Victoria’s volcano count rises

Geologists have discovered three previously unrecorded volcanoes in volcanically active southeast Australia.

The new Monash University research, published in the Australian Journal of Earth Sciences, gives a detailed picture of an area of volcanic centres already known to geologists in the region.

Covering an area of 19,000 square kilometres in Victoria and South Australia, with over 400 volcanoes, the Newer Volcanics Province (NVP) features the youngest volcanoes in Australia including Mount Schank and Mount Gambier.

Focusing on the Hamilton region, lead researcher Miss Julie Boyce from the School of Geosciences said the surprising discovery means additional volcanic centres may yet be discovered in the NVP.

“Victoria’s latest episode of volcanism began about eight million years ago, and has helped to shape the landscape. The volcanic deposits, including basalt, are among the youngest rocks in Victoria but most people know little about them,”Miss Boyce said.

“Though it’s been more than 5000 years since the last volcanic eruption in Australia, it’s important that we understand where, when and how these volcanoes erupted. The province is still active, so there may be future eruptions.”

The largest unrecorded volcano is a substantial maar-cone volcanic complex – a broad, low relief volcanic crater caused by an explosion when groundwater comes into contact with hot magma – identified 37 kilometres east of Hamilton.

Miss Boyce said the discoveries were made possible only by analysing a combination of satellite photographs, detailed NASA models of the topography of the area and the distribution of magnetic minerals in the rocks, alongside site visits to build a detailed picture of the Hamilton region of the NVP.

“Traditionally, volcanic sites are analysed by one or two of these techniques. This is the first time that this multifaceted approach has been applied to the NVP and potentially it could be used to study other volcanic provinces worldwide.”

The NVP is considered active, as carbon dioxide is released from the Earth’s mantle in several areas, where there is a large heat anomaly at depth. With an eruption frequency of one volcano every 10,800 years or less, future eruptions may yet occur.

It’s hoped that this multifaceted approach will lead to a better understanding of the distribution and nature of volcanism, allowing for more accurate hazard analysis and risk estimates for future eruptions.

New evidence for oceans of water deep in the Earth

Researchers from Northwestern University and the University of New Mexico report evidence for potentially oceans worth of water deep beneath the United States. Though not in the familiar liquid form — the ingredients for water are bound up in rock deep in the Earth’s mantle — the discovery may represent the planet’s largest water reservoir.

The presence of liquid water on the surface is what makes our “blue planet” habitable, and scientists have long been trying to figure out just how much water may be cycling between Earth’s surface and interior reservoirs through plate tectonics.

Northwestern geophysicist Steve Jacobsen and University of New Mexico seismologist Brandon Schmandt have found deep pockets of magma located about 400 miles beneath North America, a likely signature of the presence of water at these depths. The discovery suggests water from the Earth’s surface can be driven to such great depths by plate tectonics, eventually causing partial melting of the rocks found deep in the mantle.

The findings, to be published June 13 in the journal Science, will aid scientists in understanding how the Earth formed, what its current composition and inner workings are and how much water is trapped in mantle rock.

“Geological processes on the Earth’s surface, such as earthquakes or erupting volcanoes, are an expression of what is going on inside the Earth, out of our sight,” said Jacobsen, a co-author of the paper. “I think we are finally seeing evidence for a whole-Earth water cycle, which may help explain the vast amount of liquid water on the surface of our habitable planet. Scientists have been looking for this missing deep water for decades.”

Scientists have long speculated that water is trapped in a rocky layer of the Earth’s mantle located between the lower mantle and upper mantle, at depths between 250 miles and 410 miles. Jacobsen and Schmandt are the first to provide direct evidence that there may be water in this area of the mantle, known as the “transition zone,” on a regional scale. The region extends across most of the interior of the United States.

Schmandt, an assistant professor of geophysics at the University of New Mexico, uses seismic waves from earthquakes to investigate the structure of the deep crust and mantle. Jacobsen, an associate professor of Earth and planetary sciences at Northwestern’s Weinberg College of Arts and Sciences, uses observations in the laboratory to make predictions about geophysical processes occurring far beyond our direct observation.

