Simplified model for the tectonic evolution of the Taconic orogeny and closure of the Iapetus Ocean. Horizontal distances are not to scale.
When and where did the ancient Iapetus Ocean suture (the most fundamental Appalachian structure) form? Is part of New England made up of ancient African-derived rocks? What is the Moretown terrane? This new GEOLOGY study by researchers from Harvard, Middlebury College, Boise State University, and Williams College finds new evidence for an earlier closing of the Iapetus that is farther west than previous studies have reported.
Mountain-building events, called “orogenies,” in the northern U.S. Appalachia record the closure of the Iapetus Ocean, an ancient precursor to the Atlantic. The Iapetus separated continental fragments of ancestral North America and Africa more than 450 million years ago
The mountain-building period that affected most of modern-day New England, known as the “Taconic orogeny,” is commonly depicted as a collision during the Ordovician period (435 to 500 million years ago) of a North American-derived arc (the Shelburne Falls arc) and the North American margin, followed by accretion of African-derived terranes (groups of rocks with geologic histories different from surrounding rocks) during the Silurian period (410 to 435 million years ago).
New uranium-lead (U-Pb) zircon dating presented here by Harvard researcher Francis A. Macdonald and colleagues demonstrates instead that the Shelburne Falls arc was constructed on an African-derived terrane, which they have named the Moretown terrane. Their geochronologic data reveal that the main Iapetan suture, which marks the location of the Iapetus as it was consumed through subduction, is more than 50 km west than previously suspected.
Macdonald and colleagues conclude that the Moretown terrane lies below North American-derived volcanic and sedimentary rocks of the Hawley Formation, which proves a link between North American- and African-derived terranes. The Moretown terrane and Hawley Formation were both intruded by 475-million-year-old plutonic rocks (rocks formed by magma rising from great depths beneath Earth’s surface), suggesting that these terranes were together by this time and that the Iapetus Ocean closed approx. 20 million years earlier than documented elsewhere.
Note : The above story is based on materials provided by Geological Society of America, The.
Chemical Formula: MnWO4 Locality: Erie and Enterprise veins, Ellsworth (Mammoth) district, Nye County, Nevada, USA. Name Origin: After the German mineralogist, Adolph Huebner.
Hübnerite or hubnerite is a mineral consisting of manganese tungsten oxide (chemical formula: MnWO4, it isn’t a tungstate). It is the manganese endmember of the manganese – iron wolframite solid solution series. It forms reddish brown to black monoclinic prismatic submetallic crystals. The crystals are typically flattened and occur with fine striations. It has a high specific gravity of 7.15 and a Mohs hardness of 4.5. It is transparent to translucent with perfect cleavage. Refractive index values are nα=2.170 – 2.200, nβ=2.220, and nγ=2.300 – 2.320.
Typical occurrence is in association with high-temperature hydrothermal vein deposits and altered granites with greisen, granite pegmatites and in alluvial deposits. It occurs associated with cassiterite, arsenopyrite, molybdenite, tourmaline, topaz, rhodochrosite and fluorite.
It was first described in 1865 for an occurrence in the Erie and Enterprise veins, Mammoth district, Nye County, Nevada, and named after the German mining engineer and metallurgist, Adolf Huebner from Freiberg, Saxony
Physical Properties
Cleavage: {010} Perfect Color: Brown, Reddish brown, Brownish black. Density: 7.2 – 7.1, Average = 7.15 Diaphaneity: Transparent to Translucent Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 4.5 – Between Fluorite and Apatite Luster: Sub Metallic Streak: reddish brown
A team of scientists from the UK, the US, Australia and New Zealand have modelled the fate of a huge floating raft of volcanic rocks that formed in 2012 during a submarine eruption of a Pacific volcano.
Described in this month’s edition of Nature Communications, they show how satellite images of the floating-rock raft’s passage across the Pacific can be used to test models of ocean circulation. Their results could be used to forecast the dispersal of future pumice (volcanic rock) islands, and protect shipping from the hazards they pose.
The eruptions of the Icelandic volcano, Eyjafjallajökull, in 2010 brought the hazards associated with volcanic ash sharply into focus. Air routes across northern Europe were disrupted, leaving many passengers stranded and far from home for days on end.
Ocean hazard
But hazards of floating islands of pumice spewed into the ocean from erupting volcanoes are less well-known.
One such island grew from an explosion of the Havre volcano in the South Pacific, between Tonga and New Zealand, in July 2012. The volcano threw out a cubic kilometre of molten magma, which suddenly froze to form bubble-filled pumice.
It is the bubbles trapped in pumice that make it so light – half the density of water – so the rock floats on water. Like natural flotsam, pebble to boulder-sized lumps of pumice clump together. This can create huge floating rafts in the seas around erupting volcanoes, and they can be tens of centimetres thick but thousands of kilometres in length.
Havre’s pumice raft drifting in the Pacific. The scale bar is 20km. Credit: Nature Communications
Records of the use of pumice exist since the time of the Romans and Ancient Greeks. Its rough texture made them effective abrasives to remove dead skin from calluses and corns.
However, today, such floating pumice can pose a hazard for shipping. Hulls can be damaged by abrasion from the hard but light pumice, and when it approaches land these pumice rafts can block harbours and disrupt navigation.
Havre’s pumice island affected an area of ocean twice as big as both islands of New Zealand put together, floating atop the sea. Boats entering the volcanic debris reported engine problems, as the rock and dust clogged their water cooling intakes.
Threat to ocean life
It is not just the effects on shipping that have been a worry. The rafts of pumice stones block the sunlight from reaching plankton in the seas beneath. These plankton form the base of food chain when they convert sunlight to food through photosynthesis, and can be severely affected by floating pumice.
Floating rocks can also act as ferries for exotic invading species, such as shellfish and other organisms that make them their floating home. Indeed, it has been speculated that pumice islands like these were the first home that early life on Earth could have clung to and sprung from.
The study, led by Martin Jutzeler at the National Oceanography Centre in Southampton, UK, shows how the rafts eventually break up into ribbons of rock that can cover a wide area. The simulation techniques that the team has developed will allow the progress of future volcanic rafts to be predicted, and warnings issued to shipping, in the same way as volcanic ash clouds can be forecast for aircraft approaching stratospheric eruptions.
Note : The above story is based on materials provided by The Conversation
This story is published courtesy of The Conversation (under Creative Commons-Attribution/No derivatives). The above story is based on materials provided by
Phosphatized S Bacterium: Round- to oval-shaped apatite-rich nodules in Karelian rocks. These are widespread and have diameters of c. 300-500 micrometers, which are sizes and shapes typical of sulfur-oxidizing bacteria that mediate modern phosphogenesis and used as evidence supporting the interpretation that the ancient nodules represent phosphatized sulfur bacteria. Credit: Avio Lepland/Norges geologiske undersøkelse
Two billion years ago, Earth was recovering from a major environmental upheaval that had caused widespread changes in the planet’s surface conditions.
