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| Titel |
Mineral inclusions in sublithospheric diamonds from Juina, Brazil: Subducted protoliths, carbonated melts and protokimberlite magmatism |
| VerfasserIn |
Michael Walter, Galina Bulanova, Chris Smith, Lora Armstrong, Simon Kohn, Jon Blundy, Luiz Gobbo |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250036190
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| Zusammenfassung |
| A suite of Type II Diamonds from the Cretaceous Collier 4 kimberlite pipe, Juina Kimberlite
Field, Brazil, include syngenetic mineral inclusions comprising a remarkable range of
compositions that include calcium- and titanium-rich perovskite, Ca-rich majoritic garnet,
olivine, TAPP phase, CAS phase, K-hollandite phase, SiO2, FeO, native iron, low-Ni
sulphides, and Ca-Mg carbonate. The diamonds also exhibit a range in carbon isotopic
composition (δ13C ) that effectively spans that observed in the global diamond
population. Diamonds with heavy, mantle-like δ13C (-5 to -10) contain mineral inclusions
indicating a transition zone origin from mafic protoliths. Diamonds with intermediate
δ13C (-12 to -15) contain inclusions with chemistry indicating crystallization from
near-primary and differentiated carbonated melts derived from oceanic crust in the deep
upper mantle or transition zone. Diamonds with extremely light δ13C (~ -25) host
inclusions with chemistry akin to high pressure-temperature phases expected to
form in the transition zone from subducted pelagic sediments. Collectively, the
Collier 4 diamonds and their inclusions indicate multi-stage growth histories in
dynamically changing chemical environments. A 206Pb/238U age of 101±7 Ma on a
CaTiSi-perovskite inclusion is close to the kimberlite emplacement time (93.1 ±1.5 Ma).
This young inclusion age, together with the chemical and isotopic characteristics
indicating the role of subducted materials, suggest a model in which the generation of
sublithospheric diamonds and their inclusions, and the proto-kimberlite magmas, are related
genetically to the interaction of subducted lithosphere and a Cretaceous plume. |
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