Abstract The Northern Andes in Colombia are involved in a continuous mountain-building process along an active subduction zone, resulting in significant Cenozoic compression, leading to substantial Neogene shortening and topographic development. It is believed that, during the Miocene, some major geological structures reached their present-day elevation; this is the case of the Garzón Massif, an orographic barrier between the Middle Magdalena Valley and the Putumayo Basins. Some studies have been performed in order to understand the exhumation history of the Massif; however, whether the cooling process was slow or fast, and whether this occurs continuously or episodically, as well as the possible influence of faults on exhumation, is a matter of discussion. Using new apatite fission track thermochronology in combination with published data, we aimed to reconstruct the cooling history of the Massif. Our results show that cooling was asynchronous, with fault-bounded blocks cooling independently starting around 70 Ma. Cooling of the southernmost block (B6) occurs during Maastrichtian (~4.9°C/Myr), in blocks B2, B3, and B5 in Eocene (~5.3–5.6°C/Myr), and in blocks B1 and B5 from Late Oligocene to Miocene (~9°C/Myr and ~23°C/Myr, respectively). Faster cooling rates from the Miocene onward may be related to the accretion of the Panama-Choco block against the continent.

Abstract The integrated hydrothermal evolution of the large Santa Otília Paleodune from the Botucatu paleoerg and the cover Catalán Flow from the Serra Geral Group is here evaluated in Uruguaiana, southern Paraná Basin. Methods included satellite images, field surveying, petrography, and U-Pb geochronology of detrital and volcanic zircon. The tops of the compound linear-barchan paleodunes are exposed in the topographic highs. Rhombi and bowls at the top of the silicified sandstone units are significant, as is the poor preservation of eolian layering. The fishbone-shaped dune tops are surrounded by the lavas. The oxidized top of the flow (upper Tier 2) overlies the reduced base (Tier 1), which consists of exposed, massive rocks in creek beds that are light gray-colored and contain small (10 cm) agate geodes and numerous silicified sandstone dikes. The youngest dated zircon grains from the sandstone are 225–300 Ma old (one 175 Ma age), and the main older age peaks are 450–600 Ma (predominant), 900–975 Ma, 1800–1900 Ma, and 2500 Ma; few Archean 2.5 Ga ages. The strongly altered volcanic zircon preserved in the reddened Catalán Flow yields a concordia-intercept age of 137.3 ±7.6 Ma. Complex processes are thus constrained in the evolution of the Botucatu Formation and the first Serra Geral lava flow.

Abstract This paper presents a geological study of the subvolcanic bodies present in the Pico dos Três Estados (São Paulo (SP), Rio de Janeiro (RJ), and Minas Gerais (MG)) and its surroundings at the Passa Quatro Alkaline Complex. In this study, we used field-collected data, petrography, and geochemical analysis data. From a more detailed fieldwork, we verified that the region that appeared to present only two lithologies in previous works presented a faciological complex with at least six distinct facies, with emphasis on the phonolitic body that forms the Pico dos Três Estados (2,665 m high). Still regarding fieldwork, we found that there are signs of magma mingling processes in the area. Modeling indicates that 10% of fractional crystallization was able to derive the phonolitic rocks from a trachytic liquid based on the following elements: Y, Nb, Yb, Ce, Sm, Eu, La, Nd, Hf, and Pr. The modal batch partial melting shows the possible mantle sources for the magmatism in this area. This data pointed out the involvement of an enriched mantle source in the La/Yb ratio by at least 16 times more than an Oceanic Island Basalt (OIB)-type mantle.

Abstract The Jacareacanga Group comprises mafic to ultramafic schists, metacherts, quartzites, pelitic paragneisses, and amphibolites related to siliciclastic-chemical sedimentation and mafic-ultramafic volcanism. These rocks of the Jacareacanga Group correspond to turbidite-related sediments and oceanic crust basalts of a back-arc or trench basin of the early magmatic Cuiú-Cuiú Arc of the Tapajós Domain in the Amazon Craton. Field data and petrographic analysis support the new zircon U-Pb ages obtained through LA-ICP-MS for the rocks of the Jacareacanga Group. A ± 10% concordance criterion applied, along with an exclusion of ages < 2000 Ma to mitigate interference from later events, such as granitic intrusions. Two pelitic paragneisses yielded 207Pb/206Pb ages between 2008 and 2042 Ma and mica schist ages of ca. 2056 Ma, considered to be the maximum sedimentation age of the protoliths of metasedimentary rocks. Zircon populations from the Rhyacian to the Mesoarchean indicate provenance from adjacent cratonic areas. This study shows that the Jacareacanga Basin was formed during the early Orosirian. The oldest detrital zircon ages support provenance from a magmatic arc basin of a continental margin comprising Rhyacian to Mesoarchean crust.

