Age determination of Precambrian rocks from Greenland: past and present

1997 ◽  
pp. 55-59 ◽  
Author(s):  
Feiko Kalsbeek
Keyword(s):  
Age Determination ◽  
Isotopic Analysis ◽  
Radiometric Dating ◽  
Pb Isotope ◽  
Precambrian Rocks ◽  
Igneous Intrusions ◽  
Dating Methods ◽  
History Of ◽  
Single Zircon

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Kalsbeek, F. (1997). Age determination of Precambrian rocks from Greenland: past and present. Geology of Greenland Survey Bulletin, 176, 55-59. https://doi.org/10.34194/ggub.v176.5062 _______________ Age determination is an essential part of many geological investigations. The ages of Phanerozoic sedimentary rocks are typically determined by palaeontological studies (often with high precision), but for Precambrian rocks as well as for younger igneous intrusions, precise ages can only be obtained by isotopic analysis of minerals or rocks. Isotopic (radiometric) age determination of Greenland rocks began in the early 1960s and has continued since with gradually improving methods. In this contribution, the development of geochronological knowledge of the Precambrian of Greenland is described in historical perspective, and an outline of new results is given. The history of geochronology can be roughly divided into three periods: 1) a period of single-sample K-Ar and Rb-Sr mineral or whole-rock age determinations; 2) a time when most ages were determined with the help of Rb-Sr and Pb-Pb whole-rock isochrons and multi-grain zircon U-Pb isotope data; 3) the present, where ‘single’ zircon U-Pb data are the preferred method to obtain rock ages. These stages in the development of radiometric dating methods partly overlap in time, and each has yielded very significant contributions to the knowledge of Precambrian evolution in Greenland.

New age determination of the Cenozoic Lunpola basin, central Tibet

2011 ◽  
Vol 149 (1) ◽  
pp. 141-145 ◽  
Author(s):  
HUAIYU HE ◽  
JIMIN SUN ◽  
QIULI LI ◽  
RIXIANG ZHU
Keyword(s):  
Isotope Composition ◽  
Age Determination ◽  
The Tibetan Plateau ◽  
Late Oligocene ◽  
Geological Past ◽  
History Of ◽  
Uplift History ◽  
Central Tibet ◽  
Important Basis

AbstractKnowing when the Tibetan Plateau reached its present elevation is important for understanding the uplift history of Tibet. Recently, Rowley & Currie (2006) suggested that central Tibet exceeded 4000 m from 35 Ma to the Pliocene using the oxygen-isotope composition of calcareous minerals in Lunpola basin sediments. However, they adopted a poor age assignment for the Dingqing Formation in the Lunpola basin based on previous microfossil studies. In this study, we present SIMS U–Pb zircon dates from a bentonite layer intercalated within the middle to lower Dingqing Formation. Twenty-six measurements yield a highly reliable U–Pb age of 23.5 ± 0.2 Ma (2σ, MSWD = 1.1), suggesting that the deposition age of the Dingqing Formation is late Oligocene to early Miocene, much older than the Miocene–Pliocene age used by Rowley & Currie (2006). This age robustly constrains the age of Cenozoic sedimentary strata in central Tibet, and hence provides an important basis for estimating the palaeoelevation in the high Tibet during the geological past.

A reassessment of the timing of early Archaean crustal evolution in West Greenland

1998 ◽  
pp. 88-93 ◽  
Author(s):  
Stephen Moorbath ◽  
Balz Samuel Kamber
Keyword(s):  
Grain Structure ◽  
Crustal Evolution ◽  
Pb Isotope ◽  
West Greenland ◽  
Ion Probe ◽  
Combined Use ◽  
Wide Range ◽  
History Of ◽  
Single Zircon ◽  
Precambrian Terrain

