GEO4910 Field Course 8-9 September 2012
Note: Before you go on the field course, check by yourself the minerals
(characteristics, chemical formula) and rocks (mineral content, texture, formation
conditions) that we will see (listed below).
Participating students m ust subm it their own report from the field course. The
report should contain descriptions of the general geology, the way m inerals
occur, what the rocks look like, their textures and m ineral contents, and a
discussion on how the m ineralizations m ay have form ed, with references to
the literature if available. The points below are m eant to be of help for the
observations and the relevant problem s at the different stops. NG T = Norsk
G eologisk Tidsskrift (the Norwegian Geological Journal).
We will m ost likely visit the following stops: A, B, C, E, F, G, I, J, L, M .
The other stops (D, H, K) are for reserve if tim e allows.
A: Liertoppen
Contact between Carbo-Perm ian biotite granite (the "Dram m en G ranite") and
a contact m etam orphosed C am bro-Silurian schist and lim estone (both
sedim entary rocks transform ed to different classes of hornfels rocks).
1.
2.
3.
4.
5.
6.
W hat m inerals do you observe in the granite? Use a hand lens and write
down the m inerals from the m ost frequent to the least frequent, and
estim ate their relative abundance in % , and their sequence of
crystallization (paragenetic sequence).
W hat texture has the granite? M ake a drawing and label the m inerals.
Look especially at the quartz in the granite. D oes all quartz look the
sam e; describe? Could there be two generations of rock-form ing quartz
in this granite?
Use the results from the experim ental petrology of Piwinskii (1973), see
Appendix 1, to discuss a possible pressure developm ent of this granite,
and its bearing on a m agm atic water phase in this granite.
Do you find signs of fluid circulation (hydrotherm al alteration) in the
granite?
Do you find m agnetite (or hem atite or other iron-containing ore m inerals)
in this granite? From this, discuss where the iron could be?
B: G jellebekk / Auvi M ine (Lierskogen)
Perm ian skarn
bism uthinite.
1.
2.
3.
4.
deposit
with
m ainly
m agnetite,
pyrite,
chalcopyrite,
W hat is the geology (rocks, structures) like here?
W hat kinds of skarn m inerals (calcium silicates) do you find here?
W hat kinds of ore m inerals do you find here?
Do you find signs (what/where?) of hydrotherm al fluid circulation here?
2
C: Prospect by Aas Café (Fiskum -type deposit)
Precam brian fahlband / sulfide zone with pyrrhotite and pyrite; cut by Perm ian
hydrotherm al vein(s) with sphalerite, galena, chalcopyrite. Late m arcacite.
1.
2.
3.
4.
W hat relations do you find between the m inerals (paragenetic sequence,
replacem ent reactions)?
Do you find any wall rock alteration (type, thickness)?
Do you find a black substance in the veins -- what is this substance?
Have you got a theory for what kind of geochem ical processes led to the
form ation of this hydrotherm al vein deposit?
D: M ajorplassen (near Aas Café)
Hydrotherm al quartz veins and fluorite vein of Perm ian age.
1.
2.
3.
4.
Can you say anything about the age relation between the quartz veins
and the fluorite vein?
Do you find a black substance in the veins -- what is this substance?
The quartz in this deposit has fluid inclusions giving salinities of ca. 5
(2,2 - 6,7) weight % NaCl equivalents and hom ogenization tem peratures
of ca. 200 (157 - 273) degrees C with quite constant fluid density of 0,92
(0,89 - 0,96) g/cm 3.
The fluorite gives a larger variation: 0 - 11 weight % NaCl equivalents
(average ca. 8,5) and hom ogenization tem peratures from 115 to m ore
than 355 degrees C with varying fluid density from 0,73 to 1,00 g/cm 3.
Could the quartz and fluorite veins have been form ed under sim ilar
conditions?
Can you provide a hypothesis for the form ation of fluorite here?
E: Kongsberg Silver Deposit (Kongsberg)
Native silver in calcite veins of Perm ian age cutting Precam brian fahlbands.
We will visit the M ining M useum and (if tim e) a m ineralization in the fahlband
at Saggrenda.
1.
2.
3.
4.
5.
6.
W hat m ajor / characteristic m inerals du you find in the hydrotherm al
veins?
Extent and type of wall rock alteration?
Describe the appearance of the fahlband.
W hat are the argum ents of Segalstad (2009 and earlier papers) for
where the silver cam e from and how it was deposited?
W hat can be the possible heat sources, which caused the circulation of
hydrotherm al water in the Kongsberg / Fiskum -area in Perm ian tim es?
W hat could have been the com plexing agent (ligand) for the
hydrotherm al transportation of the silver? W here could this ligand have
com e from ?
3
F: Nordagutu Granite (Nordagutu)
Biotite granite of Carbo-Perm ian age (contem poraneous with the form ation of
the O slo Rift) intruded in Precam brian basem ent gneissic rocks outside the
O slo Graben. (Jacobsen, S.B. & Raade, G. 1975: NG T Vol. 55, p. 171-178).
