cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.7508900
title: Metaturbidite-hosted gold deposits, Córrego do Sítio lineament, Quadrilátero Ferrífero, Brazil

description: A study of geology and rocks paragenesis has been conducted at the Córrego do Sítio auriferous lineament, containing the Cachorro Bravo, Laranjeiras and Carvoaria metaturbidite-hosted lode-gold deposits located in the Quadrilátero Ferrífero Region, Minas Gerais, Brazil. These representative deposits are described to illustrate the essentially similar general character of all the deposits of lineament as well as the wide compositional and mineralogical differences in the ore of the different deposits, where, for the Cachorro Bravo deposit, a geological mapping included two underground mine galleries. The Córrego do Sítio unit is a metamorphosed turbidite in an alternating sequence of metagraywackes and phyllites, with parallel to discordant metamafic dikes and sills. The ore zone is predominantly hosted at the stratigraphic break between metasedimentary and metamafic rocks. Four deformation events affected the mine sequence. Mineralized veins and veinlets are considered to have formed within a brittle-ductile shear-zone environment and occurred in multiple episodes. Different vein types are recognized, but the most important volumetrically is a S1-concordant type characterized by smoky and milky quartz-carbonate-sulfide ± sulfosalts veins. Veins are dominated by quartz, but locally they are characterized by carbonate and a large variety of sulfide and sulfosalt minerals. Pyrite is the commonest associated sulfide mineral, followed by arsenopyrite and pyrrhotite. An extensive mineralogical study of polished sections has confirmed different generations of sulfide minerals. The sulfides and sulfosalt minerals are interrelated in the veins and disseminated on wall rocks. The data are consistent with a genetic models related to other Archean lode-gold deposits.
DOI: 10.6084/m9.figshare.7508900.v1
title: Metaturbidite-hosted gold deposits, Córrego do Sítio lineament, Quadrilátero Ferrífero, Brazil

description: A study of geology and rocks paragenesis has been conducted at the Córrego do Sítio auriferous lineament, containing the Cachorro Bravo, Laranjeiras and Carvoaria metaturbidite-hosted lode-gold deposits located in the Quadrilátero Ferrífero Region, Minas Gerais, Brazil. These representative deposits are described to illustrate the essentially similar general character of all the deposits of lineament as well as the wide compositional and mineralogical differences in the ore of the different deposits, where, for the Cachorro Bravo deposit, a geological mapping included two underground mine galleries. The Córrego do Sítio unit is a metamorphosed turbidite in an alternating sequence of metagraywackes and phyllites, with parallel to discordant metamafic dikes and sills. The ore zone is predominantly hosted at the stratigraphic break between metasedimentary and metamafic rocks. Four deformation events affected the mine sequence. Mineralized veins and veinlets are considered to have formed within a brittle-ductile shear-zone environment and occurred in multiple episodes. Different vein types are recognized, but the most important volumetrically is a S1-concordant type characterized by smoky and milky quartz-carbonate-sulfide ± sulfosalts veins. Veins are dominated by quartz, but locally they are characterized by carbonate and a large variety of sulfide and sulfosalt minerals. Pyrite is the commonest associated sulfide mineral, followed by arsenopyrite and pyrrhotite. An extensive mineralogical study of polished sections has confirmed different generations of sulfide minerals. The sulfides and sulfosalt minerals are interrelated in the veins and disseminated on wall rocks. The data are consistent with a genetic models related to other Archean lode-gold deposits.
DOI: 10.6084/m9.figshare.7513388
title: Lithogeochemistry of the meta-igneous units from Arroio Grande Ophiolitic Complex, southernmost Brazil

