ORCID Profile
0000-0003-2227-577X
Current Organisation
Naturhistoriska riksmuseet
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Artificial Intelligence and Image Processing not elsewhere classified | Geology | Geochronology | Extraterrestrial Geology
Expanding Knowledge in the Earth Sciences | Education and Training not elsewhere classified | Expanding Knowledge in Technology |
Publisher: Geological Society of London
Date: 2010
DOI: 10.1144/SP335.5
Publisher: Geological Society of America
Date: 03-2013
DOI: 10.1130/G33920.1
Publisher: Cambridge University Press (CUP)
Date: 2008
DOI: 10.1017/S0263593300001498
Abstract: The relationship between plutonic and volcanic rocks is central to understanding the geochemical evolution of silicic magma systems, but it is clouded by ambiguities associated with unravelling the plutonie record. Here we report an integrated U-Pb, O and Lu-Hf isotope study of zircons from three putative granitic-volcanic rock pairs from the Lachlan Fold Belt, southeastern Australia, to explore the connection between the intrusive and extrusive realms. The data reveal contrasting petrogenetic scenarios for the S- and I-type pairs. The zircon Hf-O isotope systematics in an 1-type dacite are very similar to those of their plutonie counterpart, supporting an essentially co-magmatic relationship between these units. The elevated δ 18 O of zircons in these I-type rocks confirm a significant supracrustal source component. The S-type volcanic rocks are not the simple erupted equivalents of the granites, although the extrusive and plutonie units can be related by open-system magmatic evolution. Zircons in the S-type rocks define covariant ε Ηf — β O arrays that attest to mixing or assimilation processes between two components, one being the Ordovician metasedimentary country rocks, the other either an I-type magma or a mantle-derived magma. The data are consistent with models involving incremental melt extraction from relatively juvenile magmas undergoing open-system differentiation at depth, followed by crystal-liquid mixing upon emplacement in shallow magma reservoirs, or upon eruption. The latter juxtaposes crystals with markedly different petrogenetic histories and determines whole-rock geochemical and textural properties. This scenario can explain the puzzling decoupling between the bulk rock isotope and geochemical compositions commonly observed for granite suites.
Publisher: GeoScienceWorld
Date: 02-2010
DOI: 10.1130/L80.1
Publisher: Springer Science and Business Media LLC
Date: 24-01-2020
DOI: 10.1038/S41467-019-14110-4
Abstract: Sulfur belongs among H 2 O, CO 2 , and Cl as one of the key volatiles in Earth’s chemical cycles. High oxygen fugacity, sulfur concentration, and δ 34 S values in volcanic arc rocks have been attributed to significant sulfate addition by slab fluids. However, sulfur speciation, flux, and isotope composition in slab-dehydrated fluids remain unclear. Here, we use high-pressure rocks and enclosed veins to provide direct constraints on subduction zone sulfur recycling for a typical oceanic lithosphere. Textural and thermodynamic evidence indicates the predominance of reduced sulfur species in slab fluids those derived from metasediments, altered oceanic crust, and serpentinite have δ 34 S values of approximately −8‰, −1‰, and +8‰, respectively. Mass-balance calculations demonstrate that 6.4% (up to 20% maximum) of total subducted sulfur is released between 30–230 km depth, and the predominant sulfur loss takes place at 70–100 km with a net δ 34 S composition of −2.5 ± 3‰. We conclude that modest slab-to-wedge sulfur transport occurs, but that slab-derived fluids provide negligible sulfate to oxidize the sub-arc mantle and cannot deliver 34 S-enriched sulfur to produce the positive δ 34 S signature in arc settings. Most sulfur has negative δ 34 S and is subducted into the deep mantle, which could cause a long-term increase in the δ 34 S of Earth surface reservoirs.
