The 1257 Samalas eruption (Lombok, Indonesia): The single greatest stratospheric gas release of the Common Era

Abstract

Large explosive eruptions inject volcanic gases and fine ash to stratospheric altitudes, contributing to global cooling at the Earth’s surface and occasionally to ozone depletion. The modelling of the climate response to these strong injections of volatiles commonly relies on ice-core records of volcanic sulphate aerosols. Here we use an independent geochemical approach which demonstrates that the great 1257 eruption of Samalas (Lombok, Indonesia) released enough sulphur and halogen gases into the stratosphere to produce the reported global cooling during the second half of the 13th century, as well as potential substantial ozone destruction. Major, trace and volatile element compositions of eruptive products recording the magmatic differentiation processes leading to the 1257 eruption indicate that Mt Samalas released 158 ± 12 Tg of sulphur dioxide, 227 ± 18 Tg of chlorine and a maximum of 1.3 ± 0.3 Tg of bromine. These emissions stand as the greatest volcanogenic gas injection of the Common Era. Our findings not only provide robust constraints for the modelling of the combined impact of sulphur and halogens on stratosphere chemistry of the largest eruption of the last millennium, but also develop a methodology to better quantify the degassing budgets of explosive eruptions of all magnitudes.

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Scientific RepoRts | 6:34868 | DOI: 10.1038/srep34868
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The 1257 Samalas eruption
(Lombok, Indonesia): the single
greatest stratospheric gas release
of the Common Era
Céline M. Vidal1, Nicole Métrich1, Jean-Christophe Komorowski1, Indyo Pratomo2,
Agnès Michel1, Nugraha Kartadinata3, Vincent Robert4 & Franck Lavigne5
Large explosive eruptions inject volcanic gases and ne ash to stratospheric altitudes, contributing to
global cooling at the Earth’s surface and occasionally to ozone depletion. The modelling of the climate
response to these strong injections of volatiles commonly relies on ice-core records of volcanic sulphate
aerosols. Here we use an independent geochemical approach which demonstrates that the great
1257 eruption of Samalas (Lombok, Indonesia) released enough sulphur and halogen gases into the
stratosphere to produce the reported global cooling during the second half of the 13th century, as well
as potential substantial ozone destruction. Major, trace and volatile element compositions of eruptive
products recording the magmatic dierentiation processes leading to the 1257 eruption indicate
that Mt Samalas released 158 ± 12 Tg of sulphur dioxide, 227 ± 18 Tg of chlorine and a maximum
of 1.3 ± 0.3 Tg of bromine. These emissions stand as the greatest volcanogenic gas injection of the
Common Era. Our ndings not only provide robust constraints for the modelling of the combined impact
of sulphur and halogens on stratosphere chemistry of the largest eruption of the last millennium, but
also develop a methodology to better quantify the degassing budgets of explosive eruptions of all
magnitudes.
Sulphur (S) gases injected into the stratosphere during plinian eruptions are converted into sulphate aerosols
that travel around the globe and backscatter solar radiation, resulting in a net cooling of the troposphere and
the Earth’s surface1. Besides the eect of sulphate aerosols, volcanogenic halogens and especially chlorine (Cl)
and bromine (Br) may induce the catalytic destruction of the ozone layer2. Although these processes have been
observed on a very small scale for a number of recent explosive eruptions such as the 1963 Agung, 1982 El
Chichón and 1991 Pinatubo events3, the eects of large historic silicic eruptions on climate and atmospheric
chemistry remain poorly constrained, with hitherto unexplored feedbacks. e reconstruction of climate forcing
associated with explosive eruptions involves several scientic disciplines, as it strongly depends on a variety of
parameters including the height of injection, the gas ux and the latitude of the volcanic source. For past plinian
eruptions suspected to have triggered or enhanced climate cooling, temperature reconstructions are commonly
based on the amount of associated sulphate emissions inferred from glaciological records. It is furthermore com-
monly admitted that the presence of a pre-eruptive vapour phase renders the quantication of the emissions of
sulphate and other volatile species of past eruptions particularly challenging4–6.
The 1257 eruption of Mt Samalas, a part of the Rinjani volcanic complex (Fig.1) on Lombok Island
(Indonesia), has been recognized as the “mystery eruption”7 associated with the largest sulphate spike of the
last 2.3 ky recorded in cores from both Arctic and Antarctic ice sheets8. is continuous four-phase eruption
evacuated 40 ± 3 km3 of trachydacitic magma during tens of hours, producing plinian plumes that rose up to
43 km in the stratosphere and tephra ngerprinted up to 660 km from the source, thus standing as the most
1Institut de Physique du Globe de Paris, Université Sorbonne Paris Cité, CNRS UMR 7154, Paris, 75005, France.
2Museum of Geologi, Badan Geologi, Bandung, 40122, Indonesia. 3Center of Volcanology and Geological Hazards
Mitigation, Badan Geologi, Bandung, 40122, Indonesia. 4Observatoire Volcanologique et Sismologique de la
Guadeloupe IPGP, Gourbeyre, 97113, France. 5Laboratoire de Géographie Physique UMR 8591, Université Paris 1
Panthéon-Sorbonne, 92195 Meudon, France. Correspondence and requests for materials should be addressed to
C.M.V. (email: vidal@ipgp.fr)
received: 10 June 2016
accepted: 20 September 2016
Published: 10 October 2016
OPEN

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Scientific RepoRts | 6:34868 | DOI: 10.1038/srep34868
powerful eruption of the last millenium9. Archaeologists recently determined a date of 1258 for mass burial of
thousands of medieval skeletons in London10, that could be linked in some respect to climatic perturbations in
the Northern Hemisphere by the 1257 Samalas eruption. Indeed, medieval chronicles in Northern Europe7 doc-
ument the occurrence of initial warming in the early winter of 1258 just following the eruption, that was followed
by extensive wet and cold climatic conditions in 1259 that may have impacted crops and contributed to the onset
and magnitude of famines at that time for some regions of the Northern Hemisphere. e 1257 Samalas eruption
might also have contributed to the onset of the Little Ice Age11.
e climate-forcing associated with the 1258–1259 sulphate anomaly in ice-cores has been the subject of
intense research12–15, suggesting a range of sulphate yields until the source of the eruption was found. e recent
re-evaluation of the record of volcanic sulphate deposition based on an extensive array of Antarctic ice cores sug-
gested that a total of 170 Mt of SO2 (85 Tg of S) would have been released to produce the observed sulphate spikes,
greater than the 45 Mt of SO2 estimated for the 1815 Tambora eruption16. Temperature reconstructions based
on tree-ring proxies and ice-core records showed that the emission of 96 to 138 Tg of SO2, the most probable
scenarios, would have induced an extra-tropical summer cooling over land of − 0.6 °C to − 5.6 °C during a period
of 4–5 years17. e discrepancies between these estimates derived from ice-cores data and modelling reect the
complexity of climate reconstructions based on hypothetical S yields based on distal proxies.
e quantication of volcanogenic volatile emissions at the source commonly relies on the residual amount
of volatiles dissolved in silicate melts prior to eruption recorded in small droplets of magma trapped in crystals
(melt inclusions) of the erupted products18. Here we propose an alternative approach based on melt inclusions
recording the dierent steps of magma evolution, including melt inclusions representative of both the magma that
fed the eruption (a three-phased mixture of melt, gas and crystals) and of the residual melt.
