Authors:Grasby et alAbstract:Sedimentary records from the northwest margin of Pangea and the Tethys show anomalously high Hg levels at the latest Permian extinction boundary. Background δ202Hg values are consistent with normal marine conditions but exhibit negative shifts coincident with increased Hg concentrations. Hg isotope mass-independent fractionation (Δ199Hg) trends are consistent with volcanic input in deep-water marine environments. In contrast, nearshore environments have Δ199Hg signatures consistent with enhanced soil and/or biomass input. We hypothesize that the deep-water signature represents an overall global increase in volcanic Hg input and that this isotope signature is overwhelmed in nearshore locations due to Hg from terrestrial sources. High-productivity nearshore regions may have experienced stressed marine ecosystems due to enhanced Hg loading.
Showing posts with label mercury. Show all posts
Showing posts with label mercury. Show all posts
Friday, November 18, 2016
Evidence of Extensive Mercury Pollution During Permian Triassic Mass Extinction
Thursday, August 18, 2016
Did Mercury's Volcanic Activity End 3.5 Billion Years ago?
New research from North Carolina State University finds that major volcanic activity on the planet Mercury most likely ended about 3.5 billion years ago. These findings add insight into the geological evolution of Mercury in particular, and what happens when rocky planets cool and contract in general.
There are two types of volcanic activity: effusive and explosive. Explosive volcanism is often a violent event that results in large ash and debris eruptions, such as the Mount Saint Helens eruption in 1980. Effusive volcanism refers to widespread lava flows that slowly pour out over the landscape -- believed to be a key process by which planets form their crusts.
Determining the ages of effusive volcanic deposits can give researchers a handle on a planet's geological history. For example, effusive volcanism was active a few hundred million years ago on Venus, a few million years ago on Mars, and it still takes place on Earth today. Until now, the duration of effusive volcanic activity on Mercury, made of the same materials as these other planets, had not been known.
NC State assistant professor and planetary geologist Paul Byrne and colleagues determined when the bulk of Mercury's crust-forming volcanism ended by using photographs of the surface imaged by NASA's MESSENGER mission. Because there are no physical samples from the planet that could be used for radiometric dating, the researchers used crater size-frequency analysis, in which the number and size of craters on the planet's surface are placed into established mathematical models, to calculate absolute ages for effusive volcanic deposits on Mercury.
According to their results, major volcanism on Mercury stopped at around 3.5 billion years ago, in stark contrast to the volcanic ages found for Venus, Mars and Earth.
link.
Thursday, July 28, 2016
Were Major Impacts on Moon, Mercury & Mars Caused by Protoplanets?
Around 3.8 billion years ago, an asteroid more than 150 miles across, roughly equal to the length of New Jersey, slammed into the Moon and created the Imbrium Basin -- the right eye of the fabled Man in the Moon. This new size estimate, published in the journal Nature, suggests an Imbrium impactor that was two times larger in diameter and 10 times more massive than previous estimates.
"We show that Imbrium was likely formed by an absolutely enormous object, large enough to be classified as a protoplanet," said Pete Schultz, professor of earth, environmental and planetary sciences at Brown University. "This is the first estimate for the Imbrium impactor's size that is based largely on the geological features we see on the Moon."
Previous estimates, Schultz said, were based solely on computer models and yielded a size estimate of only about 50 miles in diameter.
These new findings help to explain some of the puzzling geological features that surround the Imbrium Basin. The work also suggests -- based on the sizes of other impact basins in the Moon, Mars and Mercury -- that the early solar system was likely well stocked with protoplanet-sized asteroids.
link.
Wednesday, June 22, 2016
Mercury Increased in Three Different Spikes From Deccan Traps Across the K-T/K-Pg Boundary
Mercury enrichment and Hg isotopes in Cretaceous–Paleogene boundary successions: Links to volcanism and palaeoenvironmental impacts
Authors:
Sial et al
Abstract:
We investigate the use of Hg as a proxy for volcanism by studying four distal and two proximal sections in relation to the Deccan volcanic center, straddling the Cretaceous–Paleogene (KPg) boundary at (a) Højerup (Denmark), Bottaccione and Padriciano (Italy), (b) Meghalaya and Jhilmili (India), and (c) Bajada del Jagüel (Argentina). Hg sequestration by organic matter results in constant Hg/TOC ratio and linear correlation between Hg content of the sediments and total organic carbon (TOC).
