V35 Submarine Volcanic Eruptions: Studies of Geological, Chemical, and Biological Processes Submarine Eruptions in the NE Lau Basin W. Mata Actively Erupting NE Lau Spreading center Erupted within the year

Resing et al., /5.4 nr * 3 (%) ) 3 He # fM R/R A ) CO 2 (uM) CO 2 : 3 H e X10 9 ) CO 2 : ) pH CO 2 /S % alkalinit y Seamount X " 0.4 ns 28 " 2 $ --- NW Rota " " Esmeralda " " 1657 " % Ruby " " 6856 " % E Diamante80.2NR19NR 561 " 50 30% Maug " 0.2 * " 1668 " % Daikoku230.7NR16NR 326 " NW Eifuku " " 1368 " 17 No S- Kasuga 2 Shallow " " 1333 " 12 7 Deep " # 14 " 4333 " 31 No S Nikko " " 2261 " 34 2 Background

Figure 2A. Bathymetric Maps of hydrothermally active volcanoes and vertical profiles of chemical anomalies above them. Tows are indicated by black lines on the maps with green and red circles indicating the starting and ending points of the tows respectively. Locations of vertical casts are indicated by yellow filled symbols. Note that scales are different for each volcano. Particulate aluminum and sulfur are designated by pAl and pS respectively. pS = Elemental sulfur (pS El ) +Non volatile sulfur (pS NV ). Total Dissolvable Fe and Mn (TDFe and TDMn) are the total amount of Fe and Mn in an unfiltered acidified samples, while Dissolved Fe and Mn (DFe and DMn) are the amount of Fe and Mn in a filtered acidified sample.  pH and  CO 2 are the changes in pH and CO 2 from the regional background respectively.

Figure 3. Low level venting as identified by helium isotopic data. The solid line represents the background the * 3 He along the arc, however it is based on a single location at ~18 O N in the study area (see Figure 1). Although this background is not fully representative of the background at different particular sites within the study area, its overall shape is. During individual casts, the * 3 He levels above and below the plumes are more representative of local background. Of the four casts taken around the summit of Ahyi Volcano, a single sample showed anomalously high the * 3 He. pH data indicate that this single sample was from this depth and not inadvertently collected at a deeper depth.

Figure 4.  pH and  CO 2 are the changes in pH and ECO 2 respectively from their regional backgrounds. The inset in the top panel shows that decreases in the pH of seawater result from the addition of CO 2 and/or mineral acidity (H + ). The addition of CO 2 decreases pH and increases ECO 2, while the addition of H + decreases pH without increasing ECO 2. When only CO 2 is added, the slope of  CO 2 vs  pH is approximately 360µM/pH unit. When H + is added along with CO 2 the change in pH per CO 2 increases (slope decreases). When carbonate alkalinity is added pH increases, however when both carbonate alkalinity and CO 2 are added, pH decreases, but the decrease is less than that when only CO 2 is added. These results were modeled using a seawater carbonate modeling program [Lewis and Wallace, 1998] and the lines are best fit results for the addition of the fluids indicated to ambient seawater.