Transcript THE TECHNIQUE OF MACROPHOTOGRAPHY IN CATHODOLUMINESCENCE

THE TECHNIQUE OF
MACROPHOTOGRAPHY IN
CATHODOLUMINESCENCE
STUDIES
By
Donald J. Marshall, RELION Industries
With acknowledgment to
Dr. Anthony N. Mariano, Consultant
MACROPHOTOGRAPHY
• MICRO vs MACRO
• CLASSICAL DEFINITION IS A PHOTO
BIGGER THAN LIFE
• DOESN’T WORK FOR MICROSCOPISTS
BECAUSE ALL PHOTOS ARE LIKE THIS
• SO MACROPHOTOGRAPHY MEANS, TO
US, ONLY CAMERA IS USED AND
LARGE SPECIMEN AREA IS VIEWED
MACROPHOTOGRAPHY
• Used only by a few investigators
• Microscope with very low magnification
objective (1X) sometimes used;
• But usually no microscope– only a
camera.
• Viewed area 2 to 5 cm in diameter
WILLIAM CROOKES, F.R.S.
• 1880. Philosophical Transactions
of Royal Society
• “….preparation of sulphide of
calcium……. shines with a bright
blue-violet light, and, when on a
surface of several square inches,
is sufficient to light up a
room……. ”
MACRO vs MICRO
• Unfocused cold cathode beam about 1
cm. diameter.
• Top window in some cases limits viewed
area to 7 to 8 mm.
• So arbitrary dividing line is:
• 5 mm or less is micro.
• 5 mm to 5 cm or greater is macro.
OPERATIONAL REQUIREMENTS
• Capability to defocus the electron beam.
• Sufficient electron beam current to provide
viewable cathodoluminescence.
• Large viewing window area.
FOCUS and DEFOCUS
• Unfocused beam implies that nothing is
done to the beam to change its size.
• Unfocused beam is usually not large
enough in diameter – only 0.5 cm to 1 cm.
• So defocusing is done.
RASTERING
• Could also be done, in principle, by
rastering beam but instrumentation
requirements are more involved and this is
not done on simple cold cathode-based
instruments
FOCUSING AND DEFOCUSING OF
ELECTRON BEAM
• Requires special lens element in
electron gun to defocus electron
beam
• Both electrostatic and
electromagnetic lens are possible.
• Electromagnetic lens is most
common
MAGNETIC FOCUS COIL
COIL HOUSING
COIL
WINDINGS
FOCUS
POINT
GAP
FOCUS PLANE
MAGNETIC FIELD
LINES
ELECTRON BEAM
PATH
FOCUSING AND DEFOCUSING
• In normal operation,
• focus point moves closer to coil
(stronger focus) with higher coil
current and
• Focus point moves away from coil
(weaker focus) with lower coil current.
DEFOCUSING MODE
COIL HOUSING
COIL
WINDINGS
FOCUS
POINT
GAP
DEFOCUS PLANE
MAGNETIC FIELD
LINES
ELECTRON BEAM
PATH
DEFLECTION, FOCUSING, AND
ABERRATIONS
• Coils are usually designed for the best small spot size
and shape.
• Coils are not designed for best defocused spot shapes
and there is some appreciable variation in results.
• The spot can always be made larger but the shape may
be less than circular or elliptical and some compromise
is necessary.
• For those instruments which include magnetic deflection
of the beam, there is an inevitable interaction between
the deflection and focusing systems.
• Any deviations from the ideal beam shapes are termed
aberrations. If there were sufficient demand for macro CL
work, then coil designers would rise to the occasion.
“NO FOCUS” CONDITION
FOCUS COIL
Cathode
SAMPLE
PLANE
USUAL FOCUS CONDITION
FOCUS COIL
Cathode
SAMPLE
PLANE
DEFOCUS CONDITION
FOCUS COIL
Cathode
DEFOCUS CONDITION
SAMPLE
PLANE
DEFOCUSED BEAM SHAPE EXAMPLE
• Scottish Sandstone
• Beam is large but
it is strongly
elliptical
5 cm
Dr. James Clark
• Macro CL used originally to examine panned
concentrates from stream sediments in carbonatite
exploration.
• Used in granitoids where examination of larger areas
facilitates identification of feldspar phase relationships
and pathways for meteoric alteration fluids.
• Also to determine timing of quartz and carbonate events
associated with gold mineralization and examination of
cross cutting relationships in veins.
• Dr. James Clark, Applied Petrographics.
