Combined U-Th/He and (super 40) Ar/(super 39) Ar Geochronology of post-shield lavas from the Mauna Kea and Kohala volcanoes, Hawaii

Author:

Aciego, Sarah Maria, DePaolo, Donald J., Jourdan, F., Kennedy, B.M., Renne, P.R., Sims, K.W.W.

Title:

Combined U-Th/He and (super 40) Ar/(super 39) Ar Geochronology of post-shield lavas from the Mauna Kea and Kohala volcanoes, Hawaii

Periodical:

Geochimica et Cosmochimica Acta

Year:

2010

Volume:

74

Pages:

1620-1635

Subject:

Geochronology Geological time Geology Mauna Kea Late Quaternary Radioactive dating Uranium-thorium dating

Summary:

Late Quaternary lavas from the Mauna Kea and Kohala volcanoes on the Big Island of Hawaii have been dated using the (super 40) Ar/(super 39) Ar and U–Th/He methods to compare the U–Th/He age method with (super 40) Ar/(super 39) Ar ages. Single analyses U–Th/He ages for Hamakua lavas from Mauna Kea are 87 plus or minus 40 to 119 plus or minus 23 ka (2sigma uncertainties), which are in general equal to or younger than (super 40) Ar/(super 39) Ar ages. All of the U–Th/He ages, and all but one spurious (super 40) Ar/(super 39) ages conform to the previously proposed stratigraphy and published (super 14) C and K–Ar ages. The U–Th/He and (super 40) Ar/(super 39) Ar results agree best where there is a relatively large amount of radiogenic (super 40) Ar (>10%), and where the (super 40) Ar/(super 36) intercept calculated from the Ar isochron diagram is close to the atmospheric value. U–Th/He and (super 40) Ar/(super 39) Ar results diverge the most on a low-K transitional tholeiitic basalt with abundant olivine. The U–Th/He and (super 40) Ar/(super 39) methods are complimentary for basalts with ages of order 100–500 ka.

URL:

http://cletus.uhh.hawaii.edu:2074/10.1016/j.gca.2009.11.020

Date:

March 2010

Collection:

Periodicals