Category Archives: Geoscience

Sn-W-Critical Metals & Associated Magmatic Systems

Southern Atherton Tablelands. Credit: Cairns Tours

An EGRU conference with a session in honour of Dr Roger Taylor

24 – 28 June 2019

Tinaroo Lake Resort

Tinaroo, Atherton Tablelands, tropical north Queensland, Australia

The conference will address advances and breakthroughs in understanding the setting, genesis and  characteristics of magmatic systems  related to Sn-W-Critical Metal mineralisation, including Rare Metal Pegmatites.   The program will feature presentations from world-class researchers in the field, including:

  • Rolf Romer (GFZ, Potsdam, Germany)
  • Jingwen Mao (Chinese Academy of Geological Sciences, Beijing, China)
  • Shao-Yong Jiang (China University of Geosciences, Wuhan, China)
  • Dr Phillip Blevin (Mineral Systems, Geological Survey of NSW, Maitland, Australia)
  • Zhaoshan Chang (Colorado School of Mines, Denver, USA)
  • David Cooke (CODES, Hobart, University of Tasmania)
  • Dr Peter Pollard (Pollard Geological Services, Brisbane, Australia)
  • Dr Yanbo Cheng (EGRU, James Cook University, Townsville, Australia)

See you at the event –  should be well worth attending.  If anyone is interested in a little pre-confernece rainforest hiking for 2-3 days before the event –  message me.

Sn-W-Critical Metals Conference FF 2018-08-21 LR

Dickinsonia was an animal!

A recent paper in Science authored Ilya Bobrovskiy, Janet Hope and colleagues from ANU, the Russian Academy and European institutions has remarkably (and convincingly) discovered molecules of fat in Dickinsonia, a marine genus of the Ediacaran biota.

Dikinsonia samples from Quantitative study of developmental biology confirms Dickinsonia as a metazoan , Renee S. Hoekzema, Martin D. Brasier, Frances S. Dunn, Alexander G. Liu proceedings of The Royal Society. Published 13 September 2017.DOI: 10.1098/rspb.2017.1348

This has confirmed that the 558 million year old Dickinsonia is the earliest animal in the geological record and maybe a presursor to –  you!

Organically preserved Dickinsonia fossil from the White Sea area of Russia. A Dickinsonia fossilILYA BOBROVSKIY / AUSTRALIAN NATIONAL UNIVERSITY

The strange creature called Dickinsonia, which grew up to 1.4 metres in length and was oval shaped with rib-like segments running along its body, was part of the Ediacara Biota that lived on Earth 20 million years prior to the ‘Cambrian explosion’ of modern animal life.  The Ediacara biota are a diverse assemblage of macroscopic body forms that appear in the sedimentary rock record between 570 million and 541 million years ago. First recognized in Namibia and Australia, these remarkable organisms have since been found in Russia, China, Canada, Great Britain, and other regions. Although they immediately preceded the rapid appearance and diversification of animals in the Cambrian (541 million to 485 million years ago), their position within the tree of life has long been a puzzle. Some Ediacaran fossils appear segmented, but most lack obvious characters such as appendages, a mouth, or a gut that might link them to animal clades.

Dickinsonia costata (~7.7 cm long), SAM P13750/P40679 (South Australian Museum, Adelaide, Australia)

Prior to this study  Dikinsonia affinities were unknown and while its  mode of growth is consistent with a bilaterian affinity some thought that it belong to to the fungi, or even an “extinct kingdom”

Dickinsonia costata (centimeter scale), YPM 35467 (Yale University’s Peabody Museum, New Haven, Connecticut, USA)

Bobrovskiy et al. conducted an analysis using lipid biomarkers obtained from Dickinsonia fossils and found that the fossils contained almost exclusively cholesteroids, a marker found only in animals.  Thus, Dickinsoniawere basal animals. This supports the idea that the Ediacaran biota may have been a precursor to the explosion of animal forms later observed in the Cambrian, about 500 million years ago.

Obtaining evidence of cholesteroids first involved finding exceptionally well preserved fossils.  The Dikinsonia fossils used in this study came from a narrow strata in the remote White Sea are of Russia.

Lead senior researcher Associate Professor Jochen Brocks said the ‘Cambrian explosion’ was when complex  and other macroscopic organisms—such as molluscs, worms, arthropods and sponges—began to dominate the fossil record.

“The fossil fat molecules that we’ve found prove that animals were large and abundant 558 million years ago, millions of years earlier than previously thought,” said Associate Professor Jochen Brocks from the ANU Research School of Earth Sciences.