• http://www.appliedpetrographics.com
GRANODIORITIC INTRUSIVE ROCK
• K feldspar - light blue CL - weak reddish
purple overprint. Unaltered plagioclase yellowish green overprinted by reddish
brown to light brown CL with progressively
stronger clay alteration.
• The K feldspar poikilitically encompasses
smaller crystals of plagioclase.
• Quartz and micas are non-luminescent.
Field of view = 15.42 mm.
• Courtesy of Dr. James Clark
GRANODIORITIC INTRUSIVE ROCK
• K feldspar light blue CL.
Unaltered plagioclase
yellowish green CL
• The K feldspar
poikilitically encompasses
smaller crystals of
plagioclase.
• Quartz and micas are
non-luminescent.
• Field of view= 15.42 mm.
• Courtesy of Dr. James
Clark
1. 5 centimeter
MULTIPLE EPITHERMAL QUARTZ
TYPES
• Epithermal quartz vein
with CL
• CL photo shows two
varieties of
microcrystalline quartz
(tan and dull red), while
the comb-textured quartz
has fine-scale growth
zoning in shades of
yellow, red, gray, and
blue CL.
• Dr. James Clark
1.48 cm
COMPLEX BANDED QCHALCEDONY VEIN
• Complex epithermal Qchalcedony vein. CL photo
highlights a quartz vein
stratigraphy with early nonluminescent microcrystalline
quartz (Q1), an intermediate
stage of microcrystalline quartz
with moderate yellowish-brown
CL, and late-stage chalcedony
and quartz with strong yellow
CL (Q3). The main vein is cut
by a narrow veinlet of Q2 and
orange-luminescent calcite.
• Dr. James Clark
LATE STAGE
CHALCEDONY
AND QUARTZ
EARLY NONLUMINESCENT
QUARTZ
2.14 cm
CALCITE
DRUSY QUARTZ VEIN
• Drusy quartz in a polished slab
of quartz vein material from an
epithermal silver-gold mine,
Durango, Mexico. Locally this
quartz has native gold
inclusions. No zonation visible
in plane light.
• Kodak Royal Gold 200 film, 60
sec. 12.5 kV, 0.6ma.
• Vertical dimension is 19 mm.
• Dr. James Clark
1.4 cm
Quartz-calcite-adularia vein
• Quartz-adularia-calcite
vein. Lattice- and
parallel-bladed acicular
calcite needles with
interstitial quartzadularia. Bright orange
calcite overwhelms
much weaker brown CL
of adularia-quartz
assemblage
1.54 cm
Quartz-calcite-adularia vein
• Quartz-calcite-adularia vein. A
band of lattice-bladed calcite
has interstitial microcrystalline
quartz-adularia. Microdrusy
quartz partly lines voids within
intersecting calcite blades.
Calcite has bright orange CL
and overwhelms the much
subtler CL of adularia. The
microdrusy quartz has zoned
yellow CL (appears green in
the photo).
• CL; field of view= 11.57mm.
• Courtesy of Dr. James Clark.
2 mm
1.2 centimeter
DEWEY LIMESTONE
• Devonian from
Oklahoma
• Macro provides a
quick picture of the
different major
phases and serves as
a guide to more
detailed examination
5 cm.
CORAL
• Solitary coral,
Siphonophyllia
Sp., Co. Sligo,
perpendicular
to long
dimension.
• 14 kV, 1 m A,
2 seconds
• Sample from
Claire Mulhall,
Trinity College,
Dublin
5 cm.
2 mm
5 cm.
CORAL
• Solitary coral,
Siphonophyllia Sp., Co.
Sligo, parallel to long
dimension.
• 14 kV, 1 mA, 2 seconds
• Sample from Claire
Mulhall, Trinity College,
Dublin
5 cm.
5 cm
LIMESTONE DRILL CORE
• Partially dolomitised
Waulsortian
Limestone, Co.
Tipperary
• 14 kV, 1 mA, 2 sec.
• Sample from Claire
Mulhall, Trinity
College, Dublin
5 cm.
LIMESTONE DRILL CORE
• Limestone drill core
expanded X2 to
emphasize dolomite
crystals
2.5 cm.
MAP FOR MICRODRILLING
• Jay Kaufman, U. Md.
• Massive to finely laminated carbonate
from Namibia.
• Determined Mn/Sr, 87Sr/86Sr,C and O
isotopes from small selected areas.
