cometadata/datacite-titles-descriptions-related-identifiers huggingface dataset:
DOI: 10.6084/m9.figshare.5734659
title: A Permian methane seep system as a paleoenvironmental analogue for the pre-metazoan carbonate platforms

description: ABSTRACT: Following the rise of metazoans, the beginning of bioclasticity and substrate competition, the saga of microbial mats was in a fluctuating decline in the end of the Neoproterozoic era. Increases in diversity during the Phanerozoic and punctual upturns in the microbial carbonate production occured after the events of global mass extinctions. Gradually along the Phanerozoic, the microbial colonies occupied isolated niches and grazers-free environments, characterized by physically and/or geochemically stressful conditions, such as those found in saline bays, alkaline lakes and hydrothermal or cold seep vents. Here we report one of the oldest occurrences of a vent camp coupled with cold seepage of methane in the geologic record, associated with well-preserved microbialites and elephant skin structures. During the seep activity, oxygen depletion and high salinity conditions are prohibitive for complex animal life, clearing the way to microbial colonies to flourish. Due to the co-occurrence of high adaptability and low competitiveness of microbial forms, they became highly specialized in stressful conditions. We argue that the sporadic microbial mat upturns in Earth’s history are not restricted to geological periods, following massive death of metazoan species; they also may occur in response to punctual paleoenvironmental conditions that enable microbial colonies to growth. Indeed, the Phanerozoic geological record is punctuated of these examples, in a kind of hide-and-seek game of Precambrian times.
DOI: 10.6084/m9.figshare.5734659.v1
title: A Permian methane seep system as a paleoenvironmental analogue for the pre-metazoan carbonate platforms

description: ABSTRACT: Following the rise of metazoans, the beginning of bioclasticity and substrate competition, the saga of microbial mats was in a fluctuating decline in the end of the Neoproterozoic era. Increases in diversity during the Phanerozoic and punctual upturns in the microbial carbonate production occured after the events of global mass extinctions. Gradually along the Phanerozoic, the microbial colonies occupied isolated niches and grazers-free environments, characterized by physically and/or geochemically stressful conditions, such as those found in saline bays, alkaline lakes and hydrothermal or cold seep vents. Here we report one of the oldest occurrences of a vent camp coupled with cold seepage of methane in the geologic record, associated with well-preserved microbialites and elephant skin structures. During the seep activity, oxygen depletion and high salinity conditions are prohibitive for complex animal life, clearing the way to microbial colonies to flourish. Due to the co-occurrence of high adaptability and low competitiveness of microbial forms, they became highly specialized in stressful conditions. We argue that the sporadic microbial mat upturns in Earth’s history are not restricted to geological periods, following massive death of metazoan species; they also may occur in response to punctual paleoenvironmental conditions that enable microbial colonies to growth. Indeed, the Phanerozoic geological record is punctuated of these examples, in a kind of hide-and-seek game of Precambrian times.
DOI: 10.6084/m9.figshare.5734428.v1
title: Gold, iron and manganese in central Amapá, Brazil

description: ABSTRACT: Greenstone belts with deposits of gold, iron and manganese are common in the Paleoproterozoic Maroni-Itacaiunas Tectonic Province of the Guiana Shield. In Brazil, in the State of Amapá and northwest of Pará, they are represented by the Vila Nova Group, constituted by a basal unit of metabasalts, covered by metasediments of clastic and chemical origin. The basal metasediments, the Serra do Navio Formation, are made of a cyclothem with lenses of manganese marbles at the top of each cycle. Under the intense weathering of the Amazon, these lenses were oxidized to large deposits of high-grade manganese oxides. The exploitation of these oxides left behind the manganese carbonates and low-grade oxides. The overlaying Serra da Canga Formation presents a calcium and magnesium domain grading to an iron domain with banded silicate and oxide iron formations, mined for iron ores. Overlapping structures and superposed metamorphic crystallizations indicate two phases of dynamothermal metamorphism, the first one with axis to north-northeast and the second one to northwest, with an intermediate phase of thermal metamorphism related to syntectonic granitic intrusions. Shears oriented north-south, possibly formed during the first dynamothermal metamorphism and reactivated in the second, are ideal sites for hydrothermalism and gold mineralization, which is greater when occurs in iron formation and carbonate-bearing rocks, as it happened at the Tucano mine. Layered mafic-ultramafic intrusions in the greenstones represent a potential for chromite and platinum group elements. Pegmatites are source of cassiterite and tantalite exploited from alluvial deposits.
DOI: 10.6084/m9.figshare.5734428
title: Gold, iron and manganese in central Amapá, Brazil