The oxygenation of the atmosphere and oceans had altered global biogeochemical cycles and triggered the formation of the earliest worldwide phosphorite deposits. These are rocks that contain abundant phosphorus, a key building block of life.
Scientists are now linking the deposition of phosphorus during that time period to the establishment of sulphur bacteria habitats, potentially paving the way for a new approach to astrobiology research.
A recent paper, “Potential influence of sulphur bacteria on Palaeoproterozoic phosphogenesis,” published in the journal Nature Geoscience, concludes that the formation of these phosphorite beds was strongly influenced, if not completely controlled by, the activity of sulphur bacteria. The search for life on other planets might pick up on such geological signposts.
“It would be of great interest to identify P-rich deposits in astrobiology research,” said the paper’s lead author Aivo Lepland at the Geological Survey of Norway (NGU). “Such deposits from extraterrestrial environments may serve as unique archives of geochemical setting and biologic activity.”
Unique Rock Formation
Lepland and his project team drew on research from the organic-rich rocks of the Zaonega Formation in Karelia, Northwest Russia as part of the International Continental Scientific Drilling Program’s Fennoscandian Arctic Russia – Drilling Early Earth Project (FAR DEEP) project in 2007.
Lepland said the project provided a “unique rock record” of drill cores from the early part of the Paleoproterozoic Era (2 to 2.5 billion years ago) to study the causes and consequences of Earth’s oxygenation. Two rock cores contained 2 billion year old phosphorites, which were supplemented with samples collected from nearby outcrops. The project team investigated the micro-fabric (the shapes and sizes) of the samples and analyzed trace elements, including molybdenum (Mo) and uranium (U). The goal was to assess whether or not oxygen was present in the depositional setting. The team also looked at the carbon isotope ratios of the biomass to assess the origin of the organic matter.
The appearance of the first significant worldwide phosphorites has long been seen as a consequence of Earth’s oxygenation more than two billion years ago. However, as Lepland explained, the mechanism and triggers of the event have been poorly understood.
Significant Environmental Change
According to Lepland, the sulphur bacteria that thrive in shallow sediments exert a strong influence on the formation of phosphorite beds. The scientists call the process “S bacteria mediated phosphogenesis,” and propose that it was happening during the early Paleoproterozoic Era.
“The establishment of an environmental niche for S bacteria during that time was the consequence of the increased weathering of landmasses and the supply of sulphur to the ocean—triggered by the oxygenation of the Earth,” said Lepland.
“This, the oldest known and presumed global phosphogenesis event, likely operated the same way as in the modern world,” he added.
P-rich rocks the Zaonega Formation, Karelia: Phosphorous-rich intervals occur within a succession of organic-rich sedimentary rocks that are 2.0 Ga old and record major global environmental changes in the aftermath the rise of atmospheric oxygen at 2.3 Ga. Credit: Avio Lepland/Norges geologiske undersøkelse
Even so, Lepland pointed out that the rocks studied do not provide an answer to the question of how life formed. Primitive life had likely existed on Earth already some 2 billion years before the accumulation of the phosphorus-rich deposits. Cyanobacteria, a phylum of bacteria capable of oxygenic photosynthesis, are thought to have triggered what Lepland describes as “the most significant environmental change in Earth history”: the rise of atmospheric oxygen and the establishment of an aerobic planet.
“Major environmental changes bring about the establishment of new habitats, which in turn set the stage for evolutionary innovation and the diversification and complexity of life,” he said.
Namely, oxygenation brought about important alterations to the sulphur cycle, which provided an environmental niche for sulphur bacteria to create phosphorite beds.
“S bacteria and phosphorite formation thus go together,” he added.
Planets and Water Moons
Matthew Pasek, a planetary scientist and geologist at the University of South Florida (USF), said the study is important in that it identifies microbes as a principle agent in the phosphorus cycle, a useful tool for astrobiologists. “These deposits may serve as good biomarkers on other worlds, indicating a significant amount of biological diversity on an exoplanet,” said Pasek.
He said that an understanding of how phosphate ore is formed helps to give us an idea of how to recognize it in the geologic sequence.
“From a basic science perspective, we’ve known for a while that formation of phosphate ore was likely bio-mediated, but the who, when, and why of these formations wasn’t clear. These deposits followed the rise of oxygen, implying some fairly-advanced microbial metabolism might have been necessary to form these things. This suggests that phosphorite deposits on other worlds might serve as an indicator of advanced microbial life,” he added.
Pasek also speculated that the research, which was carried out in a very specific geological region, may help astrobiological researchers form a better understanding of the type of extraterrestrial environments where such processes are more likely to occur.
“The environment required for the formation of these rocks needs to be a planet or a large moon,” he said. “Small objects in space, such as comets, are not very active and do not vary a lot over small distance scales, so these objects would not be good places to find these types of rocks.”
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Note : The above story is based on materials provided by Astrobio net
Chemical Formula: Ca2B5SiO9(OH)5 Locality: Tick Canyon, Los Angeles Co., California. Name Origin: Named after Henry How of Nova Scotia when he first described it in 1868.
Howlite, a calcium borosilicate hydroxide (Ca2B5SiO9(OH)5), is a borate mineral found in evaporite deposits. Howlite was discovered near Windsor, Nova Scotia in 1868 by Henry How (1828–1879), a Canadian chemist, geologist, and mineralogist. How was alerted to the unknown mineral by miners in a gypsum quarry, who found it to be a nuisance. He called the new mineral silico-boro-calcite; it was given the name howlite by James Dwight Dana shortly thereafter.
The most common form of howlite is irregular nodules, sometimes resembling cauliflower. Crystals of howlite are rare, having been found in only a couple localities worldwide. Crystals were first reported from Tick Canyon, California, and later at Iona, Nova Scotia. Crystals reach a maximum size of about 1 cm. The nodules are white with fine grey or black veins in an erratic, often web-like pattern, opaque with a sub-vitreous lustre. The crystals at Iona are colorless, white or brown and are often translucent or transparent.
Its structure is monoclinic with a Mohs hardness of 3.5 and lacks regular cleavage. Crystals are prismatic and flattened on {100}. The crystals from Tick Canyon are elongated along the 010 axis, while those from Iona are elongated along the 001 axis.
Howlite is commonly used to make decorative objects such as small carvings or jewelry components. Because of its porous texture, howlite can be easily dyed to imitate other minerals, especially turquoise because of the superficial similarity of the veining patterns. The dyed howlite (or magnesite) is marketed as turquenite. Howlite is also sold in its natural state, sometimes under the misleading trade names of “white turquoise” or “white buffalo turquoise,” or the derived name “white buffalo stone.”
