GEO4910 Field Course 12-13 September 2015
Note: Before you go on the field course, check by yourself the minerals
(characteristics, chemical formulae) and rocks (mineral content, texture, formation
conditions) that we will see (listed below). Also check the background text!
Don’t forget to read this text:
http://folk.uio.no/tomvs/minerals/geo4910/NGF-Abst&Proc-2-2003_Sc_Page57-86.pdf
Participating students must submit their own report from the field course. The
report should contain descriptions of the general geology, the way minerals occur,
what the rocks look like, their textures and mineral contents, and a discussion on
how the mineralizations may have formed, with references to the literature if
available. The points below are meant to be of help for the observations and the
relevant problems at the different stops. NGT = Norsk Geologisk Tidsskrift (the
Norwegian Geological Journal).
We will most 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 time allows.
A: Liertoppen
Contact between Carbo-Permian biotite granite (the "Drammen Granite") and
contact metamorphosed Cambro-Silurian schists and limestones (both sedimentary
rocks, transformed to different classes of hornfels rocks).
1.
2.
3.
4.
5.
6.
What minerals do you observe in the granite? Use a hand lens, and write a
list of the minerals from the most frequent to the least frequent, and estimate
their relative abundances in %, and their sequence of crystallization
(paragenetic sequence).
What texture has the granite? Make a drawing and label the minerals.
Look especially at the quartz in the granite. Does all quartz look the same;
describe? Could there be two generations of rock-forming quartz in this
granite?
Use the results from the experimental petrology of Piwinskii (1973), see
Appendix 1, to discuss a possible pressure development (quantify) of this
granite, and its bearing on a magmatic water phase in this granite.
Do you find signs of fluid circulation (veins; hydrothermal alteration) in this
granite?
Do you find magnetite (or hematite or other iron-containing ore minerals) in
this granite? From this, discuss where the iron could be?
B: Gjellebekk / Auvi Mine (Lierskogen)
Permian skarn deposit with mainly magnetite, pyrite, chalcopyrite, bismuthinite.
1.
2.
3.
4.
What is the geology (rocks, structures) like here?
What kinds of skarn minerals (calcium silicates) do you find here?
What kinds of ore minerals do you find here?
Do you find signs (what/where?) of hydrothermal fluid circulation here?
2
C: Prospect by Aas Café (Fiskum-type quartz vein base metal sulfide deposit)
Precambrian fahlband / sulfide zone with pyrrhotite and pyrite; cut by Permian
hydrothermal vein(s) with quartz, sphalerite, galena, chalcopyrite. Late marcacite.
1.
2.
3.
4.
What relations do you find between the minerals (paragenetic sequence,
replacement 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 geochemical processes led to the
formation of this hydrothermal quartz vein base metal sulfide deposit?
D: Majorplassen (near Aas Café)
Hydrothermal quartz veins and fluorite vein of Permian 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 homogenization temperatures of ca. 200
(157 - 273) degrees C with quite constant fluid density of 0,92 (0,89 - 0,96)
3
g/cm [Norman & Segalstad 1978; GSA Abstr. Prog., Vol. 10, p. 464].
The fluorite gives a larger variation: 0 - 11 weight % NaCl equivalents
(average ca. 8,5) and homogenization temperatures from 115 to more than
3
355 degrees C with varying fluid density from 0,73 to 1,00 g/cm [op. cit.].
Could the quartz and fluorite veins have been formed under similar
conditions?
Can you provide a hypothesis for the formation of fluorite here?
E: Kongsberg Native Silver Calcite Vein Deposit (Kongsberg)
Native silver in calcite veins of Permian age cutting Precambrian fahlbands. We will
visit the Mining Museum and (if time) a mineralization in the fahlband at
Saggrenda.
1.
2.
3.
4.
5.
6.
What major / characteristic minerals du you find in the hydrothermal veins?
Extent and type of wall rock alteration?
Describe the appearance of the fahlband.
What are the arguments of Segalstad (2012 and earlier papers) for where the
silver came from and how it was deposited?
What can be the possible heat sources, which caused the circulation of
hydrothermal water in the Kongsberg / Fiskum-area in Permian times?
What could have been the complexing agent (ligand) for the hydrothermal
transportation of the silver? Where could this ligand have come from?