Publisher: Elsevier BV
Date: 04-2009
Publisher: Elsevier BV
Date: 10-2018
Publisher: Public Library of Science (PLoS)
Date: 25-06-2014
Publisher: Elsevier BV
Date: 07-2019
Publisher: Elsevier BV
Date: 06-2017
Publisher: Springer Science and Business Media LLC
Date: 07-01-2003
Publisher: Informa UK Limited
Date: 30-03-2017
Publisher: Elsevier BV
Date: 10-2006
Publisher: Elsevier BV
Date: 05-2018
Publisher: Elsevier BV
Date: 02-2016
Publisher: Geological Society of London
Date: 2001
Publisher: Wiley
Date: 07-12-2015
DOI: 10.1111/MAPS.12572
Publisher: Informa UK Limited
Date: 13-06-2018
Publisher: Elsevier BV
Date: 05-2011
Publisher: Springer Science and Business Media LLC
Date: 21-03-2022
Publisher: Springer Science and Business Media LLC
Date: 17-11-2021
Publisher: Elsevier BV
Date: 09-2017
Publisher: Geological Society of London
Date: 12-2005
Publisher: Elsevier BV
Date: 06-2018
Publisher: Geological Society of America
Date: 28-04-2016
DOI: 10.1130/G37898.1
Publisher: Elsevier BV
Date: 04-2011
Publisher: Elsevier BV
Date: 10-2023
Publisher: Elsevier BV
Date: 02-2008
Publisher: Elsevier BV
Date: 02-2020
Publisher: Elsevier BV
Date: 04-2014
Publisher: Wiley
Date: 21-12-2006
DOI: 10.1111/J.1472-4669.2006.00091.X
Abstract: We report in situ secondary ion mass spectrometer sulphur isotope data for sedimentary pyrite from the 2.52 Ga Upper C bellrand Subgroup, Transvaal, South Africa. The analysed sedimentary rocks represent a transition in depositional environment from very shallow to deeper water, with strong sedimentological, facies distribution and geochemical evidence for the presence of a shallow redox chemocline. Data were obtained directly in thin section in order to preserve petrographic context. They reveal a very large extent of isotopic fractionation both in mass‐independent (MIF) and in mass‐dependent fractionation (MDF) on unprecedentedly small scale. In the shallow‐water microbical carbonates, three types of pyrite were identified. The texturally oldest pyrite is found as small, isotopically little fractionated grains in the microbial mats. Large (several mm) spheroidal pyrite concretions, which postdate the mat pyrite, record strong evidence for an origin by bacterial sulphate reduction. Rare pyrite surrounding late fenestral calcite is inferred to have formed from recycled bacterial pyrite on account of the slope of its correlated MIF and MDF array. This latter type of pyrite was also found in an interbedded black shale and a carbonate laminite. In a deeper water chert, pyrite with very heavy sulphur indicates partial to almost complete sulphate reduction across a chemocline whose existence has been inferred independently. The combined picture from all the studied s les is that of a sulphate availability‐limited environment, in which sulphur was cycled between reservoirs according to changing redox conditions established across the chemocline. Cycling apparently reduced the extent of recorded sulphur isotope fractionation relative to what is expected from projection in the correlated MIF and MDF arrays. This is consistent with regionally relatively high free oxygen concentrations in the shallow water, permitting locally strong MDF. Our new observations add to the growing evidence for a complex, fluctuating evolution of free atmospheric oxygen between c . 2.7 Ga and 2.3 Ga.
Publisher: Elsevier BV
Date: 12-2005
Publisher: Wiley
Date: 25-10-2016
DOI: 10.1111/MAPS.12740
Publisher: Elsevier BV
Date: 2016
Publisher: Elsevier BV
Date: 03-2005
Publisher: Elsevier BV
Date: 03-2019
Publisher: Springer Science and Business Media LLC
Date: 27-05-2012
Publisher: Wiley
Date: 30-03-2021
DOI: 10.1111/GGR.12377
Publisher: Geological Society of London
Date: 2000
Publisher: Cambridge University Press (CUP)
Date: 21-09-2007
DOI: 10.1017/S0016756807003858
Abstract: Dating the pre-Middle Ordovician metavolcanic rocks and metagranites of the Ollo de Sapo Domain has, historically, been difficult because of the small compositional variation, the effects of the Variscan orogeny and, as revealed in this paper, the unusually high fraction of inherited zircon components. The first reliable zircon data (U–Pb ion microprobe and Pb–Pb stepwise evaporation) indicate that the Ollo de Sapo volcanism spanned 495±5 Ma to 483±3 Ma, and was followed by the intrusion of high-level granites from 483±3 Ma to 474±4 Ma. In both metavolcanic rocks and metagranites, no less than 70–80% of zircon grains are either totally Precambrian or contain a Precambrian core overgrown by a Cambro-Ordovician rim. About 80–90% of inherited zircons are Early Ediacaran (602–614 Ma) and derived from calc-alkaline intermediate to felsic igneous rocks generated at the end of the Pan-African arc–continent collision. In the Villadepera region, located to the west, both the metagranites and metavolcanic rocks also contain Meso-Archaean zircons (3.0–3.2 Ga) which ultimately originated from the West African Craton. In the Hiendelaencina region, located to the east, both the metagranites and metavolcanic rocks lack Meso-Archaean zircons, but they have two different inherited zircon populations, one Cryogenian (650–700 Ma) and the other Tonian (850–900 Ma), which suggest older-than-Ediacaran additional island-arc components. The different proportion of source components and the marked variation of the 87 Sr/ 86 Sr init. suggest, at least tentatively, that the across-arc polarity of the remnants of the Pan-African arc of Iberia trended east–west (with respect to the current coordinates) during Cambro-Ordovician times, and that the passive margin was situated to the west.