Elevated Hg concentrations that deviate from this linear relationship represent most likely true Hg anomalies and these notable Hg/TOC spikes (all TOC <1 al="" also="" and="" are="" at="" between="" biozone="" bottaccione="" boundary="" cf2="" clear="" correlation="" foraminiferal="" found="" h="" hg="" i="" ii="" iii="" in="" jerup="" jhilmili="" kpg="" meghalaya="" no="" occurs="" p1a="" planktic="" section.="" sections="" spike="" sub="" subzone="" the="" within="">2
<1 250="" 750="" a="" aerosols="" agents="" al2o3="" also="" and="" anomalies="" anoxia="" any="" are="" at="" before="" between="" biozone="" bottaccione="" boundary="" br="" carbon="" cf2="" clear="" correlation="" critical="" deccan="" dioxide="" downward="" enrichments="" episodes="" exhaled="" exists="" for="" foraminiferal="" found="" from="" h="" hg="" i="" ii="" iii="" in="" into="" is="" jerup="" jhilmili="" kpg="" kyr="" l="" lasted="" meghalaya="" mo="" no="" not="" occurs="" of="" on="" other="" p1a="" paleoenvironments.="" penetration="" phase-2="" planktic="" possibility="" probably="" proxy.="" ratios="" reached="" record="" redox="" represented="" result="" resulted="" scavenging="" seafloor="" section.="" sections.="" sections="" sediments="" spike="" started="" stratigraphic="" strong="" studied="" subzone="" sulfuric="" supported="" that="" the="" threshold="" toxic="" true="" volcanic="" which="" within=""> Hg isotopes were analyzed in samples from all KPg boundary sections in this study and from Bidart, France, the latter for comparison. Hg isotopes yielded δ202Hg values ranging from −1 to −2‰ and Δ201Hg signatures from 0 to 0.05‰ (spike II in Højerup, Bottaccione and Meghalaya KPg boundary layers) consistent with volcanic emission of Hg (0 to −2‰). The δ202Hg in spike I in Meghalaya and Padriciano and spike III in Jhilmili is consistent with volcanic emission of Hg. Two samples from Bajada del Jagüel and four from Bidart, however, display isotope signals compatible with volcanic emission/chondrite Hg. The results of three other samples are characteristic for reworked sediment, soil and/or peat. Most of the data show small positive Δ201Hg, in favor of long-term atmospheric transport prior to deposition, supporting a volcanic origin for the Hg. The present study broadens, therefore, the potential use of Hg as stratigraphic marker and, moreover, confirms that in the critical KPg transition, Hg was enriched in paleoenvironments at three distinct stages during the Deccan phase-2.
<1 250="" 750="" a="" aerosols="" agents="" al2o3="" also="" and="" anomalies="" anoxia="" any="" are="" at="" before="" between="" biozone="" bottaccione="" boundary="" br="" carbon="" cf2="" clear="" correlation="" critical="" deccan="" dioxide="" downward="" enrichments="" episodes="" exhaled="" exists="" for="" foraminiferal="" found="" from="" h="" hg="" i="" ii="" iii="" in="" into="" is="" jerup="" jhilmili="" kpg="" kyr="" l="" lasted="" meghalaya="" mo="" no="" not="" occurs="" of="" on="" other="" p1a="" paleoenvironments.="" penetration="" phase-2="" planktic="" possibility="" probably="" proxy.="" ratios="" reached="" record="" redox="" represented="" result="" resulted="" scavenging="" seafloor="" section.="" sections.="" sections="" sediments="" spike="" started="" stratigraphic="" strong="" studied="" subzone="" sulfuric="" supported="" that="" the="" threshold="" toxic="" true="" volcanic="" which="" within="">
<1 250="" 750="" a="" aerosols="" agents="" al2o3="" also="" and="" anomalies="" anoxia="" any="" are="" at="" before="" between="" biozone="" bottaccione="" boundary="" br="" carbon="" cf2="" clear="" correlation="" critical="" deccan="" dioxide="" downward="" enrichments="" episodes="" exhaled="" exists="" for="" foraminiferal="" found="" from="" h="" hg="" i="" ii="" iii="" in="" into="" is="" jerup="" jhilmili="" kpg="" kyr="" l="" lasted="" meghalaya="" mo="" no="" not="" occurs="" of="" on="" other="" p1a="" paleoenvironments.="" penetration="" phase-2="" planktic="" possibility="" probably="" proxy.="" ratios="" reached="" record="" redox="" represented="" result="" resulted="" scavenging="" seafloor="" section.="" sections.="" sections="" sediments="" spike="" started="" stratigraphic="" strong="" studied="" subzone="" sulfuric="" supported="" that="" the="" threshold="" toxic="" true="" volcanic="" which="" within="">
Thursday, July 30, 2015