Pre-eruptive magmatic conditions
The detailed petrology and mineralogy of the Holocene lavas and scoria fallouts of the Rinjani volcanic
complex, including the magmatic processes leading to the 1257 Samalas eruption, are presented by Métrich
et al. (in review), and are briey summarised hereaer. e 1257 eruption evacuated a chemically homogeneous
magma body of trachydacite (64.0 ± 0.4 wt% of SiO2; 8.1 ± 0.1 wt% of Na2O + K2O, volatile free) that derived from
a parent high alumina basalt magma through fractional crystallization. e trachydacitic magma crystallised and
degassed at temperatures of 900 °C to 980 °C. Its mineral paragenesis typically consists of plagioclase showing
a bi-modal distribution with patchy zoned cores (An82–75) surrounded by bands (An50–46), in association with
amphibole (magnesio-hastingsite), orthopyroxene (clinoenstatite), rare clinopyroxene (augite), titano-magnetite,
iron sulphide and apatite.
Here we combined the detailed geochemical study of minerals and melt inclusions with matrix glass and
whole-rock analyses (major, trace, S, Cl and Br) to characterise the composition of the pre- and post-eruptive
magmatic system, and further quantify the volatile budget of the 1257 eruption. Samples from the four phases of
the 1257 trachydacitic eruption and of the 712 A.D. basaltic scoria fallout have been examined (see Supplementary
Sample description and Figure S1). Our dataset is complemented by melt inclusions from the trachydacitic pum-
ice of the 2550 B.P. eruption19 (compositions are reported in Supplementary Tables S1, S2 and S3). Major and
trace elements denote the bi-modality of the magma compositions and the lack of intermediate andesitic magma
(Fig.2a,b). e overall evolutionary trend is perfectly illustrated by the positive correlation between Rb and 
(Fig.2b), suggesting that the 1257 trachydacite derived from the basalt through fractional crystallization of ~81%
(Methods). Furthermore, compositions of olivine-hosted melt inclusions match that of the whole-rock parent
basalt of the 1257 trachydacite (Fig.2b). Most remarkable are the melt inclusions in plagioclase An82–75 that are
representative of the whole trachydacitic magma (60.5 ± 1.3 wt% of SiO2; 9.0 ± 0.9 ppm of ) whereas more sodic
plagioclase (An50–46), amphibole and pyroxenes trapped melts that recorded the evolution towards the residual
trachydacitic composition of the matrix glass (68 ± 1 wt% of SiO2; 16.3 ppm of ) due to in-situ crystallization at
shallow depth. Depicting the magma evolution respectively associated with fractional crystallization and in-situ
Figure 1. Map of the Lesser Sunda Islands and their active volcanoes. SRTM DEM at 3 arcsecond (~90 m)
resolution (http://srtm.csi.cgiar.org)63 of Bali, Lombok and Sumbawa. is map was generated using the Esri
ArcMapI 10.1 soware (http:www.esri.com).

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crystallization is an innovative approach that enables to decipher the volatile evolution from the parent basalt to
the 1257 trachydacite. We further quantify the distribution of sulphur and halogens between the pre-eruptive
silicate melt (melt inclusions), the volatile-bearing mineral phases (sulphide (S), apatite (SO2, Cl) and amphi-
bole (Cl)), and the vapour phase (Fig.3) consisting of gas species exsolved during in-situ crystallization of the
trachydacite in the shallow crust, with possible incremental inux of deeper-derived vapour phase20. Finally we
establish the degassing budget of the 1257 Samalas eruption by comparing the pre-eruption and the post-eruption
trachydacitic magma. We stress that volatile partitioning between the vapour phase and such sulphide-saturated
calc-alkaline melts at 900–980 °C is still poorly constrained by experimental data.
e evolution of volatile species illustrated in Fig.4 reects the dierential ability of each species to be frac-
tionated into the vapour phase and minerals. Water contents of melt inclusions remain relatively constant along
the path of magma dierentiation (Fig.4a,b). e basalt displays average water contents of 3.5 ± 0.2 wt%, a typical
Figure 2. Melt inclusions record the magma evolution leading to the 1257 eruption. (a) K2O vs SiO2
variation diagram for the Rinjani-Samalas calc-alkaline suite including whole-rocks, melt inclusions in olivine
of the 712 high alumina basalt (Fo is olivine forsterite content, i.e. 100 × Mg/(Mg + Fe)), in plagioclase of
2550 B.P. and 1257 pumice clasts (An is anorthite content, i.e. 100 × Ca/(Ca + Na)), in clino-(cpx), ortho-
(opx) pyroxene, amphibole, and matrix glasses of the 1257 eruptive products. Compositions are normalised
to 100 wt%, free of volatiles. e Rinjani-Samalas suite plots in between the whole-rock compositional elds
of 1815 Tambora53 and 1963 Agung64,65 products, highlighting the enrichment in K2O of magmas towards
the East of the Lesser Sunda arc. (b) Rb- positive correlation indicates that the 1257 trachydacite derived
from its parent basaltic magma through a dominant process of fractional crystallization. Plagioclase An82–75-
hosted melt inclusions are representative of the 1257 whole magma composition, whereas plagioclase An50–46-
hosted melt inclusions record its shallow depth in-situ crystallization. (c) Cu vs  variation diagram showing
strong Cu fractionation during magma dierentiation recording the prevalent Cu-sulphide segregation. See
Supplementary Figures S2 and S3 for more major and trace element variation diagrams.