This photo of volcanoes in Guatemala was taken from NASA’s C-20A aircraft during a four-week Earth science radar imaging mission deployment over Central and South America. The conical volcano in the center is “Volcan de Agua.” The two volcanoes behind it are, right to left, “Volcan de Fuego” and “Acatenango.” “Volcan de Pacaya” is in the foreground.
The radar imaging mission got underway in early April when the C-20A departed its base in Palmdale, Calif., to collect data over targets in the Gulf Coast area of the southeastern United States. The aircraft, a modified Gulfstream III, is carrying NASA’s Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) instrument in a specialized pod. Developed by NASA’s Jet Propulsion Laboratory in Pasadena, Calif., UAVSAR measures ground deformation over large areas to a precision of 0.04 to 0.2 inches (0.1 to 0.5 centimeters).
The mission schedule calls for the aircraft to make stops in 10 international and U.S. locations, including the Gulf Coast. Research during the deployment is covering a variety of topics, including volcanoes, glaciers, forest structure, levees, and subsidence. It is also providing vegetation data sets for satellite algorithm development. The volcanoes of Central and South America are of interest because of the hazard they pose to nearby population centers. A majority of the research will focus on gathering volcano deformation measurements, with many flight lines being repeats from previous deployments. Surface deformation often precedes other signs of renewed volcanic activity.
Note : The above story is based on materials provided by NASA
Visualization of a computer model. The pathways for the hydrothermal vents at a mid ocean ridge are marked clearly. The arrows indicate the movement of the Earths’ plates at the plate boundaries. Credit: Graphics J. Hasenclever, GEOMAR
Hydrothermal vents in the deep sea, the so-called “black smokers,” are fascinating geological formations. They are home to unique ecosystems, but are also potential suppliers of raw materials for the future. They are driven by volcanic “power plants” in the seafloor and release amounts of energy that could meet the needs of a small town. But how exactly do they extract this energy from the volcanic rock? Researchers at GEOMAR Helmholtz Centre for Ocean Research Kiel have now used computer simulations to understand the underground supply routes. The study is published in the international journal Nature.
About ten years after the first moon landing, scientists on earth made a discovery that proved that our home planet still holds a lot of surprises in store for us. Looking through the portholes of the submersible ALVIN near the bottom of the Pacific Ocean in 1979, American scientists saw for the first time chimneys, several meters tall, from which black water at about 300 degrees and saturated with minerals shot out. What we have found out since then: These “black smokers,” also called hydrothermal vents, exist in all oceans. They occur along the boundaries of tectonic plates along the submarine volcanic chains. However, to date many details of these systems remain unexplained.
One question that has long and intensively been discussed in research is: Where and how deep does seawater penetrate into the seafloor to take up heat and minerals before it leaves the ocean floor at hydrothermal vents? This is of enormous importance for both, the cooling of the underwater volcanoes as well as for the amount of materials dissolved. Using a complex 3-D computer model, scientists at GEOMAR Helmholtz Centre for Ocean Research Kiel were now able to understand the paths of the water toward the black smokers.
In general, it is well known that seawater penetrates into Earth’s interior through cracks and crevices along the plate boundaries. The seawater is heated by the magma; the hot water rises again, leaches metals and other elements from the ground and is released as a black colored solution. “However, in detail it is somewhat unclear whether the water enters the ocean floor in the immediate vicinity of the vents and flows upward immediately, or whether it travels long distances underground before venting,” explains Dr. Jörg Hasenclever from GEOMAR.
This question is not only important for the fundamental understanding of processes on our planet. It also has very practical implications. Some of the materials leached from the underground are deposited on the seabed and form ore deposits that may be of economically interest. There is a major debate, however, how large the resource potential of these deposits might be. “When we know which paths the water travels underground, we can better estimate the quantities of materials released by black smokers over thousands of years,” says Hasenclever.
Hasenclever and his colleagues have used for the first time a high-resolution computer model of the seafloor to simulate a six kilometer long and deep, and 16 kilometer wide section of a mid-ocean ridge in the Pacific. Among the data used by the model was the heat distribution in the oceanic crust, which is known from seismic studies. In addition, the model also considered the permeability of the rock and the special physical properties of water.
The simulation required several weeks of computing time. The result: “There are actually two different flow paths — about half the water seeps in near the vents, where the ground is very warm. The other half seeps in at greater distances and migrates for kilometers through the seafloor before exiting years later.” Thus, the current study partially confirmed results from a computer model, which were published in 2008 in the scientific journal Science. “However, the colleagues back then were able to simulate only a much smaller region of the ocean floor and therefore identified only the short paths near the black smokers,” says Hasenclever.
The current study is based on fundamental work on the modeling of the seafloor, which was conducted in the group of Professor Lars Rüpke within the framework of the Kiel Cluster of Excellence “The Future Ocean.” It provides scientists worldwide with the basis for further investigations to see how much ore is actually on and in the seabed, and whether or not deep-sea mining on a large scale could ever become worthwhile. “So far, we only know the surface of the ore deposits at hydrothermal vents. Nobody knows exactly how much metal is really deposited there. All the discussions about the pros and cons of deep-sea ore mining are based on a very thin database,” says co-author Prof. Dr. Colin Devey from GEOMAR. “We need to collect a lot more data on hydrothermal systems before we can make reliable statements.”
Note : The above story is based on materials provided by Helmholtz Centre for Ocean Research Kiel (GEOMAR).
Chemical Formula: (Ca,Na)2–3(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2
Hornblende is a complex inosilicate series of minerals (ferrohornblende – magnesiohornblende). It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole.
Hornblende is an isomorphous mixture of three molecules; a calcium-iron-magnesium silicate, an aluminium-iron-magnesium silicate, and an iron-magnesium silicate.
The general formula can be given as (Ca,Na)2–3(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2
Occurrence
Hornblende is a common constituent of many igneous and metamorphic rocks such as granite, syenite, diorite, gabbro, basalt, andesite, gneiss, and schist.
It is the principal mineral of amphibolites. Very dark brown to black hornblendes that contain titanium are ordinarily called basaltic hornblende, from the fact that they are usually a constituent of basalt and related rocks. Hornblende alters easily to chlorite and epidote.
A rare variety of hornblende contains less than 5% of iron oxide, is gray to white in color, and named edenite, from its locality in Edenville, Orange County, New York.
Other minerals in the hornblende series include:
pargasite
hastingsite
tschermakite
Physical Properties
Color: black to dark green. Luster: vitreous to dull. Transparency: Crystals are generally opaque but thin crystals or exceptional specimens can be translucent. Crystal System : Monoclinic; 2/m Cleavage : imperfect in two directions at 56 and 124 degrees. Fracture : uneven. Hardness : 5 – 6. Specific Gravity : approximately 2.9 – 3.4 (somewhat above average for translucent minerals) Streak : brown to gray.