• Kaufman et al., 1991, Precambrian
Research, 49, p. 301
• Kaufman et al., 1993, Earth and Planetary
Science Letters, 120, p.409
MICRODRILLING OF LAMINATED
CARBONATE
• MLM = moderately luminescent microspar
• LSLC = luminescent sparry calcite
• NLM = non-luminescent microspar
• WR = whole rock
Map for microdrilling
• Jay Kaufman et al from
proterozoic in Namibia.
• Drilled out samples from
1 mm diameter areas for
C and O isotopic
analyses
• WR = whole rock value.
Local values shown also
2.9 cm
Map for microdrilling
• Jay Kaufman et al,
• Drilled out 1 mm
areas for Mn/Sr and
87Sr/86Sr analyses.
• WR = whole rock
value. Local values
shown also
2.9 cm
Dr. Anthony N. Mariano
• Specialist in mineral deposits of all kinds
and especially those associated with rare
earths. Investigated them all over the
world on five continents.
• Has been using CL for more than 30
years.
• Dr. Anthony N. Mariano, Carlisle, MA USA
CARBONATITES
• Dr. Mariano uses macrophotos extensively
in his work on carbonatites and especially
likes to work with slabs.
• “Slabs give you a better picture of what the
rock really looks like and especially as an
initial overall look.” (Dr. Anthony Mariano)
Apatite Søvite – Okorusu, Namibia
• Light lilac – pink CL
apatite – LREE
activated
• Orange CL calcite,
Mn2+
• Non-CL - pyroxene
• 17 kV,0.8 mA
• All apatite in
carbonatite are LREE
46 millimeters
Søvite, Okorusu, Namibia
• Various stages of
calcite crystallization
showing variations in
orange to orange-red
CL, corresponding to
changes in trace
element content of
calcite with each
crystallization
episode.
• Also blue fluorite
46 mm
Nepheline Syenite, Okorusu, Namibia
• Light blue CL
plagioclase
• Grey (non-CL)
nepheline
• Dull red CL specks
are sodalite
• Not a carbonatite
46 mm in length
Fluorite ore and apatite, Okorusu,
Namibia
• Hydrothermal
mineralization of fluorite
and apatite
• light blue – zoned fluorite,
intrinsic
• light lilac-pink apatite,
LREE
• Really dark is quartz or
voids.
• Dr. Anthony N. Mariano
46 mm
Carbonatite, Matongo Bandaga, Burundi
• Blue apatite, LREE
activators
• Bright red, fenite
Fspars (Fe3+)
• dark areas are blue –
non-luminescing
pyroxenes (aegerine)
• Orange calcite
• Dr. Anthony N.
Mariano
46 mm
Contact between apatite – magnetite søvite
and fenite, Okorusu, Namibia
•
•
•
•
•
•
Fenite carbonatite contact
knob on upper right side is Søvite with
orange CL calcite, light blue CL apatite
and non-CL magnetite. Band on left is
dominant orange CL calcite that
drowns out red, Fe3+ activated CL, of
K feldspar. In plane light band is
leucocratic and in sharp contact with
central melanocratic band. The light
colored matrix is calcite and orthoclase
and the dark green disseminated
grains are diopside.
The central band contains non-CL
diopside and veins of dull grey CL
celsian (activator not known). First
reported occurrence of celsian
(BaAlSi3O8) in carbonatite.
Late bands are calcite
16 kV, 0.9 mA, 30 seconds, ASA
Dr. Anthony N. Mariano
46 mm
GEMSTONES
• Not surprisingly, gem stones are one of
the favorite candidates for CL
macrophotograpy.
• They are often large.
• They usually have an irregular, non-planar,
shape.
• Often they are not removable from their
mounts
SYNTHETIC DIAMOND
• Synthetic diamond CL
at room temperature
• Dr. C.M. Welbourn,
Diamond Sales, Ltd.
5.1 millimeters
SYNTHETIC DIAMOND
• Synthetic diamond CL
at low temperatures,
80 degrees K
• Dr. C. M. Welbourn,
Diamond Sales, Ltd.
5.1 millimeters
Dr. Johann Ponahlo
• Physical-chemist and gemologist.
• Has used CL macro macro techniques
for description and documentation of
natural and synthetic gemstones for more
than two decades.
• Dr. Johann Ponahlo, Vienna, Austria
• “Samples of considerable thickness and/or
of irregular shape can be studied as well
as specimens in their original settings and
even small figurines. “
• Dr. Johann Ponahlo
ZIRCONIA
• 30 carat zirconia
• 5 kV, 1 mA
• Dr. Johann Ponahlo
1.8 cm
SYNTHETIC GADOLINIUM GARNET
• Synthetic gadolinium
garnet; 5.8 mm
diameter, 3.7 mm
height.