Publisher: Elsevier BV
Date: 09-2017
Publisher: Springer Science and Business Media LLC
Date: 12-08-2005
Publisher: Geological Society of America
Date: 12-2010
DOI: 10.1130/G31329.1
Publisher: Springer Science and Business Media LLC
Date: 30-08-2012
Publisher: Springer Science and Business Media LLC
Date: 16-11-2017
Publisher: Elsevier BV
Date: 09-2018
Publisher: Springer Science and Business Media LLC
Date: 02-04-2009
Publisher: Geological Society of America
Date: 2008
Publisher: Geological Society of London
Date: 24-05-2013
DOI: 10.1144/JGS2012-106
Publisher: Geological Society of America
Date: 21-07-2016
DOI: 10.1130/G38239Y.1
Publisher: Elsevier BV
Date: 12-2016
Publisher: Mary Ann Liebert Inc
Date: 10-2015
Abstract: The age and origin of the quartz- hibole-pyroxene (qap) gneiss from the island of Akilia, southern West Greenland, have been the subject of intense debate since the light C-isotope composition of graphite inclusions in apatite was interpreted to indicate the presence of Earth's earliest biological activity. Although this claim for biogenic relicts has been vigorously challenged, the possibility that the rocks might represent some of Earth's earliest water-lain sediments and, hence, a suitable repository for life remains an open question. While some workers have suggested that the entire sequence represents an originally mafic-ultramafic igneous precursor subsequently modified by metasomatism, quartz injection, high-grade metamorphism, and extreme ductile deformation, others maintain that at least a small part of the sequence retains geochemical characteristics indicative of a chemical sedimentary origin. Fractionated Fe isotopes with δ(56)Fe values similar to those observed in Isua BIF have been reported from high-SiO2 units of qap and used to support a chemical sedimentary protolith for the qap unit. Here, we present new Fe isotope data from all lithologic variants in the qap gneiss on Akilia, including layers of undisputed ultramafic igneous origin. Since the latter require introduction of fractionated Fe into at least part of the qap unit, we argue that Fe isotopes must therefore be treated with considerable caution when used to infer BIF for part or all of the qap protolith.
Publisher: American Geophysical Union (AGU)
Date: 12-2015
DOI: 10.1002/2015JE004809
Publisher: Informa UK Limited
Date: 27-04-2017
Publisher: Elsevier BV
Date: 04-2008
Publisher: Wiley
Date: 20-11-2014
DOI: 10.1111/MAPS.12395
Publisher: Elsevier BV
Date: 11-2018
Publisher: Elsevier BV
Date: 2008
Publisher: Elsevier BV
Date: 04-2009
Publisher: Geological Society of London
Date: 07-2012
Publisher: Wiley
Date: 17-02-2017
DOI: 10.1111/MAPS.12835
Publisher: Elsevier BV
Date: 10-2016
Publisher: Elsevier BV
Date: 2016
Publisher: Springer Science and Business Media LLC
Date: 1
DOI: 10.1038/35051550
Abstract: No crustal rocks are known to have survived since the time of the intense meteor bombardment that affected Earth between its formation about 4,550 Myr ago and 4,030 Myr, the age of the oldest known components in the Acasta Gneiss of northwestern Canada. But evidence of an even older crust is provided by detrital zircons in metamorphosed sediments at Mt Narryer and Jack Hills in the Narryer Gneiss Terrane, Yilgarn Craton, Western Australia, where grains as old as approximately 4,276 Myr have been found. Here we report, based on a detailed micro-analytical study of Jack Hills zircons, the discovery of a detrital zircon with an age as old as 4,404+/-8 Myr--about 130 million years older than any previously identified on Earth. We found that the zircon is zoned with respect to rare earth elements and oxygen isotope ratios (delta18O values from 7.4 to 5.0%), indicating that it formed from an evolving magmatic source. The evolved chemistry, high delta18O value and micro-inclusions of SiO2 are consistent with growth from a granitic melt with a delta18O value from 8.5 to 9.5%. Magmatic oxygen isotope ratios in this range point toward the involvement of supracrustal material that has undergone low-temperature interaction with a liquid hydrosphere. This zircon thus represents the earliest evidence for continental crust and oceans on the Earth.
Publisher: Geological Society of America
Date: 02-10-2017
DOI: 10.1130/G39328.1
Publisher: Society of Economic Geologists
Date: 06-2011
Publisher: Elsevier BV
Date: 04-2019
Publisher: Elsevier BV
Date: 04-2018
Publisher: University of Chicago Press
Date: 2007
DOI: 10.1086/509247
Publisher: Elsevier BV
Date: 12-2002
Publisher: American Geophysical Union (AGU)
Date: 09-2013
DOI: 10.1002/TECT.20071
Publisher: Geological Society of America
Date: 03-2007
DOI: 10.1130/B25891.1
Publisher: Springer Science and Business Media LLC
Date: 05-2023
DOI: 10.1007/S00410-023-02014-Y
Abstract: The Karoo large igneous province has been ided into rift zone and basin-related groups, with picrites from the Luenha river, Mozambique, representing an end-member of the latter. New O isotope, major and trace element data for olivine have been combined with MELTS crystallisation modelling to deconvolve compositional ersity associated with magma differentiation from source-derived heterogeneity. Three olivines populations have been discerned as follows: (1) the ‘main trend’, which records crystallisation from a variety of magma compositions (2) the ‘low Cu trend’, which is inferred to represent xenocrysts or antecrysts and (3) the ‘high CaO’ olivines, which record polybaric crystallisation of a primitive, little fractionated magma. The trace element variability in olivine phenocrysts relates partially to s ling of different parts of the same overall magma transport and storage systems, and partly to heterogeneity of parental magmas and their mantle sources. When the measured δ 18 O olivine values have been converted into δ 18 O melt values, the mean δ 18 O melt values for the ‘main trend’ and ‘low Cu’ groups are indistinguishable from each other (5.7 ± 0.1‰, 2σ) however, the mean δ 18 O melt value of 6.1 ± 0.1‰ for the ‘high CaO’ group is distinctly enriched. These data record source heterogeneity and suggest contributions from two mantle sources, one with elevated δ 18 O, and another with more ‘typical’ mantle δ 18 O. Combining these data with previously reported trace element and Nd and Sr isotope data support derivation from a mantle source similar to non-chondritic bulk silicate earth, but with minor contributions (1–2% for the enriched magmas) from a recycled sedimentary component. This points to the importance of a primitive mantle source for the basin-related successions in Karoo.