The preserved bones of Kryptodrakon progenitor (shown here in different views) has yielded new discoveries on the origin of the pterodactyloids, a group of flying reptiles that would go on to become the largest known flying creatures to have ever existed. Credit: Illustration by Brian Andres
An international research team, including a George Washington University (GW) professor, has discovered and named the earliest and most primitive pterodactyloid — a group of flying reptiles that would go on to become the largest known flying creatures to have ever existed — and established they flew above Earth some 163 million years ago, longer than previously known.
Working from a fossil discovered in northwest China, the project — led by University of South Florida (USF) paleontologist Brian Andres, James Clark of the GW Columbian College of Arts and Sciences and Xu Xing of the Chinese Academy of Sciences — named the new pterosaur species Kryptodrakon progenitor.
Through scientific analysis the team established it as the first pterosaur to bear the characteristics of the Pterodactyloidea, which would become the dominant winged creatures of the prehistoric world. Their research will be published online Thursday in the journal Current Biology.
“This finding represents the earliest and most primitive pterodactyloid pterosaur, a flying reptile in a highly specialized group that includes the largest flying organisms,” says Chris Liu, program director in the National Science Foundation’s Division of Earth Sciences. “The research has extended the fossil record of pterodactyloids by at least five million years to the Middle-Upper Jurassic boundary about 163 million years ago.”
Kryptodrakon progenitor lived around the time of the Middle-Upper Jurassic boundary. Through studying the fossil fragments, researchers also determined that the pterodactyloids originated, lived, and evolved in terrestrial environments — rather than marine environments where other specimens have been found.
The fossil is of a small pterodactyloid with a wingspan estimate of about 4.5 feet. Pterodactyloids — who went on to evolve into giant creatures, some as big as small planes — went extinct with the dinosaurs, about 66 million years ago. Pterosaurs are considered close relatives to the dinosaurs, but are not dinosaurs themselves.
The discovery provides new information on the evolution of pterodactyloids, Dr. Andres said. This area was likely a flood plain at the time the pterosaur lived, Dr. Andres said. As the pterosaurs evolved, their wings changed from being narrow, which are more useful for marine environments, to being more broad near the origin of the pterodactyloids — helpful in navigating land environments.
“He (Kryptodrakon progenitor) fills in a very important gap in the history of pterosaurs,” Dr. Andres said. “With him, they could walk and fly in whole new ways.”
The fossil that became the centerpiece of the research was discovered in 2001 by Chris Sloan, formerly of National Geographic and now president of Science Visualization. It was found in a mudstone of the Shishugou Formation of northwest China on an expedition led by Drs. Xu and Clark when Dr. Andres was a graduate student with Dr. Clark at GW. The desolate and harsh environment has become known to scientists worldwide as having “dinosaur death pits” for the quicksand in the area that trapped an extraordinary range of prehistoric creatures, stacking them on top of each other, including one of the oldest tyrannosaurs, Guanlong. Kryptodrakon progenitor was found 35 meters below an ash bed that has been dated back to more than 161 million years.
The specimen is housed at the Institute of Vertebrate Paleontology and Paleoanthropology, Beijing, China. The name Kryptodrakon progenitor comes from Krypto (hidden) and drakon (serpent), referring to “Crouching Tiger, Hidden Dragon” filmed near where the species was discovered, and progenitor (ancestral or first-born), referring to its status as the earliest pterodactyloid, Dr. Andres said.
“Kryptodrakon is the second pterosaur species we’ve discovered in the Shishugou Formation and deepens our understanding of this unusually diverse Jurassic ecosystem,” said Dr. Clark, GW’s Ronald B. Weintraub Professor of Biology. “It is rare for small, delicate fossils to be preserved in Jurassic terrestrial deposits, and the Shishugou fauna is giving us a glimpse of what was living alongside the behemoths like Mamenchisaurus.”
The scientists write that the pterosaurs were a diverse group of Mesozoic flying reptiles that underwent a body plan reorganization, adaptive radiation, and replacement of earlier forms midway through their long history, resulting in the origin of the Pterodactyloidea, a highly-specialized group of pterosaurs of which Kryptodrakon is the earliest and most primitive species.
This new take on the ecological history of pterosaurs is supported by a significant correlation found between wing shape and environment in pterosaurs and modern flying vertebrates, like bats and birds, the researchers said. Pterosaurs, however, are not the ancestors of birds — those are the dinosaurs — and scientists still believe that pterosaurs did not evolve into birds or other modern animals humans would know.
The fieldwork was supported by the National Natural Science Foundation of China, the National Science Foundation Division of Earth Sciences of the USA, the Chinese Academy of Sciences, the National Geographic Society, the Jurassic Foundation, the Hilmar Sallee bequest, and the George Washington University. Study of the specimen was supported by the Chinese Academy of Sciences, the National Science Foundation Division of Earth Sciences and the National Natural Science Foundation of China.
Note : The above story is based on materials provided by George Washington University.
A reconstruction of Earth’s earliest ocean in the laboratory revealed the spontaneous occurrence of the chemical reactions used by modern cells to synthesize many of the crucial organic molecules of metabolism (bottom pathway). Whether and how the first enzymes adopted the metal-catalyzed reactions described by the scientists remain to be established. Credit: Molecular Systems Biology / Creative Commons Attribution Non Commercial License (CC BY-NC 3.0)
Researchers from the University of Cambridge have published details about how the first organisms on Earth could have become metabolically active. The results, which are reported in the journal Molecular Systems Biology, permit scientists to speculate how primitive cells learned to synthesize their organic components — the molecules that form RNA, lipids and amino acids. The findings also suggest an order for the sequence of events that led to the origin of life.
A reconstruction of Earth’s earliest ocean in the laboratory revealed the spontaneous occurrence of the chemical reactions used by modern cells to synthesize many of the crucial organic molecules of metabolism. Previously, it was assumed that these reactions were carried out in modern cells by metabolic enzymes, highly complex molecular machines that came into existence during the evolution of modern organisms.
Almost 4 billion years ago life on Earth began in iron-rich oceans that dominated the surface of the planet. An open question for scientists is when and how cellular metabolism, the network of chemical reactions necessary to produce nucleic acids, amino acids and lipids, the building blocks of life, appeared on the scene.
The observed chemical reactions occurred in the absence of enzymes but were made possible by the chemical molecules found in the Archean sea. Finding a series of reactions that resembles the “core of cellular metabolism” suggests that metabolism predates the origin of life. This implies that, at least initially, metabolism may not have been shaped by evolution but by molecules like RNA formed through the chemical conditions that prevailed in the earliest oceans.
“Our results demonstrate that the conditions and molecules found in the Earth’s ancient oceans assisted and accelerated the interconversion of metabolites that in modern organisms make up glycolysis and the pentose-phosphate pathways, two of the essential and most centrally placed reaction cascades of metabolism,” says Dr. Markus Ralser, Group Leader at the Department of Biochemistry at the University of Cambridge and the National Institute for Medical Research. “In our reconstructed version of the ancient Archean ocean, these metabolic reactions were particularly sensitive to the presence of ferrous iron that helped catalyze many of the chemical reactions that we observed.” From the analysis of early oceanic sediments, geoscientists such as Alexandra V. Turchyn from the Department of Earth Sciences at the University of Cambridge, one of the co-authors of the study, concluded that soluble forms of iron were one of the most frequently found molecules in the prebiotic oceans.
