Passive-margin prolonged volcanism,East Australian Plate: outbursts,progressions, plate controls and suggested causes     

F. L. Sutherland  I. T. Graham  S. Meffre  H. Zwingmann  R. E. Pogson 《Australian Journal of Earth Sciences》2013,60(7):983-1005

Prolonged intraplate volcanism along the 4000 km-long East Australian margin for ca 100 Ma raises many genetic questions. Studies of the age-progressive pulses embedded in general basaltic activity have spawned a host of models. Zircon U–Pb dating of inland Queensland central volcanoes gives a stronger database to consider the structure and origin of Australian age-progressive volcanic chains. This assists appraisal of this volcanism in relation to plate motion and plate margin tectonic models. Inland Queensland central volcanoes progressed south-southeast from 34 to 31 Ma (～5.4 cm/yr) until a surge in activity led to irregular southerly progression 31 to 28 Ma. A new inland southeastern Queensland central volcano line (25 to 22 Ma), from Bunya Mountains to North Main Range, followed 3 Ma behind the adjacent coastal progression. The Australian and Tasman Sea age-progressive chains are compared against recent plate motion modelling (Indian Ocean hotspots). The chain lines differ from general vector traces owing to west-facing swells and cessations in activity. Tectonic processes on the eastern plate margin may regulate these irregularities. These include subduction, rapid roll-back and progressive detachment of the Loyalty slab (43 to 15 Ma). West-flowing Pacific-type asthenosphere, related to perturbed mantle convection, may explain the west-facing volcanic surges. Such westward Pacific flow for over 28 Ma is known at the Australian–Antarctic Discordance, southeast of the present Australian plume sites under Bass Strait–West Tasman Sea. Most basaltic activity along eastern Australia marks asthenospheric melt injections into Tasman rift zone mantle and not lithospheric plate speed. The young (post-10 Ma) fields (Queensland, Victoria–South Australia) reflect new plate couplings, which altered mantle convection and stress regimes. These areas receive asthenospheric inputs from deep thermal zones off northeast Queensland and under Bass Strait.  相似文献   

Sapphire within zircon-rich gem deposits,Bo Loei,Ratanakiri Province,Cambodia: trace elements,inclusions, U–Pb dating and genesis     

F. L. Sutherland  P. C. Piilonen  Khin Zaw  S. Meffre  J. Thompson 《Australian Journal of Earth Sciences》2013,60(6):761-773

Subordinate sapphire accompanies prevalent zircon megacrysts in the Bo Loei basaltic gem field, Ratanakiri Province, Cambodia. These deposits are important for heat-treated gem zircon. Dark blue sapphire, with rare blue-green, orange-brown and yellow stones, up to a few cm in size, include hexagonal-shaped and growth-zoned crystals. Analyses of the sapphires (electron microprobe and laser ablation-inductively coupled plasma-mass spectrometry) showed Fe as the main chromophore (0.6–2.7 wt%), with minor Ti (<0.7 wt%). Sapphire cores show enrichment in Fe relative to rims and some include exotic heavy elements (Nb up to 56, Ta up to 144, Sn up to 5 ppm). The sapphires show high Ga values (271–724 ppm) and Ga/Mg ratios (4.8–77.0) suggesting magmatic associations. Two sapphires with syngenetic inclusions (zircon, Nb-rich rutile) gave U–Pb (Th-disequilibrium corrected) ages at ca 0.93 ± 0.1 Ma. The Bo Loei sapphires show higher Fe and Ga than other magmatic sapphire suites elsewhere in Cambodia (Pailin), Laos (Ban Huai Sai, Ban Sam Sai), South Vietnam (Dak Nong, Dak Lac) and SE Thailand (Chanthaburi-Trat). This suggests potential for geographic typing of sapphire suites between these different fields.  相似文献   

Effect of jet boats on salmon eggs     

A.J. Sutherland  D.G. Ogle 《新西兰海洋与淡水研究杂志》2013,47(3):273-282

The passage of jet boats through spawning areas can kill salmon eggs buried in the river bed. By using a jet boat on the Ashley River the pressure gradients created in a redd were determined. At the maximum boat speed investigated (11 m.s^‐1) gradients up to 9.32 kPa.m^‐1 were recorded. The induced water velocities through the gravel were then estimated from the equation of motion and reproduced in a gravel‐filled tube in the laboratory. For the test conditions discharge velocities ranged from 0.18–0.3 m.s‐¹. Studies of the effect of these flows on salmon eggs revealed fatality rates of up to 40% at their most critical stage on the ninth day of development.  相似文献   

