investigating magma plumbing beneath anak krakatau volcano

Examensarbete vid Institutionen för geovetenskaper ISSN 1650-6553 Nr 193

Investigating Magma Plumbing Beneath Anak Krakatau Volcano, Indonesia: Evidence for Multiple

Magma Storage Regions

Börje Dahrén

iii

Referat

Att öka förståelsen för transport och lagring av magma är en stor utmaning för petrologer och

vulkanologer. Detta gäller speciellt för explosiva vulkaner, där förståelsen av magma-

lagringssystem är mycket viktig för att förutse dynamiska förändringar och därigenom också i

riskförebyggande arbete. Denna studie syftar till att undersöka magma-lagringssystemet vid

Anak Krakatau, den aktiva vulkanen som befinner sig på kanten av kalderan från Krakataus

förödande utbrott år 1883. För detta ändamål tillämpas a.) klinopyroxen-smälta

termobarometri (Putirka et al., 2003; Putirka, 2008), b.) plagioklas-smälta termobarometri

(Putirka, 2005; Putirka, 2008), c.) klinopyroxen-barometri (Nimis & Ulmer, 1998; Nimis,

1999; Putirka, 2008) samt d.) olivin-smälta termometri (Putirka et al., 2007). Tidigare

seismiska (Harjono et al., 1989) och petrologiska (Camus et al., 1987; Mandeville et al.,

1996a; Gardner et al., under granskning, J. Petrol.) studier har undersökt denna frågeställning.

De petrologiska studierna påvisar ytligt förvar av magma, vid ett djup av 2-8 km. Den

seismiska studien, å andra sidan, identifierade två områden med magmalagring, på djup av ~9

respektive ≥22 km.

Denna studie visar att klinopyroxen för närvarande kristalliserar i mitt i jordskorpan under

Anak Krakatau (8-12 km), en nivå tidigare identifierad av seismiska undersökningar (Harjono

et al., 1989). Plagioklas visar på ett ytligare förvar (4-6 km), vilket överenstämmer med

tidigare petrologiska undersökningar (Camus et al., 1987; Mandeville et al., 1996a; Gardner et

al., under granskning, J. Petrol.). Klinopyroxen äldre än 1981 uppvisar större

kristallisationsdjup (8-22 km), vilket antyder att magma-förvaringssystemet närmat sig ytan

under de senaste ~40 åren. Dessutom sammanfaller de identifierade djupen för lagring av

magma med de dominerande litologiska gränserna i skorpan, vilket indikerar att lagringen

styrs av diskontinuiteter och densitetsskillnader i skorpan. Denna studie visar således att

petrologiska metoder är tillräckligt känsliga för att identifiera magma-lagringsnivåer, även där

seismiska metoder misslyckas på grund av begränsningar i upplösning. Kombinerade

seismiska och petrologiska studier har därför högre potential att uppnå en mer komplett

karaktärisering av magma-lagringssystem vid aktiva vulkaniska komplex.

Nyckelord:

Anak Krakatau; termobarometri; magma-lagringssystem; klinopyroxen; plagioklas.

iv

Abstract

Improving our understanding of magma plumbing and storage remains one of the major

challenges for petrologists and volcanologists today. This is especially true for explosive

volcanoes, where constraints on magma plumbing are essential for predicting dynamic

changes in future activity and thus for hazard mitigation. This study aims to investigate the

magma plumbing system at Anak Krakatau; the post-collapse cone situated on the rim of the

1883 Krakatau caldera. Since 1927, Anak Krakatau has been highly active, growing at a rate

of ~8 cm/week. The methods employed are a.) clinopyroxene-melt thermo-barometry (Putirka

et al., 2003; Putirka, 2008), b.) plagioclase-melt thermo-barometry (Putirka, 2005), c.)

clinopyroxene composition barometry (Nimis & and Ulmer, 1998; Nimis, 1999; Putirka,

2008) and d.) olivine-melt thermometry (Putirka et al., 2007). Previously, both seismic

(Harjono et al., 1989) and petrological studies (Camus et al., 1987; Mandeville et al., 1996a;

Gardner et al., in review, J. Petrol.) have addressed the magma plumbing beneath Anak

Krakatau. Interestingly, petrological studies indicate shallow magma storage in the region of

2-8 km, while the seismic evidence points towards a mid-crustal and a deep storage, at 9 and

22 km respectively.

This study shows that clinopyroxene presently crystallizes in a mid-crustal storage region

(8-12 km), a previously identified depth level for magma storage, using seismic methods

(Harjono et al., 1989). Plagioclases, in turn, form at shallower depths (4-6 km), in concert

with previous petrological studies (Camus et al., 1987; Mandeville et al., 1996a; Gardner et

al., in review, J. Petrol.). Pre-1981 clinopyroxenes record deeper levels of storage (8-22 km),

indicating that there may have been an overall shallowing of the plumbing system over the

last ~40 years. The magma storage regions detected coincide with major lithological

boundaries in the crust, implying that magma ascent and storage at Anak Krakatau is probably

controlled by crustal discontinuities and/or density contrasts. Therefore, this study shows that

petrology has the sensitivity to detect magma bodies in the crust where seismic surveys fail

due to limited resolution. Combined geophysical and petrological surveys offer an increased

potential for the thorough characterization of magma plumbing at active volcanic complexes.

Keywords

Anak Krakatau; thermobarometry; magma plumbing; clinopyroxene; plagioclase.

v

Table of Contents

1. Introduction ........................................................................................................................ 1

2. Field work........................................................................................................................... 2

3. Geotectonic setting ............................................................................................................. 5

4. Previous estimates of magma storage depth ....................................................................... 9

5. Bulk rock geochemistry.................................................................................................... 11

6. Analytical method ............................................................................................................ 14

7. Petrography and mineral chemistry .................................................................................. 15

7.1 Plagioclase phenocrysts .............................................................................................. 15

7.2 Clinopyroxene phenocrysts ........................................................................................ 18

7.3 Olivine ........................................................................................................................ 19

7.4 Groundmass ................................................................................................................ 20

8. Estimates of bedrock density and pre-eruptive volatile content ....................................... 21

9. Method.............................................................................................................................. 22

9.1 Clinopyroxene-melt thermo-barometers .................................................................... 22

9.2 Clinopyroxene barometers ......................................................................................... 23

9.3 Plagioclase-melt thermobarometers ........................................................................... 24

9.4 Olivine-melt thermometers ........................................................................................ 24

10. Results ............................................................................................................................ 26

10.1 Pressures and temperatures from clinopyroxene-melt thermobarometry ................ 26

vi

10.2 Pressure estimates from clinopyroxene barometry .................................................. 29

10.3 Pressures and temperatures from plagioclase-melt thermobarometry ..................... 30

10.4 Temperature estimates from olivine-melt thermometry ........................................... 31

11. Discussion ...................................................................................................................... 34

12. Conclusions .................................................................................................................... 39

References ............................................................................................................................ 41

Appendix 1 – Chemical composition of analysed clinopyroxene phenocrysts ........................ 46

Appendix 2 – Chemical composition of analysed plagioclase phenocrysts ............................. 50

Appendix 3 – Chemical composition of analysed olivine ........................................................ 53

Appendix 4 – Chemical composition of analysed orthopyroxene ........................................... 54

Appendix 5 – Chemical composition of analysed titanomagnetite .......................................... 55

Appendix 6 – Chemical composition of analysed glass and groundmass ................................ 56

1

1. Introduction

The Krakatau volcano complex, western Java (Indonesia), is one of the most infamous

volcanoes worldwide due to the cataclysmic eruption of 1883, being the latest in a sequence

of caldera forming events (van Bemmelen, 1949; Camus et al., 1987). In 1927, a new volcanic

cone breached the ocean surface, earning the name Anak Krakatau, “child of Krakatau”. The

aim of this investigation is to constrain the depth of magma storage region(s) beneath Anak

Krakatau, which is approached by employing pressure and temperature modelling calculations

that use measured mineral and rock composition data and calibrated thermodynamic

formulations. The focus will be on a.) clinopyroxene-melt thermo-barometry (Putirka et al.,

2003; Putirka, 2008), and b.) plagioclase-melt thermo-barometry (Putirka, 2005). This will be

complemented by a.) clinopyroxene composition barometry (Nimis, 1999; Putirka, 2008) and

b.) olivine-melt thermometry (Putirka et al., 2007). The mineral dataset consists of electron

microprobe (EPMA) and X-ray fluorescence (XRF) analyses of minerals and rocks erupted

between 1883 and 2002. The results will serve as an independent test of previous estimates of

magma storage depths derived by geophysical means, plagioclase-melt geobarometry and in-

situ isotope stratigraphy (Camus et al., 1987; Harjono et al., 1989; Mandeville et al., 1996a;

Gardner et al., in review, J. Petrol.). Improved knowledge of the magma plumbing system

beneath Anak Krakatau will allow for better understanding and prediction of future activity at

this highly dynamic volcanic complex.

2

2. Field work

In September and October 2008, field work was carried out on the Indonesian islands of Java

and Bali, to sample rocks and fumarole gases at 16 active volcanoes. The expedition was part

of a project funded by Vetenskapsrådet and Uppsala University. Also, my participation on the

trip was made possible by additional funding from Otterborgs donationsfond.

See Fig. 1 map of the field area. According to the Global Volcanism Program, run by the

Smithsonian Institute, Krakatau was more or less active between October 2007 and October

2009. Our visit, however, took place during a period of relative quiescence. Notably, a new

crater formed in 2007, situated on the southern flank, just below the old summit crater (Fig.

2). Although no eruptions took place during our visit of Anak Krakatau, the evidence of

recent eruptions were abundant. The southern flank below the newly formed crater was

covered in volcanic ash, and was devoid of vegetation. Volcanic bombs of varying size, with

fresh bomb sags (Fig. 3) were scattered around the volcanic cone, especially on the terrace on

the eastern flank (Fig. 2). See Fig. 2-7 below for pictures taken during the expedition.

Figure 1. Map of the Sunda Straits, after Gardner et al. (in review, J. Petrol.). The location of the other volcanoes in

the north-south trending volcanic lineament is marked with triangles. Inset (b) is a close up on the Krakatau complex,

the dashed line indicating the outline of the pre-1883 Krakatau island.

3

Figure 2. The southern flank of Anak Krakatau. Visible is the 1960’s crater rim (black), the pre-2007 summit

crater (blue), as well as the currently active crater (red).

Figure 3. Picture taken on the terrace

on the eastern flank (visible in Fig. 2),

just below the main active cone. This

area was strewn with countless

volcanic bombs, ranging in size from

centimetres to several meters in

diameter. Many of the bombs had

fresh bomb sags implying that they

were recently erupted. This

particular bomb was erupted in late

2001/early 2002. In the bottom right

corner, one can see destroyed solar

panel, associated with the KrakMon

surveillance system operating on the

Krakatau islands.

Figure 4. A view from inside the

active Anak Krakatau crater. Note

the fumaroles on the far crater wall.

Other fumaroles, located in the

summit crater, were sampled to be

used in other studies (e.g. Blythe et

al., 2009).

4

Figure 5. A view from the top of Anak

Krakatau towards Rakata (Fig. 1), one

of the three islets remaining after the

collapse of the old Krakatau island in

1883.

Figure 6. A part of the 1883 caldera

wall on the island of Rakata. In other

words this is a view inside the pre-1883

Krakatau volcano (approximately in the

centre of Fig. 5). Below the volcanic

rocks, one can see the top of a sequence

of what is likely sedimentary rocks,

and/or pyroclastic deposits. Note also

the dyke swarm cutting trough the

rocks of the old Krakatau edifice.

Figure 7. View from beach of Rakata,

were the expedition spent the night

after the excursion to Anak Krakatau.

The boat in the middle left of the image

was used for transportation from the

mainland

5

3. Geotectonic setting

Anak Krakatau (Anak) is located in the Sunda Strait between the Indonesian islands of

Sumatra and Java (Fig. 1). Geologically, Anak is a part of the Sunda arc where the Indo-

Australian plate is subducted beneath the Eurasian plate. In west Java, this occurs at a rate of

67±7 mm per year (Tregoning et al., 1994). The Sunda arc is an active volcanic region with

the Krakatau complex being one of the most active parts. Since 1927, Anak has had numerous

eruptions, and has grown to a height of ~315m (Hoffmann-Rothe et al., 2006), which converts

to an average of 8 cm per week. Anak is a part of a volcanic lineament (Nishimura &

Harjono, 1992), with Panaitan to the south and Sukadana to the north (Fig. 1). This lineament

is related to a north-south trending fracture zone, manifested in a shallow seismic belt with

foci depths predominantly in the range of 0-20 km (Harjono et al., 1989; Nishimura &

Harjono, 1992; Špičák et al., 2002). Furthermore, the Krakatau complex is located at the

intersection of the volcanic lineament and a fault (Nishimura & Harjono, 1992; Deplus et al.,

1995), both of which would contribute to a heavily fractured bedrock facilitating magma

transport. The projection of this fault is seen in the bathymetric map (Deplus et al., 1995), as

indicated by the depressions labeled B and C (Fig. 8). The whole of the Sunda Strait is

subjected to extensive faulting and rifting, attributed to the clockwise rotation of Sumatra

relative to Java by 20° during the late Cenozoic (Ninkovich, 1976; Nishimura et al., 1986;

Harjono et al., 1991). The angle of subduction changes from near perpendicular (13°) in front

of Java to oblique (55°) in front of Sumatra (Jarrard, 1986). The Sumatran rotation has

resulted in extension, as reported in Harjono et al. (1991) and associated thinning of the crust

to ~20 km in the Sunda Strait, as compared to 25-30 km in Sumatra and west Java (Nishimura

& Harjono, 1992). The micro-seismic study by Harjono et al. (1989) estimated the crustal

thickness directly below Anak Krakatau to be ~22 km. The magmatism in the Sunda Strait is

thus not strictly subduction zone related, but must also be considered to be to some degree

extensional. The influence of the rifting is manifested in Sukadana (Fig. 1), where an 0.8-1.2

Ma old MORB-type basalt is found (Nishimura & Harjono, 1992).

The bimodal nature of the Krakatau complex, with extended periods of basaltic and/or

basaltic-andesitic eruptions culminating in colossal caldera forming ignimbrite eruptions (Fig.

9), was discussed by Van Bemmelen (1949), and has since been strengthened by findings of

other authors (Camus et al., 1987; Mandeville et al., 1996a).

6

The formation of the most recent caldera occurred on the 23rd

of August 1883, when the

Krakatau island collapsed (Mandeville et al., 1996). This resulted in a submarine caldera ~100

m deeper than the surrounding sea floor (Fig. 8). Note also that Anak is situated on the north-

eastern rim of this caldera. The volume of products of the 1883 eruption has been estimated to

be 17-25 km3 (Deplus et al., 1995), ~20 km

3 (Rampino & Self, 1982) or 12.5 km

3 (Mandeville

et al., 1996a). There is evidence of at least two more large ignimbrite eruptions at Krakatau.

Ninkovich, (1979) located two major dacitic ashfalls near the trench ~350 km south and

southwest of Krakatau, which he associated with Krakatau and attributed to 60,000 BC and

“recent”. The “recent” ashfall has not been radiometrically dated. However, two estimates,

from correlations with historical documents are suggested in the literature, namely 416 AD

(Camus et al., 1987) and 535 AD (Wohletz, 2000).

Figure 1. Bathymetric map

(Deplus et al., 1995) of the

Krakatau complex. Isolines

indicate 20 m contours. The

depression labeled “A” is the

~240 m deep caldera from the

1883 eruption. Note the

location of Anak Krakatau on

the north-eastern rim of the

caldera. The east-west trending

fault intersecting the volcanic

lineament is visible as the

depressions labeled “B” and

“C”.