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value for arc basalts21. e 1257 trachydacite magma derived from the basalt contains 3.9 ± 0.1 wt% of H2O, a
value measured in melt inclusions in plagioclase An82–75. Such a dissolved amount of H2O is well below the max-
imum water concentrations (8–< 10 wt%) of amphibole-bearing dacite crystallizing at 300–400 MPa under
water-saturated conditions22. is suggests a drastic loss of water during fractional crystallization and most likely
during magma decompression and ascent. e distribution of the H2O concentrations in melt inclusions in pla-
gioclase An50–46 indicates that ~70% cluster at 3.7 ± 0.3 wt% H2O (Supplementary Figure S4a), a value represent-
ative of the H2O concentration of the residual melt (Fig.4b). A few higher water contents (up to 5.5 wt%) reect
the multi-stage exsolution of water from the melt, and possibly magma mixing during relling of the 1257 trach-
ydacitic system. is feature is consistent with plagioclase textures and the temperature gradient (900–980 °C)
calculated from thermometers (Métrich et al., in review). Fluid inclusions fully support the presence of a free
water-rich vapour phase (Supplementary Figure S5a,b). No dissolved or exsolved CO2 was detected, even though
some uid inclusions show evidence of carbon bearing-complexes (Supplementary Figure S5e). Considering that
the trachydacitic system contains an initial amount of 3.9 ± 0.1 wt% of dissolved H2O, we estimate a proportion
of exsolved water of 3.5 wt% during in-situ crystallization of the trachydacite (Fig.4a). e water content of the
residual melt corresponds to a uid pressure
=PP()
HO total
2
of 90–120 MPa under equilibrium conditions, sug-
gesting an upper limit of magma storage of 3.3–4.4 km assuming a crustal density of 2.8 g/cm3 23. Hence, the 1257
Samalas eruption was sustained by a trachydacite reservoir developed in the upper crust similarly to other large
plinian eruptions24.
Sulphur concentrations in melt inclusions reect a more complex behaviour (Fig.4c,d). e parent basalt
displays an average S content of 1940 ± 90 ppm, a value commonly measured in moderately oxidized, hydrous,
arc basalts20. Poly-metallic sulphides (Cu-Fe-S) partitioning Cu (Fig.2c) do not occur in S-rich melt inclusions
but are ubiquitous in partly degassed glass embayments. e trachydacitic system displays a total S content of
870 ± 20 ppm distributed between the melt, the S-bearing minerals and the free gas phase. Sulphur concen-
trations in melt inclusions of clinopyroxene (150 ± 20 ppm), orthopyroxene (180 ± 45 ppm) and amphibole
(185 ± 45 ppm) are similar to that of the most evolved plagioclase-hosted melt inclusions (Fig.4d). Matrix glasses
Figure 3. Volatile repositories in the 1257 trachydacitic system. Composition of the residual melt is recorded
by melt inclusions trapped in cpx, opx and amphibole whereas that of the whole magma (melt + mineral
phases + pre-eruptive vapour) is preserved by melt inclusions in plagioclase An82–75. e existence of pre-
eruptive vapour is illustrated by the occurrence of water-rich uid inclusions in minerals (Supplementary
Figure S5). CO2 is very likely present in pre-eruptive vapour. e whole system is likely the result of the mixing
of trachydacitic magma batches displaying distinct volatile contents (Supplementary Figure S4f).

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are the most degassed endmember with 50 ± 20 ppm of S (Supplementary Table S2). e positive correlation
of S and FeO (Fig.4d) corresponds to the S concentration at sulde saturation (SCSS)25, in agreement with the
occurrence of iron sulphide globules (up to 60 μm in size) entrapped with apatite in phenocrysts (mostly amphi-
bole). However, the extent of FeO content range reects the possible eect of magma mixing between melts
displaying distinct S contents. e composition of iron sulphides (Supplementary Table S4) enabled to esti-
mate a proportion of 0.01% of Fe-sulphides in the system (Methods), suggesting that they removed a negligible
amount of S (~50 ppm) from the melt. Furthermore, the range of S concentrations in apatite (0.01–0.26 wt% of S,
Figure 4. Melt inclusions record the volatile evolution through magma dierentiation and in-situ
crystallization. (a) H2O vs  and (b) H2O vs FeO* contents in melt inclusions reect water exsolution through
magma dierentiation. Reported average H2O content of basalt are calculated considering melt inclusions
unaected by H+ diusion through host mineral (Supplementary Figure S6b). (c) S vs  variation diagram in
melt inclusions. (d) Positive correlation of S and FeO* in the 1257 melt inclusions is consistent with sulphide
saturation. e S concentration at sulphide saturation (SCSS, dashed curve) was calculated with model B of
Fortin et al.25. (e) Cl vs  contents in melt inclusions and whole-rocks suggest that Cl has an incompatible
behaviour during basalt dierentiation. (f) Cl vs FeO* contents in melt inclusions, whole-rocks and matrix
glasses reect mixing between trachydacitic melts and Cl exsolution during in-situ crystallization of the 1257
trachydacite. e process of mixing is also demonstrated by the positive correlation of S and Cl (Supplementary
Figure S4f). Symbols as in Fig.2. Average initial volatile contents of melt inclusions representative of the basaltic
magma and of the whole 1257 system as well as whole-rock compositions are reported with error bars (1σ).

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Supplementary Figure S6) indicates the sporadic inux of SO2 in the gas phase26, as supported by the occurrence
of submicroscopic crystals of anhydrite and gypsum (and other S-bearing complex minerals) on the walls of uid
inclusions (Supplementary Figure S5c–e).
e average Cl concentration in Rinjani-Samalas basalts (830 ± 80 ppm) is typical of a volcanic arc domain27.
e trachydacitic system displays a total Cl content of 3500 ± 175 ppm (Fig.4e) accounting for the Cl distributed
between the melt, the Cl-bearing minerals (amphibole and apatite) and the pre-eruptive vapour. Simple mass
balance calculation based on apatite composition (42.9 ± 0.2 wt% of P2O5 and 0.89 ± 0.02 wt% C l; Supplementary
Table S5) indicates that up to 1.5 ± 0.3% of apatite crystallised (Methods) with a negligible eect on the Cl con-
centration of the melt (~130 ppm). Furthermore, amphibole from the 1257 trachydacite with an average Cl con-
tent of 700 ± 100 ppm (Supplementary Table S6) only removed a minor amount of Cl from the melt. Residual
melts trapped in pyroxenes (2250 ± 140 ppm), and amphibole (2170 ± 210 ppm) share similar Cl concentrations
with matrix glasses (2170 ± 210 ppm; Supplementary Table S2), indicating low Cl exsolution from the melt dur-
ing eruption. Cl is therefore dominantly exsolved into the pre-eruptive vapour phase at shallow depth, a feature
that explains the signicant decrease of the Cl/ ratio during in-situ crystallization of the trachydacitic magma
(Fig.4e). Furthermore, the positive correlation between Cl and FeO (Fig.4f) corroborates mixing of partly
degassed trachydacitic magma batches diering by their volatile contents.
