UNIVERSITY OF GOTHENBURG Department of Earth Sciences Geovetarcentrum/Earth Science Centre

ISSN 1400-3821 B 615 Bachelor of Science thesis Göteborg 2010

Mailing address Address Telephone Telefax Geovetarcentrum Geovetarcentrum Geovetarcentrum 031-786 19 56 031-786 19 86 Göteborg University S 405 30 Göteborg Guldhedsgatan 5A S-405 30 Göteborg SWEDEN

Origin of hornblendites in the Routevare Anorthosite

Complex, Northern Scandinavian Caledonides

Fredrik Schenholm

Origin of hornblendites in the Routevare Anorthosite Complex, Northern Scandinavian Caledonides.

Fredrik Schenholm, Gothenburg University, Department of Earth Science, Geology, Box 460, SE-405 30

Göteborg

Abstract

Since the discovery of the anorthosites, no proposed theory of its origin has been widely accepted. It is called

“the anorthosite problem”. This bachelor thesis focused on the crystallization sequence and origin of the

enclosed hornblendite body in the Swedish Routevare Anorthosite Complex, but it could also improve the

understanding of “the anorthosite problem”. Three samples from the hornblendite body were closely examined at

the Geovetarcenturm in Gothenburg using optical microscope, scanning electron microscope and geochemical

data. The samples showed variation in composition and the rock types were determined to hornblendite and

pyroxene hornblendite. Oikiocrystic and poikilitic textures as well as the absence of deformation textures

indicate magmatic origin with a crystallization sequence of the most representative minerals: Pyroxene and

spinels →High Ti- hornblende→Ti free- hornblende and opaque minerals. Alteration and secondary minerals are

frequent, most likely representing retrograded metamorphose. The mineral assemblage of clinopyroxens and

spinels suggest a minimum crystallization pressure and temperature of 1440° and 3Gpa to 1480° and 2 Gpa. The

aluminum and titanium content in the hornblende were used as a geothermobarometer suggesting exsolvation of

ilmenite “needles” as the pressure decreased from pressure decreased from ~1.1 Ga to ~0.9 Ga and the

temperature increased from ~700ºC to ~925ºC. Areas with decreasing pressures and increasing temperatures are

observed in subduction related mantle wedge regions.

Key words: Routevare Anorthosite Complex, hornblende, hornblendite, optical microscopy, aluminium/titanium-

geothermobarometer

ISSN 1400-3821 B615 2010

Hornblenditers ursprung i Routevare Anorthosite Complex, norra delen av skandinaviska

Kaledoniderna.

Fredrik Schenholm, Göteborgs Universitet, Instutitionen för Geovetenskaper, Geologi, Box 460, 405 30

Göteborg

Sammanfattning

Det finns ingen accepterad teori om anortositerna ursprung. Detta kallas för ”det anortositiska problemet”.

Denna kandidatuppsats har fokuserat på kristallisationssekvensen och ursprunget av en innesluten

hornblenditkropp från svenska Routevare Anorthosite Complex, men kan möjligen också öka förståelsen för

anortositernas ursprung. Tre prover från hornblenditkroppen undersöktes på Geovetarcentrum i Göteborg med

hjälp av optiskt mikroskop, elektronmikroskop och geokemisk data. Proverna varierade i sammansättning och

bergarterna klassificerades till hornblendit och pyroxen hornblendit. Oikocrystiska och poikilitiska texturer samt

frånvaron av deformationstexturer tyder på ett magmatsikt ursprung. Kristallisationssekvens av

huvudmineralerna är: Pyroxen och spinel → Ti-rikt hornblend→Ti- fattigt hornblend och opaka mineraler.

Metamorfa mineraler är vanliga vilket mest sannolikt tyder på en retrograd metamorfos. Mineralerna

clinopyroxen och spinel indikerar en kristallisationsminimum temperatur och tryck på 1440° och 3Gpa till 1480°

och 2 Gpa. Aluminium- och titaninnehållet i hornblendet användes som en geotermobarometer där utfällningen

av illmenite nålar förmodligen skedde vid tryckminskningen ~1.1 Ga till ~0.9 Ga och temperatursökningen från

~700ºC to ~925ºC. Områden med fallande tryck och stigande temperatur är observerade i mantelkilzoner i

subduktionsmiljöer.

Nyckelord: Routevare Anorthosite Complex, hornblende, hornblendit, optiskt mikroskopering, aluminium/titan-

geotermobarometer

ISSN 1400-3821 B615 2010

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Table of content 1. Introduction 3

2. Geological setting 3

2.1 Proterozoic Massive Type Anorthosites 3

2.2 The Routevare Anorthosite Complex 3

2.2.1 The anorthosite of RAC 4

2.2.2 The hornblendite body of the RAC 4

2.2.3 The gabbro body of the RAC 5

2.2.4 The peridotite body of the RAC 5

3. Methods 6

3.1 Collecting samples in field 6

3.2 GCD-kit 6

3.3 Optical microscopy 7

3.4 Preparation for Scanning Electrom Microscope 7

3.5 SEM 7

3.6 Mineral formula recalculation 7

3.7 Pressures and temperatures 7

4. Results 8

4.1 Description of hand samples 8

4.2 Rock classification 8

4.3 Alteration diagram 9

4.4 Spider- and REE diagram 10

4.5 Thin section texture description in optical microscope 12

4.5.1 L78:79 13

4.5.2 L84:25 14

4.5.3 L78:81 16

4.6 Rock types 17

4.7 SEM and mineral formula recalculation 17

4.8 Pressures and temperatures 20

4.9 Crystallization sequence and P/T path 21

5. Discussion 23

5.1 Rock type 23

5.2 Magmatic origin 23

5.3 Crystallization sequence 23

5.4 Tectonic setting 24

5.5 Pressures and temperatures 24

5.6 Further investigations 25

6. Conclusion 26

7. Acknowledgment 26

8. References 27

Appendix

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1. Introduction The Routevare Anorthosite Complex (RAC) in the Northern part of the Swedish Caledonides

hosts several isolated bodies of pyroxenite, peridotite, gabbro and hornblendite (Björklund,

1994). The aim of this study is to investigate samples from the isolated hornblendite body to

answer questions as:

- What is the rock type of the hornblendite body?

- What is the crystallization sequence of the samples?

- What is the origin and tectonic setting of the hornblendite body?

