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Huang, KJ, Teng FZ, Plank T, Staudigel H, Hu Y, Bao ZY.  2018.  Magnesium isotopic composition of altered oceanic crust and the global Mg cycle. Geochimica Et Cosmochimica Acta. 238:357-373.   10.1016/j.gca.2018.07.011   AbstractWebsite

To investigate the behavior of Mg isotopes during low-temperature alteration of oceanic crust and to further under- stand its role in the global Mg cycle, we measured the Mg isotopic compositions (Mg-25/Mg-24 and Mg-26/Mg-24) of a set of samples of altered oceanic crust (AOC) recovered from the Ocean Drilling Program Hole 801C, the reference site for old crust (similar to 170 Ma) subducting in the Pacific. The measured delta Mg-26 values range from -1.70 parts per thousand to 0.21 parts per thousand, deviating from that of pristine oceanic basalts (-0.25 +/- 0.07 parts per thousand). Composite samples of volcanoclastic breccia that have experienced relatively intense alteration have larger variation in delta Mg-26 values (-1.01 parts per thousand to 0.15 parts per thousand) than composite samples of massive basaltic flows (-0.53 parts per thousand to -0.04 parts per thousand), indicating significant Mg isotope fractionation during low-temperature alteration of the oceanic crust. Moreover, the upper off-axis basement has on average lower delta Mg-26 values (-1.70 parts per thousand to -0.04 parts per thousand) than the lower on-axis basement (-0.16 parts per thousand to 0.21 parts per thousand). These findings, combined with the co-variations between MgO content and Fe O-x/CaO ratio and between delta Mg-26 and FeOx/CaO ratio, suggest that formation of Mg-bearing minerals (i.e., saponite and calcite) during low-temperature alteration of the oceanic crust accounts for the highly variable delta Mg-26 of AOC. Early formation of saponite under anoxic condition preferentially takes up heavy Mg isotopes and accounts for Mg enrichment and relatively high delta Mg-26 in the on-axis basement. Subsequent precipitation of carbonates results in the dilution of Mg and relatively low delta Mg-26 in the off-axis basement. In addition, accumulation of carbonate-rich interflow sediments in the upper basement may contribute further to the low delta Mg-26. A weighted average delta Mg-26 value of 0.00 +/- 0.09 parts per thousand is estimated for the AOC at Site 801, implying that low-temperature alteration of oceanic crust drives the ocean to a lighter Mg isotopic composition, and thus requires additional carbonate precipitation to maintain a steady-state Mg isotopic composition of seawater. A mass balance calculation suggests that the Mg output flux due to low-temperature alteration of the oceanic crust equals similar to 12% of the annual Mg riverine input, indicating that AOC is a significant sink of Mg in seawater. Our study further highlights that recycling of AOC with highly variable delta Mg-26 m along with overlying marine sediments into the mantle through subduction may generate Mg isotopic heterogeneity in the mantle at small scales. (C) 2018 Elsevier Ltd. All rights reserved.

Cromwell, G, Trusdell F, Tauxe L, Staudigel H, Ron H.  2018.  Holocene paleointensity of the island of Hawai'i from glassy volcanics. Geochemistry Geophysics Geosystems. 19:3224-3245.   10.1002/2017gc006927   AbstractWebsite

This study presents new high-quality paleointensity records and C-14 radiocarbon age determinations from the Island of Hawai'i during the Holocene. Previous studies on Hawai'i use experimental methods and statistical selection criteria that may produce inaccurate geomagnetic field strength estimates. Additional high-quality paleointensity results can be used to evaluate the existing Hawaiian data set and investigate Holocene geomagnetic field behavior. New paleointensity sites from 22 lava flows were calculated using the IZZI-Thellier laboratory technique and a strict set of selection criteria. Rapidly cooled, glassy volcanic material was collected for all sites. Isotopic age determinations range from 270 to > 10, 000 years before present (nine new C-14 ages are also presented as part of this study). The median intensity for the 22 flows is 47.5 mu T, with a median absolute deviation uncertainty of 5.6 mu T; substantially greater than the present-day field strength at Hawai'i (similar to 36 mu T). These new results are comparable to previously published data from this location and are consistent with global paleointensity models. There is no evidence of an intensity "spike" at 3,000 years before present, as seen in the Levant and elsewhere. Previously published data vary in intensity by experimental technique relative to data using glassy material and strict selection criteria. Non-Thellier-type data are biased low, a result of these techniques estimating intensity from possibly nonsingle domain magnetic carriers. Thellier-Thellier data are biased high, the reasons for which remain unclear as no cooling rate effect was demonstrated, and we were unable to reproduce the high bias with different selection criteria.

