ORCID Profile
0000-0003-1209-4094
Current Organisation
University of Queensland
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Publisher: Elsevier BV
Date: 11-2016
Publisher: Elsevier BV
Date: 05-2013
Publisher: Elsevier BV
Date: 04-2010
Publisher: Elsevier BV
Date: 11-2012
Publisher: Elsevier BV
Date: 08-2003
Publisher: American Association for the Advancement of Science (AAAS)
Date: 18-10-2013
Abstract: On Earth, atmospheric methane is mostly produced biologically. Atmospheric methane has also been detected on Mars, but these reports have been controversial. Based on data from the S le Analysis at Mars instrument suite on the Curiosity rover, which arrived at the surface of Mars in August 2012, Webster et al. (p. 355 , published online 19 September) report no methane, with an upper limit of only 1.3 parts per billion by volume, about 6 times lower than previous measurements.
Publisher: Elsevier BV
Date: 08-2016
Publisher: Springer Science and Business Media LLC
Date: 07-08-2008
DOI: 10.1038/NATURE07138
Abstract: The subduction of oceanic plateaux, which contain extraordinarily thick basaltic crust and are the marine counterparts of continental flood-basalt provinces, is an important factor in many current models of plate motion and provides a potential mechanism for triggering plate reorganization. To evaluate such models, it is essential to decipher the history of the collision between the largest and thickest of the world's oceanic plateaux, the Ontong Java plateau, and the Australian plate, but this has been hindered by poor constraints for the arrival of the plateau at the Melanesian trench. Here we present (40)Ar-(39)Ar geochronological data on hotspot volcanoes in eastern Australian that reveal a strong link between collision of the Greenland-sized Ontong Java plateau with the Melanesian arc and motion of the Australian plate. The new ages define a short-lived period of reduced northward plate motion between 26 and 23 Myr ago, coincident with an eastward offset in the contemporaneous tracks of seamount chains in the Tasman Sea east of Australia. These features record a brief westward deflection of the Australian plate as the plateau entered and choked the Melanesian trench 26 Myr ago. From 23 Myr ago, Australia returned to a rapid northerly trajectory at roughly the same time that southwest-directed subduction began along the Trobriand trough. The timing and brevity of this collisional event correlate well with offsets in hotspot seamount tracks on the Pacific plate, including the archetypal Hawaiian chain, and thus provide strong evidence that immense oceanic plateaux, like the Ontong Java, can contribute to initiating rapid change in plate boundaries and motions on a global scale.
Publisher: Elsevier BV
Date: 03-1994
Publisher: American Association for the Advancement of Science (AAAS)
Date: 31-05-2013
Abstract: The Mars Science Laboratory spacecraft containing the Curiosity rover, was launched from Earth in November 2011 and arrived at Gale crater on Mars in August 2012. Zeitlin et al. (p. 1080 ) report measurements of the energetic particle radiation environment inside the spacecraft during its cruise to Mars, confirming the hazard likely to be posed by this radiation to astronauts on a future potential trip to Mars. Williams et al. (p. 1068 , see the Perspective by Jerolmack ) report the detection of sedimentary conglomerates (pebbles mixed with sand and turned to rock) at Gale crater. The rounding of the rocks suggests abrasion of the pebbles as they were transported by flowing water several kilometers or more from their source.
Publisher: Elsevier BV
Date: 02-2011
Publisher: Elsevier BV
Date: 09-2015
Publisher: Elsevier BV
Date: 11-2020
Publisher: Universidade de Sao Paulo, Agencia USP de Gestao da Informacao Academica (AGUIA)
Date: 12-2002
Publisher: Proceedings of the National Academy of Sciences
Date: 21-07-2020
Abstract: Successful mine remediation is often the missing link in the circular and sustainable model for metal mining. Here, we provide compelling evidence that promoting the biogeochemical cycling of iron can be used to stabilize and remediate mine surfaces using crushed mine waste products. These microbially stabilized iron-rich crusts provide a surface similar to premining conditions that can be used to revegetate iron mine waste using the naturally rare plant species associated with these environments. Reformation of these iron-rich crusts will help to restore hydraulic function to degraded land sites and may provide an approach to reduce on the onset of acid mine drainage in sulphide-rich wastes.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 07-01-2022
Abstract: The discovery of an exceptionally well-preserved fossil site provides new insight into the nature of Miocene ecosystems.