Figure 2. The bimodal cyclicity of Krakatau, as reported in van Bemmelen (1949). The composition of the present day

eruption products are still dominated by basaltic-andesites (~55 wt% SiO2).

7

Drill cores obtained during hydrocarbon exploration by Pertamina-Aminoil provides

information on the bedrock at depth in the Sunda Strait. The closest of these wells (C-1SX) is

located ~30 km southeast of Anak (Fig. 1). The C-1SX well penetrated a continuous

sedimentary sequence of Quaternary to upper Pliocene age. The lithology is dominated by

marine clays and clay-dominated siliciclastic rocks interbedded with volcanoclastic material

to a depth of at least 3000 m (Nishimura & Harjono, 1992; Mandeville et al., 1996a).

Findings by (Lelgemann et al., 2000) suggest that the extension and rapid subsidence of the

Sunda Strait have created space for up to 6 km graben fill. Thus, the total depth of the

sediments and sedimentary rocks below Krakatau can be constrained to between 3 to 6 km.

The Pertamina-Aminoil wells all failed to reach the basement below the sedimentary

sequence, but other wells to the southeast of Sumatra and northwest of Java have drilled

Cretaceous granites and quartz-monzonites (Hamilton, 1979). The assumption of a

sedimentary sequence

underlain by a plutonic

basement below

Krakatau (Harjono et

al., 1991) is supported

by the findings of

sedimentary

(Mandeville et al.,

1996b; Gardner et al., in

review, J. Petrol.),

granitic (Oba et al.,

1983) as well as dioritic,

gabbroic and meta-basic

(Oba et al., 1983;

Gardner et al., in

review, J. Petrol.)

xenoliths in Krakatau

lavas and pyroclastic

flows. The crustal

velocity model used in

the micro-seismic study

Figure 3. Stratigraphy of the bedrock below Anak Krakatau. The lithology is

inferred from findings of xenoliths (Oba et al., 1983; Camus et al., 1987;

Mandeville et al., 1996b; Gardner et al., in review, J. Petrol.) and seismic

studies (Harjono et al., 1989; Kopp et al., 2001).

8

by Harjono et al. (1989) identifies three boundaries in the crust below Krakatau with

distinguishable crustal velocities, which could correspond with lithological boundaries. These

boundaries would be at depths of roughly 4, 9 and 22 km respectively, with the lowermost

boundary representing the Moho. The upper boundary (4 km) very likely represent the

sedimentary-plutonic crustal boundary. The middle boundary (9 km) represent a density

contrast, possibly caused by a change in lithology from a light density plutonic rock (e.g.

granite) to a higher density plutonic rock (e.g. diorite or gabbro). See Fig. 10 for a schematic

stratigraphy of the bedrock below Anak Krakatau.

9

4. Previous estimates of magma storage depth

The methods previously employed to estimate magma storage depth beneath Krakatau are a.)

plagioclase-melt thermobarometry, b.) chlorine content in melt inclusions, c.) loci of seismic

attenuation zones, and d.) in-situ crystal isotope stratigraphy. The results of these studies will

be outlined below.

Mandeville et al. (1996a)

employed plagioclase-melt

thermobarometry (Housh & Luhr,

1991) to estimate the depth of the

pre-1883 magma chamber. Their

results indicate shallow depths of

crystallization for plagioclase, with

pressure estimates in the range of 1

to 2 kbar (~4 to 8 km). This was

complemented by analysing

chlorine content in melt inclusions

(Metrich & Rutherford, 1992),

resulting in an independent

estimate of 1 kbar (~4 km).

Camus et al. (1987) estimated

depth of crystallization for

plagioclase in rocks erupted

between 1883 and 1981, using

plagioclase-melt thermobarometry (Kudo & and Weill, 1970), resulting in estimates of 0.5 to

2 kbar (~2 to 8 km).

Gardner et al. (in review, J. Petrol.) have carried out in situ 87

Sr/86

Sr analyses on

plagioclase from the 2002 eruptions, employing LA-ICPMS, and conclude that crystallization

of many plagioclase grains must have taken place during assimilation of sedimentary country-

rock. This constrains the depth of final crystallization to within the upper three or four

kilometres simply on stratigraphic grounds - from drill hole evidence - in agreement with the

plagioclase-melt thermobarometry results discussed above.

Harjono et al. (1989) analysed the seismic signature from 14 earthquakes near Anak

Krakatau during 1984, using data from analogue seismograms. Two seismic attenuation zones

Figure 11. The two seismic attenuation zones detected below Anak

Krakatau, redrawn from Harjono et al. (1989). Circles represent

earthquake foci with (open circles) and without (filled circles) S-

wave attenuation. The inferred magma storage regions are

represented by the red shapes. Note that the resolution in this

study is too low to conclude whether or not the two attenuation

zones are connected.

10

beneath the volcanic edifice were identified in that study, one a small and irregular zone at a

depth of approximately 9 km, and another much larger one at 22 km (Fig. 11). Note that the

seismic attenuation zones coincide with the lower boundary of the medium and lower crustal

velocity zones discussed above. However, it was not possible to resolve whether the two

attenuation zones are connected or not, nor if these represent large volume chambers or a

plexus of smaller pockets and chambers.

The present study uses, for the first time, barometry based on clinopyroxene, to provide an

independent and complementary test to these isotopic, geophysical and geobarometric

constraints, with the aim to establish a model of the plumbing system beneath Anak Krakatau.

11

5. Bulk rock geochemistry

Bulk rock chemistry of flows, bombs and ash erupted from Krakatau and Anak is plotted in

Fig. 12. The bulk rock data was supplied by Mairi Gardner, a final year PhD student at

University College Cork, Ireland, who works with Prof. Troll on other aspects of Anak

(Gardner et al., in review, J. Petrol.), or otherwise taken from the literature (Zen &

Hadikusumo, 1964; Self, 1982; Camus et al., 1987; Mandeville et al., 1996a). All oxides have

been normalized to 100%, (volatile free) and iron content is reported as FeOt. Note that the

bulk rock analyses of lava flows and bombs erupted between 1990 and 2002 carried out by

Gardner et al. (in review, J. Petrol.), were done on the exact same samples that were used for

the petrographic and microprobe analyses in this study. Analyses of rocks erupted during the

1883 eruption as well as the time period 1960-1981 are also plotted in Fig. 12. Note that, in

the TAS diagram (Le Bas et al., 1986) below, all Krakatau rocks plot in the subalkaline field

(Fig. 12).

Figure 12. TAS diagram (Le Bas et al., 1986) plotting bulk composition of rocks from Anak Krakatau (black circles)

and Krakatau (red circles). The data was taken from the literature. (Zen & Hadikusumo, 1964; Self, 1982; Camus et

al., 1987; Mandeville et al., 1996a; Gardner et al., in review, J. Petrol.). The Krakatau rocks include products from

the ignimbrite eruption in 1883 as well as older basaltic dyke rocks. The vast majority of the rocks erupted from Anak

Krakatau plot in a very narrow region in the basaltic-andesite field, with rocks from single events plotting in the

basaltic and andesitic fields.

12

Using the classification of Peccerillo and Taylor (1976), the rock suite plots mostly within

the medium-K part of the calc-alkaline series (Fig. 13), in concert with the findings of other

authors (Camus et al., 1987). Note, however, that when using the definition of Peacock

(1931), the rock suite would be classified as calcic rather than calc-alkaline, with an alkali

lime index of 61.6.

Figure 43. K2O vs SiO2 plot (Peccerillo & Taylor, 1976) for rocks from Anak Krakatau (black circles) and Krakatau (red

circles). Except for two of the basaltic dyke rocks from pre-1883, all rocks plot within the calc-alkaline series, and there

almost exclusively within the medium-K part.

The rocks plot in two main groups on a TAS diagram. The pumices and obsidians of the

1883 eruption plot in the dacite-rhyolite field, while the lava flows and bombs from Anak

belong to a rather homogenous suite of basaltic-andesites. The exceptions to this would be the

1960-1963 and 1981 eruptions (basalts and acidic-andesites, respectively), representing single

events. Note also that several basaltic dyke rocks from the island of Rakata with a similar

composition to the 1963 basaltic flows have been reported (Camus et al., 1987). The early

history of Anak is not well documented, as very few analyses have been performed on rocks

0

1

2

3

4

48 53 58 63 68

Arc tholeiite series

Calc-alkaline series

High-Kcalc-alkaline series

Shoshonite series

SiO2

K2O

13

erupted between 1927 and 1960. However, there are indications that the early Anak rocks did

not differ significantly from the more recent ones, as silica content in ashes and bombs

erupted in the period 1928-1935 has been reported to be in the range of 51.81 to 54.76 wt. %

(van Bemmelen, 1949), overlapping with the SiO2 content of the recent basaltic-andesites

(Fig. 12). This corresponds well with the observation of Camus et al. (1987), that the

composition of the tuff ring and lava flows on Anak appeared to belong invariably to the

basaltic-andesite suite. Field observations in 2008 also support this as the lava bombs of the

2007-2008 eruptions appear to be virtually identical in composition to the 2002 bombs. Thus,

all bulk rock analyses and field observations indicate that the bulk of Anak Krakatau island is

made up of basaltic-andesites, with minor components of basalt plus sparse acidic-andesite.

This suggests the presence of a steady state magma storage system under the volcano,

presently producing basaltic-andesite from parental basalt with limited variation of the final

product.

14

6. Analytical method

Mineral chemistry as well as glass and groundmass composition was analysed at Uppsala

University (Sweden) using a Cameca SX 50 Electron Probe Microanalyser (EPMA), equipped

with three crystal spectrometers (WDS), secondary (SE) and backscattered electron detectors

(BSE). The EPMA is an advanced microchemical instrument that is used to determine the

chemical composition of e.g. mineral samples. The sample, prepared as a thin section, is

beamed with high energy electrons with an accelerating voltage of 20 kV and a current of 15

nA, causing the sample to emit characteristic X-ray signatures, allowing the determination of

chemical composition. The electron beam is focused using several electromagnetic lenses.

The diameter of the beam is commonly 1-2 µm, though a beam size of up to 25 µm was used

for the analysis of groundmass composition. The wide beam analyses of groundmass included

glass and microcrysts, but avoided phenocrysts. Glass compositions were analysed both in the

groundmass and in melt inclusions. International reference materials were used for calibration

and standardisation (e.g. Andersson, 1997).

Figure 14. Schematic illustration of an Electron Probe Microanalyser (EPMA).

Image adopted from Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover

(www.bgr.bund.de)

15

7. Petrography and mineral chemistry

The lavas examined are all highly porphyritic, dark, and partly vesicular. Plutonic as well as

sedimentary xenoliths occur. The homogeneity of the bulk chemistry of the rocks is reflected

in the petrographic features, as all thin sections examined share the same characteristics,

outlined below. The analysed dataset consists of 152 clinopyroxene, 121 plagioclase, 19

olivine, 26 orthopyroxene and 4 titanomagnetite spot analyses where collected from 15

clinopyroxene, 12 plagioclase, 4 olivine and 4 titanomagnetite mineral grains. The relatively

small number of analysed minerals was considered adequate due to the relatively homogenous

mineral chemistry, especially regarding clinopyroxene. Also, 14 analyses of glass in

groundmass and melt inclusions where collected as well as another 14 wide beam (~10x10

µm) analyses of groundmass, in order to be able to calculate an average groundmass

composition including both glass and microcrystalline phases. Mineral chemistry of

clinopyroxene from Mandeville et al. (1996) and Camus et al. (1987) will be included in the

model calculations in order to increase the temporal resolution of the data set. The modal

composition is, on average, 70% groundmass, 25% plagioclase, 4% clinopyroxene and less

than 1% olivine crystals, as determined from point counting (4 thin sections, 144 points each).

These mineral phases will be outlined below. Representative microphotographs and electron

backscatter images of the rocks analysed are displayed in Fig. 15.

7.1 Plagioclase phenocrysts

Plagioclase is the volumetrically dominant phenocryst phase, making up approximately one

fourth of the total rock volume. Plagioclase phenocrysts are mostly subhedral, but a few are

anhedral. Sieve-like textures are a common feature with numerous melt inclusions present.

The size of the plagioclase crystals are on the order of 0.5-2 mm. Numerous plagioclase

crystals, when viewed under polarized light, appear to have experienced stages of growth

and/or dissolution, as shown by cores that have been partially resorbed at some point before

growth re-commenced (Fig 13a, 13d). Normal as well as reverse zoning has been

documented.

16

Figure 15a. Subhedral plagioclase crystal with highly

sieve-textured core and rim regions. This implies a

dynamic magmatic system. Crossed polars.

Figure 15b. Sieve-textured plagioclase crystal with

numerous melt inclusions. Crossed polars. Note also the

very thin overgrowth rim.

Figure 15c. Several intergrown anhedral plagioclase

crystals, all with a sieve-texture. Crossed polars.

Figure 15d. Plagioclase crystal. Note that the

anomalously dark brown colour of the plagioclase is due

to the thin section being thicker than normal (~100 µm).

The outer regions are sieve-textured with a very thin

overgrowth of the rims, just like the plagioclase in Fig.

15b. Crossed polars

Figure 15e. A plagioclase crystal with sieve-like texture,

having grown around several small clinopyroxenes.

Again, note the sieve-texture and the thin overgrowth on

the rims. Crossed polars.

Figure 15f. A plagioclase crystal intergrown with several

smaller clinopyroxene crystals. Crossed polars.

17

Figure 15g. Euhedral clinopyroxene crystal. Dark brown,

vesicular groundmass consisting of acicular plagioclase,

orthopyroxene, titanomagnetite and glass. Crossed

polars.

Figure 15h. Euhedral clinopyroxene crystal. Crossed

polars.

Figure 15i. Euhedral, clinopyroxene crystal. Crossed

polars.

Figure 15j. Euhedral, twinned clinopyroxene crystal. In

the bottom left corner, there is a tiny, partly resorbed

olivine with very high colours. Note that the olivine rim is

covered in discontinuous phases, as can also be seen in

Fig. 15k below. Crossed polars.

Figure 15k. BSE image of a partly resorbed olivine

(center of image), covered in discontinuous growth of

orthopyroxene and titanomagnetite. The olivine crystal is

surrounded by the groundmass composed of acicular

plagioclase (dark grey laths), anhedral orthopyroxene

(light grey), titanomagnetite (white crystals) and glass

(irregular dark grey fields).

Figure 15l. BSE image. Intergrown plagioclase (bottom)

and clinopyroxene (top). Note the abundance of melt

inclusions and vesicles in the plagioclase. The

clinopyroxene have several inclusions of opaque

minerals, likely titanomagnetite.

18

The lowest anorthite

concentrations (An45) as

well as the highest

(An80) were found in

plagioclase cores. The

rims do also vary

widely in their

composition, with

extremes of An79 and

An55. It is noteworthy

that the An% variation

between different grains

is often greater than

within individual grains. Although the number of analysed individual grains (n=12) is

insufficient to distinguish between different plagioclase generations, there seems to be two

main groupings, in the range of An45-70 and An58-80 respectively. Other authors have

independently reached similar conclusions, finding two plagioclase populations in Anak

Krakatau lavas of An55-60 and An75-90 (Gardner et al., in review, J. Petrol.) and An40-55 and

An75-90 (Camus et al., 1987). The composition of all plagioclase datapoints analysed for this

study is illustrated in Fig. 16.

