Rb-Sr Dating

Shih, C.-Y., Nyquist, L. E. and Wiesmann, H. (1994) K-Ca and Rb-Sr dating of two lunar granites relative chronometer resetting. Geochimica et Cosmochimica Acta, 58, 3101-3116. 

Simultaneous determination of mother and daughter nuclide by MS is applied in the Rb/ Sr method. The stable Sr isotope Sr serves as reference nuclide. Rb/ Sr dating has been used for many kinds of minerals, magmatic rocks and sedimentary rocks of various origins. 

Cliff R. A. (1994) Rb-Sr dating of white mica- a new potential in metamorphic geochronology. US Geol. Surv. Circular 1107, 62. 

Papanastassiou D. A. and Wasserburg G. J. (1981) Microchrons the Rb- Sr dating of microscopic samples. Proc. 12th Lunar Planet Sci. Conf. B, 1027-1038. 

Petterson M. G. and Windley B. F. (1985) Rb-Sr dating of the Kohistan arc-batholith in the Trans-Himalaya of North Pakistan, and tectonic implications. Earth Planet. Sci. Lett. 74(1), 45-57. 

A mixture of biotite and hornblende from a post-kinematic porphyry dike dated by Deutsch and Webb (1964) yielded a Rb-Sr date of 467 15 Ma (recalculated to 1.42 X10 " year ). This Middle Ordovician date may approach the crystallization age of this rock because the porphyry dikes in the basement of southern Victoria Land are thin (less than 1 m) and therefore cooled more rapidly than the much more voluminous Granite Harbor Intrusives (e.g., Olympus, Dais, Theseus, Vida, and Irizar). 

Isotopic age determinations of the basement rocks of the Terra-Nova-Bay area are listed in Appendix 4.8.1 based primarily on the work of Kreuzer et al. (1981, 1987), Vetter et al. (1984), Borsi et al. (1988), Armienti et al. (1990), and Adams (2006). The whole-rock Rb-Sr dates reported by Armienti et al. (1990) prove that the age of the Granite Harbor Intrusives of the Deep Freeze Range is Middle Cambrian based on the time scale of the lUGS (2002). All of the whole-rock samples they analyzed define a straight line in Fig. 4.8 that yields a date of507 7 Ma and an initial Sr/ Sr ratio of 0.71034 0.00022. 

The display of dates in Fig. 4.9 also demonstrates that the whole-rock K-Ar dates of the Priestley Schist are lower than those of the Priestley Slate and that they overlap the K-Ar and Rb-Sr dates of biotite of the Granite Harbor Intrusives of the Terra-Nova-Bay area. This observation confirms the hypothesis that the rocks of the Priestley Schist were outgassed during the magmatic activity that accompanied the Ross Orogeny. The Granite Harbor Intrusives and the Priestley Schist subsequently cooled at about the same rate until the Middle Ordovician at about 450 Ma. 

Rb-Sr dates and initial Sr/ Sr ratios of the Granite Harbor Intrusives of southern Victoria Land (Table 3.3, Section 3.4.2 and Appendix 3.6.3). 

Whole-rock Rb-Sr isochron dates indicate that the Rennick Schist of the Daniels Range crystallized at about 532 20 Ma (Early Cambrian lUGS 2002) and that the sandy (psammitic) and clay-rich (pelitic) facies had elevated initial Sr/ Sr ratios of 0.7187 0.0009 and 0.7243 0.0009, respectively (Adams 1986). A Rb-Sr date of a single whole-rock sample reported by Faure and Gair (1970) was recalculated to 548 33 Ma based on initial ratios obtained by Adams (1986) and using the decay constant of Rb recommended by... 

Fig. 4.18 Whole-rock Rb-Sr dates of Wilson Gneisses in the Lantennan and Seilamander ranges are 550 20 and 555 36 Ma, respectively. These dates indicate the time of regional metamorphism during which the strontium in these rocks was isoto-picaUy homogenized. The K-Ar dates of biotite, muscovite, and hornblende are cooUng ages (Data from Kreuzer et al. 1981, 1987 Adams 1982 Adams and Hohndorf 1991). See also Appendix 4.8.3.12.

Fig. 4. 21 K-Ar and Rb-Sr dates of hitotite, muscovite, and hornblende of the Admiralty Intrusives in the Robertson Bay Terrane. These dates sharply define the time of crystrillization between 355 and 365 Ma during the Famennian Stage of the Late Devonian Epoch (lUGS 2002). The good agreement of the K-Ar biotite and hornblende indicates that the rocks cooled rapidly presumably because they were intruded at shallow depth (Data from Kreuzer et al. 1987)...

A small number of Rb-Sr dates of micas of Admiralty plutons at Cooper Spur (70°38 S, IbS OS E) and... 

The whole-rock Rb-Sr date of 1789 141 Ma (Paleoproterozoic) is the time when these rocks were recrystallized during regional metamorphism to amphibolite grade and the strontium they contained was isotopically homogenized so that all three specimens had the same initial Sr/ Sr ratio of 0.7059 0.0041. This value indicates that their protoliths contained strontium derived from the lithospheric mantle in the form of volcanic rocks or their weathering products. 

The minerals of rock sample 522 date the time when the strontium they contained was re-equilibrated to an Sr/ Sr ratio of 0.7511 0.0007. The Rb-Sr date of this event (i.e., 446 14 Ma) agrees with the K-Ar dates of biotite from the Hope Granite in Fig. 5.4. 

Wade and Cathey (1986) also reported isotopic age determinations of feldspar and biotite of the Hope Granite by the K-Ar and Rb-Sr methods. However, feldspars do not retain radiogenic " Ar and the initial Sr/ Sr ratios used to calculate the Rb-Sr dates were not provided. Therefore, the reliability of these dates is uncertain. However, two Rb-Sr dates of biotite from Longhorn Spurs (84°40 S, 174°4LW) and Den Hartog Peak (84°20 S, 178°52 E) indicate that the granitic rocks at these locations cooled sufficiently to retain radiogenic Sr at 470 25 Ma during the Ordovician Period. 

The Rb-Sr date is anomalous and was later corrected by Felder and Faure (1979) who obtained a Rb-Sr date of 470 17 Ma for biotite from a specimen of the Lonely Ridge Granodiorite collected by McLelland (McLelland 208). Consequently, McLelland s date (846 35 Ma) should not be cited in the literature. 

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