Supplementary Information. Analytics

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1 GSA DATA REPOSITORY S. Kutterolf et al. Supplementary Information Analytics Table DR1: Summary of Nicaraguan tephra properties. Eruption ages and erupted magma masses from Kutterolf et al. (2007, 2008). Maximum measured bromine and chlorine contents in melt inclusions are best approximated by pre-eruptive concentrations. The standard deviation around the mean Br content shows the range in melt inclusion data. The percentage of bromine portioned into a fluid phase is determined as the difference between the most undegassed to most degassed melt inclusion. The masses of bromine and chlorine degassed during each eruption are the difference between maximum inclusion and average matrix glass concentrations multiplied by erupted magma mass. Bromine, chlorine and EESC concentrations added to the stratosphere by these eruptions are calculated using the parameters given below the Table DR1. The bottom row of Table DR2 shows average values ignoring the exceptionally large Upper Apoyo eruption. 1

2 Table DR1: Summary of Nicaraguan tephra properties. Tephra Age Erupted magma mass Eruption column height * Maximum Br content in melt inclusions Std. deviation of single points Max. Br partitioning into fluid phase Average Br Degassed content in mass of matrix glass Br Maximum Cl content in melt inclusions Average Cl Degassed content in mass of matrix glass Cl Br concentration added to stratosphere Cl concentration added to stratosphere EESC added to stratosphere [ka] [kg] [km] [ppm] [%] [%] [ppm] [kg] [ppm] [ppm] [kg] [ppt ] [% rel.] [ppt ] [% rel.] [ppt ] [% rel.] Cosigüina E E E Masaya Tuff E E E Chiltepe Tephra E E E Masaya Triple Layer E E E Mateare Tephra c E E E San Antonio Tephra E na E E Xiloa Tephra E E E Upper Apoyeque Tephra E na E E Lower Apoyeque Tephra E E E Upper Ometepe Tephra E E E Upper Apoyo Tephra E E E Lower Apoyo Tephra E E E Fontana Tephra E na E E Unicit Tephra c E E E Averages with Upper Apoyo Tephra: 6.84E E Averages ignoring Upper Apoyo Tephra 2.73E E Assumptions: 10 wt% of emitted halogens reach the stratosphere; stratosphere has moles, i.e. 15% of moles of total atmosphere. Pre-industrial stratosphere concentrations approximated as: Br = 6 ppt, Cl = 550 ppt, EESC = 900 ppt (cf. 19). *Column heights are from Kutterolf et al. (2007) Brom partitioning is calculated assuming maximum bromine concentration from the inclusions of one sample as initial bromine content (100%) and minimum bromine content in the inclusions as most Br-depleted magma due to partitioning into the fluid phase. 2

3 Chlorine and major volcanic elements (Tables DR1 and DR4) have been determined using a JEOL JXA 8200 electron microprobe (EMP) at the GEOMAR in Kiel (Germany), using setups described in Kutterolf et al. (2011). Bromine in melt inclusions and matrix glasses of the tephras were analyzed with synchrotron radiation induced X-ray fluorescence analysis at beamline L, at the storage ring DORIS III at HASYLAB, Deutsches-Elektronen Synchrotron (DESY) in Hamburg, Germany. For the bromine measurements, the spatial resolution is controlled by beam size and geometry of the sample because the primary X-ray beam penetrates deep into the sample, in contrast to ion probe and electron microprobe, where only the uppermost volume of a sample at the surface is analyzed. We use doubly polished thin sections (thickness: µm) for the analysis of inclusions and host minerals. Capillaries were used to focus the X-ray spot to values between typically 10 to 40 µm, values which approximate the sample thickness. Two point measurements were performed per analyzed inclusion: one measurement resulting in a combined spectrum of host mineral and melt inclusion and a second measurement that records only the spectra of the host mineral. Bromine concentrations were first calculated for the host mineral and then calculated for the melt inclusion, taking into account the geometry of the inclusion, major element compositions and the densities of host minerals and inclusion glasses. Bromine concentrations are based on external calibration to measurements of reference samples performed within the same experimental session (121 measurements in total). Reference samples comprised glasses with Br contents between 1.2 and 18 ppm (Table DR2) leading to the calibration line shown in Figure 1 Supplement and the resulting equation Br sample (ppm) = *x 0.5, where x is the normalized peak area. This allows to calculate the bromine concentration for each measurement. The observed accuracy for bromine contents in reference samples was better than 15% at concentrations levels between ppm, with higher values close to the lower limits of detection (Figure 1 Supplement). In contrast to homogeneous matrix glasses, determination of Br contents in melt inclusions is additionally affected by the uncertainty in measuring the inclusion thickness optically, which adds an error of < 9%. During the course of the study, different excitation conditions were applied. Initially, measurements were made with polychromatic excitation conditions and an energy-dispersive Si(Li) detector (Fig. DR2), which is optimized to detect fluorescence at high energies, but the lower limits of detection for Br were found to be as high as 1.1 ppm for Fe-poor samples such as MPI-DING reference material ATHO-G, and more than 3 ppm in Fe-rich samples such as MPI-DING reference ML3B-G due to the high scattering background when using polychromatic excitation. In order to improve the detection limits for the samples that showed Br concentrations at or below lower limits of detection, analytical conditions were optimized for Fe-rich materials. Instead of polychromatic excitation, a quasi-monochromatic beam provided by a broad bandpass multilayer (ΔE/E = 2%, i.e., pink beam ) has been used (Fig. DR2). This reduces the scatter contribution and improves the signal to noise ratios. The excitation energy was selected with a double multilayer monochromator and set to 15 kev, i.e., slightly above the binding energy of the Br K-shell electrons to optimize detection of bromine by X-ray fluorescence. In this case, an energy-dispersive SDD detector is suitable to detect the fluorescence radiation because the maximum photon energy is then below 15 kev and not as high as 50 kev as in case of polychromatic excitation. To avoid detector overload by Fe fluorescence and the formation of pile-up peaks, a 0.18 mm thick Al absorber was 3