Abstract The structure of two superposed layers within a redox-altered basaltic flow is restricted to the Paraná Volcanic Province among large igneous provinces. World-class amethyst-geode and agate-geode deposits occur in reduced Tier 1 of the Cordillera Flow (> 100 km long). Satellite and drone-sourced imagery, several field surveys, and 11 new geochemical analyses were used in this study. The lower Tier 1 (10 m thick) consists of massive rocks without cooling joints, whereas the barren Tier 2 is massive with colonnade. The flow is identified from the stratigraphy and chemical composition (e.g., 1.3 wt.% TiO2). The presence of poikilitic microphenocrysts of magnetite (mostly plagioclase inclusions) is a distinctive feature. Tier 2 rocks are chemically similar to the original lava; Tier 1 displays a decrease in SiO2 and K2O contents and an increase in Fe2O3T. Reducing and acidic hot water formed amethyst and agate deposits in Tier 1. Curved shapes (erosional remnants with agate) were formed by silicification of the lower portion of the flow. The interaction of the Guarani Paleoaquifer with the lava flow formed the two layers: the geodes and the curved portions. Other provinces may have similar features where hot aquifer water was available below the basalt.

Abstract The Upper Jurassic to Lower Cretaceous Botucatu Formation of the Paraná Basin consists primarily of trough cross-bedded eolian sandstone deposited in an intracontinental desert. In southeastern Brazil, an unusual occurrence of conglomerate and coarse-grained sandstone unconformably overlies the Neoproterozoic basement and is overlapped by volcanic rocks of the Serra Geral Formation. This represents one of the few documented occurrences of fluvial facies described for the Botucatu Formation in the northern part of the basin. To determine its depositional system and source area, we conducted facies and paleocurrent analysis, detrital grain modal counting, macroscopic provenance, and conventional heavy mineral analysis. The integrated analysis suggests that the studied succession was deposited by an ephemeral fluvial system at the margins of the extensive dune fields of the Botucatu paleodesert. Paleocurrent data and detrital composition indicate sediment dispersal toward the SE, with a possible source area associated with a recycled orogen to the NW (Brasília Belt). Although ephemeral rivers acted as important sediment suppliers for this continental-scale desert, recycling of eolian sediments by fluvial systems is not ruled out. Finally, using a multi-proxy approach, we present a paleogeographic scenario for the northern margin of the Botucatu paleodesert during the last period of Gondwana, prior to its initial rifting.

Abstract Poorly lithified siliciclastic rocks correspond to important post-salt reservoirs in the Southeastern Brazilian Margin offshore basins. These reservoirs present challenges regarding the prediction of the hydraulic behavior of faults due to low cohesion leading to diffuse brittle deformation. To improve the understanding of the deformation influence on the reservoir quality of these rocks, this paper presents a 3D modeling method based on an outcrop analog composed of Paleogene poorly lithified fluvial siliciclastic deposits in the Volta Redonda Basin (Continental Rift of Southeastern Brazil). A database was collected containing a 3D digital terrain model of the outcrop, a 1:50-scale geological section, permeability and porosity measurements, and lithological and sonic log from a well drilled upon the outcrop to the basement. Two models were built: one using traditional methods for industry where properties were uniformly distributed throughout the grid and a second model where sectors were delimited and populated with data from deformed rocks, highlighting the impact of tectonic structures (faults and deformation bands) on fluid flow, reducing the permeability by one order of magnitude, and increasing the flow time between wells by more than 10%. This study contributes to improving reservoir modeling accuracy, enhancing the understanding of fluid flow behavior in complex, deformed, poorly lithified rocks.

