Kinematic, finite strain and vorticity analysis of the Sisters Shear Zone, Stewart Island, New Zealand

Ring, Uwe; Bernet, Matthias; Tulloch, A. J.

doi:10.1016/j.jsg.2015.02.004

Cited by 19 publications

(13 citation statements)

References 60 publications

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“…Stewart Island is predominantly composed of Carboniferous–Early Cretaceous granitic‐dioritic rocks (Allibone & Tulloch, , ), with the youngest granite dated at 105 Ma (Tulloch & Kimbrough, ). A major fault system, the Sisters Shear Zone (Kula et al, , ; Ring et al, ) exhumed midcrust along an ~70° trending detachment fault that dips ~20° SSE. The fault is parallel or subparallel to much of the eastern margin of the Campbell Plateau and cessation of rapid exhumation of the footwall, determined by 40 Ar/ 39 Ar thermochronometry on K‐feldspar at 78 and 83 Ma (two analyses from Kula et al, ), overlaps Campbell Plateau‐West Antarctica breakup and formation of new ocean crust at or just before chron 33o (79 Ma; Cande & Stock, ), that is, circa 80 Ma.…”

Section: Sample Descriptions and Analytical Resultsmentioning

confidence: 99%

“…Great South basin has up to 8.6 km thickness of sedimentary rocks, of which up to 4 km are Late Cretaceous in age (Cook et al, ; Sahoo et al, ). The basin is controlled on its NW side by the 89–80 Ma Sisters detachment fault (Kula et al, , ) of the Pegasus Metamorphic Core Complex (Ring et al, ). Canterbury Basin deepens east into the bathymetric Bounty Trough.…”

Section: Introductionmentioning

confidence: 99%

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Reconnaissance Basement Geology and Tectonics of South Zealandia

et al. 2019

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We report new U-Pb zircon ages, geochemical and isotopic data for Mesozoic igneous rocks, and new seismic interpretations of mostly submerged South Zealandia (1.5 Mkm 2 ). We use these data, along with existing geological and geophysical data sets, to refine the extent and nature of geological units. Our new 1:25 M geological map of South Zealandia provides a regional framework to investigate the rifting and breakup that formed Zealandia, Earth's most submerged continent. Samples of prerift (pre-100 Ma) plutonic rocks can be matched with on-land New Zealand igneous suites and indicate an east-west strike for the subduction-related 260 to 105-Ma Median Batholith across the Campbell Plateau. The plutonic chronology of formerly contiguous plutonic rocks in West Antarctica reveals similar pulses and lulls to the Median Batholith. Contrary to previous interpretations, the Median Batholith does not coincide with the 1,600-km-long Campbell Magnetic Anomaly System. Instead we interpret the continental magnetic anomalies to represent a mainly mafic igneous unit, whose shape and extent is controlled by synrift structures related to Gondwana breakup. Correlatives of some of these unsampled igneous rocks may be exposed as circa 85 Ma alkalic volcanic rocks on the Chatham Islands. Extension directions varied by up to 65°from 100 to 80 Ma, and we suggest this allowed this large area to thin considerably before final rupture to form new oceanic crust. Synrift (90-80 Ma) structures cut the oroclinal bend in southern South Island and support a pre-early Late Cretaceous age of orocline formation.

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Section: Sample Descriptions and Analytical Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reconnaissance Basement Geology and Tectonics of South Zealandia

et al. 2019

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“…Hence, the notion of a Late Cretaceous through Paleogene wider “Alpine Fault thermotectonic corridor” might be an artifact of Neogene transpression. In addition to the Late Cretaceous/Paleogene ages for high‐T metamorphism, there are also numerous Cretaceous/Paleogene low‐T thermochronologic ages across the South Island (Ring, Mortimer, et al, ; Tippett & Kamp, ) and Stewart Island (Reiners et al, ; Ring et al, ) (Table S6), which have hitherto hardly been considered in compilations for Late Cretaceous/Paleogene ages (Briggs et al, ; Cooper & Palin, ; Mortimer, ). However, when the lithosphere is deforming, there needs to be deformation compatibility, and ages for lower crustal high‐grade metamorphism are linked in some way with low‐T thermochronologic ages in the upper crust.…”

Section: Discussionmentioning

confidence: 99%

“…The interpretation of these, admittedly sparse, upper‐crustal thermotectonic data is that Zealandia was affected by a protracted NE‐SW‐directed extensional event in the Late Cretaceous. The Cretaceous low‐T ages from Stewart Island have been interpreted to reflect footwall cooling of a normal fault system resulting from NE‐SW extension (Kula et al, ; Ring et al, ). The high‐temperature thermochronologic ages would then reflect the deep‐crustal response to extension recorded by the low‐T ages in the upper crust.…”

Section: Discussionmentioning

confidence: 99%

“…The direction of extension was NE‐SW (Schulte et al, ; Tulloch & Kimbrough, ). The separation of New Zealand from Antarctica started later by ~100 Ma (Uruski & Ilg, ) and the Pacific‐Antarctica spreading ridge formed by ~76 Ma (Gaina et al, ), and the extension direction was NE‐SW (Kula et al, ; Ring et al, ). We suggest that the various extension directions reported above are related to these two extension events to the northwest and southeast of the South Island.…”

Section: Discussionmentioning

confidence: 99%

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Middle to Late Miocene Age for the End of Amphibolite‐Facies Mylonitization of the Alpine Schist, New Zealand: Implications for Onset of Transpression Across the Alpine Fault

et al. 2019

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We report five new Rb-Sr muscovite-based isochron ages, which are the first to constrain the timing of amphibolite-facies mylonitization of the Alpine Schist in the Southern Alps of New Zealand. The ages range from 13.1 ± 4.3 to 8.9 ± 3.2 Ma (2σ uncertainties) for mylonite directly above the Alpine Fault. The weighted mean age of 10.74 ± 0.57 Ma is within uncertainty of a published 40 Ar/ 39 Ar illite/mica upper-intercept age of 11.5 ± 0.5 Ma measured at the same locality. The end of amphibolite-facies mylonitization occurred at metamorphic conditions of~560-570°C and~0.9-1.1 GPa as derived from pseudosection analysis in the NCTiKFMASH system. We interpret Miocene metamorphism to reflect transpressional crustal thickening and formation of a thick crustal root supporting early Southern Alps topography at or prior to 10.74 ± 0.57 Ma. Additional~2-1 Ma Rb-Sr biotite, 40 Ar/ 39 Ar muscovite, and 40 Ar/ 39 Ar biotite ages reflect isotopic closure during rapid cooling along the Alpine Fault in the Pleistocene. The Miocene mylonitization ages and the Pleistocene cooling ages define a distinct two-stage cooling and exhumation history for the Alpine Schist with initial cooling of~10°C/Myr and exhumation rates of 2-4 km/Myr. Final cooling since~2 Ma was >100°C/Myr at exhumation rates of~5-6 km/Myr. We interpret the two-phase cooling history by movement of the mylonite through a strongly nonlinear thermal structure. An older 60.5 ± 0.7 Ma metamorphic event is also preserved as a Rb-Sr crystallization age of a predeformational muscovite-plagioclase assemblage in a sheared pegmatite.

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