Journal of South American Earth Sciences最新文献

The ceramic industry in the productive hub of Santa Catarina needs some raw materials with specific characteristics such as kaolin to manufacture its products. This clay mineral with a naturally variable chemical composition in relation to its geolocation (in extraction area composed by rock and combined with sediment materials), attributes significant increases in transport costs due to its distance from the main productive areas in southern Brazil. Thus, as a strategic alternative, the improvement of kaolin with a high quartz content (69.9%) from the northern region of the state of Santa Catarina (∼400 km from ceramic hub in the south of the state), more precisely from the municipality of Garuva, was sought. Unit processing operations by classifying this mineral for suitability for use in industry, resulted in an increase in the concentration of kaolinite. The results indicated that the proposed method reduced the amount of quartz and consequently increased the kaolinite content, resulting in an aluminum oxide content of approximately 28.20%, a value higher than the normal natural content of ∼19%.

This work provides new stratigraphic information from the Allen and Jagüel formations (Neuquén Basin) at the Cerro Gutiérrez locality, Río Negro province. The distribution of palynomorphs allowed the definition of two palynologic assemblages: A1 corresponding to the Allen Formation, and A2 from the Jagüel Formation. The presence of taxa such as Catinipollis geiseltalensis, Gabonisporis vigorouxii, Nevesisporites vallatus, Callialasporites, Gemmamonocolpites, and Quadraplanus brossus suggests a Maastrichtian age. Due to the presence in A1 of Quadraplanus brossus, which range is Late Maastrichtian in Australia, New Zealand, and Antarctica, the age of the middle member of the Allen Formation, previously considered Late Campanian, could now be assigned to Late Maastrichtian. The palynoflora of the locality corresponds to the transitional paleoflora.

The Campo do Meio Shear Belt (CMSB) is an approximately 200 × 25 km transcurrent area along the south-southwest margin of the São Francisco Craton. A comprehensive review of geology was performed in the western CMSB, where rocks from the Campos Gerais and Petúnia Complexes are predominant. The Campos Gerais Complex is relatively well positioned in the geotectonic context of the region. It corresponds to an Archean granite-greenstone belt lithological association related to the south-southwest part of the São Francisco Craton. The Petúnia Complex, in contrast, is unraveled in this contribution through the integration of aerogeophysical data from the western Campo do Meio Shear Belt (CMSB) with new fieldwork observations and zircon U–Pb (LA-MC-ICP-MS) dating.

The Petúnia Complex has been restricted to two Mesoarchean gneissic units – Petúnia and Ribeirão da Conquista Gneiss, with crystallization ages of 2993 ± 11 Ma and 2870 ± 9 Ma, respectively. Although the ages are broadly coincident with those found in the Campos Gerais Complex, three characteristics suggest an evolutionary independent scenario (pre-S2) during the Archean for the Petúnia and Campos Gerais Complexes: i) the sharp contrast in gamma-ray emissions between these complexes; ii) the absence of komatiite affiliation in the meta-ultramafic rocks from the Petúnia Complex; and, iii) the absence of mafic dykes in the Petúnia Complex. These two complexes also can be distinguished by the frequency of Paleoproterozoic granitoid intrusions. The Petúnia Complex has only one occurrence, the Bom Jesus da Penha Metagranite, with a crystallization age of 2004 ± 11 Ma. On the other hand, several Paleoproterozoic granitoid intrusions (2.0–1.9 Ga) have been found in the Campos Gerais Complex. These Orosirian granitoids are restricted to CMSB and younger than those in the Mineiro Belt. We suggest that these Orosirian granitoids may represent remnants of a collision event that occurred after 2.1 Ga, leading to the integration of the Petúnia and Campo Gerais Complexes into the Columbia paleocontinent. During the Neoproterozoic, the evolution in the CMSBinvolved the cratonic basement and units related to the Southernmost Brasília Orogen. This set configures a tectonic mélange that underwent progressive deformation in a non-coaxial, partitioned transpressional regime.

The coastal zone is a critical and vibrant area within coastal cities. Analyzing the changes in the coastal zone of Parana State helps determine the spatiotemporal evolution patterns and driving forces of this region, providing guidance for resource protection and utilization. This study employs remote sensing (RS), Geographic Information System (GIS), and Machine Learning techniques, using Landsat data sets with eight distinct scenes from 1990 to 2024, to extract and analyze the coastline. Specifically, methodologies such as Shoreline Extraction, the Coastline Diversity Index (CDI), and the Coastline Utilization Index (CUI) were applied to assess the coastline's characteristics. The spatiotemporal characteristics of the coastline development in Parana are meticulously examined to ensure accuracy. The findings reveal that: 1) Over the past 34 years, the coastline of Parana State has shown a consistent increasing trend. Natural coastlines have been declining by 45% annually, while artificial coastlines have been increasing by approximately 55% annually. 2) The nature of the shoreline is transitioning from natural to sea-reclamation, engineering-enhanced, and degraded forest. 3) The coastline changes have occurred in three phases: The Built-up Land phase, the Port Petrochemical phase, and the Reducing Coastal Erosion phase. Significant shoreline extension is observed near both biological and ecological coasts. 4) The primary factors influencing the coastline alterations in Parana State include natural forces, human activities, and regional policies. These insights into the spatiotemporal dynamics of the Parana coastline can inform better coastal management and conservation strategies.