2. Geological setting 2.1 Proterozioc Massive Type Anorthosites

Proterozioc massif type anothosites (PMTA) comprises the most voluminous anorthosites on

Earth. The origin, petrogenesis and tectonic setting of PMTAs have been suggested for many

localities such as Greenville Province and Eastern Ghats of India. Ashwal (1993) presents a

plausible model based on available data, clues and ideas from earlier models regarding the

PMTAs petrogenisis. A basaltic melt goes through fractional crystallization and ponds up

deep in the crust. The mafic silicates sink and the crystallized plagioclases forms flotation

cumulates ascending through the crust as buoyant anorthositic mushes. Massifs forms in the

upper crust due to the ascending plagioclase- rich diapirs that coalesce together, to form an

anorthosite complex.

The tectonic settings of the PMTA’s are unknown, although there are several proposed

feasible models. It is likely that anorthosites are a product of basaltic magmatism making

many of today’s tectonic settings a potential source of origin and formation. Data indicates

subduction related tectonic settings such as; continental collisions, subduction, back arc

extension, ridge subduction and rifts, but any of these settings are to a varying degree

compatible with existing data (Ashwal, 1993).

2.2 The Routevare Anorthosite Complex

The Routevare Anorthosite Complex (RAC) is a Fe- Ti PMTA differentiated complex located

in the Swedish part of the Caledonian orogenic belt occupying an area of 76km2

north of

Kvikkjokk (Björklund, pers. com.). RAC is a part of Tielma Magmatic Complex (TMC)

(Rehnström, 2003).TMC shows similar lithologies, trace element composition and rare earth

element patterns as the AMCG (anorthosite- mangerite- charnockite- granite)- suite of the

Lofoten Complex which could indicate a common source and/or process of formation. U-Pb

age determinations on zircons of syenite samples constrain the timing of the magmatic

activity in the TMC to between ~1.78- 1.76 Ga (Rehnström, 2003).

During the formation of the Caledonian orogenic belt, around 420 Ma, major nappe

complexes were thrusted in a general easterly to south-easterly direction over the Baltica

craton as a consequence of continent-continent collision between Baltica and Laurentia

(Rehnström, 2003). The tectonostratigraphy of the Scandinavian Caledonides is traditionally

divided into four major allochthons; the Lower, Middle, Upper (Seve and Köli Nappe

Complexes) and Uppermost Allochthons (Fredén, 2002), in increasing order of thrust

distance.

The RAC is located along the base of the Seve Nappe Complex where several isolated bodies

of layered gabbro, peridotite and hornblendite occur within the main anorthosite complex (fig

1). These rocks restores to the pre- collisional western margin of Baltica. The primary

mineralogy is to a varying degree regionally altered to amphibolite grade, and along the

4

Caledonian main thrusts and local shear zones retrograded to greenschist grade (Björklund,

1994).

Fig 1. The location of the hornblendite body. Reproduced from Björklund (1994).

2.2.1 The anorthisite of the RAC

The anorthosite varies in modal composition, from gabbroic anorthosite composed of 40%

mafic minerals to pure anorthosite almost devoid of mafic minerals. The pure anorthosite is

characterized by the white color due to the seriticized large plagioclase crystals. When

sheared, these rocks show a foliated, mylonitic and fine grained texture.

2.2.2 The hornblendite body of the RAC

An elongated body, 3.000 m long and up to 500 m wide, of black hornblendite strikes from

WNW to ESE, completely enclosed by anorthosite. The body is bone-shaped with a narrow

centre and wider ends. The centre shows foliation due to deformation while the ends show

5

“massive”, primary texture, a homogenous texture without preferred crystal orientation or

stratification. Plagioclase occurs only very locally and subordinately within the hornblendite

body, which thus classifies as ultramafite. The composition varies between hornblendite and

pyroxene hornblendite but will hereby be referred as the hornblendite body.

2.2.3 The gabbro bodies of the RAC

Several bodies of gabbroic composition, with a maximum length of 1.000 m and width of 800

m, occur as isolated lensoids. The bodies show felsic to mafic composition, partly with modal

rhythmic layering cut by pyroxenite and syenite intrusions.

2.2.4 The peridotite body of the RAC

An elongated body, 1.700 m long and up to 200 m wide, of olivine- rich peridotite strikes in

the same direction as the hornblendite body from WNW to ESE. The peridotite body is

located 7 km NW of the hornblendite body.

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3. Methods 3.1 Collecting samples in the field

In 1978, Geological Survey of Sweden (SGU) employed Lennart Björklund, to sample the

anorthosite in the Routevare area to investigate the possibility of leaching Aluminum. The

area appeared to be of interest for science and Mr Björklund made complementary sampling

including the mafic rocks in 1984 and 1985.

The samples, named hornblendite, were collected in situ with a sledge hammer weighing 6 kg.

The sample sites were critically chosen with the least amount of visible deformation and

metamorphic imprint as possible. This often correlates with the central parts of the mafic

bodies.

The hornblendite samples used for analyses were L78:79, L78:81 and L84:25. Samples

L78:79 and L84:25 were collected from the north- western part of the hornblendite body,

sample L78:81 from the south -eastern part (fig 2).

Fig 2. Sample locations from the hornblendite body in the Routevare area. Figure 1 shows a more detailed map

regarding the bedrock in the area. Reproduced from Björklund (1994).

3.2 GCD-kit

To classify the different rock types and to identify a possible tectonic setting of the samples,

the software GCD-kit version 2.3 was used. Geochemical data were available (Björklund,

7

pers. com) (appendix 1), both for the hornblendite samples as well as additional samples from

the other rocks of the RAC.

3.3 Optical microscopy

Optical microscopy was carried out at Geovetarcentrum (GVC) in Gothenborg using a Leica

DMLP microscope in combination with an Olympus DP71 camera and the software Cell B.

The mineralogy of the samples were determined by using plane and crossed polarized light,

pleochrosim, extinction angles, interference color charts and opaque microscopy. Special care

was taken mapping the minerals textural spatial relations, the alteration grade and to

distinguish primary and secondary minerals.

3.4 Preparation for the Scanning Electron Microscope

To make orientation easier in the Scanning Electron Microscope (SEM), the areas of interest

were marked on the thin section samples while working with the optical microscopy. Before

starting the SEM analyses the thin sections were scanned and printed on paper to make the

orientation in the SEM easier. As a final step the thin section were coated with coal.

3.5 SEM

Mineral microchemistry was determined at the GVC, using a Hitachi SEM. The specimen

current was set to approximately 3.5 nA, the accelerating current to 20kV and the EDS

detector dead time of approximately 50%. The SEM-EDS offers the possibility to determine

the actual composition of crystals, to confirm the optical microscopy observations, to

determine the compositions of the exsolved lamellas in the pyroxenes, the opaque mineral

assemblages, and the Fe-Ti needle shaped assemblages along the crystal structure of the

hornblendes.