“Scientists have been fighting for more than 75 years over what Dickinsonia and other bizarre fossils of the Edicaran Biota were: giant single-celled amoeba, lichen, failed experiments of evolution or the earliest animals on Earth. The fossil fat now confirms Dickinsonia as the oldest known animal fossil, solving a decades-old mystery that has been the Holy Grail of palaeontology.”

Abstract

The enigmatic Ediacara biota (571 million to 541 million years ago) represents the first macroscopic complex organisms in the geological record and may hold the key to our understanding of the origin of animals. Ediacaran macrofossils are as “strange as life on another planet” and have evaded taxonomic classification, with interpretations ranging from marine animals or giant single-celled protists to terrestrial lichens. Here, we show that lipid biomarkers extracted from organically preserved Ediacaran macrofossils unambiguously clarify their phylogeny. Dickinsonia and its relatives solely produced cholesteroids, a hallmark of animals. Our results make these iconic members of the Ediacara biota the oldest confirmed macroscopic animals in the rock record, indicating that the appearance of the Ediacara biota was indeed a prelude to the Cambrian explosion of animal life.

Read the Paper Here

 

Free Carried Interests in Mining Projects, States Need to Rethink the Strategy

Natural Resource Governance Institute has issued a report on revenues received from listed mining companies in Ghana.  As many who have done the cashflow analysis have long known that a free carried interest, funded out of cashflow is a less than effective tool for garnering rent from resource projects. Projects can often take many years to repay capital and if this period corresponds with low or stagnant commodity prices then dividend payments may be low.  In effect the state is fully exposed to commodity price and operational risks.  A better solution is a competitive royalty, fee and taxation environment which is adequately regulated. 

One of the issues with a carried interest is that this often involves representation on the board of the operating entity and as such creates immediate conflicts of interest for directors and heated domestic competition for these positions.   That said, there are often political arguments for a carried interest, arguments about national interest.  In addition it has been argued that being represented on the board of the operating entity allows governments to “keep an eye on” the operator.  A better solution is robust oversight by a suitably trained and funded Department of Mines.

ghana-gold-mining-revenue-analysis-company-disclosures

In Ghana the majority of international mining companies, including Asanko Gold, Golden Star Resources, Endeavour Mining, Kinross Gold, Perseus Mining and Xtra-Gold Resources, have disclosed payments-to-governments reports under the Extractive Sector Transparency Measures Act (ESTMA) in Canada. In addition Gold Fields, AngloGold Ashanti and Newmont Mining have made voluntary disclosures regarding the payments they make to the Ghanaian government.

Data were sourced from companies complying with the Canadian, Extractive Sector Transparency Measures Act (ESTMA).

In 2017 nearly three quarters of the payments to Ghanaian government entities by ESTMA companies in the gold sector arose from royalties, with five companies paying a total of USD 57 million. A further 22 percent of the payments from these ESTMA companies were in the form of corporate income tax. While six operating companies paid royalties in 2017, only two, Kinross Gold Corporation and Endeavour Mining paid corporate taxes.

2017 gold mining payments to governments by payment type from ESTMA companies (USD in millions)

Ghana’s Vice President Mahamudu Bawumia has questioned the utility of the government’s 10 percent equity interest in mining operations, stating at the IMF’s Regional Economic Outlook for sub-Saharan Africa, that the lack of revenue generated from the government’s equity share was because “many of the mining companies say they are not making profits to pay dividends but they keep mining, notwithstanding the fact that they are unprofitable.”3

The government of Ghana holds these shares and the non-tax revenue unit of the Ministry of Finance collects the revenues. The government is provided this equity interest without having to make financial contributions to the development or operations of the project. The government has equity share interests in every gold mining operation in the country bar those owned by Newmont Mining or AngloGold Ashanti following the signing of updated mining development agreements. In the case of AngloGold Ashanti, the government has a stake of 1.55 percent in the global company AngloGold Ashanti Limited.

The NRGI report concludes that “the payments-to-governments disclosures made by international mining companies operating in the country suggest that if revenue generation is the primary purpose of this state equity participation, then the government may want to reconsider this approach”.  This has been evident to many in the industry for a very long time.  