The study combined Jacobsen’s lab experiments in which he studies mantle rock under the simulated high pressures of 400 miles below the Earth’s surface with Schmandt’s observations using vast amounts of seismic data from the USArray, a dense network of more than 2,000 seismometers across the United States.

Jacobsen’s and Schmandt’s findings converged to produce evidence that melting may occur about 400 miles deep in the Earth. H2O stored in mantle rocks, such as those containing the mineral ringwoodite, likely is the key to the process, the researchers said.

“Melting of rock at this depth is remarkable because most melting in the mantle occurs much shallower, in the upper 50 miles,” said Schmandt, a co-author of the paper. “If there is a substantial amount of H2O in the transition zone, then some melting should take place in areas where there is flow into the lower mantle, and that is consistent with what we found.”

If just one percent of the weight of mantle rock located in the transition zone is H2O, that would be equivalent to nearly three times the amount of water in our oceans, the researchers said.

This water is not in a form familiar to us — it is not liquid, ice or vapor. This fourth form is water trapped inside the molecular structure of the minerals in the mantle rock. The weight of 250 miles of solid rock creates such high pressure, along with temperatures above 2,000 degrees Fahrenheit, that a water molecule splits to form a hydroxyl radical (OH), which can be bound into a mineral’s crystal structure.

Schmandt and Jacobsen’s findings build on a discovery reported in March in the journal Nature in which scientists discovered a piece of the mineral ringwoodite inside a diamond brought up from a depth of 400 miles by a volcano in Brazil. That tiny piece of ringwoodite — the only sample in existence from within the Earth — contained a surprising amount of water bound in solid form in the mineral.

“Whether or not this unique sample is representative of the Earth’s interior composition is not known, however,” Jacobsen said. “Now we have found evidence for extensive melting beneath North America at the same depths corresponding to the dehydration of ringwoodite, which is exactly what has been happening in my experiments.”

For years, Jacobsen has been synthesizing ringwoodite, colored sapphire-like blue, in his Northwestern lab by reacting the green mineral olivine with water at high-pressure conditions. (The Earth’s upper mantle is rich in olivine.) He found that more than one percent of the weight of the ringwoodite’s crystal structure can consist of water — roughly the same amount of water as was found in the sample reported in the Nature paper.

“The ringwoodite is like a sponge, soaking up water,” Jacobsen said. “There is something very special about the crystal structure of ringwoodite that allows it to attract hydrogen and trap water. This mineral can contain a lot of water under conditions of the deep mantle.”

For the study reported in Science, Jacobsen subjected his synthesized ringwoodite to conditions around 400 miles below the Earth’s surface and found it forms small amounts of partial melt when pushed to these conditions. He detected the melt in experiments conducted at the Advanced Photon Source of Argonne National Laboratory and at the National Synchrotron Light Source of Brookhaven National Laboratory.

Jacobsen uses small gem diamonds as hard anvils to compress minerals to deep-Earth conditions. “Because the diamond windows are transparent, we can look into the high-pressure device and watch reactions occurring at conditions of the deep mantle,” he said. “We used intense beams of X-rays, electrons and infrared light to study the chemical reactions taking place in the diamond cell.”

Jacobsen’s findings produced the same evidence of partial melt, or magma, that Schmandt detected beneath North America using seismic waves. Because the deep mantle is beyond the direct observation of scientists, they use seismic waves — sound waves at different speeds — to image the interior of the Earth.

“Seismic data from the USArray are giving us a clearer picture than ever before of the Earth’s internal structure beneath North America,” Schmandt said. “The melting we see appears to be driven by subduction — the downwelling of mantle material from the surface.”

The melting the researchers have detected is called dehydration melting. Rocks in the transition zone can hold a lot of H2O, but rocks in the top of the lower mantle can hold almost none. The water contained within ringwoodite in the transition zone is forced out when it goes deeper (into the lower mantle) and forms a higher-pressure mineral called silicate perovskite, which cannot absorb the water. This causes the rock at the boundary between the transition zone and lower mantle to partially melt.

