Sedimentary and volcaniclastic record of a mid-ocean spreading ridge: Macquarie Island, Southern Ocean
Sedimentary and volcaniclastic rocks formed within mid-ocean ridge spreading centers have received relatively little documentation compared to their counterparts found in continental margin and volcanic arc systems. Results presented in this thesis characterize a diverse sedimentary and volcaniclast...
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ftmacquariefig:oai:figshare.com:article/19431017 2023-05-15T13:41:11+02:00 Sedimentary and volcaniclastic record of a mid-ocean spreading ridge: Macquarie Island, Southern Ocean Ryan Adam Portner 2017-11-10T00:00:00Z https://doi.org/10.25949/19431017.v1 https://figshare.com/articles/thesis/Sedimentary_and_volcaniclastic_record_of_a_mid-ocean_spreading_ridge_Macquarie_Island_Southern_Ocean/19431017 unknown doi:10.25949/19431017.v1 https://figshare.com/articles/thesis/Sedimentary_and_volcaniclastic_record_of_a_mid-ocean_spreading_ridge_Macquarie_Island_Southern_Ocean/19431017 In Copyright Other education not elsewhere classified zircon Mid-ocean ridges Mid-ocean ridges -- Antarctic Ocean sediment mid-ocean ridge ophiolite Text Thesis 2017 ftmacquariefig https://doi.org/10.25949/19431017.v1 2022-12-28T08:42:42Z Sedimentary and volcaniclastic rocks formed within mid-ocean ridge spreading centers have received relatively little documentation compared to their counterparts found in continental margin and volcanic arc systems. Results presented in this thesis characterize a diverse sedimentary and volcaniclastic lithofacies assemblage exposed on the Macquarie Island ophiolite, which formed within a waning slow-spreading mid-ocean ridge. Petrography, geochemistry, and geochronology of detritus indicate that the sedimentary rocks were derived from submarine exposures of faulted Oligocene to Miocene age oceanic crust. The interaction of fault-derived gravity flows with a rugged mid-ocean ridge sea floor and strong bottom current of the Southern Ocean produced a unique depositional environment. Low grade zeolite metamorphism and in-situ uplift of Macquarie Island sedimentary rocks aided the preservation of delicate sedimentary structures otherwise deformed during continental obduction or drilling of modern day midoceanridge sediment. Isotope and trace element geochemistry of sandstone, gabbroic colluvium, and basalt indicates that Miocene Macquarie Island crust was derived from a much more enriched mantle source compared to the Oligocene age detritus. The recorded covariance in enrichment with time may be attributed to changes in spreading direction and shortening of spreading segments. Alternatively, long-offset transforms associated with the shortened segments likely separated a heterogeneous mantle source. This is supported by paleogeographic reconstructions that show >300km of offset between sources for the Oligocene detritus and Macquarie Island crust. Long-offset transforms along the waning spreading center also played a role in limiting magma mixing, which is preserved by geochemically variable sideromelanein volcaniclastic rocks. Distinct geochemistry within individual volcaniclastic rock units is attributed to discrete eruption episodes, which were primarily associated with non-explosive quench fragmentation ... Thesis Antarc* Antarctic Antarctic Ocean Macquarie Island Southern Ocean Research from Macquarie University Antarctic Southern Ocean Antarctic Ocean |
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Open Polar |
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Research from Macquarie University |
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ftmacquariefig |
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unknown |
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Other education not elsewhere classified zircon Mid-ocean ridges Mid-ocean ridges -- Antarctic Ocean sediment mid-ocean ridge ophiolite |
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Other education not elsewhere classified zircon Mid-ocean ridges Mid-ocean ridges -- Antarctic Ocean sediment mid-ocean ridge ophiolite Ryan Adam Portner Sedimentary and volcaniclastic record of a mid-ocean spreading ridge: Macquarie Island, Southern Ocean |
topic_facet |
Other education not elsewhere classified zircon Mid-ocean ridges Mid-ocean ridges -- Antarctic Ocean sediment mid-ocean ridge ophiolite |
description |
Sedimentary and volcaniclastic rocks formed within mid-ocean ridge spreading centers have received relatively little documentation compared to their counterparts found in continental margin and volcanic arc systems. Results presented in this thesis characterize a diverse sedimentary and volcaniclastic lithofacies assemblage exposed on the Macquarie Island ophiolite, which formed within a waning slow-spreading mid-ocean ridge. Petrography, geochemistry, and geochronology of detritus indicate that the sedimentary rocks were derived from submarine exposures of faulted Oligocene to Miocene age oceanic crust. The interaction of fault-derived gravity flows with a rugged mid-ocean ridge sea floor and strong bottom current of the Southern Ocean produced a unique depositional environment. Low grade zeolite metamorphism and in-situ uplift of Macquarie Island sedimentary rocks aided the preservation of delicate sedimentary structures otherwise deformed during continental obduction or drilling of modern day midoceanridge sediment. Isotope and trace element geochemistry of sandstone, gabbroic colluvium, and basalt indicates that Miocene Macquarie Island crust was derived from a much more enriched mantle source compared to the Oligocene age detritus. The recorded covariance in enrichment with time may be attributed to changes in spreading direction and shortening of spreading segments. Alternatively, long-offset transforms associated with the shortened segments likely separated a heterogeneous mantle source. This is supported by paleogeographic reconstructions that show >300km of offset between sources for the Oligocene detritus and Macquarie Island crust. Long-offset transforms along the waning spreading center also played a role in limiting magma mixing, which is preserved by geochemically variable sideromelanein volcaniclastic rocks. Distinct geochemistry within individual volcaniclastic rock units is attributed to discrete eruption episodes, which were primarily associated with non-explosive quench fragmentation ... |
format |
Thesis |
author |
Ryan Adam Portner |
author_facet |
Ryan Adam Portner |
author_sort |
Ryan Adam Portner |
title |
Sedimentary and volcaniclastic record of a mid-ocean spreading ridge: Macquarie Island, Southern Ocean |
title_short |
Sedimentary and volcaniclastic record of a mid-ocean spreading ridge: Macquarie Island, Southern Ocean |
title_full |
Sedimentary and volcaniclastic record of a mid-ocean spreading ridge: Macquarie Island, Southern Ocean |
title_fullStr |
Sedimentary and volcaniclastic record of a mid-ocean spreading ridge: Macquarie Island, Southern Ocean |
title_full_unstemmed |
Sedimentary and volcaniclastic record of a mid-ocean spreading ridge: Macquarie Island, Southern Ocean |
title_sort |
sedimentary and volcaniclastic record of a mid-ocean spreading ridge: macquarie island, southern ocean |
publishDate |
2017 |
url |
https://doi.org/10.25949/19431017.v1 https://figshare.com/articles/thesis/Sedimentary_and_volcaniclastic_record_of_a_mid-ocean_spreading_ridge_Macquarie_Island_Southern_Ocean/19431017 |
geographic |
Antarctic Southern Ocean Antarctic Ocean |
geographic_facet |
Antarctic Southern Ocean Antarctic Ocean |
genre |
Antarc* Antarctic Antarctic Ocean Macquarie Island Southern Ocean |
genre_facet |
Antarc* Antarctic Antarctic Ocean Macquarie Island Southern Ocean |
op_relation |
doi:10.25949/19431017.v1 https://figshare.com/articles/thesis/Sedimentary_and_volcaniclastic_record_of_a_mid-ocean_spreading_ridge_Macquarie_Island_Southern_Ocean/19431017 |
op_rights |
In Copyright |
op_doi |
https://doi.org/10.25949/19431017.v1 |
_version_ |
1766146560856424448 |