description: Ophiolites are defined as slices of genetically-related upper mantle serpentinized peridotites and oceanic crustal rocks, tectonically displaced from its primary igneous origin of formation by plate convergence and associated (meta) sedimentary rocks of marine origin. From this premise, a meta-ultramafic-mafic-sedimentary complex (Cr-rich magnesian schists - upper mantle or crustal ultramafic cumulate candidates; epidote amphibolites, metadiorites and metagabbros - oceanic crust candidates; metasedimentary schists, quartzites and marbles - marine sedimentary rocks candidates), located in southeastern Dom Feliciano Belt (southernmost Brazil), started to be interpreted as possible slices of an ophiolitic complex related to the closure of a paleo-ocean during Brasiliano/Pan-African orogenic cycle and was called Arroio Grande Ophiolitic Complex. The present research fills the lack of geochemical data from previous studies and tests the hypothesis of an oceanic setting for the meta-igneous units of this complex from a lithogeochemistry point of view. The meta-ultramafics were interpreted as peridotites (mantle or crustal cumulates) that were subsequently serpentinized (probably in the ocean floor) and posteriorly metasomatized (probably in a continental setting). The meta-mafics were interpreted as oceanic gabbros/basalts formed in a back-arc basin. The results, together with field relationships, rock associations and petrographic evidences, support an oceanic origin for the protoliths of the meta-igneous units. The hypothesis that these rocks represent metamorphosed slices of an ophiolitic complex is still the most reasonable one. This work updates the geologic knowledge of the area and supports discussions about the evolution of Dom Feliciano Belt and Western Gondwana paleocontinent.
DOI: 10.6084/m9.figshare.7513388.v1
title: Lithogeochemistry of the meta-igneous units from Arroio Grande Ophiolitic Complex, southernmost Brazil

description: Ophiolites are defined as slices of genetically-related upper mantle serpentinized peridotites and oceanic crustal rocks, tectonically displaced from its primary igneous origin of formation by plate convergence and associated (meta) sedimentary rocks of marine origin. From this premise, a meta-ultramafic-mafic-sedimentary complex (Cr-rich magnesian schists - upper mantle or crustal ultramafic cumulate candidates; epidote amphibolites, metadiorites and metagabbros - oceanic crust candidates; metasedimentary schists, quartzites and marbles - marine sedimentary rocks candidates), located in southeastern Dom Feliciano Belt (southernmost Brazil), started to be interpreted as possible slices of an ophiolitic complex related to the closure of a paleo-ocean during Brasiliano/Pan-African orogenic cycle and was called Arroio Grande Ophiolitic Complex. The present research fills the lack of geochemical data from previous studies and tests the hypothesis of an oceanic setting for the meta-igneous units of this complex from a lithogeochemistry point of view. The meta-ultramafics were interpreted as peridotites (mantle or crustal cumulates) that were subsequently serpentinized (probably in the ocean floor) and posteriorly metasomatized (probably in a continental setting). The meta-mafics were interpreted as oceanic gabbros/basalts formed in a back-arc basin. The results, together with field relationships, rock associations and petrographic evidences, support an oceanic origin for the protoliths of the meta-igneous units. The hypothesis that these rocks represent metamorphosed slices of an ophiolitic complex is still the most reasonable one. This work updates the geologic knowledge of the area and supports discussions about the evolution of Dom Feliciano Belt and Western Gondwana paleocontinent.
DOI: 10.6084/m9.figshare.7514822
title: Structural characterization of the internal domain of Paraguai Belt, in the Cangas region, south central portion of Mato Grosso, Brazil

description: The structural study of rocks in the district of Cangas showed the identification of three phases of deformation for the Cuiabá Group in this region. The main structure oriented 120/27 is related to the first phase of deformation defined by a slate cleavage, parallel to the bedding and to the axial plane of recumbent folds. In the early stages of this phase a family of quartz veins (V1) was generated, arranged parallel to the structures of this phase of deformation, being all almost deformed. The second phase of deformation formed a crenulation cleavage (Sn+1), axial plane of opened to gentle and asymmetric normal folds, with preferential orientation 110/68. The third phase of deformation is represented by a set of centimetric to decametric scale fractures and faults with metric slip that cut all previous structures, with orientations 35/82. Related to this phase of deformation occurs a second family of quartz veins (V2), which fills the fractures related to Dn+2 and may or may not be carrying gold mineralization.
DOI: 10.6084/m9.figshare.7514822.v1
title: Structural characterization of the internal domain of Paraguai Belt, in the Cangas region, south central portion of Mato Grosso, Brazil

