Several types of dolomitization are observed in the Lower Cretaceous carbonate sequence of the Tappehsorkh deposit, Irankuh Mining District, Iran: 1) regional and extensive early diagenetic dolomitization (D1), and 2) localized hydrothermal dolomitization (D2 and D3). D1 regional dolomite, which partly to completely replace limestone, is characterized by fine‐grained euhedral to subhedral dolomite rhombs. There is no evidence for Zn‐Pb sulphide mineralization associated with this type of dolomite. Medium to coarse‐grained D2 and D3 hydrothermal dolomites occur along the syn‐sedimentary Gushfil‐Baghabrisham normal fault, about 40 m above the Lower Cretaceous sequence within black siltstone, dolostone, and crystal lithic tuff and lava rocks. Hydrothermal dolomite cross‐cuts and brecciates the host rocks. This dolomite was replaced by quartz and sulphide minerals of the main ore stage. D1 regional dolomite has average values of ‐7.37‰ and 2.20‰ for δ18O and δ13C, respectively. The δ13C values of this dolomite fall well within the range of the Lower Cretaceous carbonates. D2 hydrothermal dolomite has average δ18O and δ13C values of ‐7.92‰ and 2.93‰, respectively. The respective δ18O and δ13C values of D3 hydrothermal dolomite are ‐12.27‰ and 2.39‰. The δ18O values of D2 and D3 dolomites are more negative than those of D1 regional dolomite; this can be due to their hydrothermal origin. Fluid inclusion studies on D3 dolomite and quartz show temperatures of 170‐260 °C. The concentrations of Fe and Mn in D1 regional dolomite are very similar to those of limestone, suggesting that they likely precipitated from the same fluid (seawater), whereas those of D2 and D3 dolomites are relatively high, in agreement with the hydrothermal origin for these dolomites. Precipitation of gypsum, which is ubiquitous in the study area, could have lowered the Ca/Mg ratio of seawater. While the extensive regional dolomitization formed from low‐temperature (evolved) seawater during the early diagenesis, D2 and D3 dolomites associated with the main stage of sulphide mineralization were formed by high‐temperature hydrothermal fluids moving along the Gushfil‐Baghabrisham Fault. Copyright © 2016 John Wiley & Sons, Ltd.Read more
The widely developed black shales on the Yangtze Platform recorded palaeoceanographic environment information during the Ediacaran–Cambrian transition. This paper describes an integrated geochemical study of rare earth elements (REEs), redox‐sensitive trace elements (RSTEs), and total organic carbon (TOC) contents in Ediacaran–Cambrian black shales at Daotuo, northeastern Guizhou Province, South China. Integrated RSTE data from the Daotuo area, in combination with previously published Fe speciation and Mo‐based proxies from another six sections (Shatan, Jiulongwan, Zhongling, Yangjiaping, Longbizui and Wuhe), suggest three major periods of water euxinia during the Ediacaran–Cambrian transition. Under these conditions, organic matter and RSTEs experienced various levels of enrichment in the black shales, especially in the lower Jiumenchong Formation. Given the patterns of Mo‐U covariations, metal‐oxyhydroxide particulate shuttles may have operated during the black shale deposition of the Doushantuo Formation (Member II) at Daotuo. Conspicuously, the upper slope water was oxic‐dysoxic during the earliest Cambrian, as determined by the REE, RSTE data and sedimentological characteristics of the Liuchapo Formation and the basal Jiumenchong Formation. The generally low RSTE concentrations in the Bianmachong Formation black shales (Cambrian Series 2, end of Stage 3) suggest a persistently oxic water column in upper slope settings. The coincidence between the marine oxygenation and the development of the ecosystem likely indicates the galvanizing effects of enhanced oxygen and biological element content on the fauna during the Ediacaran–Cambrian transition. Copyright © 2016 John Wiley & Sons, Ltd.Read more
Chemistry plays an important role in the interstellar medium (ISM), regulating heating and cooling of the gas, and determining abundances of molecular species that trace gas properties in observations….Read more
Many atmospheres (cool stars, brown dwarfs, giant planets, extrasolar planets) are predominately composed of molecular hydrogen and helium….Read more