3.6 Mineral formula recalculation

To calculate mineral formulas from the chemical analyses, spreadsheets for mineral formula

calculations were used. Mostly for historic reasons, the chemical analyses of silica minerals

are often reported in weight percentages of the oxides of the elements determined. The

calculations follow four steps (serc.carleton.edu, 2009):

1) Dividing the wt% of each oxide by the formula wt% of that oxide.

2) Multiplying the resulting “mole number” of each oxide by the number of oxygen in the

oxide formula.

3) Multiply the resulting “oxygen number” of each oxide by a normalization constant.

4) Multiply the “normalized oxygen number” of each oxide by the number of cation per

oxygen in the oxide formula.

3.7 Pressure and temperature

To determine a possible pressure and temperature of the magmatic/metamorphic origin of the

samples, known pressure/temperature (P/T) stability fields were used for contents of

coexisiting elements as well as coexisiting minerals.

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4. Results 4.1 Description of hand samples

Only small fragments of the samples remain. They show a blackish color with gray pyroxene

grains enclosed in larger oikocrysts of hornblende. No indications of foliations are observed

and from certain angles the samples show schiller- like reflections similar to labradorescence.

4.2 Rock classification

To classify the rock types, major element chemical data are used (appendix 2) in two different

diagrams. The R1- R2 diagram (De la Roche et al., 1980) recalculates the rock composition as

cations in plutonic rocks, in contrast to the TAS diagram (Cox et al., 1979) using the total

alkalis versus silica in plutonic rocks (Rollinson, 1993). Note that the R1- R2 diagram uses

most of the major elements, while TAS is restricted to alkalis versus SiO2.

The geochemistry of two

samples from the hornblendite/

pyroxene hornblendite body is

available, along with additional

samples from the Routevare

area. In the R1- R2 diagram

(De la Roche et al., 1980) the

hornblendite samples, L78:79

and L78:81, plot in the

ultramafic rock field (fig 3).

According to the International

Union of Geological Science

(IUGS) hornblendite is defined

as ”An ultramafic plutonic rock

composed almost entirely of

hornblende. Now defined

modally in the ultramafic rock

classification.”.

The second diagram applied is

the TAS diagram (Cox et al.

1979), a bivariate oxide – oxide

major element diagram

classifying igneous rocks. This

diagram is straight forward

naming rock types depending

on the relationship in wt%

between the total alkalis (TA) and the SiO2 (S) content. The hornblendite samples, L78:79

and L78:81, are located in the ultramafic field, but no names are applied with this

constellation of major elements (fig 4). One sample shows a greater alkali content, placed to

the right side of the alkaline/subalkaline line.

Fig 3. The samples from the Routevare region plotted in de la Roche’s

et al. (1980) diagram using the parameters R1 and R2, calculated from

millication proportions. R1 = 4S1 – 11(Na + K) – 2(Fe + Ti); R2 = 6Ca

+ 2Mg + Al (Rollinson, 1993). The two hornblendite samples plot

correctly in the ultramafic section (data Björklund, appendix 2).

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Fig 4. TAS diagram (Cox et al., 1979) using the total alkalis versus silica to classify and name plutonic rocks.

The curved line differs alkaline from subalkaline rocks (Rollinson, 1993). The hornblendite samples classify as

ultrabasic rocks but no names are given with this major element composition.

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4.3 Alteration diagram

To examine chemical alteration of igneous samples Hughes diagram (1972) was used. The

two samples, L78:79 and L78:81, plot in the mildly K-altered field (fig 5). Plots involving

mobile elements such as K need to be interpreted accordingly.

Fig 5. Hughes diagram (1972) show alteration regarding Na/K. Both hornblendite samples show an alteration of

K.

4.4 Spider- and REE diagram

Possible source environments of magmas or indication of magma mixing or magma

fractionation, may be distinguished by patterns of trace element concentrations in Spider- and

REE diagrams (Blatt et al., 2006). In the Spider diagram the two hornblendite samples,

L78:79 and L78:81, show similar trends for the mobile elements (LIL- elements = Sr- Ba) as

in the immobile elements (HFS- elements = Th- Yb), except for a higher concentration of

Niobium (Nb) in the L78:81 sample compared to the L78:79 sample. Characteristic for both

samples are the depletion in Phosphorus (P) (fig 6), in contrast to other mafic samples as

samples “Gabbro, Pl-Am-Mt” and “Ol- Ti- Mt ore”. The general trend of enrichment of the

LIL- elements compared to the HFS- elements could indicate a subduction zone magma

generated by the transport of fluid- soluble elements into the mantle wedge region (Tatsumi et

al., 1995).

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Fig 6. Spider diagram showing the trace element concentrations of the Routevare samples. The diagram is

normalized to the composition of average MORB (Pearce, 1983).

The REE diagram also shows similar trends for the hornblendite samples, except for an

increasing concentration of Europium (Eu) and a decreasing concentration of Ytterbium (Yb)

in the L78:79 sample compared to the L78:81 sample (fig 7). The general trends of the

samples show an increasing concentration of the middle- REE elements with decreasing

concentrations of light- and heavy REE elements. The trend of the hornblendite samples

resembles the trend of the ultramafic pyroxenite samples, but with a higher REE- content. The

hornblendite samples show no similarities with other mafic samples.

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Fig 7: REE diagram normalized to REE chondrite (Boynton, 1984). The hornblendite samples show the same

trends with increasing concentrations of middle- REE and decreasing concentrations of the light- and heavy

REE.

4.5 Thin section texture descriptions in optical microscopy

Three thin sections; L78:79, L84:25 and L78:81 from the hornblendite body are described

below based on optical microscopy observations (table 1).

L78:79 L84:25 L78:81

50- 90% Hornblende Hornblende Hornblende

<50% Clinopyroxene Clinopyroxene Clinopyroxene

Orthoyroxene Orthopyroxene Orthopyroxene

<5% Opaque minerals Opaque minerals Opaque minerals

<1% Garnet

Apatite

Biotite

Calcite

Chlorite

Serpentine

Spinel

Chlorite

Relict Garnet

Spinel

Table 1. A summary of the mineral assemblages of the thin sections.

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4.5.1 L78:79

Pyroxene

Pyroxene is present as clinopyroxene (cpx) and orthopyroxene (opx) as anhedral to subhedral

grains with a diameter less than 1 mm. Cpx is more frequent then opx. A majority of the cpx

show internal patches replaced by hornblende (fig 8). The pyroxenes occur in a poikilitic

texture with cpx and opx enclosed in the hornblende crystals (fig 9). The pyroxenes constitute

less than 10% of the thin section.

