GEOLOGICAL SIGNIFICANCE OF LEAD-ALPHA AND ISOTOPIC AGE DETERMINATIONS OF “ALKALIC” ROCKS OF NEW ENGLAND

1961 ◽  
Vol 72 (5) ◽  
pp. 775 ◽  
Author(s):  
PRIESTLEY TOULMIN
Keyword(s):  
New England ◽  
Isotopic Age ◽  
Geological Significance ◽  
Age Determinations

scholarly journals Routine K/Ar age determinations on rocks from Greenland carried out for GGU in 1970

1971 ◽  
Vol 35 ◽  
pp. 52-60
Author(s):  
D Bridgwater
Keyword(s):  
Analytical Data ◽  
Age Determination ◽  
Geological Significance ◽  
Reconnaissance Survey ◽  
Geological Work ◽  
The University ◽  
Age Determinations

The programme of commercial age determinations started in 1969 (Bridgwater, 1970) was continued to supplement the work carried out by the University of Copenhagen (Larsen, this report). The material dated represents a rather heterogeneous collection of rocks from many parts of Greenland about which information was required for current geological work but which were not included in existing age determination projects. All the results obtained are listed whether or not the "ages", have a clear geological significance, since a major reason for carrying out this form of reconnaissance survey is to test the suitability of K/Ar methods for making more detailed studies. Full analytical data is available on request from GGU. Unless otherwise stated the results given are means of three determinations.

scholarly journals Isotopic age dating in Liverpool Land, East Greenland

1987 ◽  
Vol 134 ◽  
pp. 25-37
Author(s):  
B.T Hansen ◽  
J.D Friderichsen
Keyword(s):  
Age Dating ◽  
Isotopic Age ◽  
Pb Isotope ◽  
East Greenland ◽  
Isotope Age ◽  
Caledonian Orogeny ◽  
Plutonic Rocks ◽  
Age Determinations ◽  
Late Part

In Liverpool Land in the eastern part of the Scoresby Sund region gneisses and migmatites were intruded by a number of intermediate plutonites and by younger granites. A number of K-Ar, Rb-Sr and U-Pb isotope age determinations indicate that: 1) the gneisses have a pre-CaIedonian as well as a CaIedonian history, 2) the migmatites were thoroughly reworked during the late part of the Caledonian orogeny, while 3) the plutonic rocks all seem to have been intruded during the Caledonian orogeny.

scholarly journals Mapping in the Fiskefjord area, southern West Greenland

1982 ◽  
Vol 110 ◽  
pp. 55-57
Author(s):  
A.A Garde ◽  
V.R McGregor
Keyword(s):  
Granulite Facies ◽  
Amphibolite Facies ◽  
Isotopic Age ◽  
Supracrustal Rock ◽  
Granulite Facies Metamorphism ◽  
West Greenland ◽  
Facies Metamorphism ◽  
Geological Work ◽  
Age Determinations

Previous geological work on the 1:100000 map sheet 64 V.l N (fig. 15) includes published maps of smaller areas by Berthelsen (1960, 1962) and Lauerma (1964), mapping by Kryolitselskabet Øresund A/S (Bridgwater et al., 1976) and mapping by GGU geologists for the 1:500000 map sheet Frederikshåb Isblink - Søndre Strømfjord (Allaart et al., 1977, 1978). The Amltsoq and Niik gneisses and Malene supracrustal rock units south and east of Godthåbsfjord have not so far been correlated with rocks in the Fiskefjord area. Godthåbsfjord separates the granulite facies gneisses in Nordlandet from amphibolite facies Nûk gneisses on Sadelø and Bjørneøen; the granulite facies metamorphism occurred at about 2850 m.y. (Black et al., 1973), while no published isotopic age determinations from the Fiskefjord area itself are available.

Re-Os Isotopic Age of the Hongqiling Cu-Ni Sulfide Deposit in Jilin Province, NE China and its Geological Significance

2014 ◽  
Vol 64 (3) ◽  
pp. 247-261 ◽  
Author(s):  
Chunming Han ◽  
Wenjiao Xiao ◽  
Guochun Zhao ◽  
Benxun Su ◽  
Songjian Ao ◽  
...  
Keyword(s):  
Jilin Province ◽  
Sulfide Deposit ◽  
Isotopic Age ◽  
Ne China ◽  
Geological Significance

Isotopic age determinations on clay minerals from lavas and tuffs of the Derbyshire orefield

1972 ◽  
Vol 109 (6) ◽  
pp. 501-512 ◽  
Author(s):  
P. R. Ineson ◽  
J. G. Mitchell
Keyword(s):  
Clay Minerals ◽  
Hydrothermal Alteration ◽  
Igneous Rocks ◽  
The Other ◽  
Mineral Deposits ◽  
Isotopic Age ◽  
Hydrothermal Mineralization ◽  
Pumice Tuff ◽  
Southern Section ◽  
Age Determinations

SummaryEpisodic hydrothermal mineralization has previously been recognized in the northern section of the Pennine orefield. Igneous rocks from the southern section (the Derbyshire orefield) have yielded isotopic ages, some of which are thought to represent ages of hydrothermal metasomatism (deuteric or subsequent). In order to ascertain whether epicyclic hydrothermal events gave rise to the Derbyshire mineral deposits, samples of highly altered doleritic lava and pumice tuff were collected adjacent to areas of mineralization. Clay-mineral concentrates from 34 samples were dated by the potassium–argon method. The conclusions drawn from these analyses support a hypothesis of repeated hydrothermal alteration of the clay minerals, reflecting at least two episodes of mineralization, one about 270 m.y., the other about 235 m.y. The geo-chronological significance of these and other results is considered.

How reliable is the K-Ar glauconite chronometer? A case study of Eocene sediments from the Isle of Wight

Clay Minerals ◽  
2005 ◽  
Vol 40 (2) ◽  
pp. 167-176 ◽  
Author(s):  
N. Clauer ◽  
J. M. Huggett ◽  
S. Hillier
Keyword(s):  
Magnetic Separation ◽  
Isotopic Age ◽  
High Gradient Magnetic Separation ◽  
Isle Of Wight ◽  
High Gradient ◽  
Final Selection ◽  
Age Determinations ◽  
Highly Evolved

AbstractK-Ar ages of Eocene glauconite pellets from the Isle of Wight are related to quantified amounts of older glauconite pellets and to occurrences of detrital mica/illite particles that might have been added to synsedimentary pellets during reworking processes. Addition of older glauconite did not significantly bias the K-Ar dates, as the results most often provide the expected stratigraphic reference ages or even significantly lower ages. Alternatively, K-Ar dates significantly greater than those suggested by the stratigraphy appear to result from non-glauconized detrital mica in the pellets which is not always removable, even by high-gradient magnetic separation.Unexpected ‘old’ K-Ar glauconite ages do not result from misapplication of the method, but from inability to systematically identify and remove the `contaminant' particles from glauconite splits. Analysis of highly evolved glauconite separates is definitely appropriate for reliable isotopic age determinations, but it might not be enough for the final selection, as long-lasting diagenesis might have taken over the synsedimentary process. Much if not all depends on the separation and characterization of the separates, but also on the completion of the glauconitization process which effects cannot always be anticipated.

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