“When a rock with a lot of H2O moves from the transition zone to the lower mantle it needs to get rid of the H2O somehow, so it melts a little bit,” Schmandt said. “This is called dehydration melting.”

“Once the water is released, much of it may become trapped there in the transition zone,” Jacobsen added.

Just a little bit of melt, about one percent, is detectible with the new array of seismometers aimed at this region of the mantle because the melt slows the speed of seismic waves, Schmandt said.

Geologists confirm oxygen levels of ancient oceans

Assistant Professor Zunli Lu co-authored the study. -  Syracuse University News Services
Assistant Professor Zunli Lu co-authored the study. – Syracuse University News Services

Geologists in the College of Arts and Sciences have discovered a new way to study oxygen levels in the Earth’s oldest oceans.

Zunli Lu and Xiaoli Zhou, an assistant professor and Ph.D. student, respectively, in the Department of Earth Sciences, are part of an international team of researchers whose findings have been published by the journal Geology (Geological Society of America, 2014). Their research approach may have important implications for the study of marine ecology and global warming.

“More than 2.5 billion years ago, there was little to no oxygen in the oceans, as methane shrouded the Earth in a haze,” says Lu, a member of Syracuse University’s Low-Temperature Geochemistry Research Group. “Organisms practicing photosynthesis eventually started to overpower reducing chemical compounds [i.e., electron donors], and oxygen began building up in the atmosphere. This period has been called the Great Oxidation Event.”

Using a novel approach called iodine geochemistry, Lu, Zhou and their colleagues have confirmed the earliest appearance of dissolved oxygen in the ocean’s surface waters.

Central to their approach is iodate, a form of iodine that exists only in oxygenated waters. When iodate is detected in carbonate rocks in a marine setting, Lu and company are able to measure the elemental ratio of iodine to calcium. This measurement, known as a proxy for ocean chemistry, helps them figure out how much oxygen has dissolved in the water.

“Iodine geochemistry enables us to constrain oxygen levels in oceans that have produced calcium carbonate minerals and fossils,” says Lu, who developed the proxy. “What we’ve found in ancient rock reinforces the proxy’s reliability. Already, we’re using the proxy to better understand the consequences of ocean deoxygenation, due to rapid global warming.”

New study finds Antarctic Ice Sheet unstable at end of last ice age

This is one of many icebergs that sheared off the continent and ended up in the Scotia Sea. -  Photo courtesy of Michael Weber, University of Cologne
This is one of many icebergs that sheared off the continent and ended up in the Scotia Sea. – Photo courtesy of Michael Weber, University of Cologne

A new study has found that the Antarctic Ice Sheet began melting about 5,000 years earlier than previously thought coming out of the last ice age – and that shrinkage of the vast ice sheet accelerated during eight distinct episodes, causing rapid sea level rise.

The international study, funded in part by the National Science Foundation, is particularly important coming on the heels of recent studies that suggest destabilization of part of the West Antarctic Ice Sheet has begun.

Results of this latest study are being published this week in the journal Nature. It was conducted by researchers at University of Cologne, Oregon State University, the Alfred-Wegener-Institute, University of Hawaii at Manoa, University of Lapland, University of New South Wales, and University of Bonn.

The researchers examined two sediment cores from the Scotia Sea between Antarctica and South America that contained “iceberg-rafted debris” that had been scraped off Antarctica by moving ice and deposited via icebergs into the sea. As the icebergs melted, they dropped the minerals into the seafloor sediments, giving scientists a glimpse at the past behavior of the Antarctic Ice Sheet.

Periods of rapid increases in iceberg-rafted debris suggest that more icebergs were being released by the Antarctic Ice Sheet. The researchers discovered increased amounts of debris during eight separate episodes beginning as early as 20,000 years ago, and continuing until 9,000 years ago.

The melting of the Antarctic Ice Sheet wasn’t thought to have started, however, until 14,000 years ago.

“Conventional thinking based on past research is that the Antarctic Ice Sheet has been relatively stable since the last ice age, that it began to melt relatively late during the deglaciation process, and that its decline was slow and steady until it reached its present size,” said lead author Michael Weber, a scientist from the University of Cologne in Germany.

