Cosmogenic dating basalt dating someone 10 years younger than you
Phillips et al., 1997a and b; Phillips et al, in review, Dunbar and Phillips, 1996; Zreda et al., 1991, 1993; Zreda, 1994; Anthony and Poths, 1992, Laughlin et al., 1994).
These techniques rely on measurement of cosmogenic nuclides that begin to build up as soon as a rock is exposed to cosmic rays.
Received 22 January 2019, Accepted 19 August 2019, Available online 26 August 2019.
We thank George Rossman, Chi Ma, and Michael Jercinovic for assistance with mineral characterization and Lindsey Hedges, Ryan Mc Keon, Elliot Simon, and Derek Berman for laboratory assistance.
At an altitude of 1445 m and an effective geomagnetic latitude of 40.9 ° the calcium spallation rate is 152 ± 11 atoms (g Ca) at sea level and high latitude.Cosmogenic nuclide surface exposure dating and erosion rate measurements in basaltic landscapes rely primarily on measurement of ^3He in olivine or pyroxene.However, geochemical investigations using ^3He have been impossible in the substantial fraction of basalts that lack separable olivine or pyroxene crystals, or where such crystals were present, but have been chemically weathered.Fine-textured basalts often contain small grains of ilmenite, a weathering-resistant mineral that is a target for cosmogenic 3He production with good He retention and straightforward mineral separation, but with a poorly constrained production rate. Lamb, Cosmogenic 3He production rate in ilmenite and the redistribution of spallation 3He in fine-grained minerals, Geochimica et Cosmochimica Acta, 2019, ISSN 0016-7037, https://doi.org/10.1016/20.Here we empirically calibrate the cosmogenic ^3He production rate in ilmenite by measuring ^3He concentrations in basalts with fine-grained (∼20 μm cross-section) ilmenite and co-existing pyroxene or olivine from the Columbia River and Snake River Plain basalt provinces in the western United States.
The use of terrestrial cosmogenic nuclides to investigate surface exposure histories continues to gain popularity due to the applicability of the technique to many different minerals and rock types.