Evolution of zircon chemistry and inclusion paragenesis of I- to S-type granitoids from the Wilson Terrane of northern Victoria Land (Antarctica): Zircon as a record of dynamic continental crust formation
Zusammenfassung der Projektergebnisse
Based on single zircon grains from the Granite Harbour Intrusives (GHI) of the Wilson Terrane (WT) in northern Victoria Land (Antarctica) this project targeted three main topics: 1) The spatial and temporal evolution of the I- and S-type GHI sequences; 2) The specific geodynamic setting of the Wilson Terrane; 3) The development of tools using zircon as a record of continental crust formation. To 1) So far, the data presented here suggest a more complex evolution, and an earlier onset of the Ross Orogeny and the associated magmatism, than previously suggested. Our Pb-Pb data suggest a long-lived, more complex magmatic evolution of the GHI over the course of ca. 100 Ma with episodes of magmatic activity, clustering around ca. 580- 560, ca. 530-510 and ca. 500-480 Ma. The comparison of Pb-Pb ages with related isotopic, chemical and mineralogical features suggests that the youngest phase is potentially fluiddominated in some regions. The oldest age cluster is likely magmatic and not inherited. To 2) Based on the obtained Pb-Pb-ages so far, we currently interpret the GHI as the product of a long-lived active continental margin from ca. 580 to ca. 480 Ma. Whether the WT represents (i) the continental arc with a sedimentary cover and a cratonic basement, (ii) a deep sedimentary fore-arc basin on the craton-shelf exclusively, or (iii) whether it is transitional in between these settings may be answered by a detailed analysis of inherited zircon cores. In almost all samples inheritances with ages between 600 and 700/770 Ma can be found, which are so far statistically unresolvable. In three samples, which are each located on the outermost region of the investigated area, hence spanning the area, inherited ages between 1030 to 1100 Ma have been identified as well. Moreover, inheritance older than 1.3 and up to 3.4 Ga may not be recorded in all samples, but have been identified nearly everywhere beside the Lanterman Range. To 3) Developing clear diagnostic tools to use zircon as a record of continental crust formation was the main aim of this project, and it was relying heavily on the findings made in (1) and (2). However, with those findings being more complex than anticipated, the resulting conclusions for this subtopic are not straightforward. This project has shown that under certain conditions zircon ages can potentially record multiple events, surviving reworking and re-melting. However, they can be easily enough misleading and it can prove difficult to distinguish between mixed ages, annealing ages, inherited ages, or magmatic and alteration ages. This highlights the necessity to use zircon ages with care, and in combination with complimentary mineralogical and petrological data.
Projektbezogene Publikationen (Auswahl)
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(2015) Zircon chemistry of granitoids from the Wilson Terrane of northern Victoria Land (Antarctica): evidence for an immature Andean-type continental margin (Geoberlin, Berlin/ Deutschland)
Menneken M, John T, Läufer A, Berndt J
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(2015) Zircon Pb-Pb ages, chemistry and inclusion data of granitoids from the Wilson Terrane of northern Victoria Land (Antarctica): evidence for an immature Andean-type continental margin (26. Internationale Polartagung, München/ Deutschland)
Menneken M, John T, Läufer A, Berndt J, Giese J
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(2016) Early Paleozoic I- and S-Type Granitic Magmatism at the Pacific Margin of the Transantarctic Mountains (TAM): Dominantly a Crustal Recycling Process? Goldschmidt Abstracts, 2016; 1103 (Goldschmidt, Yokohama/ Japan)
Henjes-Kunst F, Gerdes A, Menneken M, Tribuzio R, Schüssler U, Zeh A
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(2016) Magmatic origin and fluid alteration versus inheritance: Complex history of accessory minerals from I-type granites from northern Victoria Land (Antarctica). (AGU Fall meeting, San Francisco/ USA)
Menneken M, John T, Läufer A, Berndt J, Henjes-Kunst F, Giese J
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(2018) Timing of subduction of the Palaeo-Pacific Ocean in northern Victoria Land (Antarctica) inferred from zircon U-Pb ages. (27. Internationale Polartagung, Rostock/ Deutschland)
Menneken M, John T, Läufer A, Berndt J, Giese J, Whitehouse M
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(2018) Zircons from the Granite Harbour Intrusives of northern Victoria Land (Antarctica) (Polar2018, Davos/Schweiz)
Menneken M, John T, Läufer A, Giese J
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(2019) Dating the Granite Harbour Intrusives of northern Victoria Land (Antarctica) - Magmatic ages, inheritance and alteration (XIII International Symposium on Antarctic Earth Sciences (ISAES), Incheon, Rep. Korea, 22-26 July 2019)
Menneken M, Läufer A, John T, Berndt J, Henjes-Kunst F, Giese J