Fig 8. A cpx showing internal patches replaced by

hornblende (hbl). Plane polarized light. Fig 9. Cpx enclosed in hornblende (hbl). Crossed

polarized light.

Hornblende

Hornblende makes up the largest volume

occupying approximately 90%. The crystal

size varies from subhedral crystals with a

length of 14 mm to anhedral crystals of 1.5

mm. Inclusions of cpx and opx are common,

as well as fractures along the cleavage planes.

Biotite along with unidentified minerals

occupies several of the fractures. A majority

of the cpx are partly replaced by irregular

patchy hornblende. A common feature of all

hornblende crystals are the presence of

pigmentation of dust like particles of Fe- Ti

oxides, elongated needles of Fe- Ti oxides

along the cleavage planes and assemblages of

opaque minerals (fig 10).

Opaque minerals

Several generations of opaque minerals are observed. One generation appear to be co-

crystallized with the hornblende, producing needle shaped Fe- Ti oxides with a maximum

length of 50 μm along the cleavage planes within the hornblende (fig 10). A later generation

appears to be the dust like particles of Fe- Ti oxides ubiquitously pigmenting the hornblendes.

The Fe- Ti oxide needles and the pigmented Fe- Ti dust like oxides are frequently absent

along the boundaries of the hornblende crystals. A third generation are blocky opaque mineral

Fig 10. Pigmentation of dust like particles of Fe- Ti

oxides are shown as sub- vertical stripes on the left

side. The right side shows the elongated needle

shaped Fe- Ti oxides. Plane polarized light.

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assemblages enclosed and/or exsolved in the hornblende. A red, unidentified mineral is

associated with the opaque minerals.

Biotite

Subhedral biotite grains with a maximum length of 0.4 mm are located in fractures along the

cleavage planes within the hornblende. Minor amounts of biotite are also observed in larger

fractures between hornblende crystals. Biotite is an accessory mineral.

Apatite

Minor amounts of apatite crystals are enclosed in the hornblende. Apatite is an accessory

mineral.

Calcite

Calcite is an accessory mineral located along fractures in the hornblende grain boundaries.

Serpentinite

Serpentinite is an accessory mineral in fractures along hornblende grain boundaries.

Interpreted crystallization sequence

Pyroxenes were the first minerals to crystallize suggested from the poikilitic texture. Second

mineral to crystallize were the hornblende, indicated by the oikocrystic texture. Three

generations of opaque minerals are observed, with the Fe- Ti needle shaped oxides as the first

generation, exsolved along the hornblende’s cleavage planes. The second generation is the

pigmented Fe- Ti dust like oxides. Clear margins occasionally embrace the blocky Fe- Ti

oxides. This could indicate that these blocky assemblages originate from the Fe- Ti needles

and Fe- Ti pigmentation, making this the third generation. Calcite and serpentinite suggests

being metamorphic minerals due to retrograded metamorphose.

4.5.2 L84:25

Pyroxene

Pyroxene is present as cpx and opx. The

anhedral crystals with a maximum length of 4

mm are strongly altered to chlorite and

epidote, both within and along the crystal

boundaries. Internal patches within the

crystals are partly replaced by hornblende.

Pyroxenes are often mantled and corroded by

hornblende (fig 11). Fractures are common,

often exhibiting replacement by hydrous

minerals such as chlorite and hornblende.

Spinel

Green spinel is closely associated with the

opaque mineral assemblages, easily observed

in plane polarized light showing the

characteristic green colour (Fig 12). An

estimated occurrence is a minimum of 1%. The maximum size of the crystals 0,8 mm in

length. The intensity of the green colour varies in the spinels. Some of the crystals show black

lamellas.

Fig 11. Hornblende (hbl) mantling and corroding cpx

and opaque mineral assemblages (oma). Crossed

polarized light.

15

Hornblende

Anhedral hornblende are frequently mantling and entwining the pyroxenes, and inclusions of

opaque mineral assemblages are common. Several of the pyroxenes show internal patches

replaced by hornblende (Fig 8). More frequent compared to sample L78:79 is the dark

pigmentation of dust like particles of Fe- Ti oxides as well as elongated needles of opaque Fe-

Ti oxides along the cleavage planes. Some grain boundaries are altered to needle shaped

chlorite as well as along several crystal surfaces.

Opaque minerals

Opaque mineral assemblages, with a maximum diameter of 1 mm are common, making up

about 5% of the volume. The assemblages are frequently surrounded by a rim of chlorite

along with unidentified minerals (fig 13). These chlorite rimmed opaque mineral assemblages

commonly occur as inclusions in the hornblende. Another textural generation of opaque

minerals, similar to the L78:79 sample, occur as pigmented dust like particles of Fe- Ti oxides

as well as elongated needles of Fe- Ti oxides along the cleavage planes of hornblende.

Fig 12. Green spinel (sp) enclosed in an opaque

mineral assemblage. The red streak in the centre is a

microscopic refractive error. Plane polarized light.

Fig 13. Chlorite (chl) rimming the opaque mineral

assemblage (oma). Needle shaped chl visible on the

right side of the rim. Crossed polarized light.

Garnet

Garnet is enclosed in the hornblende. The

crystals are commonly strongly altered to

magnetite within the structure while the

borders are altered to calcite and chlorite (fig

14). Garnet is an accessory mineral.

Chlorite

Chlorite is a common secondary product as

rims around the opaque mineral assemblages

(fig 13), along grain boundaries of hornblende

and pyroxene and in fractures of pyroxenes.

Interpreted crystallization sequence

The pyroxenes were the first mineral to

crystallize suggested by hornblendes post-

crystallization texture of the mantling and

corroding of the pyroxenes. Enclosed spinels in the hornblende also suggest pre- hornblende

Fig 14. A garnet (gar) exposed to secondary

processes producing magnetite, calcite and chlorite.

Plane polarized light.

16

crystallization. Out of the three observed generations of Fe- Ti oxides, it is likely the first

generation of Fe- Ti oxides exsolved from the hornblende as needle shaped crystals. The

second generation of the pigmentation of dust like Fe- Ti oxide is suggested to be followed by

the third generation of the Fe- Ti oxide assemblages. Chlorite is an alteration product of

hornblende (Nesse, 2000), most likely from retrograde metamorphism.

4.5.3 L78:81

Pyroxene

A variety of cpx and opx are enclosed in hornblende oikocrysts, mainly as subhedral crystals

with a homogenous size of 2-3 mm. The pyroxenes make up 40% of the volume. Lamellas

and twinning structures are frequent in the cpx (fig 15). The cpx occasionally show alteration

and secondary growth of chlorite along the crystal margins. Fe- Ti oxides are more common

along the cleavage planes and as pigmentation on the crystal structure, compared to the

pyroxenes in previous samples. Cpx is more frequent then opx.