description: ABSTRACT: Greenstone belts with deposits of gold, iron and manganese are common in the Paleoproterozoic Maroni-Itacaiunas Tectonic Province of the Guiana Shield. In Brazil, in the State of Amapá and northwest of Pará, they are represented by the Vila Nova Group, constituted by a basal unit of metabasalts, covered by metasediments of clastic and chemical origin. The basal metasediments, the Serra do Navio Formation, are made of a cyclothem with lenses of manganese marbles at the top of each cycle. Under the intense weathering of the Amazon, these lenses were oxidized to large deposits of high-grade manganese oxides. The exploitation of these oxides left behind the manganese carbonates and low-grade oxides. The overlaying Serra da Canga Formation presents a calcium and magnesium domain grading to an iron domain with banded silicate and oxide iron formations, mined for iron ores. Overlapping structures and superposed metamorphic crystallizations indicate two phases of dynamothermal metamorphism, the first one with axis to north-northeast and the second one to northwest, with an intermediate phase of thermal metamorphism related to syntectonic granitic intrusions. Shears oriented north-south, possibly formed during the first dynamothermal metamorphism and reactivated in the second, are ideal sites for hydrothermalism and gold mineralization, which is greater when occurs in iron formation and carbonate-bearing rocks, as it happened at the Tucano mine. Layered mafic-ultramafic intrusions in the greenstones represent a potential for chromite and platinum group elements. Pegmatites are source of cassiterite and tantalite exploited from alluvial deposits.
DOI: 10.6084/m9.figshare.6124886
title: A cathodoluminescence-assisted LA-ICP-MS study of topaz from different geological settings

description: ABSTRACT: In this study, the crystallization dynamics and the fingerprints of two topaz crystals from the Ouro Preto region (Brazil), two from the Eastern Brazilian Pegmatite Province (EBPP), one from the Western part of the United States (US) and one from Pakistan were characterized. The combination of scanning electron microscope-cathodoluminescence (SEM-CL) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data allowed for the characterization of these samples. Samples from the Ouro Preto region showed primary crystallization and recrystallization processes, which were demonstrated by a CL-heterogeneous core and CL-homogeneous rims in the SEM-CL images. Their fingerprint was composed of Ca, Ti, V, Cr, Mn, Fe, Cu and Zn. Samples from the EBPP showed both dark and CL-homogeneous SEM-CL images, implying slow and late-stage crystallization, typical of pegmatites. Their fingerprints were composed of Li, Nb, LREE, Ta and W, and of Ti, Nb and HREE. A sample from a Western part of the US displayed CL-heterogeneity with growth and resorption events and well-preserved growth zones, which were noticeable through the SEM-CL images. Its fingerprint was composed of Li, Ti, V, Mn, Nb, LREE, Ta and W. A sample from Pakistan showed an evident metamorphic recrystallization process, which was visible by the incipient and CL-homogeneous luminescence given by the SEM-CL images. Its fingerprint was composed of Ca, Cr, V, Zn, LREE, HREE and W.
DOI: 10.6084/m9.figshare.6124886.v1
title: A cathodoluminescence-assisted LA-ICP-MS study of topaz from different geological settings

