2'11' Isotope Separation

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2.11. Isotope Separation Analysis
Isotope ratios for specific elements can change
locally due to geological, climatological,
biological, chemical and physical processes
during the history of the earth.
The analysis of isotope ratios is a unique tool
for provenance studies as seen in previous
examples.
Typical isotope ratios used for provenance
studies 13C/12C 18O/16O 204Pb/208Pb
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Stable isotopic ratios
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Determination of the Pb isotope ratio
Neutron activation technique on 204Pb or 208Pb ?
204Pb(n,?)205Pb
208Pb(n,?)209Pb
Not possible since the cross section is extremely
weak and 205Pb and 209Pb have no characteristic ?
decay radiation!
Alternative method isotope analysis by mass
separation techniques!
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Separation in magnetic fields
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Example Separation of 204Pb and 208Pb
B
R1
R2

Separated 204Pb, 208Pb beams
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Mass spectrum in focal plane detector
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Isotope Analyzer
Small sample of material with mass lt?g is
ionized by sputter technique, accelerated and
mass separated by sequence of magnetic and
electrical fields
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Origin of Hittite Mining Industry
Tin bronze statue
The Hittite empire had an extensive metallurgy
and mining industry in the early bronze age,
1500-1300 BC.
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Hittite Mining Site determination by lead (Pb)
isotope analysis
Control over the mining sites was important for
Hittite empire trade
Origin of metal in artifact is determined by
their 207Pb/206Pb isotope ratio
Metal contain tin, copper, nickel and lead!
A. Yener, Bibl. Archaeologist 58 (1995) 101-107
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The importance of lead isotopes
There are 4 stable lead isotopes 204Pb, 206Pb,
207Pb, 208Pb
Lead isotope distribution is not necessarily
constant but may change if significant Uranium
Plutonium abundance exist in in the ore material.
Natural decay of these a unstable isotopes feed
the Pb isotopes.
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Natural decay chains the feeding of Pb isotopes
208Pb
207Pb
206Pb
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Pb isotopic ratio
Depending on chemical history and water content
of ore material significant differences exist in
abundances of long-lived mother U, Np, Pt
elements in the ore material. This eventually
leads to build-up of significant differences in
lead daughter isotopic abundances, which often
is characteristic for the mine site.
Present day lead primeval lead radiogenic lead
Simple evolution model tp time between origin
of earth and last geo- logical active period
l238 decay constant of 238U l235 decay constant
of 235U l232 decay constant of 232Th
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Evolution model applied for US mines
Certain lead isotope ratios help to identify the
original mines, the analysis of the lead isotope
ratio reveals ancient trading routes
Present isotope ratio parameters
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Ancient ship trade ca 1500 BC
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Difficulty of Underwater Archaeology
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Egyptian trading vessel at Uluburun Kas
C. Pulak, Int. J. of Naut. Arch. 27(1998)
188 - 224
G. F. Bass, Amer. J. Archaeology 90 (1986) 269-296
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The Uluburun Wreck
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Copper and tin ingots
Copper ingots
Tin ingot
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Origin and destination?Did the ship sail west or
east
Origin of copper and tin can be tested on the
mine specific lead isotope ratio in the ingots.
Typical lead ratio of Taurus mines
Typical lead ratio of ship ingots
Lead concentration in copper and tin
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Trading Route