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Comparison of K-Ar and whole-rock Rb-Sr dating in New Quebec and Labrador
Continue to access RSC content when you are not at your institution. Follow our step-by-step guide. In situ dating of K-rich minerals, e.
In this article I shall introduce the Rb-Sr dating method, and explain how it works; in the process the reader should learn to appreciate the general reasoning.
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Rubidium/Strontium Dating of Meteorites
Ruiz , L. Jones, W. Describes a Rb-Sr technique that permits ore deposits to be dated using common gangue minerals such as calcite and fluorite.
One of the problems encountered in the Rb-Sr dating of sedimentary rocks concerns the time and extent of Sr isotope homogenization. Several workers.
This study employs the single grain pyrite Rb-Sr technique to date mineralization, using the example of the Linglong lode gold deposit, Jiaodong Peninsula, eastern China. Four pyrite samples from veins of different mineralization stages give an average isochron age of Hence, the successful attempt of the single grain Rb-Sr technique of pyrite, which occurs as a common mineral phase in orebodies and is genetically related to the mineralization, has great potential for precise geochronology of hydrothermal mineral deposits.
Single grain pyrite Rb-Sr dating of the Linglong gold deposit, eastern China. N2 – This study employs the single grain pyrite Rb-Sr technique to date mineralization, using the example of the Linglong lode gold deposit, Jiaodong Peninsula, eastern China. AB – This study employs the single grain pyrite Rb-Sr technique to date mineralization, using the example of the Linglong lode gold deposit, Jiaodong Peninsula, eastern China.
Overview Fingerprint. Abstract This study employs the single grain pyrite Rb-Sr technique to date mineralization, using the example of the Linglong lode gold deposit, Jiaodong Peninsula, eastern China. Access to Document Link to publication in Scopus. Gold deposits Chemical Compounds. Ore Geology Reviews , 34 3 , In: Ore Geology Reviews.
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Conventional fault dating techniques commonly use bulk samples of syn-kinematic illite and other K-bearing minerals in fault gouges, which results in mixed ages of repeatedly reactivated faults as well as grain-size dependent age variations. Here we present a new approach to resolve fault reactivation histories by applying high-spatial resolution Rb-Sr dating to fine-grained mineral slickenfibres in faults occurring in Paleoproterozoic crystalline rocks.
The timing of these growth phases and the associated structural orientation information of the kinematic indicators on the fracture surfaces are linked to far-field tectonic events, including the Caledonian orogeny. Our approach links faulting to individual regional deformation events by minimizing age mixing through micro-scale analysis of individual grains and narrow crystal zones in common fault mineral assemblages.
Dating of faults is of importance for the understanding of faulting histories, local and regional tectonic evolution, as well as mechanisms of faulting and stress release. In cratons, reconstruction of plate tectonics and stress field variations caused by far-field effects of distant orogenic events is aided by geochronological constraints of fault movement.
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K-Ar and Rb-Sr isotopic studies were carried out on authigenic illitic clay minerals in Late Permian coal measures from the Bowen Basin Australia , in order to determine the timing of maximum paleotemperatures, which were responsible for coal maturation and coal seam gas generation. The results indicate two major thermal events affected the Bowen Basin region, at and Ma. The narrow range of age data from different size fractions, lithologies and stratigraphic depths indicates episodic, short-lived thermal events, rather than gradual temperature increase due to progressive burial as previously believed.
PLOEGSMA, MAARTEN: A pilot Rb-Sr dating of the Suomusjärvi ultramylonite: evidence for major post-Svecofennian deformation in SW Finland. Bull. Geol. Soc.
Joaquin Ruiz, Lois M. Jones, William C. Kelly; Rubidium-strontium dating of ore deposits hosted by Rb-rich rocks, using calcite and other common Sr-bearing minerals. Geology ; 12 5 : — We have tested a Rb-Sr technique that permits ore deposits to be dated using common gangue minerals such as calcite and fluorite. The technique was tested using fluorite and calcite from three deposits ranging in age from Tertiary to Precambrian.
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The Rb-Sr beta-decay dating system is one of the most attractive tools in geochronology, as Rb is sufficiently abundant in common K-bearing minerals like biotite, muscovite and K-feldspar. This allows dating of a wide variety of rocks e. However, this advantage was to date negatively counteracted by the lack of a suitable in-situ technique, as beta decay systems by nature have isobaric interferences of the daughter isotope by their respective parent isotope.
A reaction cell sandwiched between two quadrupoles within an inductively coupled plasma mass spectrometer ICP-MS allows exactly this, the online chemical separation of two different elements. Coupled to a laser ablation LA system, in-situ Rb-Sr dating is therefore possible if a suitable reaction gas within the reaction cell can be found that separates Sr from Rb. We present here a simple procedure in which Rb-Sr ages can be obtained from a suite of individual phases in regular thin sections.
The aim of this work was to obtain additional data through Rb-Sr whole rock dating on some units of the metamorphosed basement complex.
Different lithologies impure marble, eclogite and granitic orthogneiss sampled from a restricted area of the coesite-bearing Brossasco—Isasca Unit Dora Maira Massif have been investigated to examine the behaviour of 40 Ar— 39 Ar and Rb—Sr systems in phengites developed under ultrahigh-pressure UHP metamorphism. Mineralogical and petrological data indicate that zoned phengites record distinct segments of the P — T path: prograde, peak to early retrograde in the marble, peak to early retrograde in the eclogite, and late retrograde in the orthogneiss.
Besides major element zoning, ion microprobe analysis of phengite in the marble also reveals a pronounced zoning of trace elements including Rb and Sr. These data confirm previous reports on excess Ar and, more significantly, highlight that phengite acted as a closed system in the different lithologies and that chemical exchange, not volume diffusion, was the main factor controlling the rate of Ar transport. Although this time interval matches Ar ages from the same sample, Rb—Sr data from phengite are not entirely consistent with the whole dataset.
The oldest age obtained from a millimetre-sized grain fraction enriched in prograde—peak phengites may represent a minimum age estimate for the prograde phengite relics. Results highlight the potential of the in situ 40 Ar— 39 Ar laser technique in resolving discrete P — T stages experienced by eclogite-facies rocks provided that excess Ar is demonstrably a negligible factor , and confirm the potential of Rb—Sr internal mineral isochrons in providing precise crystallization ages for eclogite-facies mineral assemblages.
Dating eclogite-facies rocks and their subsequent retrogression at upper crustal levels represents an invaluable, essential tool for constraining the rate of exhumation of these rocks from mantle depths, thus allowing development of theoretical models. To temporally quantify geological processes, isotopic ages must be linked to a specific stage of the P — T —deformation evolution of a rock.
In the most popular approach, this link is established using the closure temperature concept T c ; Dodson, When interpreting isotopic ages in terms of temperature only, this concept has been used to derive the temperature—time path by analysing minerals with different T c. However, high-pressure HP and ultrahigh-pressure UHP metamorphic rocks are peculiar systems, which experienced extreme physical conditions characterized by limited aqueous fluids with restricted mobility, and consequently by limited mass transfer and exceedingly sluggish reaction kinetics.
In these circumstances, one cannot assume that radiogenic daughters diffusing out of a mineral are efficiently removed at the grain boundary and that the concentration of that isotope at the grain boundary is zero.