Mercury Anomalies Associated With Three Mass Extinction Events
Mercury anomalies associated with three extinction events (Capitanian Crisis, Latest Permian Extinction and the Smithian/Spathian Extinction) in NW Pangea
Authors:
Grasby et al
Abstract:
Strata of Permian – Early Triassic age that include a record of three major extinction events (Capitanian Crisis, Latest Permian Extinction and the Smithian/Spathian Extinction) were examined at the Festningen section, Spitsbergen. Over the c. 12 Ma record examined, mercury in the sediments shows relatively constant background values of 0.005–0.010 μg g–1. However, there are notable spikes in Hg concentration over an order of magnitude above background associated with the three extinctions. The Hg/total organic carbon (TOC) ratio shows similar large spikes, indicating that they represent a true increase in Hg loading to the environment. We argue that these represent Hg loading events associated with enhanced Hg emissions from large igneous province (LIP) events that are synchronous with the extinctions. The Hg anomalies are consistent across the NW margin of Pangea, indicating that widespread mercury loading occurred. While this provides utility as a chemostratigraphic marker the Hg spikes may also indicate loading of toxic metals to the environment, a contributing cause to the mass extinction events.
Monday, July 14, 2014
Is Mercury a Failed SuperEarth?
Planet Mercury's unusual metal-rich composition has been a longstanding puzzle in planetary science. According to a study published online in Nature Geoscience July 6, Mercury and other unusually metal-rich objects in the solar system may be relics left behind by collisions in the early solar system that built the other planets.
The origin of planet Mercury has been a difficult question in planetary science because its composition is very different from that of the other terrestrial planets and the moon. This small, innermost planet has more than twice the fraction of metallic iron of any other terrestrial planet. Its iron core makes up about 65 percent of Mercury's total mass; Earth's core, by comparison, is just 32 percent of its mass.
How do we get Venus, Earth and Mars to be mostly "chondritic" (having a more-or-less Earth-like bulk composition) while Mercury is such an anomaly? For Arizona State University professor Erik Asphaug, understanding how such a planet accumulated from the dust, ice and gas in the early solar nebula is a key science question.
There have been a number of failed hypotheses for Mercury's formation. None of them until now has been able to explain how Mercury lost its mantle while retaining significant levels of volatiles (easily vaporized elements or compounds, such as water, lead and sulfur). Mercury has substantially more volatiles than the moon does, leading scientists to think its formation could have had nothing to do with a giant impact ripping off the mantle, which has been a common popular explanation.
To explain the mystery of Mercury's metal-rich composition, ASU's Asphaug and Andreas Reufer of the University of Bern have developed a new hypothesis involving hit-and-run collisions, where proto-Mercury loses half its mantle in a grazing blow into a larger planet (proto-Venus or proto-Earth). One or more hit-and-run collisions could have potentially stripped away proto-Mercury's mantle without an intense shock, leaving behind a mostly-iron body and satisfying a number of the major puzzles of planetary formation – including the retention of volatiles – in a process that can also explain the absence of shock features in many of the mantle-stripped meteorites.
Asphaug and Reufer have developed a statistical scenario for how planets merge and grow based on the common notion that Mars and Mercury are the last two relics of an original population of maybe 20 bodies that mostly accreted to form Venus and Earth. These last two planets lucked out.
"How did they luck out? Mars, by missing out on most of the action – not colliding into any larger body since its formation – and Mercury, by hitting the larger planets in a glancing blow each time, failing to accrete," explains Asphaug, who is a professor in ASU's School of Earth and Space Exploration. "It's like landing heads two or three times in a row – lucky, but not crazy lucky. In fact, about one in 10 lucky."
link.
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