description: ABSTRACT: In this study, the crystallization dynamics and the fingerprints of two topaz crystals from the Ouro Preto region (Brazil), two from the Eastern Brazilian Pegmatite Province (EBPP), one from the Western part of the United States (US) and one from Pakistan were characterized. The combination of scanning electron microscope-cathodoluminescence (SEM-CL) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) data allowed for the characterization of these samples. Samples from the Ouro Preto region showed primary crystallization and recrystallization processes, which were demonstrated by a CL-heterogeneous core and CL-homogeneous rims in the SEM-CL images. Their fingerprint was composed of Ca, Ti, V, Cr, Mn, Fe, Cu and Zn. Samples from the EBPP showed both dark and CL-homogeneous SEM-CL images, implying slow and late-stage crystallization, typical of pegmatites. Their fingerprints were composed of Li, Nb, LREE, Ta and W, and of Ti, Nb and HREE. A sample from a Western part of the US displayed CL-heterogeneity with growth and resorption events and well-preserved growth zones, which were noticeable through the SEM-CL images. Its fingerprint was composed of Li, Ti, V, Mn, Nb, LREE, Ta and W. A sample from Pakistan showed an evident metamorphic recrystallization process, which was visible by the incipient and CL-homogeneous luminescence given by the SEM-CL images. Its fingerprint was composed of Ca, Cr, V, Zn, LREE, HREE and W.
DOI: 10.6084/m9.figshare.6832271
title: Geochemistry of the Northern Paraná Continental Flood Basalt (PCFB) Province: implications for regional chemostratigraphy

description: ABSTRACT: The Paraná Continental Flood Basalt (PCFB) province is one of the largest igneous provinces on Earth, but little is known about the architecture and geochemical characteristics of the lava flows. In this context, a set of borehole samples arranged in an NEE-SWW profile - more than 600 km long - located in the northern PCFB was used to define its chemostratigraphy. In this region, the outcrops are rare, and the volcanic piles are covered by hundreds of meters of sedimentary rocks from the Bauru Sub-Basin. This study aimed to explore the chemostratigraphic column from northern PCFB to improve the understanding of its internal architecture and to characterize the flood basalt sequences by using the petrography and elemental geochemistry of surface and borehole samples. The results showed the presence of the main four magma types, which were essentially distinguished by their P 2 O 5 , TiO 2 and Sr concentrations, as well as Zr/Y ratios, with excellent chemostratigraphy relations.
DOI: 10.6084/m9.figshare.6832271.v1
title: Geochemistry of the Northern Paraná Continental Flood Basalt (PCFB) Province: implications for regional chemostratigraphy

description: ABSTRACT: The Paraná Continental Flood Basalt (PCFB) province is one of the largest igneous provinces on Earth, but little is known about the architecture and geochemical characteristics of the lava flows. In this context, a set of borehole samples arranged in an NEE-SWW profile - more than 600 km long - located in the northern PCFB was used to define its chemostratigraphy. In this region, the outcrops are rare, and the volcanic piles are covered by hundreds of meters of sedimentary rocks from the Bauru Sub-Basin. This study aimed to explore the chemostratigraphic column from northern PCFB to improve the understanding of its internal architecture and to characterize the flood basalt sequences by using the petrography and elemental geochemistry of surface and borehole samples. The results showed the presence of the main four magma types, which were essentially distinguished by their P 2 O 5 , TiO 2 and Sr concentrations, as well as Zr/Y ratios, with excellent chemostratigraphy relations.
DOI: 10.6084/m9.figshare.6832478
title: Local geological sections and regional stratigraphy based on physical geology and chemical stratigraphy of the Serra Geral Group from Araraquara to Avaré, SP

description: ABSTRACT: From Araraquara to Avaré, in the Serra Geral Group outcropping area, 22 detailed geological sections were elaborated. The stratigraphic relationships and the chemical analysis allowed the identification of seven [P2O5] basalt classes, all of them pertaining to the Pitanga type, showing a consistent stacking order across the studied region. Thus, each class is considered to correspond to a specific lava flow, allowing a general stratigraphic column to be proposed. Besides the stacking order, the validation of P2O5 as a tool for lava correlation at great distances was also based on the values obtained from samples collected at different positions in a single flow, and on the remarkable [P2O5] contrast between adjacent flows. Minimum lateral extensions range from 75 to 185 km, and thickness from 20 to 80 m. Vertical tectonic displacements, which took place in different periods, were inferred from the altitude of specific flows, and also from the Botucatu and Piramboia formations. They are noticeable in a region bounded by EW drainage lineaments, which contains a large area where Piramboia and Botucatu formations crop out, probably due to the tectonic activity causing this region to be a generalized structural high.
DOI: 10.6084/m9.figshare.6832478.v1
title: Local geological sections and regional stratigraphy based on physical geology and chemical stratigraphy of the Serra Geral Group from Araraquara to Avaré, SP