Origin date/time: Sun, 30 Oct 16 13:39:25 GMT; Location: MARCHWIEL,WREXHAM ; Lat/long: 53.031,-2.939; Depth: 4km; Magnitude: 0.5Read more
Origin date/time: Sat, 29 Oct 16 19:20:51 GMT; Location: ; Lat/long: 59.936,2.33; Depth: 43km; Magnitude: 2.7Read more
Origin date/time: Sat, 29 Oct 16 02:02:35 GMT; Location: NEATH,NEATH PORT TALBOT ; Lat/long: 51.674,-3.718; Depth: 9km; Magnitude: 1Read more
Origin date/time: Sat, 29 Oct 16 01:43:53 GMT; Location: CULGAITH,CUMBRIA ; Lat/long: 54.673,-2.59; Depth: 4km; Magnitude: 0.3Read more
List of Reviewers No abstract is available for this article. Ancillary Article Information DOI 10.1002/gj.2887 View/save citation Format Available FullRead more
Origin date/time: Thu, 27 Oct 16 04:56:54 GMT; Location: LISKEARD,CORNWALL ; Lat/long: 50.516,-4.523; Depth: 8km; Magnitude: 0.2Read more
Origin date/time: Thu, 27 Oct 16 02:08:29 GMT; Location: LISKEARD,CORNWALL FELT CORNWALL.. ; Lat/long: 50.51,-4.532; Depth: 10km; Magnitude: 2.3Read more
A temporary cooling of the ocean around Antarctica’s fastest-melting glacier failed to stop its retreat into the sea.The Pine Island Glacier in West Antarctica is currently the largest glacial contributor to global sea-level rise. Knut Christianson at the University of Washington in Seattle andRead more
Genetic analysis of historical virus samples proves the epidemic arrived by another route.Read more
Europe’s largest land mammal may be a hybrid of two extinct species.Julien Soubrier and Alan Cooper at the University of Adelaide in Australia and their colleagues analysed mitochondrial DNA from 65 fossil specimens of bison, including the threatened European bison (Bison bonasus),Read more
Academia is more difficult than ever for young scientists. That’s bad for them, and bad for scienceRead more
A telescope located deep in the West Australian outback has shown what the Universe would look like if human eyes could see radio waves.
Published today in the Monthly Notices of the Royal Astronomical Society, the GaLactic and Extragalactic All-sky MWA, or ‘GLEAM’ survey, has produced a catalogue of 300,000 galaxies observed by the Murchison Widefield Array (MWA), a $50 million radio telescope located at a remote site north-east of Geraldton.
Lead author Dr Natasha Hurley-Walker, from Curtin University and the International Centre for Radio Astronomy Research (ICRAR), said this is the first radio survey to image the sky in such amazing technicolour. “The human eye sees by comparing brightness in three different primary colours – red, green and blue,” she said. “GLEAM does rather better than that, viewing the sky in each of 20 primary colours. That’s much better than we humans can manage, and it even beats the very best in the animal kingdom, the mantis shrimp, which can see 12 different primary colours.”
GLEAM is a large-scale, high-resolution survey of the radio sky observed at frequencies from 70 to 230 MHz, observing radio waves that have been travelling through space—some for billions of years. “Our team are using this survey to find out what happens when clusters of galaxies collide,” Dr Hurley-Walker said. “We’re also able to see the remnants of explosions from the most ancient stars in our galaxy, and find the first and last gasps of supermassive black holes.”
MWA director Dr Randall Wayth said GLEAM is one of the biggest radio surveys of the sky ever assembled. “The area surveyed is enormous,” he said. “Large sky surveys like this are extremely valuable to scientists and they’re used across many areas of astrophysics, often in ways the original researchers could never have imagined.”
Completing the GLEAM survey with the Murchison Widefield Array is a big step on the path to SKA-low, the low frequency part of the international Square Kilometre Array radio telescope to be built in Australia in the coming years. “It’s a significant achievement for the MWA telescope and the team of researchers that have worked on the GLEAM survey,” Dr Wayth said. “The survey gives us a glimpse of the Universe that SKA-low will be probing once it’s built. By mapping the sky in this way we can help fine-tune the design for the SKA and prepare for even deeper observations into the distant Universe.”