7.2 Clinopyroxene phenocrysts

Clinopyroxene is the second most abundant mineral phase, though markedly less common

than plagioclase, making up approximately 4% of the total rock volume. The clinopyroxene

crystals are, with few exceptions, euhedral. Most grains have melt inclusions, though

considerably fewer than found in plagioclase. The clinopyroxene crystals are slightly smaller

than plagioclase, in the region of 0.2-1.0 mm. Also, it is common to find plagioclase that has

grown around clinopyroxene, implying that the main phase of plagioclase growth occurred

after clinopyroxene crystallization, the two mineral phases may thus possibly record different

levels of magma storage and crystallisation.

The overall composition of pyroxenes, in terms of the endmember mineral components as

defined by (Morimoto et al., 1988), is plotted in Fig. 17. It is apparent that all the

Figure 16. Composition of all analyzed plagioclase crystals (n=121).

Composition of plagioclase varies between An45 and An80.

19

clinopyroxenes belong to the same compositional family. Therefore, the average composition

of each individual clinopyroxene grain was calculated, which will be used in the

thermobarometric model calculations. Note also that the core-rim variations are minor and

unsystematic, though a tendency of normal zoning towards slightly Fe-richer rims is often

observed. However, the opposite has also been found in a few grains. This would indicate that

the clinopyroxenes are close to equilibrium with the basaltic-andesite host rock. Interestingly,

Camus et al. (1987) noted that the variation in composition of the clinopyroxenes found in the

1981 acid-andesites relative to the ones in the earlier basaltic-andesites does not differ

significantly, implying a common source region for the clinopyroxenes, despite the

differences in bulk chemistry between the eruptions. Moreover, in terms of major elements,

the composition of the recent (1990-2002) and the old (1883-1981) clinopyroxenes is very

similar. There is, however, one notable distinction between the two, namely the Na2O

component. The clinopyroxenes from the recent eruptions have Na2O contents of 0.20 ± 0.06

(n=152, range = 0.042-0.40, 1 std), which contrasts the older clinopyroxenes that fall between

0.31-0.50 % (n=15). Although

Na2O is a minor component in

clinopyroxene, this is an

interesting distinction, as the

jadeite (NaAlSi2O6) component

of clinopyroxene is supposed to

increase (under equilibrium)

with increasing pressure under

which the melt has crystallised

(Putirka et al., 1996; 2003;

Putirka, 2008). This implies that

the older rocks may have formed

at a deeper level than the recent

ones.

7.3 Olivine

Olivine is rather uncommon (<1 wt. %) and has not been identified in all thin sections. The

olivines found are very small, with diameters in the order of 0.02 to 0.15 mm, and are best

Figure 17. Composition of clinopyroxenes (filled circles, n=168) and

orthopyroxenes (open circles, n=26). The clinopyroxene dataset

include composition of minerals analyzed for this study (n=153) and

older clinopyroxenes (n=15) reported in the literature (Camus et al.,

1987; Mandeville et al., 1996a). All clinopyroxenes plot in a narrow

region in the augite field, implying a common source. The

composition of the orthopyroxenes found in the groundmass (n=26)

is slightly more heterogeneous, spreading over the enstatite and

pigeonite fields.

20

identified using electron backscatter images and EPMA analyses. All olivines observed are

anhedral (resorbed), frequently with rims covered by over-growths of orthopyroxene and

occasional titanomagnetite (Appendix A, image 11). There is a gradual normal zoning in all

the olivines investigated towards more Fe-rich rims. Forsterite content is in the range of Fo63-

80, with most olivine rims below Fo69.

7.4 Groundmass

The groundmass consists of 35% glass, 40% microcrystalline laths of plagioclase, 20%

orthopyroxene and 5% opaque phases, as determined by point counting on high magnification

electron backscatter images (7 images, 88 points each). The glass is dark brown to black, and

not transparent under plain-polarized light. The plagioclase in the groundmass, present as

anhedral laths and needles (An59-68), is chemically very similar to the larger plagioclase

phenocrysts. The orthopyroxenes occur in two modes: as a discontinuous phase on the rims of

partly resorbed olivine, and as microcrysts in the groundmass. No clinopyroxene has been

identified in the groundmass. Only four EPMA analyses were performed on the opaque

phases, all of which were identified as titanomagnetite. Although this is a small number of

analyses, our data coincide with the findings of Camus et al. (1987), who identified

titanomagnetite as the only opaque phase in basaltic-andesites from Anak.

21

8. Estimates of bedrock density and pre-eruptive volatile content

The H2O content is a very influential parameter in a number of the thermobarometers that will

be used. The pre-eruptive volatile content of a rock can be approximated from the mass

deficiency in EPMA analyses of groundmass glass and melt inclusions („the difference

method‟), as described in Devine et al. (1995), provided that the volatiles make up >1%. The

mass deficiency in the glass inclusions ranges from 1.2 % to 4.9 % (average = 2.4 %).

However, the precision of estimating volatile concentrations using the difference method is

not very high, reported to be ±0.5 % (Devine et al., 1995). Mandeville et al. (1996a) estimated

the pre-eruptive volatile content in the 1883 eruptive products to be 4 ± 0.5 wt. %. Due to the

enrichment of H2O in magmas during fractional crystallisation, it would be reasonable to

assume that the water content in the recently erupted basaltic-andesites are lower than in the

considerably more felsic magma of the 1883 eruption. Therefore, the pre-eruptive H2O

content will be approximated to be in the range of 2 to 4 wt. % for the thermobarometric

calculations to follow. Furthermore, for the reasons stated above, the higher end of that range

(3-4 wt. %) will be considered for basaltic-andesite bulk rock compositions, while the lower

end (2 to 3 wt. %) will be considered for basaltic bulk compositions. Note that the H2O

estimates henceforth will be labeled as XH2O, were X is the estimate in weight percent.

For the conversion of pressure estimates (kbar) to depth (km), the approximate densities of

the respective stratigraphic units below Krakatau need to be established. In the seismic study

by Kopp et al. (2001), a seismic line over the Java trench, ending just ~10 km south of

Krakatau, was investigated. The stratigraphy proposed for the area close to the Krakatau

complex by Kopp et al. (2001) will be used as density constraint applicable for the bedrock

directly below Krakatau also (table 1). In Kopp et al. (2001), two different densities are

suggested for different parts of the sedimentary succession, 2.23 and 2.4 g cm-3

, respectively.

For our purpose, an average of the two will be used.

Table 1. Densities of country rock below Anak Krakatau.

Inferred rock types Depth

(km)

Density (g cm-3

)

Sedimentary succession 0-4 2.32

Granitoids 4-9 2.8

Diorite/gabbro 9-22 2.95

Mantle >22 3.37

22

9. Method

The available rock forming mineral phases in the rocks are, plagioclase > clinopyroxene >

orthopyroxene > titanomagnetite > olivine. This allows the use of a number of igneous

thermometers and barometers. The focus will be on the clinopyroxene-melt thermobarometry

(Putirka et al., 1996; 2003; Putirka, 2008) and plagioclase-melt thermobarometry (Putirka,

2005) but will be complemented by other appropriate methods outlined below.

9.1 Clinopyroxene-melt thermo-barometers

Two models based on clinopyroxene-melt equilibria have been applied. The first and most

established model is a thermobarometer developed by Putirka et al. (1996), and later

calibrated for a wider selection of compositions and P-T conditions (Putirka, 1999; Putirka et

al., 2003), including the application to hydrous magmas. This clinopyroxene-melt

thermobarometer is an experimental regression model based on the jadeite-

diopside/hedenbergite exchange equilibria between clinopyroxene and co-existing melt. The

model has proved to be able to recreate P-T conditions for a wide range of magma

compositions, within a reasonable margin of error, and has been widely used in the last

decade (Shaw & Klügel, 2002; Putirka & Condit, 2003; Schwarz et al., 2004; Caprarelli &

Riedel, 2005; Klügel et al., 2005; Galipp et al., 2006; Mordick & Glazner, 2006; Longpré et

al., 2008; Barker et al., 2009). The Putirka et al. (2003) thermobarometer will henceforth be

termed PTB03. The standard errors of estimate (SEE) for PTB03 are ± 33 °C and ± 1.7 kbar

(Putirka et al., 2003). The second clinopyroxene-melt model to be used for comparison is a

barometer based on the Al partitioning between melt and clinopyroxene, and was recently

presented by Putirka (2008, eqn. 32c). That model is noteworthy as it is especially calibrated

for hydrous systems, requiring the input of a specific H2O estimate. This model will be named

PTB08. PTB08 also requires the input of a temperature estimate, which will be provided by

the PTB03 model. Note that PTB08 is not as firmly tested as PTB03, and is thus not

considered quite as reliable, even though the reported SEE of ±1.5 kbar (Putirka, 2008) is

even better than for PTB03. As PTB03 and PTB08 are based on different clinopyroxene-melt

exchange equilibria (Na and Al, respectively), any overlap of the two models would strongly

imply that the results are reliable.

23

Both PTB03 and PTB08 require the input of a mineral composition data and that of a co-

existing melt. The importance of finding a suitable nominal melt, representing the equilibrium

conditions of clinopyroxene formation, needs to be stressed, as it is the single largest source

of error in mineral-melt equilibria models. This is especially true as there is no definite right

or wrong when it comes to choosing a nominal melt, meaning that testing whether the

nominal melt of choice represents an equilibrium melt is exceedingly important. Tests of

equilibrium are often performed (Klügel & Klein, 2005; Longpré et al., 2008; Barker et al.,

2009) using the Fe-Mg exchange coefficients, Kd[FeMg], between clinopyroxene and liquid

(Duke, 1976). The Kd[FeMg] expected for a clinopyroxene-melt system in equilibrium would

be 0.28 ± 0.08 (Putirka, 2008), and clinopyroxene-melt pairs that fall outside these boundaries

will not be considered. As a further equilibrium test, it is useful to take into account the

exchange equilibria of other components, such as Na-Al and Ca-Al, as initially suggested by

Rhodes et al. (1979) and later expanded on by Putirka (1999). The Putirka (1999) model

predicts the relative amounts of different clinopyroxene mineral components that would

crystallize from a given nominal melt at the estimated P-T conditions. The predicted mineral

components (PMC) can then be compared to the observed mineral components (OMC). If the

clinopyroxene and melt compositions are approaching an equilibrium pair, the PMC should

closely match the OMC. Here, the focus will be on the dioipside+hedenbergite component

(DiHd), as it is the main component of the analysed clinopyroxenes, and it will provide a

good complement to the other equilibrium tests that will be performed (Putirka, personal

communication Aug. 2009).

9.2 Clinopyroxene barometers

To test the results of the Putirka clinopyroxene-melt thermobarometry (PTB03 and PTB08), a

clinopyroxene barometer not requiring the input of a coexisting melt would be ideal. The

clinopyroxene composition barometer developed by Nimis (1995; 1999) and Nimis & Ulmer

(1998) is widely used, despite having a tendency of systematically underestimating pressures

when applied on hydrous systems (Putirka, 2008). To eliminate the systematic error, this

barometer was re-calibrated for hydrous systems by Putirka (2008, eqn. 32b), with the added

requirement of an H2O estimate in addition to the temperature estimate already needed. This

barometer will be called NimCal08. The SEE for NimCal08 is at 2.6 kbar (Putirka, 2008).

24

9.3 Plagioclase-melt thermobarometers

Plagioclase-melt thermobarometry has been one of the preferred methods for petrologists to

estimate pressures and temperatures of igneous systems, likely due to the abundance of

plagioclase phenocryst in igneous rocks of varying composition and tectonic setting. Since the

first thermometer was formulated (Kudo & and Weill, 1970), the approach has been

developed further by various authors and a geobarometer has been incorporated (Housh &

Luhr, 1991; Sugawara, 2001; Ghiorso et al., 2002; Putirka, 2005; Putirka, 2008). Putirka

(2005) calibrated the plagioclase-melt thermobarometer for hydrous systems, requiring the

input of a H2O estimate in the modelling calculations. The thermometer in Putirka (2005) was

later improved slightly (Putirka, 2008, eqn. 24a). Despite all this, the accuracy of plagioclase-

melt geobarometry remains underwhelming, reproducing pressures within <3 kbar in most

cases and, occasionally and apparently randomly, produces very poor results from some data

sets. SEE for the plagioclase-melt thermometer is ± 36 °C and ± 2.47 kbar (Putirka, 2008).

The results of the plagioclase-melt thermobarometer will therefore be evaluated in reference

to the findings of Gardner et al. (in review, J. Petrol.), who argue for shallow crustal

plagioclase growth in the Anak magma plumbing system.

The recommended equilibrium test for plagioclase-melt thermobarometry uses the ratio of

the partitioning coefficients of the anorthite and albite components, Kd[An-Ab]. This is

expected to be 0.10 ± 0.05 at low temperatures (T < 1050 °C), or 0.27 ± 0.11 at high

temperatures (T > 1050 °C) (Putirka, 2008). Due to the highly variable composition, only the

plagioclase datapoints closest to equilibrium with the selected nominal melt will be

considered reliable. As a further test for equilibrium, the temperature estimate will be

compared to a plagioclase saturation surface temperature calculated for the nominal melt

(Putirka, 2008, eqn. 26). The plagioclase saturation surface temperature would be the lowest

possible temperature for the nominal melt before plagioclase would start crystallizing. A close

match between the temperature estimates of the plagioclase-melt and plagioclase saturation

thermometers is expected for equilibrium conditions (Putirka, 2008).

9.4 Olivine-melt thermometers

Olivine-melt thermometers (Beattie 1993; Putirka 2007, eqn. 4) will also be tested on the few

olivines found. To test for olivine-melt equilibrium, the test proposed by Roeder and Emslie

25

(1970) has been used, where the partitioning coefficient of Fe and Mg between olivine and

liquid (Kd[FeMg]) should approach 0.30 ± 0.03. Though this value has since been shown to

vary with pressure and silica- and alkali-content, it remains generally valid at pressures below

20 to 30 kbar (Putirka, 2008). As reported by Putirka (2008), the two models that most

successfully manage to recreate temperatures for olivine-melt equilibria are the Beattie (1993)

and Putirka (2007, eqn. 4) models, henceforth labeled BO93 and PO07, respectively. Though

BO93 is the overall more successful olivine-melt thermometer, it has a tendency of

systematically overestimating temperatures for hydrous systems, a problem the PO07

thermometer is calibrated to avoid (Putirka et al., 2007; Putirka, 2008). PO07 may therefore

be considered the most suitable model (Putirka, 2008). The SEE of PO07 is ± 29 °C (Putirka,

2008). In this study, the main reason for employing olivine-melt thermometry is to provide an

independent test for the reliability of the clinopyroxene-melt thermobarometry. The

temperature estimates from clinopyroxene-melt and olivine-melt thermometry will be

compared and a close match would indicate a high reliability of the results (Longpré et al.,

2008; Putirka, personal communication Aug. 2009). This approach assumes that the

clinopyroxenes and olivines are coeval, and will only be applicable if both clinopyroxene and

olivine perform adequate equilibrium tests using the same nominal melt.

26

10. Results

In this section, the results of the thermobarometric models described above are presented. .

The methods employed are a.) clinopyroxene-melt thermo-barometry (Putirka et al., 2003;

Putirka, 2008) b.) clinopyroxene composition barometry (Nimis & and Ulmer, 1998; Nimis,

1999; Putirka, 2008) c.) plagioclase-melt thermo-barometry (Putirka, 2005) and d.) olivine-

melt thermometry (Putirka et al., 2007). The clinopyroxene-melt thermobarometry (PTB03

and PTB08) as well as the plagioclase-melt thermobarometry is considered most reliable

(Putirka, 2008). The other models mentioned will mainly be used for reference, as overlap in

results between different models is a very strong indication of reliable results.

