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8-2018 Data Report: IODP Expedition 366 Pore Water Trace Element (V, Mo, Rb, Cs, U, Ba, and Li) Compositions C. G. Wheat University of Alaska Fairbanks

Trevor Fournier University of Alaska Fairbanks

Claudia Paul University of Alaska Fairbanks

Catriona Menzies University of South Hampton

Roy E. Price State University of New York

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Scholar Commons Citation Wheat, C. G.; Fournier, Trevor; Paul, Claudia; Menzies, Catriona; Price, Roy E.; Ryan, Jeff; and Sissman, Olivier, "Data Report: IODP Expedition 366 Pore Water Trace Element (V, Mo, Rb, Cs, U, Ba, and Li) Compositions" (2018). School of Geosciences Faculty and Staff Publications. 1147. https://scholarcommons.usf.edu/geo_facpub/1147

This Conference Proceeding is brought to you for free and open access by the School of Geosciences at Scholar Commons. It has been accepted for inclusion in School of Geosciences Faculty and Staff ubP lications by an authorized administrator of Scholar Commons. For more information, please contact [email protected]. Authors C. G. Wheat, Trevor Fournier, Claudia Paul, Catriona Menzies, Roy E. Price, Jeff yaR n, and Olivier Sissman

This conference proceeding is available at Scholar Commons: https://scholarcommons.usf.edu/geo_facpub/1147 Fryer, P., Wheat, C.G., Williams, T., and the Expedition 366 Scientists Proceedings of the International Ocean Discovery Program Volume 366 publications.iodp.org

https://doi.org/10.14379/iodp.proc.366.201.2018 Contents Data report: IODP Expedition 366 pore water 1 Abstract 1 Introduction trace element (V, Mo, Rb, Cs, U, Ba, and Li) 2 Methods 1 3 Results compositions 7 Acknowledgments 7 References C. Geoffrey Wheat,2 Trevor Fournier,2 Claudia Paul,2 Catriona Menzies,3 Roy E. Price,4 Jeffrey Ryan,5 and Olivier Sissman6

Keywords: International Ocean Discovery Program, IODP, JOIDES Resolution, Expedition 366, Site U1491, Site U1492, Site U1493, Site U1494, Site U1495, Site U1496, Site U1497, Site U1498, Mariana Convergent Margin, , , pore water trace elements

Abstract analyzed to assess potential biogenic and diagenetic reactions as the serpentinite material weathers and exchanges with bottom seawater International Ocean Discovery Program (IODP) Expedition 366 via diffusion. Results were generally consistent with earlier coring focused, in part, on the study of geochemical cycling, matrix alter- and drilling operations, resulting in systematic changes in the com- ation and transport, and deep biosphere processes in the Mariana position of the deep-sourced fluid with distance from the trench. zone. This research was accomplished by sampling the summit and flank regions of three active serpentinite mud volca- Introduction noes in the Mariana forearc: Yinazao (Blue Moon), Fantangisña (Ce- lestial), and Asùt Tesoro (Big Blue) . These mud One goal of International Ocean Discovery Program (IODP) Ex- volcanoes represent a transect with increasing distance from the pedition 366 was to elucidate geochemical cycling within the sub- trench. Because these mud volcanoes discharge fluids and materials duction channel of the Mariana forearc system (see the Expedition from the subduction channel, they provide a means to characterize 366 summary chapter [Fryer et al., 2018b]). Expedition 366 suc- thermal, geochemical, and pressure conditions within the seismo- cessfully cored the flank and summit regions of three Mariana genic zone. Previous coring on Ocean Drilling Program (ODP) Legs forearc serpentinite mud volcanoes that are located along a transect 125 and 195 at two other serpentinite mud volcanoes (Conical and with increasing distance from the trench and by inference with South Chamorro Seamounts, respectively) and piston, gravity, and depth to the subducted Pacific plate (Figure F1). Previous scientific push cores from several other Mariana serpentinite mud volcanoes drilling during Ocean Drilling Program (ODP) Legs 125 and 195 at add to this transect of deep-sourced material that is discharged at two other Mariana serpentinite mud volcanoes, Conical and South the seafloor. Chamorro Seamounts, respectively, as well as piston, gravity, and Pore waters were squeezed from cored serpentinite materials to push cores from several other Mariana serpentinite mud volcanoes determine the composition of deep-sourced fluid from the sub- add additional geochemical data to this transect of active ser- duction channel and to assess the character, extent, and effect of pentinite mud volcanoes in the Mariana forearc (Fryer, Pearce, diagenetic reactions and mixing with seawater on the flanks of three Stokking, et al., 1990; Salisbury, Shinohara, Richter, et al., 2002; serpentinite seamounts (Yinazao, Fantangisña, and Asùt Tesoro). In Mottl et al., 2004; Hulme et al., 2010). addition, two water-sampling temperature probe (WSTP) fluid One of the expedition’s primary objectives was to determine the samples were collected in two of the cased boreholes, each with at composition of deep-sourced fluid to characterize thermal, geo- least 30 m of screened casing that allowed formation fluids to dis- chemical, and pressure conditions within the subduction channel by charge into the borehole. Here we report shore-based Li, Rb, Cs, Ba, sampling the summit region where newly deposited material is cur- V, Mo, and U measurements of pore waters and one of the WSTP rently being delivered. A second primary objective was to assess the samples. The alkali metals were analyzed to constrain the tempera- character, extent, and effect of diagenetic reactions and mixing with ture of reaction in the subduction channel. The other elements were seawater on the flanks of three serpentinite mud volcanoes, thus