4 placed between sample and detector. This resulted in a reduction of Fe-K fluorescence recorded in the detector to values below 1% at a transmission > 45% for Br fluorescence (Figure 2 Supplement). The optimised set-up resulted in lower limits of detection for bromine of 0.3 ppm and 0.18 ppm in the MPI-DING reference glasses ML3B-G and ATHO-G, respectively. In the thin reference samples used in this study, lower limits of detection are less than 0.05 ppm for acquisition times of 300 sec. Table DR2: Reference samples with values for thickness, density and Br concentrations. Average peak areas result from 121 point measurements taken during area scans with acquisition times of 300 sec/point over the entire term of the analysis. Errors are given for the area scan deviations and the peak area estimation. The peak areas were normalised to sample time, thickness and density and then used for a calibration line for Br. Reference Peak area average Error [%] Concentration [ppm] Thickness [µm] Density [g/cm 3 ] Peak area normalised Error [%] KN PN A CFA KANKR

5 Figure DR1. Br concentrations vs. average normalised peak area of reference samples as shown in Table S1. The calibration line has been used to calculate the Br concentrations in the samples (y (ppm) = *x 0.5). 5

6 Figure DR2. Demonstration of the improvement of experimental set-up for samples with low Br contents: Br is not detectable in the reference glass ML3B-G with polychromatic excitation conditions (top). With the pink beam, lower limits of detection are significantly improved and Br is detectable in the glass. However, Br detection is hampered by the formation of Fe pile-up peaks in Fe-rich samples. This negative effect can be ruled out by the use of a 0.18 mm thick Al foil placed between sample and detector (sample thickness: 100 µm; Br concentration: 3 ppm). Atmospheric Assumptions We use the assumptions that have also been used in the WMO ozone assessements and in publications by Textor et al. (2003) like it is dicussed in the main text. For the estimations how stratospheric halogen contents are affected by additional volanic halogen emission we assume that 10% of emitted halogens reach the stratosphere (all eruption column heights >15 km) 6

7 (Textor et al. 2003). For calculations of atmospheric halogen load due to volcanic eruptions to the global stratosphere we used published accepted values after Jacob (1999). Accordingly, the stratosphere has mol halogen, which is 15% of mol of the total atmosphere. Since anthropogenic emissions of bromine decreased from 65 kt/yr in to 37 kt/yr in 2008, while chlorine decreased from 1291 to 343 kt/yr over the same time period (Montzka et al., 2011) present day stratospheric halogen loading becomes more and more pre-industrial like where the stratospheric concentration in 1980 are given as a fixpoint since then stratospheric measurements of halogens become continously. Those pre-industrial stratosphere concentrations are approximated as: Br = 6 ppt, Cl = 550 ppt, EESC = 900 ppt refering to chapter 1 of the WMO ozone assessment (Montzka et al. 2011) Individual Measurements Table DR3: (see next page) Results for the individual measurements. Major elements and chlorine data stem from same inclusion like the bromine measurements if exposed on surface. If bromine measurement is from inside the crystal alternative surficial melt inclusion from same crystal has been taken (+) or an average from at least 5 different melt inclusions of the same sample (#) are used. (*) Bromine concentrations of matrix glasses are estimated to be the same like comparable measurements from chemical similar tephras from the same or nearby volcanic complex. Error of thickness determination is given in % and represents 1 µm accuracy. The combined maximum possible bromine concentration error results from the maximum possible analytical error (<15%) and the respective uncertainty in inclusion thickness per inclusion measurement. References supplement: Kutterolf, S., Freundt, A., and Peréz, W., 2008, The Pacific offshore record of Plinian arc volcanism in Central America, part 2: Tephra volumes and erupted masses: Geochem. Geophys. Geosys., v. 9, no. 2, p. doi: /2007gc Kutterolf, S., Freundt, A., Peréz, W., Wehrmann, H., and Schmincke, H.-U., 2007, Late Pleistocene to Holocene temporal succession and magnitudes of highly-explosive volcanic eruptions in west-central Nicaragua: J. Volc. Geo. Res., v. 163, p Kutterolf S, Freundt A, & Burkert C (2011) Eruptive history and magmatic evolution of the 1.9 ka Plinian dacitic Chiltepe Tephra from Apoyeque volcano in west-central Nicaragua, Bull Volc. 73, , doi: /s Textor C, Graf HF, Herzog M, & Oberhuber JM (2003) Injection of gases into the stratosphere by explosive volcanic eruptions. J. Geophys. Res. 108(4606), doi: /2002jd (2003). Jacob DJ (1999) Introduction to Atmospheric Chemistry. 267 (Princeton University Press, 1999) Montzka, S., Reimann, S., O Doherty, S., Engel, A., Krüger, K., Sturges, W. T., and Authors), C. L., 2011, Ozone-Depleting Substances (ODSs) and Related Chemicals, Chapter 1. 7