The scientists reconstructed the conditions of this prebiotic sea based on the composition of various early sediments described in the scientific literature. The different metabolites were incubated at high temperatures (50-90oC) similar to what might be expected close to a hydrothermal vent of an oceanic volcano, a temperature that would not support the activity of conventional protein enzymes. The chemical products were separated and analyzed by liquid chromatography tandem mass spectrometry.
Some of the observed reactions could also take place in water but were accelerated by the presence of metals that served as catalysts. “In the presence of iron and other compounds found in the oceanic sediments, 29 metabolic-like chemical reactions were observed, including those that produce some of the essential chemicals of metabolism, for example precursors of the building blocks of proteins or RNA,” says Ralser. “These results indicate that the basic architecture of the modern metabolic network could have originated from the chemical and physical constraints that existed on the prebiotic Earth.”
The detection of one of the metabolites, ribose 5-phosphate, in the reaction mixtures is particularly noteworthy. Its availability means that RNA precursors could in theory give rise to RNA molecules that encode information, catalyze chemical reactions and replicate. Whether and how the first enzymes adopted the metal-catalyzed reactions described by the scientists remain to be established.
Note : The above story is based on materials provided by European Molecular Biology Organization.
Chemical Formula: Ba(Mn4+6Mn3+2)O16 Locality: Manganese deposits of the Central Provinces of India. Name Origin: Named for Thomas Henry Holland (1868-1947), Director of the Indian Geologic Survey.
Physical Properties of Hollandite
Color: Grayish black, Black, Silver gray. Density: 4.7 – 5, Average = 4.84 Diaphaneity: Opaque Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 4-6 Luminescence: Non-fluorescent. Luster: Earthy (Dull) Streak: black
Michigan State University geologist’s new discovery helps solve mystery source of African lava. Credit: Tyrone Rooney
Floods of molten lava may sound like the stuff of apocalyptic theorists, but history is littered with evidence of such past events where vast lava outpourings originating deep in Earth accompany the breakup of continents.
New research at Michigan State University shows that the source of some of these epic outpourings, however, may not be as deep as once thought. The results, published in the journal Geology, show that some of these lavas originated near the surface rather than deep within the mantle.
When geoscientists want to learn more about massive lava flows — the kind that accompany continental rifting and continent break up — they conduct field studies of the African tectonic plate. Here, the Great Rift Valley of East Africa provides a snapshot of how a continent can be torn apart.
Armed with new technology, scientists can better translate the story that is stored in the rift’s fossilized lava flows. What they learn is applicable to continental breakup around the globe, said Tyrone Rooney, MSU geologist.
“For decades, there’s been a big debate as to where the lavas from this massive outpouring came from,” he said. “Did they emit from deep within Earth? Or was there some contribution from shallower sources? Our paper shows that some lavas came from within the African tectonic plate itself.”
To clarify, many nonscientists think of big eruptions in terms of Mount St. Helens or Vesuvius. These were mere drops in a bucket compared to what Rooney and his colleagues are studying. The ancient African outpouring is estimated to have poured out 350,000 cubic kilometers of lava about 30 million years ago. That’s comparable to twice the amount of water in all the world’s lakes, Rooney explained.
While much of this lava is probably derived from deep sources, Rooney’s team found that some parts of the tectonic plate also have melted to form an unusual group of lavas in Ethiopia. The researchers showed that the rocks, artifacts from the ancient outpouring, had chemical signatures of materials found in the lithosphere and were distinctly different from most of the other rocks in Ethiopia.
Rooney and his team were able to confirm their findings because, in part, of having access to tools that their predecessors merely imagined. The new approaches are allowing them to challenge long-standing theories in their field.
For example, mass spectrometers are employed to reveal the rocks’ chemical signatures. By identifying the lavas’ elemental characteristics, the scientists can trace their origin to the surface or from deep in the mantle. Using lasers, scientists can transform rock into a fine mist and measure its composition.
In a surprise finding, the team’s lab experiments revealed that the Ethiopian samples matched rocks collected from other distant regions. The lavas in Arabia, Jordan, Egypt and Sudan are similar, which means that some of the ingredients that supply the massive outpourings, or basalt floods, have a shallow source that is tapped as the continents split apart. Indeed the seeds of the lithosphere’s own destruction maybe contained within it, Rooney said.
“We’re interested in this because these massive outpourings happen around the same time continents break apart, create new oceans and affect the planet and the environment on a global scale,” he said. “So knowing the source of the lava gives us insights into a process that we still know little about.”
Rooney’s research laid the groundwork for a National Science Foundation grant that will allow him to continue to unlock the secrets of tectonic forces and continental rifting.
Note : The above story is based on materials provided by Michigan State University.
Epiceratherium naduongense sp. nov. vom Krokodil zerbissen. Credit: Senckenberg
A team of scientists from the University of Tübingen and the Senckenberg Center for Human Evolution and Palaeoenvironment Tübingen was able to recover fossils of two previously unknown mammal species that lived about 37 million years ago. The newly described mammals show a surprisingly close relationship to prehistoric species known from fossil sites in Europe. The location: The open lignite-mining Na Duong in Vietnam. Here, the team of scientists was also able to make a series of further discoveries, including three species of fossilized crocodiles and several new turtles.
Southeast Asia is considered a particularly species-rich region, even in prehistoric times — a so-called hotspot of biodiversity. For several decades now, scientists have postulated close relationships that existed in the late Eocene (ca. 38-34 million years ago) between the faunas of that region and Europe. The recent findings by the research team under leadership of Prof. Dr. Madelaine Böhme serve as proof that some European species originated in Southeast Asia.
Rhinoceros and Coal beast
One of the newly described mammals is a rhinoceros, Epiaceratherium naduongense. The anatomy of the fossil teeth allows identifying this rhinoceros as a potential forest dweller. The other species is the so-called “Coal Beast,” Bakalovia orientalis. This pig-like ungulate, closely related to hippos, led a semi-aquatic lifestyle, i.e., it preferred the water close to bank areas. At that time, Na Duong was a forested swampland surrounding Lake Rhin Chua. The mammals’ remains bear signs of crocodile attacks. Indeed, the excavation site at Na Duong contains the fossilized remains of crocodiles up to 6 meters in length.