Abstract Situated between the Campos and Santos basins, the Cabo Frio High emerges as a focal point of heightened magmatic activity during the Santonian–Campanian and the Eocene period following the breakup of these basins. The geodynamic framework associated with these events took place during their passive margin stage, wherein magmatic occurrences could potentially be attributed to the reactivation of significant geological structures or thermal enhancement facilitated by proximal hotspots, within a context of lithospheric thinning (i.e., Trindade Plume). This investigation unveils novel Sr–Nd–Pb–Hf isotope data derived from alkaline magmatic rocks extracted from three boreholes strategically positioned within the Cabo Frio High area. The evolutionary trajectory of these rocks reflects the intricate processes of assimilation and fractional crystallization. The results of the analysis and binary mixing modeling point out to an involvement of both depleted (characterized by Depleted Mantle [DM]/Mid-Ocean Ridge Basalt [MORB] or HIMU compositions) and enriched (manifesting as the Enriched Mantle I [EMI] and the Enriched Mantle II [EMII]) sources in the genesis of these magmas. Moreover, the discerned incorporation of a fertile Ocean Island Basalt (OIB-like) reservoir hints at a plausible association with the Trindade Plume, amplifying the complexity of the magmatic genesis within the studied region.

Abstract The AN-34 and QT-02 iron oxide–copper–gold (IOCG) prospects are located in the northern portion of Carajás Mineral Province (CMP), where important copper IOCG deposits occur. This region lacks basic geological information on the outskirts of the large IOCG deposits, and these small prospects might provide information regarding fluid–rock interaction and alteration-mineralization styles. In these prospects, banded iron formations (BIFs), basic volcanic rocks, and granitoids are variably deformed and hydrothermally altered. The hydrothermal alteration evolved from early silicification, potassic alteration, and Fe enrichment. All these alterations are pervasive and linked to shearing structure development. They are followed by late, ductile-brittle, chloritic alteration and sodic alteration. The quartz–magnetite oxygen isotope geothermometry (δ18Oqtz–mag) and chlorite geothermometry reveal a decrease in the temperature of the hydrothermal system from 520°C ± 30°C to 273°C ± 20°C. The calculated δ18OH2O for silicification (6.6–5.8‰) and Fe enrichment (9.2–10.47‰) suggest the involvement of magmatic fluids. δ18OH2O values from 0.27 to 0.77‰ and 1.7 to 3.3‰ from late sodic alteration and hematite are compatible with meteoric fluids. Our findings shed more light on the fluid–rock interaction, hydrothermal evolution, and mineralization styles in the IOCG deposits of the northern sector of the CMP.

Abstract The Neoproterozoic Dom Feliciano Belt, the southern portion of the Mantiqueira Province, has over half of its area composed of granitic rocks, forming a granitic belt from Uruguay to the southern region of Brazil. The continuum of the batholith is interrupted by the Phanerozoic cover of the Paraná Basin. The Florianópolis Batholith is composed of granitic suites that crystallized between 640 and 580 Ma, with its northern limit defined by the Major Gercino Shear Zone. The batholith crops out about 15 km west of the current border of the Paraná Basin, along a valley sculpted by the Adaga and Lessa rivers. The importance of this region lies in the limited information about the continuity of the batholith beneath the sedimentary cover. This work aims to characterize field and petrographic features and crystallization age using U-Pb laser ablation-inductively coupled plasma mass spectrometry methodology on zircon and titanite of granitoid rocks that crop out in the Picadas region. These rocks are coarse to medium-fine-grained monzogranites, porphyritic to equigranular, with biotite and hornblende as the mafic phases. The U-Pb results showed the existence of Paleo, Meso, and Neoproterozoic (Tonian) inheritances and crystallization events at ca. 630–624 Ma and at 598 Ma.