1 Wheat, C.G., Fournier, T., Paul, C., Menzies, C., Price, R.E., Ryan, J., and Sissman, O., 2018. Data report: IODP Expedition 366 pore water trace element (V, Mo, Rb, Cs, U, Ba, and Li) com- positions. In Fryer, P., Wheat, C.G., Williams, T., and the Expedition 366 Scientists, Mariana Convergent Margin and South Chamorro . Proceedings of the International Ocean Discovery Program, 366: College Station, TX (International Ocean Discovery Program). https://doi.org/10.14379/iodp.proc.366.201.2018 2 Global Undersea Research Unit, College of Fisheries and Ocean Sciences, University of Alaska Fairbanks, USA. Correspondence author: [email protected] 3 Ocean and Earth Science National Oceanography Centre, University of Southampton, United Kingdom. 4 School of Marine and Atmospheric Sciences, State University of New York, USA. 5 School of Geosciences, University of South Florida, USA. 6 IFP énergies nouvelles, France. MS 366-201: Received 20 March 2018 · Accepted 31 May 2018 · Published 13 August 2018 This work is distributed under the Creative Commons Attribution 4.0 International (CC BY 4.0) license. C.G. Wheat et al. Data report: pore water trace element compositions

Figure F1. Locations of IODP Expedition 366 Sites U1491–U1498 and Site We also recovered material with extended core barrel (XCB) and ro- 1200 on South Chamorro Seamount superimposed on a regional bathy- tary core barrel (RCB) coring. Recovered materials included ser- metric map. (From the Expedition 366 summary chapter [Fryer et al., pentinite mudflows with clasts from the flanks of each of three 2018b].) edifices and pelagic sediment: Sites U1491 (Yinazao [Blue Moon] 19° Seamount), U1493, U1494, U1495 (Asùt Tesoro [Big Blue] Sea-

0 0 0 -3000 0 0 -600 0 000 3 0 - 2 0 - -1 -3 N 000 -6 mount), and U1498 (Fantangisña [Celestial] Seamount) (Figure F1).

0 -50 00 00 0 -4000 -400 -4 0 0 -5 0 -4 0 00 0 00 0 The serpentinite mudflow matrix differed in color with depth and, 0 -3 0 -400 -3000 0 0 00 0 -4000 -3

0 100 km

-4 - 3 U1496 0 although distinctly disturbed by flow-in during HLAPC and XCB 00 U1495

- 00 0 4 0

00 2000 0 0 - 0 -20 -1 0 0 000 -7 -4 AsùtAsù0 t TesoruTesoru 000 coring, discrete horizons of clast content and matrix constituents -6 0 -2000 -40 00 0 4 0 18° - 0 Mariana 0 U1494 SeamountSeamount remained in place. Serpentinite material also was recovered from -3000 Trench

0

0 -10000 U1493 20 - 0 0 the summit regions of each of the three cored mud volcanoes: Sites 0 0 0 0 -4 0 0 0 0 4 0 -4 - 0-5000 -6 0 00 00 00 -30 000 -3 0 -1 0 -3 -4 U1492 (Yinazao Seamount), U1496 (Asùt Tesoro Seamount), and 0 0

0 -8000 0 -200

0 0 0 -2 7 000 0 - U1497 (Fantangisña Seamount). 0 0 4 00 - 0 17° -40 0 0 -4000 -1 Serpentinite material and sediment for pore water analysis were 0 00 100 -20 0 - 0 0 0 0 -4 -1

0

0 -4 -400 0 U1497 0 0 immediately taken from the catwalk and placed in a refrigerator to 00 0