Late Silurian (Ludlow–Přídolí) microfossils and sedimentation in the Welsh Basin near Clun,Shropshire     

C. Giles Miller  Stuart J. E. Sutherland  Ken J. Dorning 《Geological Journal》1997,32(1):69-83

The base of the Clun Forest Formation at Clun, Shropshire, has previously been taken to correlate with the base of the Downton Castle Sandstone Formation (Přídolí Series, upper Silurian) on the basis of brachiopod, bivalve, gastropod and ostracod faunas. The detailed distribution of microfossils (acritarchs, chitinozoans, conodonts and ostracods) is documented at Nantyrhynau Quarry, Clun, Shropshire, to test this correlation. Three new species of chitinozoans, Eisenackitina clunensis, Eisenackitina kerria and Angochitina paucispinosa, are described from the quarry. Macrofossil and ostracod distributions suggest that the correlation is correct. However, a typical Ludlow acritarch flora is present throughout the section and suggests that the basal part of the Clun Forest Formation is Ludlow in age. The mixture of characteristic Ludlow and Přídolí microfossils at Nantyrhynau Quarry may be the result of differing environmental conditions between the Ludlow (shelf) and Clun (basinal) areas at this time. Alternatively, the strata exposed at Nantyrhynau Quarry may represent a period towards the end of the Ludlow Series when there are no strata represented in corresponding shelf sections due to non-deposition or erosion. © 1997 John Wiley & Sons, Ltd.  相似文献   

The 2dF Galaxy Redshift Survey: Wiener reconstruction of the cosmic web     

Pirin Erdo&#;du  Ofer Lahav  Saleem Zaroubi  George Efstathiou  Steve Moody  John A. Peacock  Matthew Colless  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Chris Collins  Warrick Couch  Gavin Dalton  Roberto De Propris  Simon P. Driver  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole Jackson  Ian Lewis  Stuart Lumsden  Steve Maddox  Darren Madgwick  Peder Norberg  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2004,352(3):939-960

  相似文献   

One-photon and two-photon annihilation of positronium in strong magnetic fields     

Simon Carr  Peter Sutherland 《Astrophysics and Space Science》1978,58(1):83-88

In the presence of a strong magnetic field (such as those believed to be characteristic of neutron stars:B-10¹² Gauss) positronium may annihilate through the emission of a single photon, the magnetic field providing the photon momentum. We report on calculations of the one-photon and two-photon annihilation rates for the ground state of positronium, for magnetic fields in the range (1–44)×10¹² Gauss, and give, in the two-photon case, the minimum energy half-width of the emission line due to the momentum contributions from the magnetic field. We find that unless neutron stars have magnetic fields in excess of 10¹³ Gauss, it is unlikely that the one-photon process will be observable.Research supported in part by the National Research Council of Canada.  相似文献   

Collaborative geomatics and the Mushkegowuk Cree First Nations: Fostering adaptive capacity for community-based sub-arctic natural resource management     

Daniel D.P. McCarthy  Graham S. Whitelaw  Scott Anderson  Donald Cowan  Fred McGarry  Anthony Robins  Holly L. Gardner  Christine D. Barbeau  Nadia A. Charania  Zachariah General  Jeff Liedtke  Celine Sutherland  Paulo Alencar  Leonard J.S. Tsuji 《Geoforum》2012,43(2):305-314

The remote First Nation (FN) communities of the Mushkegowuk Territory on the west coast of James Bay, Ontario, Canada are currently facing increased development pressures and the imposition of a government land use planning process. The land use planning process is mandated in the Far North Act (received Royal Assent on September 23, 2010). There is a need for capacity enhancement for community-based natural resource planning and management in the Territory. A number of frameworks are emerging for addressing change brought on by resource development and building resilience to such change at the community level. Among these include the concept of adaptive capacity. In collaboration with FN community leaders, we explored the use of “collaborative geomatics” tools to foster adaptive capacity. Our action research suggests that collaborative geomatics technologies should enhance the Mushkegowuk First Nations’ adaptive capacity to address environmental and policy change by allowing them to collect and manage data collaboratively (e.g., traditional environmental knowledge, western science) to create opportunities for innovative community development, including natural resource development and management.  相似文献   