Pedersen, LER, Staudigel H, McLoughlin N, Whitehouse MJ, Strauss H.  2017.  A multiple sulfur isotope study through the volcanic section of the Troodos ophiolite. Chemical Geology. 468:49-62.   10.1016/j.chemgeo.2017.08.008   AbstractWebsite

Multiple S isotope systematics (delta S-34 and Delta S-33) and high resolution in-situ S isotope measurements offer new perspectives on the study of biological and abiotic cycling of sulfur in hydrothermal systems. We applied these techniques to the Tethyian Troodos ophiolite (91 Ma) from Cyprus, one of the best-preserved remnants of oceanic crust in the world, using materials from deep drill cores and surface sampling. We focused on the volcanic section of the ophiolite, including the hydrothermal massive sulfide deposit at Agrokipia, which represents a fossil zone of high-temperature fluid upwelling, and the Akaki river section which displays a range of lower temperature alteration types. The delta S-34 and Delta S-33 values of bulk and SIMS (secondary ion mass spectrometry) analyses from the Agrokipia sulfide deposits show that the sulfide minerals are largely derived from thermochemical reduction of entrained seawater sulfate and leached H2S from the "root zone" of hydrothermal upwelling. The contributions of these two sources can vary substantially within individual sulfide grains, indicating a very dynamic mixing between these sulfur sources. Microbial reworking of the sulfide mound is recorded in a sample with very elevated 4335 values (0.22 parts per thousand). The Akaki and Agrokipia volcanics experienced low temperature sulfur loss and removal of heavier sulfur isotopes due to partial oxidation by microbes. While some intervals gained sulfur, and have delta S-34 and Delta S-33 values indicative of microbial sulfate reduction. REE-data of vein quartz containing pyrite with delta S-34 = similar to 21 parts per thousand implies local ephemeral hydrothermal upwelling in the lower Akaki volcanics, possibly associated with the late stage boninitic magmatic activity in the Troodos ophiolite, suggesting that microbial sulfate reduction in oceanic crust may continue for 10-15 Ma in crustal sections with prolonged igneous activity such as Troodos.

Sudek, LA, Wanger G, Templeton AS, Staudigel H, Tebo BM.  2017.  Submarine basaltic glass colonization by the heterotrophic Fe(II)-Oxidizing and siderophore-producing deep-sea bacterium Pseudomonas stutzeri VS-10: The potential role of basalt in enhancing growth. Frontiers in Microbiology. 8   10.3389/fmicb.2017.00363   AbstractWebsite

Phylogenetically and metabolically diverse bacterial communities have been found in association with submarine basaltic glass surfaces. The driving forces behind basalt colonization are for the most part unknown. It remains ambiguous if basalt provides ecological advantages beyond representing a substrate for surface colonization, such as supplying nutrients and/or energy. Pseudomonas stutzeri VS-10, a metabolically versatile bacterium isolated from Vailulu'u Seamount, was used as a model organism to investigate the physiological responses observed when biofilms are established on basaltic glasses. In Fe-limited heterotrophic media, P. stutzeri VS-10 exhibited elevated growth in the presence of basaltic glass. Diffusion chamber experiments demonstrated that physical attachment or contact of soluble metabolites such as siderophores with the basaltic glass plays a pivotal role in this process. Electrochemical data indicated that P. stutzeri VS-10 is able to use solid substrates (electrodes) as terminal electron donors and acceptors. Siderophore production and heterotrophic Fe(II) oxidation are discussed as potential mechanisms enhancing growth of P. stutzeri VS-10 on glass surfaces. In correlation with that we discuss the possibility that metabolic versatility could represent a common and beneficial physiological trait in marine microbial communities being subject to oligotrophic and rapidly changing deep-sea conditions.

Staudigel, H, Furnes H, DeWit M.  2015.  Paleoarchean trace fossils in altered volcanic glass. Proceedings of the National Academy of Sciences.   10.1073/pnas.1421052112   AbstractWebsite

Microbial corrosion textures in volcanic glass from Cenozoic seafloor basalts and the corresponding titanite replacement microtextures in metamorphosed Paleoarchean pillow lavas have been interpreted as evidence for a deep biosphere dating back in time through the earliest periods of preserved life on earth. This interpretation has been recently challenged for Paleoarchean titanite replacement textures based on textural and geochronological data from pillow lavas in the Hooggenoeg Complex of the Barberton Greenstone Belt in South Africa. We use this controversy to explore the strengths and weaknesses of arguments made in support or rejection of the biogenicity interpretation of bioalteration trace fossils in Cenozoic basalt glasses and their putative equivalents in Paleoarchean greenstones. Our analysis suggests that biogenicity cannot be taken for granted for all titanite-based textures in metamorphosed basalt glass, but a cautious and critical evaluation of evidence suggests that biogenicity remains the most likely interpretation for previously described titanite microtextures in Paleoarchean pillow lavas.

Cromwell, G, Tauxe L, Staudigel H, Ron H.  2015.  Paleointensity estimates from historic and modern Hawaiian lava flows using glassy basalt as a primary source material. Physics of the Earth and Planetary Interiors. 241:44-56.   10.1016/j.pepi.2014.12.007   AbstractWebsite

Published paleointensity estimates derived from lavas extruded in known fields are highly variable and rarely recover the expected field strength within an accuracy of better than 10%. Inconsistent results on modern volcanic rocks lend even greater uncertainty to intensity experiments performed on lava flows emplaced during periods of unknown geomagnetic field strength. The majority of published paleointensity data are collected from the slowly cooled, massive centers of lava flows, where the magnetic grains are more likely to be multi-domain and produce non-ideal experimental results. Glassy volcanic material (found on subaerial lava flow tops and in sub-aqueous and subglacial environments), however is rapidly cooled, and therefore most likely of all volcanic materials to behave as single-domain particles demanded by Néel theory. We present a new paleointensity study of historic and modern Hawaiian lavas and test the viability of subaerially emplaced glassy basaltic material as an accurate recorder of magnetic field intensity. Six of eight lava flows sampled on the Big Island of Hawaii (1843, 1859, 1935, 1950, 1960, 1990 C.E.) produce well behaved Arai plots and recover an average intensity to within 2.7 μT of the expected field strength or better than 8% accuracy. We apply very strict selection criteria, including a minimum of three specimens per site, to prevent extraneous field estimates from affecting the final results. Individual volcanic glass results from the 1960 C.E. lava flow have a much lower variance than published data from the same volcanic unit. Glassy materials should therefore be collected wherever possible as they allow recovery of geomagnetic field strength with unprecedented accuracy.