Publisher: Copernicus GmbH
Date: 30-10-2019
Publisher: Elsevier BV
Date: 10-2017
Publisher: Geological Society of America
Date: 2008
DOI: 10.1130/G24861A.1
Publisher: Geological Society of London
Date: 30-07-2020
DOI: 10.1144/JGS2020-034
Publisher: Geological Society of America
Date: 03-04-2015
DOI: 10.1130/B31213.1
Publisher: Wiley
Date: 08-08-2013
Publisher: Elsevier BV
Date: 03-1997
Publisher: Elsevier BV
Date: 03-2012
Publisher: Elsevier BV
Date: 2018
Publisher: The Royal Society
Date: 05-05-2006
Abstract: At greater than 3.7 Gyr, Earth's oldest known supracrustal rocks, comprised dominantly of mafic igneous with less common sedimentary units including banded iron formation (BIF), are exposed in southwest Greenland. Regionally, they were intruded by younger tonalites, and then both were intensely dynamothermally metamorphosed to granulite facies (the highest pressures and temperatures generally encountered in the Earth's crust during metamorphism) in the Archaean and subsequently at lower grades until about 1500 Myr ago. Claims for the first preserved life on Earth have been based on the occurrence of greater than 3.8 Gyr isotopically light C occurring as graphite inclusions within apatite crystals from a 5 m thick purported BIF on the island of Akilia. Detailed geologic mapping and observations there indicate that the banding, first claimed to be depositional, is clearly deformational in origin. Furthermore, the mineralogy of the supposed BIF, being dominated by pyroxene, hibole and quartz, is unlike well-known BIF from the Isua Greenstone Belt (IGB), but resembles enclosing mafic and ultramafic igneous rocks modified by metasomatism and repeated metamorphic recrystallization. This scenario parsimoniously links the geology, whole-rock geochemistry, 2.7 Gyr single crystal zircon ages in the unit, an approximately 1500 Myr age for apatites that lack any graphite, non-MIF sulphur isotopes in the unit and an inconclusive Fe isotope signature. Although both putative body fossils and carbon-12 enriched isotopes in graphite described at Isua are better explained by abiotic processes, more fruitful targets for examining the earliest stages in the emergence of life remain within greater than 3.7 Gyr IGB, which preserves BIF and other rocks that unambiguously formed at Earth's surface.
Publisher: Elsevier BV
Date: 09-2006
Publisher: Cambridge University Press (CUP)
Date: 24-10-2011
DOI: 10.1017/S001675681100080X
Abstract: Field observations from the Trinity Peninsula Group at View Point on the Antarctic Peninsula indicate that thick, southward-younging and overturned clastic sedimentary rocks, comprising unusually coarse conglomeratic lenses within a succession of fine-grained sandstone–mudstone couplets, are the deposits of debris and turbidity flows on or at the foot of a submarine slope. Three detrital zircons from the sandstone–mudstone couplets date deposition at 302 ± 3 Ma, at or shortly after the Carboniferous–Permian boundary. Conglomerates predominantly consist of quartzite and granite and contain boulders exceeding 500 mm in diameter. Zircons from granitoid clasts and a silicic volcanic clast yield U–Pb ages of 466 ± 3 Ma, 373 ± 5 Ma and 487 ± 4 Ma, respectively and have corresponding average εHf t values between +0.3 and +7.6. A quartzite clast, conglomerate matrix and sandstone interbedded with the conglomerate units have broadly similar detrital zircon age distributions and Hf isotope compositions. The clast and detrital zircon ages match well with sources within Patagonia however, the age of one granite clast and the εHf characteristics of some detrital zircons point to a lesser South Africa or Ellsworth Mountain-like contribution, and the quartzite and granite-dominated composition of the conglomerates is similar to upper Palaeozoic diamictites in the Ellsworth Mountains. Unlike detrital zircons, large conglomerate clasts limit possible transport distance, and suggest sedimentation took place on or near the edge of continental crust. Comparison with other upper Palaeozoic to Mesozoic sediments in the Antarctic Peninsula and Patagonia, including detrital zircon composition and the style of deformation, suggests deposition of the Trinity Peninsula Group in an upper plate basin on an active margin, rather than a subduction-related accretionary setting, with slow extension and rifting punctuated by short periods of compression.