From island to island toward Europe
In the Late Eocene, the European mainland presented a very different aspect than it does today. Italy and Bulgaria were part of an island chain in the Tethys Sea. These islands spanned several thousand kilometers between what later became Europe and India. European fossils from that epoch are very rare, since little material has been preserved due to the folding of mountains and erosion. Yet, the two new species had relatives in this area: A rhinoceros Epiaceratherium bolcense closely resembling the one from Na Duong was found in Italy (Monteviale). Fossil finds of Epiaceratherium magnum from Bavaria indicate that rhinoceroses reached continental Europe no later than 33 million years ago and colonized the landmass. The coal beast did not quite make it to the European mainland — but it certainly reached the so-called Balkano-Rhodopen Island: a fossilized coal beast very similar to Bakalovia orientalis was unearthed in present-day Bulgaria.
Research among coal dust and excavators
The open mining pit Na Duong is still active. While the scientists conduct their excavations, lignite is being extracted nearby. Since 2008, the international research team around Prof. Dr. Madelaine Böhme from the Senckenberg Center for Human Evolution and Palaeoenvironment (HEP) at the University of Tübingen has studied the prehistoric ecosystem and the fossils of Na Duong in Vietnam. This research revealed that the lignite seams contained a globally important fossil deposit from the Paleogene interval. Originally, scientists had expected to find fossils from the younger Cenozoic (up to 23 million years ago) at the site. This ecosystem, which the scientists from Vietnam, France and Germany explore and reconstruct in ever more detail from one excavation season to the next, is a 37 million year-old swamp forest in a tropical to subtropical climate. Up to 600 trees grew there per hectare, and their crowns reached heights of up to 35 meters.
Note : The above story is based on materials provided by Senckenberg Research Institute and Natural History Museum.
Chemical Formula: Mn Zn2(SiO4)(OH)2 Locality: Franklin, Sussex Co., New Jersey, USA. Name Origin: Named for H. H. Hodgkinson, assistant underground supervisor of Franklin mine who discovered the mineral.
Hodgkinsonite is a rare zinc manganese silicate mineral Mn Zn2(SiO4)(OH)2. It crystallizes in the monoclinic system and typically forms radiating to acicular prismatic crystals with variable color from pink, yellow-red to deep red. Hodgkinsonite was discovered in 1913 by H. H. Hodgkinson, for whom it is named in Franklin, New Jersey, and it is only found in that area.
Physical Properties
Color: Light pink, Orange, Reddish brown. Density: 3.91 Diaphaneity: Translucent to subtranslucent to opaque Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 4.5-5 – Near Apatite Luminescence: Fluorescent, Long UV=red, weak pink dull dark purple. Luster: Vitreous (Glassy)
Photo:
This sample of hodgkinsonite is displayed in the Smithsonian Museum of Natural History. The sample is about 20 cm across and is from Franklin, New Jersey.
Havre Seamount pumice raft drift graph. Credit: University of Southampton
A technique presented in Nature Communications by researchers from the National Oceanography Centre Southampton (NOCS) and the University of Southampton will aid in predicting the dispersal and drift patterns of large floating ‘islands’ of pumice created by volcanic eruptions at sea.
Known as pumice rafts, these large mobile accumulations of pumice fragments can spread to affect a considerable area of the ocean, damaging vessels and disrupting shipping routes for months or even years. The ability to predict where these rafts will end up could give enough advance warning for protective measures to be put in place on shipping routes or in harbours where the presence of pumice is hazardous.
Martin Jutzeler, Post-Doctoral Research Fellow at NOCS, and a team of colleagues simulated the drift of a massive 400km2 raft of pumice from Havre, a deep submarine volcano in the southwest Pacific, using a high-resolution model of the global ocean circulation. The team, which included researchers from the University of Tasmania in Australia, the University of Otago in New Zealand and Stanford University in the United States, then tested the results against satellite imagery plus direct observations from sailing crews, to show that they can accurately reproduce surface drift using this method and note that this large-scale natural experiment validates the physics of the model.
This technique, they believe, can be used to forecast dispersal routes of potentially hazardous pumice rafts from future eruptions, mitigating potential risks to ships and allowing authorities to protect harbours. The same high-fidelity particle tracking can also be used to predict the spread of other floating objects in surface ocean waters, such as anthropogenic waste or passively-drifting organisms.
“Pumice in rafts can drift for years, become waterlogged and sink, or become stranded on shorelines. For a variety of reasons, it’s important that we develop a better understanding of their formation, movement and dispersal over time,” said Dr Bob Marsh, Reader in Physical Oceanography at the University of Southampton who was part of the research team. “The pumice raft used in our research was formed by the impressive, deep submarine eruption of the Havre caldera volcano in the southwest Pacific in July 2012 was perfect for our research. The eruption was far from coastal interferences so produced a single raft spanning over 400 square kilometres in one day, thus initiating a gigantic, high-precision, natural experiment in surface dispersion, in a region dominated by eddies — the oceanic equivalent of weather systems.”
“Our research shows how observed raft dispersal can be accurately reproduced by simulating drift and dispersal patterns using currents from an eddy-resolving ocean model hindcast,” Dr Marsh continued. “For future eruptions that produce potentially hazardous pumice rafts, our technique allows real-time forecasts of dispersal routes, in addition to inference of ash/pumice deposit distribution in the deep ocean.”
Note : The above story is based on materials provided by University of Southampton.
The Congo River is a river in Africa and the world’s deepest river with measured depths in excess of 220 m (720 ft).[2] It is the second largest river in the world by volume of water discharged. Additionally, its overall length of 4,700 km (2,920 mi) makes it the ninth longest river.
The Congo gets its name from the ancient Kingdom of Kongo which inhabited the lands at the mouth of the river. The Democratic Republic of the Congo and the Republic of the Congo, both countries lying along the river’s banks, are named after it. Between 1971 and 1997 the government of then-Zaire called it the Zaire River.
Basin and course
Course and Drainage basin of the Congo River with topography shading.
The Congo’s drainage basin covers 4,014,500 square kilometres (1,550,000 sq mi). The Congo’s discharge at its mouth ranges from 23,000 cubic metres per second (810,000 cu ft/s) to 75,000 cubic metres per second (2,600,000 cu ft/s), with an average of 41,000 cubic metres per second (1,400,000 cu ft/s).
The river and its tributaries flow through the Congo rainforest, the second largest rain forest area in the world, second only to the Amazon Rainforest in South America. The river also has the second-largest flow in the world, behind the Amazon; the third-largest drainage basin of any river, behind the Amazon and Plate rivers; and is one of the deepest rivers in the world, at depths greater than 220 m (720 ft). Because its drainage basin includes areas both north and south of the equator, its flow is stable, as there is always at least one part of the river experiencing a rainy season.
The sources of the Congo are in the highlands and mountains of the East African Rift, as well as Lake Tanganyika and Lake Mweru, which feed the Lualaba River, which then becomes the Congo below Boyoma Falls. The Chambeshi River in Zambia is generally taken as the source of the Congo in line with the accepted practice worldwide of using the longest tributary, as with the Nile River.