“The sediment record suggests a different pattern – one that is more episodic and suggests that parts of the ice sheet repeatedly became unstable during the last deglaciation,” Weber added.

The research also provides the first solid evidence that the Antarctic Ice Sheet contributed to what is known as meltwater pulse 1A, a period of very rapid sea level rise that began some 14,500 years ago, according to Peter Clark, an Oregon State University paleoclimatologist and co-author on the study.

The largest of the eight episodic pulses outlined in the new Nature study coincides with meltwater pulse 1A.

“During that time, the sea level on a global basis rose about 50 feet in just 350 years – or about 20 times faster than sea level rise over the last century,” noted Clark, a professor in Oregon State’s College of Earth, Ocean, and Atmospheric Sciences. “We don’t yet know what triggered these eight episodes or pulses, but it appears that once the melting of the ice sheet began it was amplified by physical processes.”

The researchers suspect that a feedback mechanism may have accelerated the melting, possibly by changing ocean circulation that brought warmer water to the Antarctic subsurface, according to co-author Axel Timmermann, a climate researcher at the University of Hawaii at Manoa.

“This positive feedback is a perfect recipe for rapid sea level rise,” Timmermann said.

Some 9,000 years ago, the episodic pulses of melting stopped, the researchers say.

“Just as we are unsure of what triggered these eight pulses,” Clark said, “we don’t know why they stopped. Perhaps the sheet ran out of ice that was vulnerable to the physical changes that were taking place. However, our new results suggest that the Antarctic Ice Sheet is more unstable than previously considered.”

Today, the annual calving of icebergs from Antarctic represents more than half of the annual loss of mass of the Antarctic Ice Sheet – an estimated 1,300 to 2,000 gigatons (a gigaton is a billion tons). Some of these giant icebergs are longer than 18 kilometers.

How productive are the ore factories in the deep sea?

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. The study appears in the current issue of the world-renowned scientific journal “Nature“.

In general, it is well known that seawater penetrates into the 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”.

Geologists prove early Tibetan Plateau was larger than previously thought

This is Syracuse University professor Gregory Hoke. -  Syracuse University
This is Syracuse University professor Gregory Hoke. – Syracuse University

Earth scientists in Syracuse University’s College of Arts and Sciences have determined that the Tibetan Plateau-the world’s largest, highest, and flattest plateau-had a larger initial extent than previously documented.

Their discovery is the subject of an article in the journal Earth and Planetary Science Letters (Elsevier, 2014).

Gregory Hoke, assistant professor of Earth sciences, and Gregory Wissink, a Ph.D. student in his lab, have co-authored the article with Jing Liu-Zeng, director of the Division of Neotectonics and Geomorphology at the Institute for Geology, part of the China Earthquake Administration; Michael Hren, assistant professor of chemistry at the University of Connecticut; and Carmala Garzione, professor and chair of Earth and environmental sciences at the University of Rochester.

“We’ve determined the elevation history of the southeast margin of the Tibetan Plateau,” says Hoke, who specializes in the interplay between the Earth’s tectonic and surface processes. “By the Eocene epoch (approximately 40 million years ago), the southern part of the plateau extended some 600 miles more to the east than previously documented. This discovery upends a popular model for plateau formation.”

Known as the “Roof of the World,” the Tibetan Plateau covers more than 970,000 square miles in Asia and India and reaches heights of over 15,000 feet. The plateau also contains a host of natural resources, including large mineral deposits and tens of thousands of glaciers, and is the headwaters of many major drainage basins.

Hoke says he was attracted to the topography of the plateau’s southeast margin because it presented an opportunity to use information from minerals formed at the Earth’s surface to infer what happened below them in the crust.

“The tectonic and topographic evolution of the southeast margin has been the subject of considerable controversy,” he says. “Our study provides the first quantitative estimate of the past elevation of the eastern portions of the plateau.”

Historically, geologists have thought that lower crustal flow- a process by which hot, ductile rock material flows from high- to low-pressure zones-helped elevate parts of the plateau about 20 million years ago. (This uplift model has also been used to explain watershed reorganization among some of the world’s largest rivers, including the Yangtze in China.)

