Mineral analysis used to reconstruct the landscape and movements of large blocks of rocks in the region around 600 million years ago when recounting a research project he had started 36 years ago to reconstruct the movements of large blocks in parts of Brazil’s Northeast and Midwest around 600 million years ago geologist Ticiano dos Santos recalled a student from the Institute of Geology at the University of Campinas (IG-UNICAMP) currently at the Geological Survey of Brazil in Manaus she spent months examining dozens of rock slides under optical and scanning electron microscopes,” Ticiano recalls in one of the cut and polished rock slides with a thickness of 30 micrometers (1 micrometer is equivalent to 1 thousandth of a millimeter) she finally found micrometric grains of what she thought could be coesite — a mineral that forms at depths of around 90 kilometers (km) under an ultra-high pressure of 2.5 gigapascals roughly 25 thousand times greater than sea-level pressure Coesite is quite rare because it typically transforms into quartz as it rises to shallower depths and pressure decreases Santos / IG-UnicampA sample of rock subjected to ultra-high pressure For nearly a year during his master’s degree program geologist Matheus Ancelmi later surveyed and cataloged over 40 outcrops subjected to high pressure They then moved to an area in the municipality of Irauçuba they found another sample of the rare mineral This time the microscope analysis was tasked to Nádia Borges Gomes who at the time was also pursuing a master’s degree under Santos “The coesite discovery was huge,” says Benjamin Bley a geologist from the University of São Paulo’s Institute of Geosciences (IGc-USP) further bolsters research surrounding the geological connection between northeastern Brazil and northeastern Africa and Ticiano Santos (wearing shorts) selecting rocks and minerals in the Irauçuba area the Forquilha region used to be a mountain range comparable to the much more recent Himalayas which are still in the process of formation,” Ticiano remarks He explains that this mountain range likely formed in a subduction zone [an area where two tectonic plates meet with one sliding beneath the other] in an ancient ocean as a result of the collision of two separate continents one situated to the east of the city of Sobral “The rock formations in the western continent differ geologically from those in the eastern continent with each aging around 2.3 billion and 2.1 billion years Whenever one tectonic plate sinks beneath another a portion of the rock within the magma melts and can emerge as volcanic lava “The mountains and volcanoes in the northern regions of Brazil’s Northeast and Midwest have been entirely eroded away,” explains Ticiano “All that remains is the root of what we term the magmatic arc essentially a stretch of magmatic rocks that rose to the surface.” These magmatic arcs — also known as volcanic arcs so called because they create a shape resembling an arc when observed from above — are sections of molten mantle that rise to the surface only the foundations — or roots — of these structures have endured in Brazil Santos’s research first began in 1987 when he made his first trip through the Caatinga (semiarid scrublands) of northwestern Ceará in search of oceanic bedrock during the final year of his geology studies at the Federal University of Rio Grande do Norte (UFRN) in Natal He had set out to test a hypothesis put forth by two UFRN professors Peter Hackspacker (1952–2021) and Reinaldo Petta which postulated potential linkages between the rock formations in Ceará and Africa Alexandre Affonso / Revista Pesquisa FAPESPHowever Santos returned empty-handed from his initial trips he widened his search area and ultimately found rocks that led to the identification of the Santa Quitéria continental magmatic arc working alongside American geologist Allen Fetter then affiliated with the University of Kansas and Ebehard Wernick (1940–2019) from São Paulo State University (UNESP) in Rio Claro a year subsequent to his appointment at UNICAMP now with funding from FAPESP and the Brazilian National Council for Scientific and Technological Development (CNPq) scouring the terrain for outcrops and chipping away at stones Santos knew that the presence of the newly identified arc — characterized by distinctive rock formations several kilometers long and wide — meant that there must have been a collision between tectonic plates composed of blocks of rock from the earth’s outermost layers I chanced upon a dense black rock that looked to be primitive possibly from the time when the arc was formed,” he recalls it initially didn’t cross my mind that it could be an eclogite formed through compression deep within the earth.” But eclogite it was although his colleagues initially met this conclusion with skepticism validation came from an Indian geologist at UNICAMP after scrutinizing the rock under an optical microscope To further clarify the region’s geological history all that was lacking was to locate coesite a mineral indicating the depth at which one tectonic plate has dipped beneath another Globally, only 24 occurrences of coesite have been unearthed thus far, including the two discoveries in Ceará — the first in Brazil — as reported in the June edition of Lithos. “We will no doubt find others in Brazil,” Ticiano predicts His confidence is explained by the