Tel: +61 423 982 018
Dr Robert Massey
Royal Astronomical Society
Tel: +44 (0)20 7734 3307
Dr Natasha Hurley-Walker
Curtin University, ICRAR
Tel: +61 426 192 677
Dr Randall Wayth
Curtin University, ICRAR, CAASTRO
Tel: +61 418 282 359
Images and Captions
A ‘radio colour’ view of the sky above a ’tile’ of the Murchison Widefield Array radio telescope, located in outback Western Australia. The Milky Way is visible as a band across the sky and the dots beyond are some of the 300,000 galaxies observed by the telescope for the GLEAM survey. Red indicates the lowest frequencies, green the middle frequencies and blue the highest frequencies. Credit: Radio image by Natasha Hurley-Walker (ICRAR/Curtin) and the GLEAM Team. MWA tile and landscape by Dr John Goldsmith/Celestial Visions.
The GLEAM view of the centre of the Milky Way, in radio colour. Red indicates the lowest frequencies, green the middle frequencies and blue the highest frequencies. Each dot is a galaxy, with around 300,000 radio galaxies observed as part of the GLEAM survey. Credit: Natasha Hurley-Walker (ICRAR/Curtin) and the GLEAM Team.
High-resolution videos and images are available from www.icrar.org/GLEAM
Original publication, ‘GaLactic and Extragalactic All-sky Murchison Widefield Array (GLEAM) survey I: A low-frequency extragalactic catalogue’, published in the Monthly Notices of the Royal Astronomical Society onOctober 27th, 2016. Available from http://s3-ap-southeast-2.amazonaws.com/icrar.org/wp-content/uploads/2016/10/18223055/GLEAM-Paper_sml.pdf
Notes for editors
The Murchison Widefield Array (MWA) is a low frequency radio telescope located at the Murchison Radio-astronomy Observatory in Western Australia’s Mid West. The MWA observes radio waves with frequencies between 70 and 320 MHz and was the first of the three Square Kilometre Array (SKA) precursors to be completed. A consortium of 13 partner institutions from four countries (Australia, USA, India and New Zealand) has financed the development, construction, commissioning and operations of the facility. Since commencing operations in mid 2013 the consortium has grown to include new partners from Canada and Japan. Key science for the MWA ranges from the search for redshifted HI signals from the Epoch of Reionisation to wide-field searches for transient and variable objects (including pulsars and Fast Radio Bursts), wide-field Galactic and extra-galactic surveys, and solar and heliospheric science.
The Square Kilometre Array (SKA) project is an international effort to build the world’s largest radio telescope, led by SKA Organisation based at the Jodrell Bank Observatory near Manchester. Co-located primarily in South Africa and Western Australia, the SKA will be a collection of hundreds of thousands of radio antennas with a combined collecting area equivalent to approximately one million square metres, or one square kilometre. The SKA will conduct transformational science to improve our understanding of the Universe and the laws of fundamental physics, monitoring the sky in unprecedented detail and mapping it hundreds of times faster than any current facility.
The International Centre for Radio Astronomy Research (ICRAR) is a joint venture between Curtin University and The University of Western Australia with support and funding from the State Government of Western Australia.
The Royal Astronomical Society (RAS,www.ras.org.uk), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. The RAS organizes scientific meetings, publishes international research and review journals, recognizes outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.
The RAS accepts papers for its journals based on the principle of peer review, in which fellow experts on the editorial boards accept the paper as worth considering. The Society issues press releases based on a similar principle, but the organisations and scientists concerned have overall responsibility for their content.Read more
Breakthrough Listen, which was created last year with $100 million in funding over 10 years from the Breakthrough Prize Foundation and its founder, internet investor Yuri Milner, won’t be the first to search for intelligent life around this star….Read more
Origin date/time: Tue, 25 Oct 16 20:53:49 GMT; Location: ISLAY,ARGYLL AND BUTE ; Lat/long: 55.649,-6.171; Depth: 9km; Magnitude: 0.6Read more
A new study finds movement of North Anatolian fault may provide clues to future earthquakes.Read more
Distant wastewater disposal wells likely induced the third largest earthquake in recent Oklahoma record, the February 13, 2016, magnitude 5.1 event roughly 32 kilometers (nearly 20 miles) northwest of Fairview, Oklahoma, according to a new study.Read more
In the final days before the US election, political leaders must speak out to boost confidence in the democratic process, says Andrew Daniller.Read more
Failure of ExoMars lander will pave the way for the next mission.Read more
A Fourier transform analysis of 2.5 million spectra in the Sloan Digital Sky Survey was carried out to detect periodic spectral modulations. Signals having the same period were found in only 234 stars overwhelmingly in the F2 to K1 spectral…Read more