10.1 Pressures and temperatures from clinopyroxene-melt

thermobarometry

The first, and arguably most important

step, when employing a mineral-melt

equilibrium model is to find a suitable

nominal melt. As mentioned above, the

clinopyroxenes exhibit no obvious signs of

being out of equilibrium with the host melt,

as they are euhedral and lack any major

compositional zoning. However, euhedral

habitus and the lack of zoning does not by

itself verify that the clinopyroxene was in

equilibrium with the host melt, especially

considering the sluggishness of

clinopyroxene re-equilibration, that is on the

order of months to years for a 5-10µm rim

(Cashman, 1990), and the rather short repose

time at Anak Krakatau volcano, often with tens of smaller eruptions during a single year.

The most commonly used nominal melts are: a.) bulk rock composition (Caprarelli &

Riedel, 2005; Putirka & Condit, 2003; Putirka et al., 2003) and b.) groundmass or groundmass

glass (Shaw & Klügel, 2002; Klügel et al., 2005; Longpré et al., 2008). In

Figure 18. Test for equilibrium using the Kd[FeMg]

between clinopyroxene and melt. The 1963 basalt and

2002 bulk rock both result in Kd[FeMg] values close to

the ideal of 0.28 (Putirka, 2008), and are selected as the

two viable nominal melt options.

60

65

70

75

80

0 20 40 60

10

0xM

g# c

px

100xMg# melt

1963 Basalt

Melt inclusions

2002 bulk rock

Groundmass

Glass

Out of equilibrium Out of equilibrium

27

addition to these options, two

more nominal melts will be

evaluated here. These are melt

inclusions (in plagioclase and

clinopyroxene) and a more

primitive bulk rock from a lava

flow from the eruptive period

1960-1963 (henceforth labeled

1963 basalt) reported in Zen and

Hadikusumo (1964). In Fig. 18,

the Kd[FeMg] of the five

nominal melt options outlined

above are compared. It is

apparent that groundmass and

glass are far from equilibrium

conditions with the

clinopyroxene.

Of the remaining three

options, the 1963 basalt and the

bulk rock fit well within the

expected boundaries, while

inclusions appear to be only

slightly out of equilibrium. In

Fig. 19, the observed and

predicted DiHd components are

plotted, using the (a) 1963 basalt

and (b) 2002 bulk rock. Both

result in a very good match. It is

thus not possible, using only

these methods, to determine whether the 1963 basalt or 2002 bulk rock is the better nominal

melt. Both of those nominal melts will be used therefore, resulting in six sets of P-T estimates

using the PTB03 and PTB08 models with different input of nominal melts and H2O estimates.

The results of these model calculations are summarised in Fig. 20a-b. The average P estimate

of -0.57 kbar (range = -1.81 to 0.43) gained from PTB03 using the 2002 bulk rock as nominal

Figure 19. The predicted vs. observed mineral components of

diopside+hedenbergite, using nominal melts (a) 1963 basalt and (b)

2002 bulk rock. Both nominal melts result in very similar results, in

terms of predicted mineral compositions, indicating that both need

to be considered viable nominal melts. Clinopyroxenes analyzed for

this thesis and older clinopyroxenes (erupted 1883-1981) are

represented by black and red circles respectively.

0,60 0,80 1,00

Ob

se

rve

d c

px C

om

po

ne

nts

Predicted px Components

Nominal melt: 2002 bulk rock

0,60 0,70 0,80 0,90 1,00

Ob

se

rve

d c

px C

om

po

ne

nts

Predicted cpx Components

Nominal melt: 1963 basalt

28

melt is an impossible result. Also, using the 2002 bulk rock as nominal melt, there is no

overlap of the results from the PTB03 and PTB08 calibrations. This indicate that the 2002

bulk rock is not suitable as a nominal melt composition from which the clinopyroxene has

crystallized, and will therefore not be considered further. The three sets of calculated

pressures using the 1963 basalt as nominal melt are in a narrow range (0.59 to 3.77 kbar) with

a high degree of overlap between PTB03 and PTB08 results. PTB03 and PTB08 were also

employed using representative clinopyroxene compositions reported in the literature (Camus

et al., 1987; Mandeville et al., 1996a). These clinopyroxenes come from rocks erupted

between 1883 and 1981. The results of the old clinopyroxenes are plotted in Fig. 20c,

spreading over a much larger P-T interval, and the majority of them record higher pressures

and temperatures as compared to the more recent ones. This indicates that the bulk of the

clinopyroxenes prior to the acidic-andesite eruption of 1981 crystallized at a greater depth

compared to the recently erupted clinopyroxenes. Note that the old clinopyroxenes did not

perform quite as well in the equilibrium test as the more recent clinopyroxenes. However, the

difference in this equilibrium test between old and recent clinopyroxenes is very slight, and all

datapoints are within the allowed 5% deviation. All results of clinopyroxene-melt

thermobarometry, using the 1963 basalt as nominal melt, are reported in table 2.

Figure 20. Results of PTB03 (filled circles) and PTB08

using 2H2O (filled triangles) and 3H2O (open triangles).

Recent and old clinopyroxenes are displayed in black

symbols and red symbols respectively, Note that, when

using the 1963 basalt (a), results of the PTB03 and PTB08

models are overlapping. The 2002 bulk rock (b) does not

produce an overlap. This is a strong indication that the

1963 basalt is the most suitable nominal melt. The

pressures and temperatures calculated for the old

clinopyroxenes (c) are consistently higher than for the

recent clinopyroxenes. SEE for PTB03 are ± 33 °C and ±

1.7 kbar. SEE for PTB08 is ± 1.5 kbar

0

1

2

3

4

5

1090 1100 1110 1120 1130

P (

kb

ar)

T (° C)

(a)

Nominal melt:1963 basalt

0

1

2

3

4

5

6

7

8

1100 1120 1140 1160

P (

kb

ar)

T (° C)

(c)

Nominal melt:1963 basalt

-2

-1

0

1

2

3

4

5

1080 1090 1100 1110 1120

P (

kb

ar)

T (°C)

(b)

Nominal melt:2002 bulk rock

29

10.2 Pressure estimates from clinopyroxene barometry

The NimCal08 barometer (Putirka, 2008, eqn. 32b), using temperature estimates calculated

using the PTB03 model, yields pressures slightly lower than the PTB03 and PTB08 models.

Estimates of 2H2O and 3H2O result in average pressures of 1.03 kbar (-0.57 to 2.14) and 1.48

kbar (-0.11 to 2.59) respectively. As mentioned above, this model is not deemed very precise

nor accurate, with a tendency of systematically underestimating pressure (Putirka, 2008).

Despite this, the overall overlap with model results from PTB03 and PTB08 lends further

credence to these results. The results of the NimCal08 barometer is plotted in Fig. 21, and

table 2, for comparison with the PTB03 and PTB08 models.

Figure 21. Results of the

NimCal08 barometer.

Results using 2H2O and

3H2O are represented by

filled and open squares

respectively. The partial

overlap with results from

the PTB03 and PTB08

models lends further

credence to these results.

SEE for NimCal08 is at

2.6 kbar.

Table 2. Clinopyroxene-melt thermobarometry and clinopyroxene barometry.

Model Nominal

melt

XH2O (%) Recent clinopyroxenes

(1990-2002)

Old clinopyroxenes

(1883-1981)

P (kbar) T (°C) P (kbar) T (°C)

PTB03 1963 basalt N/A 2.74

(1.46 to 3.77) 1116

(1102 to 1123)

4.85

(2.64 to 7.52)

1131

(1113 to 1154)

PTB08 1963 basalt 2 1.92

(0.59 to 2.83)

N/A 2.78

(1.15 to 5.61)

N/A

3 2.59

(1.26 to 3.50)

3.45

(1.82 to 6.28)

NimCal08 N/A 2 1.03

(-0.57 to 2.14)

N/A 2.41

(-1.72 to 5.66)

N/A

3 1.48

(-0.11 to 2.59)

2.86

(-1.27 to 6.11)

-1

0

1

2

3

1100 1110 1120 1130

P (

kb

ar)

T (°C)

30

10.3 Pressures and temperatures from plagioclase-melt

thermobarometry

Of all the potential nominal

melts, the 2002 bulk rock

performed best in the Kd[ab-an]

equilibrium test with the

plagioclase (Fig. 22), with the

majority of the datapoints falling

within the field of equilibrium.

The plagioclase-melt pairs

outside the field of equilibrium

will not be considered for the

model calculations. However, at

>3.5H2O the temperature

estimates calculated are all below

1050, requiring equilibrium

conditions of Kd[Ab-An] that

differ from 0.27 ± 0.11 (Putirka,

2008), i.e. the plagioclase is not in equilibrium with the bulk rock at >3.5H2O. This effectively

constrains pre-eruptive H2O content in the basaltic-andesite to ≤3.5H2O. A further indication

that the 2002 bulk rock is a suitable nominal melt for plagioclase-melt thermobarometry is the

fact that the plagioclase saturation surface temperatures calculated are only on average ~10 °C

higher than the temperature estimated using the plagioclase-melt thermometer. The results of

plagioclase-melt thermobarometry, using 2002 bulk rock, 3H2O and 3.5H2O, is displayed in

table 3 and Fig. 23. Note that there is no systematic difference between P-T estimates for

plagioclase cores and rims. However, there is a strong correlation with An content and P-T

estimates. High An contents, resulting in low Kd[An-Ab], correspond to low pressure

estimates and vice versa. Plagioclase with medium An content appears to be closest to

equilibrium with the bulk rock, with a range of An62-68 yielding Kd[An-Ab] values very close

to the ideal of 0.27 (0.24-0.30) determined by Putirka (2008). These “best fit” plagioclases

result in a very tight range of temperature and pressure estimates, where T = 1065 to 1071 °C

Figure 22. Equilibrium test for plagioclase and three nominal melt

options. The 2002 bulk rock result in the best fit, and will be used

in the plagioclase-melt thermobarometry.

0

10

20

30

40

50

0 5 10 15

1000 x

An

x A

b l

iq

1000 x Ab x An liq

2002 Bulk rock

Groundmass

1963 Basalt

31

and P = 1.24 to 1.81 kbar (assuming 3H2O), or 1049 to 1055 °C and 0.72 to 1.24 kbar

(assuming 3.5H2O). These two sets of P-T estimates are considered the most reliable.

Table 3. Results from plagioclase-melt thermobarometry.

T (°C) Saturation surface

T (°C)

P (kbar)

Kd[An-Ab] =

0.16-0.38

P (kbar)

Kd[An-Ab] =

0.24-0.30

Nominal melt XH2O (%)

1051

(1044 to 1060)

1061 1.06 (0.33 to 1.75) 1.01 (0.72 to 1.24) 2002 Bulk rock 3.5

1067

(1059 to 1076)

1076 1.61 (0.80 to 2.35) 1.56 (1.24 to 1.81) 2002 Bulk rock 3

10.4 Temperature estimates from olivine-melt thermometry

As the olivine phase is clearly not stable in the basaltic-andesite host rock, neither bulk

rock chemistry nor groundmass can be considered as feasible nominal melts for olivine-

melt thermometry. However, the more primitive bulk rock of the 1963 basalt seems to

better represent the magma that gave rise to initial olivine crystallization. Three bulk rock

compositions from the 1963 lava flow (Zen & Hadikusumo, 1964) will be compared:

analysis No. 4, 5, and an average of the two. Analysis No 5 has the highest magnesium

Figure 23. Results of plagioclase-

melt thermobarometry, using

3.5H2O (red triangles) and 3H2O

(blue circles). Only the

plagioclase compositions closest

to equilibrium with the 2002 bulk

rock have been used in this plot.

The dotted lines indicate the

respective estimated saturation

surface temperatures (Putirka,

2008), very close to the calculated

temperatures. Note also that

there is no systematic difference

between P-T estimates for

plagioclase cores and rims. SEE

for the plagioclase-melt

thermobarometer are ± 36 °C

and ± 2.47 kbar

0

0,5

1

1,5

2

1040 1050 1060 1070 1080

P (

kb

ar)

T (° C)

3H2O

3.5H2O

32

number of the three. Using the Kd[FeMg] of Roeder and Emslie (1970) as discriminant,

the olivines are divided into three classes by being close to equilibrium with the three

different bulk rocks (Fig. 24). The Forsterite content of these three classes would be Fo75-

76, Fo70-72 and Fo69-67. Note that olivines above Fo77 and below Fo67 are out of equilibrium

with all nominal melts tested, and are thus discarded. This results in three sets of

temperatures (see table 4) in the range of 1106 to 1153 °C. The results, and a comparison

with the temperatures estimated for clinopyroxene using PTB03, are plotted in Fig. 25.

Note that the temperatures estimated for olivine are overlapping with temperatures

estimated for clinopyroxene, suggesting that the olivine-melt and clinopyroxene-melt

models are consistent with each other (Longpré et al., 2008; Putirka, personal

communication Aug. 2009).

Figure 24. Test for olivine-

melt equilibrium. The

olivines are divided into

three compositional groups

based on their forsterite

content and which nominal

melt produces the best fit.

Note that the average bulk

composition was used as

nominal melt in the PTB03

model.

60

65

70

75

80

35 40 45 50 55

10

0xM

g#

Oliv

ine

100xMg# Liquid

1963 basalt (no:4)

1963 basalt (average)

1963 basalt (no:5)

outside equilibrium

outside equilibrium

33

Table 4. Results of olivine-melt thermometry

Figure 25. Results of

olivine-melt

thermobarometry. The

overlap of temperatures

estimated for olivine

(PO07) and clinopyroxene

(PTB03) is a strong

indication that the results

are reasonable. The SEE

for PO07 is at ± 29 °C.

Model T (°C) Fo75-76 T (°C) Fo70-72 T (°C) Fo67-69

PO07 1153 (1152 to 1153) 1131 (1127 to 1139) 1110 (1106 to 1112)

1090

1100

1110

1120

1130

1140

1150

1160T

(°C

)

Olivine composition

Fo76-75 Fo72-70 Fo69-67

cpx temperature(PTB03)

34

11. Discussion

The clinopyroxene-melt and plagioclase-melt thermobarometry resulted in two distinct sets

of P-T estimates with very little overlap, indicative of two distinct magma crystallisation

(storage) regions. In Fig. 26, the results from plagioclase-melt and clinopyroxene-melt

barometry are displayed as histograms, with the pressure estimates converted to depth. It is

evident that the calculated depths of plagioclase and clinopyroxene crystallization are focused

to in the region of 4-6 and 8-12 km respectively. Fig. 27 combines all results from

clinopyroxene-melt and plagioclase-melt barometry in one plot.

The depths calculated for plagioclase crystallization (4-6 km) fit well with previously

calculated depths as well as evidence from crystal isotope stratigraphy (Camus et al., 1987;

Mandeville et al., 1996a; Gardner et al., in review, J. Petrol.). In turn, the zone of

clinopyroxene crystallization (8-12 km) coincide very well with the findings of Harjono et al.

(1989), identifying a magma chamber system at a depth of ~9 km, with an unknown vertical

extension. These contrasting depths calculated for plagioclase and clinopyroxene

crystallization are not contradictory, as plagioclase should represent a later stage of

crystallization than clinopyroxene, but rather it indicates a shallow and a deeper magma

storage region. Also, a lack of seismic attenuation zones at depths less than 9 km does not

exclude shallower magma storage. A diffuse zone of small pockets of magma, e.g. as

discussed in Gardner et al. (in review, J. Petrol.) would likely be outside the detection limit of

the micro-seismic study of Harjono et al. (1989).