0

3 -

- 0 5 U1498 0 00 1 FantangisñaFantangisña 0 - 0

0 0 cool samples to near (2°–5°C) the in situ temperature (see the Expe-

0

0 400 0 - - 0 0 5 0 00 -4 SeamountSeamount -4 0

0 00 0 dition 366 methods chapter [Fryer et al., 2018a]). Serpentinite and -10

-30 0

0 - -2000 3 00 000 16° 1 - YinazaoYinazao - 0 40 sediment samples were then extracted from the core liner in a nitro- U1491 0 0 0 4 0 00 - 40 SeamountSeamount - 0 0 0 0 -2 gen-filled glove bag, scraped to remove the outer contaminated

-5 0 U1492 0 0

- 6 000 -20 rind, and placed into a titanium squeezer. The squeezer was re- 0 -3 0 0 000 00 -4000 -4 - 80 0 0 0 0 0 0 0 4 0 - -2000 0 4 moved from the glove bag and inserted into the press. Pore waters - 0 - 4 0 0 0 -500 0 0 -10 0 0 0 0

1 - - 0 3

- 0 4 15° 0 0 00 0 0 were expelled, filtered, aliquoted, preserved, and stored for a range 0 0 0 8 - h c 00 0 0 of shore-based analyses. A total of 149 pore water samples and 2 40 0 n - 6 0 00 300 -2000 - -4000 - e 0 -3 -4 r 00 0 -4000 TrenchT WSTP samples were collected during Expedition 366. Unfortu-

a 0 0 0 0 -100 0 0 00 0 0 0 0 4 nna - 40 - -90 50 - -30 ia nately, not all of the whole-round samples provided sufficient fluids 00 0 Depth (m) 0 4 r - 00 40 a -6000 -

00 0 14° MariaM 0 for shore-based analyses for each solute or isotope. Only the WSTP 0

2 00 00 - 7 0 - 9 0 - 0 -4 0 1200 00 -300 0 00 -80 0 sample from Hole U1496C is included in this data set. 0 0 0 -4 1 00 - -9 -5 -2 0 0 0 0 0 0 0 0 SouthSouth ChamorroChamorro 0 0

-3 4 00 - 5 -500 -8000 0 0 - 0 Analyses presented herein were conducted using the identical 0 0 SeamountSeamount 0 0 0 0 0

- 6

3 0 - -6000 9 - 0 GuamGuam - 000 3

0 0 0 -5 0 inductively coupled plasma–mass spectrometry (ICP-MS) and in- 0 0 00 -4000 0 0 3 0 - 00 4 0 - 00 00 -3000 -9 0 0 0 -4 -1 0 6000 0 13° - -70 ductively coupled plasma–optical emission spectrometry (ICP- 145°E 146° 147° 148° OES) methods that Mottl et al. (2004) and Hulme et al. (2010) used, thus ensuring continuity among data sets. Trace elements (V, Mo, providing constraints for the extent of continued serpentinite reac- Rb, Cs, U, and Ba) were analyzed on 103 samples using an ICP-MS tions and potential microbial metabolic activity. To meet these two with a 1:50 dilution in 3% ultra-pure nitric acid and standard ma- objectives, 149 whole-round samples were collected for pore water chine settings (Table T1). Standards were matrix matched with bot- extraction. Extracted pore waters were analyzed shipboard, ali- tom seawater from the eastern flank of the Juan de Fuca Ridge quoted into a range of containers, and preserved for shore-based (Wheat et al., 2010). This seawater and a blank were analyzed about analyses (see the Expedition 366 summary chapter [Fryer et al., every 8 to 10 samples to account for machine drift. The average con- 2018b]). In addition, two fluid samples were collected using the wa- centration of this bottom seawater and the standard deviation are ter-sampling temperature probe (WSTP) within two cased bore- listed in Table T1. holes, each with screened casing that allows formation fluids to flow The lack of sensitivity in the Li measurements at sea led us to into the borehole while retaining the mud matrix (e.g., ODP Hole analyze 127 samples on an ICP-OES with a 1:25 dilution in 3% ultra- 1200C; Wheat et al., 2008). pure nitric acid utilizing standard axial machine settings (Table T1). Although pore waters were analyzed for many dissolved ions Concurrent with this measurement, we also measured B, Ba, Mn, and gases at sea, shipboard instrumentation limits some critical Fe, Si, and Sr, and we measured Ca, Mg, K, Na, and S on a separate analyses. This paper remedies this limitation by presenting results aliquot with a 1:100 dilution. These analyses were conducted to from analyses of trace elements, particularly Rb and Cs. These two confirm that shipboard results were consistent with results that elements constrained the temperature of the deep-sourced fluid, were generated during prior work (e.g., Mottl et al., 2004; Hulme et given their similar chemistries but different mobilization character- al., 2010). As expected, results from these shore-based analyses and istics (e.g., Hulme et al., 2010). Lithium concentration data, another shipboard results agree within analytical precision. Duplicate shore- alkali metal, also is presented because many samples have concen- based results are not presented because the entire data set was not trations that were below the detection limit afforded by the ship- analyzed and the IODP database already includes measured values. board instrument. Other trace elements (V, Mo, Ba, and U) were Deep-sourced fluid compositions for the three seamounts that measured and are presented to provide a gauge for potential reac- were drilled during Expedition 366 were calculated based on pore tions and diagenetic pathways on the flanks of the seamount. water data from the summit boreholes for which the fluid composi- tion reaches an asymptotic composition with depth. Such profiles Methods are consistent with deep-sourced fluids that upwell faster than the surrounding serpentinite matrix (e.g., Fryer, Pearce, Stokking, et al., Coring with the half-length advanced piston corer (HLAPC) 1999; Mottl et al., 2003, 2004; Hulme et al., 2010). Concentrations was the primary method used to acquire material during Expedition calculated for the deep-sourced fluid for Yinazao Seamount were 366 (see the Expedition 366 methods chapter [Fryer et al., 2018a]). generally based on the average concentration of pore waters from