NOTE: This article was published in a former series of GEUS Bulletin. Please use the original series name when citing this article, for example: Moorbath, S., & Kamber, B. S. (1998). A reassessment of the timing of early Archaean crustal evolution in West Greenland. Geology of Greenland Survey Bulletin, 180, 88-93. https://doi.org/10.34194/ggub.v180.5091 _______________ In last year’s Review of Greenland activities, Kalsbeek (1997) divided the recent history of geochronology into three successive periods: 1. single-sample K-Ar and Rb-Sr mineral or whole-rock age determinations; 2. Rb-Sr and Pb/Pb whole-rock isochrons and multigrain zircon U-Pb isotope data; 3. the present, where ‘single’ zircon U-Pb data are predominantly used. To these three, we would propose adding a fourth, namely a combination of all three, in order to achieve the maximum age information within complex terrains. For an early Precambrian terrain like that of West Greenland, we consider that the combined use of at least the last two approaches is essential (to which should be added the Sm-Nd method). In recent years, study of the geochronological evolution of the Godthåbsfjord and Isua regions has been dominated by rapid and precise ion-probe U-Pb dating of complex-structured zircons, and it has become fashionable to regard the wide range of zircon dates, and particularly the oldest, as giving the age of rock formation. Dates obtained from whole-rock Rb-Sr, Sm-Nd and Pb/Pb regressions have been regarded as too imprecise for adequate age resolution, whilst constraints on crustal evolution imposed by initial Sr, Nd and Pb isotope ratios have been summarily dismissed or totally ignored. We consider that this sole dependence on ion-probe dating of zircon can lead (as, indeed, in the early Archaean of West Greenland) to a potential misinterpretation of the timing of crustal evolution, especially in those cases where little or no information regarding the relationship between measured date and internal grain structure is available. Figure 1 shows the localities mentioned in the text.

Age determination of plutonium material by alpha spectrometry and thermal ionization mass spectrometry

2008 ◽  
Vol 96 (6) ◽  
Author(s):  
Hai-Tao Zhang ◽  
F. R. Zhu ◽  
J. Xu ◽  
Y. H. Dai ◽  
D. M. Li ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Alpha Spectrometry ◽  
Thermal Ionization Mass Spectrometry ◽  
Age Determination ◽  
Thermal Ionization ◽  
Ionization Mass Spectrometry ◽  
Ionization Mass ◽  
History Of ◽  
Thermal Ionization Mass

SummaryAge is a key parameter to deduce the history of a plutonium material. An experimental method using both alpha spectrometry and thermal ionization mass spectrometry has been developed for the age determination of plutonium material. This method is based on the parent/daughter pair

scholarly journals Eruption age of Kannabe volcano using multi-dating: Implications for age determination of young basaltic lava flow

2019 ◽  
Vol 46 (1) ◽  
pp. 49-56
Author(s):  
Yorinao Shitaoka ◽  
Takeshi Saito ◽  
Junji Yamamoto ◽  
Masaya Miyoshi ◽  
Hidemi Ishibashi ◽  
...  
Keyword(s):  
Lava Flow ◽  
Soil Layer ◽  
Age Determination ◽  
Osl Dating ◽  
Basaltic Lava ◽  
Dating Methods ◽  
Paleomagnetic Dating ◽  
Eruption Age ◽  
Basaltic Lava Flow

Abstract We estimated the eruption age of Kannabe volcano, located in southwestern Japan. Although the eruption age had been estimated using tephrochronology and K-Ar dating, the precision of its age determination left some room for improvement. The latest eruption age of Kannabe volcano is well constrained by wide spread tephras to ca. 7.2–30 ka. We applied paleomagnetic dating to a basaltic lava and optically stimulated luminescence (OSL) dating to a soil layer, which are associated with the Kannabe volcano. The soil layer above the Kannabe scoria was newly dated to be 21 ± 6 ka, as inferred from OSL dating. We also made paleomagnetic investigation to estimate the eruption age of the Kannabe basaltic lava. Paleomagnetic data of 23 rock samples from six locations in the Kannabe basaltic lava showed good mutual agreement. The average of remanent magnetizations yields declination of 0.3° and inclination of 65.9° with 95% confidence limit of 2.7°. This paleomagnetic direction with a relatively steep inclination is thought to be correlated with the paleomagnetic secular variation data of sediments in Lake Biwa at ca. 21.5 ka. Based on that information from multi-dating, we inferred that the Kannabe volcano erupted at ca. 22 ka. This result presents profound scientific implications for the precise age determination of young basaltic lava flow, for which few dating methods exist.