In this study, no strong evidence of the very deep storage zone (>22 km), detected by

Harjono et al. (1989), has been found. This implies that crystalline phases potentially formed

in the deep storage region very rarely survive ascent and crustal storage, due to resorption in

the progressively evolving melts, or remain in deep seated cumulates. A few of the old

clinopyroxenes analyzed, however, do record depths of crystallization greater than 18 km (fig.

20, 26, 27 and table 5), implying that they might have formed in this very deep storage region.

Therefore, there are strong lines of thermobarometric, geophysical and isotopic evidence

for up to three distinct magma storage regions below Anak, at depths of approximately 4-6

and 8-12 km plus a probable very deep storage region at ≥22 km, as discussed in Harjono et

al. (1989). These three zones fit remarkably well with the three lithological boundaries (Fig.

10) inferred for the bedrock below Anak Krakatau, based on evidence from drill holes,

xenoliths and micro-seismic studies. Additionally, there are indications of a shallowing of the

35

plumbing system over recent years (fig. 20, 26, 27 and table 5), with respect to clinopyroxene

crystallization.

Key factors controlling the ascent of silicate magmas may be a.) fractures, states of stress

and mechanical properties of the lithosphere, and b.) density contrasts between magma and

rock, where light density lithologies act as barriers for denser magma (Putirka et al., 2003, and

Figure 26. Calculated pressures from (a) plagioclase-melt

barometry, (b) PTB03 and PTB08 for recent

clinopyroxene, and (c) PTB03 and PTB08 for old

clinopyroxene. Plagioclase record depths of crystallisation

that considerably shallower than clinopyroxene, and pre-

1981 clinopyroxenes record deeper levels of crystallisation

than recent clinopyroxenes.

Figure 27. All results from clinopyroxene-melt and

plagioclase-melt barometry (fig. 26). The clinopyroxene

and plagioclase record distinctly different depths of

crystallisation with very little overlap. The old

clinopyroxene appear to have crystallised partly at

deeper levels, and are spread over a larger interval.

36

references therein). The bedrock beneath Anak is heavily fractured and faulted, which would

provide ample vertical pathways for magma ascent. Results of the mineral-melt

thermobarometry (this thesis) and geophysical investigations (Harjono et al., 1989), however,

strongly indicate that magma storage below Anak is chiefly controlled by discontinuities and

lateral lithological boundaries in the crust, where density contrasts between the different

lithologies plays an important role.

The magma evolution and plumbing system beneath Anak is thus envisaged in the

following manner:

1) Partial melting of the mantle wedge and transport of magma up to the mantle-lower

crust boundary, where magma ascent is halted due to the density contrast with the lower crust.

The initial melt composition may also, to some extent, be influenced by decompressional

melting, due to the extensional character of the Sunda Straits (Harjono et al., 1991). The

extent of the seismic attenuation zone (Fig. 11) detected by Harjono et al (1989) implies that

this storage region is large-scale and likely interconnected. This would, in part, account for

the semi-continuous supply and semi-homogenous character of the Anak basaltic-andesites.

Analogous to this would be the “deep crustal hot zones” proposed by e.g. Annen et al. (2006).

2) Ascent of basalt either when magma density has decreased to below that of the lower

crust (~2.95 g cm-3

), or when replenishment of fresh basalt and associated volatile release into

the magma chambers from below forces ascent to higher levels.

3) The ascending magma stalls at a mid-crustal level due to density contrast, at a depth of

~9 km, where crystallization of clinopyroxene takes place. The euhedral habitus and

homogenous composition of all observed and analyzed clinopyroxenes would indicate a

sizeable and stable storage region with a continuous supply of magma. The bulk composition

of the magma at this level is likely close to the evolved basalt documented in Zen &

Hadikusumo (1964), as indicated by clinopyroxene being in apparent equilibrium with this

bulk composition at the calculated thermodynamic conditions.

4) Again, ascent of magma is triggered by either evolving the magma towards a less dense,

basaltic-andesitic composition, with a magma density lower than that of the middle crust

(~2.75 g cm-3

), or when replenishment of fresh magma and associated release of gases from

below forces ascent.

5) At a depth of ~4 km, the magma ascent is stalled once more again, at a major

lithological boundary. The main phase of plagioclase crystallization takes place at this level.

The large compositional variation of plagioclase (An45-80), the sieve-like textures and complex

zoning patterns would suggest a highly dynamic magma system. The sieve-like textures, in

37

particular, could be an indication of rapid growth and/or dissolution, which in turn can be

related to events like magma mixing, replenishment, and assimilation of country rock (e.g.

Tepley et al., 1999; Troll et al., 2004). This shallow storage region is likely made up of a

plexus of more or less interconnected pockets of magma dispersed in the crust, as it was not

detected in the low resolution micro-seismic study of Harjono et al. (1989), but has been

detected by Gardner et al. (in review, J. Petrol.) using in situ (LA-ICPMS) 87

Sr/86

Sr analyses

on plagioclase to show sediment contamination in plagioclase growth zones. This storage

region is likely where the magma evolves to its final pre-eruptive composition (i.e. basaltic-

andesite) before being erupted, as indicated by plagioclase being close to equilibrium with

this bulk composition at the calculated thermodynamic conditions. See Fig. 28 for a schematic

illustration of the current magma plumbing system beneath Anak Krakatau.

Thermal preconditioning of the upper crust by mafic to intermediate magmas has been

suggested to be a major factor in the production of rhyolitic magmas in the Taupo Volcanic

Zone (Price et al., 2005). This petrogenic model could potentially be applicable to the

Figure 28. The magma

plumbing system at

Anak Krakatau. Three

magma storage regions

have been identified, of

which the upper two

have been verified by

thermobarometric

model calculations in

this study. Only the

mid-crustal storage

level (at ~8-12 km

depth) has been

detected by both

seismic and

thermobarometric

studies. Therefore,

combined geophysical

and petrological

surveys provide the

highest potential for the

thorough

characterization of

magma plumbing at

active volcanic

complexes.

38

Krakatau complex, considering its history of recurring major dacitic-rhyolitic eruptions with

intermittent periods of mafic-intermediate magmatism. In this model, a steep geothermal

gradient and continuous heating of the crust would eventually lead to large scale assimilation

of country rocks, as well as recycling of co-magmatic plutons and intrusives. The idea that the

uppermost magma storage region (~4-6 km) detected is made up of a plexus of magma

pockets, as discussed above, means that the surface-to-volume ratio of the magma volume

stored at that level is high, leading to an efficient heat transfer from magma to crust. The high

magma throughput at Anak Krakatau, evident in the average extrusive growth of 8 cm/week,

would further add to the efficient heating of the crust. In concert with these speculations, the

geothermal gradient in one of the 3 km deep wells, ~30 km south-southeast of Krakatau has

been estimated to be as high as 67 °C/km (Nishimura et al., 1986).

With the model proposed by Price et al. (2005) and the cyclicity of van Bemmelen (1949)

in mind, the shallowing of the plumbing system detected in this study could be an indication

that Krakatau is presently in the process of evolving towards a new major caldera forming

eruption.

Table 5. Calculated pressures converted to depth

Model Mineral phase Nominal melt XH2O

(%)

Time of eruption Depth (km)

PTB03 Clinopyroxene 1963 basalt N/A 1990-2002 10.59 (6.15 to 14.14)

1883-1981 17.85 (10.24 to 26.85)

PTB08 Clinopyroxene 1963 basalt 2 1990-2002 10.05 (5.45 to 13.20)

1883-1981 13.04 (7.39 to 22.78)

PTB08 Clinopyroxene 1963 basalt 3 1990-2002 7.70 (2.58 to 10.88)

1883-1981 10.73 (5.08 to 20.51)

Plagioclase-melt Plagioclase 2002 bulk rock 3 1990-2002 6.39 (5.22 to 7.26)

Plagioclase-melt Plagioclase 2002 bulk rock 3.5 1990-2002 4.35 (3.16 to 5.19)

Figure 29. The cyclicity of Krakatau, redrawn and modified from van Bemmelen (1949). The red hatched area

represents the inferred recent shallowing of the magma plumbing system.

39

12. Conclusions

Our results imply that clinopyroxene presently crystallizes in a mid-crustal storage region (8-

12 km), a magma storage region previously identified in the micro-seismic study by Harjono

et al. (1989). Plagioclase, in turn, form at shallower depths (4-6 km), very much in concert

with previous estimates based on plagioclase barometry and chlorine in fluid inclusions

(Camus et al., 1987; Mandeville et al., 1996a; Gardner et al., in review, J. Petrol.).

Clinopyroxenes erupted between 1981-1883 record deeper levels of storage, indicating that

there may have been a shallowing of the plumbing system over the last ~40 years. This study

demonstrates that petrology can detect magma bodies in the crust where seismic surveys fail

due to limitations in resolution, and vice versa in the case of the ~22 km system.

Consequently, a combination of geophysical and petrological surveys offers the highest

potential for a thorough characterization of magma plumbing at active volcanic complexes.

The magma storage regions detected beneath Krakatau coincide with major lithological

boundaries in the crust, implying that magma ascent at Anak is controlled by discontinuities

in the crust. This, in turn, indicates that density contrasts between magma and bedrock is an

important parameter controlling magma ascent at this particular volcanic complex. However,

the extensional character and heavily faulted bedrock in the Sunda Straits (Nishimura et al.,

1986), is likely fundamental in providing vertical pathways for magma to ascend, meaning

that other factors such as stratigraphy, play a significant role too.

The compelling evidence presented in this study of widespread and shallow magma storage

at this highly active volcano, coupled with the documented caldera forming eruptions at the

Krakatau complex in the recent past, means that continuous seismic and petrologic monitoring

of Anak Krakatau remain of utmost importance. This is especially true considering that

Indonesia today has the world‟s fourth largest population, with a much more densely

populated proximal area compared to that in 1883, when the latest major ignimbrite eruption

claimed 36,000 lives.

40

Acknowledgement

For the opportunity to work on this project, for all the discussions, counselling and for

providing endless inspiration, I would like to thank my supervisors Prof. Valentin R. Troll

and Dr. Ulf Bertil Andersson.

When working at the EPMA facilities at Uppsala University, I was greatly helped by

specialist technician Hans Harryson.

I would also like to thank Jane Chadwick, Mairi Gardner, Frances Deegan, Lara Blythe,

Abigail Barker, Peter Dahlin and Axel Andersson. You have all been of great help.

A heartfelt thanks goes to all the participants in the field trip to Java and Bali in 2008. You all

made the trip memorable.

Kristina, thank you for everything not geology.

The project was made possible by funding provided by Vetenskapsrådet, Uppsala University

and Otterborgs donationsfond.

41

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46

Appendix 1 – Chemical composition of analysed clinopyroxene phenocrysts

SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O Cr2O3 SUM

AK-LF 3-PX p1 51.94 0.47 1.56 9.66 0.75 15.06 20.06 0.32 0.00 0.00 99.80

AK-LF 3-PX 51.40 0.50 1.49 8.53 0.48 15.63 20.55 0.27 0.00 0.00 98.85

AK-LF 3-PX p3 51.37 0.70 1.89 9.14 0.34 15.62 20.09 0.30 0.00 0.00 99.44

AK-LF 3-PX p4 51.41 0.68 2.26 9.42 0.36 15.91 19.41 0.13 0.00 0.00 99.57

AK-LF 3-PX p5 51.34 0.64 2.16 8.96 0.33 15.54 19.54 0.17 0.00 0.00 98.68

AK-LF 3-PX p6 51.01 0.80 2.21 9.18 0.46 14.45 20.22 0.21 0.00 0.00 98.56

AK-LF 3-PX tr Pl>rim 51.70 0.64 2.05 9.75 0.31 15.28 19.84 0.27 0.01 0.00 99.85

AK-LF 3-PX tr Pl>rim 51.96 0.68 2.01 9.34 0.34 15.32 20.39 0.20 0.00 0.00 100.23

AK-LF 3-PX tr Pl>rim 51.67 0.58 1.93 9.23 0.36 15.84 19.99 0.29 0.00 0.00 99.89

AK-LF 3-PX tr Pl>rim 52.38 0.47 1.63 9.01 0.42 15.53 20.24 0.21 0.00 0.01 99.91

AK-LF 3-PX tr Pl>rim 51.21 0.66 2.26 9.93 0.54 14.71 20.30 0.23 0.00 0.01 99.84

AK-LF 3-PX tr Pl>rim 52.68 0.46 1.41 9.43 0.62 15.78 19.77 0.17 0.01 0.00 100.34

AK-LF 3-PX tr Pl>rim 52.86 0.45 1.14 9.22 0.59 15.90 19.83 0.09 0.00 0.00 100.08

AK-LF 3-PX tr Pl>rim 52.64 0.40 1.15 9.45 0.52 15.60 20.08 0.14 0.00 0.00 99.98

AK-LF 3-PX tr Pl>rim 52.67 0.45 1.28 9.52 0.59 15.59 19.77 0.18 0.00 0.00 100.05

AK-LF 3-PX tr Pl>rim 52.41 0.44 1.39 9.53 0.67 15.15 19.90 0.19 0.00 0.00 99.68

AK-LF 3-PX tr Pl>rim 52.04 0.43 1.36 9.07 0.60 15.60 20.43 0.17 0.00 0.00 99.70

AK-LF 3-PX tr Pl>rim 51.07 0.53 1.54 9.06 0.46 15.53 20.64 0.10 0.00 0.00 98.95

AK-LF 3-PX tr Pl>rim 51.39 0.57 1.75 8.60 0.44 15.87 20.38 0.23 0.00 0.01 99.25

AK-LF 3-PX tr Pl>rim 52.11 0.63 1.85 8.93 0.30 15.45 20.57 0.17 0.00 0.00 100.00

AK-LF 3-PX tr Pl>rim 51.74 0.57 1.70 10.08 0.36 15.83 18.93 0.22 0.01 0.00 99.44

AK-LF 3-PX tr Pl>rim 51.29 0.69 2.04 9.59 0.27 15.44 19.83 0.04 0.00 0.02 99.22

AK-LF 3-PX tr Pl>rim 51.53 0.61 1.87 9.50 0.35 15.55 19.90 0.20 0.01 0.00 99.52

AK-LF 3-PX tr Pl>rim 51.89 0.69 2.14 9.87 0.34 15.36 19.50 0.25 0.00 0.00 100.06

AK-LF 3-PX tr Pl>rim 52.18 0.55 1.63 10.93 0.34 16.50 17.82 0.09 0.00 0.00 100.04