IODP Proceedings 2Volume 366 C.G. Wheat et al. Data report: pore water trace element compositions

Table T1. Pore water chemical data arranged by distance from the trench. Download table in CSV format.

Table T2. Summary of deep-sourced fluids. * = Expedition 366 data are the average of deeper samples at the summit sites, as described in the text. Other data are from Hulme et al., 2010. Download table in CSV format.

Serpentinite Distance to Alkalinity Mg Ca Sr Sulfate Ba B Li Na seamount trench (km) pH (mmol/kg) (mmol/kg) (mmol/kg) (μmol/kg) (mmol/kg) (μmol/kg) (μmol/kg) (μmol/kg) (mmol/kg)

Bottom seawater 0 8.1 2.3 52.4 10.2 90 28 0.140 410 26 466 Yinazao (Blue Moon)* 55 10.7 1.4 0.9 58 750 23.9 0.22 0.2 4.7 361 Cerulean Springs 60 10.8 2.3 0 49.5 320 8.5 0.297 15 2.1 220 East Quaker 61 10.7 3.1 0.2 74.8 6.9 360 Fantangisña (Celestial)* 62 ~10.8 <0.5 <2 >82 >630 <8 ~0.8 <1 ~12 ~400 NE Quaker 63 >8.3 <1.3 20 >33 <23 <420 Pacman 70 >8.9 <1.0 44 <6.9 <56 <25 <0.118 <387 >30.3 464 Quaker 76 9.2 0.8 0.5 18.1 205 23 0.125 830 119 461 Baby Blue 72 >9.0 <1.0 40 <6.9 <61 <22 0.216 >31 >489 Asùt Tesoro (Big Blue)* 72 12.5 73 0.8 0.1 13 30 0.07 1,070 4 640 South Chamorro 78 12.5 62 0 0.3 10 28 0.40 3,000 0.4 610 Conical 86 12.5 52 0.1 1 20 46 0.10 3,900 1.6 390

Serpentinite Distance to K Rb Cs V Mo U Phosphate Ammonium seamount trench (km) (mmol/kg) (μmol/kg) (nmol/kg) (nmol/kg) (nmol/kg) (nmol/kg) (μmol/kg) (μmol/kg)