Publisher: Elsevier BV
Date: 12-2021
Publisher: University of Chicago Press
Date: 09-2012
DOI: 10.1086/666745
Publisher: Wiley
Date: 15-07-2023
DOI: 10.1002/ESP.5660
Abstract: Lithology plays a fundamental role in rock weathering and erosion, and in landscape evolution. When weathering‐ and erosion‐prone lithologies are protected from erosion by more resilient rock types (e.g., quartzites and banded iron formations) unusual weathering products result. At the Southern Espinhaço Range, Minas Gerais, Brazil, bauxitic weathering profiles are found in a unique geomorphological–lithological–climatic setting. Resistant quartzites acted as a barrier against erosion of interbedded hematite‐phyllite lenses, channelling solution flows and facilitating the formation of deep weathering profiles. The long‐term exposure of the hematite‐phyllites under alternating wet and dry tropical climates favoured widespread bauxitization. Here we investigate the geochemical, mineralogical, geochronological and micromorphological signatures of scaffolded bauxites in order to reconstruct their evolutionary history. Our data suggest that recurrent aluminium and iron mobilization within the profiles were mainly driven by mineral dissolution‐reprecipitation mediated by bioturbation and the influx of vegetation‐derived organic species. (U–Th)/He geochronology of Al‐goethite reveals that bauxitization started at least since the Lower Miocene, with important intensification of weathering in the Upper Miocene and Lower Pleistocene. The adjacent resilient quartzites acted as scaffolds for bauxitization and supported the preservation of more erodible weathering profiles developed over phyllites. Surface waters that could not infiltrate into the impermeable adjacent quartzites preferentially infiltrated into the more weathereable phyllites, enhancing their porosity and permeability, further enhancing weathering. The evolutionary history of Southern Espinhaço Range bauxites suggests a new model of bauxitization in ancient land surfaces evolution underlain by quartzites, where erosion‐prone lithologies are scaffolded by resilient quartzites and survive long‐term weathering with minimum erosion, producing bauxites.
Publisher: Elsevier BV
Date: 05-2018
Publisher: Elsevier BV
Date: 09-2017
Publisher: Elsevier BV
Date: 2022
Publisher: FapUNIFESP (SciELO)
Date: 2021
Publisher: Elsevier BV
Date: 06-2002
Publisher: Elsevier BV
Date: 05-1995
Publisher: Elsevier BV
Date: 11-2013
Publisher: Elsevier BV
Date: 07-2018
Publisher: Geological Society of America
Date: 2001
Publisher: American Association for the Advancement of Science (AAAS)
Date: 27-09-2013
Abstract: The Mars Science Laboratory rover Curiosity scooped s les of soil from the Rocknest aeolian bedform in Gale crater. Analysis of the soil with the Chemistry and Mineralogy (CheMin) x-ray diffraction (XRD) instrument revealed plagioclase (~An57), forsteritic olivine (~Fo62), augite, and pigeonite, with minor K-feldspar, magnetite, quartz, anhydrite, hematite, and ilmenite. The minor phases are present at, or near, detection limits. The soil also contains 27 ± 14 weight percent x-ray amorphous material, likely containing multiple Fe 3+ - and volatile-bearing phases, including possibly a substance resembling hisingerite. The crystalline component is similar to the normative mineralogy of certain basaltic rocks from Gusev crater on Mars and of martian basaltic meteorites. The amorphous component is similar to that found on Earth in places such as soils on the Mauna Kea volcano, Hawaii.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 27-09-2013
Abstract: The Rocknest aeolian deposit is similar to aeolian features analyzed by the Mars Exploration Rovers (MERs) Spirit and Opportunity. The fraction of sand micrometers in size contains ~55% crystalline material consistent with a basaltic heritage and ~45% x-ray amorphous material. The amorphous component of Rocknest is iron-rich and silicon-poor and is the host of the volatiles (water, oxygen, sulfur dioxide, carbon dioxide, and chlorine) detected by the S le Analysis at Mars instrument and of the fine-grained nanophase oxide component first described from basaltic soils analyzed by MERs. The similarity between soils and aeolian materials analyzed at Gusev Crater, Meridiani Planum, and Gale Crater implies locally sourced, globally similar basaltic materials or globally and regionally sourced basaltic components deposited locally at all three locations.
Publisher: Informa UK Limited
Date: 19-03-2022
Publisher: Elsevier BV
Date: 11-2009
Publisher: Elsevier BV
Date: 08-2020
Publisher: Informa UK Limited
Date: 04-2008
Publisher: Elsevier BV
Date: 09-2011
Publisher: American Association for the Advancement of Science (AAAS)
Date: 27-09-2013
Abstract: “Jake_M,” the first rock analyzed by the Alpha Particle X-ray Spectrometer instrument on the Curiosity rover, differs substantially in chemical composition from other known martian igneous rocks: It is alkaline ( % normative nepheline) and relatively fractionated. Jake_M is compositionally similar to terrestrial mugearites, a rock type typically found at ocean islands and continental rifts. By analogy with these comparable terrestrial rocks, Jake_M could have been produced by extensive fractional crystallization of a primary alkaline or transitional magma at elevated pressure, with or without elevated water contents. The discovery of Jake_M suggests that alkaline magmas may be more abundant on Mars than on Earth and that Curiosity could encounter even more fractionated alkaline rocks (for ex le, phonolites and trachytes).