description: The structural study of rocks in the district of Cangas showed the identification of three phases of deformation for the Cuiabá Group in this region. The main structure oriented 120/27 is related to the first phase of deformation defined by a slate cleavage, parallel to the bedding and to the axial plane of recumbent folds. In the early stages of this phase a family of quartz veins (V1) was generated, arranged parallel to the structures of this phase of deformation, being all almost deformed. The second phase of deformation formed a crenulation cleavage (Sn+1), axial plane of opened to gentle and asymmetric normal folds, with preferential orientation 110/68. The third phase of deformation is represented by a set of centimetric to decametric scale fractures and faults with metric slip that cut all previous structures, with orientations 35/82. Related to this phase of deformation occurs a second family of quartz veins (V2), which fills the fractures related to Dn+2 and may or may not be carrying gold mineralization.
DOI: 10.6084/m9.figshare.7509245
title: Stratigraphy of the Araí Group: record of paleoproterozoic rifting in Central Brazil

description: The Araí Group is characterized by a succession of low-grade metassedimentary and metavolcanic rocks that overlaps the Aurumina Suit and the Ticunzal Formation. The related basin fill-succession of the Araí Group was probably deposited in an intracontinental rift, which evolution initiated before 1,77 My in the Paleoproterozoic. Originally this unit was subdivided in the Arraias Formation (continental sequence) and Traíras Formation (marine sequence). However, the analysis, compilation and integration of the geologic data, mainly related to the sedimentary geology and the tectono-stratigraphy, had shown the necessity to formalize four unit subdivisions, including the Água Morna, Arraias, Caldas and Traíras formations. The Água Morna Formation represents a braided river fluvial deposicional system, evolved in an intracontinental SAG basin type, during a pre-rift phase, and representing the Água Morna Tectonosequence submitted to thermal subsidence processes. The Arraias Formation represents a thick package of continental sediments, subdivided in four members: Cubículo (aluvial fans), Prata (braided river), Mutum (aeolian), Ventura (lacustrine) and Buracão (volcanic and pyroclastic), representing the Arraias Tectonosequence, which constitute the infilling of the main rift phase, under mechanic subsidence. The Caldas Formation represents the transitional depositional sequence of the Araí Group, subdivided in two informal members related to beach system: Lower Member (backshore and foreshore) and Upper Member (shoreface). The Traíras Formation represents the marine sequence, subdivided in the Boqueirão Member (mixed platform dominated by tides), Rio Preto Member (siliciclastic platform dominated by tides) and Rosário Member (mixed platform dominated by tides), integrating the Traíras Tectonosequence and developed during flexural subsidence (post rift phase). Here the rewied stratigraphy has shown well functional for mapping and regional correlations in different areas of occurrence of the Araí Group in Central Brazil.
DOI: 10.6084/m9.figshare.7509245.v1
title: Stratigraphy of the Araí Group: record of paleoproterozoic rifting in Central Brazil

description: The Araí Group is characterized by a succession of low-grade metassedimentary and metavolcanic rocks that overlaps the Aurumina Suit and the Ticunzal Formation. The related basin fill-succession of the Araí Group was probably deposited in an intracontinental rift, which evolution initiated before 1,77 My in the Paleoproterozoic. Originally this unit was subdivided in the Arraias Formation (continental sequence) and Traíras Formation (marine sequence). However, the analysis, compilation and integration of the geologic data, mainly related to the sedimentary geology and the tectono-stratigraphy, had shown the necessity to formalize four unit subdivisions, including the Água Morna, Arraias, Caldas and Traíras formations. The Água Morna Formation represents a braided river fluvial deposicional system, evolved in an intracontinental SAG basin type, during a pre-rift phase, and representing the Água Morna Tectonosequence submitted to thermal subsidence processes. The Arraias Formation represents a thick package of continental sediments, subdivided in four members: Cubículo (aluvial fans), Prata (braided river), Mutum (aeolian), Ventura (lacustrine) and Buracão (volcanic and pyroclastic), representing the Arraias Tectonosequence, which constitute the infilling of the main rift phase, under mechanic subsidence. The Caldas Formation represents the transitional depositional sequence of the Araí Group, subdivided in two informal members related to beach system: Lower Member (backshore and foreshore) and Upper Member (shoreface). The Traíras Formation represents the marine sequence, subdivided in the Boqueirão Member (mixed platform dominated by tides), Rio Preto Member (siliciclastic platform dominated by tides) and Rosário Member (mixed platform dominated by tides), integrating the Traíras Tectonosequence and developed during flexural subsidence (post rift phase). Here the rewied stratigraphy has shown well functional for mapping and regional correlations in different areas of occurrence of the Araí Group in Central Brazil.
DOI: 10.6084/m9.figshare.7519148
title: The Serra Alta Formation, Permian, in the central-eastern portion of São Paulo State, Paraná Basin, Brazil