Bottom seawater 0 10.1 1.37 2.2 38.4 100 13.5 Yinazao (Blue Moon)* 55 0.9 0.29 3.6 16 10 0.08 2 95 Cerulean Springs 60 2.2 0.45 5.6 25.1 20 0.31 East Quaker 61 3.7 0.8 198 Fantangisña (Celestial)* 62 <6 <1 ~7.7 ~15 ~4 0.1 <0.5 ~3 NE Quaker 63 <7.64 40.7 50 Pacman 70 10.1 >1.4 >9.1 <0.28 Quaker 76 9.39 1.57 96 80.3 36 0.01 Baby Blue 72 10.5 >1.69 >10.3 5.4 198 <0.54 Asùt Tesoro (Big Blue)* 72 13 6.6 160 100 104 0.3 3 180 South Chamorro 78 19 10 53.5 16.3 24 <0.1 Conical 86 15 7.8 >61.6 113 42 0 depths greater than 8 meters below seafloor (mbsf) in Hole data from Hole U1496B do not show an asymptote with depth, only U1492C, with the exception of Section 366-U1492C-16F-1 (Table data from Hole U1496B were used to estimate the deep-sourced T2). The trace element concentration-depth profiles were signifi- fluid concentration for this element. cantly influenced by diagenetic reactions near the seafloor; thus, the deep-sourced fluid composition was calculated based on the aver- Results age concentration of samples deeper than 17 mbsf (V, Rb, and Cs), 31 mbsf (Cs), and 77 mbsf (Mo, Ba, and alkalinity). Concentration-depth profiles The composition of the deep-sourced fluid that upwells near the Concentration-depth profiles for Li, Rb, and Cs and for V, Mo, summit of Fantangisña Seamount was estimated from pore water U, and Ba are presented in Figures F2 and F3, respectively. These samples collected from Holes U1497A and U1497B (Table T2). Un- profiles highlight differences in composition among the three ser- fortunately, there was no clearly defined asymptotic composition pentinite seamounts. In general, fluids from summit sites show a with depth, which is an indication that seepage is slower here than trend from lower Rb, B, and Cs concentrations in fluids from at the other summit sites, allowing diagenetic reactions to dominate Yinazao Seamount to Fantangisña Seamount and Asùt Tesoro Sea- trace element depth profiles. Thus, concentrations of dissolved ions mount (i.e., from the shallowest to the deeper source fluids). Chem- in the deep-sourced fluid are generally reported as minimum or ical compositions of upwelling fluids from summit sites are maximum values for Fantangisña Seamount. generally similar for Li and U. Trends for the more reactive elements Concentration-depth profiles reach an asymptote in samples V and Mo are less defined but are similar at Yinazao and Fan- from Holes U1496A and U1496B (Asùt Tesoro Seamount). Data tangisña Seamounts and generally greater at Asùt Tesoro Sea- from Hole U1496C were not used in this analysis because these mount. Ba trends generally match the inverse in the sulfate data, samples were collected using RCB drilling, which resulted in less which show a range in values from a low at Fantangisña Seamount than ideal cores from which pore waters were extracted. Deep- to a high at Asùt Tesoro Seamount (Figure F4). sourced fluids were calculated from averages of samples that were In addition, there are some general differences in concentration- deeper than 5 mbsf (Hole U1496A) and 3 mbsf (Hole U1496B), with depth profiles between summit and flank sites for a given ser- the exception of Sections 366-U1496A-8F-3, 366-U1496A-9F-1, pentinite mud volcano. In general, flank sites have higher Li concen- and 366-U1496B-7F-1; each of these three samples was contami- trations, consistent with diffusive exchanges of Li in bottom nated with drilling fluid (seawater). Similarly, the WSTP sample seawater. Likewise, Rb concentrations at flank sites are generally from Hole U1496C was contaminated with seawater. Because Mo more similar to bottom seawater than concentrations in deep-

IODP Proceedings 3Volume 366 C.G. Wheat et al. Data report: pore water trace element compositions

Figure F2. Pore water concentration depth profiles for Li, Rb, and Cs from Yinazao, Fantangisña, and Asùt Tesoro Seamounts. Solid symbols = summit data (Holes U1492C, U1497A, and U1496A), open symbols = data from the other summit and flank holes, black solid symbol = bottom seawater.

Lithium (µmol/kg) Rubidium (µmol/kg) Cesium (nmol/kg) 010203040024680 50 100 150 200 250 0 0 0

Asùt Tesoro 50 50 Asùt Tesoro 50 Asùt Tesoro

100 100 100

Depth (mbsf) Yinazao Yinazao Yinazao

150 Fantangisña 150 150 Fantangisña Fantangisña

200 200 200

Figure F3. Pore water concentration depth profiles for V, Mo, U, and Ba from Yinazao, Fantangisña, and Asùt Tesoro Seamounts. Solid symbols = summit data (Holes U1492C, U1497A, and U1496A), open symbols = data from the other summit and flank holes, black solid symbol = bottom seawater.

Vanadium (nmol/kg) Molybdenum (nmol/kg) 0 50 100 150 200 250 0 50 100 150 200 250 0 0

Asùt Tesoro 50 Asùt Tesoro 50

Yinazao Yinazao

100 100 Depth (mbsf)

150 150 Fantangisña Fantangisña

200 200

Barium (µmol/kg) Uranium (nmol/kg) 0 0.25 0.5 0.75 1 03691215 0 0

Yinazao Asùt Tesoro Asùt Tesoro 50 50

Yinazao 100 100 Depth (mbsf)

150 Fantangisña 150 Fantangisña

200 200

IODP Proceedings 4Volume 366 C.G. Wheat et al. Data report: pore water trace element compositions