But years of studying rock and water samples from the plateau have led Hoke to rethink the area’s history. For starters, his data indicates that the plateau has been at or near its present elevation since the Eocene epoch. Moreover, surface uplift in the southernmost part of the plateau-in and around southern China and northern Vietnam-has been historically small.

“Surface uplift, caused by lower crustal flow, doesn’t explain the evolution of regional river networks,” says Hoke, referring to the process by which a river drainage system is diverted, or captured, from its own bed into that of a neighboring bed. “Our study suggests that river capture and drainage reorganization must have been the result of a slip on the major faults bounding the southeast plateau margin.”

Hoke’s discovery not only makes the plateau larger than previously thought, but also suggests that some of the topography is millions of years younger.

“Our data provides the first direct documentation of the magnitude and geographic extent of elevation change on the southeast margin of the Tibetan Plateau, tens of millions years ago,” Hoke adds. “Constraining the age, spatial extent, and magnitude of ancient topography has a profound effect on how we understand the construction of mountain ranges and high plateaus, such as those in Tibet and the Altiplano region in Bolivia.”

Most of the sand in Alberta’s oilsands came from eastern North America, study shows

Christine Benyon is completing her Master's degree in Geoscience in the Faculty of Science. -  Riley Brandt, University of Calgary
Christine Benyon is completing her Master’s degree in Geoscience in the Faculty of Science. – Riley Brandt, University of Calgary

They’re called the Alberta oilsands but most of the sand actually came from the Appalachian region on the eastern side of the North American continent, a new University of Calgary-led study shows.

The oilsands also include sand from the Canadian Shield in northern and east-central Canada and from the Canadian Rockies in western Canada, the study says.

This study is the first to determine the age of individual sediment grains in the oilsands and assess their origin.

“The oilsands are looked at as a Western asset,” says study lead author Christine Benyon, who is just completing her Master’s degree in Geoscience in the Faculty of Science.

“But we wouldn’t have oilsands without the sand, and some of that sand owes its origin to the Appalachians and other parts of Canada.”

The research, which also involved study sponsor Nexen Energy ULC and the University of Arizona LaserChron Center, was published last week in the Journal of Sedimentary Research.

The findings contribute to geologists’ fundamental understanding of the oilsands.

They also help oilsands companies better understand the stratigraphy, or layers, of sand and the ancient valleys where sediment was deposited, “and that could lead to better production techniques,” Benyon says.

To determine the origin of the sand, the researchers used a relatively new technique called “detrital zircon uranium-lead geochronology.”

They used a mass spectrometer to date the age of tiny and extremely durable crystallized minerals called zircons that are present in the oilsands.

“The age of those zircons tells us how long since they crystallized. And knowing that, we can infer their place of origin,” Benyon explains.

Researchers dated the zircons in nine core samples from three wells drilled into the oilsands’ McMurray Formation.

Lowermost deposits contained zircons ranging from 1,800 to 2,800 million years old. These zircons, and thereby the associated sand, originally came from the Canadian Shield, which contains rocks of those ages, Benyon says.

Most of the oilsands’ sediment contains zircons that range from 300 to 1,200 million years old – the same zircon signature found in Appalachian sources in eastern North America.

The uppermost oilsands contain zircons that are less than 250 million years old, indicating the Canadian Rockies as their most likely place of origin.

So how did so much of the sand, deposited during the Cretaceous geological time period about 145 to 66 million years ago (before the sand was emplaced with oil), get to Alberta from the other side of the continent?

No one knows for sure, but Benyon and her co-authors propose three theories, all involving sediment transported by a continental-sized river system:

  • The massive river system transported the sediment directly from eastern North America to the present-day oilsands region during the Cretaceous;

  • The river system transported the sediment from eastern North America during an earlier geological time period and deposited it in the southwestern United States; later, in the Cretaceous, rivers flowing northward ‘recycled’ the sediment and deposited it in western Canada;
  • An older (perhaps Jurassic or Permian) river system coming from the Appalachians deposited the sediment in western Canada; later, during the Cretaceous, the sediment was eroded by smaller rivers and re-deposited in northeastern Alberta.