AK-LF6-PX p11 52.32 0.65 2.04 9.71 0.34 15.40 19.93 0.26 0.00 0.01 100.66

AK-LF6-PX p12 51.01 0.80 3.15 9.92 0.26 15.30 19.55 0.17 0.00 0.00 100.15

AK-LF6-PX p13 52.02 0.66 1.93 9.45 0.32 15.59 20.01 0.18 0.02 0.00 100.18

AK-LF6-PX p14 52.16 0.68 2.16 9.60 0.35 15.62 19.91 0.21 0.00 0.00 100.68

AK-LF1-PX p16 51.61 0.64 2.06 9.71 0.33 15.46 20.13 0.20 0.00 0.03 100.17

AK-LF1-PX p17 52.31 0.63 2.09 9.11 0.31 15.32 20.47 0.20 0.00 0.01 100.45

AK-LF1-PX p18 51.43 0.69 2.17 9.44 0.27 15.40 20.30 0.22 0.00 0.00 99.92

AK-LF6-PX tr R-R 50.82 0.68 2.36 9.12 0.32 15.22 20.07 0.40 0.00 0.01 99.01

AK-LF6-PX tr R-R 51.55 0.86 2.71 9.33 0.41 15.78 19.81 0.27 0.00 0.00 100.72

AK-LF6-PX tr R-R 50.17 0.74 2.71 8.74 0.28 15.65 20.29 0.17 0.00 0.00 98.74

AK-LF6-PX tr R-R 50.26 0.65 2.59 8.42 0.29 15.67 20.63 0.21 0.00 0.00 98.72

AK-LF6-PX tr R-R 51.96 0.70 2.26 8.41 0.24 15.55 20.67 0.15 0.01 0.03 99.98

AK-LF6-PX tr R-R 52.47 0.59 1.89 8.51 0.47 16.02 20.42 0.19 0.00 0.00 100.56

AK-LF6-PX tr R-R 51.98 0.55 1.71 8.79 0.48 16.20 19.98 0.11 0.00 0.00 99.80

AK-LF6-PX tr R-R 51.65 0.61 2.11 8.78 0.35 15.78 20.39 0.21 0.00 0.00 99.89

AK-LF6-PX tr R-R 51.25 0.45 1.56 9.24 0.54 15.26 20.57 0.27 0.00 0.00 99.12

AK-LF6-PX tr R-R 51.66 0.65 2.08 9.79 0.29 15.67 20.03 0.18 0.00 0.00 100.35

47

AK-LF6-PX tr R-R 51.57 0.62 2.32 9.79 0.26 15.54 19.83 0.23 0.00 0.00 100.17

AK-LF6-PX tr R-R 51.09 0.37 1.31 9.18 0.57 15.23 20.35 0.08 0.00 0.00 98.19

AK-LF6-PX tr R-R 52.78 0.41 1.33 8.49 0.41 15.65 20.91 0.17 0.00 0.00 100.15

AK-LF6-PX tr R-R 51.62 0.73 2.71 8.30 0.25 15.16 20.92 0.17 0.00 0.00 99.86

AK-LF6-PX tr R-R 52.15 0.65 2.24 8.73 0.26 15.31 20.28 0.23 0.02 0.00 99.86

AK-LF6-PX tr R-R 51.28 0.60 2.04 8.90 0.36 15.12 20.49 0.11 0.00 0.00 98.89

AK-LF6-PX tr R-R 51.84 0.66 2.26 9.27 0.27 15.21 19.97 0.13 0.00 0.00 99.62

AK-LF6-PX tr R-R 51.22 0.71 2.55 9.45 0.30 15.52 19.92 0.14 0.00 0.00 99.82

AK-LF6-PX tr R-R 51.36 0.75 2.22 10.56 0.32 16.11 18.30 0.06 0.06 0.01 99.76

AK-LF6-PX tr R-R 51.21 0.79 2.30 10.24 0.40 15.25 19.26 0.10 0.00 0.00 99.56

AK-LF6-PX tr R-R 51.72 0.79 2.42 10.49 0.32 15.21 19.01 0.20 0.00 0.03 100.19

AK-LF6-PX tr R-R 51.74 0.68 2.02 9.27 0.29 15.25 20.14 0.23 0.00 0.02 99.64

AK-LF6-PX tr R-R 51.55 0.60 1.86 9.44 0.45 14.99 20.16 0.29 0.00 0.00 99.34

AK-LF6-PX tr R-R 51.14 0.64 2.28 9.58 0.28 15.33 19.79 0.24 0.00 0.00 99.27

AK-LF6-PX tr R-R 52.13 0.64 2.21 9.62 0.26 15.37 19.88 0.11 0.00 0.00 100.21

AK-LF6-PX tr R-R 52.04 0.65 2.21 10.00 0.30 15.57 19.92 0.25 0.00 0.00 100.95

AK-LF6-PX tr R-R 52.13 0.65 2.19 9.90 0.34 15.37 19.73 0.21 0.00 0.00 100.52

AK-LF6-PX tr R-R 52.16 0.64 2.11 9.60 0.36 15.71 19.91 0.15 0.00 0.00 100.65

AK-LF6-PX tr R-R 52.15 0.64 2.02 9.59 0.41 15.38 20.44 0.22 0.00 0.01 100.86

AK-LF6-PX tr R-R 51.34 0.60 2.10 9.43 0.53 14.97 20.36 0.32 0.00 0.00 99.65

AK-LF6-PX tr R-R 51.33 0.81 2.44 9.79 0.37 14.77 19.94 0.24 0.00 0.00 99.68

AK-LF6-PX tr R-R 50.62 0.74 2.79 9.26 0.29 15.42 20.28 0.19 0.00 0.01 99.61

2_AK14px p1 50.71 0.73 2.70 9.24 0.36 15.57 19.96 0.23 0.00 0.03 99.53

2_AK14px p2 50.88 0.75 2.49 10.05 0.34 15.83 18.95 0.27 0.00 0.01 99.56

2_AK14px p5 50.52 0.70 2.30 9.22 0.29 15.57 20.10 0.16 0.00 0.02 98.91

2_AK12px p8 51.74 0.65 2.34 8.68 0.34 15.33 20.53 0.25 0.00 0.02 99.88

2_AK12px p9 51.15 0.66 2.08 9.24 0.30 14.93 19.78 0.21 0.00 0.04 98.38

2_AK12px p10 51.53 0.68 2.20 9.60 0.27 15.16 19.65 0.24 0.00 0.00 99.32

2_AK12px p13 50.75 0.83 3.09 8.58 0.29 15.07 20.30 0.28 0.00 0.00 99.18

2AK14px tr1 49.92 0.83 3.08 8.86 0.28 15.27 20.32 0.31 0.00 0.00 98.87

2AK14px tr1 50.59 0.60 2.17 8.38 0.33 15.43 20.35 0.13 0.00 0.06 98.04

2AK14px tr1 50.91 0.61 2.17 8.34 0.31 15.78 20.34 0.18 0.00 0.00 98.65

2AK14px tr1 50.95 0.60 2.23 8.12 0.34 15.77 20.09 0.16 0.00 0.00 98.25

2AK14px tr1 51.65 0.62 2.10 8.33 0.28 15.85 20.31 0.12 0.00 0.00 99.26

2AK14px tr1 51.52 0.61 2.18 8.37 0.35 15.73 20.15 0.14 0.00 0.06 99.10

2AK14px tr1 51.53 0.62 2.06 8.32 0.28 15.67 20.17 0.12 0.00 0.01 98.77

2AK14px tr1 50.67 0.63 2.33 8.22 0.30 15.75 20.56 0.26 0.01 0.03 98.74

2AK14px tr1 51.09 0.63 2.34 8.34 0.35 15.45 20.63 0.24 0.00 0.00 99.08

2AK14px tr1 53.16 0.67 2.46 8.53 0.31 16.45 20.23 0.15 0.00 0.00 101.95

2AK14px tr1 51.53 0.62 2.03 8.94 0.44 15.45 20.00 0.18 0.00 0.02 99.20

2AK14px tr1 51.06 0.68 2.08 9.13 0.30 15.44 20.02 0.16 0.01 0.00 98.87

2AK14px tr1 50.99 0.78 2.79 9.43 0.26 15.19 19.61 0.21 0.00 0.03 99.29

2AK14px tr1 51.10 0.72 2.30 9.05 0.30 15.62 19.93 0.30 0.01 0.00 99.33

2AK14px tr1 51.13 0.64 2.21 8.81 0.30 15.47 19.93 0.15 0.00 0.05 98.70

2AK14px tr1 50.57 0.66 2.56 8.99 0.24 15.40 20.20 0.21 0.00 0.00 98.82

2AK14px tr1 51.11 0.74 1.45 12.78 0.46 15.00 17.39 0.16 0.00 0.05 99.15

48

2_AK1XC 1px p15 50.68 0.65 2.31 8.54 0.22 15.50 20.69 0.23 0.00 0.02 98.83

2_AK1XC 1px p17 52.00 0.67 2.24 8.46 0.26 15.65 20.97 0.17 0.00 0.00 100.43

2_AK1XC 1px p18 51.55 0.62 2.41 8.21 0.21 15.31 20.78 0.20 0.01 0.11 99.40

2_AKIXC 1px p19 51.57 0.69 2.04 9.75 0.41 14.92 20.04 0.18 0.00 0.05 99.64

2_AKIXC 1px p20 52.49 0.61 1.83 8.51 0.28 15.88 20.13 0.18 0.00 0.00 99.93

2_AKIXC 1px p21 51.09 0.67 2.08 9.58 0.33 15.26 20.15 0.24 0.00 0.06 99.47

2_AKIXC 1px p22 51.92 0.69 2.05 8.55 0.34 15.78 20.81 0.23 0.00 0.00 100.36

2_AKIXC 1px p23 51.43 0.71 2.27 9.11 0.36 15.31 19.85 0.23 0.00 0.00 99.27

2_AKIXC 1px p24 51.77 0.72 2.27 9.13 0.29 15.72 20.14 0.26 0.01 0.01 100.33

2_AKIXC 1px p25 51.29 0.74 2.49 9.05 0.27 15.35 19.77 0.22 0.00 0.00 99.18

3_AKXIC 04 6px p1 50.80 0.63 2.30 9.46 0.37 15.36 19.79 0.25 0.00 0.00 98.96

3_AKXIC 04 6px p2 51.04 0.75 2.60 9.34 0.32 15.51 19.63 0.14 0.00 0.03 99.37

3_AKXIC 04 6px p3 51.50 0.63 2.20 9.04 0.30 15.51 20.03 0.19 0.00 0.00 99.40

3_AKXIC 04 6px p4 52.17 0.55 1.93 8.82 0.32 16.15 20.00 0.17 0.00 0.00 100.10

3_AKXIC 04 2px p5 51.85 0.49 1.40 8.75 0.56 15.00 20.85 0.19 0.00 0.00 99.08

3 AKXIC 04 2px tr1 52.01 0.54 1.48 8.70 0.44 15.36 20.98 0.21 0.00 0.04 99.76

3 AKXIC 04 2px tr1 51.58 0.54 1.38 8.89 0.46 15.51 20.89 0.21 0.00 0.00 99.45

3 AKXIC 04 2px tr1 50.32 0.67 2.68 8.84 0.47 14.63 21.09 0.26 0.00 0.00 98.95

3 AKXIC 04 2px tr1 51.89 0.53 1.54 8.74 0.54 15.40 20.88 0.18 0.00 0.00 99.69

3 AKXIC 04 2px tr1 51.73 0.47 1.36 8.93 0.52 15.21 20.78 0.30 0.00 0.02 99.34

3 AKXIC 04 2px tr1 51.99 0.59 1.63 8.52 0.42 15.11 20.61 0.15 0.00 0.00 99.02

3 AKXIC 04 2px tr1 49.05 0.70 2.63 8.51 0.48 13.88 20.90 0.18 0.00 0.00 96.33

3 AKXIC 04 2px tr1 51.77 0.55 1.56 9.19 0.44 15.05 20.48 0.16 0.00 0.00 99.20

3 AKXIC 04 2px tr1 51.98 0.44 1.20 9.11 0.50 15.07 20.75 0.26 0.00 0.01 99.32

3 AKXIC 04 2px tr1 51.86 0.58 1.42 8.88 0.57 14.68 20.88 0.23 0.00 0.00 99.10

3 AKXIC 04 2px tr1 51.76 0.45 1.23 9.35 0.60 15.32 20.67 0.24 0.00 0.00 99.61

3 AKXIC 04 2px tr1 53.46 0.43 1.34 8.94 0.50 15.96 20.60 0.22 0.00 0.00 101.45

3 AKXIC 04 2px tr1 51.03 0.75 1.59 11.82 0.41 14.96 18.24 0.18 0.02 0.02 99.01

4_AKXIC 11 p40 52.20 0.63 1.93 9.15 0.27 15.76 19.89 0.26 0.00 0.00 100.08

4_AKXIC 11 p41 51.87 0.60 2.06 8.86 0.28 15.60 20.24 0.10 0.00 0.02 99.62

4_AKXIC 11 p42 52.07 0.56 1.92 8.83 0.32 15.43 20.05 0.21 0.01 0.01 99.40