Tebo, BM, Davis RE, Anitori RP, Conne LB, Schiffman P, Staudigel H.  2015.  Microbial communities in dark oligotrophic volcanic ice cave ecosystems of Mt. Erebus, Antarctica. Frontiers in Microbiology. 6   10.3389/fmicb.2015.00179   AbstractWebsite

The Earth's crust hosts a subsurface, dark, and oligotrophic biosphere that is poorly understood in terms of the energy supporting its biomass production and impact on food webs at the Earth's surface. Dark oligotrophic volcanic ecosystems (DOVEs) are good environments for investigations of life in the absence of sunlight as they are poor in organics, rich in chemical reactants and well known for chemical exchange with Earth's surface systems. Ice caves near the summit of Mt. Erebus (Antarctica) offer DOVEs in a polar alpine environment that is starved in organics and with oxygenated hydrothermal circulation in highly reducing host rock. We surveyed the microbial communities using PCR, cloning, sequencing and analysis of the small subunit (16S) ribosomal and Ribulose-1,5-bisphosphate Carboxylase/Oxygenase (RubisCO) genes in sediment samples from three different caves, two that are completely dark and one that receives snow-filtered sunlight seasonally. The microbial communities in all three caves are composed primarily of Bacteria and fungi; Archaea were not detected. The bacterial communities from these ice caves display low phylogenetic diversity, but with a remarkable diversity of RubisCO genes including new deeply branching Form I clades, implicating the Calvin-Benson-Bassham (CBB) cycle as a pathway of CO2 fixation. The microbial communities in one of the dark caves, Warren Cave, which has a remarkably low phylogenetic diversity, were analyzed in more detail to gain a possible perspective on the energetic basis of the microbial ecosystem in the cave. Atmospheric carbon (CO2 and CO), including from volcanic emissions, likely supplies carbon and/or some of the energy requirements of chemoautotrophic microbial communities in Warren Cave and probably other Mt. Erebus ice caves. Our work casts a first glimpse at Mt. Erebus ice caves as natural laboratories for exploring carbon, energy and nutrient sources in the subsurface biosphere and the nutritional limits on life.

Staudigel, H, Furnes H, Smits M.  2014.  Deep biosphere record of in situ oceanic lithosphere and ophiolites. Elements. 10:121-126.   10.2113/gselements.10.2.121   AbstractWebsite

Volcanic glass from pillow lavas and hyaloclastites displays distinctive alteration textures that suggest the activity of boring microbes. Analogous textures are common in volcanic sections of the seafloor, in ophiolites, and in greenstone belts up to 3.5 Ga in age. While the origin of such trace fossils remains poorly understood, they offer much potential for investigating processes in the present-day, deep-ocean, crustal biosphere and their role in biogeochemical cycles.

Cromwell, G, Constable CG, Staudigel H, Tauxe L, Gans P.  2013.  Revised and updated paleomagnetic results from Costa Rica. Geochemistry Geophysics Geosystems. 14:3379-3388.   10.1002/ggge.20199   AbstractWebsite

Paleomagnetic results from globally distributed lava flows have been collected and analyzed under the time-averaged field initiative (TAFI), a multi-institutional collaboration started in 1996 and designed to improve the geographic and temporal coverage of the 0-5 Ma paleomagnetic database for studying both the time-averaged field and its very long-term secular variations. Paleomagnetic samples were collected from 35 volcanic units, either lava flows or ignimbrites, in Costa Rica in December 1998 and February 2000 from the Cordilleras Central and Guanacaste, the underlying Canas, Liberia and Bagaces formations and from Volcano Arenal. Age estimates range from approximately 40 ka to slightly over 6 Ma. Although initial results from these sites were used in a global synthesis of TAFI data by Johnson et al. (2008), a full description of methodology was not presented. This paper documents the definitive collection of results comprising 28 paleomagnetic directions (24 normal, 4 reversed), with enhanced precision and new geological interpretations, adding two paleointensity estimates and 19 correlated Ar-40/Ar-39 radiometric ages. The average field direction is consistent with that of a geocentric axial dipole and dispersion of virtual geomagnetic poles (17.34.6 degrees) is in general agreement with predictions from several statistical paleosecular variation models. Paleointensity estimates from two sites give an average field strength of 26.3 T and a virtual axial dipole moment of 65 ZAm(2). The definitive results provide a useful augmentation of the global database for the longer term goal of developing new statistical descriptions of paleomagnetic field behavior.