No matter how and when the sand got to the present location of the oilsands, “the study tells us that the Appalachians were an important source of sediment in the geological history of North America,” Benyon says.

Innovative handheld mineral analyzer — ‘the first of its kind’

This is Dr. Graeme Hansford of the University of Leicester Space Research Centre. -  University of Leicester
This is Dr. Graeme Hansford of the University of Leicester Space Research Centre. – University of Leicester

Dr Graeme Hansford from the University of Leicester’s Space Research Centre (SRC) has recently started a collaborative project with Bruker Elemental to develop a handheld mineral analyser for mining applications – the first of its kind.

The analyser will allow rapid mineral identification and quantification in the field through a combination of X-ray diffraction (XRD) and X-ray fluorescence (XRF). The novel X-ray diffraction method was invented at the University of Leicester and has been developed at the Space Research Centre. The addition of XRD capability represents an evolution of current handheld XRF instruments which sell 1000s of units each year globally.

The handheld instrument is expected to weigh just 1.5 kg, will be capable of analysing mining samples for mineral content within 1 – 2 minutes, and requires no sample preparation. This would be a world first. The analyser is unique due to the insensitivity of the technique to the shape of the sample, which enables the direct analysis of samples without any form of preparation – something currently inconceivable using conventional XRD equipment.

Dr Hansford said: “It’s very fulfilling for me to see the development of this novel XRD technique from initial conception through theoretical calculations and modelling to experimental demonstration.

“The next step is to develop the commercial potential and I’m very excited to be working with Bruker Elemental on the development of a handheld instrument.”

Bruker Elemental is a global leader in handheld XRF instrumentation, with the mining sector a key customer. Bruker therefore brings essential commercial expertise to the project. The two partners have complementary expertise, and are uniquely placed to successfully deliver this knowledge exchange project.

Alexander Seyfarth, senior product manager at Bruker Elemental, said: “Bruker is excited to be involved in this project as it will bring new measurement capabilities to our handheld equipment. In many cases this system will provide information on the crystallography of the sample in addition to the elemental analysis.”

Dr Hansford originally conceived of the XRD technique in early 2010, when trying to work out how to apply XRD for space applications – for example on the surface of Mars or an asteroid – without the need for any sample preparation.

The next stage of the project will focus on developing and testing the methodology using samples which are representative of real-world problems encountered in mining, such as determining the relative amounts of iron oxide minerals in ore samples. In the second part of the project, a prototype handheld device will be developed at the SRC in conjunction with Bruker to demonstrate efficacy of the technology in the field. A key advantage is that the hardware requirements of the technique are very similar to existing handheld XRF devices, facilitating both rapid development and customer acceptance.

Diamonds in Earth’s oldest zircons are nothing but laboratory contamination

This image explains how synthetic diamond can be distinguished from natural diamond. -  Dobrzhinetskaya Lab, UC Riverside.
This image explains how synthetic diamond can be distinguished from natural diamond. – Dobrzhinetskaya Lab, UC Riverside.

As is well known, the Earth is about 4.6 billion years old. No rocks exist, however, that are older than about 3.8 billion years. A sedimentary rock section in the Jack Hills of western Australia, more than 3 billion years old, contains within it zircons that were eroded from rocks as old as about 4.3 billion years, making these zircons, called Jack Hills zircons, the oldest recorded geological material on the planet.

In 2007 and 2008, two research papers reported in the journal Nature that a suite of zircons from the Jack Hills included diamonds, requiring a radical revision of early Earth history. The papers posited that the diamonds formed, somehow, before the oldest zircons – that is, before 4.3 billion years ago – and then were recycled repeatedly over a period of 1.2 billion years during which they were periodically incorporated into the zircons by an unidentified process.

Now a team of three researchers, two of whom are at the University of California, Riverside, has discovered using electron microscopy that the diamonds in question are not diamonds at all but broken fragments of a diamond-polishing compound that got embedded when the zircon specimen was prepared for analysis by the authors of the Nature papers.