8 Table DR3 Lith. Unit sample name type sample thickness [µm] thickness surface-top inclusion/gl inclusion [µm] s [µm] bottom inclusionbottom Na 2O [wt%]; sample error 1µm [%] normed to [µm] 100% P 2O 5 [wt%]; normed to 100% FeO [wt%]; SiO 2 [wt%]; normed to normed to 100% 100% CaO [wt%]; normed to 100% MgO [wt%]; K 2O [wt%]; normed to normed to 100% 100% MnO [wt%]; Al 2O 3 [wt%]; normed to normed to 100% 100% TiO 2 [wt%]; normed to 100% measured total [wt%] Br [ppm] combined analytical Br matrix (<15%) and Cl [ppm] Cl/Br Br/K delta Br glass average thickness error [ppm] Upper Ometepe Tephra UOT* N344a-2 inc * 10.1 UOT* N344a-3 inc(1) * UOT* N344a-3 inc(2) * Lower Apoyo Tephra LAT N442-1 inc(1) LAT N inc(2) LAT N inc(2) LAT N inc (1) LAT N inc(2) LAT N442-2 inc(3) LAT N442-4# inc(1) LAT N442-4# inc(2) LAT N442-5 inc(3) LAT N333-a# inc LAT N333-b# inc LAT N442-3 gls Upper Apoyo Tephra UAT N450-5 inc(1) UAT N450-5 inc(1) UAT N450-5 inc(2) UAT N450-5 inc(3) UAT N450-1 inc(1) UAT N450-1 inc(1) UAT N450-3 inc(2) UAT N450-3 inc(3) UAT N450-4 inc(1) UAT N450-6 gls UAT N450-6 gls UAT N450-3 gls UAT N450-3 gls Chiltepe Tephra CT N inc(1) CT N inc(2) CT N inc CT N inc CT N562-4# inc CT N562-4# inc CT N241-a inc CT N562-5 gls CT N562-6 gls CT N562-7 gls Xiloa Tephra XT* N260-3 inc(1) * 8.8 XT* N260-3 inc(2) * 4.57 XT* N260-4 inc(1) * 2.75 XT* N inc(2) * 4.11 XT* N inc(2) * 3.99 XT* N259 inc * 4.74 Mateare Tephra MaT N250-2 inc(3) MaT N250-4 inc(1) MaT N250-4 inc(1) MaT N250-4 inc(2) MaT N250-5 inc MaT N250-a+ inc(1) MaT N250-a+ inc(2) MaT N255-b# inc Mat N250-1 gls Cosiqüina eruption 1835 N402-2 inc(1) N402-2 inc(1) N inc(2) N inc(2) N inc N402-5 gls Unicit Tephra UT* N inc(1) * 3.53 UT* N inc(2) * 3.14 UT* N22-01 inc * UT* N22-a inc * 6.18 Lower Apoyeque Tephra Laq* N inc * 3.98 Laq* N inc * 4.88 Laq* N inc * 4.32 Masaya Triple Layer MTL W25C6-15 inc MTL W25C6-17 inc MTL W25C6-18 inc(1) MTL W25C6-18 inc(2) MTL W67e15-7b gls MTL W23b7b-5 gls MTL W23b7b-9 gls Masaya Tuff MT W31A5d-10 inc MT W28A8f-11+ inc(1) MT W28A8f-11+ inc(2) MT W28A8f-15+ inc MT W28A8f-14+ inc MT W28A8f-18 inc MT W28A8f-19+ inc MT W31a5d gls MT W31a5d gls Fontana Tephra FT* N69-3 inc San Antonio Tephra SAT W67B6-1b inc SAT W67B6-1c gls Upper Apoyeque Tephra Uaq* N8-1 inc * 6.37 major elements and chlorine data are from same inclusion like the bromine measurements if on surface exposed; otherwise melt inclusion from same crystall (+) or an average from at least 5 different inclusions of the same sample (#) are used *Bromine concentrations of mat glasses are estimated to be the same like the others from the same or nearby volcanic complex error of thickness determination is given in % and represents one µm accuracy. Combined maximum possible bromine concentration error results from the maximum possible analytical error (<15%) and the respective uncertainty in inclusion thickness per inclusion measurement