Cromwell, G, Tauxe L, Staudigel H, Constable CG, Koppers AAP, Pedersen RB.  2013.  In search of long-term hemispheric asymmetry in the geomagnetic field : Results from high northern latitudes. Geochemistry Geophysics Geosystems. 14:3234-3249.   10.1002/ggge.20174   AbstractWebsite

Investigations of the behavior of the geomagnetic field on geological timescales rely on globally distributed data sets from dated lava flows. We present the first suitable data from the Arctic region, comprising 37 paleomagnetic directions from Jan Mayen (71 degrees N, 0.2-461 ka) and Spitsbergen (79 degrees N, 1-9.2 Ma) and five paleointensity results. Dispersion of the Arctic virtual geomagnetic poles over the last 2 Ma (27.34.0 degrees) is significantly lower than that from published Antarctic data sets (32.15.0 degrees). Arctic average virtual axial dipole moment (76.824.3 ZAm(2)) is high in comparison to Antarctica over the same time interval (34.88.2 ZAm(2)), although the data are still too sparse in the Arctic to be definitive. These data support a long-lived hemispheric asymmetry of the magnetic field, contrasting higher, more stable fields in the north with lower average strength and more variable field directions in the south. Such features require significant non-axial-dipole contributions over 10(5)-10(6) years.

Knowles, E, Staudigel H, Templeton A.  2013.  Geochemical characterization of tubular alteration features in subseafloor basalt glass. Earth and Planetary Science Letters. 374:239-250.   10.1016/j.epsl.2013.05.012   AbstractWebsite

There are numerous indications that subseafloor basalts may currently host a huge quantity of active microbial cells and contain biosignatures of ancient life in the form of physical and chemical basalt glass alteration. Unfortunately, technological challenges prevent us from observing the formation and mineralization of these alteration features in situ, or reproducing tubular basalt alteration processes in the laboratory. Therefore, comprehensive analysis of the physical and chemical traces retained in mineralized tubules is currently the best approach for deciphering a record of glass alteration. We have used a number of high-resolution spectroscopic and microscopic methods to probe the geochemical and mineralogical characteristics of tubular alteration features in basalt glasses obtained from a suite of subseafloor drill cores that covers a range of different collection locations and ages. By combining three different synchrotron-based X-ray measurements - X-ray fluorescence microprobe mapping, XANES spectroscopy, and mu-XRD - with focused ion beam milling and transmission electron microscopy, we have spatially resolved the major and trace element distributions, as well as the oxidation state of Fe, determined the coordination chemistry of Fe, Mn and Ti at the micron-scale, and constrained the secondary minerals within these features. The tubular alteration features are characterized by strong losses of Fe2+, Mn2+, and Ca2+ compared to fresh glass, oxidation of the residual Fe, and the accumulation of Ti and Cu. The predominant phases infilling the alteration regions are Fe3+-bearing silicates dominated by 2:1 clays, with secondary Fe- and Ti-oxides, and a partially oxidized Mn-silicate phase. These geochemical patterns observed within the tubular alteration features are comparable across a diverse suite of samples formed over the past 5-100 Ma, which shows that the microscale mineralization processes are common and consistent throughout the ocean basins and throughout time. The distributions of Ti and Cu are distinct between tubular mineralization and the crack-filling minerals and thus delineate sequential stages of fluid-rock interaction. The preserved chemistry of clay and oxide mineralization in the tubular alteration then represents a common precursor state (e.g. Ti accumulation), that has not yet undergone recrystallization (e.g. titanite formation) as observed in many older, metamorphosed examples of tubular alteration. (C) 2013 Elsevier B.V. All rights reserved.

Tauxe, L, Gee JS, Steiner MB, Staudigel H.  2013.  Paleointensity results from the Jurassic: New constraints from submarine basaltic glasses of ODP Site 801C. Geochemistry, Geophysics, Geosystems.   10.1002/2013GC004704   AbstractWebsite

Tholeiite of the oldest oceanic crust was drilled during ODP Legs 129 and 185 at Hole 801C in the western Pacific. Fresh appearing submarine basaltic glass (SBG) was recovered from the tholetiites (~167 Ma; Koppers et al. [2003]) which has been shown to be nearly ideal for determining absolute paleointensity. Paleointensities of the younger, off-axis, alkalic basalts (~160 Ma; Koppers et al. [2003]), overlying the tholeiites, had been studied earlier [Tauxe, 2006]. Here we report results from the older tholeiitic (on-axis) sequence. We subjected a total of 73 specimens from 17 cooling units to absolute paleointensity experiments. Of these, 30 specimens and 6 cooling unit averages met our strictest reliability criteria, yielding an average of 11.9± 3.9 μT. The bulk of evidence suggests a paleolatitude of the site of 14°S (with an uncertainty of 10°). This translates the intensity to a value for the virtual axial dipole moment of 28 ZAm2, slightly lower than values determined from the plagio clase crystals in the three cooling units of the younger alkalic basalts over lying the tholeiites. This value is low when compared to the long-term median value of the field of 42 ZAm2. Our results and those of the published literature therefore support the contention of a low magnetic field strength in the Jurassic (average of 28 ± 14 ZAm2; N = 138 individual estimates), as initially suggested by Prévot et al. [1990]. Our interpretation of the body of available data argue for low field strengths for the entire Jurassic extending into the early Cretaceous.