The Congo flows generally northwards from Kisangani just below the Boyoma falls, then gradually bends southwestwards, passing by Mbandaka, joining with the Ubangi River, and running into the Pool Malebo (Stanley Pool). Kinshasa (formerly Léopoldville) and Brazzaville are on opposite sides of the river at the Pool, where the river narrows and falls through a number of cataracts in deep canyons (collectively known as the Livingstone Falls), running by Matadi and Boma, and into the sea at the small town of Muanda.
The Congo River Basin is one of the distinct physiographic sections of the larger Mid-African province, which in turn is part of the larger African massive physiographic division.
Economic importance
Although the Livingstone Falls prevent access from the sea, nearly the entire Congo is readily navigable in sections, especially between Kinshasa and Kisangani. Large river steamers worked the river until quite recently. The Congo River still is a lifeline in a land with few roads or railways.
Railways now bypass the three major falls, and much of the trade of Central Africa passes along the river, including copper, palm oil (as kernels), sugar, coffee, and cotton. The river is also potentially valuable for hydroelectric power, and the Inga Dams below Pool Malebo are first to exploit the Congo river.
Hydro-electric power
The Congo River is the most powerful river in Africa. During the rainy season over 50,000 cubic meters (1,800,000 cu ft) of water per second flow into the Atlantic Ocean. Opportunities for the Congo River and its tributaries to generate hydropower are therefore enormous. Scientists have calculated that the entire Congo Basin accounts for thirteen percent of global hydropower potential. This would provide sufficient power for all of sub-Saharan Africa’s electricity needs.Currently there are about forty hydropower plants in the Congo Basin. The largest is the Inga Falls dam, about 200 km (120 mi) southwest of Kinshasa. The prestigious Inga Project was launched in the early 1970s and at that time the first dam was completed. The plan as originally conceived called for the construction of five dams that would have had a total generating capacity of 34,500 megawatts. To date only two dams have been built, which are the Inga I and Inga II, with a total of fourteen turbines.
In February 2006, South Africa’s state-owned power company, Eskom, announced a proposal to increase the capacity of the Inga dramatically through improvements and the construction of a new hydroelectric dam. The project would bring the maximum output of the facility to 40 GW, twice that of China’s Three Gorges Dam.
It is feared that these new hydroelectric dams could lead to the extinction of many of the fish species that are endemic to the river.
Natural history
The beginning of the Livingstone Falls (Lower Congo Rapids) near Kinshasa
The Congo River formed 1.5-2 million years BP during the Pleistocene.
The Congo’s formation may have led to the allopatric speciation of the bonobo and the common chimpanzee from their most recent common ancestor. The bonobo is endemic to the humid forests in the region, as are other iconic species like the Allen’s swamp monkey, dryas monkey, aquatic genet, okapi and Congo Peafowl.
In terms of aquatic life, the Congo River Basin has a very high species richness, and among the highest known concentrations of endemics. Until now, almost 700 fish species have been recorded from the Congo River Basin, and large sections remain virtually unstudied. Due to this and the great ecological differences between the regions in the basin, it is often divided into multiple ecoregions (instead of treating it as a single ecoregion). Among these ecoregions, the Lower Congo Rapids alone has more than 300 fish species, including approximately 80 endemics while the southwestern part (Kasai Basin) alone has about 200 fish species, of which about a quarter are endemic. The dominant fish families–at least in parts of the river–are Cyprinidae (carp/cyprinids, such as Labeo simpsoni), Mormyridae (elephantfishes), Alestidae (African tetras), Mochokidae (squeaker catfishes), and Cichlidae (cichlids). Among the natives in the river is the huge, highly carnivorous giant tigerfish. Two of the more unusual endemic cichlids are the whitish (non-pigmented) and blind Lamprologus lethops, which is believed to live as deep as 160 metres (520 ft) below the surface, and Heterochromis multidens, which appears to be more closely related to cichlids of the Americas than other Africa cichlid. There are also numerous endemic frogs and snails. Several hydroelectric dams are planned on the river, and these may lead to the extinction of many of the endemics.
Several species of turtles, and the slender-snouted, Nile and dwarf crocodile are native to the Congo River Basin.
Note : The above story is based on materials provided by Wikipedia
Hibonite Esiva eluvials, Maromby, Amboasary District, Anosy (Fort Dauphin) Region, Tul�ar (Toliara) Province, Madagascar (TYPE LOCALITY) Miniature, 3.4 x 3.4 x 2.8 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”
Chemical Formula: (Ca,Ce)Al12O19 Locality: Esiva, near Taolanaro (Fort Dauphin), and near Ambindandrakemba, Madagascar. Name Origin: Named for Paul Hibon, who discovered the mineral.
Hibonite ((Ca,Ce)(Al,Ti,Mg)12O19) is a brownish black mineral with a hardness of 7.5-8.0 and a hexagonal crystal structure. It is rare, but is found in high-grade metamorphic rocks on Madagascar. Some presolar grains in primitive meteorites consist of hibonite. Hibonite also is a common mineral in the Ca-Al-rich inclusions (CAIs) found in some chondritic meteorites. Hibonite is closely related to hibonite-Fe (IMA 2009-027, ((Fe,Mg)Al12O19)) an alteration mineral from the Allende meteorite.
A very rare gem, Hibonite was discovered in Madagascar by Paul Hibon, a French prospector.
Physical Properties
Cleavage: {0001} Good, {1010} Parting Color: Black, Black, Reddish brown. Density: 3.84 Diaphaneity: Opaque Fracture: Sub Conchoidal – Fractures developed in brittle materials characterized by semi-curving surfaces. Hardness: 7.5-8 Luster: Metallic Streak: reddish brown
Photos :
Hibonite Esiva, Maromby Commune, Amboasary Department, Anosy (Fort Dauphin) Region, Madagascar (TYPE LOCALITY) Miniature, 4.0 x 3.9 x 0.8 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”Hibonite Amboasary, Anosy (Fort Dauphin) Region, Tul�ar (Toliara) Province, Madagascar Cabinet, 10.3 x 7.6 x 5.0 cm “Courtesy of Rob Lavinsky, The Arkenstone, www.iRocks.com”Vohimena deposit (Vohimena Nord), Tranomaro Commune, Amboasary District, Anosy Region (Fort Dauphin Region), Tuléar Province (Toliara), Madagascar
A local resident shows a fragment thought to be part of a meteorite collected in a snow covered field in the Yetkulski region outside the Urals city of Chelyabinsk February 24, 2013. Credit: Reuters/Andrei Romanov
(Reuters) – The chance of a city-killing asteroid striking Earth is higher than scientists previously believed, a non-profit group building an asteroid-hunting telescope said on Tuesday.
A global network that listens for nuclear weapons detonations detected 26 asteroids that exploded in Earth’s atmosphere from 2000 to 2013, data collected by the Comprehensive Nuclear Test Ban Treaty Organization shows.