Pumice clasts from the four phases of the eruption contain on average 1230 ± 45 ppm of Cl (Table1). is
value is in agreement with the residual Cl content of matrix glasses aer correction for crystallization. Br contents
average 1.6 ± 0.2 ppm in basaltic scoria and 2.92 ± 0.08 ppm in 1257 pumice clasts (Table1). e average Br/Cl
ratio of the basaltic whole-rock (3.7 ± 0.4 × 10−3) is in agreement with the upper range of published values for
arc/back-arc basin basalts (1–3.2 × 10−3)28. is probably suggests a minimum eect of syn-eruptive degassing
on the Br/Cl ratio29. Considering that the whole-rock Br/Cl ratio (3.7 ± 0.4 × 10−3) is characteristic of the basaltic
magma ratio, we calculated indirectly a Br concentration of 3.1 ± 0.4 ppm in the basalt containing 830 ± 80 ppm
of Cl (Table1). Such a Br content is comparable to the concentrations measured in basaltic melt inclusions of
 S Cl Br
Concentrations (ppm)
Undegassed residual melt Cundegassed RM (MIs cpx, opx, amph) 170 ± 50 2235 ± 155
Degassed residual melt Cdegassed RM (Matrix glass) 16.3 50 ± 20 2170 ± 110
Pre-eruptive trachydacite Cpre–eruptive (MIs plagioclase ~An76) 9.0 ± 0.9 870 ± 20 3500 ± 175
Trachydacitic whole-rock CWR 9.5 ± 0.9 80 ± 20 1230 ± 45 2.92 ± 0.08
Parent basalt Cbasalt (MIs olivine ~Fo76) 1.7 ± 0.2 1940 ± 90 830 ± 80 3.1 ± 0.4
Basaltic whole-rock (712 AD scoria) 2.20 ± 0.07 39 ± 1 428 1.6 ± 0.2
Classic petrologic method
Volatile i loss Δ i = Cundegassed RM − Cdegassed RM × XRM (ppm) 140 ± 50 960 ± 190
Minimum mass released (Tg) 14 ± 5 96 ± 19
New approach: whole trachydacitic system
Volatile i loss Δ i = Cpre–eruptive − CWR (ppm) 790 ± 30 2270 ± 180
Mass released (Tg) 79 ± 6 227 ± 18
Contribution of the parent basalt
eoretical amount of volatile available Csystem (ppm) 10090 ± 1480 4300 ± 720 16 ± 3
SCu–Fe–S (ppm) 690 ± 225
Suid (ppm) 8500 ± 1500
mS
fluid
assuming 1.5 wt% uid (Tg) 13 ± 6
Volatile i loss Δ i = Csystem − CWR (ppm) 13 ± 3
Maximum mass released (Tg) 92 ± 8 1.3 ± 0.3
Global atmospheric mixing ratios (ppbv of Cl and pptv of Br) 36 90
Stratospheric emissions (Tg) 63–73 23–55 0.13–0.33
Table 1. Volatile degassing budget calculations. MIs: melt inclusions; cpx: clinopyroxene; opx:
orthopyroxene; amph: amphibole. Calculations of mass of volatile released and amount of S sequestered in Cu-
Fe-S detailed in the method. XRM is the residual melt fraction, i.e. the ratio of  contents in the 1257
trachydacitic whole-rock and the residual melt (0.59). e concentration
Ci
system
of each volatile species i in the
1257 trachydacitic system is derived from the
C C/
iTh
ratio of the parent basalt assuming the conservation of the
ratio of volatile contents respective to  during basalt dierentiation. =××
mmXS
S
fluid
magma
fluidfluid
, where
Xuid is the maximum amount of deeper-derived vapour (1.5 wt%). e maximum mass of S released is the sum
of the emissions of the trachydacitic system (79 Tg S) and
mS
fluid
(13 Tg S). See text for Cl and Br. Global
atmospheric (troposphere and stratosphere) mixing ratios of halogen X is given by =
X[ ]
atm
n
n
X
air
, where nX is the
amount of substance (moles) of halogen X released by the eruption, and nair is the amount of substance (moles)
of air in the atmosphere, i.e. 1.5 × 1020 mol. Stratospheric emissions calculated as 80% of S and 10–25% of Cl and
Br total emissions38. SO2 emissions (in Tg, i.e. megatons) correspond to twice the reported S emissions.

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Masaya, Nicaragua30. We stress that from the onset to the end of the 1257 eruption, whole-rocks record similar
volatile concentrations (S, Cl, Br), suggesting a relatively constant extent of the syn-eruptive degassing.
Atmospheric volatile emissions of the 1257 Samalas eruption
e atmospheric volatile yields from volcanic eruptions are usually estimated using the petrologic method, which
involves substracting the volatile concentrations in the residual melt corrected for crystallization from those
of undegassed melt inclusions31. e pre-eruptive volatile contents of the residual melt (170 ± 50 ppm of S and
2235 ± 155 ppm of Cl) and that of the degassed matrix glass (50 ± 20 ppm of S and 2170 ± 110 ppm of Cl) indi-
cate volatile losses of 140 ± 50 ppm of S and 960 ± 190 ppm of Cl (Table1). When scaled to the mass of erupted
magma (calculated using a volume of 40 km3 and a DRE density of 2500 kg/m3, see Methods), the syn-eruptive
devolatilisation of the melt would have released 14 ± 5 Tg of S (28 Tg of SO2) and 96 ± 19 Tg of Cl. is calculation
neglects, however, the amounts of S and Cl stored in the pre-eruptive vapour phase, and thus provides minimum
estimates.
In the following, we quantify the atmospheric yields using the representative volatile contents of the whole
1257 trachydacitic system. Its S content is recorded by melt inclusions trapped in plagioclase An82–75 (Table1)
and accounts for the S allocated in the trachydacitic melt, the pre-eruptive vapour phase, and the iron sulphides
(Fig.3). We further assume that sulphide breakdown prior to eruption through interaction with a pre-existing
uid phase32 did not occur, as they likely remained stable prior to eruption. Given the negligible eect of iron sul-
phide on the S dissolved in the melt, the S degassing (melt + vapour) is provided by the dierence between the ini-
tial S concentration of the system (870 ± 20 ppm) and the S content of the 1257 whole-rock (80 ± 20 ppm), which
yields a loss of 790 ± 30 ppm (Table1). Such a loss corresponds to the emission of 79 ± 6 Tg of S (158 ± 12 Tg of
SO2).
e highest Cl content (3500 ± 175 ppm) recorded by the trachydacitic melt inclusions representative of the
1257 whole-rocks (Fig.4e) accounts for the Cl allocated in the melt and in the pre-eruptive vapour phase. Using
the average Cl concentration in the whole-rock (1230 ± 45 ppm), we calculate a Cl loss of 2270 ± 180 ppm, indic-
ative of an atmospheric discharge of 227 ± 18 Tg of Cl (Table1).
