Volatile cycling of H₂O, CO₂, F, and Cl in the HIMU mantle: A new window provided by melt inclusions from oceanic hot spot lavas at Mangaia, Cook Islands

Abstract

Pb) mantle end-member, thought to result from recycled oceanic crust. Complete geochemical characterization of the HIMU mantle end-member has been inhibited due to a lack of deep submarine glass samples from HIMU localities. We homogenized olivine-hosted melt inclusions separated from Mangaia lavas and the resulting glassy inclusions made possible the first volatile abundances to be obtained from the HIMU mantle end-member. We also report major and trace element abundances and Pb-isotopic ratios on the inclusions, which have HIMU isotopic fingerprints. We evaluate the samples for processes that could modify the volatile and trace element abundances postmantle melting, including diffusive Fe and H 2 O loss, degassing, and assimilation. H 2 O/Ce ratios vary from 119 to 245 in the most pristine Mangaia inclusions; excluding an inclusion that shows evidence for assimilation, the primary magmatic H 2 O/Ce ratios vary up to 200, and are consistent with significant dehydration of oceanic crust during subduction and long-term storage in the mantle. CO 2 concentrations range up to 2346 ppm CO 2 in the inclusions. Relatively high CO 2 in the inclusions, combined with previous observations of carbonate blebs in other Mangaia melt inclusions, highlight the importance of CO 2 for the generation of the HIMU mantle. F/Nd ratios in the inclusions (30 6 9; 2r standard deviation) are higher than the canonical ratio observed in oceanic lavas, and Cl/K ratios (0.079 6 0.028) fall in the range of pristine mantle (0.02-0.08).

Variations in the H2O Content and H2O/Ce Ratio of Mantle Pyroxenites: Implications for Enriched Components in the Mantle

“…H 2 O, Ce content, and H 2 O/Ce are from these literatures. PM: McDonough and Sun () and Dixon and Clague (); DMM: Workman and Hart () and Salters and Stracke (); EM I: Kendrick et al (); EM II: Workman et al () and Kendrick et al (); HIMU: Cabral et al ().…”

Recycled oceanic crust and marine sediment in the source of alkali basalts in Shandong, eastern China: Evidence from magma water content and oxygen isotopes

“…Specifically, the EM‐I type hotspot lavas of the Pitcairn and Koolau end‐members in Hawaii exhibit H 2 O/Ce values of ~80 and ~111, respectively [ Kendrick et al , ; Dixon and Clague , ], while the EM‐II type lavas of Samoa and Society exhibit H 2 O/Ce values of ~50–80 [ Workman et al , ; Kendrick et al , , ]. In contrast, the HIMU type lavas have a higher H 2 O/Ce of ~200, and FOZO type components in the Atlantic and Pacific plume‐influenced MORB have H 2 O/Ce values of >250 and ~210, respectively [ Dixon et al , ; Métrich et al , ; Cabral et al , ]. Thus, it is clear that the EM‐type lavas have the lowest H 2 O/Ce ratios.…”

Deeply dredged submarine HIMU glasses from the Tuvalu Islands, Polynesia: Implications for volatile budgets of recycled oceanic crust

“…The lack of fresh, deeply dredged HIMU glass has been an impediment to developing a more complete understanding of the HIMU mantle. The recovery of the glasses reported here is important because volatile budgets of the HIMU mantle are critical for the generation of melts of this end‐member [ Jackson and Dasgupta , ; Dasgupta et al ., ; Gerbode and Dasgupta , ; Mallik and Dasgupta , ], and the volatile budgets of HIMU lavas may provide clues to how volatiles are cycled through the mantle, from subduction zones to hotspots [ Cabral et al ., ]. During residence on the seafloor, the uppermost portion of oceanic crust undergoes low‐temperature alteration and incorporation of volatiles (including several weight percent H 2 O and CO 2 ) [ Staudigel et al ., ; Alt and Teagle , ; Bach et al ., ; Wallmann , ; Dixon et al ., ; Gillis and Coogan , ].…”

“…For example, subducted upper continental crust is suggested to give rise to the EM2 mantle end‐member [ White and Hofmann , ; Jackson et al ., ; Workman et al ., ], but the origin of EM1 is not as well understood [ Weaver , ; Eiler et al ., ; Gasperini et al ., ; Eisele et al ., ; Honda and Woodhead , ; Geldmacher et al ., ; Salters and Sachi‐Kocher , ; Collerson et al ., ; Hart , ; Konter and Becker , ; Garapic et al ., ]. The HIMU mantle end‐member is characterized by the most radiogenic Pb‐isotopic compositions in the oceanic mantle, and is thought to originate from recycling of ancient subducted oceanic crust [e.g., Chase , ; Hofmann and White , ; Zindler et al ., ; Nakamura and Tatsumoto , ; Dupuy et al ., ; Graham et al ., ; Hauri and Hart , ; Hémond et al ., ; Roy‐Barman and Allègre , ; Woodhead , ; Hanyu and Kaneoka , ; Kogiso et al ., ; Salters and White , ; Schiano et al ., ; Lassiter et al ., ; Stracke et al ., ; Stroncik and Haase , ; Kelley et al ., ; Nishio et al ., ; Chan et al ., ; Parai et al ., ; Day et al ., ; John et al ., ; Hanyu et al ., ; Kawabata et al ., ; Salters et al ., ; Krienitz et al ., ; Cabral et al ., ]. Alternative mechanisms for generating the HIMU mantle have been proposed, including metasomatism, melting of lower mantle phases, and carbonate recycling [ Niu and O'Hara , ; Pilet et al ., ; Collerson et al ., ; Castillo , ].…”