Copper isotopic composition

The copper isotope composition of waters actively weathering copper minerals could have distinctly heavy copper isotope signatures and indicate... 

The lead and copper isotopic composition of copper ores from the Sierra Morena (Spain). Journal of Iberian Geology 35(l) 59-68... 

Gale, N. H., Woodhead, A. P., Stos-Gale, Z. A., Walder, A., and Bowen, I. (1999). Natural variations detected in the isotopic composition of copper possible applications to archaeology and geochemistry. International Journal of Mass Spectrometry 184 1-9. 

Luais B, Telouk P, Albarede F (1997) Precise and accurate neodymium isotopic measurements by plasma-source mass spectrometry. Geochim Cosmochim Acta 61 4847-4854 Marechal C, Telouk P, Albarede F (1999) Precise analysis of copper and zinc isotopic compositions by plasma-source mass spectrometry. Chem Geol 156 251-273... 

The lead isotope ratios indicate an upper cmstal source for the lead and are consistent with mineralization at 800 Ma. Tracer isotopes in carbonates and chalcocite concentrates indicate that an external fluid altered the dolomitic unit changing its isotopic composition as well as deposited copper mineralisation. 

Chlorine is the major anion in surface- and mantle-derived fluids. It is the most abundant anion in hydrothermal solutions and is the dominant metal complexing agent in ore forming environments (Banks et al. 2000). Despite its variable occurrence, chlorine isotope variations in natural waters conunonly are small and close to the chlorine isotope composition of the ocean. This is also true for chlorine from fluid inclusions in hydrothermal minerals which indicate no significant differences between different types of ore deposits such as Mississippi-Valley and Porphyry Copper type deposits (Eastoe et al. 1989 Eastoe and Guilbert 1992). 

Magna T, Wiechert U, Halhday AN (2006) New constraints on the lithium isotope composition of the Moon and terrestrial planets. Earth Planet Sci Lett 243 336-353 Mardchal CN, Albarede E (2002) Ion-exchange fractionation of copper and zinc isotopes, Geochim Cosmochim Acta 66 1499-1509... 

Motyka, R.J., Hawkins, D.B., Poreda, R.J. and Jeffries, A. (1986) Geochemistry, Isotopic Composition, and the Origin of Fluids Emanating from Mud Volcanoes in the Copper River Basin, Alaska, Alaska Division of Geological and Geophysical Surveys, Public-data File 86-34, p. 87. 

Mar chal, C.N., Albarede, F., and Emmanuel, N. (1997) Natural variations in copper and zinc isotopic compositions. In Seventh Annual V.M. Goldschmidt Conference, 131-132, LPI Contribution No. 921, Lunar and Planetary Institute Houston. 

In the case of lead arsenate (acid form), calcium arsenate, and sodium arsenate, the Pb-isotopic compositions closely match those of sulfides from porphyry copper deposits from southeastern Arizona, specifically from the Pima and Silver Bell districts (Bouse et al., 1999). Notably, other major historical producers of arsenic trioxide (e.g., Anaconda Copper Co., US Smelting Co., Jardine Mining Co.) used... 

Bouse, R. M., Ruiz, J., Tidey, S. R., Tosdal, R. M., and Wooden, J. L. (1999). Lead isotope compositions of Late Cretaceous and Early Tertiary igneous rocks and sulfide minerals in Arizona Implications for the sources of plutons and metals in porphyry copper deposits. Econ. Geol. 94, 211-224. 

Fuel, chiefly charcoal, usually has a low lead content and, in many cases, the trees from which it came were growing near the ore deposit and tend to have incorporated lead of the same isotopic composition as the ore deposit. In most cases, the isotope composition of lead in the smelted copper has not been perturbed away from that of lead in the copper ore. Further isotopic comparisons of copper ores and associated Bronze Age copper slags are needed to examine this question more extensively. Comparisons that have already been made bear out the hypotheses just advanced. 

Figure 4. Lead isotope compositions for ores and copper slags from Cyprus. Copper ores, umbers, galena and copper slags have lead isotopic compositions falling into the same field. Error bars at the 95% level for the lead isotope ratios are shown on this and subsequent figures. (Reproduced with permission from ref. 3. Copyright 1986 University of Birmingham.)...

The application of lead isotope analyses to provenancing almost pure copper artifacts seems relatively straightforward in most instances, but what of arsenical copper and tin bronze alloys In principle, the arsenic in arsenical copper may have been derived from high-arsenic minerals (such as tennantite or basic copper arsenates) containing lead of a different isotopic composition from that of the copper ore used to produce the copper. However, absolutely no archaeological or other evidence of proves that this was ever done in the Bronze Age Aegean. On the contrary, at Kythnos definite evidence shows that arsenical copper was produced in EBII times from arsenical copper ores of variable (sometimes zero) arsenic content but of uniform lead isotope composition. 

Tin bronze is another matter because, apart from rare copper ore deposits also containing tin (e.g., some of those in Cornwall), tin from a quite different source than the copper has almost always been added to copper to produce bronze. The only tin mineral that is likely to contain lead is stannite, which is not common except as a mineralogical curiosity. Tin has always been obtained in very large quantities from cassiterite, which almost never contains even a trace of lead. The tin ingots found underwater off the coast of Israel contain no lead. Our work on Cypriot Late Bronze Age bronzes indicates no perturbation away from the characteristic Cypriot lead isotope composition, even for bronzes containing 18% tin. 

Figure 6. Lead isotope compositions for the Kythnos Hoard and Early Cycladic copper-based alloy artifacts from Amorgos.

Figure 9 shows the results of the lead isotope analyses of these objects compared with the lead isotope composition of the objects from Kastri on Syros and Chalandriani. On the basis of our measurements of the amount of variation in lead isotopic composition found for other copper ore deposits, we have estimated approximate bounds for at least five different copper ore sources from which Trojan copper must have been derived. As yet, there is not enough lead isotope data on the Anatolian copper ore deposits to be able to directly link the estimated lead isotope fields with particular copper occurrences. However, because the lead isotope composition is, to a first approximation, controlled by the geological age of the ore deposit, these five different ore sources, of widely different lead isotope compositions, must have been formed at quite different times. 

Figure 9. Lead isotope compositions for Early Bronze Age copper-based alloy artifacts from Troy II and artifacts from Kastri and Chalandriani on Cycladic island of Syros. The lead isotope fields indicated by broken lines are approximate. Model ages calculated in millions of years on the basis of Cummings and Richards (1975) model Jit are indicated for each grouping of lead isotope data. (Reproduced with permission from ref. 6. Copyright 1984 Basil Blackwell...

Some of the objects from Kastri falling in Trojan field B need further discussion. Four of these objects (16167, 16169, 16171, and 16174) have lead isotope compositions that resemble the fingerprint of Cypriot copper ores however, we have rejected the hypothesis that these metal objects at Kastri are Cypriot in origin by comparing their trace elemental composition, particularly gold and silver content, with some Cypriot copper artifacts excavated on Cyprus. The results of the neutron activation analyses of these objects are presented in Figure 11. 

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