3
F: Nordagutu Granite (Nordagutu)
Biotite granite of Carbo-Permian age (contemporaneous with the formation of the
Oslo Rift) intruded in Precambrian basement gneissic rocks outside the Oslo
Graben. [Jacobsen, S.B. & Raade, G. 1975: NGT Vol. 55, p. 171-178].
1.
2.
3.
4.
Describe the granite (texture, mineral content, paragenetic sequence), like
you did for the Drammen granite.
Do you find signs of hydrothermal activity associated with (caused by) the
granite?
Do you find magnetite (or hematite or other iron-containing ore minerals) in
this granite? From this, discuss where the iron could be?
What are the differences between this granite and the granite at Stop A?
G: Cappelen Quarry (Fen; Ulefoss)
Carbonatite ("søvite") with columbite and pyrochlore (coppite) etc. of Cambrian
age. Damkjernite lamproite (kimberlite-like) dikes.
1.
2.
What criteria would you use to characterize the carbonatite as a magmatic
intrusive, and not as a sedimentary limestone?
What chemical elements have they mined at these quarries / mines and what
other chemical elements could be of economic interest from here?
H: Road cut and “Vaskeriet” (Fen; Ulefoss)
Ferro-carbonatite and “rødberg” (red carbonatite) with hematite and REE-minerals
(monazite and others) of Cambrian age (REE = Rare Earth Elements; the
lanthanides + yttrium).
1.
2.
Do you see signs of post-solidus volatile activity in the carbonatite?
What chemical elements have they exploited from the rock "rødberg", and
what other chemical elements could be of economic interest from here?
4
I: Gautefall Apartments (Telemark County) - night quarters
The Tørdal Granite, age ca. 1 billion years.
1.
2.
3.
4.
Describe the granite's appearance compared to the Drammen- (Stop A) and
Nordagutu (Stop F) granites. You see that there is almandite garnet in the
granite. Is this a common primary magmatic mineral? What could be the
reason for finding almandite in this granite?
Granites may roughly be classified into mantle-derived and anatexis-derived
(earlier called palingenetic) granites, the latter formed by ultrametamorphosis. Anatexis-granites may further be subdivided into I-type (remelted igneous material) and S-type (melted sedimentary material). In some
cases "restites" (unmelted rests of the original rocks) can give information
about the origin. From your observations and this very simplified way of
classification, would the Tørdal Granite be resembling an I-type or S-type
granite?
[There are other proposed granite classifications, like anorogenic "A-type"
and rift-related "R-type" granites, which will not be considered here.]
Do you see signs of hydrothermal activity associated with (caused by) the
granite?
Burnham & Ohmoto (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 may be associated
with both types. If Burnham & Ohmoto (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 Telemark County)
Precambrian granite pegmatite associated the Tørdal Granite with amazonite alkali
feldspar, beryl, topaz, lepidolite (Li-mica), cassiterite, and REE-minerals.
1.
2.
3.
Describe the relations between the pegmatite and its wall rocks.
Describe structure (zoning?) of this complex pegmatite (wall zone, graphic
granite zone, core-wall zone, and core zone). In which zones do the different
pegmatite minerals occur (or dominate)?
Do you find any hydrothermal veins cutting the pegmatite -- if so, where do
these veins originate?
NOTE: The pegmatite owner wants you to pay 50 kr. per kg rocks taken from his
property. The teacher will collect the money to give to the owner.
J (alternative): A pegmatite quarry, Kragerø (southern Telemark) or elsewhere.
5
K: Kragerø (southern Telemark County)
Precambrian albitite (“kragerøite”) with rutile, pegmatite veins, apatite veins,
hematite veins.
1.
Describe the geologic appearance.
2.
Bodart (1968) proposed a metamorphic / metasomatic model for the
formation of ore deposits in the Kragerø Area.
Give a summary of Bodart's model.
What is your opinion about Bodart's model for the explanation of the Kragerø
Area's geology judged from your observations?
Reference: Bodart, D.E. 1968: On the paragenesis of albitites. NGT, Vol. 48,
p. 269-280.
L: Meikjær Nickel Mine (Bamble) [or another nickel mine in this area]
Precambrian noritic gabbro with massive sulfides.
1.
2.
3.
4.