Publisher: Elsevier BV
Date: 07-2014
Publisher: American Geophysical Union (AGU)
Date: 05-2019
DOI: 10.1029/2018GC008124
Publisher: Elsevier BV
Date: 09-2010
Publisher: American Association for the Advancement of Science (AAAS)
Date: 27-09-2013
Abstract: S les from the Rocknest aeolian deposit were heated to ~835°C under helium flow and evolved gases analyzed by Curiosity’s S le Analysis at Mars instrument suite. H 2 O, SO 2 , CO 2 , and O 2 were the major gases released. Water abundance (1.5 to 3 weight percent) and release temperature suggest that H 2 O is bound within an amorphous component of the s le. Decomposition of fine-grained Fe or Mg carbonate is the likely source of much of the evolved CO 2 . Evolved O 2 is coincident with the release of Cl, suggesting that oxygen is produced from thermal decomposition of an oxychloride compound. Elevated δD values are consistent with recent atmospheric exchange. Carbon isotopes indicate multiple carbon sources in the fines. Several simple organic compounds were detected, but they are not definitively martian in origin.
Publisher: Elsevier BV
Date: 03-2005
Publisher: Elsevier BV
Date: 03-2015
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 10-2019
Publisher: Elsevier BV
Date: 11-2021
Publisher: Elsevier BV
Date: 02-2012
Publisher: Elsevier BV
Date: 08-2008
Publisher: Elsevier BV
Date: 02-2005
Publisher: Springer Science and Business Media LLC
Date: 09-2076
Publisher: Elsevier BV
Date: 05-2012
Publisher: Elsevier BV
Date: 2020
Publisher: FapUNIFESP (SciELO)
Date: 06-2002
DOI: 10.1590/S0001-37652002000200008
Abstract: Laser heating 40Ar/39Ar geochronology provides high analytical precision and accuracy, mum-scale spatial resolution, and statistically significant data sets for the study of geological and planetary processes. A newly commissioned 40Ar/39Ar laboratory at CPGeo/USP, São Paulo, Brazil, equips the Brazilian scientific community with a new powerful tool applicable to the study of geological and cosmochemical processes. Detailed information about laboratory layout, environmental conditions, and instrumentation provides the necessary parameters for the evaluation of the CPGeo/USP 40Ar/39Ar suitability to a erse range of applications. Details about analytical procedures, including mineral separation, irradiation at the IPEN/CNEN reactor at USP, and mass spectrometric analysis enable potential researchers to design the necessary s ling and s le preparation program suitable to the objectives of their study. Finally, the results of calibration tests using Ca and K salts and glasses, international mineral standards, and in-house mineral standards show that the accuracy and precision obtained at the 40Ar/39Ar laboratory at CPGeo/USP are comparable to results obtained in the most respected laboratories internationally. The extensive calibration and standardization procedures undertaken ensure that the results of analytical studies carried out in our laboratories will gain immediate international credibility, enabling Brazilian students and scientists to conduct forefront research in earth and planetary sciences.
Publisher: Geological Society of America
Date: 08-2010
DOI: 10.1130/G30919.1
Publisher: Elsevier BV
Date: 04-2007
Publisher: Mineralogical Society of America
Date: 10-2015
Publisher: Informa UK Limited
Date: 09-08-2023
Publisher: Informa UK Limited
Date: 31-07-2022
Publisher: Springer Science and Business Media LLC
Date: 26-01-2007
Publisher: Elsevier BV
Date: 08-2014
Publisher: Oxford University Press (OUP)
Date: 24-02-2022
DOI: 10.1093/PETROLOGY/EGAC015
Abstract: Eastern Australia encompasses the longest track (~2000 km) of age-progressive continental volcanoes on Earth. These so-called ‘central volcanoes’ are shield volcanoes considered as surficial expressions of Cenozoic mantle plume activity under the northward moving Australian continent. Here, we investigate three central volcanoes located in the southern, younger part of the volcanic track (Ebor, Nandewar, and Canobolas) with the aim of unraveling the plumbing system architecture during waning hotspot activity. We explore the duration of volcanic activity and compare long-term evolution of magmatic processes via 40Ar/39Ar geochronology, mineral and groundmass chemistry, mineral-melt thermobarometry, and Rhyolite-MELTS thermodynamic simulations. 40Ar/39Ar geochronology on groundmass and mineral separates indicates that Ebor is the oldest of the three volcanoes, with duration of at least ~1 Ma (20.4 ± 0.09 to 19.4 ± 0.07 Ma). Nandewar also lasted ~1 Ma (19.4 ± 0.03 to 18.5 ± 0.03 Ma). The Canobolas volcanic complex was younger and shorter lived at ~0.5 Ma (12.0 ± 0.02 to 11.55 ± 0.05 Ma). Interestingly, all three volcanoes share a repetitive tempo of ~0.1 Ma between eruptions. The volcanoes produced porphyritic to aphyric lavas with basalt to trachyte compositions. The phenocryst assemblage includes plagioclase and K-feldspar, pink and green clinopyroxene, rare olivine, and titanomagnetite. Textural and compositional zoning of phenocrysts reveals successive events of mafic replenishment and magma transport prior to eruption. Dissolution