 

Geological Belts, Plate Boundaries, and Mineral Deposits in Myanmar

Geological Belts, Plate Boundaries and Mineral Deposits in Myanmar

 

Just received the above titled book from Elsevier for review.  I had the great pleasure of spending some time in the field in Myanmar with Andrew Mitchell in 2017 and this important contribution by him is a remarkable testament to  his life’s work.  He has enormous knowledge of the geology and mineral deposits of Myanmar and that is obvious in this text.

I will be undertaking a chapter-by-chapter review of the text over the coming 6 weeks or so and posting here.  A quick review:  The text is well written, beautifully presented and the numerous maps provide new geological insights.  As a largely personal contribution this is an unusual work and will be important to minerals industry professionals and researchers and importantly, geoscience educators in Myanmar.

Geological Belts, Plate Boundaries, and Mineral Deposits in Myanmar, Mitchell, A., Elsevier, pp 524, ISBN 978-0-12-803382-1 , https://doi.org/10.1016/C2014-0-00978-1, 2018

Description

Geological Belts, Plate Boundaries and Mineral Deposits in Myanmar arms readers with a comprehensive overview of the geography, geology, mineral potential and tectonic plate activity of Myanmar. The book focuses on the nature and history of the structural belts and terranes of Myanmar, with particular emphasis on the mineral deposits and their relationship to stratigraphy and structure. The country has a long history of plate tectonic activity, and the most recent plate movements relate to the northward movement of the India plate as it collides with Asia. Both of these are responsible for the earthquakes which frequently occur, making the country a geologically dynamic region. Additionally, Myanmar is rich in mineral and petroleum potential and the site of some of Southeast Asia’s largest faults. However, many geoscientists are only recently becoming familiar with Myanmar due to previous political issues. Some of these barriers have been removed and there is emerging international interest in the geology and mineral deposits of Myanmar. This book collates this essential information in one complete resource. Geological Belts, Plate Boundaries and Mineral Deposits in Myanmar is an essential reference for economic geologists, mineralogists, petroleum geologists, and seismologists, as well as geoscience instructors and students taking related coursework.

The Big Bonanza – “the richest mineral discovery in world history”

To the Daily Alta California, it was “the great discovery of the age”.  After emerging from the underground at the California Mine on the Comstock Lode Dan de Quille called it “the richest mineral discovery in the world’s history” and he named it The Big Bonanza.    In a field of exceedingly high-grade mineralization the Big bonanza would generate immense wealth.

Virginia city circa 1870

“Not a pebble in the crosscut was worth less than US$600 per ton and no small sample could be reasonably assayed for fear of grabbing a sulphuret nodule that would run the chunk into the thousands of dollars a ton.”  Bear in mind these are 1870 dollars, likely worth US$20,000 per tonnes in today’s dollars.

“Sometime in the first half of 1875, as cross cuts on the 1,500 foot level reveled that the ore body did indeed span the entire length of the California mine, John Mackay must have realised that The Big bonanza would make him one of the richest men in the world.”

Virginia city circa 1870
Pyrargyrite silver ore from the Comstock Lode, Storey Co., Nevada, U.S.
Chris Ralph/Nevada Outback Gems

The Bonanza King is a well researched history of the Comstock Lode and characters involved.   The book underlines the importance and occasional reward for focused hard work in the industry.   Strongly recommended for mining folks.

Pyrargyrite is a sulfosalt mineral consisting of silver sulfantimonide, Ag3SbS3. Known also as dark red silver ore or ruby silver, it is an important source of the metal.

Additional Reading

Bonanza Ores of the Comstock Lode, Viginia city, Nevada, Economic Geology, 1922

Review in the WSJ by Patrick Cooke

Crouch, Gregory. The Bonanza King: John Mackay and the Battle over the Greatest Riches in the American West.   

Climate Change Public Death Spiral

Climate Change Has Run Its Course

Stephen F. Hayward

By Steven F. Hayward

Steven F. Hayward, is currently the Thomas Smith Distinguished Fellow at the John M. Ashbrook Center at Ashland University, where he directs the Ashbrook Center’s new program in political economy. For the last decade he was the F.K. Weyerhaeuser Fellow in Law and Economics at the American Enterprise Institute in Washington, D.C., and a Senior Fellow at the Pacific Research Institute in San Francisco.

