The behavior of chalcophile elements during magmatic differentiation as observed in Kilauea Iki lava lake, Hawaii

作者：Greaney Allison T^*; Rudnick Roberta L; Helz Rosalind T; Gaschnig Richard M; Piccoli Philip M; Ash Richard D

来源：Geochimica et Cosmochimica Acta, 2017, 210: 71-96.

DOI：10.1016/j.gca.2017.04.033

• Chalcophile element
• Partitioning
• Differentiation
• Kilauea Iki lava lake
• Molybdenum

We quantify the behavior of Cu, Ga, Ge, As, Mo, Ag, Cd, In, Sn, Sb, W, Tl, Pb, and Bi during the differentiation of a picritic magma in the Kilauea Iki lava lake, Hawaii, using whole rock and glass differentiation trends, as well as partition coefficients in Cu-rich sulfide blebs and minerals. Such data allow us to constrain the partitioning behavior of these elements between sulfide and silicate melts, as well as the chalcophile element characteristics of the mantle source of the Kilauea lavas. Nearly all of the elements are generally incompatible on a whole-rock scale, with concentrations increasing exponentially below similar to 6 wt% MgO. However, in-situ laser ablation data reveal that Cu, Ag, Bi, Cd, In, Pb, and Sn are chalcophile; As, Ge, Sb, and Tl are weakly chalcophile to lithophile; and Mo, Ga, and W are lithophile. The average D-sulfide/silicate (melt) values are: D-Ag = 1252 +/- 1201 (2SD), D-Bi = 663 +/- 576, D-Cd = 380 +/- 566, D-In = 40 +/- 34, D-Pb = 34 +/- 18, D-Sn = 5.3 +/- 3.6, D-As = 2.4 +/- 7.6, D-Ge = 1.6 +/- 1.4, D-Sb = 1.3 +/- 1.5, D-Tl = 1.1 +/- 1.7, D-Mo = 0.56 +/- 0.6, D-Ga = 0.10 +/- 0.3, and D-W = 0.11 +/- 0.1. These findings are consistent with experimental partitioning studies and observations of Ni-rich sulfide liquid in mid-ocean ridge basalts (MORB), despite the different compositions of the KI sulfides. The KI glasses and whole rocks are enriched in As, Ag, Sb, W, and Bi, relative to elements of similar compatibility (as established by abundances in MORB), mimicking enrichments found in basalts from the Manus back arc basin (Jenner et al., 2012) and the upper continental crust (UCC). These enrichments suggest the presence of terrigenous sediments in the Kilauea mantle source. The KI source is calculated to be a mixture of depleted MORB mantle (DMM) and 10-20% recycled crust composed of MORB and minor terrigenous sediments.

• 出版日期2017-8-1