Underplating basalt may contribute to volatile emissions during plinian eruptions of silicic magmas6. Despite
the absence of any obvious petrologic evidence of the contribution of the parent basalt into the degassing budget,
we further explore how the potential contribution of a deeper-derived vapour phase would have increased the
atmospheric emissions of the 1257 eruption. Using the S concentration of basaltic melt inclusions, we calculate
that the trachydacitic system derived through 81% of fractional crystallization of the parent basalt would have
contained 1 wt% of S (Ssystem; Table1), distributed between the trachydacitic melt (Smelt), the pre-eruptive vapour
phase (Suid), and the poly-metallic sulphides (SCu–Fe–S). e Cu concentration decreases from basalt to trachydac-
ite (Fig.2c) indicating that segregated Cu-bearing sulphides (Cu–Fe–S) sequestered a maximum of 690 ppm of S
(Methods; Table1). Considering such a sink of S in Cu-sulphides and the proportion of S dissolved in the trach-
ydacitic melt (870 ± 20 ppm), the pre-eruptive vapour phase would have stored a maximum of 8500 ppm of S. is
suggest a partition coecient
DS
fluidmelt/
of 13, which lls a gap of experimental constraints on S solubility for these
magma conditions. In order to calculate the mass of S that could have been emitted by additional pre-eruptive
vapour, it is necessary to assess the amount of water lost during the magma dierentiation. An amount of 5–6 wt%
uid is thought to be an upper limit beyond which percolation would occur and the uid would be lost from the
system33. Furthermore, an average value of 5 wt% uid is consistent with the discrepancy between the water con-
tent of the trachydacitic melt (3.7 ± 0.3 wt%) and the maximum H2O concentrations that an amphibole-bearing
dacite could display (8–< 10 wt%)22. Assuming a maximum of 5 wt% of uid in the system including 3.5 wt%
exsolved during in-situ crystallization of the trachydacite, the parent basalt would have contributed to 1.5 wt% of
supplementary vapour. is corresponds to an addition of 13 ± 6 Tg of S onto the S budget (Table1). e large
uncertainty on this estimate reects the complexity of quantifying the proportion of water, the major component
of the vapour phase. e 1257 eruption would thus have released a maximum of 92 ± 8 Tg of S (184 ± 16 Tg of
SO2).
We estimate similarly a total theoretical Cl available in the trachydacitic system of 4300 ± 720 ppm (Table1).
Within the error, such concentration is relatively in agreement with the initial Cl content of the melt inclusions
representative of the 1257 whole-rocks (3500 ± 175 ppm), suggesting minor Cl fractionation by Cl-bearing phases
during basalt dierentiation. e potential contribution of the parent basalt onto the Cl budget is thus likely
negligible.
Partial exsolution of magmatic Br into pre-eruptive vapour may occur, and its uid/melt partition coecient
DBr
fluidmelt/
is typically much larger than
DCl
fluidmelt/
34. Following the previous reasoning, the initial Br concentration
calculated for the parent basalt indicates a total of 16 ± 3 ppm Br available in the trachydacitic system (Table1)
allocated in both the melt and the pre-eruptive vapour phase. Using the average Br content of the 1257
whole-rocks (2.92 ± 0.08 ppm), we calculate a Br loss of 13 ± 3 ppm that corresponds to a maximum emission of
1.3 ± 0.3 Tg of Br (Table1).
The largest volatile release of the Common Era
e 1257 Samalas eruption produced a S injection of 79 ± 6 Tg, equivalent to 158 ± 12 Tg of SO2 (Table1), and
a maximum of 184 ± 16 Tg of SO2 if the parent basalt contributed to the degassing budget. Hence, the inux of
volatiles from the basalt would not exceed 15% of the total budget. Furthermore, our new approach increases by
a factor of 5 the minimum S emission derived from the classic petrologic method. We stress that such emission
probably occurred within a day9, and is much higher than the total annual global volcanic SO2 ux of 15–21 Tg/yr
associated with atmospheric emissions from both quiescent and explosive degassing volcanoes35. In addition to
the prodigious S yield, the 1257 Samalas eruption emitted 227 ± 18 Tg of Cl, and a maximum of 1.3 ± 0.3 Tg of
Br taking into account the potential contribution of the basalt. ese yields stand as the largest volatile emissions

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of the Common Era (Fig.5), exceeding by a factor of two the SO2 emissions of the 946 Peaktu eruption (90 Tg of
SO2)36, and of the 1815 Tambora eruption (73–91 Tg of SO2) that had a devastating impact on climate on a global
scale. Furthermore, the Cl yield of the Samalas eruption constitutes the largest emission since the Minoan erup-
tion of Santorini, 3,600 y B.P.37. Although the Br emissions have been estimated for only a few Holocene eruptions,
the Br release of the 1257 Samalas eruption (1.3 ± 0.3 Tg) is similar to the maximum scenario of Br yield of the
Minoan eruption (1.5 Tg of Br)37, and one order of magnitude higher than the Br emission of the Chiltepe erup-
tion, 1.8 ka (0.125 Tg)30.
Stratospheric injection and potential impact on climate and atmospheric chemistry
Sulphur gases are scavenged by incorporation into ice particles in volcanic plumes before reaching the tropopause,
resulting in stratospheric emissions which probably represents 80% of the initial injection38. Such a process would
suggest that the 1257 Samalas eruption produced a stratospheric injection of ~126 Tg of SO2 (Table1), which
is within the range of the two SO2 stratospheric scenarios of 96 and 138 Tg of SO2 estimated based on climate
modelling and tree-ring based hemispheric temperature reconstructions17. If the parent magma contributed to
the degassing budget, the stratospheric injection of SO2 could reach up to 150 Tg, which should be considered as
a maximum value. Hence, our estimates corroborate the upper range of sulphate yields derived from ice-core data
and temperature reconstructions. We also stress that the low discrepancies between our stratospheric estimates
and ice-cores based scenarios may reect the ecient gas injection from the onset to the end of the eruption.
