Planetary nebula distances re-examined: an improved statistical scale     

J. P. Phillips 《Monthly notices of the Royal Astronomical Society》2004,353(2):589-600

  相似文献   

Correction to: Quantifying and understanding carbon storage and sequestration within the Eastern Arc Mountains of Tanzania,a tropical biodiversity hotspot     

Simon Willcock  Oliver L. Phillips  Philip J. Platts  Andrew Balmford  Neil D. Burgess  Jon C. Lovett  Antje Ahrends  Julian Bayliss  Nike Doggart  Kathryn Doody  Eibleis Fanning  Jonathan M. H. Green  Jaclyn Hall  Kim L. Howell  Rob Marchant  Andrew R. Marshall  Boniface Mbilinyi  Pantaleon K. T. Munishi  Nisha Owen  Ruth D. Swetnam  Elmer J. Topp-Jorgensen  Simon L. Lewis 《Carbon balance and management》2017,12(1):20

  相似文献   

湘西沃溪金矿床矿石矿物学特征及深部找矿意义   总被引：4，自引：1，他引：3  

彭 渤 刘升友 Piestrzynski Adam Jadwiga Pieczonka唐晓燕  余昌训谢淑容 《中国地质》2008,35(6):1286-1290

借助电子探针分析技术,对沃溪矿床V3矿脉深部(29中段)矿体进行了矿石矿物学观察和分析,发现深部矿体自然金中Ag、Sb、Pb、Bi等杂质元素的含量明显比浅部(24中段以上)自然金相应组分的含量偏高,深部自然金的成色(≤995)比浅部自然金的成色(≥999)明显偏低;深部矿体矿石中发育辉锑矿、黄铁矿、闪锌矿、黄铜矿、黝铜矿、硫锑矿、车轮矿等矿物,形成明显比浅部矿体组成复杂的矿物组合,显示矿床深部发育Au-Pb-zn-Bi±Cu的矿化作用.上述表明:沃溪矿床深部可能发育具Au-Pb-zn-Bi±Cu等元素组合的新矿体.它不同于浅部的W-Sb-Au元素组合的特征.因而深部找矿工作应多注重Au-Pb-zn-Bi+Cu多元素矿床.  相似文献   

The partitioning behavior of silver in a vapor-brine-rhyolite melt assemblage     

Adam C. Simon  Thomas Pettke  Philip M. Piccoli 《Geochimica et cosmochimica acta》2008,72(6):1638-1659

The partitioning of silver in a sulfur-free rhyolite melt-vapor-brine assemblage has been quantified at 800 °C, pressures of 100 and 140 MPa and f_O2≈NNO (nickel-nickel oxide). Silver solubility (±2σ) in rhyolite increases 5-fold from 105 ± 21 to 675 ± 98 μg/g as pressure increases from 100 to 140 MPa. Nernst-type partition coefficients describing the mass transfer of silver at 100 MPa between vapor and melt, brine and melt and vapor and brine are 32 ± 30, 1151 ± 238 and 0.026 ± 0.004, respectively. At 140 MPa, values for for vapor and melt, brine and melt, and vapor and brine are 32 ± 10, 413 ± 172 and 0.06 ± 0.03, respectively. Apparent equilibrium constant values (±2σ) describing the exchange of silver and sodium between vapor and melt, , at 100 and 140 MPa are 105 ± 68 and 14 ± 6. The average values (±2σ) for silver and sodium exchange between brine and melt, , at 100 and 140 MPa are 313 ± 288 and 65 ± 12. These data indicate that the mass transfer of silver from rhyolite melt to an exsolved volatile phase(s) is enhanced at 100 MPa relative to 140 MPa, suggesting that decompression increases the silver ore-generative potential of an evolving silicate magma. Model calculations using the new data suggest that the evolution of low-density, aqueous fluid (i.e., vapor) may be responsible for the the silver tonnage of many porphyry-type and perhaps epithermal-type ore deposits. For example, Halter et al. (Halter W. E., Pettke T. and Heinrich C. A. (2002) The origin of Cu/Au ratios in porphyry-type ore deposits. Science296, 1842-1844) used detailed silicate and sulfide melt inclusion and vapor and brine fluid inclusions analyses to estimate a melt volume on the order of 15 km³ to satisfy the copper budget at the Bajo de la Alumbrera copper-, gold-, silver-ore deposit. Using their melt volume estimate with the data presented here, model calculations for a 15-km³ felsic melt, saturated with pyrrhotite and magnetite, suggest that a low-salinity magmatic vapor may scavenge on the order of 7 × 10¹² g of silver from the melt. This quantity of silver exceeds the discovered 2 × 10⁹ g of Ag at Alumbrera. Calculated tonnages for numerous other deposits yield similar results. The excess silver in the vapor, remaining after porphyry formation, is then available to precipitate at lower PTconditions in the stratigraphically higher epithermal environment. These data suggest that silver, and perhaps other ore metals, in the porphyry-epithermal continuum may be derived solely from the time-integrated flux of dominantly low-salinity vapor exsolved from a series of sequential magma batches.  相似文献   