Publisher: Geological Society of London
Date: 09-2006
Publisher: Wiley
Date: 12-2017
Publisher: Geological Society of America
Date: 09-01-2017
DOI: 10.1130/G38458.1
Publisher: Copernicus GmbH
Date: 03-04-2020
Abstract: Abstract. Thorium–lead (Th-Pb) crystallization ages of hydrothermal monazites from the western, central and eastern Tauern Window provide new insights into Cenozoic tectonic evolution of the Tauern metamorphic dome. Growth domain crystallization ages range from 21.7 ± 0.4 to 10.0 ± 0.2 Ma. Three major periods of monazite growth are recorded between ∼ 22–20 (peak at 21 Ma), 19–15 (major peak at 17 Ma) and 14–10 Ma (major peak around 12 Ma), respectively, interpreted to be related to prevailing N–S shortening, in association with E–W extension, beginning strike-slip movements and reactivation of strike-slip faulting. Fissure monazite ages largely overlap with zircon and apatite fission track data. Besides tracking the thermal evolution of the Tauern dome, monazite dates reflect episodic tectonic movement along major shear zones that took place during the formation of the dome. Geochronological and structural data from the Pfitschtal area in the western Tauern Window show the existence of two cleft generations separated in time by 4 Ma and related to strike-slip to oblique-slip faulting. Moreover, these two phases overprint earlier phases of fissure formation. Highlights. In situ dating of hydrothermal monazite-(Ce). New constraints on the exhumation of the Tauern metamorphic dome. Distinct tectonic pulses recorded from east to west.
Publisher: Elsevier BV
Date: 10-2003
Publisher: Springer Science and Business Media LLC
Date: 29-03-2001
Publisher: Elsevier BV
Date: 08-2015
Publisher: Elsevier BV
Date: 03-2018
Publisher: Springer Science and Business Media LLC
Date: 07-04-2017
DOI: 10.1038/S41598-017-00832-2
Abstract: Granitoid-hosted mineral deposits are major global sources of a number of economically important metals. The fundamental controls on magma metal fertility are tectonic setting, the nature of source rocks, and magma differentiation. A clearer understanding of these petrogenetic processes has been forged through the accessory mineral zircon, which has considerable potential in metallogenic studies. We present an integrated zircon isotope (U-Pb, Lu-Hf, O) and trace element dataset from the paired Cu-Au (copper) and Sn-W (tin) magmatic belts in Myanmar. Copper arc zircons have juvenile εHf (+7.6 to +11.5) and mantle-like δ 18 O (5.2–5.5‰), whereas tin belt zircons have low εHf (−7 to −13) and heavier δ 18 O (6.2–7.7‰). Variations in zircon Hf and U/Yb reaffirm that tin belt magmas contain greater crustal contributions than copper arc rocks. Links between whole-rock Rb/Sr and zircon Eu/Eu* highlight that the latter can monitor magma fractionation in these systems. Zircon Ce/Ce* and Eu/Eu* are sensitive to redox and fractionation respectively, and here are used to evaluate zircon sensitivity to the metallogenic affinity of their host rock. Critical contents of Sn in granitic magmas, which may be required for the development of economic tin deposits, are marked by zircon Eu/Eu* values of ca. ≤0.08.
Publisher: Elsevier BV
Date: 06-2001
Publisher: Elsevier BV
Date: 2017
Publisher: Mineralogical Society of America
Date: 02-2013
Publisher: Elsevier BV
Date: 2017
Publisher: Springer Science and Business Media LLC
Date: 23-09-2019
DOI: 10.1038/S41598-019-49882-8
Abstract: Nanospheres of lead (Pb) have recently been identified in zircon (ZrSiO 4 ) with the potential to compromise the veracity of U-Pb age determinations. The key assumption that the determined age is robust against the effects of Pb mobility, as long as Pb is not lost from the zircon during subsequent geological events, is now in question. To determine the effect of nanosphere formation on age determination, and whether analysis of nanospheres can yield additional information about the timing of both zircon growth and nanosphere formation, zircons from the Napier Complex in Enderby Land, East Antarctica, were investigated by high-spatial resolution NanoSIMS (Secondary Ion Mass Spectrometry) mapping. Conventional SIMS analyses with µm resolution potentially mixes Pb from multiple nanospheres with the zircon host, yielding variable average values and therefore unreliable ages. NanoSIMS analyses were obtained of 207 Pb/ 206 Pb in nanospheres a few nanometres in diameter that were resolved from 207 Pb/ 206 Pb measurements in the zircon host. We demonstrate that analysis for 207 Pb/ 206 Pb in multiple in idual Pb nanospheres, along with separate analysis of 207 Pb/ 206 Pb in the zircon host, can not only accurately yield the age of zircon crystallization, but also the time of nanosphere formation resulting from Pb mobilization during metamorphism. Model ages for both events can be derived that are correlated due to the limited range of possible solutions that can be satisfied by the measured 207 Pb/ 206 Pb ratios of nanospheres and zircon host. For the Napier Complex zircons, this yields a model age of ca 3110 Ma for zircon formation and a late Archean model age of 2610 Ma for the metamorphism that produced the nanospheres. The Nanosphere Model Age (NMA) method constrains both the crystallization age and age of the metamorphism to ~±135 Ma, a significant improvement on errors derived from counting statistics.