Fliegel, D, Knowles E, Wirth R, Templeton A, Staudigel H, Muehlenbachs K, Furnes H.  2012.  Characterization of alteration textures in Cretaceous oceanic crust (pillow lava) from the N-Atlantic (DSDP Hole 418A) by spatially-resolved spectroscopy. Geochimica Et Cosmochimica Acta. 96:80-93.   10.1016/j.gca.2012.08.026   AbstractWebsite

The habit, mineralogy, crystallography, and Fe speciation of tubular and granular alteration textures in basaltic glass recovered from DSDP Hole 418A, which have previously been associated with biologically mediated alteration, were investigated using an integrated suite of microscopic and spectroscopic approaches in order to shine light on their formation and mineralization history. Two different analytical approaches were used: (1) micro scale investigations with conventional petrographic optical microcopy and microscale X-ray fluorescence mapping and X-ray absorption spectroscopy, and (2) nano scale analyses with FIB (focused ion beam milling) to prepare cross-sections for TEM (transmission electron microscopy), EELS (electron energy loss spectroscopy), and STXM (scanning transmission electron microscopy) analyses. The integrated data show that tubular and granular textures are similar in chemical, mineralogical and structural habit. Both granular and tubular alteration textures show a marked transition from ferrous iron in the glass matrix to ferric iron in the textures. Granular and tubular textures are filled with sheet silicates of similar chemistry, and both exhibit thin amorphous alteration rims similar to 10-20 nm wide. The alteration rims are typically depleted in Ca and Fe. Ca is enriched at the contact between the secondary mineralization and the alteration rims, whereas Fe is enriched throughout the alteration features and is mainly present as Fe-III in contrast to Fe-II in the host glass. Carbon is enriched only in a few areas, and could possibly be of organic origin but is not bound in carbonate. The mineralization of the features follows the sequence: dissolution of the glass; formation of a leached amorphous rim; mineralizing the cavities by smectide type clays and subsequently congruent growing of the texture diameter by diffusing of the elements through the alteration layer. None of the features could be linked solely to a biogenic origin and hence the biogenicity of the textures can neither be refuted nor supported by this micro-and nano-scale data set. (C) 2012 Elsevier Ltd. All rights reserved.

Edwards, KJ, Glazer BT, Rouxel OJ, Bach W, Emerson D, Davis RE, Toner BM, Chan CS, Tebo BM, Staudigel H, Moyer CL.  2011.  Ultra-diffuse hydrothermal venting supports Fe-oxidizing bacteria and massive umber deposition at 5000 m off Hawaii. ISME Journal. 5:1748-1758.   10.1038/ismej.2011.48   AbstractWebsite

A novel hydrothermal field has been discovered at the base of Loihi Seamount, Hawaii, at 5000 mbsl. Geochemical analyses demonstrate that 'FeMO Deep', while only 0.2 degrees C above ambient seawater temperature, derives from a distal, ultra-diffuse hydrothermal source. FeMO Deep is expressed as regional seafloor seepage of gelatinous iron-and silica-rich deposits, pooling between and over basalt pillows, in places over a meter thick. The system is capped by mm to cm thick hydrothermally derived iron-oxyhydroxide-and manganese-oxide-layered crusts. We use molecular analyses (16S rDNA-based) of extant communities combined with fluorescent in situ hybridizations to demonstrate that FeMO Deep deposits contain living iron-oxidizing Zetaproteobacteria related to the recently isolated strain Mariprofundus ferroxydans. Bioenergetic calculations, based on in-situ electrochemical measurements and cell counts, indicate that reactions between iron and oxygen are important in supporting chemosynthesis in the mats, which we infer forms a trophic base of the mat ecosystem. We suggest that the biogenic FeMO Deep hydrothermal deposit represents a modern analog for one class of geological iron deposits known as ` umbers' (for example, Troodos ophilolites, Cyprus) because of striking similarities in size, setting and internal structures. The ISME Journal (2011) 5, 1748-1758; doi: 10.1038/ismej.2011.48; published online 5 May 2011

Koppers, AAP, Russell JA, Roberts J, Jackson MG, Konter JG, Wright DJ, Staudigel H, Hart SR.  2011.  Age systematics of two young en echelon Samoan volcanic trails. Geochemistry Geophysics Geosystems. 12   10.1029/2010gc003438   AbstractWebsite

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 (40)Ar/(39)Ar 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 (40)Ar/(39)Ar 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 similar to 50 km apart, the VAI and MALU trends have distinct geochemical characters and independent but overlapping linear (40)Ar/(39)Ar 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.

McLoughlin, N, Staudigel H, Furnes H, Eickmann B, Ivarsson M.  2010.  Mechanisms of microtunneling in rock substrates: distinguishing endolithic biosignatures from abiotic microtunnels. Geobiology. 8:245-255.   10.1111/j.1472-4669.2010.00243.x   AbstractWebsite