Spinel

Green spinel is typically associated with the opaque mineral assemblages. These assemblages

are enclosed in the hornblende oikocrysts. Some of the crystals show black lamellas. Spinel is

an accessory, but characteristic mineral.

Hornblende

Two large optically continuous oikocrysts of hornblende, making up about 50% of the

volume, enclose the other crystals mainly consisting of cpx, opx and opaque mineral

assemblages. As in samples L78:81 and L84:25, the hornblende is darkened by ubiquitous

pigmented dust like particles of Fe- Ti oxides as well as elongated needles of Fe- Ti oxides

along the cleavage planes. Another generation of Fe- Ti free hornblende is occasionally

observed as anhedral crystals along the boundaries of the pyroxenes (fig 16).

Fig 15. A twinned cpx enclosed in hornblende (hbl).

The dark colour of the hbl is a result of Fe- Ti oxides.

Crossed polarized light.

Fig 16. Fe- Ti free hornblende (hbl) along the grain

boundary of an altered cpx. Plane polarized light.

17

Opaque minerals

As in samples L78:79 and L84:25, several

generations of opaque minerals occur, making

up approximately 10% of the volume. The

hornblende crystals are entirely filled with

elongated needles of Fe- Ti oxides along the

cleavage planes as well as pigmentation of

dust like particles of Fe- Ti oxides. Opaque

mineral assemblages are commonly enclosed

in the hornblende oikocrysts. Inclusions of

spinel and unidentified minerals are common

within these assemblages. Clear margins are

frequently surrounding the assemblages

within the hornblende oikocrysts (fig 17).

Interpreted crystallization sequence

Considering the oikocrystic texture of the

hornblende enclosing the pyroxenes, pyroxenes are likely to have crystallized first, followed

by co- or pre pyroxene crystallized spinels and hornblende. Three generations of opaque

minerals are observed, with the Fe- Ti needle shaped oxides as the first generation, exsolved

along the hornblende’s cleavage planes. The second generation is the pigmented Fe- Ti dust

like oxides. The frequently clear margins embracing the blocky Fe- Ti oxides could indicate

that these blocky assemblages originate from the Fe- Ti needles and Fe- Ti pigmentation,

making this the third generation. The spinels are closely associated with the blocky Fe- Ti

oxide assemblages.

4.6 Rock types

Based on the optical microscopy described above, two rock types are classified. Samples

L78:79 and L84:25, both sampled from the North- west corner of the hornblendite body,

contains 90% respectively 80% of hornblende making L78:79 the only sample classifying as

hornblendite, according to the rock class definition of International Union of Geological

Science. Sample L78:81 is sampled from the North- east corner of the hornblendite body

containing 50% of hornblende. The high proportions of pyroxenes therefore classify samples

L78:81 and L84:25 as pyroxene hornblendite.

4.7 SEM and mineral formula recalculation

Pyroxene

The most representative and frequent cpx is diopside, occasionally showing lamellas of

exsolved hypersthene (table 2)(appendix 1, site 21 and 21). Hornblende commonly hosts the

cleavage planes of the diopside (fig 18).

Wollastonite Enstatite Ferrosilite

Diopside L78:81 55,13% 41,59% 3,27%

Hypersthene lamella L78:81 3,44% 69,15% 27.41%

Table 2. Mineral formulae recalculation of a single pyroxene’s chemical analyses from the SEM, showing the wt%

end member compositions of diopside and hypersthene.

Fig 17. Two opaque mineral assemblages (oma)

showing the characteristic clear margins. Crossed

polarized light.

18

Hornblende

The hornblende shows little chemical variation in composition in all samples (appendix 1, site

12 and 29). Exsolution of needle shaped ilmenite is common and less common but still

frequent are exsolutions of rutile and titanite. Lamellas of hornblende with slightly higher

aluminium content are observed within the pyroxenes (appendix 1, site 35, spectrum 3), often

together with the needle shaped ilmenite, and occasionally green spinel (fig 18).

Fig 18. A backscattered image of lamellas within a cpx (cpx, spectrum 2). Exsolved spinel (sp, spectrum 1) is clearly

visible as a white strip within the dark grey hornblende lamella (hbl, spectrum 3). Two diagonal cutting grey stripes of

opx/cpx (opx/cpx, spectrum 4) are shown on the right side of the image. As the hornblende and opx/cpx lamellas are

observed along the crystal planes of the cpx, they are interpreted to be post- cpx crystallization. The hornblende lamellas

are cutting the opx/cpx lamellas, suggesting a post opx/cpx- crystallization. The spinels are located as exsolution minerals

within the hornblende, suggesting post- hornblende crystallization. Spectrum compositions are posted in appendix 1 as

Site 35 and spectrum 1 to 4.

There are several members of the hornblende group, and to describe the RAC’s hornblende, a

comparison was made to 206 other known hornblende members with similar chemical

composition (Deer et al, 1997). RAC’s hornblende show greatest similarities to the

hornblende group member hastingsite (appendix 3)

19

Spinel

Two different types of characteristic spinels,

named spinel 1 and spinel 2, were examined

with similar essential chemical composition of

Fe, Mg, Al, O. Spinel 2 has a higher Ti-

content compared to spinel 1 (appendix 1, site

26 and 27) and these two spinels are

distinguished by rounded

inclusions/exsolutions within the crystals of

spinel 1. The spinels typically occur in

assemblages of magnetite, hematite and

corundum, and rarely in hornblende lamellas

within the pyroxenes.

To classify spinel 1 and spinel 2, a “spinel

prism” is used, based on the chemical analysis

(fig 19). Both spinel 1 and spinel 2 classifies

as ferroan spinel types. Spinel 1 is a pure solid

solution between spinel and hercynite, but

with a larger contribution of hercynite, and classifies as a Mg- rich hercynite. Spinel 2 is more

complex, as it is a solid solution between spinel, hercynite, magnesioferrite and magnetite/

ulvöspinel. It classifies as a Ti- poor/Mg- rich hercynite.

Magnetite and Hematite

Magnetite and hematite are common in the opaque mineral assemblages closely associated

with spinel and corundum. Exsolved Fe- oxides occur in hornblende and pyroxene as

“needles” along the cleavage planes and as rounded inclusions.

Titanite

Exsolved needle shaped titanite is common in the hornblende, as well as exsolved illmenite

within the titanites.

Ilmenite

Ilmenite is more frequent than titanite or

rutile, as exsolved needle shaped crystal

within the hornblende (fig 20).