many research groups now studying the magmatic arcs that cut across the country “High-pressure rocks and rocks from magmatic arcs demarcate the region where tectonic plates collided,” explains Mônica Heilbron a geologist at Rio de Janeiro State University (UERJ) a tectonic plate can break off and attach to another one further away A section of the Amazonian craton [a large block of rock] used to be attached to another from North America.” Having dedicated decades to studying the Ribeira-Aracuaí magmatic arc stretching from the southern part of Bahia to the southwest of São Paulo with an age of up to 840 million years and a width of up to 40 km she explains that studies such as those by the UNICAMP group help reconstruct tectonic processes in the distant past and provide a better understanding of similar present-day phenomena “Even though the rate of magma ascent may vary “The subduction process is complete in Ceará but is still active in California and Chile as denoted by the frequent earthquakes there.” Project East border of the Santa Quitéria magmatic arc: A new ultra-high pressure belt in the Ceará Central domain? (nº 16/08289-8); Grant Mechanism Regular Research Grant; Principal Investigator Ticiano José Saraiva dos Santos (UNICAMP); Investment R$183,454.53 © Revista Pesquisa FAPESP - All rights reserved Another consequence highlighted in the article is the decrease in carbon sequestration (photo: archive/Agência Brasil) Research focusing on the Caatinga shows that by restoring the soil it is possible to achieve quality levels close to those that existed before human interference Agência FAPESP* – A study published in the journal Applied Soil Ecology analyzed the impact of desertification in the Caatinga the semi-arid shrubland and thorn forest biome in Brazil’s Northeast region and found that degradation reduces soil functionality by more than 50% reducing its ability to support plant growth and promote human and animal well-being Another consequence highlighted in the article is the decrease in carbon sequestration The research was conducted by scientists from the Federal University of Ceará (UFC) and the Research Center for Greenhouse Gas Innovation (RCGI) of the University of São Paulo (USP) They analyzed 54 soil samples taken during the dry and rainy seasons in three different areas of the Irauçuba desertification zone in the northern part of Ceará state The reduction of more than 50% in soil functionality was calculated by means of various physical biological and chemical analyses in areas degraded by human activity mainly due to compaction caused by animal trampling and ultimately accelerates the soil erosion process,” explains Antonio Yan Viana Lima student at USP’s Luiz de Queiroz College of Agriculture (ESALQ) RCGI researcher and first author of the paper carbon content and enzymatic activity proved to be favorable for vegetation growth and carbon sequestration,” says Lima “But we saw little variation in the chemical indicators between the areas studied including between restored and degraded areas This shows that biological components are important indicators of soil health because they respond rapidly to human disturbance,” he adds we found that by preventing human activity chemical and biological indices close to their original composition,” says Arthur Pereira professor at UFC and coordinator of the study are fields that were completely fenced off more than two decades ago in order to prevent human activity and animal movement No species were planted in these fields because the goal was to see how and if the vegetation would regenerate naturally without this interference “The interesting thing is that the results of the analysis in these areas were very close to what was seen in the areas with native vegetation it’s been possible to restore the health of the soil which could also be promising for carbon sequestration since these areas had higher levels of total and microbial carbon stocks,” says Pereira The study used the Soil Management Assessment Framework (SMAF) tool in the semi-arid region is based on calculations performed by algorithms that place the results of the factors analyzed on a scale of 0 to 100 This results in a final number corresponding to a soil health index The research group is now extending the analysis to the three other desertification zones in the semi-arid region to see if the situation observed in Irauçuba is representative of the entire Caatinga and if there are other techniques for restoring degraded soils These new endeavors are being developed as part of the Caatinga Microbiome Initiative (CMI) project an inter-institutional initiative created in 2022 that involves more than 20 professors and researchers from Brazil and abroad to study the microbiome of the Caatinga and its relationship with soil health The research is part of several projects in the Nature Based Solution program of the RCGI, an Engineering Research Center (ERC) set up by FAPESP and Shell with the support of several companies Among the center’s initiatives is Project 53 which develops integrated agricultural systems a strategy for producing a variety of crops in the same area while respecting the seasonality of each crop The article “Grazing exclusion restores soil health in Brazilian drylands under desertification process” can be read at: www.sciencedirect.com/science/article/pii/S0929139323003050