The explosions include the February 15, 2013, impact over Chelyabinsk, Russia, which left more than 1,000 people injured by flying glass and debris.
“There is a popular misconception that asteroid impacts are extraordinarily rare … that’s incorrect,” said former astronaut Ed Lu, who now heads the California-based B612 Foundation.
The foundation on Tuesday released a video visualization of the asteroid strikes in an attempt to raise public awareness of the threat.
Asteroids as small as about 131 feet – less than half the size of an American football field – have the potential to level a city, Lu told reporters on a conference call
“Picture a large apartment building – moving at Mach 50,” Lu said.
Mach 50 is 50 times the speed of sound, or roughly 38,000 mph.
NASA already has a program in place that tracks asteroids larger than 0.65 mile. An object of this size, roughly equivalent to a small mountain, would have global consequences if it struck Earth.
An asteroid about 6 miles in diameter hit Earth some 65 million years ago, triggering climate changes that are believed to have caused the dinosaurs – and most other life on Earth at the time – to die off.
“Chelyabinsk taught us that asteroids of even 20-meter (66-foot) size can have substantial effect,” Lu said.
City-killer asteroids are forecast to strike about once every 100 years, but the prediction is not based on hard evidence.
B612 intends to address that issue with a privately funded, infrared space telescope called Sentinel that will be tasked to find potentially dangerous asteroids near Earth. The telescope, which will cost about $250 million, is targeted for launch in 2018.
B612 takes its name from the fictional planet in the book “The Little Prince,” by French author and aviator Antoine de Saint-Exupery.
Video :
Note : The above story is based on materials provided by Irene KlotzCAPE CANAVERAL, Florida for Reuters
Yale scientists have clarified how calcium carbonate from rocks transforms into carbon dioxide gas by studying Mediterranean marble. Here, a microscopic view of Epidote mineral crystals, which formed from the dissolution reactions that liberated carbon dioxide. The individual crystals are only a few millimeters long. Credit: Jay Ague/Yale
Scientists at Yale University have clarified how carbon dioxide escapes minerals deep inside Earth and seeps into the planet’s atmosphere, a significant step in the planet’s natural carbon cycle. Deeper insight into the cycle helps scientists more accurately assess how humans are altering carbon’s movement and affecting the planet’s climate.
Carbon—the basis for life—is present in the earth, seas, sky, and every living creature. Geologists have long known that significant amounts of carbon are stored as calcium carbonate in certain rocks, such as marble, and returned to the atmosphere through volcanic eruptions. But how calcium carbonate from rocks transforms into carbon dioxide gas has been unclear.
In new research published in the May 2014 issue of Nature Geoscience, the Yale team presents evidence that the mineral aragonite, which is composed of calcium carbonate, can dissolve to release carbon dioxide in water-based fluid. This reaction occurs in high-pressure subduction zones, places where one slab of Earth’s outer rocky shell slides beneath another.
“The dissolution of calcium carbonate in the fluid of subduction zones releases far more carbon dioxide than conventional models predict and could be an important part of the global carbon cycle,” said lead author Jay J. Ague, professor and chair of Yale’s Department of Geology & Geophysics and curator-in-charge of the Mineralogy and Meteoritics collections at the Yale Peabody Museum of Natural History.
Ague’s co-author is Stefan Nicolescu, collection manager for Mineralogy and Meteoritics at the Yale Peabody Museum.
At subduction zones, extreme pressures and temperatures break rocks down and release the carbon as carbon dioxide. The carbon dioxide can become incorporated in magmas that ascend and produce volcanic eruptions, which shoot carbon dioxide back into the atmosphere.
Ague and Nicolescu collected marble rocks from an ancient subduction zone exposed on the Greek islands of Syros and Tinos. Some of the rocks were collected at fluid-flow sites; others were not. They found that the amount of calcium carbonate, the precursor to dissolved carbon dioxide, drastically decreased as they moved closer to fluid conduits. This pattern, they argue, suggests the fluid was instrumental in removing both calcium and carbon dioxide from the rocks.
The discovery of calcium carbonate dissolution did not fit the conventional hypotheses for how carbon dioxide is released from subducted rocks. Devolatilization reactions, which consume or produce water and produce more limited amounts of carbon dioxide, were thought to be the main method of carbon dioxide release from minerals in subduction zones. But these reactions could not account for the large carbon dioxide losses observed in the rock samples, leading Ague and Nicolescu to challenge the conventional wisdom.
Other recent research, including detailed studies of the chemistry of subduction zone fluids, had suggested that other types of reactions might be responsible for carbon dioxide production in subduction zones. What was lacking were field examples suitable for testing hypotheses of carbon dioxide reaction, the researchers said. Ague and Nicolescu argue that the carbon-depleted marbles they found in Greece constitute an important window into how chemical reactions operate to release carbon dioxide from Earth’s deep interior.
Said Ague, “The new hypothesis of carbonate mineral dissolution survived multiple rigorous tests, which was exciting because it can account for geologic relationships that have remained enigmatic for a long time.”
The paper is titled “Carbon dioxide released from subduction zones by fluid-mediated reactions.”
Reference:
“Carbon dioxide released from subduction zones by fluid-mediated reactions.” Jay J. Ague, Stefan Nicolescu. Nature Geoscience (2014) DOI: 10.1038/ngeo2143. Received 19 September 2013 Accepted 17 March 2014 Published online 20 April 2014
Note : The above story is based on materials provided by Yale University
Chemical Formula: (Ca,Na)2-3Al3(Al,Si)2Si13O36·12H2O Locality: Glasgow, Strathclyde (Dumbartonshire), Scotland. Name Origin: Named after the English mineral collector, John Henry Heuland (1778-1856), a British mineral collector and dealer. Ca modifier added by zeolite nomenclature committee.
Heulandite is the name of a series of tecto-silicate minerals of the zeolite group. Prior to 1997, heulandite was recognized as a mineral species, but a reclassification in 1997 by the International Mineralogical Association changed it to a series name, with the mineral species being named:
Heulandite-Ca
Heulandite-Na
Heulandite-K
Heulandite-Sr
Heulandite-Ba (described in 2002).
Heulandite-Ca, the most common of these, is a hydrous calcium and aluminium silicate, (Ca,Na)2-3Al3(Al,Si)2Si13O36·12H2O. Small amounts of sodium and potassium are usually present replacing part of the calcium. Strontium replaces calcium in the heulandite-Sr variety. The appropriate species name depends on the dominant element. The species are visually indistinguishable, and the series name heulandite is still used whenever testing has not been performed.
Physical Properties
Cleavage: {010} Perfect Color: White, Reddish white, Grayish white, Brownish white, Yellow. Density: 2.2 Diaphaneity: Transparent to subtranslucent Fracture: Brittle – Generally displayed by glasses and most non-metallic minerals. Hardness: 3-3.5 – Calcite-Copper Penny Luster: Vitreous – Pearly Streak: white