Unveiling the history of seized plutonium through nuclear forensic investigations

2009 ◽  
Vol 97 (4-5) ◽  
Author(s):  
Klaus Mayer ◽  
Maria Wallenius ◽  
M. Hedberg ◽  
Klaus Lützenkirchen
Keyword(s):  
Age Determination ◽  
Nuclear Material ◽  
Radioactive Material ◽  
Radioactive Materials ◽  
Nuclear Terrorism ◽  
History Of ◽  
Illicit Trafficking ◽  
Nuclear Forensic ◽  
Intended Use

AbstractIllicit incidents involving nuclear or other radioactive materials and the threat of nuclear terrorism are reasons for serious concern. Since 1993 more than 1300 incidents have been reported to the IAEA Illicit Trafficking Database. Only a small number of cases involve plutonium or plutonium containing materials. However, these cases are attributed particular attention in view of the proliferation aspects and of the radiotoxicity associated with plutonium. Efforts focus on prevention, detection and response to cases of illicit trafficking of nuclear material. If the place of theft or diversion of the material can be identified, then measures of safeguards and physical protection can be implemented to prevent future thefts.Nuclear Forensic Science aims at providing clues on the origin and intended use of nuclear or other radioactive material involved in illicit incidents. The paper provides a brief description of the nuclear forensic methodology and describes in detail the challenges associated with age determination of plutonium materials.

Chronostratigraphy of uplifted Quaternary hemipelagic deposits from the Dodecanese island of Rhodes (Greece)

2016 ◽  
Vol 86 (1) ◽  
pp. 79-94 ◽  
Author(s):  
Frédéric Quillévéré ◽  
Jean-Jacques Cornée ◽  
Pierre Moissette ◽  
Gatsby Emperatriz Lopez-Otalvaro ◽  
Christiaan van Baak ◽  
...  
Keyword(s):  
Eastern Mediterranean ◽  
Age Determination ◽  
Eastern Mediterranean Region ◽  
Western Mediterranean ◽  
Radiometric Dating ◽  
Type Locality ◽  
Unique Element ◽  
Calcareous Nannofossils ◽  
Mediterranean Regions

AbstractAn integrated magneto-biostratigraphic study, based on calcareous nannofossils and foraminifers, together with the radiometric dating of a volcaniclastic layer found in several outcrops, was carried out on the hemipelagic deposits of the Lindos Bay Formation (LBF) at six localities on the island of Rhodes (Greece). Our highly refined chronostratigraphic framework indicates that the lower and upper lithos-tratigraphic boundaries of the LBF are diachronous. Associated with the40Ar/39Ar age determination of 1.85 ± 0.08 Ma for the volcaniclastic layer, our data show that among the investigated outcrops, the Lindos Bay type locality section provides the longest record (1.1 Ma) of the LBF. Hemipelagic deposition occurred continuously from the late Gelasian (~1.9 Ma) to the late Calabrian (~0.8 Ma), i.e., from Chrons C2n (Olduvai) to C1r.1r (Matuyama) and from nannofossil Zones CNPL7 to CNPL10. This long record, together with the hemipelagic nature of the deposits, make the Lindos Bay type locality section a unique element in the eastern Mediterranean region, allowing future comparisons with other early Quaternary deep-sea sections available in the central and western Mediterranean regions.

SIMS Pb–Pb and U–Pb age determination of eucrite zircons at<5μm scale and the first 50Ma of the thermal history of Vesta

2013 ◽  
Vol 110 ◽  
pp. 152-175 ◽  
Author(s):  
Qin Zhou ◽  
Qing-Zhu Yin ◽  
Edward D. Young ◽  
Xian-Hua Li ◽  
Fu-Yuan Wu ◽  
...  
Keyword(s):  
Thermal History ◽  
Age Determination ◽  
History Of