Abstract The Uruguayan onshore portion of the Pelotas Basin is the Laguna Merin Basin. Despite its interesting geological and geophysical features, such as the highest Bouguer gravity anomaly and the youngest volcanic calderas in the country, it is the least known basin in Uruguay. In this study, a stratigraphic chart is presented for the first time, and an integrated analysis of its sedimentary infill is performed through the acquisition of horizontal-to-vertical spectral ratio data as well as geological and geophysical data available from previous studies. The Cretaceous sedimentary infill was restricted to the rift phase, corresponding to alluvial and fluvial deposits. The Cenozoic sedimentary cover corresponds to continental to marine sedimentary rocks and sediments deposited from the Oligocene to the present day in a drift tectonic framework. It presents a regional areal extension that exceeds the structural rifting borders of the basin. The maximum Cretaceous/Cenozoic sedimentary infill thickness is ~500 m. Cretaceous sedimentary units related to the rift and Oligocene drift phases are only present in the Uruguayan portion of the onshore Pelotas Basin, and the thickness of the Cenozoic drift deposits (from the Miocene to modern deposits) in the Brazilian region is at least twice that in the Uruguayan region.

Abstract The definition of geological domains is critical for mineral exploration and has been enhanced through the development of three-dimensional (3D) models. This study focuses on the marble ore bodies in the Canta-Galo Marble District, located in Acarape, Ceará, Brazil, and owned by Geolux Company. Geologically, the Geolux Marble Mine lies within the Borborema Province, specifically in the Northern Domain of the Central Ceará Subdomain. The 3D model was developed using lithostructural mapping, drill hole descriptions and sampling, and an analysis of ore production and mining processes. Data were compiled into a geological database and modeled using the Leapfrog Geo® software. Geolux extracts dolomitic marble, which is then transported to external companies for processing. This manuscript presents a geological model of the marble deposit, based on historical drill holes and geological mapping of the Canta-Galo District. The 3D geochemical and geological interpretation of drill holes reveals the distribution of MgO and SiO2 contents in pure and impure dolomitic marbles. Estimating marble resources will be crucial for medium- to long-term mine planning in this important district of Ceará State.

Abstract This article presents a study of the titanium-rich andradite garnet, melanite, which occurs in the rocks of the Morro de São João Alkaline Complex, of Paleocene age, located in the district of Casimiro de Abreu, southeast of the state of Rio de Janeiro, Brazil. The complex comprises felsic to mafic syenitic rocks associated with pseudoleucite. The garnet-bearing rocks are composed of a mineralogical assemblage rich in Ti and Ca, consisting mainly of alkali-feldspar, nepheline, clinopyroxene and amphiboles rich in calcium, and accessory phases containing titanite, titanite-rich magnetite, apatite, annite, and melanite. This mineral has contents of up to 4.91 wt.% TiO2, and its molecular constituents include andradite (73.54%), grossular (17.09%), and hutcheonite (9.34%). The presence of melanite, mainly associated with calcium clinopyroxene, indicates a crystallization environment characterized by conditions of high oxygen fugacity and the influence of mantle metasomatism at its source. Furthermore, as this garnet is the result of late crystallization, its presence indicates that the bearing rocks, even the most parental ones, are evolved rocks, given the low contents of MgO (< 8.14 wt.%) and Ni (< 60 ppm), as opposed to the high levels of Ba (< 10,840 ppm), Rb (< 464 ppm), and Sr (< 10,000 ppm).

Abstract Net erosion recorded in lithological columns of hundreds of wells from the proximal domain of the Sergipe–Alagoas Basin was quantified through palaeoburial indicators: transit time sonic logs (DT) and vitrinite reflectance profiles (VRe). The preferred determinations with DT logs of pelitic rocks compound a large database and are less subject to variations in sampling and laboratory procedures. The sonic log profiles of 485 wells have been used for the calculation of the net erosion grid, while just 60 VRe profiles have been used for this purpose. Net erosion varies typically from 100 to 700 m in the Sergipe Sub-basin to the south, probably as a result of isostatic compensation to the sedimentary loads of the post-rift stratigraphic sequences. The Alagoas Sub-basin to the north stands as the most eroded. The average net erosion in the Alagoas SB is around 750 m but reaches more than 1,200 m in the north. The main cause of the erosion of the syn-rift strata in the Alagoas SB is probably the long-time sub-aerial exposure of uplifted rift flanks. Late Albian tectonic inversion, focused on northern Alagoas SB, enhanced erosion as evidenced in seismic sections, especially those parallel to the coast.