textures in plagioclase, coupled with increasing An and FeOt and decreasing Ba and Ce from crystal cores to mantles, indicate recharge with mafic, oxidised melt. Increasing Mg# and Cr from clinopyroxene cores to rims also supports primitive magma replenishment. Mineral–melt thermobarometry and Rhyolite–MELTS simulations indicate a main level of magma storage in the three volcanoes in the middle crust (18–25-km depth ~1100°C), repeatedly replenished by undegassed, primitive melts. Green clinopyroxene cores crystallised in isolated pockets where magmas underwent extensive fractionation at depths of 15 to 30 km and ~800°C. The shallow level plumbing system was volumetrically minor and dominated by crystallisation of low-An plagioclase with large melt inclusions, possibly crystallised from degassed, reduced and evolved magma, as suggested by plagioclase hygrometry and fO2 modelling. Our combined geochronological and geochemical approach reveals that the three spatially separated but genetically linked volcanoes had comparable, complex plumbing system architectures. Fractionation and repeated magma rejuvenation were critical processes throughout the lifespans of volcanism, and eruptive tempos were controlled by recurrent mafic influx. The maficity of lavas and their crystal cargo correlate with the volume fraction of phenocrysts, suggesting mafic recharge was a key driver of mush remobilisation and eruption. Other volcanoes active during the late stages of plume activity in eastern Australia share similar textural and geochemical features, suggesting that waning hotspot activity may result in increased complexity in magma transport and storage.
Publisher: Elsevier BV
Date: 05-2020
Publisher: University of Chicago Press
Date: 11-2003
DOI: 10.1086/378486
Publisher: Elsevier BV
Date: 03-2018
Publisher: Wiley
Date: 2004
DOI: 10.1002/ESP.1090
Publisher: Elsevier BV
Date: 2013
Publisher: Elsevier BV
Date: 10-2022
Publisher: Elsevier BV
Date: 02-2020
Publisher: Springer Science and Business Media LLC
Date: 16-08-2019
Publisher: Geological Society of South Africa
Date: 26-10-2020
Abstract: During the Grenvillian assembly of Rodinia, the Namaqua-Natal Metamorphic Province (NNMP) was formed as a result of the convergence of the Laurentia and Kalahari cratons. A detailed model for this accretion along the south-eastern margin of the Kalahari Craton has been established, but the tectonic history of the NNMP along the western margin of the Kalahari Craton has remained highly controversial. U-Pb SHRIMP zircon age dating of gneiss in the Kakamas Domain of the NNMP, as well as U-Pb SHRIMP age dating of detrital zircons and 40Ar/39Ar dating of metamorphic muscovite from sediments overlying the gneiss, confirms the presence of at least two separate events during the Namaqua-Natal Orogeny at ~1 166 Ma and 1 116 Ma. These events occurred after the Areachap Terrane was accreted onto the western margin of the Proto-Kalahari Craton during the Kheis Orogeny. 40Ar/39Ar ages derived from metamorphic muscovite formed in the metasediments of the Kheis terrane does not provide evidence for the timing of the Kheis Orogeny but suggests that it most likely only occurred after ~1 300 Ma and not at 1 800 Ma as commonly accepted. A U-Pb concordia age of ~1 166 Ma was derived from granitic gneiss in the Kakamas Domain of the Bushmanland Subprovince, possibly reflecting subduction and the initiation of continent-continent collision between the Proto-Kalahari Craton and the Bushmanland Subprovince. This granitic gneiss is nonconformably overlain by the metasediments of the Korannaland Group that contains metamorphic muscovite with 40Ar/39Ar ages of ~1 116 Ma. This age suggest that complete closure of the ocean between the Proto-Kalahari Craton and Bushmanland Subprovince probably occurred about 50 Ma after the intrusion of the ~1 166 Ma granitic gneisses.
Publisher: Elsevier BV
Date: 09-2005
Publisher: University of Chicago Press
Date: 11-2009
DOI: 10.1086/605779
Publisher: Mineralogical Society of America
Date: 10-2015
Publisher: American Geophysical Union (AGU)
Date: 02-2018
DOI: 10.1002/2017JF004282
Publisher: Elsevier BV
Date: 10-2018
Publisher: American Association for the Advancement of Science (AAAS)
Date: 30-09-2022
Abstract: The Perseverance rover landed in Jezero crater, Mars, to investigate ancient lake and river deposits. We report observations of the crater floor, below the crater's sedimentary delta, finding that the floor consists of igneous rocks altered by water. The lowest exposed unit, informally named Séítah, is a coarsely crystalline olivine-rich rock, which accumulated at the base of a magma body. Magnesium-iron carbonates along grain boundaries indicate reactions with carbon dioxide-rich water under water-poor conditions. Overlying Séítah is a unit informally named Máaz, which we interpret as lava flows or the chemical complement to Séítah in a layered igneous body. Voids in these rocks contain sulfates and perchlorates, likely introduced by later near-surface brine evaporation. Core s les of these rocks have been stored aboard Perseverance for potential return to Earth.