• The CL spectrum
consists of narrow
bands of trivalent Eu
and Tb.
• 5 kV, 1 mA
• Dr. Johann Ponahlo
5.8 mm
CORUNDUM
• 12 carat synthetic
corundum
• Sample is brown in
natural light
• 5 kV, 1 mA
• Dr. Johann Ponahlo
~1.5 cm
AMAZONITE AND GROSSULARITE
• Yellow green is
grossularite
• Blue is amazonite, 7.2
carat. Bands clearly
identify sample as
feldspar
• 8 kV, 1 mA
• Ponahlo
8 mm
MOUNTED ALEXANDRITE
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•
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Right: Natural >20
carat alexandrite in its setting
from mine near the Takowaya
river where alexandrites first
discovered in 1830. Stone and
setting date back to 19th century.
Valued at 1.3 million euros.
Left: 22 carats synthetic
alexandrite made by Kyocera Inc.,
Japan (1990).
Natural stone CL is distinctly lower
than synthetic. Natural stone on
display in Museum for Natural
History, Vienna.
Dr. Johann Ponahlo.
Synthetic is blue green in daylight and
violet-tinted in artificial light
1.4 cm
Valued at 1.3
million euros
CHROMIUM DIOPSIDES FROM BRAZIL AND
RUSSIA
• Two on right are
natural diopsides from
Brazil
• Four on left are
natural diopsides from
Russia.
• 9 kV, 0.7 mA
• Dr. Johann Ponahlo
2.5 cm
COLORLESS TOPAZ,
SCAPOLITE, LEUCOSAPPHIRE
• Upper left is
leucosapphire
• Lower left is 4 carat
scapolite
• Blue is 13 carat cut
topaz
• 7.5 kV, 0.8 mA
• Dr. Johann Ponahlo
30 mm
SAPPHIRE AND CAT’S EYE APATITE
• Both cabochons are
nearly opaque and
colorless.
• Red CL is a sapphire
from Sri Lanka
• Yellow CL is Apatite
• 12 kV, 0.9 mA
• Dr. Johann Ponahlo
19.6 mm
YULETIDE TREE
• Regardless of one’s religious beliefs, a
decorated Yule time evergreen is always a
welcome sight. This particular “tree” was
created by Skip Palenik, Microtrace
Analytical, and his son Chris. The
illumination comes from the
cathodoluminescence of the various minerals
that they arranged.
MERRY XMAS FROM
MICROTRACE ANALYTICAL
•
•
•
•
Blue are zircon
Green are plagioclase
Pink is fluorapatite
Red is calcite
• Arranged by Chris
Palenik, Microtrace
Analytical
9.2 mm
ACKNOWLEDGMENTS
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Dr. James Clark, Applied Petrographics, Portland, OR
Dr. Shane Elen, GIA, Carlsbad, CA
Dr. Alan Kaufman, University of Maryland, College Park, MD
Dr. Anthony Mariano, Carlisle, MA
Dr. Claire Mulhall,Trinity College, Dublin
Dr. Christopher Palenik, Microtrace Analytical, Elgin, IL
Dr. Johann Ponahlo, Vienna, Austria
Dr. George Sevastopulo, Trinity College, Dublin
Dr. Chris Welbourn, DeBeers,UK
BIBLIOGRAPHY
•
Clark, Dr. James, Applied Petrographics, http://www.appliedpetrographics.com
•
Crookes, William1880. Contributions of molecular physics in high vacua. Magnetic
deflection of molecular trajectory, – laws of magnetic rotation in high and law vacua, phosphorogenic properties of molecular discharge. Philosophical Transactions of the
Royal Society of London, vol. 170, part II, 641-662.
•
Kaufman, A.J., Jacobsen, S.B. and Knoll, A.H. 1993. The Vendian record of C- and
Sr-isotopic variations: Implications for tectonics and paleoclimate. Earth and
Planetary Science Letters 120: 409-430.
Kaufman, A.J., Hayes, J. M., Knoll, A.H. and Germs, G.J.B. 1991. Isotopic
compositions of carbonates and organic carbon from Upper Proterozoic successions
in Namibia: Stratigraphic variation and the effects of diagenesis and
metamorphism. Precambrian Research 49: 301-327.
•
Welbourn, C.M., M. Cooper, and P. M. Spear 1996. De Beers Natural versus
synthetic diamond verification instruments, Gems and Gemology, p. 156-169.