1.
2.
3.
Describe the granite (texture, m ineral content, paragenetic sequence),
like you did for the Dram m en granite.
D u you find signs of hydrotherm al activity associated with (caused by)
the granite?
Do you find m agnetite (or hem atite or other iron-containing ore m inerals)
in this granite? From this, discuss where the iron could be?
G : Cappelen Quarry (Fen; Ulefoss)
Carbonatite ("søvite") with colum bite and pyrochlore (coppite) etc. of
Cam brian age. Dam kjernite lam proite (kim berlite-like) dikes.
1.
2.
W hat criteria would you use to characterize the carbonatite as a
m agm atic intrusive, and not as a sedim entary lim estone?
W hat chem ical elem ents have they m ined at these quarries / m ines and
what other chem ical elem ents could be of econom ic interest from here?
H: Road cut and Vaskeriet (Fen; Ulefoss)
Ferro-carbonatite and “rødberg” (red carbonatite) with hem atite and REEm inerals (m onazite and others) of Cam brian age (RE E = Rare Earth
Elem ents; the Lanthanides + yttrium ).
1.
2.
Do you see signs of post-solidus volatile activity in the carbonatite?
W hat chem ical elem ents have they exploited from the rock "rødberg",
and what other chem ical elem ents could be of econom ic interest from
here?
4
I: G autefall Tourist Hotel (Telem ark) - night quarters
The Tørdal G ranite, age ca. 1 billion years.
1.
2.
3.
4.
Describe the granite's appearance com pared to the Dram m en- and
Nordagutu granites. You see that there is alm andite garnet in the granite.
Is this a com m on prim ary m agm atic m ineral? W hat could be the reason
for finding alm andite in this granite?
G ranites m ay roughly be classified into m antle-derived and anatexisderived (earlier called palingenetic) granites, the latter form ed by ultram etam orphosis. Anatexis-granites m ay further be subdivided into I-type
(re-m elted igneous m aterial) and S-type (m elted sedim entary m aterial).
In som e cases "restites" (unm elted rests of the original rocks) can give
inform ation about the origin. From your observations and this very
sim plified way of classification, would the Tørdal G ranite be resem bling
an I-type or S-type granite?
[There are other proposed granite classifications, like anorogenic "Atype" and rift-related "R-type" granites, that will not be considered here.]
Do you see signs of hydrotherm al activity associated w ith (caused by)
the granite?
Burnham & Ohm oto (1980) argued that especially copper deposits would
be associated with I-type granites, and that especially tin deposits would
be associated with S-type granites. Molybdenite deposits m ay be
associated w ith both types. If Burnham & O hm oto (1980) were right,
what kinds of deposits would you expect to find in the area associated
with the Tørdal granite? See Appendix 2.
Reference: Burnham, C.W. & Ohmoto, H. 1980: Late stage felsic magmatism.
Mining Geology, Special Issue, No. 8, p. 1-11.
J: Tørdal (central Telem ark)
Precam brian granite pegm atite associated the Tørdal G ranite with am azonite
alkali feldspar, beryl, topaz, lepidolite (Li-m ica), cassiterite and REE-m inerals.
1.
2.
3.
Describe the relations between the pegm atite and its wallrocks.
Describe structure (zoning?) of the pegm atite (wall zone, graphic granite
zone, core-wall zone and core zone). In which zones do the different
pegm atite m inerals occur (dom inate)?
Do you find any hydrotherm al veins cutting the pegm atite -- if so, where
do these veins originate?
J (alternative): A pegm atite quarry, Kragerø (southern Telem ark)
5
K: Kragerø (southern Telem ark)
Precam brian albitite (kragerøite) with rutile, pegm atite veins, apatite veins,
hem atite veins.
1.
Describe the geologic appearance.
2.
Bodart (1968) proposed a m etam orphic / m etasom atic m odel for the
form ation of ore deposits in the Kragerø Area.
G ive a sum m ary of Bodart's m odel.
W hat is your opinion about Bodart's m odel for the explanation of the
Kragerø Area's geology judged from your observations?
Reference: Bodart, D.E. 1968: O n the paragenesis of albitites. NG T, Vol.
48, p. 269-280.
L: M eikjæ r Nickel M ine (Bam ble) [or another nickel m ine in this area]
Precam brian noritic gabbro with m assive sulfides.
1.
2.
3.
4.
5.
Describe the geologic occurrence of gabbro and m assive sulfides. W hat
is the texture of gabbro and sulfides?
W hat m inerals do you find in the gabbro? W hy is the gabbro called a
norite?
W hat ore m inerals do you find?
Do you find the nickel m ineral pentlandite? How does it occur?
