Staudigel Hubert

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Age systematics of two young en echelon Samoan volcanic trails

2011-07-29 , Koppers, Anthony A. P. , Russell, Jamie A. , Roberts, Jed , Jackson, Matthew G. , Konter, Jasper G. , Wright, Dawn J. , Staudigel, Hubert , Hart, Stanley R.

The volcanic origin of the Samoan archipelago can be explained by one of three models, specifically, by a hot spot forming over a mantle plume, by lithospheric extension resulting from complex subduction tectonics in the region, or by a combination of these two processes, either acting sequentially or synchronously. In this paper, we present results of 36 high-resolution 40Ar/39Ar incremental heating age analyses for the initial (submarine) phase of Samoan volcanoes, ranging from 13.2 Ma for the westernmost Samoan seamounts to 0.27 Ma in the eastern Samoan volcanic province. Taken as a whole, our new age data point to a hot spot origin for the shield-building volcanism in the Samoan lineament, whereby seamounts younger than 5 Ma are consistent with a model of constant 7.1 cm/yr plate motion, analogous to GPS measurements for the Pacific Plate in this region. This makes our new 40Ar/39Ar ages of the submarine basalts all older compared to recent absolute plate motion (APM) models by Wessel et al. (2008), which are based on the inversion of twelve independent seamount trails in the Pacific relative to a fixed reference frame of hot spots and which predict faster plate motions of around 9.3 cm/yr in the vicinity of Samoa. The Samoan ages are also older than APM models by Steinberger et al. (2004) taking into account the motion of hot spots in the Pacific alone or globally. The age systematics become more complicated toward the younger end of the Samoan seamount trail, where its morphology bifurcates into two en echelon subtracks, termed the VAI and MALU trends, as they emanate from two eruptive centers at Vailulu'u and Malumalu seamount, respectively. Spaced ∼50 km apart, the VAI and MALU trends have distinct geochemical characters and independent but overlapping linear 40Ar/39Ar age progressions since 1.5 Ma. These phenomena are not unique to Samoa, as they have been observed at the Hawaiian hot spot, and can be attributed to a geochemical zoning in its underlying mantle source or plume. Moreover, the processes allowing for the emergence of two distinct eruptive centers in the Samoan archipelago, the stepped offset of these subtracks, and their slight obliqueness with respect to the overall seamount trail orientation may very well be controlled by local tectonics, stresses, and extension, also causing the rejuvenated volcanism on the main islands of Savai'i, Upolu, and Tutuila since 0.4 Ma.

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238U-Th-230-Ra-226-Pb-210-Po-210, Th-232-Ra-228, and U-235-Pa-231 constraints on the ages and petrogenesis of Vailulu'u and Malumalu Lavas, Samoa

2008-04-01 , Sims, Kenneth W. W. , Hart, Stanley R. , Reagan, Mark K. , Blusztajn, Jerzy S. , Staudigel, Hubert , Sohn, Robert A. , Layne, Graham D. , Ball, Lary A. , Andrews, J. E.

We report 238U-230Th-226Ra-210Pb-210Po, 232Th-228Ra and 235U-231Pa measurements for a suite of 14 geologically and geochemically well-characterized basaltic samples from the Samoan volcanoes Vailulu'u, Malumalu, and Savai'i. Maximum eruption ages based on the presence of parent-daughter disequilibria indicate that Vailulu'u is magmatically productive with young lavas (<8 Ka) resurfacing both its summit crater and lower flanks. 210Pb and 210Po measurements indicate that several flows have erupted within its summit crater in the past 100 years, with the newest observed flow being erupted in November of 2004. For lavas which have eruption ages that are demonstrably young, relative to the half-lives of 230Th, 231Pa, and 226Ra, we interpret their 238U -230Th, 235U-231Pa and 230Th - 226Ra disequilibria in terms of the magmatic processes occurring beneath the Samoan Islands. (230Th/238U) > 1 indicates that garnet is required as a residual phase in the magma sources for all these lavas. The large range of (238U/232Th) and (230Th/232Th) is attributed to long-term source variation. The Samoan basalts are all alkaline basalts and show significant 230Th and 231Pa excesses but limited variability, indicating that they have been derived by small but similar extents of melting. Their (230Th/238U), (231Pa/235U) and Sm/Nd fractionation are consistent with correlations among other ocean island basalt suites (particularly Hawaii) which show that (230Th/238U) and (231Pa/235U) of many OIBS can be explained by simple time-independent models. Interpretation of the 226Ra data requires time-dependent melting models. Both chromatographic porous flow and dynamic melting of a garnet peridotite source can adequately explain the combined U-Th-Ra and U-Pa data for these Samoan basalts. Several young samples from the Vailulu'u summit crater also exhibit significant 210Pb deficits that reflect either shallow magmatic processes or continuous magma degassing. In both cases, decadal residence times are inferred from these 210Pb deficits. The young coeval volcanism on Malumalu and Vailulu'u suggests the Samoa hot spot is currently migrating to the northeast due to dynamic interaction with the Tonga slab.