A new 40Ar/39Ar eruption age for the Mount Widderin volcano,Newer Volcanic Province,Australia, with implications for eruption frequency in the region     

E. L. Matchan  E. B. Joyce  D. Phillips 《Australian Journal of Earth Sciences》2016,63(2):175-186

The Mount Widderin shield volcano is located near Skipton, western Victoria, in the Western Plains subprovince of the monogenetic Pliocene–Holocene Newer Volcanic Province (NVP). Radiometric ages for lavas in the Hamilton–Skipton–Derrinallum area are few, owing to limited suitable outcrop for K–Ar or ⁴⁰Ar/³⁹Ar geochronology studies. Existing age constraints for flows in this area have been inferred from Regolith Landform Units (RLUs), complemented by a small number of K–Ar studies on ≥1 Ma flows. Although the RLU approach provides a valuable overview of relative eruption ages across the NVP, it is of limited use in eruption frequency studies. Additional radio-isotopic ages are required to refine age ranges for individual RLUs, and to validate previous assignment of individual flows to specific RLUs. We report a new, high-precision ⁴⁰Ar/³⁹Ar age of 389 ± 8 ka (2σ) for a Mount Widderin basalt sample. Based on this age and geomorphic observations, we propose that both the Widderin and Elephant lava flows be reassigned from the Eccles RLU to the Rouse RLU. We use the 389 ± 8 ka (2σ) age for Widderin, along with published K–Ar ages, to anchor a stratigraphic sequence of 15 individual flows in the Hamilton–Skipton–Derrinallum area, demonstrating that intermittent volcanism has occurred in this area from ≥3 Ma to ≤0.389 Ma. Within the limits of available data for the NVP, this time span of volcanic activity is second only to that of the Melbourne area. We consider the significance of the Widderin eruption age, in conjunction with published age constraints for maars and scoria cones of the Western Plains subprovince, building on previous studies that have focused solely on lava flow ages. The inclusion of the additional data weakens the argument for a decrease in volcanic activity after ca 0.9 Ma as implied by published ages for lava flows only. Additional detailed combined geochronology–geomorphology studies of lavas, scoria cones and maars in strategically selected small areas are advocated to better understand eruption frequency across the NVP.  相似文献   

The distributional and nutritional impacts and mitigation potential of emission-based food taxes in the UK     

Ariane Kehlbacher  Richard Tiffin  Adam Briggs  Mike Berners-Lee  Peter Scarborough 《Climatic change》2016,137(1-2):121-141

  相似文献   

Anomalously heavy monthly and seasonal precipitation in the Polish Carpathian Mountains and their foreland during the years 1881–2010     

Robert Twardosz  Marta Cebulska  Adam Walanus 《Theoretical and Applied Climatology》2016,126(1-2):323-337

  相似文献   

What caused the spring intensification and winter demise of the 2011 drought over Texas?     

D. Nelun Fernando  Kingtse C. Mo  Rong Fu  Bing Pu  Adam Bowerman  Bridget R. Scanlon  Ruben S. Solis  Lei Yin  Robert E. Mace  John R. Mioduszewski  Tong Ren  Kai Zhang 《Climate Dynamics》2016,47(9-10):3077-3090

  相似文献   

Tracking the long-term responses of diatoms and cladocerans to climate warming and human influences across lakes of the Ring of Fire in the Far North of Ontario,Canada     

Kathryn E. Hargan  Clare Nelligan  Adam Jeziorski  Kathleen M. Rühland  Andrew M. Paterson  Wendel Keller  John P. Smol 《Journal of Paleolimnology》2016,56(2-3):153-172

  相似文献   

The influence of the wind direction and plants on the variability of topsoil magnetic susceptibility in industrial and urban areas of southern Poland     

Tadeusz Magiera  Henryk Parzentny  Adam Łukasik 《Environmental Earth Sciences》2016,75(3):213

  相似文献