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Tin belt rocks have heavier median zircon O isotope values 6. Zircon isotope and trace element plots highlighting source, plotted by sample and suite. Zircon isotopic and trace element signatures reaffirm that the igneous rocks in the two belts have different magmatic ages, are derived from different sources, and they underline the role of geodynamic setting in magma petrogenesis. A juvenile mantle signature dominates the copper arc, and the link between a subducting slab leading to oxidized intermediate magmas and Cu-Au mineralization is well established Tin belt granites are sourced from isotopically more evolved protoliths with little or no mantle input.
Such S-type magmas are typically generated in the mid- to lower-crust through the partial melting of dominantly metasedimentary source rocks, leading to reduced melts that can evolve towards Sn-W mineralization The interpreted accretionary setting driving the Myanmar magmatism has obvious parallels in both the Central Andes and other magmatic belts originating in similar geodynamic regimes.
Blevin et al. They showed certain metallogenic affinities plot within common domains, highlighting the relationship that Cu-Au and Sn-W associated granites have with differing degrees of redox and fractionation. This work provides a useful framework within which to assess the sensitivity of zircon geochemistry to metallogeny.
For the Myanmar whole-rock data, the size of the Eu anomaly increases, i. These ranges in log f O 2 are consistent with other published figures for Cu-Au and Sn-W deposits Practical application of zircons as monitors of magma fertility requires calibration of measured proxies. The concentration of Sn in the residual melt increases with magma fractionation until it reaches a critical threshold required for subsequent mineralization processes Identification of this threshold within zircon would have significant implications for monitoring Sn mineralization potential.
Calibration of a Sn threshold can be undertaken with real-world examples. The Zaaiplaats tin deposit is hosted in a granitic phase of the Bushveld Complex that represents a single magmatic pulse. Zaaiplaats, however, may be anomalously rich in Sn. Also plotted on the y-axis are aggregated and bucketed whole-rock Sn contents reported for major tin deposits from Southeast Asia Malaysia and Thailand , the Erzgebirge, Bolivia, Portugal, Nigeria, and the Massif Central, as summarized in Lehmann If Sn in zircon was measured directly, then assessing this threshold in zircon requires knowledge of the partitioning of Sn between zircon and melt.
Sensu Blundy and Wood 28 , the Sn zircon-melt partition coefficient D Sn is therefore likely to be similar to that for Nd for more reducing systems.
Published values of D Nd vary, but assuming a zircon-melt value of 3. We set out to assess whether source, redox and the degree of magma fractionation may be evaluated from the zircon record of two contrasting magmatic belts. The Myanmar zircon data show that Hf and O isotopes highlight the role of source in determining the initial metallogenic trajectory of resultant magma, with tin belt granites having a more evolved crustal source, comprising material that has previously experienced supracrustal processes, while the copper arc granites have a mantle-like, juvenile, isotopic signature.
We set out to recreate the metallogenic affinity diagram of Blevin et al.
Work by Ballard et al. More recently, Lu et al. Magma fractionation is a key process in the development of enhanced concentrations of incompatible metals, a necessary precursor to mineralization processes leading to deposits of those metals. We use the example of Sn mineralization to show how thresholds may be established in the trace element signatures of zircons, and which may be used to distinguish barren from fertile granites.
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Zircons have great potential to be developed into a useful exploration tool, especially within the detrital record, and our study suggests they may contain key information regarding pathfinding for lithophile elements. Zircons grains from all samples were separated using a combination of heavy liquid and Frantz magnetic separation techniques. Full analytical methodology is detailed in the supplementary information, and all analytical results including standard analyses are available in the supplementary data tables in Excel format.
Financial support was provided by the Oxford University Fell Fund ref.
NJG thanks Tony Kemp for early discussions. Electronic supplementary material. Supplementary information accompanies this paper at doi Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. National Center for Biotechnology Information , U.
Sci Rep. Published online Apr 7. Nicholas J. Gardiner , 1, 2 Chris J. Hawkesworth , 3 Laurence J.
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Robb , 1 Martin J. Whitehouse , 4 Nick M. Roberts , 5 Christopher L. Kirkland , 2 and Noreen J. Evans 6. Chris J. Laurence J. Martin J.
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Nick M. Christopher L. Noreen J. Author information Article notes Copyright and License information Disclaimer. Gardiner, Email: ua. Corresponding author. Received Nov 24; Accepted Mar Abstract Granitoid-hosted mineral deposits are major global sources of a number of economically important metals. Geology The paired magmatic belts of Myanmar are interpreted to have formed on the subducting margin of Neo-Tethys during the Late Mesozoic-Early Cenozoic Open in a separate window.
Figure 1. Table 1 Sample locations and a summary of key isotope and geochemical metrics as discussed in the text. Approach The mineral zircon provides an exceptional record of magmatic evolution Figure 2. Metallogenic Processes Blevin et al. Figure 3.
is granite an ore
Figure 4. Application To Tin Metallogeny Practical application of zircons as monitors of magma fertility requires calibration of measured proxies. Figure 5. Conclusions We set out to assess whether source, redox and the degree of magma fractionation may be evaluated from the zircon record of two contrasting magmatic belts. Methods Zircons grains from all samples were separated using a combination of heavy liquid and Frantz magnetic separation techniques. Electronic supplementary material Supplementary Information 1.
Dataset 1 K, xls. Author Contributions N. Notes Competing Interests The authors declare that they have no competing interests. Footnotes Electronic supplementary material Supplementary information accompanies this paper at doi References 1. Granite-related ore deposits. Economic Geology th Anniversary Volume , —