5.
Describe the geologic occurrence of gabbro and massive sulfides. What is the
texture of the gabbro and the sulfides?
What minerals do you find in the gabbro? Why is the gabbro called a norite?
What ore minerals do you find?
Do you find the nickel mineral pentlandite? How does it occur (see photo)?
Are there any late-stage alterations of the ore?
po
ptl
ptl
po
vio
cp
cp
po
Meikjær Mine
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+
+
22 FeNiS2 + 3 H2O + 8.5 O2 = FeNi2O4 + Fe (aq) + 6 H + 4 SO4 (aq).
6
M: Tvedalen Area (Vestfold County)
Larvikite monzonite quarry, building and ornamental stone
1.
2.
3.
4.
5.
What minerals do you observe in the larvikite? Use a hand lens and write
down the minerals from the most frequent to the least frequent, and estimate
their relative abundance in %, and their sequence of crystallization
(paragenetic sequence).
What texture has the larvikite? Make a drawing and label the minerals.
Do you find quartz in the larvikite? If not, is there another mineral present
instead of quartz?
The larvikite is an attractive decorative stone because of its multi-colored
"Schiller Effect". Is this effect present in all orientations of the rock?
Do you see any pegmatites in the larvikite? What major minerals do these
pegmatites carry? Are these pegmatites different from granite pegmatites; if
so, in what ways? What kind of pegmatites 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 may find relevant).
The report doesn't need to be extensive or neatly made. 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:
Hammer, chisel, hand lens, protection eye glasses, sample bags and marker pen
if you plan to collect samples, notebook, writing materials, geologic maps,
clinometer compass, magnet, acid bottle with 10% HCl, pocket knife, field
backpack, the textbook plus handouts from the GEO4910 course.
In addition bring:
Sturdy field boots, wind- and rain proof field clothes, warm clothes / long
underwear. (Forget neat clothes and your swim suit, because the hotel is closed).
Food:
Bring a lunch (or more than one?) and what you want to drink for the first and
second day. The course offers a LATE dinner (at about 20-21 o'clock) the first
day; plus breakfast and lunch (make your own lunch at breakfast) the second day.
No more food than this will be provided for the second day.
Transportation:
Mini-bus. Inside the vehicle the following is prohibited for safety reasons: smoking,
food, glass bottles, loose rock samples, and loose hammers / chisels. All loose
things must be put in your luggage or in plastic boxes, if provided. (If you want
to collect samples, you must bring sample bags etc. yourself). Your luggage may
be placed in a luggage trailer to be towed by the mini-bus, if many students.
Departure from Oslo the first day around 8 o'clock (places to be agreed on); return
the second day at 18 o'clock (?).
Night quarters:
Gautefall Apartments (Gautefallheia near Drangedal, central Telemark County).
Phone: 35499977; night guard: 93883995.
Note: The course pays for the accomodation and the meals. ALL extra expenses
will have to be paid by the students!
The Sunday morning 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 important incoming
messages. Some parts of the field course have no cellular phone coverage (but
messages can be left at the answering machine, and the calls can be returned
later).
4. September 2015
Associated Professor Tom V. Segalstad
Geological Museum, University of Oslo
8
APPENDIX 1
The red colored line indicates the stability of quartz in the granitic melt. Quartz
(Qz) is stable to the right of the red line. By cooling the melt, or lowering the water
pressure in the melt, the quartz will no longer crystallize from the melt to the left
of the red line ("Qz out"). Similarly for the other major rock-forming minerals
plagioclase (Plag) or potassium feldspar (Kspr). The granitic melt is completely
solidified to a granite at the solidus curve.
9
APPENDIX 2
Excerpted from (with chemical reactions added):
Burnham, C.W. & Ohmoto, H. 1980: Late-stage processes of felsic magmatism.
Mining Geology, Special Issue, No. 8, p. 1-11.
10
APPENDIX 3
The main field trip stops indicated on the Bedrock Map of Norway, Norwegian
Geological Survey, 1984. Scale: width of map ~140 km. North = up.
Reference to the bedrock map:
Sigmond, E.M.O., Gustavson, M. & Roberts, D. 1984: Berggrunnskart over Norge M. 1:1 million. Norges Geologiske Undersøkelse, Trondheim.