4_AKXIC 11 p43 51.37 0.73 2.39 9.87 0.35 15.17 19.44 0.20 0.00 0.01 99.54

4_AKXIC 11 p44 51.93 0.68 2.25 8.75 0.24 15.34 20.25 0.22 0.01 0.00 99.68

4_AKXIC 11 p52 52.59 0.53 1.89 9.79 0.38 15.97 18.81 0.23 0.01 0.00 100.19

4_AKXCI 11 p53 52.17 0.61 2.11 9.69 0.29 15.97 19.20 0.21 0.00 0.11 100.36

4_AKXCI 11 p54 52.25 0.62 2.05 9.33 0.33 15.06 19.89 0.21 0.01 0.00 99.76

4_AKXCI 11 p55 52.37 0.63 2.25 9.54 0.38 15.05 19.84 0.25 0.00 0.05 100.35

4_AKXCI 11 p56 52.41 0.82 2.88 10.08 0.31 14.88 18.72 0.20 0.00 0.02 100.33

4_AKXCI 11 p56b 51.75 0.70 2.73 9.80 0.31 15.31 19.42 0.09 0.00 0.02 100.14

4_AKXCI 11 tr2 C-R 52.26 0.63 1.79 8.72 0.46 15.21 20.64 0.23 0.00 0.00 99.93

4_AKXCI 11 tr2 C-R 52.73 0.49 1.61 9.04 0.48 15.14 20.45 0.23 0.00 0.00 100.17

4_AKXCI 11 tr2 C-R 52.25 0.66 2.09 9.47 0.65 14.89 20.09 0.26 0.00 0.00 100.36

4_AKXCI 11 tr2 C-R 51.77 0.57 2.06 9.26 0.52 14.63 20.17 0.18 0.00 0.00 99.17

4_AKXCI 11 tr2 C-R 51.84 0.63 2.04 9.31 0.53 14.52 20.38 0.25 0.00 0.00 99.50

4_AKXCI 11 tr2 C-R 51.88 0.62 1.97 9.24 0.45 14.99 20.25 0.20 0.00 0.00 99.60

4_AKXCI 11 tr2 C-R 52.31 0.56 1.75 9.26 0.48 15.00 20.45 0.24 0.01 0.00 100.05

49

4_AKXCI 11 tr2 C-R 51.92 0.59 1.86 8.69 0.53 14.74 20.79 0.18 0.00 0.00 99.30

4_AKXCI 11 tr2 C-R 51.80 0.54 1.80 8.67 0.51 14.91 20.96 0.22 0.00 0.00 99.43

4_AKXCI 11 tr2 C-R 52.65 0.55 1.88 8.26 0.40 15.09 20.83 0.18 0.00 0.00 99.83

4_AKXCI 11 tr2 C-R 50.96 0.76 2.69 8.69 0.36 14.90 20.85 0.28 0.00 0.03 99.52

4_AKXCI 11 tr2 C-R 51.45 0.82 2.75 8.56 0.33 15.00 20.65 0.18 0.02 0.03 99.79

4_AKXCI 11 tr2 C-R 51.45 0.79 2.73 8.69 0.39 15.23 20.58 0.30 0.00 0.05 100.22

4_AKXCI 11 tr2 C-R 51.23 0.82 2.64 8.87 0.33 15.24 20.73 0.19 0.01 0.00 100.07

4_AKXCI 11 tr2 C-R 52.56 0.55 1.69 8.55 0.41 15.05 20.18 0.19 0.00 0.06 99.23

4_AKXCI 11 tr2 C-R 50.90 0.63 2.02 9.18 0.37 14.65 19.87 0.34 0.00 0.00 97.94

4_AKXCI 11 tr2 C-R 50.92 0.67 2.35 9.39 0.28 15.24 19.80 0.23 0.02 0.06 98.95

4_AKXCI 11 tr2 C-R 51.71 0.71 2.24 8.82 0.27 15.10 20.14 0.14 0.00 0.00 99.12

4_AKXCI 11 tr2 C-R 50.90 0.89 3.16 10.08 0.34 14.65 19.65 0.30 0.00 0.03 100.00

4_AKXCI 11 tr2 C-R 50.45 1.05 2.64 10.88 0.41 14.75 18.46 0.10 0.01 0.00 98.75

50

Appendix 2 – Chemical composition of analysed plagioclase phenocrysts


3_AKXIC 04 1fsp p8 50,25 0,02 30,74 0,62 0,00 0,00 14,56 3,21 0,06 0,00 99,46

3_AKXIC 04 1fsp p9 50,23 0,02 31,03 0,67 0,05 0,00 14,66 3,24 0,08 0,00 99,98

3_AKXIC 04 1fsp p10 52,17 0,04 28,76 0,59 0,00 0,00 12,53 4,50 0,11 0,00 98,70

3 AKXIC 04 2fsp tr2 52,35 0,03 27,85 0,62 0,00 0,00 11,95 4,93 0,12 0,00 97,84

3 AKXIC 04 2fsp tr2 50,92 0,04 29,09 0,62 0,00 0,00 13,08 4,09 0,10 0,01 97,94

3 AKXIC 04 2fsp tr2 50,97 0,08 28,56 0,57 0,02 0,00 12,84 4,25 0,11 0,00 97,39

3 AKXIC 04 2fsp tr2 51,71 0,03 28,24 0,53 0,04 0,00 12,45 4,56 0,10 0,00 97,67

3 AKXIC 04 2fsp tr2 51,79 0,05 28,37 0,57 0,00 0,00 12,42 4,44 0,12 0,00 97,78

3 AKXIC 04 2fsp tr2 52,86 0,01 27,45 0,55 0,00 0,00 11,63 4,90 0,13 0,00 97,53

3 AKXIC 04 2fsp tr2 52,75 0,03 26,92 0,64 0,00 0,00 11,40 5,10 0,13 0,00 96,97

3 AKXIC 04 2fsp tr2 52,26 0,03 28,06 0,63 0,01 0,00 12,35 4,40 0,08 0,00 97,81

3 AKXIC 04 2fsp tr2 53,44 0,02 27,27 0,60 0,02 0,00 11,12 5,21 0,15 0,00 97,82

3 AKXIC 04 2fsp tr2 52,91 0,03 27,51 0,56 0,00 0,00 11,11 5,16 0,14 0,02 97,44

3 AKXIC 04 2fsp tr2 53,03 0,00 27,48 0,57 0,00 0,00 11,27 5,21 0,13 0,00 97,69

3 AKXIC 04 2fsp tr2 52,58 0,02 27,25 0,63 0,00 0,02 11,33 5,12 0,12 0,00 97,07

3 AKXIC 04 2fsp tr2 51,79 0,00 28,44 0,53 0,00 0,00 12,20 4,73 0,10 0,00 97,78

3 AKXIC 04 2fsp tr2 49,56 0,03 29,40 0,72 0,00 0,00 14,05 3,59 0,06 0,00 97,41

3 AKXIC 04 2fsp tr2 50,16 0,06 29,63 0,80 0,00 0,01 13,98 3,61 0,07 0,02 98,34

3_AKXIC 04 2fsp p24 53,77 0,03 28,30 0,60 0,00 0,00 11,77 4,80 0,13 0,02 99,41

3_AKXIC 04 2fsp p26 53,25 0,03 27,88 0,59 0,01 0,00 11,66 4,93 0,12 0,00 98,47

3_AKXIC 04 2fsp p27 52,38 0,02 28,84 0,63 0,01 0,00 12,58 4,41 0,10 0,00 98,98

3_AK1 1 fsp p11 49,11 0,03 30,35 0,59 0,00 0,00 14,72 3,04 0,08 0,02 97,93

3_AK1 1 fsp p12 48,24 0,02 31,81 0,67 0,00 0,00 15,68 2,67 0,02 0,02 99,13

3_AK1 1 fsp p13 50,94 0,06 30,06 0,74 0,00 0,00 13,90 3,84 0,09 0,00 99,62

4_AKLF 1Fsp p1 49,00 0,01 30,27 0,80 0,01 0,00 15,39 2,91 0,08 0,00 98,47

4_AKLF 1Fsp p2 49,84 0,00 30,10 0,72 0,01 0,00 14,82 3,18 0,09 0,00 98,76

4_AKLF 1Fsp p3 48,67 0,03 31,48 0,75 0,00 0,00 15,86 2,56 0,07 0,00 99,42

4_AKLF 1Fsp p5 47,80 0,03 31,83 0,66 0,00 0,00 16,19 2,36 0,03 0,00 98,90

4_AKLF 1Fsp p6 51,49 0,06 29,76 0,76 0,00 0,04 13,57 3,87 0,08 0,00 99,63

4_AKLF 1Fsp p7 53,31 0,06 28,61 0,71 0,04 0,00 12,30 4,71 0,13 0,00 99,86

4_AKLF 1Fsp p8 51,55 0,03 30,15 0,69 0,03 0,00 13,94 3,65 0,08 0,00 100,12

4_AKLF 1Fsp p9 53,29 0,06 29,22 0,73 0,00 0,00 12,83 4,33 0,12 0,00 100,57

4_AKLF p18 52,55 0,02 28,74 0,58 0,00 0,02 12,69 4,44 0,10 0,00 99,15

4_AKLF p19 53,34 0,05 28,77 0,56 0,00 0,00 12,46 4,59 0,13 0,00 99,91

4_AKLF p20 54,16 0,01 28,03 0,66 0,00 0,00 11,45 4,84 0,14 0,01 99,31

4_AKLF p21 50,90 0,02 30,35 0,62 0,00 0,00 13,90 3,57 0,07 0,00 99,44

4_AKLF p22 52,45 0,04 29,20 0,69 0,02 0,00 12,84 4,17 0,10 0,00 99,51

4_AKLF p31 50,24 0,02 30,66 0,54 0,04 0,00 14,37 3,37 0,08 0,00 99,32

4_AKLF p32 49,65 0,02 30,69 0,57 0,00 0,00 14,71 3,32 0,06 0,00 99,03

4_AKLF p33 49,67 0,00 31,33 0,61 0,00 0,00 14,89 2,81 0,07 0,00 99,37

4_AKLF p34 50,27 0,03 30,41 0,63 0,00 0,00 14,23 3,57 0,12 0,03 99,29

51

4_AKXIC 11 p36 47,80 0,01 31,96 0,58 0,00 0,00 16,17 2,18 0,02 0,00 98,72

4_AKXIC 11 p37 48,25 0,01 31,72 0,56 0,02 0,00 15,77 2,34 0,05 0,00 98,71

4_AKXIC 11 p38 50,17 0,01 30,76 0,60 0,00 0,00 14,35 3,33 0,07 0,00 99,30

4_AKXIC 11 p39 52,46 0,05 29,57 0,66 0,00 0,00 13,30 4,05 0,09 0,00 100,18

4_AKXIC 11 p48 50,69 0,04 30,16 0,61 0,01 0,00 14,08 3,72 0,07 0,00 99,39

4_AKXIC 11 p49 51,78 0,03 29,58 0,56 0,00 0,00 13,44 3,90 0,10 0,00 99,38

4_AKXIC 11 p50 52,07 0,04 29,63 0,58 0,00 0,00 13,21 3,98 0,11 0,00 99,62

4_AKXIC 11 p51 53,15 0,04 29,11 0,74 0,00 0,00 12,80 4,19 0,12 0,00 100,16

4_AKXCI 11 tr2 C-R 49,09 0,01 31,63 0,76 0,01 0,00 15,43 2,83 0,04 0,00 99,81

4_AKXCI 11 tr2 C-R 50,85 0,05 29,94 0,58 0,02 0,00 14,06 3,53 0,08 0,00 99,11

4_AKXCI 11 tr2 C-R 50,27 0,03 29,84 0,61 0,00 0,00 14,29 3,29 0,10 0,00 98,44

4_AKXCI 11 tr2 C-R 49,76 0,01 31,00 0,66 0,00 0,00 14,78 3,24 0,07 0,00 99,52

4_AKXCI 11 tr2 C-R 50,74 0,02 30,40 0,76 0,00 0,00 14,19 3,50 0,08 0,00 99,70

4_AKXCI 11 tr2 C-R 50,60 0,05 29,75 0,63 0,00 0,00 14,00 3,63 0,11 0,01 98,77

4_AKXCI 11 tr2 C-R 50,71 0,02 30,49 0,64 0,01 0,00 14,10 3,43 0,06 0,00 99,47

4_AKXCI 11 tr2 C-R 50,33 0,03 30,27 0,68 0,02 0,00 14,69 3,18 0,08 0,00 99,28

4_AKXCI 11 tr2 C-R 48,56 0,02 31,22 0,72 0,00 0,00 15,73 2,59 0,06 0,00 98,91

4_AKXCI 11 tr2 C-R 49,31 0,03 30,74 0,72 0,00 0,00 15,31 2,88 0,06 0,02 99,09

4_AKXCI 11 tr2 C-R 48,22 0,00 31,95 0,70 0,00 0,00 16,13 2,28 0,06 0,01 99,36

4_AKXCI 11 tr2 C-R 48,73 0,00 31,40 0,75 0,00 0,00 15,75 2,55 0,05 0,00 99,22

4_AKXCI 11 tr2 C-R 48,66 0,04 30,90 0,72 0,00 0,00 15,56 2,51 0,05 0,02 98,47

4_AKXCI 11 tr2 C-R 48,52 0,01 31,05 0,72 0,01 0,00 15,68 2,41 0,03 0,02 98,45 4_AKXCI 11 tr3 C-R 56,48 0,04 26,36 0,54 0,00 0,00 10,10 5,95 0,18 0,00 99,66

