Hunter fracture zone

The Hunter fracture zone is a sinistral (left-lateral) transform faulting fracture zone,^[1] that to its south is part of a triple junction with the New Hebrides Trench, and the North Fiji Basin Central Spreading Ridge.^[2] The Hunter fracture zone, with the Hunter Ridge, an area with recent volcanic activity to its north, is the southern boundary of the North Fiji Basin.^[3] This boundary area in the south-western part of the Hunter fracture zone is associated with hot subduction, and a unique range of volcanic geochemistry.^[4]

Hunter fracture zone
Fiji Vanuatu New Caledonia Zealandia North  Fiji Basin   Lau Basin New Hebrides   Trench   Hunter fracture     zone     Lau   Ridge South   Fiji Basin Tonga Trench Minerva Abyssal   Plain  Tonga-  Kerm-   adec Ridge    Cook fracture   zone Colville   Ridge Three Kings Ridge Geographical and geological relationships of the Hunter fracture zone. Zealandia is outlined in black.
Etymology	Hunter Island
Coordinates	20.667°S 177.0°W / -20.667; -177.0
Tectonics
Plate	Australian, New Hebrides and the Conway Reef microplate
Status	Active
Age	Miocene-current

Geography

The Hunter fracture zone is located to the south and southwest of Fiji and starts where the southern part of the New Hebrides Trench ends due to the increasing obliqueness of convergence lending to more strike slip faulting than subducting. It terminates around the International Date Line, with the Kadavu Islands immediately to its north.^[5] However some earlier work has postulated that the fault structures around Suva on Fiji itself are related and different authors have defined the zone variably.^[6]

Seismicity

Approximate surface projection on Pacific Ocean of tectonic seismic zones near Hunter fracture zone including spreading activity in the North Fiji Basin to its north. White land top right are islands of Fiji. Key:'"`UNIQ--templatestyles-0000000F-QINU`"'

  Up to 70 km (43 mi) deep shallow-focus earthquakes

'"`UNIQ--templatestyles-00000010-QINU`"'

  70–300 km (43–186 mi) deep shallow-focus earthquakes

'"`UNIQ--templatestyles-00000011-QINU`"'

  More than 300 km (190 mi) deep shallow-focus earthquakes

'"`UNIQ--templatestyles-00000012-QINU`"'

  (orange) Hunter fracture zone

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  (blue) Active subduction trenches (New Hebrides Trench)

'"`UNIQ--templatestyles-00000014-QINU`"'

  (light blue) Inactive trenches

'"`UNIQ--templatestyles-00000015-QINU`"'

  (brown) Selected oceanic floor ridges (Hunter Ridge)

'"`UNIQ--templatestyles-00000016-QINU`"'

  (yellow) Spreading centers or rifts

. Mouse over shows feature names.

The western Hunter fracture zone is an area of fair shallow seismicity.^[7] Large (more than M_w6) earthquakes have occurred in historic times.^[8]

Tectonics

It defines part of the plate boundary between the New Hebrides and the Conway Reef microplate with the Australian plate, with the rest of the convergence being accommodated by subduction and rifting. The major present subduction and rifting is in an area where the Hunter Ridge is being split that is called the Monzier Rift.^[9]. This is active volcanically as part of a separate subduction system to the rest of the Vanuatu subduction zone that has been called the Matthew and Hunter subduction zone.^[10] The Hunter Ridge and Hunter fracture zone are the south eastern terminus of the Vanuatu subduction zone's subduction and its associated slab edge. From 3 million years ago the southernmost Central Spreading Ridge of the North Fiji Basin propagated southward and has now intersected with the New Hebrides Trench and the Hunter fracture zone to form the current triple junction.^[1]

See also

• List of fracture zones

References

1. Durance et al. 2012, p915
2. Durance et al. 2012, p929
3. Sigurdsson, IA; Kamenetsky, VS; Crawford, AJ; Eggins, SM; Zlobin, SK (1993). "Primitive island arc and oceanic lavas from the Hunter ridge–Hunter fracture zone. Evidence from glass, olivine and spinel compositions". Mineralogy and Petrology. 47 (2): 149–69. Bibcode:1993MinPe..47..149S. doi:10.1007/BF01161564. S2CID 53477063.
4. Durance et al. 2012, p929
5. Begg, Graham (13 July 2002). "Arc dynamics and tectonic history of Fiji based on stress and kinematic analysis of dikes and faults of the Tavua Volcano, Viti Levu Island, Fiji". Tectonics. 21 (4): 1023. Bibcode:2002Tecto..21.1023B. doi:10.1029/2000TC001259. S2CID 129542546.
6. Shorten, GG (1990). "Structural geology of Suva Peninsula and Harbour and its implications for the Neogene tectonics of Fiji". New Zealand Journal of Geology and Geophysics. 33 (3): 495–506. Bibcode:1990NZJGG..33..495S. doi:10.1080/00288306.1990.10425704.
7. Hamburger, MW; Isacks, BL (1994). "Shallow Seismicity in the North Fiji Basin". Shallow seismicity in the north Fiji basin. In Basin Formation, Ridge Crest Processes, and Metallogenesis in the North Fiji Basin. Circum-Pacific Council for Energy and Mineral Resources Earth Science Series. Berlin, Heidelberg: Springer Berlin Heidelberg. pp. 21–32. doi:10.1007/978-3-642-85043-1_3. ISBN 9783642850431. Retrieved 4 July 2023.
8. "Seismotectonics of the Eastern Margin of the Australia Plate" (PDF). Retrieved 3 July 2023.
9. McCarthy et al. 2022, 1. Introduction.
10. McCarthy et al. 2022, 2.1. The Vanuatu – Hunter Ridge subduction system.

Sources

• Durance, PM; Jadamec, MA; Falloon, TJ; Nicholls, IA (1 August 2012). "Magmagenesis within the Hunter Ridge Rift Zone resolved from olivine-hosted melt inclusions and geochemical modelling with insights from geodynamic models". Australian Journal of Earth Sciences. 59 (6): 913–31. Bibcode:2012AuJES..59..913D. doi:10.1080/08120099.2012.682096. S2CID 67848457.
• McCarthy, A; Falloon, TJ; Danyushevsky, LV; Sauermilch, I; Patriat, M; Jean, MM; Maas, R; Woodhead, JD; Yogodzinski, GM (15 July 2022). "Implications of high-Mg# adakitic magmatism at Hunter Ridge for arc magmatism of the Fiji-Vanuatu region". Earth and Planetary Science Letters. 590 (117592). Bibcode:2022E&PSL.59017592M. doi:10.1016/j.epsl.2022.117592. hdl:20.500.11850/553552.