Are there any late-stage alterations of the ore?
po
ptl
ptl
po
cp
Meikjær Mine
vio
po
cp
cp po
vio
Nystein Mine
Photomicrographs, Bamble nickel ores, polished sections, 0.5 mm longest side. Left: Meikjær Mine;
pentlandite (ptl) in pyrrhotite; cp = chalcopyrite. Right: Nystein Mine; pentlandite (ptl) replaced by violarite
FeNi2O4 (vio) in pyrrhotite (po). Photo and collection: T.V. Segalstad.
If pentlandite (Fe,Ni)9S8 is written as simplified FeNiS2; possible replacement reaction:
2 FeNiS2 + 3 H2O + 8.5 O2 = FeNi2O 4 + Fe2+ (aq) + 6 H+ + 4 SO 42- (aq).
6
M : Tvedalen (Vestfold)
Larvikite m onzonite quarry, building and ornam ental stone
1.
2.
3.
4.
5.
W hat m inerals do you observe in the larvikite? Use a hand lens and write
down the m inerals from the m ost frequent to the least frequent, and
estim ate their relative abundance in % , and their sequence of
crystallization (paragenetic sequence).
W hat texture has the larvikite? M ake a drawing and label the m inerals.
Do you find quartz in the larvikite? If not, is there another m ineral present
instead of quartz?
The larvikite is an attractive decorative stone because of its m ulti-colored
"Schiller Effect". Is this effect present in all orientations of the rock?
Do you see any pegm atites in the larvikite? W hat m ajor m inerals do
these pegm atites carry? Are these pegm atites different from granite
pegm atites; if so, in what ways? W hat kind of pegm atites are these?
Report:
The report is due 2 days after the field course (Tuesday; before exam ).
The report should be based on your field observations, our discussions in the
field, and the literature handed out (plus other literature you m ay find
relevant).
The report doesn't need to be extensive or neatly m ade. Answers to the
questionnaire, handwritten and drawn on the front and rear pages of the
questionnaire itself, will be accepted.
7
What to bring to the field course:
Useful to bring:
Ham m er, chisel, hand lens, protection eye glasses, sam ple bags and m arker
pen if you plan to collect sam ples, notebook, writing m aterials, geologic m aps,
clinom eter com pass, m agnet, acid bottle with 10% HCl, pocket knife, field
backpack, the textbook plus handouts from the G EO 4910 course.
In addition bring:
Sturdy field boots, wind- and rain proof field clothes, w arm clothes / long
underwear, neat clothes and possibly swim suit (for the hotel).
Food:
Bring a lunch bag (or m ore than one?) and what you want to drink for the first
day. The course offers a LATE dinner (at about 20 o'clock) the first day, plus
breakfast and lunch the second day.
Transportation:
M ini-bus. Inside the vehicle the following is prohibited for safety reasons:
sm oking, food, glass bottles, loose rock sam ples, and loose ham m ers /
chisels. All loose things m ust be put in your luggage or in plastic boxes, if
provided. (If you want to collect sam ples, you m ust bring sam ple bags etc.
yourself).
Departure from O slo the first day around 8 o'clock (places to be agreed on);
return the second day at 17-18 o'clock (?).
Night quarters:
G autefall Tourist Hotel (G autefallheia near Drangedal, central Telem ark
County).
Phone: 35995000 / 35995051.
Note: The course pays for the accom odation and the m eals. But A LL extra
expenses (like drinks or telephone at the hotel) will have to be paid by the
students before departure!
The hotel pool is norm ally open between 7 and 20 o'clock.
The m orning breakfast is at 8 o'clock and departure no later than 9 o'clock.
Mobile phone:
The teacher Segalstad has cellular phone # 911 93 973 for im portant
incom ing m essages. Som e parts of the field course have no cellular phone
coverage (but m essages can be left at the answering m achine, and the calls
can be returned later).
1. Septem ber 2012
Associated professor Tom V. Segalstad
G eological M useum , University of O slo
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APPENDIX 1
The line colored red indicates the stability of quartz in the granitic m elt. Q uartz
(Qz) is stable to the right of the red line. By cooling the m elt, or lowering the
water pressure in the m elt, the quartz will no longer crystallize from the m elt
to the left of the red line ("Q z out"). Sim ilarly for the other m ajor rock-form ing
m inerals plagioclase (Plag) or potassium feldspar (Kspr). The granitic m elt is
com pletely solidified to a granite at the solidus curve.
9
APPENDIX 2
Excerpted from (with chemical reactions added):
Burnham , C.W. & O hm oto, H . 1980: Late-stage processes of felsic
m agm atism . M ining G eology, Special Issue, No. 8, p. 1-11.
10
APPENDIX 3
The m ain field trip stops indicated on the Bedrock M ap of Norway, Norwegian
G eological Survey, 1984. Scale: width of m ap ~140 km . North = up.
Reference to the bedrock map:
Sigm ond, E.M .O., G ustavson, M . & Roberts, D. 1984: Berggrunnskart over
Norge - M . 1:1 m illion. Norges G eologiske Undersøkelse, Trondheim .