4_AKXCI 11 tr3 C-R 56,17 0,05 26,12 0,47 0,00 0,00 10,14 5,65 0,19 0,00 98,78

4_AKXCI 11 tr3 C-R 56,10 0,04 26,81 0,52 0,00 0,00 10,56 5,72 0,17 0,01 99,92

4_AKXCI 11 tr3 C-R 55,80 0,03 26,53 0,51 0,00 0,00 10,61 5,68 0,17 0,00 99,33

4_AKXCI 11 tr3 C-R 54,85 0,03 26,97 0,53 0,00 0,00 11,04 5,39 0,14 0,05 98,99

4_AKXCI 11 tr3 C-R 54,86 0,04 27,10 0,47 0,00 0,00 10,93 5,15 0,15 0,00 98,69

4_AKXCI 11 tr3 C-R 55,09 0,02 27,47 0,54 0,00 0,01 11,12 4,96 0,16 0,03 99,40

4_AKXCI 11 tr3 C-R 54,65 0,05 27,46 0,50 0,02 0,00 11,24 5,09 0,12 0,01 99,13

4_AKXCI 11 tr3 C-R 54,48 0,02 26,70 0,45 0,00 0,00 11,19 5,12 0,14 0,00 98,10

4_AKXCI 11 tr3 C-R 54,58 0,06 27,15 0,55 0,00 0,00 11,30 5,22 0,11 0,00 98,96

4_AKXCI 11 tr3 C-R 55,05 0,08 26,82 0,43 0,00 0,00 11,31 5,04 0,13 0,00 98,84

4_AKXCI 11 tr3 C-R 54,63 0,03 26,61 0,49 0,01 0,00 11,20 5,20 0,13 0,00 98,31

4_AKXCI 11 tr3 C-R 54,49 0,05 27,41 0,58 0,04 0,00 11,22 5,21 0,18 0,01 99,18

4_AKXCI 11 tr3 C-R 55,03 0,01 27,23 0,56 0,00 0,00 10,99 5,39 0,13 0,00 99,34

4_AKXCI 11 tr3 C-R 54,30 0,04 26,54 0,55 0,00 0,00 11,02 5,34 0,15 0,00 97,93

4_AKXCI 11 tr3 C-R 55,80 0,06 27,18 0,59 0,00 0,00 10,93 5,44 0,16 0,00 100,16

4_AKXCI 11 tr3 C-R 55,14 0,03 27,21 0,44 0,02 0,00 10,74 5,55 0,14 0,00 99,27

4_AKXCI 11 tr3 C-R 57,05 0,01 25,77 0,48 0,02 0,00 9,73 6,31 0,20 0,00 99,57

4_AKXCI 11 tr3 C-R 55,13 0,03 26,87 0,48 0,00 0,00 10,87 5,53 0,14 0,00 99,04

4_AKXCI 11 tr3 C-R 54,86 0,02 26,70 0,54 0,00 0,00 11,13 5,37 0,16 0,06 98,83

4_AKXCI 11 tr3 C-R 55,25 0,00 26,90 0,44 0,00 0,00 10,67 5,77 0,16 0,08 99,25

4_AKXCI 11 tr3 C-R 55,25 0,02 26,60 0,52 0,02 0,00 10,70 5,44 0,17 0,00 98,73

4_AKXCI 11 tr3 C-R 56,41 0,02 26,39 0,52 0,00 0,00 10,08 6,03 0,14 0,02 99,62

4_AKXCI 11 tr3 C-R 56,56 0,02 26,07 0,54 0,00 0,00 10,07 5,85 0,19 0,00 99,31

52

4_AKXCI 11 tr3 C-R 55,34 0,00 26,58 0,59 0,00 0,01 10,59 5,48 0,14 0,08 98,82

4_AKXCI 11 tr3 C-R 53,79 0,02 28,20 0,46 0,00 0,00 11,90 4,68 0,10 0,00 99,14

4_AKXCI 11 tr3 C-R 52,94 0,03 28,49 0,57 0,02 0,00 12,64 4,56 0,13 0,00 99,38

4_AKXCI 11 tr3 C-R 53,25 0,04 28,12 0,51 0,02 0,00 12,15 4,53 0,13 0,00 98,75

4_AKXCI 11 tr3 C-R 54,26 0,04 27,04 0,51 0,01 0,00 11,90 4,87 0,11 0,01 98,75

4_AKXCI 11 tr3 C-R 54,73 0,01 27,48 0,53 0,00 0,01 11,47 4,94 0,15 0,00 99,33

4_AKXCI 11 tr3 C-R 53,82 0,05 27,70 0,48 0,00 0,00 12,08 4,66 0,08 0,00 98,87

4_AKXCI 11 tr3 C-R 51,24 0,04 28,81 0,56 0,00 0,00 11,96 4,03 0,10 0,00 96,74

4_AKXCI 11 tr3 C-R 52,90 0,04 27,22 0,54 0,00 0,00 12,04 4,77 0,12 0,00 97,63

4_AKXCI 11 tr3 C-R 54,39 0,04 27,52 0,45 0,00 0,00 11,50 4,96 0,15 0,00 99,00

4_AKXCI 11 tr3 C-R 54,34 0,07 27,65 0,53 0,00 0,00 11,37 5,11 0,14 0,00 99,22

4_AKXCI 11 tr3 C-R 53,84 0,05 27,16 0,67 0,00 0,00 11,82 4,70 0,15 0,00 98,40

4_AKXCI 11 tr3 C-R 54,01 0,05 26,87 0,51 0,02 0,00 11,64 4,96 0,15 0,05 98,27

4_AKXCI 11 tr3 C-R 52,87 0,06 27,63 0,56 0,00 0,01 12,68 4,29 0,11 0,02 98,23

4_AKXCI 11 tr3 C-R 52,45 0,09 27,67 0,57 0,06 0,00 12,67 4,29 0,13 0,00 97,95

4_AKXCI 11 tr3 C-R 53,05 0,01 28,04 0,56 0,00 0,00 12,61 4,47 0,10 0,00 98,85

4_AKXCI 11 tr3 C-R 52,65 0,02 28,02 0,55 0,01 0,00 12,57 4,43 0,13 0,00 98,37

4_AKXCI 11 tr3 C-R 48,15 0,06 26,71 0,64 0,00 0,00 12,27 3,52 0,09 0,05 91,47

4_AKXCI 11 tr3 C-R 54,10 0,06 29,01 0,50 0,00 0,00 12,42 4,55 0,12 0,02 100,78

4_AKXCI 11 tr3 C-R 51,52 0,03 29,43 0,58 0,03 0,00 13,66 3,59 0,08 0,01 98,93

4_AKXCI 11 tr3 C-R 54,60 0,03 27,65 0,53 0,00 0,00 11,58 4,90 0,15 0,00 99,43

4_AKXCI 11 tr3 C-R 53,42 0,07 28,03 0,54 0,00 0,00 12,08 4,81 0,10 0,00 99,05

4_AKXCI 11 tr3 C-R 51,06 0,06 25,88 0,57 0,00 0,00 11,59 4,38 0,14 0,01 93,69

4_AKXCI 11 tr3 C-R 55,54 0,04 27,06 0,54 0,00 0,00 10,85 5,49 0,17 0,01 99,71

4_AKXCI 11 tr3 C-R 53,01 0,05 27,67 0,53 0,00 0,00 12,04 4,63 0,14 0,00 98,07

4_AKXCI 11 tr3 C-R 53,94 0,02 27,14 0,55 0,00 0,00 11,31 5,11 0,10 0,01 98,18

4_AKXCI 11 tr3 C-R 55,27 0,07 27,12 0,47 0,00 0,00 11,07 5,23 0,15 0,00 99,39

4_AKXCI 11 tr3 C-R 53,24 0,07 27,87 0,59 0,04 0,00 12,17 4,47 0,11 0,00 98,56

4_AKXCI 11 tr3 C-R 52,59 0,06 28,17 0,66 0,00 0,00 12,75 4,06 0,11 0,00 98,41

4_AKXCI 11 tr3 C-R 53,53 0,05 27,73 0,72 0,01 0,00 12,12 4,70 0,13 0,00 98,98

4_AKXCI 11 tr3 C-R 52,87 0,09 27,64 0,59 0,00 0,00 12,39 4,64 0,14 0,00 98,35

4_AKXCI 11 tr3 C-R 52,23 0,02 27,86 0,66 0,05 0,00 12,84 4,16 0,11 0,00 97,93

4_AKXCI 11 tr3 C-R 53,09 0,05 28,00 0,75 0,01 0,00 12,76 4,40 0,13 0,00 99,18

53

Appendix 3 – Chemical composition of analysed olivine


AK-LF7-PX p19 37.92 0.03 0.00 26.59 0.54 36.72 0.16 0.00 0.00 0.00 101.95

3_AKXIC 04 p28 36.47 0.00 0.00 25.92 0.49 35.63 0.17 0.00 0.02 0.01 98.71

3_AKXIC 04 p29 37.28 0.02 0.00 26.28 0.44 36.05 0.16 0.00 0.00 0.01 100.25

3_AKXIC 04 p30 37.10 0.03 0.00 25.94 0.50 35.37 0.19 0.00 0.00 0.05 99.18

3_AKXIC 04 p33 36.61 0.03 0.00 28.88 0.53 33.41 0.20 0.00 0.00 0.00 99.66

3_AKXIC 04 p34 38.40 0.00 0.03 22.29 0.38 39.94 0.19 0.00 0.00 0.06 101.29

3_AKXIC 04 p35 37.08 0.02 0.00 25.23 0.42 36.73 0.21 0.00 0.00 0.00 99.70

3_AKXIC 04 p36 36.29 0.13 0.02 32.52 0.61 31.32 0.24 0.00 0.00 0.03 101.17

4_AKLF p10 39.29 0.00 0.03 19.20 0.36 41.43 0.17 0.00 0.00 0.00 100.49

4_AKLF p11 39.68 0.06 0.00 18.96 0.29 41.51 0.19 0.00 0.00 0.02 100.70

4_AKLF p12 39.14 0.01 0.00 20.34 0.38 40.31 0.16 0.00 0.00 0.00 100.34

4_AKLF p13 37.75 0.01 0.00 22.08 0.36 38.88 0.15 0.00 0.01 0.02 99.25

4_AKLF p14 37.41 0.00 0.03 24.83 0.47 36.39 0.20 0.00 0.00 0.00 99.34

4_AKLF p27 37.25 0.05 0.02 27.66 0.72 33.87 0.20 0.00 0.00 0.00 99.77

4_AKLF p28 37.28 0.03 0.00 27.95 0.63 33.29 0.18 0.00 0.01 0.00 99.35

4_AKLF p29 37.10 0.03 0.00 29.70 0.68 32.79 0.25 0.00 0.01 0.05 100.59

4_AKXCI 11 p59 37.39 0.00 0.03 29.93 0.63 32.54 0.17 0.00 0.00 0.01 100.68

4_AKXCI 11 p60 37.83 0.00 0.08 27.39 0.49 35.06 0.16 0.00 0.00 0.00 101.01

4_AKXCI 11 p61 37.43 0.01 0.00 29.32 0.50 33.74 0.17 0.00 0.00 0.00 101.17

54

Appendix 4 – Chemical composition of analysed orthopyroxene


AK-LF7-PX p20 54.16 0.20 0.69 16.99 0.48 26.48 1.68 0.00 0.00 0.00 100.67

2_AK14px p3 53.43 0.31 1.00 16.51 0.53 25.99 1.72 0.00 0.00 0.00 99.48

2_AK14px p4 53.88 0.28 0.96 16.88 0.57 25.84 1.63 0.00 0.00 0.00 100.03

3_AK1 1 9px p17 52.16 0.42 0.67 20.50 0.67 20.25 4.79 0.00 0.01 0.00 99.47

3_AK1 1 9px p18 52.15 0.37 0.79 20.80 0.65 20.81 3.72 0.00 0.00 0.00 99.29

3_AKXIC 04 1 p20 52.21 0.28 0.70 18.59 0.56 24.70 2.07 0.00 0.00 0.04 99.16

3_AKXIC 04 2 p22 51.84 0.46 1.54 18.47 0.60 24.03 2.26 0.00 0.01 0.04 99.24

3_AKXIC 04 2 p23 52.90 0.43 0.76 20.03 0.68 20.76 4.63 0.00 0.00 0.00 100.18

3_AKXIC 04 p31 50.73 0.92 2.08 14.24 0.57 15.57 14.78 0.13 0.01 0.00 99.03

3_AKXIC 04 p32 53.19 0.33 0.75 18.59 0.59 23.86 2.06 0.00 0.01 0.00 99.38

3_AKXIC 04 p37 52.75 0.47 0.83 19.53 0.70 20.68 4.94 0.00 0.02 0.00 99.91

4_AKXCI 11 p63 54.22 0.36 0.73 18.97 0.62 21.89 4.07 0.00 0.00 0.00 100.86

4_AKXCI 11 p64 54.45 0.35 0.65 19.69 0.69 23.44 2.17 0.00 0.02 0.00 101.46

4_AKXCI 11 p65 53.11 0.33 0.81 19.33 0.66 21.73 3.83 0.00 0.03 0.00 99.81

4_AKLF p30 54.35 0.88 2.81 18.86 0.53 17.74 4.06 0.32 0.59 0.02 100.16

4_AKLF p15 46.89 0.44 1.13 23.94 0.63 22.07 4.07 0.00 0.00 0.00 99.17

AK-LF8-PX tr R-R 54.13 0.31 0.96 17.35 0.55 25.90 1.74 0.00 0.00 0.05 100.99

AK-LF8-PX tr R-R 53.65 0.26 0.80 17.40 0.49 26.13 1.69 0.00 0.01 0.01 100.44

AK-LF8-PX tr R-R 54.29 0.23 0.76 16.89 0.44 26.55 1.58 0.00 0.00 0.00 100.74

AK-LF8-PX tr R-R 54.82 0.24 0.74 16.88 0.50 26.23 1.56 0.00 0.00 0.01 100.98

AK-LF8-PX tr R-R 52.93 0.26 0.80 16.76 0.56 26.23 1.65 0.00 0.00 0.00 99.19

AK-LF8-PX tr R-R 53.82 0.23 0.74 17.04 0.49 25.86 1.64 0.00 0.00 0.01 99.83

AK-LF8-PX tr R-R 53.82 0.35 1.39 16.57 0.54 25.54 1.67 0.00 0.00 0.00 99.87

AK-LF8-PX tr R-R 54.12 0.32 1.39 17.34 0.48 25.73 1.68 0.00 0.00 0.00 101.07

AK-LF8-PX tr R-R 54.57 0.33 1.26 17.39 0.50 26.11 1.58 0.00 0.02 0.00 101.77

AK-LF8-PX tr R-R 54.39 0.34 1.22 17.69 0.56 25.53 1.75 0.00 0.02 0.01 101.52

55

Appendix 5 – Chemical composition of analysed titanomagnetite


4_AKLF p16 0.13 10.89 3.39 72.83 0.433843 3.19 0.08 0.00 0.01 3.11 94.06

4_AKLF p17 0.10 12.34 3.69 75.75 0.396398 3.18 0.03 0.00 0.00 0.04 95.52

4_AKLF p35 0.10 10.70 3.15 76.34 0.408019 2.99 0.14 0.00 0.00 0.24 94.06

4_AKXCI 11 p66 0.18 18.43 1.92 72.64 0.463541 1.37 0.14 0.00 0.02 0.05 95.22

56

Appendix 6 – Chemical composition of analysed glass and groundmass

SiO2 TiO2 Al2O3 FeO MnO MgO CaO Na2O K2O Cr2O3 SUM Note

AK-LF6-PX p15 57.28 2.62 12.76 12.76 0.27 1.09 4.57 4.63 1.91 0.00 97.89 1

2_AK12px p11 57.68 1.65 16.29 7.67 0.19 1.26 2.77 7.59 2.04 0.00 97.14 1

3_AK1 1 fsp p14 64.83 1.08 16.18 4.60 0.07 0.25 4.72 5.28 1.80 0.01 98.82 1

3_AKXIC 04 2fsp p25 61.31 1.92 9.91 11.29 0.23 1.91 3.50 3.99 2.92 0.02 97.01 1

3_AKXIC 04 2px p7 63.31 1.75 13.84 7.43 0.20 0.72 3.90 4.95 2.15 0.00 98.26 1

4_AKLF p23 60.86 1.63 11.11 10.44 0.22 3.51 4.62 2.96 2.68 0.00 98.03 1

4_AKLF p24 63.86 1.34 13.84 7.07 0.14 1.87 2.73 4.10 3.41 0.05 98.41 1

3_AK1 1 fsp p15 66.35 1.40 12.61 6.54 0.13 0.85 3.10 4.96 1.88 0.02 97.84 2

3_AK1 1 fsp p16 68.41 1.51 12.15 6.69 0.13 0.82 3.06 3.63 1.63 0.00 98.04 2

3_AKXIC 04 p19 67.93 1.61 12.36 4.95 0.11 0.42 3.11 2.73 2.54 0.00 95.78 2

3_AKXIC 04 p21 68.44 1.84 11.65 5.94 0.13 0.30 2.77 3.99 3.19 0.00 98.25 2

2_AK14px p7 60.46 0.67 19.37 3.99 0.09 0.87 6.31 5.22 1.40 0.00 98.38 3

2_AK12px p14 62.36 0.87 18.59 4.22 0.08 0.33 5.78 5.27 1.53 0.01 99.05 3

2_AKIXC 1px p26 59.82 0.68 18.10 4.20 0.06 0.73 7.51 4.90 1.04 0.00 97.04 3

2_AKIXC 1px p27 57.66 0.50 20.90 2.57 0.05 0.26 9.00 4.99 0.67 0.00 96.61 3

AK-LF 3-PX p8 57.49 1.49 16.08 8.08 0.11 1.65 6.51 4.62 1.52 0.00 97.54 3

AK-LF 3-PX p9 57.84 1.36 15.54 7.89 0.11 2.53 6.50 4.73 1.43 0.00 97.93 3

2_AK14px p6 62.72 1.10 14.46 7.40 0.21 2.17 4.95 4.94 1.79 0.01 99.75 3

2_AKIXC 1px p28 59.99 0.92 15.03 6.23 0.15 2.39 6.16 4.41 1.30 0.00 96.57 3

4_AKXIC 11 p45 64.50 2.14 11.50 10.20 0.20 1.84 3.30 4.20 2.79 0.00 100.67 3

4_AKXIC 11 p46 61.55 3.00 13.07 12.08 0.11 1.07 3.16 4.44 2.26 0.00 100.76 3

4_AKXCI 11 p57 63.37 0.00 15.34 8.17 0.13 1.11 4.53 4.84 1.88 0.00 99.37 3

4_AKXCI 11 p58 63.09 1.24 13.64 6.53 0.12 1.30 4.90 4.60 2.26 0.00 97.68 3

4_AKLF p25 58.11 1.54 12.75 11.32 0.25 4.62 6.01 3.66 1.44 0.00 99.69 3

4_AKLF p26 58.77 2.10 14.28 11.78 0.19 2.14 5.25 4.72 1.71 0.05 100.98 3

1: Melt inclusions

2: Groundmass glass

3: Groundmass

Tidigare utgivna publikationer i serien ISSN 1650-6553

Nr 1 Geomorphological mapping and hazard assessment of alpine areas inVorarlberg, Austria, Marcus Gustavsson

Nr 2 Verification of the Turbulence Index used at SMHI, Stefan Bergman

Nr 3 Forecasting the next day’s maximum and minimum temperature in Vancouver,Canada by using artificial neural network models, Magnus Nilsson

Nr 4 The tectonic history of the Skyttorp-Vattholma fault zone, south-central Sweden,Anna Victoria Engström

Nr 5 Investigation on Surface energy fluxes and their relationship to synoptic weatherpatterns on Storglaciären, northern Sweden, Yvonne Kramer

Nr 183 Taking the Temperature & Pressure on Dannemora, Michaela Åberg. December 2009

Nr 184 Klimatologisk analys av mätningar från Abisko för den inre snöstruturen, Bilyan Mladenov. December 2009

Nr 185 Processing Techniques of Aeromagnetic Data. Case Studies from the Precambrian ofMozambique, Luís André Magaia. December 2009

Nr 186 10Be in Greenland Ice Cores, Anna Sturevik Storm. January 2010

Nr 187 Lithospheric-Scale Stresses and Shear Localization Induced by Density-Driven Instabilities, Christiane Heinick. March 2010

Nr 188 Atmosfärens gränsskikt över land och hav, Annika Hjelmsten. April 2010

Nr 189 Oxidationsfenomen i några svenska kopparmalmer – en betraktelse över sambandet-mellan texturer och bildningsmiljö, Per Carlsson. April 2010

Nr 190 Utvärdering av automatiska snödjupsmätningar med en SR50A Sonic RangingSensor, Nicole Carpman. April 2010

Nr 191 Uppskattning av vindklimat – Implementering och utvärdering av en metod förnormalårskorrektion, Irene Helmersson. April 2010

Nr 192 Orografins påverkan på åska i Värmland under 2009, Elisabeth Saarnak. May 2010

investigating magma plumbing beneath anak krakatau volcano

Documents