Rutile

Rutile occur, analogous to titanite, but less

commonly, as exsolved needles in

hornblende.

Corundum

Corundum is frequent along the borders of

spinel and magnetite in the opaque mineral

assemblages.

Fig 19. Nomenclature for members of the spinel

group based on chemical composition. Spinel 1 and 2

classifies as ferroan spinel types, based on two

measurements.

Fig 20. Exsolved ilmenite “needles” within a

hornblende crystal in sample L78:81 as a back

scattered image from the SEM. The purple square

shows the area measuring the hornblende and ilmenite

composition.

20

4.8 Pressure and temperatures

Known pressure/temperature (P/T) stability fields for mineral assemblages are used as an

indicator of the P/T environment the hornblendite could have originated from. Hornblende’s

stability field in a subduction environment ranges from 1000°C at 1 GPa to 550°C at 2.7 GPa,

while the pyroxenes stability field include a higher temperature and greater pressure

environment (fig 21) (Ashwal, 1993). Orlando et al (2000) experimental studies of basanites

hosting similar clinopyroxenes and spinels as in the investigated samples L84:25 and L78:81

show a stability field ranging from 1440° C and 3 GPa to 1480°C and 2 GPa (fig 22).

Fig 21. P/T stability field for minerals in a subduction zone

environment according to Ashwal (1993).

Fix 22. P/T stability field for an assemblage of clinopyroxene and

spinel in an experimental phase relation study of basanite. The

heavier line represents liquidus curve. Reproduced from Orlando et

al (2000).

21

The TiO2- and Al2O3 content (wt%) of hornblende reflects a possible P/T environment for

hornblende to form in. The TiO2 content correlates to the temperature but is nearly

independent of the pressure. But in combination with the Al2O3 content a useful

geothermobarometer is provided (Ernst et al, 1998). Two values are used (appendix 1, site 12

and 19), the first value is measured on a pure hornblende, clear of exsolved ilmenite

“needles”. The second value is measured over a large area, including both hornblende and

ilmenite “needles”, to produce an integrated mean bulk composition of the hornblende before

the ilmenite needles were exsolved. This composition suggests reflecting the original

composition of the hornblende. With an increasing temperature, and a decreasing pressure,

hornblende cannot host TiO2 resulting in exsolution of ilmenite lamellas (fig 23).

Fig 23. Isopleths of Al2O3 and TiO2, in weight percent, based on synthetic Ca- amphiboles as a function of P and

T (Ernst et al, 1998). As the pressure decreases from ~1.1 GPa to ~0.9 GPa and the temperature increases from

~700ºC to ~925ºC ilmenite “needles” are suggested to exsolve from the hornblende in sample L79:81. This

exsolution could indicate an upward migration of the hornblendite magma.

4.9 Crystallization sequence and P/T path

The crystallization sequence presented in figure 24 is based on the results from microscopy

observations and chemical analysis. Figure 25 shows a speculative P/T path, based on the

crystallization sequence from figure 24 in combination with the established P/T path

presented in figure 23.

22

Fig 24. A possible crystallization sequence for the hornblendite (L78:79) and the pyroxene hornblendite (L78:81

and L84:25) samples. Primary crystallized minerals are marked 1 – 5 and the later metamorphic minerals 6.

Fig. 25. A speculative P/T path of the hornblendite samples. Number 1 to 3 suggests the crystallization of opx,

cpx, spinels and the exsolved hypersthene lamellas. Number 4 and 5 show the established stability fields for the

Fe- Ti rich hornblende and the hornblende with the exsolved ilmenite “needles” (fig 22). Note that Fe- Ti rich

hornblende might originate from greater pressures and temperatures. Number 6 shows a possible P/T path for the

minerals with a later metamorphic origin.

23

5. Discussion 5.1 Rock types

Trace element data of two samples, L78:79 and L78:81, from the hornblendite body in the

RAC are available to geochemically determine the rock type. The classification diagrams R1-

R2 (De la Roche et al., 1980) and TAS (Cox et al., 1979) are used, both indicating ultramafic

composition (fig 3 and fig 4). The R1-R2 diagram is based on the more immobile elements Ti,

Mg and Fe making this diagram more reliable compared to the TAS diagram based on Na, K

and Si considering the K – alteration in the Hughes diagram (1972) of the samples (fig 5). The

ultramafic composition from both classification diagrams R1-R2 (De la Roche et al., 1980)

and TAS (Cox et al., 1979) correlates with the rock types determined with the optical

microscopy; L78:79 as hornblendite and L78:81 and L84:25 as pyroxene hornblendite.

5.2 Magmatic origin

Hornblende is a common mineral in both metamorphic and igneous originated rocks (Wenk et

al, 2004), and may form in a fluid rich magma or in prograde/retrograde metamorphic

environments due to the influence of hydrous fluids. Field observations show no indication of

foliation or preferred mineral orientation, indicating no deformation metamorphism has

occurred. The samples show a poikilitic texture of hornblende oikicrysts, with a maximum

length of 7 cm, enclosing pyroxenes. This is confirmed in optical microscopy and SEM and

could indicate an order of crystallization with pyroxene as the first mineral to crystallize. This

is best observed in samples L78:79 and 78:81. But this assumption should according to

Shelley (1993) be taken with care, when examples of simultaneous crystallization of poikilitic

textures exist.

Magmatism is still the most likely source, due to the characteristic igneous textures (Blatt et

al, 2006) of the hornblende oikocrysts and the poikilitic pyroxenes. The massive and

undeformed texture observed in the hand samples further support the suggestion of a

magmatic origin.

5.3 Crystallization sequence

Textural relations indicate that the most likely minerals to first crystallize are the pyroxenes

and the Fe, Mg, Al- spinels, frequently enclosed by hornblende. Orthopyroxenes are observed

in optical microscopy, and if Bowen’s reaction series is applied, orthopyroxene would be the

first to crystallize followed by the clinopyroxene diopside. This sequence could not be

determined from textural relations in optical microscopy or SEM. Occasionally the diopside

shows lamellas of hypersthene, indicating post diopside crystallization. Ilmenite, titanite and

rutile “needles” are common along the cleavage planes of the hornblende, most likely caused

by Fe- Ti exsolution due to a cooling history of the hornblende (Mongkoltip et al, 1983).

Ilmenite is exsolved within titanite suggesting post titanite crystallization sequence. The

hornblendes show enclosed inclusions of the frequently appearing green Fe, Mg, Al- spinel

indicating pre hornblende crystallization. The spinels are often part of an opaque mineral

assemblage, containing hematite, magnetite, minor amounts of sulphides and corundum.