Publisher: Elsevier BV
Date: 08-2009
Publisher: Elsevier BV
Date: 11-2018
Publisher: Elsevier BV
Date: 10-2005
Publisher: Wiley
Date: 23-03-2017
DOI: 10.1111/MAPS.12814
Publisher: Elsevier BV
Date: 11-2017
Publisher: Elsevier BV
Date: 12-2015
Publisher: Geological Society of America
Date: 05-2007
DOI: 10.1130/B26080.1
Publisher: Proceedings of the National Academy of Sciences
Date: 06-04-2015
Abstract: Metallic lead nanospheres have been discovered in ancient ( .4 Ga) zircon grains from an Archean (2.5 Ga) high-grade metamorphic terrain in East Antarctica. Native Pb is present as 5–30 nm nanospheres, commonly in association with an amorphous silica-rich phase, along with titanium and aluminium-bearing phases. Together, these phases form nanoinclusions generated during the recovery of crystallinity in radiation-damaged zircon under high-grade metamorphic conditions. Once formed, the entrapment of nanospheres in annealed zircon effectively arrests Pb loss, explaining why zircon that has experienced such extreme conditions is not completely reset to its metamorphic age. The heterogeneous distribution of Pb can, however, affect isotopic measurement by microbeam techniques, leading to spurious age estimates. Metallic Pb is extremely rare in nature and has never previously been observed in high temperature rocks.
Publisher: Elsevier BV
Date: 04-2006
Publisher: Elsevier BV
Date: 11-2016
Publisher: University of Chicago Press
Date: 03-2009
DOI: 10.1086/595017
Publisher: Elsevier BV
Date: 02-2018
Publisher: American Association for the Advancement of Science (AAAS)
Date: 12-11-2021
Abstract: Measuring physical s les of Solar System bodies in the laboratory provides more information than is possible from remote sensing alone. In December 2020, the Chang’e-5 mission landed on the Moon, collected s les, and returned them to Earth. Che et al . analyze two fragments of volcanic lunar basalt collected by Chang’e-5. Radiometric dating using lead isotopes indicated that the rocks formed from magma that erupted about 2 billion years ago, later than other volcanic lunar s les. The abundance of extinct radioactive elements in the rock is too low for radioactive heating to have produced the magma. Another, thus far unknown, source must be responsible for the late lunar volcanism. —KTS
Publisher: Elsevier BV
Date: 15-04-2006
Publisher: Elsevier BV
Date: 05-2004
Publisher: Geological Society of America
Date: 2005
DOI: 10.1130/G21706.1
Publisher: Elsevier BV
Date: 05-2015
Publisher: Copernicus GmbH
Date: 30-10-2019
DOI: 10.5194/SE-2019-162
Abstract: Abstract. Thorium-Pb crystallization ages of hydrothermal monazites from the western, central and eastern Tauern Window provide new insights into Cenozoic tectonic evolution of the Tauern metamorphic dome. Growth domain crystallization ages range from 22.3 ± 0.6 Ma to 7.7 ± 0.9 Ma. Three major periods of monazite growth are recorded between ~ 22–19 (peak at 21 Ma), 19–15 (major peak at 17 Ma) and 13–8 Ma (major peaks at 12, 10 and 8 Ma), respectively interpreted to be related to prevailing N-S shortening, in association with E-W extension, beginning strike-slip movements, and reactivation of strike-slip faulting. Fissure monazite ages largely overlap with zircon and apatite fission tracks data. Besides tracking the thermal evolution of the Tauern dome, monazite dates reflect episodic tectonic movement along major shear zones that took place during the formation of the dome. Geochronological and structural data from the Pfitschtal area in the western Tauern Window show the existence of two cleft generations separated in time by 4 Ma and related to strike-slip to oblique-slip faulting. Moreover, these two phases overprint earlier phases of fissure formation.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 30-09-2022
Abstract: Impact glasses found in lunar soils provide a possible window into the impact history of the inner solar system. However, their use for precise reconstruction of this history is limited by an incomplete understanding of the physical mechanisms responsible for their origin and distribution and possible relationships to local and regional geology. Here, we report U-Pb isotopic dates and chemical compositions of impact glasses from the Chang’e-5 soil and quantitative models of impact melt formation and ejection that account for the compositions of these glasses. The predominantly local provenance indicated by their compositions, which constrains transport distances to ~150 kilometers, and the age-frequency distribution are consistent with formation mainly in impact craters 1 to 5 kilometers in diameter. Based on geological mapping and impact cratering theory, we tentatively identify specific craters on the basaltic unit s led by Chang’e-5 that may have produced these glasses and compare their ages with the impact record of the asteroid belt.