Indeed, the stratospheric loading of volatiles is correlated to the initial dynamics of an eruption that needs to be
suciently powerful to inject a pre-existing vapour phase accumulated at the top of the magmatic reservoir33,39
into the stratosphere via a high-ux gas jet and convective column before wholesale column collapse.
e input of both volcanic Br and Cl enhances the catalytic destruction of ozone because the resulting BrO is
a reaction partner for ClO40. Such reactions can occur either when halogens are released at tropospheric altitudes
or when they are directly injected into the stratosphere. e Cl and Br emissions of the 1257 Samalas eruption
represent initial atmospheric concentrations of 36 ppbv of Cl and 90 pptv of Br (Table1). For comparison, the
pre-industrial atmospheric Cl mixing ratio was 0.55 ppbv, corresponding to methyl chloride emissions from the
oceans, i.e. before the onset of anthropogenically dominated emissions, and increased up to 3.8 ppbv in the late
1990s, during the Antarctic ozone hole climax41,42. e pre-industrial Br mixing ratio was 5 pptv, and increased up
to 20 pptv in the late 1990s43. Hence, the 1257 Samalas eruption produced increments in globally averaged Cl and
Br concentrations that exceed the pre-1980 levels by a factor of 65 for Cl and 18 for Br, and the ozone-hole climax
concentrations by factors of 9 for Cl and 5 for Br. ese results likely suggest that the 1257 eruption discharged
enough halogen gases into the atmosphere to trigger ozone destruction cycles. We stress that such comparisons
should be made carefully, however, given that the mixing ratios calculated for the 1257 Samalas eruption corre-
spond to initial and local increases of Cl and Br concentrations, whereas background mixing ratios are global
annual values.
A signicant proportion of Cl and Br released by the 1257 Samalas eruption was likely scavenged by hydro-
meteors during ascent in the plume and may not have reached the stratosphere. Although sattelite-based
Figure 5. e 1257 Samalas eruption produced the largest volatile emissions of the Common Era. Plots
of SO2, Cl and Br emissions (in Tg, i.e. megatons) for climate-impacting plinian eruptions. Yields of eruptions
before 1980 are from petrological studies. Fine lines represent the maximum estimates (associated with the
contribution of the parent basaltic magma in the case of the 1257 eruption). References: Minoan 3,600 y
B.P. (Greece)37; Peaktu 946 A.D. (DPRK/China)36; Huaynaputina 1600 (Peru)66; Tambora 1815 (Indonesia),
emissions re-calculated at 36–45 Tg S (73–91 Tg SO2) and 18–23 Tg Cl based on the syn-eruptive losses
(400 ppm S; 200 ppm Cl)53,67 and new volume estimates of 41 ± 4 km3 DRE68 and 51 km3 DRE69); Cosigüina 1835
(Nicaragua)30,70; Krakatau 1883 (Indonesia)71; El Chichón 1982 (Mexico)72; Pinatubo 1991 (Philippines)4.

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Scientific RepoRts | 6:34868 | DOI: 10.1038/srep34868
measurements of present-day volcanism enhanced our understanding of the fate of volcanic halogens in the
stratosphere, much remains to be investigated, in particular concerning Br emissions and potential eects of
large tropical explosive eruptions on stratospheric ozone44. Sophisticated plume experiments and modelling38
showed that 10% to 25% of halogen gases can reach the stratosphere, although the scavenging eciency strongly
depends on several parameters such as the latitude, the salinity of the uid, the gas phase composition and the
ability of ash particles to capture halogens45. Comparison of tropical versus high latitude eruptions shows that
tropical humid atmospheric conditions, including the occurrence of a typhoon, may cause ecient scavenging of
halogens as observed for the 1991 Pinatubo eruption46,47. It has been observed in the case of the 1982 El Chichón
eruption, however, that a high mass ux rate within a plinian plume can partly preserve halogens from being
scavenged, thus enhancing the stratospheric injection48. Considering that: (i) the 1257 Samalas eruption more
likely occurred between May and July 1257, i.e. during the Indonesian dry season7,17; and (ii) the strong mass ux
rates of the two plinian phases (2.8 × 108 kg/s during phase 1 and 4.6 × 108 kg/s during phase 3)9 are one order of
magnitude higher than the maximum ux rate of the 1982 El Chichón eruption (6.8 × 107 kg/s)49,50, we assume
that the stratospheric injection of halogens could likely have reached 10 to 25% of the initial load. is would
correspond to stratospheric injections of 23–57 Tg of Cl and 0.1–0.3 Tg of Br (Table1) for the 1257 eruption.
Volcanic-induced ozone depletion has been observed as a consequence of the 1991 Pinatubo eruption that caused
the destruction of 2–6% of global average total ozone46 due to the release of 3–16 Tg of Cl4 most of which was
scavenged by typhoon Yunya during the eruption. e combined Cl (51–675 Tg) and Br (0.1–1.5 Tg) emissions of
the Minoan eruption of Santorini (Greece) would have provoked reductions of 20 to > 90% of ozone at northern
high latitudes37. is strongly suggests that the 1257 Samalas eruption likely provoked strong ozone destruction,
even for the lower-bound 10%-injection scenario. is process is enhanced by the simultaneous emission of S, as
sulphate aerosols provide surface area for heterogeneous chemical reactions that activate Cl and Br species, thus
enabling and enhancing the catalytic destruction of ozone51,52.
Our study underscores the fundamental importance of considering magmatic systems in their totality as well
as the evolution of the behaviour of volatiles during magma dierentiation in order to signicantly improve the
quantication of the degassing budget of large climate-impacting explosive eruptions. e application of this
methodology to other magmatic systems that have produced volatile-rich intermediate magmas would enhance
the reconstruction of the climate impact of past volatile emissions associated to eruptions of large to moderate
volumes of S-rich magmas (e.g. 1815 Tambora53, 1835 Cosigüina54). Given the prodigious amounts of volatiles
released by the 1257 Samalas eruption, interactions between processes involving S, Cl and Br should be consid-
ered in future global scale climate-modelling. Although the probability of occurrence of such a large eruption
in the next decades is statistically low, the ozone-destruction power of volcanic eruptions in general should be
systematically assessed, particularly given that the Antarctic ozone-hole is decreasing43 and that stratospheric
halogen concentrations are expected to reach their pre-industrial level during the second half of the century.