These assemblages are repeatedly enclosed in the Fe- Ti “needle” rich hornblendes showing a

clear rim of Fe- Ti “needle”- free hornblende. A possible origin of these opaque mineral

assemblages is the Ti- Fe components from the hornblende, suggesting post hornblende

exsolution. A relict garnet altered to chlorite, magnetite and calcite is a strong indicator of

metamorphism and secondary processes as well as the alteration products of chlorite,

serpentinite and epidote related to pyroxenes and hornblende.

24

5.4 Tectonic setting

A general trend can be distinguished in the enrichment of the LIL- elements compared to the

HFS- elements in the spider diagram (fig 6). This could indicate a subduction zone magma

generated by the transport of fluid- soluble elements into the mantle wedge region (Tatsumi et

al., 1995). But the enrichment of Ta and Nb do not fit this interpretation. Phosphorous is an

incompatible element in mantle mineralogy, and will during partial melting quickly partition

to the melt (Rollinson, 1993). The depletion of phosphorous may well indicate mantle origin.

According to Rehnström (2003), the syenite instrusions are the oldest components within the

TMC where the magmatic activity is constrained to ~1.78- 1.76 Ga based on U- Pb zircon

dating on syenite samples. But in the RAC, observations are made (Björklund, pers. com.) of

syenite intrusions cutting mafic intrusions such as gabbros suggesting post- gabbro activity.

Rehnström’s (2003) zircon dating is slightly younger than the magmatic activity in the

Lofoten complex, ~1.8 Ga (Markl et al., 1998). Considering the long lived magmatic activity,

and Björklund’s (pers. com.) observations, same tectonic source is still likely.

It is possible the anorthosite of the RAC is of similar age as the anorthosite of the AMCG

Lofoten Complex, and considering the enclosed appearance of the hornblendite/ pyroxene

hornblendite body within the RAC’s anorthosite, this body likely intruded in the “active”

anorthosite. This would indicate similar ages of hornblendite body and the anorthosite,

making the post- sveconfennian orogen a potential source of origin. This could correlate with

the weak connection to a subduction environment in the spider diagram.

5.5 Pressure and Temperatures

The only indicator of a possible tectonic setting is a subduction environment based on the

Spider diagram (fig 6). Supporting evidence for this is the high Fe- Ti hornblende’s P/T

stability field in a subduction environment ranging from 1000°C at 1 Gpa to 550°C at 2,7

Gpa. In the Ernst et al (1998) isopleth Al2O3 and TiO2- diagram (fig 23) the samples plot

within this stability field. A suggestion would be, as the pressure decreases from ~1.1 GPa to

~0.9 GPa and the temperature increases from ~700ºC to ~925ºC, the ilmenite “needles”

exsolve from the hornblende when TiO2 no longer fit in the hornblende crystal structure (fig

25, number 4 and 5). Environments with decreasing pressures and increasing temperatures are

observed in the mantle wedge of subduction zone environments (fig 26), and could therefore

indicate an upward migration of the crystallizing of the hornblendite magma within this

environment (Tatsumi et al., 1995). But according to Tatsumi et al (1995) the temperature

range of ~700ºC to ~925ºC are at greater pressure than ~1.1 GPa to ~0.9 GPa. However, as

the isopleth Al2O3 and TiO2- diagram suggests minimum pressures and temperatures,

hornblende could have formed at an earlier stage, in greater pressures and temperatures. The

P/T paths for the pyroxenes (number 1-3) and the metamorphic minerals (number 6) shown in

figure 25 are based on microscopy- and SEM observations, with no actual

geothermobarometry calculations.

According to Shelley (1993), poikilitic textures do not always show the order of

crystallization. Tatsumi et al (1995) indicate another possible scenario where pyroxenes

crystallize after hornblende. Subducted lithosphere sometimes produce a dehydrated reaction

were amphibole, especially hornblende, releases water to form clinopyroxene and garnet. The

released water form buoyancy “hydrous curtains” which in a later stage are a part in the

formation of the trench side volcano chains. This reaction takes place at a maximum pressure

of 3.5 Gpa. But this scenario cannot be excluded even though it does not fit into the

established crystallization sequence described in chapter 5.3.

25

Fig 26. A simplified illustration of a subduction zone environment. The orange to red area illustrate the mantle

wedge region. An area similar to this, with slightly different temperature intervals in the mantle wedge region,

could possibly have been the host for an upward migration of hornblendite magma in the Proterozoic eon.

Illustration reproduced from Tatsumi et al., 1995.

5.6 Further investigations

Considering the low number of investigated samples in this thesis, future work should include

a greater number of samples to achieve more satisfying conclusions. Additional and more

thorough work in the SEM could result in well calculated geothermometers and

geobarometers of the pyroxenes. This would be of great interest regarding the origin of the

samples. Additional work in the SEM, as well as a greater number of samples, would also

give a more accurate statistical result than presented in this thesis.

26

6. Conclusion Three samples were collected from a hornblendite body in the Routevare Anorthosite

Complex (RAC) located in the Northern part of the Swedish Caledonides. The samples are of

ultramafic composition and can be classified as hornblendite (L78:79) and pyroxene

hornblendite (L78:81 and L84:25). Considering the undeformed and massive texture,

observed both in hand samples and microscopy, magmatic origin is very likely. The

established crystallization sequence (fig 23) generally agreeing with Bowen’s reaction series

is mainly based on observations of enclosed minerals and exsolution textures. Secondary

minerals suggest later retrogressive metamorphic event/events.

Results from the spider diagram indicate a possible tectonic setting of a subduction zone

magma generated by the transport of fluid- soluble elements into the mantle wedge region, but

this assumption should be taken with great care due to the deviating concentrations of Ta and

Nb.

The mineral assemblage of clinopyroxenes and spinels indicate a minimum crystallization

temperature and pressure of 1440° and 3Gpa to 1480° and 2 Gpa.

Exsolution of ilmenite ”needles” in the hornblende suggest decreasing pressures ~1.1 to ~0.9

GPa and increasing temperatures ~700ºC to ~925ºC. Areas with decreasing pressures and

increasing temperatures, just like the hornblendite magma mentioned above, are observed in

subduction related mantle wedge regions.

7. Acknowledgment I especially would like to thank my supervisor, Associate Professor Lennart Björklund for

samples, guidance and support. Ali Froozan and PhD Karin Appelqvist made the SEM-work

possible, thank you for your patience. My eyes and brain spent many hours examining thin

sections and I had several interesting and giving discussions with PhD Johan Hogland and

Professor Rob Hellingwerf in the optical microscopy facility. Finally I would like to thank

Linn Karlsson for her patience and support.