Publisher: Elsevier BV
Date: 2020
Publisher: Geological Society of America
Date: 03-04-2015
DOI: 10.1130/B31214.1
Publisher: Springer Science and Business Media LLC
Date: 24-08-2014
DOI: 10.1038/NGEO2231
Publisher: Springer Science and Business Media LLC
Date: 23-07-2018
Publisher: Springer Science and Business Media LLC
Date: 06-2018
Publisher: Elsevier BV
Date: 2015
Publisher: Elsevier BV
Date: 08-1999
Publisher: Geological Society of London
Date: 23-08-2010
Publisher: American Chemical Society (ACS)
Date: 09-01-2017
DOI: 10.1021/ACS.ANALCHEM.6B04330
Abstract: The Pb isotope composition of a nuclear fallout debris particle has been directly measured in post-detonation materials produced during the Trinity nuclear test by a secondary ion mass spectrometry (SIMS) scanning ion image technique (SII). This technique permits the visual assessment of the spatial distribution of Pb and can be used to obtain full Pb isotope compositions in user-defined regions in a 70 μm × 70 μm analytical window. In conjunction with backscattered electron (BSE) and energy-dispersive spectroscopy (EDS) mapping of the same particle, the Pb measured in this fallout particle cannot be from a major phase in the precursor arkosic sand. Similarly, the Pb isotope composition of the particle is resolvable from the surrounding glass at the 2σ uncertainty level (where σ represents the standard deviation). The Pb isotope composition measured in the particle here is in excellent agreement with that inferred from measurements of green and red trinitite, suggesting that these types of particles are responsible for the Pb isotope compositions measured in both trinitite glasses.
Publisher: Oxford University Press (OUP)
Date: 14-10-2004
Publisher: American Association for the Advancement of Science (AAAS)
Date: 16-02-2007
Abstract: Granitic plutonism is the principal agent of crustal differentiation, but linking granite emplacement to crust formation requires knowledge of the magmatic evolution, which is notoriously difficult to reconstruct from bulk rock compositions. We unlocked the plutonic archive through hafnium (Hf) and oxygen (O) isotope analysis of zoned zircon crystals from the classic hornblende-bearing (I-type) granites of eastern Australia. This granite type forms by the reworking of sedimentary materials by mantle-like magmas instead of by remelting ancient metamorphosed igneous rocks as widely believed. I-type magmatism thus drives the coupled growth and differentiation of continental crust.
Publisher: Elsevier BV
Date: 03-2006
Publisher: Geological Society of America
Date: 06-10-2010
DOI: 10.1130/B30139.1
Publisher: Elsevier BV
Date: 09-2012
Publisher: Wiley
Date: 16-03-2017
DOI: 10.1111/GBI.12234
Abstract: We revisit the S-isotope systematics of sedimentary pyrite in a shaly limestone from the ca. 2.52 Ga Gamohaan Formation, Upper C bellrand Subgroup, Transvaal, South Africa. The analysed rock is interpreted to have been deposited in a water depth of ca. 50-100 m, in a restricted sub-basin on a drowning platform. A previous study discovered that the pyrites define a nonzero intercept δ
Publisher: Springer Science and Business Media LLC
Date: 09-06-2021
DOI: 10.1038/S43247-021-00181-Z
Abstract: Impact cratering on the Moon and the derived size-frequency distribution functions of lunar impact craters are used to determine the ages of uns led planetary surfaces across the Solar System. Radiometric dating of lunar s les provides an absolute age baseline, however, crater-chronology functions for the Moon remain poorly constrained for ages beyond 3.9 billion years. Here we present U–Pb geochronology of phosphate minerals within shocked lunar norites of a boulder from the Apollo 17 Station 8. These minerals record an older impact event around 4.2 billion years ago, and a younger disturbance at around 0.5 billion years ago. Based on nanoscale observations using atom probe tomography, lunar cratering records, and impact simulations, we ascribe the older event to the formation of the large Serenitatis Basin and the younger possibly to that of the Dawes crater. This suggests the Serenitatis Basin formed unrelated to or in the early stages of a protracted Late Heavy Bombardment.
Publisher: Oxford University Press (OUP)
Date: 05-2018
Publisher: Copernicus GmbH
Date: 23-03-2020
DOI: 10.5194/EGUSPHERE-EGU2020-17704
Abstract: & & Constraining the duration of magmatic activity on the Moon is essential to understand how the lunar mantle evolved chemically through time. Determining age and initial isotopic compositions of mafic lunar meteorites is a critical step in defining the periods of magmatic activity that occurred during the history of the Moon and to constrain the chemical characteristics of mantle components involved in the sources of the magmas.& & & & We have used the in-situ Pb& #8211 Pb SIMS technique to investigate lunar gabbros and basalts, including meteorites from the Northwest Africa (NWA) 773 clan (NWA 2727, NWA 3333, NWA 2977, NWA 773 and NWA 3170), LAP 02224, NWA 4734 and Dhofar 287A. These s les have been selected as they all belong to the dominant chemical group of low-titanium mare basalts and there is no clear agreement on their age. We have obtained ages of 2978 & #177 13 Ma for LAP02224, 2981 & #177 12 Ma for NWA 4734 and 3208 & #177 22 Ma for Dhofar 287. For the NWA 773 clan, four s les (NWA 2727, NWA 773, NWA 2977, NWA 3170) yielded isochron-calculated ages that are identical within uncertainties with an average age of 3086.1 & #177 4.8 Ma. The gabbroic s le NWA 3333 yielded an age of 3038 & #177 20 Ma suggesting that two distinct magmatic events are recorded in the meteorites of the NWA 773 clan.