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The granitoids in the other areas of the Eastern Granitoid Province are barren.- The Western Granitoid Province (22–149 Ma) in northern Peninsular Thailand, western Thailand and Burma has biotite granite and hornblende-biotite granite/granodiorite.Tin deposits are associated with biotite granite, which probably is the dominant phase (14% of tin production).
The composition of TNO related to rare-element pegmatites is rather different from rare-metal granites: the latter have high REE and Th concentrations, and low Li and Mg.Columbite-group minerals (CGM) account for the majority of the current tantalum production; other Ta–Nb oxides (TNO) such as tapiolite, wodginite, ixiolite, rutile and pyrochlore-supergroup minerals may also be used.In this paper mineralogical and geochemical data with a focus on opaque minerals as well as age determinations on CGM using the U–Pb method are presented for 13 rare-element granite and pegmatite districts in Africa, covering Archean, Paleoproterozoic, Neoproterozoic, Paleozoic and Mesozoic provinces.In addition, other trace elements (Mo, Sn, and U) are also closely correlated with W and REE signatures.The Fe-rich garnets are attributed to rapid growth by infiltration metasomatism during disequilibrium, which caused the incorporation of these trace elements into the garnet structure that reflect the composition of the ore-forming fluid.Garnets in the study area are mainly composed of grandite (grossular–andradite) garnets, and exhibit compositional variation as oscillatory zoning.
The chondrite-normalized REE patterns of Al-rich garnets are HREE-enriched. Tungsten is strongly fractionated into the Fe-rich garnets (average concentration: 618 ppm), compared to the Al-rich rims (average concentration: 19 ppm).
In general, CGM from Ta-ore provinces are characterised by the predominance of one type of REE distribution pattern characterised by ratios between individual groups of REE (light, middle, heavy REE) and the presence and intensity of anomalies (e.g. Despite textural complexities such as complex zoning patterns and multiple mineralisation stages, the chemical compositions of CGM, tapiolite and wodginite–ixiolite from rare-metal granite and rare-element pegmatite provinces indicate that they are cogenetic and reflect specific source characteristics that may be used to discriminate among rocks of different origin.
Geochronological data produced for CGM from ore districts are discussed together with the respective ore mineralogy and minor and trace element geochemistry of TNO to reconsider the geodynamics of pegmatite formation.
Trace elements are incorporated in TNO in a systematic fashion, e.g.
wodginite and ixiolite carry higher Ti, Zr, Hf, Sn and Li concentrations than CGM and tapiolite.
Most of the tin deposits are associated with Main Range-type plutons (28% of tin production).