description: ABSTRACT: From Araraquara to Avaré, in the Serra Geral Group outcropping area, 22 detailed geological sections were elaborated. The stratigraphic relationships and the chemical analysis allowed the identification of seven [P2O5] basalt classes, all of them pertaining to the Pitanga type, showing a consistent stacking order across the studied region. Thus, each class is considered to correspond to a specific lava flow, allowing a general stratigraphic column to be proposed. Besides the stacking order, the validation of P2O5 as a tool for lava correlation at great distances was also based on the values obtained from samples collected at different positions in a single flow, and on the remarkable [P2O5] contrast between adjacent flows. Minimum lateral extensions range from 75 to 185 km, and thickness from 20 to 80 m. Vertical tectonic displacements, which took place in different periods, were inferred from the altitude of specific flows, and also from the Botucatu and Piramboia formations. They are noticeable in a region bounded by EW drainage lineaments, which contains a large area where Piramboia and Botucatu formations crop out, probably due to the tectonic activity causing this region to be a generalized structural high.
DOI: 10.6084/m9.figshare.6832646
title: 2D magnetometric modeling of a basic-intermediate intrusion geometry: geophysical and geological approaches applied to the Limeira intrusion, Paraná Magmatic Province (SP, Brazil)

description: ABSTRACT: The Limeira Intrusion is an occurrence related to the Mesozoic continental flood basalts of Paraná Magmatic Province, cropping out at the eastern São Paulo state. It is made up of basic-intermediate rocks with a great diversity of structures, textures and modal compositions, related to specific evolutionary process in a magma chamber. Previous geological and stratigraphic evidence suggests it has a lopolithic-like geometry rather than a conventional sill-like, assumed for most regional similar occurrences. 2D forward modeling of magnetometric data, based on available aerial and newly obtained ground data integrated with in situ rock magnetic susceptibility measurements, were used to test such hypothesis. The results, even considering intrinsic drawbacks of magnetometric theoretical models, are compatible with the geologic-based presumed intrusion geometry. The determination of intrusive bodies geometry is quite significant to explain their different emplacement mechanisms. In the case of Limeira Intrusion, the results suggest that the emplacement mechanism may occur, apparently, by inner-accretion of fresh magmatic pulses in its central region. Importantly, the magmatic evolution of lopolith-like basic-intermediate intrusions may open the way for extensive differentiation processes, with strong implications to petrology and metallogenesis.
DOI: 10.6084/m9.figshare.6832646.v1
title: 2D magnetometric modeling of a basic-intermediate intrusion geometry: geophysical and geological approaches applied to the Limeira intrusion, Paraná Magmatic Province (SP, Brazil)

description: ABSTRACT: The Limeira Intrusion is an occurrence related to the Mesozoic continental flood basalts of Paraná Magmatic Province, cropping out at the eastern São Paulo state. It is made up of basic-intermediate rocks with a great diversity of structures, textures and modal compositions, related to specific evolutionary process in a magma chamber. Previous geological and stratigraphic evidence suggests it has a lopolithic-like geometry rather than a conventional sill-like, assumed for most regional similar occurrences. 2D forward modeling of magnetometric data, based on available aerial and newly obtained ground data integrated with in situ rock magnetic susceptibility measurements, were used to test such hypothesis. The results, even considering intrinsic drawbacks of magnetometric theoretical models, are compatible with the geologic-based presumed intrusion geometry. The determination of intrusive bodies geometry is quite significant to explain their different emplacement mechanisms. In the case of Limeira Intrusion, the results suggest that the emplacement mechanism may occur, apparently, by inner-accretion of fresh magmatic pulses in its central region. Importantly, the magmatic evolution of lopolith-like basic-intermediate intrusions may open the way for extensive differentiation processes, with strong implications to petrology and metallogenesis.
DOI: 10.6084/m9.figshare.6832748
title: Nepheline syenites to syenites and granitic rocks of the Itatiaia Alkaline Massif, Southeastern Brazil: new geological insights into a migratory ring Complex