& & & & The entire age dataset from lunar mafic meteorites was screened to identify data that are problematic from an analytical viewpoint and/or show evidence of resetting and terrestrial contamination. This refined dataset combines the ages of mafic lunar meteorites and Apollo s les and suggests pulses in magmatic activity, with two main phases between 3350 and 3100 Ma and between 3900 and 3550 Ma followed by a minor phase at ~3000 Ma.& & & & The evolution of the Pb initial ratios of the low-Ti mare basalts between 3400 Ma and 3100 Ma suggests that these rocks were progressively contaminated by a KREEP-like component. Nevertheless, the ~3000 Ma mafic rocks (NWA4734 and LAP02224) show significant differences in terms of initial & sup& & /sup& Pb/& sup& & /sup& Pb ratios that illustrates that the lunar mantle is probably more heterogeneous than has previously been assumed.& &
Publisher: Elsevier BV
Date: 2019
Publisher: Geological Society of America
Date: 16-11-2013
DOI: 10.1130/G39894.1
Publisher: Elsevier BV
Date: 05-2015
Publisher: American Journal of Science (AJS)
Date: 02-2007
DOI: 10.2475/02.2007.06
Publisher: Elsevier BV
Date: 06-2018
Publisher: Geological Society of London
Date: 03-1998
Publisher: Elsevier BV
Date: 11-2016
Publisher: Proceedings of the National Academy of Sciences
Date: 12-05-2009
Abstract: The age of the Vindhyan sedimentary basin in central India is controversial, because geochronology indicating early Proterozoic ages clashes with reports of Cambrian fossils. We present here an integrated paleontologic–geochronologic investigation to resolve this conundrum. New s ling of Lower Vindhyan phosphoritic stromatolitic dolomites from the northern flank of the Vindhyans confirms the presence of fossils most closely resembling those found elsewhere in Cambrian deposits: annulated tubes, embryo-like globules with polygonal surface pattern, and filamentous and coccoidal microbial fabrics similar to Girvanella and Renalcis . None of the fossils, however, can be ascribed to uniquely Cambrian or Ediacaran taxa. Indeed, the embryo-like globules are not interpreted as fossils at all but as former gas bubbles trapped in mucus-rich cyanobacterial mats. Direct dating of the same fossiliferous phosphorite yielded a Pb–Pb isochron of 1,650 ± 89 (2σ) million years ago, confirming the Paleoproterozoic age of the fossils. New U–Pb geochronology of zircons from tuffaceous mudrocks in the Lower Vindhyan Porcellanite Formation on the southern flank of the Vindhyans give comparable ages. The Vindhyan phosphorites provide a window of 3-dimensionally preserved Paleoproterozoic fossils resembling filamentous and coccoidal cyanobacteria and filamentous eukaryotic algae, as well as problematic forms. Like Neoproterozoic phosphorites a billion years later, the Vindhyan deposits offer important new insights into the nature and ersity of life, and in particular, the early evolution of multicellular eukaryotes.
Publisher: Elsevier BV
Date: 10-2017
Publisher: Elsevier BV
Date: 04-2009
Publisher: Wiley
Date: 11-2009
Publisher: Springer Science and Business Media LLC
Date: 05-2012
DOI: 10.1038/NATURE11140
Abstract: Earth's lithosphere probably experienced an evolution towards the modern plate tectonic regime, owing to secular changes in mantle temperature. Radiogenic isotope variations are interpreted as evidence for the declining rates of continental crustal growth over time, with some estimates suggesting that over 70% of the present continental crustal reservoir was extracted by the end of the Archaean eon. Patterns of crustal growth and reworking in rocks younger than three billion years (Gyr) are thought to reflect the assembly and break-up of supercontinents by Wilson cycle processes and mark an important change in lithosphere dynamics. In southern West Greenland numerous studies have, however, argued for subduction settings and crust growth by arc accretion back to 3.8 Gyr ago, suggesting that modern-day tectonic regimes operated during the formation of the earliest crustal rock record. Here we report in situ uranium-lead, hafnium and oxygen isotope data from zircons of basement rocks in southern West Greenland across the critical time period during which modern-like tectonic regimes could have initiated. Our data show pronounced differences in the hafnium isotope-time patterns across this interval, requiring changes in the characteristics of the magmatic protolith. The observations suggest that 3.9-3.5-Gyr-old rocks differentiated from a >3.9-Gyr-old source reservoir with a chondritic to slightly depleted hafnium isotope composition. In contrast, rocks formed after 3.2 Gyr ago register the first additions of juvenile depleted material (that is, new mantle-derived crust) since 3.9 Gyr ago, and are characterized by striking shifts in hafnium isotope ratios similar to those shown by Phanerozoic subduction-related orogens. These data suggest a transitional period 3.5-3.2 Gyr ago from an ancient (3.9-3.5 Gyr old) crustal evolutionary regime unlike that of modern plate tectonics to a geodynamic setting after 3.2 Gyr ago that involved juvenile crust generation by plate tectonic processes.
Location: United Kingdom of Great Britain and Northern Ireland
Location: United Kingdom of Great Britain and Northern Ireland
Start Date: 04-2017
End Date: 12-2021
Amount: $345,000.00
Funder: Australian Research Council
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