I-type, high-K calc-alkaline (HKCA) granites are the main components of two large Neoproterozoic batholiths that occur in different tectonic domains in SE Brazil (Agudos Grandes (emplaced in the central Ribeira Fold Belt) and Socorro (emplaced in the Socorro-Guaxupé Nappe). We investigated representative samples from both batholiths using detailed petrography by optical and electronic microscopy and chemical analysis of main minerals (amphibole, biotite and plagioclase) by EPMA aiming to obtain reliable estimates of magmatic temperatures and pressures. Granites from both batholiths show broadly similar whole-rock compositions and crystallized from oxidized magmas at ∼ NNO+1 to +2. However, they were emplaced at different depths (Agudos Grandes: 3–5 kbar; Socorro: 5–6 kbar; Al-in-hornblende geobarometry) and crystallized at slightly, but consistently different temperatures (respectively, lower and greater than 800 °C). The lower temperatures of the Agudos Grandes granites may account for the presence of titanite as a main accessory mineral, in contrast with its absence, or occurrence as thin rims in ilmenite in the Socorro granites. The pressure estimates are consistent with the metamorphic conditions of the country rocks and suggest that magma emplacement was influenced by a combination of density control and evolving tectonic stress regimes, with the dominantly more mafic rocks of Socorro emplaced at greater depths. On the other hand, higher Sr/Y ratios and REE fractionation shown by the Agudos Grandes whole-rocks may result from magma equilibration in a thicker crust (>60 km, as contrasted with ∼50 km for Socorro) at the time of magma generation. However, the possible presence of cumulate components (as suggested, for instance, by high apatite and hornblende saturation temperatures) requires that these contrasts are tested in the future by proxies that are independent of whole-rock composition (e.g., trace-element chemistry of minerals).

Sediment provenance analysis is a tool increasingly used in the study of basins. This technique allows identifying the mineralogical and lithological composition of source areas, inferring paleogeography, climate and relief, determining the main sand distribution routes, and estimating the distance and transport time. The Mesozoic volcanic-sedimentary packages of the Parecis Basin mark a significant part of the South American Platform evolution, regarding tectonism, subsidence, sedimentation, basic and alkaline magmatism, uplift and erosion. Also, these packages registers the initial stages of Andean Orogeny subduction. Different authors have established opposite stratigraphic proposals for Parecis Basin regional correlations, and also for its tectonics evolution. Given this context, there are controversies regarding the chronostratigraphic positioning and relationships between the intervals, especially the units called Salto das Nuvens and Utiariti formations. This article presents the faciological framework and facies association, heavy mineral assemblage, ZTR index and sediment sources, and U-Pb detrital zircon ages to both sub-basins. Detrital Zircon data reveal minimum ages of 124 Ma for the Rondônia sub-basin and 245 Ma for the Juruena sub-basin for sedimentary deposition attributed to the base of the Cretaceous units. The detrital age of zircons points to a varied contribution, between elements from different provinces and ages of the Amazon Craton, the Paraguay Fold Belt and records of alkaline magmatism of ages Permo-Triassic and Cretaceous in the different kimberlithic fields of Rondônia and Mato Grosso.

Coatzacoalcos is one of the notable Mexico coastal areas regarding location, activities, and resources. The purpose of the current study is to use geographic techniques to assess the spatial and temporal changes in Land Use/Cover (LULC), Land Surface Temperature (LST), and Shoreline as a result of anthropogenic and natural factors. Four calibrated multi-temporal Landsat images, dated 1993, 2003, 2013, and 2023, were combined and processed to accomplish this goal. The six primary LULC classes forest, built-up land, mining, water bodies, and agriculture were mapped using RF Machine learning algorithms. The last period (2003–2023) shows the highest rate of built-up land expansion, while the years 1993–2013 show the lowest rate of agricultural land reduction. Forest cover in the southeast decreased steadily from 339.25, 308.49, 287.43, and 211.83 km² in 1993, 2003, 2013, and 2023. There is a slight difference in mean LST between built-up areas that recorded 26, 29, 32, and 33 °C in 1993, 2003, 2013, and 2023, respectively. The following is an order of LULC from lowest to highest LST during 2023 water body 12 °C, Forest 19 °C, Agriculture Land 22 °C, Mining 26 °C, Barren Land 34 °C and Built-up Land 33 °C. In Zone B near Coatzacoalcos showed particularly high accretion as a result of building artificial structures. Maximum rates of accretion and erosion were recorded at 2.0 m/year and −9.63 m/year, respectively. Fortunately, Zone C has minimal urban development and is home to forests and agricultural areas, so the potential negative effects are reduced. This study aids in understanding spatial and temporal LULC changes, LST variations, and shoreline dynamics, crucial for the sustainable management of Coatzacoalcos coastal resources in Mexico.