Methods
Calculation details. Fraction of solid removal. We apply Rayleigh’s law to  concentrations ( is highly
incompatible) in basaltic and trachydacitic melts as
=×
−−
CCf
Th
preeruptive Th
basalt D1
Th , where
−
CTh
preeruptive
is the 
content of the 1257 system (9.0 ± 0.9 ppm),
CTh
basalt
is the  content of the basalt (1.7 ± 0.2 ppm), f is the propor-
tion of remaining melt, and the global partition coefficient of Th DTh is
1
. Equation is then simplified as
=
−
C
C
f
1
Th
preeruptive
Th
basalt . We calculate a proportion of trachydacitic melt f of 0.19 ± 0.03, i.e. a solid removal (1− f) of 0.81.
Water loss during in-situ crystallization of the 1257 trachydacite. e conservation of the ratio of water respective
to  during in-situ crystallization of the trachydacite is expressed as =
−
−
C
C
C
C
HO
Preeruptive
Th
preeruptive
HO
RM
Th
RM
22
. In-situ crystallization of
the 1257 trachydacite with 3.9 ± 0.1 wt% H2O and 9.0 ± 0.9 ppm  indicates a theoretical water content of
7.2 wt% in the residual melt (RM). e latter actually contains 3.7 ± 0.3 wt% H2O, suggesting the exsolution of
3.5 wt% of H2O.
Proportion of apatite. Using P2O5 concentrations of the 1257 trachydacite (0.42 ± 0.05 wt%; Supplementary
Table S3) and of the 1257 matrix glass (0.13 ± 0.06 wt%; Supplementary Table S3), we estimate a P2O5 loss Δ P2O5
of 0.6 ± 0.1 wt% due to apatite crystallization during in-situ crystallization. e proportion of P2O5 in apatite
X()
PO
apat
25
is given by =
∆
X
PO
apat PO
C
PO
apat
25
25
25
, where
CPO
apat
25
is the P2O5 content of apatite (42.9 ± 0.2 wt%; Supplementary
Table S5). We thus calculate a proportion of 0.015 ± 0.003 of apatite that would account for the removal of a max-
imum of 130 ppm of Cl from the melt.
Proportion of Fe-sulphides in the 1257 trachydacitic system. e proportion of iron-sulphide in the 1257 trachy-
dacite is derived from
=×+×CCXCX
S
WR
S
degassedRMRM
S
sulphide sulp hide
, where XRM is the residual melt fraction
(0.59), and
CS
sulphide
is the S content of Fe-sulphides (38.9 ± 0.5 wt%; Supplementary Table S4). is equation yields
a proportion of iron-sulphides Xsulphide of 0.01% in the 1257 trachydacite.
Mass of volatile released. e mass of volatile i released is calculated as mi = mmag ma × Δ i × 10−15, where 10−15
is the conversion factor of ppm into kg, and mmagma = ρm × V is 1.00 ± 0.08 × 1014 kg (DRE magma density ρm is
2500 kg/m3, DRE erupted volume V is 40 ± 3 km3 7).

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Sulphur uptake by poly-metallic sulphides. Using Cu concentrations of the basalt (114 ± 32 ppm; Supplementary
Table S3) and of the 1257 trachydacite (11.4 ± 0.8 ppm; Supplementary Table S3) derived through 81% of crystal-
lization, we calculate that 580 ppm of Cu (Δ Cu) were fractionated by Cu-bearing sulphides segregated during the
basalt dierentiation. e amount of associated S is given by =∆ ×
−−
SCu CC/
Cu Fe S
S
sulphide
Cu
sulphide
where
CS
sulphide
(32.1 ± 0.6 wt%) and
CCu
sulphide
(27.0 ± 1.1 wt%) are S and Cu contents in Cu-Fe sulphides, respectively
(Supplementary Table S4). is calculation yields an amount of 690 ± 225 ppm of S removed from the melt by
poly-metallic sulphides. is amount is considered as a maximum because we neglected the possible fractiona-
tion of Cu into the vapour phase.
Analysis of melt inclusions, matrix glasses and uid inclusions. Water and CO2 analysis. Melt
inclusions were analysed using a Thermo-Nicolet 6700 FTIR spectrometer coupled with an optical/IR
Spectra-Tech microscope (IPGP, France). Water and carbon concentrations were calculated using the
Beer-Lambert law (C(wt%) = 100 × A × M/(ε × ρ × e), where A is the absorbance, M the molar mass (g/mol), ε
the molar absorptivity (L/mol · cm), e the thickness (cm), and ρ the glass density in g/L). Melt inclusion densities
were calculated with the model of Lange and Carmichael (1987), using a partial molar volume of water of
12.0 ± 0.5 cm3/mol55. Dissolved total water concentrations (H2Omolec + OH−) were calculated using the broad
absorption band at 3550 cm−1 and absorption coecients of 62.8 L/mol · cm56 for basalt, and of 68.7 ± 1.0 L/
mol · cm57 for trachydacite. Carbon concentrations were determined using the 1515 cm−1
−
CO3
2
absorption band
aer subtraction of the background, previously acquired on a volatile-free basalt. Deconvolution of the carbonate
peaks taking into account the contribution of the 1630 cm−1 H2Omolecular band was performed using PEAK FIT
soware. e absorption coecient was calculated as ε1515 = 451 − 342 × Na/(Na + Ca)58. e analytical uncer-
tainties on CO2 and water concentrations were 17% and ≥ 10%, respectively. CO2 or carbonate ions were not
observed in trachydacitic melt inclusions.
Major element, S and Cl analysis. Major element concentrations in glasses and host minerals were measured
by electron probe micro-analysis (EPMA) using a Cameca SXFive electron probe (Camparis, Paris, France).
In melt inclusions they were measured with an accelerating voltage of 15 kV, a 4–10 nA defocused beam and
peak counting times of 10–30 s depending on the element. Sodium was measured rst with a 5 s peak count
time in order to minimise alkali loss. S, Cl and P concentrations were determined with a 30 nA defocused beam
and counting times of 120–200 s on peak. S speciation was investigated in these analytical conditions in a large
olivine-hosted melt inclusion of the dataset, by scanning the peak position for the wavelength of S Kα radiation
(λSKα)59. Accuracy of S and Cl measurements were ensured by analysis of KE12 (3332 ± 42 ppm Cl; 183 ± 6 ppm
S; N = 57), of the alkali trachyte CFA47 (5399 ± 175 ppm Cl; 67 ± 17 ppm S; N = 61), and of the international
standard Vg2 (291 ± 14 ppm Cl; 1435 ± 40 ppm S; N = 43). e analytical errors are ≤ 6% and 3% for S con-
centrations < 200 ppm and above 1400 ppm, respectively; 4% and ≤ 2% for Cl concentrations < 300 ppm and
> 3300 ppm, respectively. e detection limits were 55 ppm for S and 60 ppm for Cl.