Published: Wall Street Journal, Jun 5th, 2018

Climate change is over. No, I’m not saying the climate will not change in the fu­ture, or that human influ­ence on the climate is negli­gible. I mean simply that climate change is no longer a pre-eminent policy issue. All that remains is boilerplate rhetoric from the political class, frivolous nuisance lawsuits, and bureaucratic mandates on behalf of special-interest renewable-energy rent seekers.
The End is Nigh

Judged by deeds rather than words, most national governments are backing away from forced-marched decarbonization. You can date the arc of climate change as a policy priority from 1988, when highly publicized congressional hear­ings first elevated the issue, to 2018. President Trump’s ostentatious with­drawal from the Paris Agreement merely ratified a trend long becom­ing evident.

A good indicator of why climate change as an issue is over can be found early in the text of the Paris Agreement. The “nonbinding” pact declares that climate action must in­clude concern for “gender equality, empowerment of women, and inter-generational equity” as well as “the importance for some of the concept of ‘climate justice.’ ” Another is Sarah Myhre’s address at the most recent meeting of the American Geophysical Union, in which she proclaimed that climate change cannot fully be ad­dressed without also grappling with the misogyny and social injustice that have perpetuated the problem for decades.

The descent of climate change into the abyss of social justice identity politics represents the last gasp of a cause that has lost its vitality. Climate alarm is like a car alarm—a blaring noise people are tuning out.

This outcome was predictable.

Political scientist Anthony Downs de­scribed the downward trajectory of many political movements in an arti­cle for the Public Interest, “Up and Down With Ecology: The ‘Issue-Attention” published in 1972, long before the climate-change campaign began. Observing the movements that had arisen to address issues like crime, poverty and even the U.S.-So­viet space race, Mr. Downs discerned a five-stage cycle through which po­litical issues pass regularly.

The first stage involves groups of experts and activists calling attention to a public problem, which leads quickly to the second stage, wherein the alarmed media and political class discover the issue. The second stage typically includes a large amount of euphoric enthusiasm—you might call it the “dopamine” stage—as activists conceive the issue in terms of global peril and salvation. This tendency ex­plains the fanaticism with which di­vinity-school dropouts Al Gore and Jerry Brown have warned of climate change.
Then comes the third stage: the hinge. As Mr. Downs explains, there soon comes “a gradually spreading re­alization that the cost of ‘solving’ the problem is very high indeed.” That’s where we’ve been since the United Na­tions’ traveling climate circus commit­ted itself to the fanatical mission of massive near-term reductions in fossil fuel consumption, codified in unrealis­tic proposals like the Kyoto Protocol. This third stage, Mt Downs continues, “becomes almost imperceptibly trans­formed into the fourth stage: a grad­ual decline in the intensity of public interest in the problem.”

While opinion surveys find that roughly half of Americans regard climate change as a problem, the is­sue has never achieved high salience among the public, despite the drum­beat of alarm from the climate cam­paign. Americans have consistently ranked climate change the 19th or 20th of 20 leading issues on the an­nual Pew Research Center poll, while Gallup’s yearly survey of envi­ronmental issues typically ranks cli­mate change far behind air and wa­ter pollution.

“In the final stage,” Mr. Downs concludes, “an issue that has been re­placed at the center of public concern moves into a prolonged limbo—a twi­light realm of lesser attention or spasmodic recurrences of interest.” Mr. Downs predicted correctly that environmental issues would suffer this decline, because solving such is­sues involves painful trade-offs that committed climate activists would rather not make.

A case in point is climate cam­paigners’ push for clean energy, whereas they write off nuclear power because it doesn’t fit their green utopian vision. A new study of climate-related philanthropy by Mat­thew Nisbet found that of the $556.7 million green-leaning foundations spent from 2011-15, “not a single grant supported work on promoting or reducing the cost of nuclear en­ergy.” The major emphasis of green giving was “devoted to mobilizing public opinion and to opposing the fossil fuel industry.”

Scientists who are genuinely wor­ried about the potential for cata­strophic climate change ought to be the most outraged at how the left po­liticized the issue and how the inter­national policy community narrowed the range of acceptable responses. Treating climate change as a planet-scale problem that could be solved only by an international regulatory scheme transformed the issue into a political creed for committed believ­ers. Causes that live by politics, die by politics.

Source Research:  

Detailed Lithospheric Magnetics – 250 Metre Resolution

ESA has just released the most detail magnetic data on the lithosphere from its Swarm three satellite constellation.  Launched on 22 November 2013, Swarm is the fourth in a series of pioneering Earth Explorer research missions, following on from GOCE, SMOS and CryoSat. Is also ESA’s first constellation of satellites to advance our understanding of how Earth works.

