We use 40 Ar‐ 39 Ar incremental heating to fingerprint bulk fluvial sediment entering the northeast Pacific Ocean, with the long‐term intent of tracking sediment source and transport changes from the terrestrial system to the marine environment through time. We show reproducible age spectra from individual rivers accounting for the majority of sediment delivered to the Pacific margin.
Early stages of Gondwana breakup: The 40Ar/39Ar ...
Incremental 40Ar/39Ar ages of biotite and hornblende from the northeastern Reading Prong: Their bearing on late Proterozoic thermal and tectonic history
Download Citation on ResearchGate | 40Ar/39Ar incremental-release age of biotite from a gabbro of the Shabogamo intrusive suite, southwestern Labrador | Biotite from a gabbro sill of the Shabogamo ...
Biotite from a gabbro sill of the Shabogamo intrusive suite in southwestern Labrador records a well defined 40Ar/39Ar plateau age of 1353 ± 17 Ma. This is similar to the 1375 ± 60 Ma dates recorded by Sm–Nd and Rb–Sr whole-rock isotopic systems of the suite. Together, recent radiometric results suggest that members of the suite were emplaced at approximately 1375 Ma and cooled quickly at ...
New age constraints for a short pulse in Ross orogen deformation triggered by East–West Gondwana suturing. Gondwana Research, 2007. Anne Grunow. John Encarnacion. Timothy Paulsen. M. Watkeys. Paul Layer. Anne Grunow. John Encarnacion. Timothy Paulsen. M. Watkeys.
Apparent-loss age spectra, thus, result from differential gas release of hornblende and an included, earlier degassing minor contamination of much younger biotite, which had apparently not been completely eliminated from the amphibole separate, despite careful handpicking.
Analyses were done at Stanford University. For each of the 4 samples described here, an incremental thermal release age spectra is included, along with a table summarizing the data used to calculate ages, and a table of raw data from each temperature increment.
40 Ar/ 39 Ar step‐heating experiments on hornblende, biotite, plagioclase, and potassium feldspar from gabbro, diorite, plagiogranite, and granite yielded complex release spectra. On isotope correlation diagrams, the incremental‐heating data indicate that gabbro, diorite, and plagiogranite cooled below the closure‐temperature for argon in ...
For 40ar– 39ar biotite, mostly ferro-hornblende or hornblende and rb-sr systems. However, muscovite or hornblende, 40ar/39ar dating is a hydrous lower crust. Hornblende and the muscovite dates are also recorded in hornblende. Ar-Ar dating in mafic rocks of hornblende is 300°c, radiometric age of late archaean and record 100.
The tectonic significance of pre-Scandian 40Ar/39Ar phengite cooling ages in the Caledonides of western Norway. Journal of the Geological Society, 1998. Torgeir Andersen. A. Andresen. Henry Berry. D. Lux. Torgeir Andersen. A. Andresen.
40Ar/39Ar dating of biotite from a calc-alkaline gabbro stock NW of Loscos in the Iberian Range yielded a slightly disturbed gas release spectrum. It has an early Permian, 288.5 ± 1.4 Ma total gas age, interpreted as the minimum emplacement age.
Weighted mean plateau age = 172.411.1 Ma, Fraction of 39Ar in plateau=83.42 % Estimated uncertainties are quoted at one standard deviation. Additional evidence of post-crystallization thermal disturbance in gabbro specimen JD379 is given by the Rb-Sr whole-rock, plagioclase, and biotite age of 142120 Ma, initial
Age references. The table below shows references for all age information in PALEOMAGIA database. ... 40Ar/39Ar incremental-release ages of hornblende and biotite from Grenville basement rocks within the Indian Head range complex, southwest Newfoundland: Their bearing on Late Proterozoic - early Paleozoic thermal history ... Palaeomagnetism and ...
Group gabbro. 40Ar/39Ar dates provide significant new constraints on lithologic affinity and tectonic models such as the approximate 60 Ma age of the high-grade ("Ruby") metamorphic complex. 40 ~t-1~~~ incremental therrnal-release spectra are produced by incrementally heating a sample and
This is reflected by the stable Ar release pattern at low‐ and high‐temperature steps in the age spectrum . A flat age spectrum and an isochron age identical to that of other lavas in this area suggest that propylitic metasomatism is pervasive and rapid following the eruption of lavas.
Abstract. The 40 Ar/ 39 Ar dating technique is a recently developed analytical variation of the conventional K-Ar method. It has greatly enhanced the general applicability of K-Argeochronology because it has the ability to distinguish between: (1) samples which have lost a component of radiogenic argon since their initial crystallization, (2) samples which have remained closed systems with ...
Hornblende from undeformed diorite of the Kdynž complex records a well-defined 40Ar/39Ar age plateau which corresponds to an isotope-correlation age of ca. 516 Ma. This is interpreted to date post-magmatic cooling following emplacement. Key words Variscan ⋅ Cadomian · Teplá-Barrandian · 40Ar/39Ar geochronology · Bohemian Massif
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Biotites in these samples show no petrographic evidence of retrograde alteration, however they do record internally discordant 40 Ar/ 39 Ar age spectra. Although the extent of internal discordance is variable, the overall character of the release patterns is similar with younger apparent ages recorded in intermediate-temperature gas fractions.