27

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Blatt H., Tracy R.J., Owens B.E., 2006, Petrology – Igneous, Sedimentary and Metamorphic,

Third edition., W.H. Freeman and Company New York, 530pp.

Björklund L., 1994, The Routevare Anorthosite Complex a Fe-Ti massif type differentiated

complex, N. Swedish Caledonides. Abstr. 21:a Nordiska Geologiska Vintermötet, Luleå 1994

Björklund L., Stigh J., 1992, The Routevare Anorthosite Complex - a Fe-Ti massif type

differentiated complex, N. Swedish Caledonides. Abstr. IGCP-290 Conference 1-6 June 1992

in Rogaland, Norway. C.E.R.M., Université du Québec à Chicoutimi, Second Newsletter -

Summer 1992, 4.

Björklund L., Personal comments.

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Henderson P. (ed), Rare earth element geochemistry. Elsevier, pp. 63-114.

Cox K.G., Bell J.D. and Pankhurst R.J., 1979, The interpretation of igneous rocks. George.

Allen and Unwin, London, 450pp.

De la Roche H., Leterrier J., Grande Claude P. and Marchal M., 1980, A classification of

volcanic and plutonic rocks using R1-R2 diagrams and major element analyses – its

relationships and current nomenclature. Chemical Geology, 29, 183-210.

Deer W.A., Howie R.A., J. Zussman., 1997, Rock Forming Minerals, Double Chain Silicates

– Second edition. The Geological Society, Vol 2B, 234, 242-269.

Ernst W.G., Liu J., 1998, Experimental phase – equalibrium study of Al – and Ti – contents of

calcic amphibole in MORB – A semiquantitative thermobarometer, American Mineralogist,

Vol 68, 952-969.

Farbtafel nach Michel-Levy, herausgegeben von Carl Zeiss

Fredén K., 2002, Berg och Jord – Sveriges Nationalatlas. Kartförlaget., 22

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2009-05-14

Le Maitre R.W., 1989, A classification of igneous rocks and glossary of terms. Blackwell

Scientific Publications., 193pp.

Markl G., Frost R.B., Bucher K., 1998, The origin of Anorthosites and Related Rocks from

the Lofoten Islands, Northern Norway: I. Filed Relations and Estimations of Intrinsic

Variables, Journal of Petrology, Vol 39, 1425-1452.

Mongkoltip P., Ashworth J.R., 1983, Exsolution of ilmenite and rutile in hornblende,

American Mineralogist, Vol 68, 143-155.

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Nesse W.D., 2000, Introduction to Mineralogy, Oxford University Press, 442pp.

Orlando A., Conticelli S., Armienti P., Borrini D., 2000, Experimental study on a basanite

from the McMuro Volcanic Group, Antarctica: inference on its mantle source, Antarctic

Science, Vol 12 (1), 105-116

Pearce J.A., 1983, Role of sub-continental lithosphere in magma genesis at active continental

margins. In: Hawkesworth C.J. and Norray M.J. (eds.), Continental basalts and mantle

xenoliths. Shiva, Nantwich, 230-249

Rehnström E.F., 2003, Geochronology and petrology of the Tielma Magmatic Complex,

northern Swedish Caledonides – results and tectonic implications. Norwegian Journal of

Geology, Vol. 83, 243-257.

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Caledonides. In D. G. Gee & B. A. Sturt (eds.): The Caledonide Orogen — Scandinavia and

Related Areas. John Wiley & Sons, Chichester., 55-68.

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Appendix 1

Geochemical data from SEM, major elements, all values in wt%

Pyroxene

Site 21

P.Lamell

Site 21

Hbl

Site

12

Hbl+

ilmenite

Site 19

Spinel

1 Site

26

Spinel

2 Site

27

Hbl

Site

29

Hbl+

ilmenite

Site 29

Ilmenite

Site 19

Spinel

Site 35

Specturm

1

Cpx Site

35

Specturm

2

Hbl Site

35

Spectrum

3

Opx/cpx

Site 35

Spectrum

4

Hbl Site

48

Spectrum

1

Ilmenite

Site 48

Spectrum

2

Titanite

Site 48

Spectrum

3

Na2O 0,37 0,15 1,83 2,13 1,40 0,71 2,12 2,06 0,25 0,82 0,43 2,09 0,26 2,10 0 0

MgO 12,84 21,55 13,23 13,5 11,30 8,22 13,25 13,13 2,61 10,31 13,90 13,87 19,41 12,62 0,31 0

Al2O3 7,07 5,54 11,36 14,34 57,11 56,19 14,74 13,62 1,07 53,66 5,22 14,95 4,87 12,91 0 0,93

SiO2 46,65 48,19 42,86 39,81 0 0,12 39,58 38,64 2,3 3,74 48,06 41,57 49,43 40,97 1,09 29,16

P2O5 0 0 0 0 0 0,19 0 0 0 0 0 0 0 0 0 0

SO3 0 0 0 0 0 0 0 0,13 0 0 0 0 0 0 0 0

K2O 0 0 0,62 0,75 0 0 0,69 0,73 0 0 0 0,06 0 0,79 0 0

CaO 23,68 1,5 13,25 12,37 0 0 12,34 11,89 1,02 1,39 23,43 13,8 10,58 11,85 1,79 28,23

TiO2 1,07 0,11 0,82 2,82 0 6,72 0,82 2,82 48,66 0 0,7 0,38 0,31 0,83 48,53 38,90

CrO3 0 0 0,22 0 0,21 0,11 0 0 0 0,67 0 0 0 0,13 0 0

MnO 0 0,67 0,17 0 0,33 0,2 0,11 0,15 0,87 0,34 0,14 0,11 0,53 0,19 1,26 0

Fe2O3 6,95 21,94 12,82 12,97 27,06 24,58 12,03 12,91 48,01 29,09 3,03 10,29 16,31 13,15 50,70 0,75

Total 98,63 99,75 97,18 98,69 97,06 97,05 95,69 96,09 104,8 100,03 97,93 97,12 101,69 95,54 103,68 97,96

Appendix 2

Whole rock analysis, all values in wt%

SiO2 TiO2 Al2O3 FeO Fe2O3 MnO MgO CaO Na2O K2O P2O5 CO2 F S

L78:79 44.5 1.12 9.05 2.51 7.37 0.15 12.5 15.7 1.26 0.4 0.003 0 0 2.54

L78:81 40.0 1.55 13.3 6.52 8.35 0.15 11.4 14.7 1.04 0.27 0.002 0 0 1.0

Appendix 3

Hornblende comparisons, all values in wt%