This is the most detailed map ever of the tiny magnetic signals generated by Earth’s lithosphere. The map, a video of which is seen here.  The data is being used to understand more about Earth’s geological history, is thanks to four years’ of measurements from ESA’s trio of Swarm satellites, historical data from the German CHAMP satellite and observations from ships and aircraft.

Erwan Thebault from the University of Nantes in France said, “This is the highest resolution model of the lithospheric magnetic field ever produced.  “With a scale of 250 km, we can see structures in the crust like never before. And, we have gained even finer detail in some parts of the crust, such as beneath Australia, where measurements from aircraft have mapped at resolution of 50 km.

“This combined use of satellite and near-surface measurements gives us a new understanding of the crust beneath our feet, and will be of enormous value to science.”

Map of field vertical component Z, at the Earth’s surface from the LCS-1 model for spherical harmonic degrees n-16-185. Green lines are isochrones.

Most of Earth’s magnetic field is generated deep within the outer core by an ocean of superheated, swirling liquid iron, but there are also much weaker sources of magnetism. The Swarm constellation has been used to yield some discoveries about these more elusive signals, such as that from Earth’s lithosphere. A small fraction of the magnetic field comes from magnetised rocks in the upper lithosphere, which includes Earth’s rigid crust and upper mantle. This lithospheric magnetic field is very weak and therefore difficult to detect from space. As new oceanic crust is created through volcanic activity, iron-rich minerals in the upwelling magma are oriented to magnetic north at the time and solidified as the magma cools. Since magnetic poles flip back and forth over time, the solidified magma due to mantle upwelling at mid-oceanic ridges forms magnetic ‘stripes’ on the seafloor which provide a record of Earth’s magnetic history. These magnetic imprints on the ocean floor can be used as a sort of time machine, allowing past field changes to be reconstructed and showing the movement of tectonic plates from hundreds of million years ago until the present day.

More: 

ESA Swarm Overview

Swarm Press Release

 

Milin Kamak intermediate sulfidation epithermal Au-Ag deposit in Western Srednogorie, Bulgaria

Here is a brief paper, by Ralica Sabeva Vassilka Mladenova and Aberra Mogessie on the gold deposits around the small western Bulgarian town of Breznik.  I acquired this project for Euromax Resources Limited back in 2003 and we explored this until my departure in 2010.  A rather nice intermediate sulphidation gold deposit which has now had the necessary fluid inclusion and sulphur isotope work conducted by Bulgarian and Austrian researchers.

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John C. Menzies and Greg Hall at Breznik in beautiful western Bulgaria

Our intention while I was CEO was to devleop this deposit using adits and an internal winze.  .

Pillow Lavas of Late Cretaceous Age, west of the town of Breznik, Bulgaria

Highlights

  • Situated in the Late Cretaceous 80-100km wide Apuseni-Banat-Timok-Srednogorie (ABTS) magmatic and metallogenic belt;
  • The deposit is hosted by altered trachybasalt to andesitic trachybasalt volcanic and volcanoclastic rocks;
  • 2.4 Mt at 5.91 g/t Au and of 26.78 g/t Ag, the probable reserves and resources are 13.1 tonnes of gold and 59.5 tonnes of silver;
  • Strike of 400-1000 metres and widths of cms up to 15 metres;
  • Temperature of formation ~238 to 273°C, salinity of 3.7-6.6% and  δ34S average of 1.350/00 suggestive of a magmatic sulphur source;
  • Fluid evolution from a low sulphidation through later intermediate (precious metals) stage.
Simplified geological map of Western Srednogorie zone in Bulgaria with the main paleovolcanic centres (after Dabovski et al. (2009) modified by Velev et al. (2012)). (B) Simplified geological map of Milin Kamak area.

Abstract

The Milin Kamak gold-silver deposit is located in Western Srednogorie zone, 50 km west of Sofia, Bulgaria. This zone belongs to the Late Cretaceous Apuseni-Banat-Timok-Srednogorie magmatic and metallogenic belt. The deposit is hosted by altered trachybasalt to andesitic trachybasalt volcanic and volcanoclastic rocks with Upper Cretaceous age, which are considered to be products of the Breznik paleovolcano. Milin Kamak is the first gold-silver intermediate sulfidation type epithermal deposit recognized in Srednogorie zone in Bulgaria. It consists of eight ore zones with lengths ranging from 400 to 1000 m, widths from several cm to 3–4 m, rarely to 10–15 m, an average of 80–90 m depth (a maximum of 200 m) and dip steeply to the south. The average content of gold is 5.04 g/t and silver – 13.01 g/t. The styles of alteration are propylitic, sericite, argillic, and advanced argillic. Ore mineralization consists of three stages. Quartz-pyrite stage I is dominated by quartz, euhedral to subhedral pyrite, trace pyrrhotite and hematite in the upper levels of the deposit. Quartz-polymetallic stage II is represented by major anhedral pyrite, galena, Fe-poor sphalerite; minor chalcopyrite, tennantite, bournonite, tellurides and electrum; and trace pyrrhotite, arsenopyrite, marcasite. Gangue minerals are quartz and carbonates. The carbonate-gold stage III is defined by deposition of carbonate minerals and barite with native gold and stibnite.