Figure F4. Pore water concentration of sulfate plotted versus Ba from waters from the flanks of the seamounts have Ba concentrations Yinazao, Fantangisña, and Asùt Tesoro Seamounts. Solid symbols = summit that mirror the sulfate concentrations but without a clear distinc- data (Holes U1492C, U1497A, and U1496A), open symbols = data from the tion between flank and summit concentrations. Plots of Mo or V other summit and flank holes, black solid symbol = bottom seawater. concentrations versus Ba concentrations (not shown) show two dis- 2 tinct groupings, similar to sulfate (Figure F4). One grouping is high in Mo or V and low in Ba, and the other is high in Ba and low in Mo or V, consistent with different modes of production and removal of these elements (e.g., Crusius et al., 1996; Morford et al., 2005; Mc- Manus et al., 1998). 1.5 Trends in deep-sourced fluids The distance between the Mariana serpentinite mud volcanoes and the trench is a proxy for the depth to the subduction channel (Mottl et al., 2004; Hulme et al., 2010). In general, the greater this Fantangisña distance, the deeper the source for the upwelling pore fluids and the 1 warmer the temperature in the subduction channel. The range of temperatures below these serpentinite mud volcanoes spans 80°– Barium (µmol/kg) 350°C, affecting the type and rate of reactions that occur at depth Asùt Tesoro (Hulme et al., 2010). Thus, one anticipates changes in the fluid com- position as a function of distance from the trench. For example, two 0.5 Yinazao noteworthy changes are observed in the Ca and alkalinity data. Close to the trench, Ca concentrations are higher than seawater val- ues and the alkalinity is well below the seawater value (Table T2). In contrast, Ca concentrations farther from the trench are below the seawater value and alkalinity values are high. These values are a re- 0 sult of the temperature dependence of the decarbonization process 0 5 10 15 20 25 30 35 within the subduction channel (Fryer, Pearce, Stokking, et al., 1999). Sulfate (mmol/kg) Likewise, trends are observed in the trace element data. In general, Rb and Cs concentrations increase in the estimated sourced fluids. Similarly, Cs concentrations at flank sites on Yinazao deep-sourced fluids as a function of distance from the trench, con- Seamount are more seawater-like than the sourced fluids; however, sistent with expectation of seawater-basalt reactions in the sub- flank fluids from Fantangisña Seamount are much higher in Cs than duction channel at increasing temperature (Figure F5A) (You et al., either bottom seawater or the upwelling fluid from the summit. 1996; Sadofsky and Bebout, 2003). In contrast, concentrations of Ba Also, Cs concentrations from the flanks of Yinazao Seamount are may decrease with distance from the trench, inverse to the sulfate nearly identical to their deep-sourced counterparts; both are ~1 trend (Figure F5B). However, trends of deep-sourced fluid concen- nmol/kg different from seawater. Some flank fluids from the upper trations with distance from the trench were not observed with the 20 mbsf have higher U concentrations than the deep-sourced fluid other trace element data (Li, V, and Mo), and each of the deep- but generally merge with the low concentrations of the deep- sourced fluids has U concentrations that approach the limit of de- sourced fluid, indicative of ongoing removal of seawater U that is tection. Other trends were identified in concentration-concentra- diffusively transported into the serpentinite matrix. Concentrations tion plots of various elements (Figure F6). Some of these trends of Mo in the upper 20 mbsf are generally higher than their deep- (e.g., K versus Rb) likely reflect changes in the temperature of reac- sourced counterparts, consistent with diagenetic or microbial me- tion, whereas others (e.g., Ba versus V) likely reflect redox condi- diated reactions within this depth zone. Similar diagenetic influ- tions. Combined, these trends provide a conceptual illustration of ences are evident in the V data from Asùt Tesoro Seamount, but a subsurface processes and their surface expression (Figure F7). clear delineation is not evident at the other two seamounts. Pore

IODP Proceedings 5Volume 366 C.G. Wheat et al. Data report: pore water trace element compositions

Figure F5. Concentrations of deep-sourced fluids as a function of distance to the trench. A. Trends in Rb (green circles) and Cs (red squares) are similar, showing increased concentrations with distance and by supposition depth to the subduction channel and temperature within the subduction channel. B. Trends in sulfate (green circles) and Ba (red squares) show an inverse relationship. A 12 200

10 Cesium Rubidium 150 8

6 100

4 Cesium (nmol/kg)

Rubidium (µmol/kg) 50 2

0 0 50 55 60 65 70 75 80 85 90 Distance to trench (km) B 50 1

Sulfate 40 0.8

30 0.6

20 0.4 Sulfate (mmol/kg) Barium Barium (µmol/kg) 10 0.2

0 0 50 55 60 65 70 75 80 85 90 Distance to trench (km)

Figure F6. Concentrations of K versus Rb and Ba versus V in deep-sourced fluids. The K-Rb trend is likely due to changes in reactions with increased tempera- ture, and the Ba-V trend is likely redox related.