Rock-dwelling, endolithic micro-organisms can create tubular microcavities (TMCs) by the dissolution of rock substrates. Microtunnels can also conceivably be formed by abiotic processes, and collectively, these structures are here termed tubular microcavities. A textural record of life in subseafloor environments is provided by biological TMCs, and it is imperative to distinguish these from abiological tunnels. To this end, the morphologies and petrographic context of tunnels formed by chemical solution, physical abrasion, and biological processes are here described. Biological TMCs in volcanic glass are restricted to sites that were connected to early fluid circulation. Their shapes, distribution, and the absence of intersections exclude an origin by chemical dissolution of pre-existing heterogeneities such as, radiation damage trails, gas-escape structures, or fluid inclusion trails. Rather their characteristics are best explained by microbial dissolution, involving perhaps, cellular extensions that provide a mechanism of localizing and directing microtunnel formation as observed in terrestrial soils. Biological TMCs are contrasted with ambient inclusion trails (AITs) found in cherts and authigenic minerals. These differ in exhibiting longitudinal striae, a constant diameter, and polygonal cross-section, sometimes with terminal inclusions. The origin(s) of AITs remain unclear but they are hypothesized to form by migration of crystalline or organic inclusions in sealed substrates, in contrast to biotic TMCs that form in open systems. We present diagnostic morphological and petrographic criteria for distinguishing these different types of TMCs. Moreover, we argue that AIT-type processes are not viable in volcanic glass because of the absence of crystalline millstones, localized chemical solution agents, and elevated fluid pressures, necessary to drive this process.

Staudigel, H, Clague DA.  2010.  The Geological History of Deep-Sea Volcanoes Biosphere, Hydrosphere, and Lithosphere Interactions. Oceanography. 23:58-71.   10.5670/oceanog.2010.62   AbstractWebsite

The geological evolution of seamounts has distinct influence on their interactions with the ocean, their hydrology, geochemical fluxes, biology, resources, and geohazards. There are six geological evolutionary stages of seamounts: (1) Small seamounts (100-1000-m height), (2) mid-sized seamounts (> 1000-m height, > 700-m eruption depth), (3) explosive seamounts (< 700-m eruption depth), (4) ocean islands, (5) extinct seamounts, and (6) subducting seamounts. Throughout their lifetimes, seamounts offer major passageways for fluid Circulation that promotes geochemical exchange between seawater and the volcanic oceanic crust, and seamounts likely host significant microbial communities. Water circulation may be promoted by hydrothermal siphons in conjunction with the underlying oceanic crust, or it may be driven by intrusions inside seamounts from Stage 2 onward. Geochemical fluxes are likely to be very large, primarily because of the very large number of Stage I seamounts. Intrusive growth of seamounts also initiates internal deformation that ultimately may trigger volcano sector collapse that likely peaks at the end of the main volcanic activity at large seamounts or islands. Explosive activity at seamounts may begin at abyssal depth, but it is most pronounced at eruption depths shallower than 700 m. Wave erosion inhibits the emergence of islands and shortens their lifespans before they Subside due to lithosphere cooling. Once volcanism ends and a seamount is Submerged, seamounts are largely unaffected by collapse or erosion. Throughout their histories, seamounts offer habitats for diverse micro- and macrobiological communities, Culminating with the formation of coral reefs in tropical latitudes. Geological hazards associated with seamounts are responsible for some of the largest natural disasters recorded in history and include major explosive eruptions and large-scale landslides that may trigger tsunamis.

Staudigel, H, Koppers AAP, Plank TA, Hanan BB.  2010.  Seamounts in the Subduction Factory. Oceanography. 23:176-181.   10.5670/oceanog.2010.69   AbstractWebsite

The "Subduction Factory" is a metaphor for the geochemical processing of subducted oceanic crust and sediment into components that are either incorporated into the volcanic arc or recycled into Earth's mantle. Seamounts may be a significant source of material to the Subduction Factory, in particular, by providing trace elements Such as K, Ba, La, Ce, U, Th, Pb, Rb, and Cs. Seamount subduction might also play a role in the global distribution of chemical mantle heterogeneities. Neither one of these effects of seamount subduction is well understood. The Izu-Bonin-Marianas (IBM) volcanic arc is a region where the potential impact of seamount subduction may be explored most effectively. There, sections of the IBM arc and many of the incoming seamounts display unusually high (206)Pb/(204)Pb ratios, which offer a particularly promising geochemical tracer that may help quantity seamount input into the Subduction Factory. Although this process remains to be explored in a quantitative manner, it is apparent that the demise of seamounts in subduction zones offers an exciting research target with important consequences for globally relevant geochemical processes.

Jackson, MG, Hart SR, Konter JG, Koppers AAP, Staudigel H, Kurz MD, Blusztajn J, Sinton JM.  2010.  Samoan hot spot track on a "hot spot highway": Implications for mantle plumes and a deep Samoan mantle source. Geochemistry Geophysics Geosystems. 11   10.1029/2010gc003232   AbstractWebsite

We report new geochemical data for submarine lavas from the Samoan region that greatly enhance the geochemical data set for volcanoes from the hot spot. Additionally, two volcanoes dredged in the northern Lau Basin, Futuna Island and Manatu seamount, are young (<5 Ma), appear to be genetically related, and may have been generated by melting a component of Samoan mantle that has been advected into the region. We also find evidence for three seamounts and one atoll along the Samoan hot spot track that are not geochemically related to Samoa. We use a plate motion model to show that three non-Samoan hot spots, currently active in the Cook-Austral Islands, provided volcanism to the Pacific Plate now in the Samoan region approximately 10-40 Ma. The four interloping volcanoes in the Samoan region exhibit geochemical affinities with the three hot spots. All three hot spots would have left a depleted, viscous, refractory keel that is coupled to the base of the Pacific lithosphere that has been "rafted" to the Samoan region. Therefore, the new data also have implications for the origin of the Samoan hot spot as its origin has been suggested to be a result of either a deep-seated mantle plume or a consequence of lithospheric cracking. Without major modification of the current "propagating lithospheric cracks" model, it is not clear how such cracks could yield melts from the refractory keel present under the Samoan lithosphere. Instead, a region of buoyantly upwelling mantle, or plume, is suggested to generate the shield stage volcanism in the Samoan region.