description: The delimitation and mapping of the Serra Alta Formation in the São Paulo State, Brazil, has always been a focus of controversy in the Brazilian geological community. Despite its large extension in subsurface, which may be comparable to the Irati Formation, the Serra Alta Formation still needs more detailed studies on its stratigraphic position, fossil content, depositional systems and age. In the east-central portion of the São Paulo State, the Serra Alta Formation overlies the Irati Formation and is predominantly composed of dark grey pelitic facies. The unit is mapped from the southern boundary of the São Paulo State to the Gibóia Dome, located in the county of Rio das Pedras. In this place, the Serra Alta and Teresina formations are replaced by the red colored pelites of the Corumbataí Formation, unit that extends to north beyond the state boundaries and may be considered correlated to these units. In this work, we present columnar sections and describe the contacts of the Serra Alta Formation with vertically adjacent Permian units. We also present the detailed facies analysis, in order to characterize the depositional system. The investigation of subsurface profiles also enabled a better understanding of the architectural patterns of the succession, helping to determine its real distribution and stratigraphic position in the central-south of São Paulo State. The integration of the data allowed identifying a particular transgressive stacking pattern, contributing to detail the late Permian regressive cycle in the Paraná Basin.
DOI: 10.6084/m9.figshare.7519148.v1
title: The Serra Alta Formation, Permian, in the central-eastern portion of São Paulo State, Paraná Basin, Brazil

description: The delimitation and mapping of the Serra Alta Formation in the São Paulo State, Brazil, has always been a focus of controversy in the Brazilian geological community. Despite its large extension in subsurface, which may be comparable to the Irati Formation, the Serra Alta Formation still needs more detailed studies on its stratigraphic position, fossil content, depositional systems and age. In the east-central portion of the São Paulo State, the Serra Alta Formation overlies the Irati Formation and is predominantly composed of dark grey pelitic facies. The unit is mapped from the southern boundary of the São Paulo State to the Gibóia Dome, located in the county of Rio das Pedras. In this place, the Serra Alta and Teresina formations are replaced by the red colored pelites of the Corumbataí Formation, unit that extends to north beyond the state boundaries and may be considered correlated to these units. In this work, we present columnar sections and describe the contacts of the Serra Alta Formation with vertically adjacent Permian units. We also present the detailed facies analysis, in order to characterize the depositional system. The investigation of subsurface profiles also enabled a better understanding of the architectural patterns of the succession, helping to determine its real distribution and stratigraphic position in the central-south of São Paulo State. The integration of the data allowed identifying a particular transgressive stacking pattern, contributing to detail the late Permian regressive cycle in the Paraná Basin.
DOI: 10.6084/m9.figshare.7507337
title: Hydraulic characterization from porous aquifers of the Brazilian Federal District

