past 30 000 cal. yr is emerging. Three major climate events are recognised: (1) LGCP beginning at ca. 28 000 cal. yr BP, ending at Termination I, ca. 18 000 cal. yr BP, and including a warmer and more variable phase between ca. 27 000 and 21 000 cal. yr BP, (2) LGIT between ca. 18 000 and 11 600 cal. yr BP, including a Lateglacial warm period from ca. 14 800 to 13 500 cal. yr BP and a Lateglacial climate reversal between ca. 13 500 and 11 600 cal. yr BP, and (3) Holocene interglacial conditions, with two phases of greatest warmth between ca. 11 600 and 10 800 cal. yr BP and from ca. 6 800 to 6 500 cal. yr BP. Some key boundaries coincide with volcanic tephras. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Where Is the PFAS? Innovations in PFAS Detection and Characterization     

John Horst  Craig Divine  Joe Quinnan  Johnsie Lang  Erika Carter  Theresa Guillette  Vivek Pulikkal 《Ground Water Monitoring & Remediation》2022,42(1):13-23

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