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Article

Hydrothermal venting at Vailulu'u Seamount : the smoking end of the Samoan chain

2004-02-10 , Staudigel, Hubert , Hart, Stanley R. , Koppers, Anthony A. P. , Constable, C. , Workman, Rhea K. , Kurz, Mark D. , Baker, Edward T.

The summit crater of Vailulu'u Seamount, the youngest volcano in the Samoan chain, hosts an active hydrothermal system with profound impact on the ocean water column inside and around its crater (2 km wide and 407 m deep at a 593 m summit depth). The turbidity of the ocean water reaches 1.4 NTU, values that are higher than in any other submarine hydrothermal system. The water is enriched in hydrothermal Mn (3.8 ppb) and 3He (1 × 10−11 cc/g) and we measured water temperature anomalies near the crater floor up to 0.2°C. The hydrothermal system shows complex interactions with the ocean currents around Vailulu'u that include tidally-modulated vertical motions of about 40–50 m, and replenishment of waters into the crater through breaches in the upper half of the crater wall. Inside and outside potential density gradients suggest that hydrothermal venting exports substantial amounts of water from the crater (1.3 ± 0.2 × 108 m3/day), which is in good agreement with fluxes obtained from a tracer release experiment inside the crater of Vailulu'u (0.8 × 108 m3/day [Hart et al., 2003]). This mass flux, in combination with the differences in the inside and outside crater temperature, yields a power output of around 760 megawatts, the equivalent of 20–100 MOR black smokers. The Mn output of 300 kg/day is approximately ten times the output of a single black smoker.

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Vailulu’u Seamount

2010-03 , Koppers, Anthony A. P. , Staudigel, Hubert , Hart, Stanley R. , Young, Craig M. , Konter, Jasper G.

Vailulu’u seamount is an active underwater volcano that marks the end of the Samoan hotspot trail.

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Preprint

The return of subducted continental crust in Samoan lavas

2007-08-04 , Jackson, Matthew G. , Hart, Stanley R. , Koppers, Anthony A. P. , Staudigel, Hubert , Konter, Jasper G. , Blusztajn, Jerzy S. , Kurz, Mark D. , Russell, Jamie A.

Substantial quantities of terrigenous sediments are known to enter the mantle at subduction zones, but little is known about their fate in the mantle. Subducted sediment may be entrained in buoyantly upwelling plumes and returned to the earth’s surface at hotspots, but the proportion of recycled sediment in the mantle is small and clear examples of recycled sediment in hotspot lavas are rare. We report here remarkably enriched 87Sr/86Sr and 143Nd/144Nd isotope signatures (up to 0.720830 and 0.512285, respectively) in Samoan lavas from three dredge locations on the underwater flanks of Savai’i island, Western Samoa. The submarine Savai’i lavas represent the most extreme 87Sr/86Sr isotope compositions reported for ocean island basalts (OIBs) to date. The data are consistent with the presence of a recycled sediment component (with a composition similar to upper continental crust, or UCC) in the Samoan mantle. Trace element data show similar affinities with UCC—including exceptionally low Ce/Pb and Nb/U ratios—that complement the enriched 87Sr/86Sr and 143Nd/144Nd isotope signatures. The geochemical evidence from the new Samoan lavas radically redefines the composition of the EM2 (enriched mantle 2) mantle endmember, and points to the presence of an ancient recycled UCC component in the Samoan plume.

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Article

Seafloor seismic monitoring of an active submarine volcano : local seismicity at Vailulu'u Seamount, Samoa

2004-06-26 , Konter, Jasper G. , Staudigel, Hubert , Hart, Stanley R. , Shearer, Peter M.

We deployed five ocean bottom hydrophones (OBHs) for a 1-year seismic monitoring study of Vailulu'u Seamount, the youngest and easternmost volcano in the Samoan Archipelago. Four instruments were placed on the summit crater rim at 600–700 m water depth, and one was placed inside the crater at 1000 m water depth. An analysis of the first 45 days of records shows a very large number of seismic events, 211 of them local. These events define a steady background activity of about four seismic events per day, increasing to about 10 events per day during a week of heightened seismic activity, which peaked at 40 events during 1 day. We identified 107 earthquakes, whose arrivals could be picked on all five stations and that are likely located within the seamount, based on their similar waveforms. Two linear trends are defined by 21 of these events. These are extremely well correlated and located, first downward then upward on a steeply inclined plane that is close to the axial plane of the southeast rift as it emerges from the main summit of Vailulu'u. These events resemble volcanotectonic earthquakes from subaerial volcanoes in displaying very coherent seismic waveforms and by showing systematic, narrowly defined progressions in hypocenter locations. We propose that these events reflect brittle rock failure due to magma redistribution in or near a central magma reservoir.