Re-ionizing the universe without stars     

Michael A. Dopita  Lawrence M. Krauss  Ralph S. Sutherland  Chiaki Kobayashi  Charles H. Lineweaver 《Astrophysics and Space Science》2011,335(2):345-352

Recent observations show that the measured rates of star formation in the early universe are insufficient to produce re-ionization, and therefore, another source of ionizing photons is required. In this Letter, we examine the possibility that these can be supplied by the fast accretion shocks formed around the cores of the most massive haloes (10.5<log M/M _⊙<12) on spatial scales of order 1 kpc. We model the detailed physics of these fast accretion shocks, and apply these to a simple 1-D spherical hydrodynamic accretion model for baryonic infall in dark matter halos with an Einasto density distribution. The escape of UV photons from these halos is delayed by the time taken to reach the critical accretion shock velocity for escape of UV photons; 220 km s⁻¹, and by the time it takes for these photons to ionize the surrounding baryonic matter in the accretion flow. Assuming that in the universe at large the baryonic matter tracks the dark matter, we can estimate the epoch of re-ionization in the case that accretion shocks act alone as the source of UV photons. We find that 50% of the volume (and 5-8% of the mass) of the universe can be ionized by z∼7–8. The UV production rate has an uncertainty of a factor of about 5 due to uncertainties in the cosmological parameters controlling the development of large scale structure. Because our mechanism is a steeply rising function of decreasing redshift, this uncertainty translates to a re-ionization redshift uncertainty of less than ±0.5. We also find that, even without including the UV photon production of stars, re-ionization is essentially complete by z∼5.8. Thus, fast accretion shocks can provide an important additional source of ionizing photons in the early universe.  相似文献   

东喜马拉雅构造结南迦巴瓦群高压麻粒岩中含石榴石花岗岩脉锆石SHRIMP U-Pb定年及其与折返作用   总被引：13，自引：10，他引：3  

戚学祥  李化启  李天福  蔡志慧  于春林 《岩石学报》2010,26(3):975-984

东喜马拉雅构造结核部的南迦巴瓦群是经历了高压麻粒岩相峰期变质、角闪岩相退变质和强烈混合岩化作用形成的以含有高压麻粒岩透镜体或夹层为特色的变质岩组合。地质地球化学研究表明产于退变质高压麻粒岩中的含石榴石花岗岩脉具有高钾、富铝、轻稀土强烈富集、分馏程度很高、重稀土相对亏损、Eu强烈亏损、大离子亲石元素及放射性元素相对原始地幔值强烈富集、Rb/Sr1.4的特征。利用花岗岩的主要成分及锆的含量估算的岩浆初始温度为792～801℃,略低于南迦巴瓦群的峰期变质温度850℃。锆石SHRIMPU-Pb定年结果显示锆石核部年龄集中在519～525Ma之间,揭示出印度地块经历泛非期构造运动改造的痕迹。锆石边部主要存在39～44Ma、24～25Ma和7.3Ma三个年龄段,前者代表了花岗岩浆的侵位时代,第二个年龄段是对MCT和STDS构造热事件改造的反映,后者揭示出构造-浅表反馈作用的信息。说明含石榴石花岗岩脉是在南迦巴瓦群折返过程中近等温降压条件下地壳岩石发生"干"深熔作用形成的高钾过铝质钙碱性花岗岩,以及南迦巴瓦群在经历峰期变质作用后很快就开始折返,并在后碰撞过程中经历了藏南拆离系(STDS)和主中央冲断带(MCT)构造事件及后期构造-浅表反馈作用的影响。  相似文献   

The 2dF Galaxy Redshift Survey: correlation with the ROSAT-ESO flux-limited X-ray galaxy cluster survey     

Matt Hilton  Chris Collins  Roberto De Propris  Ivan K. Baldry  Carlton M. Baugh  Joss Bland-Hawthorn  Terry Bridges  Russell Cannon  Shaun Cole  Matthew Colless  Warrick J. Couch  Gavin B. Dalton  Simon P. Driver  George Efstathiou  Richard S. Ellis  Carlos S. Frenk  Karl Glazebrook  Carole A. Jackson  Ofer Lahav  Ian Lewis  Stuart Lumsden  Steve J. Maddox  Darren Madgwick  Peder Norberg  John A. Peacock  Bruce A. Peterson  Will Sutherland  Keith Taylor 《Monthly notices of the Royal Astronomical Society》2005,363(2):661-674

  相似文献