Fliegel, D, Wirth R, Simonetti A, Furnes H, Staudigel H, Hanski E, Muehlenbachs K.  2010.  Septate-tubular textures in 2.0-Ga pillow lavas from the Pechenga Greenstone Belt: a nano-spectroscopic approach to investigate their biogenicity. Geobiology. 8:372-390.   10.1111/j.1472-4669.2010.00252.x   AbstractWebsite

Pillow lava rims and interpillow hyaloclastites from the upper part of the Pechenga Greenstone Belt, Kola Peninsula, N-Russia contain rare tubular textures 15-20 mu m in diameter and up to several hundred mu m long in prehnite-pumpellyite to lower greenschist facies meta-volcanic glass. The textures are septate with regular compartments 5-20 mu m across and exhibit branching, stopping and no intersecting features. Synchrotron micro-energy dispersive X-ray was used to image elemental distributions; scanning transmission X-ray microscopy, Fe L-edge and C K-edge were used to identify iron and carbon speciation at interfaces between the tubular textures and the host rock. In situ U-Pb radiometric dating by LA-MC-ICP-MS (laser ablation multicollector inductively coupled plasma mass spectrometry) of titanite from pillow lavas yielded a metamorphic age of 1790 +/- 89 Ma. Focused ion-beam milling combined with transmission electron microscopy was used to analyze the textures in three dimensions. Electron diffraction showed that the textures are mineralized by orientated pumpellyite. On the margins of the tubes, an interface between mica or chlorite and the pumpellyite shows evidence of dissolution reactions where the pumpellyite is replaced by mica/chlorite. A thin poorly crystalline Fe-phase, probably precipitated out of solution, occurs at the interface between pumpellyite and mica/chlorite. This sequence of phases leads to the hypothesis that the tubes were initially hollow, compartmentalized structures in volcanic glass that were mineralized by pumpellyite during low-grade metamorphism. Later, a Fe-bearing fluid mineralized the compartments between the pumpellyite and lastly the pumpellyite was partially dissolved and replaced by chlorite during greenschist metamorphism. The most plausible origin for a septate-tubular texture is a progressive etching of the host matrix by several generations of microbes and subsequently these tubes were filled by authigenic mineral precipitates. This preserves the textures in the rock record over geological time. The micro textures reported here thus represent a pumpellyite-mineralized trace fossil that records a Paleoproterozoic sub-seafloor biosphere.

McLoughlin, N, Fliegel DJ, Furnes H, Staudigel H, Simonetti A, Zhao G, Robinson PT.  2010.  Assessing the biogenicity and syngenicity of candidate bioalteration textures in pillow lavas of the delta 2.52 Ga Wutai greenstone terrane of China. Chinese Science Bulletin. 55:188-199., Beijing, China (CHN): Science Press Springer, Beijing   10.1007/s11434-009-0448-0   AbstractWebsite

Microorganisms that inhabit sub-seafloor lavas are capable of etching volcanic glass and creating micron-sized tunnels and pits. Mineralization of these bioalteration traces ensures that these textures survive deformation and transformation of the host glass to metamorphic minerals. The fossil record of such bioalteration textures extends far beyond volcanic glass from in-situ oceanic crust to include meta-volcanic glass from ophiolites and Precambrian greenstone belts. Investigation of petrographic thin section reported here from approximately 2.52 Ga tholeiitic pillow lavas from the Wutai Group of N. China found filamentous micro-textures. Laser Raman spectroscopy confirmed that these textures are mineralized by titanite. Moreover, the Wutai micro-textures are comparable in size, morphology and distribution to bioalteration textures from Archean greenschist facies pillow lavas. In-situ U-Pb dating of the titanite by laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICP-MS) gives an age of 1.81 + or - 0.12 Ga (2sigma , n=22, (super 206) Pb/ (super 238) U weighted average). This provides a minimum age for the mineralization of these candidate bioalteration textures and corresponds to a regional metamorphic event. This also represents a minimum age estimate for the timing of bioalteration and is compatible with the existence of a Late Archean-Proterozoic sub-seafloor biosphere. Copyright 2010 Science in China Press and Springer Berlin Heidelberg and 2009 Science in China Press and Springer-Verlag GmbH

Hein, JR, Conrad TA, Staudigel H.  2010.  Seamount Mineral Deposits; A Sources of Rare Metals for High-Technology Industries. Oceanography. 23:184-184.   10.5670/oceanog.2010.70   AbstractWebsite

The near exponential growth in Earth's population and the global economy puts increasing constraints on our planet's finite supply of natural metal resources, and, consequently, there is an increasing need for new sources to supply high-tech industries. To date, effectively all of our raw-metal resources are produced at land-based sites. Except for nearshore placer deposits, the marine environment has been largely excluded from metal mining due to technological difficulties, even though it covers more than 70% of the planet. The case can be made that deep-water seabed mining is inevitable in the future, owing to the critical and strategic metal needs for human society. In this paper, we evaluate the case that seamounts offer significant potential for mining.