12 120

10 100 Asùt Tesoro

8 80

Asùt Tesoro 6 60

Seawater Yinazao 40

Rubidium (µmol/kg) 4 Vanadium (nmol/kg)

Fantangisña Yinazao Fantangisña 2 20

Seawater 0 0 0 5 10 15 20 0 0.2 0.4 0.6 0.8 Potassium (mmol/kg) Barium (µmol/kg)

IODP Proceedings 6Volume 366 C.G. Wheat et al. Data report: pore water trace element compositions

Figure F7. Pore water chemical data derived from the Mariana forearc during Expedition 366, data from this report, and data from two other serpentinite mud volcanoes at a greater distance from the trench (South Chamorro and Conical Seamounts) (Hulme et al., 2010). Bar graphs illustrate relative differences in concentrations among sites to highlight these differences. Depths are conceptual and for illustrative purposes only. (See the Expedition 366 summary chapter [Fryer et al., 2018b].)

Distance from trench axis (km) 75 0

South Conical Chamorro Asùt Tesoru Fantangisña Yinazao pH = 12.5 pH = 12.5 pH = 12.5 pH = 11.0 pH = 11.2 Dip-slip motion Horizontal motion (toward) Horizontal motion (away) Serpentine mud volcano BCaNa K B Ca Na K BCaNa K BCaNaK BCaNaK Conduit of mud volcano Greenschist pod Blueschist pod K CO2– SO2– B 0 3 4 Ca Sr B Li Ca Sr Cs Ce Rb Cs Mn Fe Co Rb Cs Ba Bruciteite Pacific plate Trench Na/Cl Gd/Tb Carbonate Na/Cl Gd/Tb chimneysneys seamount chimneyss Forearc axis sediment Horst 5 Horst block block

Graben Prehnite-Pumpellyite 10 Forearc mantle <80°C

Carbonate dissolution; (km) Depth Greenschist sediment compaction, 15 serpentine + brucite; H2 200°C–80°C

Clay diagenesis and Décollement desorbed water release 20 n

<300°CClay decomposition and fluid freshening - 25 Blueschist lawsonite-albite/ Direction of lawsonite blueschist subduction

Acknowledgments methods. In Fryer, P., Wheat, C.G., Williams, T., and the Expedition 366 Scientists, Mariana Convergent Margin and South Chamorro Seamount. This research used samples provided by the International Ocean Proceedings of the International Ocean Discovery Program, 366: College Discovery Program (IODP). IODP is sponsored by the U.S. National Station, TX (International Ocean Discovery Program). Science Foundation (NSF) and participating countries. Financial https://doi.org/10.14379/iodp.proc.366.102.2018 support was provided by the U.S. Science Support Program Fryer, P., Wheat, C.G., Williams, T., Albers, E., Bekins, B., Debret, B.P.R., Deng, J., Dong, Y., Eickenbusch, P., Frery, E.A., Ichiyama, Y., Johnson, K., (USSSP) for this shore-based analysis. We thank Marta Torres for Johnston, R.M., Kevorkian, R.T., Kurz, W., Magalhaes, V., Mantovanelli, providing a review that improved this publication. This is C-DEBI S.S., Menapace, W., Menzies, C.D., Michibayashi, K., Moyer, C.L., Mul- contribution 429. lane, K.K., Park, J.-W., Price, R.E., Ryan, J.G., Shervais, J.W., Sissmann, O.J., Suzuki, S., Takai, K., Walter, B., and Zhang, R., 2018b. Expedition 366 References summary. In Fryer, P., Wheat, C.G., Williams, T., and the Expedition 366 Scientists, Mariana Convergent Margin and South Chamorro Seamount. Crusius, J., Calvert, S., Pedersen, T., and Sage, D., 1996. Rhenium and molyb- Proceedings of the International Ocean Discovery Program, 366: College denium enrichments in sediments as indicators of oxic, suboxic and sul- Station, TX (International Ocean Discovery Program). fidic conditions of deposition. Earth and Planetary Science Letters, https://doi.org/10.14379/iodp.proc.366.101.2018 145(1–4):65–78. https://doi.org/10.1016/S0012-821X(96)00204-X Hulme, S.M., Wheat, C.G., Fryer, P., and Mottl, M.J., 2010. Pore water chemis- Fryer, P., Pearce, J.A., Stokking, L.B., et al., 1990. Proceedings of the Ocean try of the Mariana serpentinite mud volcanoes: a window to the seismo- Drilling Program, Initial Reports, 125: College Station, TX (Ocean Drill- genic zone. Geochemistry, Geophysics, Geosystems, 11(1):Q01X09. ing Program). https://doi.org/10.2973/odp.proc.ir.125.1990 https://doi.org/10.1029/2009GC002674 Fryer, P., Wheat, C.G., and Mottl, M.J., 1999. Mariana blueschist mud volca- McManus, J., Berelson, W.M., Klinkhammer, G.P., Johnson, K.S., Coale, K.H., nism: implications for conditions within the subduction zone. Geology, Anderson, R.F., Kumar, N., Burdige, D.J., Hammond, D.E., Brumsack, H.J., 27(2):103–106. https://doi.org/10.1130/0091- McCorkle, D.C., and Rushdi, A., 1998. Geochemistry of barium in marine 7613(1999)027<0103:MBMVIF>2.3.CO;2 sediments: implications for its use as a paleoproxy. Geochimica et Cosmo- Fryer, P., Wheat, C.G., Williams, T., Albers, E., Bekins, B., Debret, B.P.R., chimica Acta, 62(21–22):3453–3473. Deng, J., Dong, Y., Eickenbusch, P., Frery, E.A., Ichiyama, Y., Johnson, K., https://doi.org/10.1016/S0016-7037(98)00248-8 Johnston, R.M., Kevorkian, R.T., Kurz, W., Magalhaes, V., Mantovanelli, Morford, J.L., Emerson, S.R., Breckel, E.J., and Kim, S.H., 2005. Diagenesis of S.S., Menapace, W., Menzies, C.D., Michibayashi, K., Moyer, C.L., Mul- oxyanions (V, U, Re, and Mo) in pore waters and sediments from a conti- lane, K.K., Park, J.-W., Price, R.E., Ryan, J.G., Shervais, J.W., Sissmann, nental margin. Geochimica et Cosmochimica Acta, 69(21):5021–5032. O.J., Suzuki, S., Takai, K., Walter, B., and Zhang, R., 2018a. Expedition 366 https://doi.org/10.1016/j.gca.2005.05.015

