Iron Pyrites

26 Oct 2019

This is a peculiar one - and comes courtesy of https://phys.org/news/2019-10-shelf-life-pyrite.html ... where we are informed the glacial cycles of the last couple of million years - a succession of cold periods interspersed with warm interglacials - may have an origin in the weathering of pyrite rocks. For knowledge of what pyrite actually is go to https://en.wikipedia.org/wiki/Pyrite ... where we are told the mineral pyrite (also known as iron pyrites and quite commonly found in geological formations, including sediment layers). It is also known as fools gold and can form crystals. It is an iron sulfide -the most common of all sulfide minerals. It can even be found in coal. It is most often found associated with other sulfic oxides, is found in quartz veins, sedimentary rocks, and in metamorphic rocks - as well as in coal beds (and as a replacement mineral in fossils).

So, with that background in mind, it reads, 'it is widely accepted that changes in the concentration of carbon dioxide and other greenhouses gases (unspecified) in the atmosphere are largely responsible for these natural fluctuations of cold and warm periods' and 'what exactly triggers the increase in carbon dioxide concentrations that cause the transition from glacial to warm is not fully understood.' Dr Martin Kolling of Bremen University (a marine environmentalist rather than a geologist) has developed a new model in which the weathering of pyrite, a common mineral containing sulfur, plays a key role. The findings were published in Nature Geoscience (Oct 2019). Apparently, on exposure to air pyrite is oxydised and produces an acid which is capable of dissolving carbonate minerals. It is also said to release co2 - which is somehow then lofted into the atmosphere (bearing in mind the excruciatingly slow production). He admits the release of co2 in this context was small - but caused the climate to switch from cold to warm. In the modern world humans are releasing much greater amounts of co2 but the temperature remains stubbornly at a standstill. It is however projected to rise at some point in the future - from ten years time to hundreds of years time. Nobody knows. In geology there is a lot of time to play around with and on this aspect he is on safer ground.

Another assumption in the model (accepted without comment) is that during glacial periods sea levels were much lower. We know the North Atlantic had much lower sea levels during the Late Glacial Maximum but it does not follow that during every glacial period sea levels were lower. For example, during what is termed as the last Ice Age (but older than the LGM) sea levels in the Mediterranean were unaccountably high. Is wishful thinking part of the environmentalist dabbles and excursions into science? It does of course make it easy to piece together his model by accepting that assumption - and ignoring anything to the contrary. It also leads into the main thrust of his model - that during warm periods sea levels rise and cover continental shelf systems. Once under water new pyrites are formed in sedimentary layers that have been drowned - 'through the breakdown of organic matter.' They go on to say the short interglacials are not sufficient to replenish the pyrite fully and therefore the sea levels must migrate further downwards (on each occasion) in order for pyrite weathering to be effective. Currently, the pyrite front is 90m below modern sea levels.

One has to wonder if it is being proposed that this happened on a global scale and what evidence he has that sea levels change worldwide during glacial periods and warm periods - quite apart from the correlation with co2. Geologists tend to be hard headed so I wonder what they are thinking when reading this copy of Nature Geoscience (or are they resigned to an endless stream of environmentalist tall tales).