Evidence of Middle Jurassic magmatism within the Seychelles microcontinent: Implications for the breakup of Gondwana

J. G. Shellnutt; T. Y. Lee; H. Y. Chiu; Y. H. Lee; J. Wong

doi:10.1002/2015GL066036

Evidence of Middle Jurassic magmatism within the Seychelles microcontinent: Implications for the breakup of Gondwana

J. G. Shellnutt^*, T. Y. Lee, H. Y. Chiu, Y. H. Lee, J. Wong

^*Corresponding author for this work

Department of Earth Sciences (Include Institute of Marine Environmental Science and Technology)

Research output: Contribution to journal › Article › peer-review

13 Citations (Scopus)

Abstract

The breakup of East and West Gondwana occurred during the Jurassic, but the exact timing is uncertain due to the limited exposure of rocks suitable for radioisotopic dating. Trachytic rocks from Silhouette Island, Seychelles, yielded a range of zircon ages from Paleoproterozoic to Cenozoic. The ²⁰⁶Pb/²³⁸U age of the trachyte is 64.9 ± 1.6 Ma (Danian) but the majority of zircons yielded an age of 163.8 ± 1.8 Ma (Callovian) with a small subset yielding an age of 147.7 ± 4.5 Ma (Tithonian). The Hf isotopes of the Callovian (ε_Hf(t) = +4.1 to +13.4) and Danian (ε_Hf(t) = +1.9 to +7.1) zircons indicate that they were derived from moderately depleted mantle sources whereas the Tithonian zircons (ε_Hf(t) = -7.0 to -7.3) were derived from an enriched source. The identification of middle Jurassic zircons indicates that rifting and magmatism were likely contemporaneous during the initial separation of East and West Gondwana.

Original language	English
Pages (from-to)	10207-10215
Number of pages	9
Journal	Geophysical Research Letters
Volume	42
Issue number	23
DOIs	https://doi.org/10.1002/2015GL066036
Publication status	Published - 2015 Dec 16

Keywords

Callovian
Gondwana
Hf Isotopes
Seychelles
Tithonian
U/Pb dating

ASJC Scopus subject areas

Geophysics
General Earth and Planetary Sciences

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10.1002/2015GL066036

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title = "Evidence of Middle Jurassic magmatism within the Seychelles microcontinent: Implications for the breakup of Gondwana",

abstract = "The breakup of East and West Gondwana occurred during the Jurassic, but the exact timing is uncertain due to the limited exposure of rocks suitable for radioisotopic dating. Trachytic rocks from Silhouette Island, Seychelles, yielded a range of zircon ages from Paleoproterozoic to Cenozoic. The 206Pb/238U age of the trachyte is 64.9 ± 1.6 Ma (Danian) but the majority of zircons yielded an age of 163.8 ± 1.8 Ma (Callovian) with a small subset yielding an age of 147.7 ± 4.5 Ma (Tithonian). The Hf isotopes of the Callovian (εHf(t) = +4.1 to +13.4) and Danian (εHf(t) = +1.9 to +7.1) zircons indicate that they were derived from moderately depleted mantle sources whereas the Tithonian zircons (εHf(t) = -7.0 to -7.3) were derived from an enriched source. The identification of middle Jurassic zircons indicates that rifting and magmatism were likely contemporaneous during the initial separation of East and West Gondwana.",

keywords = "Callovian, Gondwana, Hf Isotopes, Seychelles, Tithonian, U/Pb dating",

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AU - Shellnutt, J. G.

AU - Lee, T. Y.

AU - Chiu, H. Y.

AU - Lee, Y. H.

AU - Wong, J.

PY - 2015/12/16

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N2 - The breakup of East and West Gondwana occurred during the Jurassic, but the exact timing is uncertain due to the limited exposure of rocks suitable for radioisotopic dating. Trachytic rocks from Silhouette Island, Seychelles, yielded a range of zircon ages from Paleoproterozoic to Cenozoic. The 206Pb/238U age of the trachyte is 64.9 ± 1.6 Ma (Danian) but the majority of zircons yielded an age of 163.8 ± 1.8 Ma (Callovian) with a small subset yielding an age of 147.7 ± 4.5 Ma (Tithonian). The Hf isotopes of the Callovian (εHf(t) = +4.1 to +13.4) and Danian (εHf(t) = +1.9 to +7.1) zircons indicate that they were derived from moderately depleted mantle sources whereas the Tithonian zircons (εHf(t) = -7.0 to -7.3) were derived from an enriched source. The identification of middle Jurassic zircons indicates that rifting and magmatism were likely contemporaneous during the initial separation of East and West Gondwana.

AB - The breakup of East and West Gondwana occurred during the Jurassic, but the exact timing is uncertain due to the limited exposure of rocks suitable for radioisotopic dating. Trachytic rocks from Silhouette Island, Seychelles, yielded a range of zircon ages from Paleoproterozoic to Cenozoic. The 206Pb/238U age of the trachyte is 64.9 ± 1.6 Ma (Danian) but the majority of zircons yielded an age of 163.8 ± 1.8 Ma (Callovian) with a small subset yielding an age of 147.7 ± 4.5 Ma (Tithonian). The Hf isotopes of the Callovian (εHf(t) = +4.1 to +13.4) and Danian (εHf(t) = +1.9 to +7.1) zircons indicate that they were derived from moderately depleted mantle sources whereas the Tithonian zircons (εHf(t) = -7.0 to -7.3) were derived from an enriched source. The identification of middle Jurassic zircons indicates that rifting and magmatism were likely contemporaneous during the initial separation of East and West Gondwana.

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Evidence of Middle Jurassic magmatism within the Seychelles microcontinent: Implications for the breakup of Gondwana

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