Publisher: Universidade Federal do Rio Grande do Sul
Date: 31-08-2010
Abstract: Crescimentos autigênicos precoces de K-feldspato são abundantes nos arenitos fluviais cretácicos da Formação Açu (Bacia Potiguar), um dos mais importantes reservatórios onshore de hidrocarbonetos do Brasil. Estes crescimentos foram formados diretamente ao redor de K-feldspatos detríticos, em condições superficiais (eodiagênese inicial). A continuidade física entre crescimentos e grãos detríticos impossibilitou sua separação visando a aplicação do método convencional 40K- 40Ar. Assim, optou-se em aplicar o método 40 39 Ar- Ar diretamente nos crescimentos autigênicos de K-feldspato. Como resultado, foi obtida uma idade mínima de 120 Ma, muito próxima à idade bioestratigráfica previamente estabelecida para os arenitos da Formação Açu, o que demonstra a viabilidade da aplicação do método 40Ar- 39Ar na determinação de idades deposicionais de arenitos-reservatório. Entretanto, para fins de aprimoramento do método e melhor precisão nas idades, é sugerido o uso de equipamentos que utilizam sonda a laser ultravioleta (UV), o que reduz a possibilidade de contaminação por diferentes fases minerais.
Publisher: Elsevier BV
Date: 08-1991
Publisher: Informa UK Limited
Date: 08-2008
Publisher: Springer Science and Business Media LLC
Date: 18-06-2020
DOI: 10.1038/S41598-020-66830-Z
Abstract: Robust methods for the characterisation of microbial biosignatures in geological matrices is critical for developing mineralogical biosignatures. Studying microbial fossils is fundamental for our understanding of the role microorganisms have played in elemental cycling in modern and ancient environments on Earth and potentially Mars. Here, we aim to understand what promotes the fossilisation of microorganisms after the initial stages of biomineralisation, committing bacteriomorphic structures to the geological record within iron-rich environments. Mineral encrusted cell envelope structures were routinely identified within a goethite-rich vein that cross-cut the saprolite (iron ore) of a weathered banded iron formation (BIF) system in the Quadrilátero Ferrífero, Brazil. The preservation of potential organic and mineralogical biosignatures associated with these fossils was characterised using the following high-resolution analytical techniques: scanning and transmission electron microscopy, focused ion beam scanning electron microscopy, nanoscale secondary ion mass spectrometry, synchrotron-based Fourier transform infrared spectroscopy and Raman spectroscopy. Electron microscopy demonstrated that mineral nucleation associated with a range of cell envelope structures typically followed the extant cell templates. These biologically-influenced iron-rich minerals are microcrystalline with minimal secondary growth. In contrast, intracellular mineralisation formed larger minerals that grew inward from the cell membrane to infill intracellular voids after cell death. A three dimensional reconstruction of encrusted cell envelopes in a fossilised biofilm suggests that microorganisms may be able to replicate, during the initial stages of mineralisation. Carbon and nitrogen signatures are preserved associated with the cell envelope structures however, there were no conclusive mineralogical biosignatures associated with the mineralised cell envelopes highlighting the classical importance of morphology and elemental biosignatures in determining the biogenicity of bacteriomorphic structures.
Publisher: Geological Society of America
Date: 2007
DOI: 10.1130/G23755Y.1
Publisher: Science China Press., Co. Ltd.
Date: 2002
DOI: 10.1360/02TB9331
Publisher: Geological Society of America
Date: 04-08-2017
DOI: 10.1130/G38989.1
Publisher: Geological Society of America
Date: 07-2020
DOI: 10.1130/B35560.1
Abstract: The 40Ar/39Ar dating method is among the most versatile of geochronometers, having the potential to date a broad variety of K-bearing materials spanning from the time of Earth’s formation into the historical realm. Measurements using modern noble-gas mass spectrometers are now producing 40Ar/39Ar dates with analytical uncertainties of ∼0.1%, thereby providing precise time constraints for a wide range of geologic and extraterrestrial processes. Analyses of increasingly smaller subs les have revealed age dispersion in many materials, including some minerals used as neutron fluence monitors. Accordingly, interpretive strategies are evolving to address observed dispersion in dates from a single s le. Moreover, inferring a geologically meaningful “age” from a measured “date” or set of dates is dependent on the geological problem being addressed and the salient assumptions associated with each set of data. We highlight requirements for collateral information that will better constrain the interpretation of 40Ar/39Ar data sets, including those associated with single-crystal fusion analyses, incremental heating experiments, and in situ analyses of micros led domains. To ensure the utility and viability of published results, we emphasize previous recommendations for reporting 40Ar/39Ar data and the related essential metadata, with the amendment that data conform to evolving standards of being findable, accessible, interoperable, and reusable (FAIR) by both humans and computers. Our ex les provide guidance for the presentation and interpretation of 40Ar/39Ar dates to maximize their interdisciplinary usage, reproducibility, and longevity.