Fluid inclusions in quartz are liquid H2O-rich with homogenization temperature (Th) ranging from 238 to 345 °C as the majority of the measurements are in the range 238–273 °C. Ice-melting temperatures (Tm) range from −2.2 to −4.1 °C, salinity – from 3.7 to 6.6 wt.% NaCl equiv. These measurements imply an epithermal environment and low- to moderate salinity of the ore-forming fluids.

δ34S values of pyrite range from −0.49 to +2.44‰. The average calculated δ34S values are 1.35‰. The total range of δ34S values for pyrite are close to zero suggesting a magmatic source for the sulfur.

Read the Full Text Here

Late stage intermediate sulphidation mineralization at Breznik.
Quartz-pyrite stage I is dominated by quartz, euhedral to subhedral pyrite, trace pyrrhotite and hematite in the upper levels of the deposit. Quartz-polymetallic stage II is represented by major anhedral pyrite, galena, Fe-poor sphalerite; minor chalcopyrite, tennantite, bournonite, tellurides and electrum; and trace pyrrhotite, arsenopyrite, marcasite. Gangue minerals are quartz and carbonates. The carbonate-gold stage III is defined by deposition of carbonate minerals and barite with native gold and stibnite.

Breznik a Centre of Local Culture & Spectacular Kukeri Festival

Breznik is a delightful small town in western Bulgaria and well worth a visit.

In the middle of winter across the Balkans, Kukeri festivals allow for mid-winter celebrations.

Kukeri are elaborately costumed Bulgarian men (and some wonen) who perform traditional rituals intended to scare away evil spirits. Closely related traditions are found throughout the Balkans and Greece (including Romania and the Pontus). The costumes cover most of the body and include decorated wooden masks of animals (sometimes double-faced) and large bells attached to the belt. Around New Year and before Lent, the kukeri walk and dance through villages to scare away evil spirits with their costumes and the sound of their bells. They are also believed to provide a good harvest, health, and happiness to the village during the year. The custom is generally thought to be related to the Thracian Dionysos cult in the wider area of Thracia. (after Wikipedia)

Melting sea ice could help cool the planet by flooding the atmosphere with particles that deflect sunlight.

Immense quantities of reflective compounds, emitted by marine microbes, act like a handbrake on global warming.

Italicized text from:  The Australian, August 24, 2017

Australian research suggests climate modellers have under­estimated a natural “thermostat” that helps alleviate the rise in temperatures: immense quantities of reflective compounds, emitted by marine microbes, that act like a handbrake on global warming.

The study, published by the American Meteorological Society, suggests an overlooked source of these so-called aerosols — algae living in ice — could jam the handbrake on even harder. Lead author Albert Gabric said with the Arctic expected to see ice-free summers within a decade, far more of the aerosols would be emitted.

We examine the relationship between sea ice dynamics, phytoplankton biomass and emissions of marine biogenic aerosols in both Arctic and Southern Oceans.

Accurate estimation of the climate sensitivity requires a better understanding of the nexus between polar marine ecosystem responses to warming, changes in sea ice extent and emissions of marine biogenic aerosol (MBA). Sea ice brine channels contain very high concentrations of MBA precursors that once ventilated have the potential to alter cloud microphysical properties, such as cloud droplet number, and the regional radiative energy balance. In contrast to temperate latitudes, where the pelagic phytoplankton are major sources of MBAs, the seasonal sea ice dynamic plays a key role in determining MBA concentration in both the Arctic and Antarctic. We review the current knowledge of MBA sources and the link between ice melt and emissions of aerosol precursors in the polar oceans. We illustrate the processes by examining decadal scale time series in various satellite-derived parameters such as aerosol optical depth (AOD), sea ice extent and phytoplankton biomass in the sea ice zones of both hemispheres. The sharpest gradients in aerosol indicators occur during the spring period of ice melt. In sea ice covered waters, the peak in AOD occurs well before the annual maximum in biomass in both hemispheres. The results provide strong evidence that suggests seasonal changes in sea ice and ocean biology are key drivers of the polar aerosol cycle. The positive trend in annual mean Antarctic sea ice extent is now almost one-third of the magnitude of the annual mean decrease in Arctic sea ice, suggesting the potential for different patterns of aerosol emissions in the future.