Orcutt, B, Bailey B, Staudigel H, Tebo BM, Edwards KJ.  2009.  An interlaboratory comparison of 16S rRNA gene-based terminal restriction fragment length polymorphism and sequencing methods for assessing microbial diversity of seafloor basalts. Environmental Microbiology. 11:1728-1735.   10.1111/j.1462-2920.2009.01899.x   AbstractWebsite

P>We present an interlaboratory comparison between full-length 16S rRNA gene sequence analysis and terminal restriction fragment length polymorphism (TRFLP) for microbial communities hosted on seafloor basaltic lavas, with the goal of evaluating how similarly these two different DNA-based methods used in two independent labs would estimate the microbial diversity of the same basalt samples. Two samples were selected for these analyses based on differences detected in the overall levels of microbial diversity between them. Richness estimators indicate that TRFLP analysis significantly underestimates the richness of the relatively high-diversity seafloor basalt microbial community: at least 50% of species from the high-diversity site are missed by TRFLP. However, both methods reveal similar dominant species from the samples, and they predict similar levels of relative diversity between the two samples. Importantly, these results suggest that DNA-extraction or PCR-related bias between the two laboratories is minimal. We conclude that TRFLP may be useful for relative comparisons of diversity between basalt samples, for identifying dominant species, and for estimating the richness and evenness of low-diversity, skewed populations of seafloor basalt microbial communities, but that TRFLP may miss a majority of species in relatively highly diverse samples.

McLoughlin, N, Furnes H, Banerjee NR, Muehlenbachs K, Staudigel H.  2009.  Ichnotaxonomy of microbial trace fossils in volcanic glass. Journal of the Geological Society. 166:159-169.   10.1144/0016-76492008-049   AbstractWebsite

Ancient microbial activity in volcanic glass creates micron-sized cavities that call be regarded as trace fossils. These are common in glassy rims of oceanic pillow lavas and volcanic breccias. Morphologically comparable mineralized traces are also found in (meta)-volcanic glasses from ophiolites and Precambrian greenstone belts. Multiple lines of evidence indicate microbial formation of these borings, although the affinity of the trace maker(s) is poorly constrained. Two broad morphological types have been previously recognized and termed 'granular' and 'tubular' bioalteration textures. Here optical microscopy and SEM observations are used to erect two new ichnogenera: Granulohyalichnus igen. nov. and Tubulohyalichnus igen. nov. Five ichnospecies are also defined: Granulohyalichnus vulgaris isp. nov., a granular species' Tubulohyalichnus simplus isp. nov, all unornamented tubular species; Tubulohyalichnus annularis isp. nov., an annulated tubular species; Tubulohyalichnus spiralis isp. nov, a helicoidal tubular species; Tubulohyalichnus stipes isp. nov., a branched tubular species. This systematic taxonomy is advanced to allow reliable comparisons to be made between new and existing reports of these microbial borings. Moreover, the adoption of a taxonomic framework will aid the development of these ichnofossils as palaeoenvironmental indicators and tracers of microbial evolution.

Lawrence, KP, Tauxe L, Staudigel H, Constable CG, Koppers A, McIntosh W, Johnson CL.  2009.  Paleomagnetic field properties at high southern latitude. Geochemistry Geophysics Geosystems. 10   10.1029/2008gc002072   AbstractWebsite

Statistical analyses of paleomagnetic data from lava flows are used to study geomagnetic field behavior on million year timescales. Previous paleomagnetic studies have lacked high-latitude measurements necessary to investigate the persistence of geomagnetic anomalies observed in the recent and historical field and replicated in some numerical geodynamo simulations. These simulations suggest that reduced convective flow inside the tangent cylinder may affect the magnetic field at high latitude, whereas lower-latitude observations are expressions of columnar/helical flow outside the tangent cylinder. This paper presents new paleointensity and paleodirectional data from 100 volcanic sites in the Erebus Volcanic Province (EVP), Antarctica, and 21 new age determinations by the (40)Ar/(39)Ar incremental heating method. The new EVP data are combined with previously published paleomagnetic and geochronological results, providing 133 sites, 91 having radioisotopic dates. Modified Thellier-Thellier paleointensity estimates are reported for 47 sites (37 have dates). Ages for the combined data set span 0.03 to 13.42 Ma. The 125 high-quality EVP directional data selected from the merged data set have a non-Fisherian distribution and a mean direction with an inclination anomaly of similar to 3 degrees, but 95% confidence limits include the prediction from a geocentric axial dipole. Virtual geomagnetic pole (VGP) dispersions for Brunhes, Matuyama, and the combined 0-5 Ma data set are consistently high compared with values from middle-to low-latitude regions regardless of the criterion used to determine transitional fields. With VGP latitude cut off at 45 degrees, the dispersion (23.9 +/-2.1 degrees) for the combined 0-5 Ma EVP data set is consistent with earlier high-latitude data and paleosecular variation (PSV) in Model G but not with some more recent statistical PSV models. Mean EVP paleointensity of 31.5 +/-2.4 mu T, derived from 41 high-quality sites, is about half the current value at McMurdo (similar to 63 mu T). The result is essentially independent of data selection criteria. High VGP dispersion and low-intensity values support the global observation of anticorrelation between directional variability and field strength. Simulations of time-varying dipole strength show that uneven temporal sampling may bias the mean EVP intensity estimate, but the possibility of persistently anomalous field behavior at high latitude cannot be excluded.