“The diamonds are not indigenous to the zircons,” said Harry Green, a research geophysicist and a distinguished professor of the Graduate Division at UC Riverside, who was involved in the research. “They are contamination. This, combined with the lack of diamonds in any other samples of Jack Hills zircons, strongly suggests that there are no indigenous diamonds in the Jack Hills zircons.”

Study results appear online this week in the journal Earth and Planetary Science Letters.

“It occurred to us that a long-term history of diamond recycling with intermittent trapping into zircons would likely leave some sort of microstructural record at the interface between the diamonds and zircon,” said Larissa Dobrzhinetskaya, a professional researcher in the Department of Earth Sciences at UCR and the first author of the research paper. “We reasoned that high-resolution electron microscopy of the material should be able to distinguish whether the diamonds are indeed what they have been believed to be.”

Using an intensive search with high-resolution secondary-electron imaging and transmission electron microscopy, the research team confirmed the presence of diamonds in the Jack Hills zircon samples they examined but could readily identify them as broken fragments of diamond paste that the original authors had used to polish the zircons for examination. They also observed quartz, graphite, apatite, rutile, iron oxides, feldspars and other low-pressure minerals commonly included into zircon in granitic rocks.

“In other words, they are contamination from polishing with diamond paste that was mechanically injected into silicate inclusions during polishing” Green said.

The research was supported by a grant from the National Science Foundation.

Green and Dobrzhinetskaya were joined in the research by Richard Wirth at the Helmholtz Centre Potsdam, Germany.

Dobrzhinetskaya and Green planned the research project; Dobrzhinetskaya led the project; she and Wirth did the electron microscopy.

Supervolcanoes discovered in Utah

Brigham Young University geologists found evidence of some of the largest volcanic eruptions in earth’s history right in their own backyard.

These supervolcanoes aren’t active today, but 30 million years ago more than 5,500 cubic kilometers of magma erupted during a one-week period near a place called Wah Wah Springs. By comparison, this eruption was about 5,000 times larger than the 1980 Mount St. Helens eruption.

“In southern Utah, deposits from this single eruption are 13,000 feet thick,” said Eric Christiansen, the lead author for the BYU study. “Imagine the devastation – it would have been catastrophic to anything living within hundreds of miles.”

Dinosaurs were already extinct during this time period, but what many people don’t know is that 25-30 million years ago, North America was home to rhinos, camels, tortoises and even palm trees. Evidence of the ancient flora and fauna was preserved by volcanic deposits.

The research group, headed by Christiansen and professor emeritus Myron Best, measured the thickness of the pyroclastic flow deposits. They used radiometric dating, X-ray fluorescence spectrometry, and chemical analysis of the minerals to verify that the volcanic ash was all from the same ancient super-eruption.

They found that the Wah Wah Springs eruption buried a vast region extending from central Utah to central Nevada and from Fillmore on the north to Cedar City on the south. They even found traces of ash as far away as Nebraska.

But this wasn’t an isolated event; the BYU geologists found evidence of fifteen super-eruptions and twenty large calderas. The scientific journal Geosphere recently published two of their papers detailing the discoveries.

Despite their enormous size, the supervolcanoes have been hidden in plain sight for millions of years.

“The ravages of erosion and later deformation have largely erased them from the landscape, but our careful work has revealed their details,” said Christiansen. “The sheer magnitude of this required years of work and involvement of dozens of students in putting this story together.”

Supervolcanoes are different from the more familiar “straddle” volcanoes – like Mount St. Helens – because they aren’t as obvious to the naked eye and they affect enormous areas.

“Supervolcanoes as we’ve seen are some of earth’s largest volcanic edifices, and yet they don’t stand as high cones,” said Christiansen. “At the heart of a supervolcano instead, is a large collapse.”

Those collapses in supervolcanoes occur with the eruption and form enormous holes in the ground in plateaus, known as calderas.

Not many people know that there are still active supervolcanoes today. Yellowstone National Park in Wyoming is home to one roughly the same size as the Wah Wah Springs caldera, which was about 25 miles across and 3 miles deep when it first formed.