Publication Date:
2022-05-26
Description:
© The Author(s), 2016. This is the author's version of the work and is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Geochimica et Cosmochimica Acta 195 (2016): 201-225, doi:10.1016/j.gca.2016.08.017.
Description:
To understand the dynamics of solid mantle upwelling and melting in the Hawaiian
plume, we present new major and trace element data, Nd, Sr, Hf, and Pb isotopic
compositions, and 238U-230Th-226Ra and 235U-231Pa-227Ac activities for 13 Haleakala
Crater nepheline normative basanites with ages ranging from ~900 to 4100 yr B.P..
These basanites of the Hana Volcanics exhibit an enrichment in incompatible trace
elements and a more depleted isotopic signature than similarly aged Hawaiian
shield lavas from Kilauea and Mauna Loa. Here we posit that as the Pacific
lithosphere beneath the active shield volcanoes moves away from the center of the
Hawaiian plume, increased incorporation of an intrinsic depleted component with
relatively low 206Pb/204Pb produces the source of the basanites of the Hana
Volcanics. Haleakala Crater basanites have average (230Th/238U) of 1.23 (n=13),
average age-corrected (226Ra/230Th) of 1.25 (n=13), and average (231Pa/235U) of 1.67
(n=4), significantly higher than Kilauea and Mauna Loa tholeiites. U-series modeling
shows that solid mantle upwelling velocity for Haleakala Crater basanites ranges
from ~0.7 to 1.0 cm/yr, compared to ~10 to 20 cm/yr for tholeiites and ~1 to 2
cm/yr for alkali basalts. These modeling results indicate that solid mantle upwelling
rates and porosity of the melting zone are lower for Hana Volcanics basanites than
for shield-stage tholeiites from Kilauea and Mauna Loa and alkali basalts from
Hualalai. The melting rate, which is directly proportional to both the solid mantle
upwelling rate and the degree of melting, is therefore greatest in the center of the
Hawaiian plume and lower on its periphery. Our results indicate that solid mantle
upwelling velocity is at least 10 times higher at the center of the plume than at its
periphery under Haleakala.
Description:
Funding for this project was provided by NSF grants EAR-0001924 and EAR-9909473 to KWWS.
Description:
2018-08-20
Repository Name:
Woods Hole Open Access Server
Type:
Preprint
Permalink