description: ABSTRACT: The Itatiaia Alkaline Massif comprises some of the largest meso-cenozoic alkaline igneous occurrences in Brazil, covering over 215 km2 between the states of Minas Gerais and Rio de Janeiro. It appears as an elongated, 30-km long and 4.5-11.5-km wide SE-NW-trending body emplaced along accommodation zones of the Continental Rift of Southern Brazil, intruding metapelites, orthogneiss and granites of the Brasília and Ribeira fold belts. New data and geological mapping suggest that the massif evolved from a migratory magmatic center manifested as ring structures and successive moon-shaped intrusions from SE to NW in three sectors of distinct lithological and geomorphological characteristics: Southeastern, Central and Northwestern. The lithological variants in the three sectors present themselves as discrete intrusive bodies, comprising feldspathoid-bearing and quartz-bearing syenites, porphyritic to breccioid trachytes, granite, monzonite, gabbro and trachybasalt, which can be grouped into 21 units. These rocks occur in five petrographical sets: plagioclase-free nepheline syenites, plagioclase-bearing nepheline syenite and pulaskites, nordmarkite-granite series, anti-rapakivi associations and basic rocks. Sin- to tardi-plutonic dykes of nephelinites, phonolites, trachytes and rhyolites are also present.
DOI: 10.6084/m9.figshare.6832748.v1
title: Nepheline syenites to syenites and granitic rocks of the Itatiaia Alkaline Massif, Southeastern Brazil: new geological insights into a migratory ring Complex

description: ABSTRACT: The Itatiaia Alkaline Massif comprises some of the largest meso-cenozoic alkaline igneous occurrences in Brazil, covering over 215 km2 between the states of Minas Gerais and Rio de Janeiro. It appears as an elongated, 30-km long and 4.5-11.5-km wide SE-NW-trending body emplaced along accommodation zones of the Continental Rift of Southern Brazil, intruding metapelites, orthogneiss and granites of the Brasília and Ribeira fold belts. New data and geological mapping suggest that the massif evolved from a migratory magmatic center manifested as ring structures and successive moon-shaped intrusions from SE to NW in three sectors of distinct lithological and geomorphological characteristics: Southeastern, Central and Northwestern. The lithological variants in the three sectors present themselves as discrete intrusive bodies, comprising feldspathoid-bearing and quartz-bearing syenites, porphyritic to breccioid trachytes, granite, monzonite, gabbro and trachybasalt, which can be grouped into 21 units. These rocks occur in five petrographical sets: plagioclase-free nepheline syenites, plagioclase-bearing nepheline syenite and pulaskites, nordmarkite-granite series, anti-rapakivi associations and basic rocks. Sin- to tardi-plutonic dykes of nephelinites, phonolites, trachytes and rhyolites are also present.
DOI: 10.6084/m9.figshare.7186934
title: Emerald from the Fazenda Bonfim Deposit, northeastern Brazil: chemical, fluid inclusions and oxygen isotope data

description: ABSTRACT: The Fazenda Bonfim emerald deposit, State of Rio Grande do Norte, is within the regional geological domain known as Seridó Mobile Belt, Borborema Tectonic Province. It was formed from metasomatic fluids interaction at along lithological contacts between Be-rich albite-granite intrusions and Cr (±V)-rich mafic-ultramafic host-rocks, enclosed in the lens-shaped “hornfels” phlogopite schist. Emerald crystals display relatively high contents of Mg and Na, as well as trace amounts of Ca, K, Cs, Li, P, Sc, Ti, Mn, Co, Ni, Zn, Ga and Rb. Cr is the main chromophore element, followed by Fe and some V. Display also concentric growth zones and randomly-oriented mineral micro-inclusions, indicative for static growth. This zoning is linked to cationic substitution of alkalis accompanied by Cr loss, which favors irregular coloration of crystals. Metasomatic fluids contemporaneous with emerald growth are aqueous (H 2 O+NaCl), with low to moderate salinity and low density, although trace amounts of CO 2 ± CH 4 were also observed. These fluids showed a field-trapped between 375-430ºC and 200-600 bars, based on combination of fluid inclusions isochores. In addition, oxygen isotope data (δ 18 O = 6.9-7.4‰) suggest an igneous-metasomatic source for fluids and emerald components.