The size of plume heterogeneities constrained by Marquesas isotopic stripes

Abstract

The scale and geometry of chemical and isotopic heterogeneities in the source of plumes have important scientific implications on the nature, composition and origin of plumes and on the dynamics of mantle mixing over time. Here, we address these issues through the study of Marquesas Islands, one of the Archipelagoes in Polynesia. We present new Sr, Nd, Pb, Hf isotopes as well as trace element data on lavas from several Marquesas Islands and demonstrate that this archipelago consists of two adjacent and distinct rows of islands with significantly different isotopic compositions. For the entire 5.5 Ma construction period, the northern islands, hereafter called the Ua Huka group, has had systematically higher 87Sr/86Sr and lower 206Pb/204Pb ratios than the southern Fatu Hiva group at any given 143Nd/144Nd value. The shape and curvature of mixing arrays preclude the ambient depleted MORB mantle as one of the mixing end‐members. We believe therefore that the entire isotopic heterogeneity originates in the plume itself. We suggest that the two Marquesas isotopic stripes originate from partial melting of two adjacent filaments contained in small plumes or “plumelets” that came from a large dome structure located deep in the mantle under Polynesia. Low‐degree partial melting under Marquesas and other “weak” Polynesian hot spot chains (Pitcairn‐Gambier, Austral‐Cook, Society) sample small areas of the dome and preserve source heterogeneities. In contrast, more productive hot spots build up large islands such as Big Island in Hawaii or Réunion Island, and the higher degrees of melting blur the isotopic variability of the plume source.

Combined petrological, geochemical and isotopic modeling of a plume source: Example of Gambier Island, Pitcairn chain

“…Similar Pb isotopic compositions and elevated Ce/Pb or Nb/La ratios have been reported for other OIB in the world: Ua Pou, Motane, Fatu Hiva and Tahuata in the Marquesas Archipelago Chauvel et al, 2012) and Azores, Cape Verde and Canary Islands in the Atlantic (Thirlwall, 1997;Simonsen et al, 2000;Holm et al, 2006) (see Fig. 2).…”

“…Magma production is low compared to Hawaii (respectively ∼30,000 km 3 /yr versus ∼110,000 km 3 /yr, Chauvel et al, 2012) and controlled by intermittent eruptions that cannot be described by a 'simple' plume model as defined by Morgan (1972). In addition, the isotopic data published on Polynesian lavas define a very large range that is similar to the entire field known for oceanic islands (Vidal et al, 1984;Palacz and Saunder, 1986;Weaver, 1991;Chauvel et al, 1992Chauvel et al, , 2012Woodhead and Devey, 1993;Hémond et al, 1994;White and Duncan, 1996;Dostal et al, 1998;Lassiter et al, 2003). So the question can be asked of how the rather weak Polynesian Superplume compares to the classical Hawaiian model?…”

“…Synchronous eruptions (Guillou et al, , 2014Maury et al, 2013) (Marquesas, Society, Austral-Cook and Pitcairn-Gambier) located above a large low shear velocity seismic anomaly at the coremantle boundary (Gu et al, 2001;Romanowicz and Gung, 2002;Lekic et al, 2012). Magma production is low compared to Hawaii (respectively ∼30,000 km 3 /yr versus ∼110,000 km 3 /yr, Chauvel et al, 2012) and controlled by intermittent eruptions that cannot be described by a 'simple' plume model as defined by Morgan (1972). In addition, the isotopic data published on Polynesian lavas define a very large range that is similar to the entire field known for oceanic islands (Vidal et al, 1984;Palacz and Saunder, 1986;Weaver, 1991;Chauvel et al, 1992Chauvel et al, , 2012Woodhead and Devey, 1993;Hémond et al, 1994;White and Duncan, 1996;Dostal et al, 1998;Lassiter et al, 2003).…”

High-precision lead isotopes and stripy plumes: Revisiting the Society chain in French Polynesia

“…In some cases, isotopic compositions present a spatial organization with parallel and synchronous isotopic stripes, as suggested for Hawaii, Marquesas, Samoa, Society and Galápagos Islands in the Pacific or in Tristan-Gough Islands in the Atlantic Ocean (Abouchami et al, 2000;Hoernle et al, 2000;Workman et al, 2004;Abouchami et al, 2005;Huang et al, 2011;Weis et al, 2011;Chauvel et al, 2012;Payne et al, 2013;Rohde et al, 2013;Harpp et al, 2014).…”

Probing the Earth’s Deep Interior Through Geochemistry

“…There is also evidence of dual tracks with distinct isotopic compositions persisting in the Marquesas (Desonie et al, 1993;Chauvel et al, 2012) and the Society Islands (Payne et al, 2013) for the entire history of the hot spot tracks, 5 and 4 million years, respectively. Two tracks have been identified in Samoa (Workman et al, 2004;Huang et al, 2011;Jackson et al, 2014), but the northern Vai chain appeared only about 2.1 million years ago.…”