 
“Whether that can slow the rate of warming of the Arctic is the trillion-dollar question,” said Dr Gabric, a marine biogeo­chemist with Griffith University in Brisbane.
 
Climate scientists have long known that aerosols help mitigate global warming by bouncing sunrays back into space, and by altering clouds to make them more reflective. Experts believe half of the ­potential warming from greenhouse gases may be offset in this way.
 
Much research has focused on aerosols produced artificially, through the burning of fossil fuels and vegetation. Scientists worry that if China switched to renewable sources of energy overnight, it could trigger a massive surge in warming.
 
Aerosols are also produced naturally by volcanoes — such as the 1991 eruption of Mount Pinatubo in The Philippines, which is credited with cutting global temperatures by about 0.5C for two years — and by marine ecosystems.
 
Algae known as “phytoplankton” are a major contributor, with increasingly massive blooms of these marine creatures emerging in the warming Arctic waters.
The new study analysed terabytes of satellite data to track atmos­pheric aerosol concen­trations. For the first time, it identified sea ice as a “very strong source” of the airborne particles.
 
Dr Gabric said “ice algae” had evolved to tolerate the subzero temperatures of sea ice and the water that formed it. They used a compound called dimethyl sulfide as an “antifreeze” to survive the chill. “When the sea ice melts during spring, these algae don’t need that protection any more. They expel these compounds, which are degassed to the atmosphere and converted into sulfate aerosols very similar to what you get from burning sulphur-containing coal.
 
“This happens every year as the sea ice melts. The difference in recent decades is that the ice is melting a lot earlier. We now think that within 10 years there won’t be any ice in the Arctic during summer.”
 
He said the process had “absolutely not” been factored into the Intergovernmental Panel on Climate Change models of global warming. “The whole aerosol question and its relationship to warming is the biggest uncertainty to projecting what’s going to happen this century.
 
“This is a new area of ­research, primarily because people can’t get up there and measure it very easily. You need an ice­breaker and a big gun to shoot any polar bears that might want to eat you,” he said. 

The Palaeozoic Variscan Oceans. An outstanding geoscience research contribution

 

The Variscan area of Europe with palinspastic movement of Iberia in relation to Central Europe to take account of the Bay of Biscay opening. Franke et al 2017

Gondwana Research 48 (2017) 257–284: Read Here
Wolfgang Franke, L. Robin M. Cocks, Trond H. Torsvik

The Variscan and related North American orogenies which now total 6,000 kilometres of strike, were caused by the opening and closing of the Rheic Ocean over a 100 million year period from 440MA to 320MA. This period saw the creation of several minor oceans and seaways, repeated periods of rifting and subduction and ultimately with the amalgamation of Laurussia and Gondwana, formation of the Pangea super-continent. Wolfgang Franks and colleagues have undertaken a comprehensive review and re-interpretation of the oceanic history of the Variscan domain. They attribute the complex geology to the opening and closing of 5 oceans or seaways, rifting and repeated subduction events. As a consequence of this complex tectonism, Variscan Europe is well endowed with mineral deposits although few are in production. Indeed this is where the industrial exploitation of Cu, Pb, Zn, Ag and Au commenced in post Roman times. The proposed complexity is very similar to that observed along the margins of the Tethyan Ocean to the east during a later period. This paper is well worth a detailed review.

In the comments below we summarize the Franks et al paper to produce a history of the Variscan.

A Brief History of the Variscan

Early Palaeozoic

  • From at least Cambrian times the Armorican Terrane Assemblage (ATA) appears to have formed a promontory at the edge of the Gondwana Craton near NW Africa
  • In the early Ordovician (~490MA) along the eastern side of Iapetus Ocean a rift developed along the NW flank of Gondwana forming the Rheic Ocean. A rifted Gondwana fragment Avalonia moved westwards towards Laurussia as the Rheic Ocean expanded at the expense of the Iapetus;
  • The Rheic Ocean became very wide;
  • Towards the end of the Ordovician Avalonia merged with Laurussia with much strike-slip faulting;

Silurian

  • During the Late Silurian and Early Devonian NE subduction of the Rheic Ocean lead to back-arc spreading and sedimentation in what is now in part the Rheno-Hercynian belt
  • Additional rifting in the Silurian (~440MA) along the NW margin of Africa resulted in the formation of the Saxo-Thuringian and the Galicia-Moldanubian seaways and the separation of the ATA elements from each other and ATA from Gondwana (with Palaeo-Adria to the immediate east).

