Slow‐to‐Fast Deformation in Mafic Fault Rocks on an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New Guinea
Abstract Slip on the active Mai'iu low‐angle normal fault in Papua New Guinea that dips 15–24° at the surface has exhumed in its footwall a single, continuous fault surface across a >25‐km‐wide dome. Derived from a metabasaltic protolith, the fault zone consists of a <3‐m‐thick zone of go...
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| Format: | Article |
| Language: | English |
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Wiley
2020-11-01
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| Series: | Geochemistry, Geophysics, Geosystems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2020GC009171 |
| _version_ | 1797637971974815744 |
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| author | M. Mizera T. Little C. Boulton D. Prior E. Watson J. Biemiller J. White Norio Shigematsu |
| author_facet | M. Mizera T. Little C. Boulton D. Prior E. Watson J. Biemiller J. White Norio Shigematsu |
| author_sort | M. Mizera |
| collection | DOAJ |
| description | Abstract Slip on the active Mai'iu low‐angle normal fault in Papua New Guinea that dips 15–24° at the surface has exhumed in its footwall a single, continuous fault surface across a >25‐km‐wide dome. Derived from a metabasaltic protolith, the fault zone consists of a <3‐m‐thick zone of gouges and cataclasites that overprint a structurally underlying carapace of extensional mylonites. Detailed microstructural and geochemical data, combined with chlorite‐based geothermometry, reveal changing deformation processes and conditions in the Mai'iu fault rocks as they were exhumed. The microstructure of nonplastically deformed actinolite grains inherited from the fine‐grained (6–35 µm) metabasaltic protolith indicates that shearing at depth was controlled by diffusion creep accompanied by grain‐boundary sliding of these grains together with chlorite neo‐crystallization at T > 275°C–370°C. In a foliated cataclasite unit at shallower crustal levels (T ≈ 150°C–275°C), metasomatic reactions accompanied fluid‐assisted mass transfer processes that accommodated aseismic, distributed shearing; pseudotachylites and ultracataclasites in the same unit indicate that such creep was punctuated by episodes of seismic slip—after which creep resumed. At the shallowest levels (T < 150°C), gouges contain abundant saponite, a frictionally weak mineral that promotes creep on the shallowest dipping (≤24°), most poorly oriented part of the Mai'iu fault. Our field, microstructural and geochemical data of freshly exhumed fault rocks support geodetic, seismological, and geomorphic evidence for mixed seismic‐to‐aseismic slip on this active low‐angle normal fault. |
| first_indexed | 2024-03-11T12:55:54Z |
| format | Article |
| id | doaj.art-c9fbeda26f864ab8888f4485fd68802a |
| institution | Directory Open Access Journal |
| issn | 1525-2027 |
| language | English |
| last_indexed | 2024-03-11T12:55:54Z |
| publishDate | 2020-11-01 |
| publisher | Wiley |
| record_format | Article |
| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj.art-c9fbeda26f864ab8888f4485fd68802a2023-11-03T17:01:17ZengWileyGeochemistry, Geophysics, Geosystems1525-20272020-11-012111n/an/a10.1029/2020GC009171Slow‐to‐Fast Deformation in Mafic Fault Rocks on an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New GuineaM. Mizera0T. Little1C. Boulton2D. Prior3E. Watson4J. Biemiller5J. White6Norio Shigematsu7Faculty of Geosciences Utrecht University Utrecht The NetherlandsSchool of Geography Environment and Earth Sciences Victoria University of Wellington Wellington New ZealandSchool of Geography Environment and Earth Sciences Victoria University of Wellington Wellington New ZealandDepartment of Geology University of Otago Dunedin New ZealandGNS Science Lower Hutt New ZealandInstitute for Geophysics Jackson School of Geosciences University of Texas at Austin Austin TX USADepartment of Earth Sciences University of New Brunswick Fredericton CanadaResearch Institute Earthquake and Volcano Geology Geological Survey of Japan Tsukuba Ibaraki JapanAbstract Slip on the active Mai'iu low‐angle normal fault in Papua New Guinea that dips 15–24° at the surface has exhumed in its footwall a single, continuous fault surface across a >25‐km‐wide dome. Derived from a metabasaltic protolith, the fault zone consists of a <3‐m‐thick zone of gouges and cataclasites that overprint a structurally underlying carapace of extensional mylonites. Detailed microstructural and geochemical data, combined with chlorite‐based geothermometry, reveal changing deformation processes and conditions in the Mai'iu fault rocks as they were exhumed. The microstructure of nonplastically deformed actinolite grains inherited from the fine‐grained (6–35 µm) metabasaltic protolith indicates that shearing at depth was controlled by diffusion creep accompanied by grain‐boundary sliding of these grains together with chlorite neo‐crystallization at T > 275°C–370°C. In a foliated cataclasite unit at shallower crustal levels (T ≈ 150°C–275°C), metasomatic reactions accompanied fluid‐assisted mass transfer processes that accommodated aseismic, distributed shearing; pseudotachylites and ultracataclasites in the same unit indicate that such creep was punctuated by episodes of seismic slip—after which creep resumed. At the shallowest levels (T < 150°C), gouges contain abundant saponite, a frictionally weak mineral that promotes creep on the shallowest dipping (≤24°), most poorly oriented part of the Mai'iu fault. Our field, microstructural and geochemical data of freshly exhumed fault rocks support geodetic, seismological, and geomorphic evidence for mixed seismic‐to‐aseismic slip on this active low‐angle normal fault.https://doi.org/10.1029/2020GC009171low‐angle normal faultsdiffusion creepgrain‐boundary slidingfluid‐assisted mass transferpseudotachylitesseismic‐to‐aseismic slip |
| spellingShingle | M. Mizera T. Little C. Boulton D. Prior E. Watson J. Biemiller J. White Norio Shigematsu Slow‐to‐Fast Deformation in Mafic Fault Rocks on an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New Guinea Geochemistry, Geophysics, Geosystems low‐angle normal faults diffusion creep grain‐boundary sliding fluid‐assisted mass transfer pseudotachylites seismic‐to‐aseismic slip |
| title | Slow‐to‐Fast Deformation in Mafic Fault Rocks on an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New Guinea |
| title_full | Slow‐to‐Fast Deformation in Mafic Fault Rocks on an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New Guinea |
| title_fullStr | Slow‐to‐Fast Deformation in Mafic Fault Rocks on an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New Guinea |
| title_full_unstemmed | Slow‐to‐Fast Deformation in Mafic Fault Rocks on an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New Guinea |
| title_short | Slow‐to‐Fast Deformation in Mafic Fault Rocks on an Active Low‐Angle Normal Fault, Woodlark Rift, SE Papua New Guinea |
| title_sort | slow to fast deformation in mafic fault rocks on an active low angle normal fault woodlark rift se papua new guinea |
| topic | low‐angle normal faults diffusion creep grain‐boundary sliding fluid‐assisted mass transfer pseudotachylites seismic‐to‐aseismic slip |
| url | https://doi.org/10.1029/2020GC009171 |
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