description: Hydraulic conductivity (K) in unsaturated soil is a key input parameter for modeling subsurface water and solute movements. K-values are also important to better define the potential of aquifers and to optimize water resources management activities. Since K-values are usually not readily available, different techniques are applied to estimate them. This study aimed to estimate unsaturated K-values from porous aquifers found in the Federal District of Brazil. Infiltration tests were conducted in different soil types using the open-end-hole approach and the permeability test using shallow boreholes with specific depths, as reported by Heitfeld in 1979. Soil structure was taken into consideration in such estimations. In order to consider important soil properties such as soil texture and bulk density, K-values were also estimated by means of pedotransfer functions (PTFs). Soil texture was determined in the laboratory and used as input parameter for PTFs. Results from open-end-hole method and permeability test compared to those obtained from pedotransfer functions. K-values from four different shallow porous aquifers systems encountered in the Federal District varied from 10-8 ms-1 to 10-6ms-1. Highest K-values were found in Oxisols while the lowest rates were found in Inceptisols. Decreasing conductivity trend was found with increasing depth due to the increase of loamy soils. Variations in the rate of hydraulic conductivity indicated heterogeneity of porous aquifers due to differences in textural and structural characteristics of the soils.
DOI: 10.6084/m9.figshare.7507337.v1
title: Hydraulic characterization from porous aquifers of the Brazilian Federal District

description: Hydraulic conductivity (K) in unsaturated soil is a key input parameter for modeling subsurface water and solute movements. K-values are also important to better define the potential of aquifers and to optimize water resources management activities. Since K-values are usually not readily available, different techniques are applied to estimate them. This study aimed to estimate unsaturated K-values from porous aquifers found in the Federal District of Brazil. Infiltration tests were conducted in different soil types using the open-end-hole approach and the permeability test using shallow boreholes with specific depths, as reported by Heitfeld in 1979. Soil structure was taken into consideration in such estimations. In order to consider important soil properties such as soil texture and bulk density, K-values were also estimated by means of pedotransfer functions (PTFs). Soil texture was determined in the laboratory and used as input parameter for PTFs. Results from open-end-hole method and permeability test compared to those obtained from pedotransfer functions. K-values from four different shallow porous aquifers systems encountered in the Federal District varied from 10-8 ms-1 to 10-6ms-1. Highest K-values were found in Oxisols while the lowest rates were found in Inceptisols. Decreasing conductivity trend was found with increasing depth due to the increase of loamy soils. Variations in the rate of hydraulic conductivity indicated heterogeneity of porous aquifers due to differences in textural and structural characteristics of the soils.
DOI: 10.6084/m9.figshare.7506338
title: Lavras granite emplacement and gold mineralization during the development of the post-collisional volcanoplutonic center, west of the Sul-riograndense Shield: Geophysical and structural data

description: Based on the integration of original and available geological, geophysical and structural data, we assess the construction of the Lavras granite in an evolving volcanoplutonic center. This center encompasses the Lavras do Sul intrusive complex and the Hilário trachyandesitic sequence (604 - 590 Ma), both formed in the western foreland setting during the post-collisional period of the Dom Feliciano Orogeny, Sul-riograndense Shield. Brittle structures and magnetic lineaments indicate the volcanic activity starting near the orogenic collapse, since it was initially controlled by NW-SE and WNW-ESE-striking dextral transtensive systems that inverted to sinistral during tectonic relaxation. The intrusive complex was formed from the north to the south, with emplacement of the Tapera monzonite and the Lavras granite respectively, following slip change along the N70-75°W fault zone cutting it across. The granite has moderate dimensions (325 km³) and a tabular shape (length - L: thickness - T ≈ 3:1) tapering to the south, as deduced from gravity data. AMS petrofabric (anisotropy of magnetic susceptibility) reinforces two compositional-structural domains in the center and in the border of this granite body, represented by the magnesian terms (granodiorite and monzogranite) and the ferroan ones (syenogranite and alkali feldspar granite) respectively. These data together with brittle structures point to a multistage pluton constructed in two resurgent episodes involving: (1) the central laccolith through the emplacement of granodiorite beneath the monzogranite sill; and (2) the annular intrusions of ferroan granites, induced by expansion of the high-level reservoir due to recharge with lamprophyric mafic-ultramafic magmas. Its structural control, spatial distribution and association with lamprophyric dykes attest the link of gold mineralization with the last resurgent episode in a mature volcanoplutonic center.