Trace element analysis. Abundances of 30 traces elements (Ba, Ce, Co, Cu, Ni, Sc, V, Dy, Er, Eu, Gd, Hf, Ho, La,
Lu, Nb, Nd, Pb, Pr, Rb, Sm, Sr, Ta, Tb, , Tm, U, Y, Yb and Zr) were determined in melt inclusions by laser ablation
inductively coupled plasma mass spectrometry (LA-ICP-MS) at the Laboratoire Magmas et Volcans (Université
Blaise Pascal, Clermont-Ferrand, France), using a 193 nm ArF excimer laser ablation system (Resonetics M50)
coupled to a 7500 cs Agilent ICP-MS system, with helium as the ablation gas. Samples were analysed using a
laser repetition rate of 2 Hz, laser spot diameter range of 20–40 mm and pulse energy of 6 mJ (14 J/cm2).
e background was measured for 30 s before ablation, and each analysis lasted 100 s. Measurements were cal-
ibrated against NIST 612 glass standard60, using CaO as the internal element reference. Repeated analyses of
BCR2-G glass international standard for each spot size were reproducible within 1 to ≤ 5% RSD for most elements
and ≤ 7% RSD for Gd and some elements with low abundances such as Yb and Hf (< 5 ppm) and Tb, Tm, Lu and Ta
(< 1 ppm). Our measurements on BCR-2G standard were compared to published values (Supplementary Table S7).
Melt inclusions were analysed in single spot. Careful examination of counting statistics of each element and data
reduction was performed using the Glitter soware61.
Fluid inclusions characterisation. Plagioclase-hosted primary uid inclusions of the 1257 A.D. rocks were ana-
lysed by Raman microspectrometry at the Ecole Normale Supérieure, Paris (France). Spectra were acquired in
ambient conditions using a Renishaw INVIA spectrometer. is device is equipped with an Ar laser source giving
an incident beam with a 514.5 nm wavelength, focused through a Leica microscope. e Rayleigh scattering com-
ponent was removed by a Notch lter, and the Raman-scattered light was dispersed by a holographic grating with
1800 lines/mm and detected by a CCD camera. A power of 2 mW was used to avoid heating eects and sample
damage. Raman spectra were acquired between 200 and 3900 cm−1 in order to identify S-, CO2- and H2O- bearing
components of the uid phase.
Whole-rock analysis. Major and trace element analyses of whole-rock samples are reported in Métrich
et al. (in review). In this work, S and halogens (Cl, F and Br) were extracted by the pyrohydrolysis method62.
About 500 mg of powdered whole-rock mixed with ~500 mg of V2O5 in a platinum crucible was heated at 1200 °C
in a quartz combustion tube through a H2O-vapour stream transported by a nitrogen ux. e extracted S and
halogen species are converted into acids by hydrolysis in the H2O-vapour which was further condensed in a
cooling system. e condensate was collected in a vial containing 10 mL of a NaOH solution (25 mmol/L). e
vapour ux was adjusted in order to complete the extraction in 45–60 min and collect 80–100 ml of solution.
e dilution factors (masssolution/masssample) ranged from 180 to 250. Aer the complete extraction, the solutions
were immediately analysed (for Cl and F) by liquid chromatography using a Dionex DX120 ion chromatograph

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Scientific RepoRts | 6:34868 | DOI: 10.1038/srep34868
(IC) with an Ion Pac AS9-HC (Dionex) anionic column, performed in suppression mode (ASRS-UltraII). e
detection limit was 100 μg/L for both F and Cl in the sample solution. Solution concentrations were calculated
using a calibration curve (0–50 ppm), and were further converted into rock concentrations using the dilution
factor. Taking into account the mean dilution factor, detection limits in rock samples were 15 to 20 mg/kg for
both elements. Br contents were determined using a 7900 Agilent ICP-MS device, in low resolution with a Scott
spray chamber and a micro nebulizer (0.2 ml/min). Br was analysed in the ‘no gas’ mode, with an acquisition time
of 0.3 sec, measuring 5 points as peak pattern, 3 replicates and 100 sweeps by replicates, 70 sec for the uptake,
40 sec as stabilisation time and 60 sec for rinsing time. Br solution concentrations were further calculated using
a calibration curve (0–50 ppb), and were further converted into rock concentrations using the dilution factor.
To ensure a complete extraction and the accuracy of the analyses, pyrohydrolysis/IC/ICP-MS was performed on
international standards covering a wide compositional range and S, Cl, Br and F concentrations. We stress that
our results were reproducible within 1–10% RSD for Cl, within 6–16% RSD for Br, and within 2–16% RSD for
S except for AGV-1 (35% RSD). e ecient extraction of S from sulphide-bearing samples was guaranteed by
the analysis of a sulde-bearing syenite standard SY-2. Our results compared to published reference values are
reported in Supplementary Table S8.
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Acknowledgements
We thank the Indonesian Ministry of Research an Technology RISTEK and the Nusa Tengara Barat Governor’s
Oce, M. Hendrasto (CVGHM), Surono (Badan Geologi) and J.-P. Toutain (IRD) for their permission to conduct
eldwork and administrative support. We also thank H. Rachmat, Muntaharlin and J.-P. Degeai for providing
additional samples. We thank M. Fialin, N. Rividi, J.-L. Devidal, D. Deldicque and V. Zanon for dedicated
assistance during EPMA, LA-ICP-MS and Raman analyses. 14C dates were obtained by C. Moreau and J.-P.
Dumoulin (LMC14, CNRS UMS2572). SRTM data was provided by CIAT-CSI. is study was partly funded by
INSU-CNRS CT3-ALEA projects ECRin I and II and INSU-CNRS Artemis 2014 for 14C dating in the framework
of C.M. Vidal PhD’s thesis. is is IPGP contribution 3754.
Author Contributions
C.M.V., N.M. and J.-C.K. conducted fieldwork, sampling, sample preparation and analysis, interpreted the
results, performed degassing budget calculations and co-wrote the manuscript and co-draed the gures. A.M.
conceived and conducted the pyrohydrolysis/IC/ICP-MS analyses. I.P., N.K., V.R. and F.L. conducted eldwork
and sampling. All authors reviewed the manuscript.
Additional Information
Supplementary information accompanies this paper at http://www.nature.com/srep
Competing nancial interests: e authors declare no competing nancial interests.
How to cite this article: Vidal, C. M. et al. e 1257 Samalas eruption (Lombok, Indonesia): the single greatest
stratospheric gas release of the Common Era. Sci. Rep. 6, 34868; doi: 10.1038/srep34868 (2016).
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