Age Determination of Carboniferous Basic Rocks of Shropshire and Colonsay

1941 ◽  
Vol 78 (1) ◽  
pp. 45-61 ◽  
Author(s):  
W. D. Urry ◽  
Arthur Holmes
Keyword(s):  
Time Scale ◽  
Age Determination ◽  
Igneous Rocks ◽  
Fine Grained ◽  
History Of ◽  
Basic Rocks

The helium method of determining the ages of fine-grained basic igneous rocks has now been so far developed as to be applicable to various geological and petrological problems, particularly where geological periods are involved, as in the problem here discussed. For details of the history of this development up to the beginning of 1937 reference may be made to Holmes, 1931; Urry, 1933; Lane and Urry, 1935; Urry, 1936 (b); Holmes and Paneth, 1936; and Holmes, 1937. During 1937 it was found that many of the helium-ratios on which the ‘helium’ time-scale had been based were too high, because of a previously unsuspected error in radium determination due to reliance having being placed on a radium standard which was seriously at fault. To clear up this embarrassing situation an immediate effort was made by several investigators in collaboration, and the first fruits of their work have recently become available (Evans, Goodman, Keevil, Lane, and Urry, 1939).

scholarly journals Routine K/Ar age determination on post-Silurian dolerite dykes, North Greenland fold belt

1983 ◽  
Vol 115 ◽  
pp. 9-14
Author(s):  
P.R Dawes ◽  
D.C Rex ◽  
N.J Soper
Keyword(s):  
Age Determination ◽  
Field Studies ◽  
Fold Belt ◽  
The North ◽  
Isotopic Analyses ◽  
History Of ◽  
Magmatic History ◽  
The University ◽  
North Greenland

This note documents results of routine K/Ar isotopic age determination of dolerite dykes from the North Greenland fold belt. All the material was collected in 1969 by two of us (P.R.D. and N.J.S.) during the Joint Services Expedition to Peary Land; the isotopic analyses have been undertaken by D.C.R. in the geologicallaboratories of the University of Leeds. In view of the renewed interest in the tectonic and magmatic history of the Peary Land region stemming from the systematic field studies carried out by GGU in 1978-1980 (see GGU Rapport 88, 99 and 106), the results of this early dating programme are listed here as a contribution to this discussion. Recently, some reference has been made in the literature to these hitherto unpublished results (Dawes & Soper, 1979; Higgins et al., 1981; Håkansson & Pedersen, 1982).

scholarly journals The ages of Galactic globular clusters in the context of self-enrichment

2008 ◽  
Vol 4 (S258) ◽  
pp. 265-274 ◽  
Author(s):  
T. Decressin ◽  
H. Baumgardt ◽  
P. Kroupa ◽  
G. Meynet ◽  
C. Charbonnel
Keyword(s):  
Globular Clusters ◽  
First Generation ◽  
Second Generation ◽  
Age Determination ◽  
Dynamical Evolution ◽  
Low Velocity ◽  
Tidal Forces ◽  
History Of ◽  
First And Second Generation

AbstractA significant fraction of stars in globular clusters (about 70%-85%) exhibit peculiar chemical patterns, with strong abundance variations in light elements along with constant abundances in heavy elements. These abundance anomalies can be created in the H-burning core of a first generation of fast-rotating massive stars, and the corresponding elements are conveyed to the stellar surface thanks to rotational induced mixing. If the rotation of the stars is fast enough, this material is ejected at low velocity through a mechanical wind at the equator. It then pollutes the interstellar medium (ISM) from which a second generation of chemically anomalous stars can be formed. The proportion of anomalous stars to normal stars observed today depends on at least two quantities: (1) the number of polluter stars; (2) the dynamical history of the cluster, which may lose different proportions of first- and second-generation stars during its lifetime. Here we estimate these proportions, based on dynamical models for globular clusters. When internal dynamical evolution and dissolution due to tidal forces are accounted for, starting from an initial fraction of anomalous stars of 10% produces a present-day fraction of about 25%, still too small with respect to the observed 70-85%. In the case of gas expulsion by supernovae, a much higher fraction is expected to be produced. In this paper we also address the question of the evolution of the second-generation stars that are He-rich, and deduce consequences for the age determination of globular clusters.

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