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Article

Recycled metasomatized lithosphere as the origin of the Enriched Mantle II (EM2) end-member : evidence from the Samoan Volcanic Chain

2004-04-27 , Workman, Rhea K. , Hart, Stanley R. , Jackson, Matthew G. , Regelous, Marcel , Farley, Kenneth A. , Blusztajn, Jerzy S. , Kurz, Mark D. , Staudigel, Hubert

An in-depth Sr-Nd-Pb-He-Os isotope and trace element study of the EMII-defining Samoan hot spot lavas leads to a new working hypothesis for the origin of this high 87Sr/86Sr mantle end-member. Systematics of the Samoan fingerprint include (1) increasing 206Pb/204Pb with time - from 18.6 at the older, western volcanoes to 19.4 at the present-day hot spot center, Vailulu'u Seamount, (2) en-echelon arrays in 206Pb/204Pb – 208Pb/204Pb space which correspond to the two topographic lineaments of the 375 km long volcanic chain – this is much like the Kea and Loa Trends in Hawai'i, (3) the highest 87Sr/86Sr (0.7089) of all oceanic basalts, (4) an asymptotic decrease in 3He/4He from 24 RA [Farley et al., 1992] to the MORB value of 8 RA with increasing 87Sr/86Sr, and (5) mixing among four components which are best described as the “enriched mantle”, the depleted FOZO mantle, the (even more depleted) MORB Mantle, and a mild HIMU (high 238U/204Pb) mantle component. A theoretical, “pure” EMII lava composition has been calculated and indicates an extremely smooth trace element pattern of this end-member mantle reservoir. The standard recycling model (of ocean crust/sediment) fails as an explanation for producing Samoan EM2, due to these smooth spidergrams for EM2 lavas, low 187Os/188Os ratios and high 3He/4He (>8 RA). Instead, the origin of EM2 has been modeled with the ancient formation of metasomatised oceanic lithosphere, followed by storage in the deep mantle and return to the surface in the Samoan plume.

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Article

Vailulu'u Seamount, Samoa : life and death on an active submarine volcano

2006-04-13 , Staudigel, Hubert , Hart, Stanley R. , Pile, Adele , Bailey, Bradley E. , Baker, Edward T. , Brooke, Sandra , Connelly, Douglas P. , Haucke, Lisa , German, Christopher R. , Hudson, Ian , Jones, Daniel O. B. , Koppers, Anthony A. P. , Konter, Jasper G. , Lee, Ray , Pietsch, Theodore W. , Tebo, Bradley M. , Templeton, Alexis S. , Zierenberg, Robert , Young, Craig M.

Submersible exploration of the Samoan hotspot revealed a new, 300-m-tall, volcanic cone, named Nafanua, in the summit crater of Vailulu'u seamount. Nafanua grew from the 1,000-m-deep crater floor in <4 years and could reach the sea surface within decades. Vents fill Vailulu'u crater with a thick suspension of particulates and apparently toxic fluids that mix with seawater entering from the crater breaches. Low-temperature vents form Fe oxide chimneys in many locations and up to 1-m-thick layers of hydrothermal Fe floc on Nafanua. High-temperature (81°C) hydrothermal vents in the northern moat (945-m water depth) produce acidic fluids (pH 2.7) with rising droplets of (probably) liquid CO2. The Nafanua summit vent area is inhabited by a thriving population of eels (Dysommina rugosa) that feed on midwater shrimp probably concentrated by anticyclonic currents at the volcano summit and rim. The moat and crater floor around the new volcano are littered with dead metazoans that apparently died from exposure to hydrothermal emissions. Acid-tolerant polychaetes (Polynoidae) live in this environment, apparently feeding on bacteria from decaying fish carcasses. Vailulu'u is an unpredictable and very active underwater volcano presenting a potential long-term volcanic hazard. Although eels thrive in hydrothermal vents at the summit of Nafanua, venting elsewhere in the crater causes mass mortality. Paradoxically, the same anticyclonic currents that deliver food to the eels may also concentrate a wide variety of nektonic animals in a death trap of toxic hydrothermal fluids.

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