Publisher: FapUNIFESP (SciELO)
Date: 12-2007
DOI: 10.1590/S0001-37652007000400011
Abstract: This paper presents 40Ar/39Ar ages of the rocks from the Serra do Azeite transtensional shear zone in the southern part of the Ribeira belt, between the States of São Paulo and Paraná, and also discusses the regional correlations and the tectonic implications for other parts of the belt. The geochronological data suggest that transtensional deformation was active between 600 and 580 Ma (hornblende and muscovite apparent ages, respectively). This time span is considerably older than previous proposals for the period of activity of these structures (520-480 Ma) in the northern segment of this belt and in the Araçuaí belt. Kinematic analysis of the dated mylonites shows extensional structures with top-down movement to ESE compatible with structures found in other tectonic segments in the eastern portion of the Quadrilátero Ferrífero and in the Rio Doce Valley region. Our ages are situated in the same time interval defined for the alkaline magmatism of the Serra do Mar suite. We suggest that the regional tectonic framework was developed during continental-scale extension. This process has been coeval with convergent strain in the adjacent Neoproterozoic shear zones of the Apiaí/Ribeira and Araçuaí belts, which make up significant segments of these belts. The available data show that these structures may not be simply related to post-orogenic gravitational collapse, but must involve a more complex process probably related to dynamic balance between crustal thickening and thinning during tectonic convergence, basin formation and exhumation processes.
Publisher: Elsevier BV
Date: 11-2007
Publisher: Elsevier BV
Date: 03-2014
Publisher: Wiley
Date: 19-08-2020
Publisher: American Association for the Advancement of Science (AAAS)
Date: 16-10-1992
DOI: 10.1126/SCIENCE.258.5081.451
Abstract: Supergene cryptomelane [K(1-2)(Mn(3+)Mn(4+))(8)O(16). chiH(2)O] s les from deeply weathered pegmatites in southeastern Brazil subjected to (40)K-(40)Ar and (40)Ar/(39)Ar analysis yielded (40)K-(40)Ar dates ranging from 10.1 +/- 0.5 to 5.6 +/- 0.2 Ma (million years ago). Laser-probe (40)Ar/(39)Ar step-heating of the two most disparate s les yielded plateau dates of 9.94 +/- 0.05 and 5.59 +/- 0.10 Ma, corresponding, within 2 sigma, to the (40)K-(40)Ar dates. The results imply that deep weathering profiles along the eastern Brazilian margin do not reflect present climatic conditions but are the result of a long-term process that was already advanced by the late Miocene. Weathering ages predate pulses of continental sedimentation along the eastern Brazilian margin and suggest that there was a time lag between weathering and erosion processes and sedimentation processes.
Publisher: Elsevier BV
Date: 04-2014
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 06-2002
Publisher: American Association for the Advancement of Science (AAAS)
Date: 24-01-2014
Abstract: Sedimentary rocks examined by the Curiosity rover at Yellowknife Bay, Mars, were derived from sources that evolved from an approximately average martian crustal composition to one influenced by alkaline basalts. No evidence of chemical weathering is preserved, indicating arid, possibly cold, paleoclimates and rapid erosion and deposition. The absence of predicted geochemical variations indicates that magnetite and phyllosilicates formed by diagenesis under low-temperature, circumneutral pH, rock-dominated aqueous conditions. Analyses of diagenetic features (including concretions, raised ridges, and fractures) at high spatial resolution indicate that they are composed of iron- and halogen-rich components, magnesium-iron-chlorine–rich components, and hydrated calcium sulfates, respectively. Composition of a cross-cutting dike-like feature is consistent with sedimentary intrusion. The geochemistry of these sedimentary rocks provides further evidence for erse depositional and diagenetic sedimentary environments during the early history of Mars.
