TY - JOUR
T1 - Using Syntectonic Calcite Veins to Reconstruct the Strength Evolution of an Active Low-Angle Normal Fault, Woodlark Rift, SE Papua New Guinea
AU - Mizera, Marcel
AU - Little, Tim
AU - Boulton, Carolyn
AU - Katzir, Yaron
AU - Thiagarajan, Nivedita
AU - Prior, David J.
AU - Biemiller, James
AU - Smith, Euan G.C.
N1 - Funding Information:
Marsden Fund grant VUW1310 provided financial support to conduct this research. We are grateful to Hugh Davies (University of Papua New Guinea) and Ian Smith (University of Auckland) for providing field book scans and discussions. We thank Susan Ellis, Samuel Webber, Jürgen Österle, Laura Wallace, Kevin Norton, and Daniel Stockli for field support and discussions. Insightful reviews by Isabelle Manighetti, Bob Holdsworth, an anonymous reviewer and an expert Associate Editor (anonymous) improved the manuscript. Special thanks go to the many landowners, oral chiefs, elders, and citizens who granted us permission to study their land. We also thank our guides and carriers without whom this work would not have been possible.
Publisher Copyright:
© 2021. American Geophysical Union. All Rights Reserved.
PY - 2021/8/1
Y1 - 2021/8/1
N2 - Quantifying the strength evolution of faults that cut the lithosphere is essential to better understand seismicity in continental regions. We estimate differential stresses and principal stress orientations driving rapid slip of ∼10 mm/yr on the active Mai'iu low-angle normal fault (LANF), SE Papua New Guinea. The fault's mafic footwall hosts a well-preserved sequence of mylonite, (ultra-)cataclasite, and gouge. In these fault rocks, we combine stress inversion of fault-slip data and paleostress analysis of syntectonically emplaced calcite veins with microstructural and clumped-isotope geothermometry to constrain a syn-exhumational sequence of deformation stresses and temperatures, and to construct a stress profile through the exhumed footwall of the active Mai'iu LANF. This includes: (a) at ∼12–20 km depth (T ≈ 275–370°C), mylonites accommodated slip on the Mai'iu fault at low differential stresses (>25–135 MPa) before being overprinted by localized brittle deformation at shallower depths; (b) at ∼6–12 km depth (T ≈ 130–275°C) differential stresses in the foliated cataclasites and ultracataclasites were high enough (>150 MPa) to drive slip on a mid-crustal portion of the fault (dipping 30–40°), and to trigger brittle yielding of mafic footwall rocks in a zone of mixed-mode seismic/aseismic slip; and (c) at shallower crustal depths (T < 150°C; depth <6 km) on the most poorly oriented segment of the Mai'iu LANF (dipping ∼22°), slip occurred on frictionally weak clay-rich gouges (μ ≈ 0.15–0.38). Subvertical σ1 and subhorizontal σ3 parallel to the extension direction, with σ1 ≈ σ2 (constriction), reflect vertical unloading and 3-D bending strain during rolling-hinge style flexure of the footwall.
AB - Quantifying the strength evolution of faults that cut the lithosphere is essential to better understand seismicity in continental regions. We estimate differential stresses and principal stress orientations driving rapid slip of ∼10 mm/yr on the active Mai'iu low-angle normal fault (LANF), SE Papua New Guinea. The fault's mafic footwall hosts a well-preserved sequence of mylonite, (ultra-)cataclasite, and gouge. In these fault rocks, we combine stress inversion of fault-slip data and paleostress analysis of syntectonically emplaced calcite veins with microstructural and clumped-isotope geothermometry to constrain a syn-exhumational sequence of deformation stresses and temperatures, and to construct a stress profile through the exhumed footwall of the active Mai'iu LANF. This includes: (a) at ∼12–20 km depth (T ≈ 275–370°C), mylonites accommodated slip on the Mai'iu fault at low differential stresses (>25–135 MPa) before being overprinted by localized brittle deformation at shallower depths; (b) at ∼6–12 km depth (T ≈ 130–275°C) differential stresses in the foliated cataclasites and ultracataclasites were high enough (>150 MPa) to drive slip on a mid-crustal portion of the fault (dipping 30–40°), and to trigger brittle yielding of mafic footwall rocks in a zone of mixed-mode seismic/aseismic slip; and (c) at shallower crustal depths (T < 150°C; depth <6 km) on the most poorly oriented segment of the Mai'iu LANF (dipping ∼22°), slip occurred on frictionally weak clay-rich gouges (μ ≈ 0.15–0.38). Subvertical σ1 and subhorizontal σ3 parallel to the extension direction, with σ1 ≈ σ2 (constriction), reflect vertical unloading and 3-D bending strain during rolling-hinge style flexure of the footwall.
KW - brittle-ductile transition
KW - calcite
KW - crustal strength
KW - low-angle normal fault
KW - paleopiezometry
KW - paleostress
UR - http://www.scopus.com/inward/record.url?scp=85113379933&partnerID=8YFLogxK
U2 - 10.1029/2021JB021916
DO - 10.1029/2021JB021916
M3 - Article
AN - SCOPUS:85113379933
VL - 126
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
SN - 2169-9313
IS - 8
M1 - e2021JB021916
ER -