Spatially heterogeneous argon-isotope systematics and apparent 40Ar/39Ar ages in perlitised obsidian

Osmium isotope systematics of ureilites

The Os/Os for 22 ureilite whole rock samples, including monomict, augite-bearing, and polymict lithologies, were examined in order to constrain the provenance and subsequent magmatic processing of the ureilite parent body (or bodies). The Re/Os ratios of most ureilites show evidence for a recent disturbance, probably related to Re mobility during weathering, and no meaningful chronological info...

Al-Mg ISOTOPE SYSTEMATICS IN THE EFREMOVKA

Introduction: In recent years, the calcium-aluminum-rich inclusion (CAI) E60 from the Efremovka reduced CV3 chondrite has been used as an age anchor for the Al-Mg extinct chronome-ter (t 1/2 ~0.73 Ma) since an internal Al-Mg isochron corresponding to a 26 Al/ 27 Al ratio of (4.63±0.44)×10-5 has been determined for it [1] and a highly precise 207 Pb-206 Pb age of 4567.11±0.16 Ma has also been re...

Chromium isotope systematics in the Connecticut River

Article history: Received 18 August 2016 Received in revised form 27 February 2017 Accepted 4 March 2017 Available online 7 March 2017 Limited constraints on Cr isotope fractionation duringweathering and river transport is currently a gap in our understanding of the chromium (Cr) isotope system, which is an emerging proxy in environmental and paleoenvironmental studies. Here, we investigate Cr ...

Potassium-argon ages from the galapagos islands.

Potassium-argon ages of eight volcanic rocks from some of the geologically oldest flows exposed in the Galápagos Archipelago indicate that the Galápagos Islands have a probable maximum age of 3 million years. Rocks from six islands were dated; the oldest are from Española (3.2 +/- 0.2), Sante Fe (2.7 +/- 0.1), and Plazas (4.2 +/- 1.8 million years). The new data suggest that the Galápagos Islan...

Zr ISOTOPE SYSTEMATICS OF ALLENDE CAIs