Louisville Seamount Chain: Petrogenetic processes and geochemical evolution of the mantle source

Abstract

The Louisville Seamount Chain is a 4300 km long chain of submarine volcanoes in the southwestern Pacific that spans an age range comparable to that of the Hawaiian-Emperor chain and is commonly thought to represent a hot spot track. Dredging in 2006 recovered igneous rocks from 33 stations on 22 seamounts covering some 49 Myr of the chain's history. All samples are alkalic, similar to previous dredge and drill samples, providing no evidence for a Hawaiian-type tholeiitic shield-volcano stage. Major and trace element variations appear to be predominantly controlled by small but variable extents of fractional crystallization and by partial melting. Isotopic values define only a narrow range, in agreement with a surprising long-term source homogeneity-relative to the length scale of melting-and overlap with proposed fields for the ''C'' and ''FOZO'' mantle end-members. Trace element and isotope geochemistry is uncorrelated with either seamount age or lithospheric thickness at the time of volcanism, except for a small number of lavas from the westernmost Louisville Seamounts built on young (<20 Ma old) oceanic crust. The Louisville hot spot has been postulated to be the source of the 120 Ma Ontong Java Plateau, but the Louisville isotopic signature cannot have evolved from a source with isotopic ratios like those measured for Ontong Java Plateau basalts. On the other hand, this signature can be correlated with that of samples dredged from the Danger Islands Troughs of the Manihiki Plateau, which has been interpreted as a rifted fragment of the ''Greater'' Ontong Java Plateau.

Re‐Os isotope and platinum group elements of a FOcal ZOne mantle source, Louisville Seamounts Chain, Pacific ocean

“… Total alkali versus SiO 2 plot for LSC basalts analyzed for Os isotopes and Re and platinum group element (PGE) abundances showing the slightly different composition of samples from Rigil seamount. Also shown are data fields for the dredged samples from Louisville seamounts [ Cheng et al ., ; Hawkins et al ., ; Beier et al ., ; Vanderkluysen et al ., ], Ontong Java Plateau (OJP) tholeiites [ Fitton and Godard , ], and the associated alkalic rocks from the Solomon Islands (YS = Younger Series, NMA = North Malaita Alkalics, SA = Sigana Alkalics) [ Tejada et al ., ], and Lyra Basin (LB) [ Tejada et al ., ] for reference.…”

“…One of the striking characteristics of the LSC is the almost uniform isotopic composition of its volcanic products along the chain [ Cheng et al ., ; Beier et al ., ; Vanderkluysen et al ., ], except for the seamounts in the vicinity of the Wishbone Scarp (Figure ) [ Beier et al ., ]. The limited range in the age‐corrected Os isotopic compositions for the Louisville seamount samples compared to other OIBs (Table ; Figure ) is in excellent agreement with Pb, Nd, Hf, and Sr isotope data.…”

“…The other point of interest is the nature of the source, which up until now has had very limited support for a deep‐rooted mantle [e.g., Hanyu , ] with little influence from heterogeneities found in most ocean island basalts (OIB). For example, isotopic and trace element data suggest a long‐lived and remarkably homogeneous mantle source quite distinct from that of mid‐ocean ridge basalts (MORB) [ Cheng et al ., ; Hawkins et al ., ; Beier et al ., ; Vanderkluysen et al ., ] and, combined with the age‐progressive volcanism [ Koppers et al ., ], led these workers to suggest a source with an affinity to the FOcal ZOne (FOZO) [ Hart et al ., ] mantle inferred to represent a common component in the source of OIBs. Finally, Expedition 330 was expected to shed further light on the inferred link with the Ontong Java Plateau (OJP) emplacement as the potential plume‐head stage of the Louisville hotspot development.…”

Accreted seamounts in North Tianshan, NW China: Implications for the evolution of the Central Asian Orogenic Belt

“…Recent discoveries indicate that enriched basalts are not only limited to mantle plumes but can be found in oceanic spreading ridges (Niu et al, 2002;Hemond et al, 2006;Nauret et al, 2006), and in some arc-related settings (Kita et al, 2001;Scott et al, 2002) such as slab roll-back (Ferrari et al, 2001), arc rifting and deep water cycle model (Ivanov and Litasov, 2014). Moreover, Hirano et al (2006) proposed that the small alkaline volcanoes erupt along lithospheric fractures in response to plate flexure White and Duncan (1996), Louisville from Vanderkluysen et al (2014), OIB and MORB compositions are from Sun and McDonough (1989). during subduction. In our previous studies we discussed the occurrences of alkaline basalts hosted by ophiolitic mélanges in the West Junggar and suggested that the plume-related magmatism developed during the evolution of the Junggar ocean as well as paleo-Asian Ocean (Yang et al, 2012b(Yang et al, , 2013(Yang et al, , 2015.…”

“…Regardless of how they are formed seamounts migrate with the ocean plates and eventually reach active convergent margins (von Huene, 2008;. However, because they represent areas of thicker-than-normal oceanic crust, they often accrete on the margin of subduction zones (Hoernle et al, 2002;Buchs et al, 2011).…”