IODP Proceedings 7Volume 366 C.G. Wheat et al. Data report: pore water trace element compositions

Mottl, M.J., Komor, S.C., Fryer, P., and Moyer, C.L., 2003. Deep-slab fluids fuel Wheat, C.G., Fryer, P., Fisher, A.T., Hulme, S., Jannasch, H., Mottl, M.J., and extremophilic Archaea on a Mariana forearc serpentinite mud volcano: Becker, K., 2008. Borehole observations of fluid flow from South Ocean Drilling Program Leg 195. Geochemistry, Geophysics, Geosystems, Chamorro Seamount, an active serpentinite mud volcano in the Mariana 4:9009. https://doi.org/10.1029/2003GC000588 forearc. Earth and Planetary Science Letters, 267(3–4):401–409. Mottl, M.J., Wheat, C.G., Fryer, P., Gharib, J., and Martin, J.B., 2004. Chemis- https://doi.org/10.1016/j.epsl.2007.11.057 try of springs across the Mariana forearc shows progressive devolatiliza- Wheat, C.G., Jannasch, H.W., Fisher, A.T., Becker, K., Sharkey, J., and Hulme, tion of the subducting plate. Geochimica et Cosmochimica Acta, S., 2010. Subseafloor seawater-basalt-microbe reactions: continuous sam- 68(23):4915–4933. https://doi.org/10.1016/j.gca.2004.05.037 pling of borehole fluids in a ridge flank environment. Geochemistry, Geo- Sadofsky, S.J., and Bebout, G.E., 2003. Record of forearc devolatilization in physics, Geosystems, 11(7):Q07011. low-T, high-P/T metasedimentary suites: significance for models of con- https://doi.org/10.1029/2010GC003057 vergent margin chemical cycling. Geochemistry, Geophysics, Geosystems, You, C.-F., Castillo, P.R., Gieskes, J.M., Chan, L.H., and Spivack, A.J., 1996. 4(4):9003–9031. https://doi.org/10.1029/2002GC000412 Trace element behavior in hydrothermal experiments: implications for Salisbury, M.H., Shinohara, M., Richter, C., et al., 2002. Proceedings of the fluid processes at shallow depth in subduction zones. Earth and Plane- Ocean Drilling Program, Initial Reports, 195: College Station, TX (Ocean tary Science Letters, 140(1–4):41–52. Drilling Program). https://doi.org/10.2973/odp.proc.ir.195.2002 https://doi.org/10.1016/0012-821X(96)00049-0

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