Publisher: Elsevier BV
Date: 07-2008
Publisher: Elsevier BV
Date: 10-2012
Publisher: Informa UK Limited
Date: 02-2007
Publisher: Japanese Society of Microbial Ecology
Date: 2018
Publisher: Elsevier BV
Date: 04-2010
Publisher: Universidade de Sao Paulo, Agencia USP de Gestao da Informacao Academica (AGUIA)
Date: 04-2004
Publisher: American Geophysical Union (AGU)
Date: 09-2013
DOI: 10.1002/TECT.20084
Publisher: Geological Society of America
Date: 2007
Publisher: American Association for the Advancement of Science (AAAS)
Date: 24-01-2014
Abstract: We determined radiogenic and cosmogenic noble gases in a mudstone on the floor of Gale Crater. A K-Ar age of 4.21 ± 0.35 billion years represents a mixture of detrital and authigenic components and confirms the expected antiquity of rocks comprising the crater rim. Cosmic-ray–produced 3 He, 21 Ne, and 36 Ar yield concordant surface exposure ages of 78 ± 30 million years. Surface exposure occurred mainly in the present geomorphic setting rather than during primary erosion and transport. Our observations are consistent with mudstone deposition shortly after the Gale impact or possibly in a later event of rapid erosion and deposition. The mudstone remained buried until recent exposure by wind-driven scarp retreat. Sedimentary rocks exposed by this mechanism may thus offer the best potential for organic biomarker preservation against destruction by cosmic radiation.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 24-01-2014
Abstract: Sedimentary rocks at Yellowknife Bay (Gale crater) on Mars include mudstone s led by the Curiosity rover. The s les, John Klein and Cumberland, contain detrital basaltic minerals, calcium sulfates, iron oxide or hydroxides, iron sulfides, amorphous material, and trioctahedral smectites. The John Klein smectite has basal spacing of ~10 angstroms, indicating little interlayer hydration. The Cumberland smectite has basal spacing at both ~13.2 and ~10 angstroms. The larger spacing suggests a partially chloritized interlayer or interlayer magnesium or calcium facilitating H 2 O retention. Basaltic minerals in the mudstone are similar to those in nearby eolian deposits. However, the mudstone has far less Fe-forsterite, possibly lost with formation of smectite plus magnetite. Late Noachian/Early Hesperian or younger age indicates that clay mineral formation on Mars extended beyond Noachian time.
Publisher: Virtual Explorer Pty Ltd.
Date: 2004
Publisher: Elsevier BV
Date: 10-2018
Publisher: FapUNIFESP (SciELO)
Date: 06-2018
Publisher: FapUNIFESP (SciELO)
Date: 08-03-2018
Publisher: Annual Reviews
Date: 05-1999
DOI: 10.1146/ANNUREV.EARTH.27.1.183
Abstract: ▪ Abstract Recent developments in the application of K-Ar and 40 Ar/ 39 Ar dating of continental weathering process demonstrate the method's suitability for dating minerals present in weathering profiles. Alunite-group sulfates and hollandite-group manganese oxides, which often precipitate through weathering reactions, were first analyzed by the K-Ar method 30 years ago. Recently these minerals were shown to be suitable to 40 Ar/ 39 Ar geochronology, despite their fine-grained habits. The bulk nature of the K-Ar technique and the complex mineral assemblages in weathering profiles restrict K-Ar dating of weathering processes. The single-crystal approach possible with the 40 Ar/ 39 Ar method allows the study of weathering profiles where alunite- and hollandite-group minerals occur as minor phases. Step-heating analysis possible with the 40 Ar/ 39 Ar method provides information about the Ar and K retention histories, the presence of hypogene contaminants, and possible 39 Ar recoil during s le irradiation. Fully automated, modern 40 Ar/ 39 Ar systems enable analysis of several s les, providing a comprehensive weathering database. These results are useful in the study of continental paleoclimates and the geochemical, geomorphological, and tectonic histories of an area.
Publisher: American Geophysical Union (AGU)
Date: 12-2017
DOI: 10.1002/2017JE005445
Abstract: Following K‐Ar dating of a mudstone and a sandstone, a third s le has been dated by the Curiosity rover exploring Gale Crater. The Mojave 2 mudstone, which contains relatively abundant jarosite, yielded a young K‐Ar bulk age of 2.57 ± 0.39 Ga (1 σ precision). A two‐step heating experiment was implemented in an effort to resolve the K‐Ar ages of primary and secondary mineralogical components within the s le. This technique involves measurement of 40 Ar released in low‐temperature (500°C) and high‐temperature (930°C) steps, and a model of the potassium distribution within the mineralogical components of the s le. Using this method, the high‐temperature step yields a K‐Ar model age of 4.07 ± 0.63 Ga associated with detrital plagioclase, compatible with the age obtained on the Cumberland mudstone by Curiosity. The low‐temperature step, associated with jarosite mixed with K‐bearing evaporites and/or phyllosilicates, gave a youthful K‐Ar model age of 2.12 ± 0.36 Ga. The interpretation of this result is complicated by the potential for argon loss after mineral formation. Comparison with the results on Cumberland and previously published constraints on argon retentivity of the in idual phases likely to be present suggests that the formation age of the secondary materials, correcting for plausible extents of argon loss, is still less than 3 Ga, suggesting post‐3 Ga aqueous processes occurred in the sediments in Gale Crater. Such a result is inconsistent with K‐bearing mineral formation in Gale Lake and instead suggests postdepositional fluid flow at a time after surface fluvial activity on Mars is thought to have largely ceased.