Devonian

  • The Saxo-Thuringian Ocean and ultimately, collision of the Thuringia and Franconia elements of the ATA with Avalonia previously accreted onto Laurussia (Baltica) occurred at ~ 400MA with the final closure of the NW extent of the Rheic Ocean;
  • During the Devonian there was widespread strike-slip movement between ATA and Palaeo-Adria to the east possibly as consequence of east verging oblique subduction of the Saxo-Thuringian Ocean;
  • In the Early Emsian, the Rheic mid-ocean ridge was subducted southwards under the northernmost part of the ATA (Franconia), creat­ing the short-lived Baja California-type Rheno-Hercynian Ocean which incorporated the former back-arc basin sediments
  • The northward and lateral movements of Gondwana saw the successive closure of the Galicia-Moldanubian, Saxo-Thuringian and Rheic Oceans from south to north, over the period from about 380Ma through the Early carboniferous

Carboniferous and Permian

  • Laurussia and Gondwana finally collided at around 320MA to form the super-continent Pangea
  • Prior to this collision there was significant dextral strike-slip movement between Laurussia and Gondwana
  • Post collision, the Amorican terranes returned to roughly the same location prior to their separation more than 100 million years earlier;
  • This collision produced a very extensive orogen extending from the Ouachita and the Alleghanian Orogenies in North America through the Variscan of Western Europe;
  • Continued shortening into the Late Carboniferous saw dextral strike-slip faulting along the SW margin of Baltica and clockwise rotation of the Bohemian Arc into its current location
  • This orogenesis extended from the Carboniferous into the Middle Permian with collisional shortening of more than 1,000 km.

Abstract

Geological evidence, supported by biogeographical data and in accord with palaeomagnetic constraints, indicates that “one ocean” models for the Variscides should be discarded, and confirms, instead, the existence of three Gondwana-derived microcontinents which were involved in the Variscan collision: Avalonia, North Armorica (Franconia and Thuringia subdivided by a failed Vesser Rift), and South Armorica (Central Iberia/Armorica/ Bohemia), all divided by small oceans. In addition, parts of south-eastern Europe, including Adria and Apulia, are combined here under the new name of Palaeo-Adria, which was also Peri-Gondwanan in the Early Palaeozoic. Oceanic separations were formed by the break-up of the northern Gondwana margin from the Late Cambrian onwards. Most of the oceans or seaways remained narrow, but – much like the Alpine Cenozoic oceans – gave birth to orogenic belts with HP-UHP metamorphism and extensive allochthons: the Saxo-Thuringian Ocean be­tween North and South Armorica and the Galicia-Moldanubian Ocean between South Armorica and Palaeo-Adria. Only the Rheic Ocean between Avalonia and peri-Gondwana was wide enough to be unambiguously recorded by biogeography and palaeomagnetism, and its north-western arm closed before or during the Emsian in Europe. Ridge subduction under the northernmost part of Armorica in the Emsian created the narrow and short-lived Rheno-Hercynian Ocean. It is that ocean (and not the Rheic) whose opening and closure controlled the evolution of the Rheno-Hercynian fold-belt in south-west Iberia, south-west England, Germany, and Moravia (Czech Republic). Devonian magmatism and sedimentation set within belts of Early Variscan deformation and metamor­phism are probably strike-slip-related. The first arrival of flysch on the forelands and/or the age of deformation of foreland sequences constrains the sequential closure of the Variscan seaways (Galicia-Moldanubian in the Givetian; Saxo-Thuringian in the Early Famennian; Rheno-Hercynian in the Tournaisian). Additional Mid- to Late Devonian and (partly) Early Carboniferous magmatism and extension in the Rheno-Hercynian, Saxo-Thuringian and Galicia-Moldanubian basins overlapped with Variscan geodynamics as strictly defined. The Early Carboniferous episode was the start of episodic anorogenic heating which lasted until the Permian and probably relates to Tethys rifting.

Gondwana Research 48 (2017) 257–284: Read Here