Publisher: Elsevier BV
Date: 1994
Publisher: Elsevier BV
Date: 2021
Publisher: Elsevier BV
Date: 03-2020
DOI: 10.1016/J.SCITOTENV.2019.136128
Abstract: Microbial biofilms growing in iron-rich seeps surrounding Lake Violão, Carajás, Brazil serve as a superb natural system to study the role of iron cycling in producing secondary iron cements. These seeps flow across iron duricrusts (referred to as canga in Brazil) into hydraulically restricted lakes in northern Brazil. Canga caps all of the iron ore deposits in Brazil, protecting them from being destroyed by erosion in this active weathering environment. Biofilm s les collected from these seeps demonstrated heightened biogeochemical iron cycling, contributing to the relatively rapid, seasonal formation of iron-rich cements. The seeps support iron-oxidising lineages including Sideroxydans, Gallionella, and an Azoarcus species revealed by 16S rRNA gene sequencing. In contrast, a low relative abundance of putative iron reducers for ex le, Geobacter species (<5% of total sequences in any s le), corresponds to carbon limitation in this canga-associated ecosystem. This carbon limitation is likely to restrict anoxic niches to within biofilms. Examination of a canga rock s le collected from the edge of Lake Violão revealed an array of well- to poorly-preserved microbial fossils in secondary iron cements. These heterogeneous cements preserved bacterial cell envelopes and possibly extracellular polymeric substances within the microfossil iron-rich cements (termed biocements). Bacterial iron reduction initiates the sequence, and intuitively is the rate-limiting step in this broadly aerobic environment. The organic framework of the active- and paleo-biofilms appears to provide a scaffold for the formation of some cements within canga and likely expedites cement formation. The accelerated development of these resilient iron-rich biocements in the lake edge environment compared with surroundings duricrust-associated environments may provide insights into new approaches to remediate mined land, aiding to stabilise slopes, reduce erosion, restore functional hydrogeology and provide a substrate akin to natural canga for revegetation using endemic canga plant species, which have adapted to grow on iron-rich substrates.
Publisher: American Geophysical Union (AGU)
Date: 07-2014
DOI: 10.1002/2013TC003426
Publisher: Oxford University Press (OUP)
Date: 06-2018
Publisher: Elsevier BV
Date: 12-2013
Publisher: Elsevier BV
Date: 05-2019
Publisher: Elsevier BV
Date: 12-2003
Publisher: Elsevier BV
Date: 06-2020
Publisher: Elsevier BV
Date: 09-2013
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 2021
Publisher: Geological Society of America
Date: 2006
DOI: 10.1130/G22003.1
Publisher: Elsevier BV
Date: 09-2022
Publisher: Sociedade Brasileira de Geologia
Date: 03-2012
Publisher: Elsevier BV
Date: 03-2014
Publisher: American Geophysical Union (AGU)
Date: 10-2016
DOI: 10.1002/2016JE005017
Publisher: Springer Science and Business Media LLC
Date: 20-09-2008
Publisher: Elsevier BV
Date: 10-2006
Publisher: FapUNIFESP (SciELO)
Date: 06-2014
Publisher: American Association for the Advancement of Science (AAAS)
Date: 24-01-2014
Abstract: The Curiosity rover discovered fine-grained sedimentary rocks, which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy. This aqueous environment was characterized by neutral pH, low salinity, and variable redox states of both iron and sulfur species. Carbon, hydrogen, oxygen, sulfur, nitrogen, and phosphorus were measured directly as key biogenic elements by inference, phosphorus is assumed to have been available. The environment probably had a minimum duration of hundreds to tens of thousands of years. These results highlight the biological viability of fluvial-lacustrine environments in the post-Noachian history of Mars.
Publisher: Elsevier BV
Date: 08-2019
Publisher: Elsevier BV
Date: 07-2012
Publisher: Elsevier BV
Date: 09-2021
Publisher: Elsevier BV
Date: 04-2018
Publisher: Geological Society of America
Date: 27-01-2017
DOI: 10.1130/GES01405.1
Publisher: American Association for the Advancement of Science (AAAS)
Date: 27-09-2013
Abstract: The ChemCam instrument, which provides insight into martian soil chemistry at the submillimeter scale, identified two principal soil types along the Curiosity rover traverse: a fine-grained mafic type and a locally derived, coarse-grained felsic type. The mafic soil component is representative of widespread martian soils and is similar in composition to the martian dust. It possesses a ubiquitous hydrogen signature in ChemCam spectra, corresponding to the hydration of the amorphous phases found in the soil by the CheMin instrument. This hydration likely accounts for an important fraction of the global hydration of the surface seen by previous orbital measurements. ChemCam analyses did not reveal any significant exchange of water vapor between the regolith and the atmosphere. These observations provide constraints on the nature of the amorphous phases and their hydration.
Publisher: Geological Society of London
Date: 03-2012
Publisher: Elsevier BV
Date: 12-2016
Publisher: Elsevier BV
Date: 2006
Publisher: Informa UK Limited
Date: 06-02-2022
Publisher: Elsevier BV
Date: 10-2008
Publisher: Elsevier BV
Date: 12-2016
Publisher: Springer Science and Business Media LLC
Date: 31-03-2021
Publisher: Elsevier BV
Date: 09-2019
Publisher: Elsevier BV
Date: 06-2022
Publisher: Society of Economic Geologists
Date: 08-2006
Location: United States of America
No related grants have been discovered for Paulo Marcos Vasconcelos.