50thKaikoura05 -1- Kaikoura 2005 CHARACTERISATION OF NEW ...

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the bulk strength of the Pacific Plate crust above the Alpine Fault ramp. The shears also provided a means for suprahydrostatic metamorphic fluids to escape upwards, acting as a closely spaced array of planar, vertical conduits cutting across the otherwise low permeability (1 x 10 -18 m 2 ) schist. We calculate that an aqueous fluid volume of 5.6 x 10 10 m 3 was required to deposit the 1-3 mm thick veins that currently seal the backshears throughout the 30 km-long by ~2 km-wide array, equivalent to an integrated fluid flux of 486000 m 3 /m 2 . Upward draining of this metamorphic fluid into the hangingwall would have left the underlying source region near its base residually drier. Fluid expulsion may thus have accomplished a net devolatilisation and rheological strengthening along the Alpine mylonite zone at depth at the same time that hydrolytic weakening softened structurally higher rocks in the hanging-wall. These fluid-related strength changes may have limited the degree to which the Alpine Fault could slip in the plate motion direction without some partitioning of deformation into its hanging-wall. POSTER COLLAPSE AND RE-GROWTH OF MONOWAI SUBMARINE VOLCANO, KERMADEC ARC, 1998-2004 Ian C. Wright 1 , William W. Chadwick 2 , Cornel E. J. de Ronde 3 , Dominique Reymond 4 , Olivier Hyvernaud 4 , Stephen Bannister 3 , Peter Stoffers 5 & Kevin Mackay 1 1 National Institute of Water and Atmospheric Research, 301 Evans Bay Parade, Greta Point, Private Bag 14-901, Kilbirnie, Wellington, 6003, New Zealand 2 CIMRS, Oregon State University, 2115 SE OSU Drive, Newport, OR, 97365, USA 3 Institute of Geological & Nuclear Sciences, 30 Gracefield Road, PO Box 31-312, Lower Hutt, New Zealand 4 Laboratoire de Geophysique, CEA/DASE/LDG, Tahiti, P.O. Box 640, Papeete, French Polynesia 5 Institute of Geosciences, University of Kiel, Kiel, Germany (k.mackay*niwa.co.nz) Monowai submarine volcano is located at 25°53.5’S/177°11.1’W, about 1400 km NNE of New Zealand along the Kermadec arc, and consists of a shallow symmetrical cone with a summit depth of ~100 m. Monowai is one of the most active submarine volcanoes in the Kermadec arc, based on visual reports from overflights, oceanographic surveys of hydrothermal plumes, and seismoacoustic monitoring from French Polynesia and elsewhere. Since the late 1970’s, Monowai has been the source of frequent swarms of acoustic Twave events every few years. On 24 May 2002 there was a particularly large seismoacoustic event with a duration of 6-8 minutes and an exceptional amplitude that was 4-5 times larger than any other T-wave signal recorded from Monowai. Bathymetric surveys of Monowai that bracket this event were collected with multibeam sonars in 1998 and 2004 by R/V Sonne (Hydrosweep) and R/V Tangaroa (EM300), respectively. A new collapse feature is apparent on the SE side of the volcano in the 2004 bathymetry. The two surveys were compared using a quantitative technique that has been used for documenting depth changes due to volcanic eruptions on mid-ocean ridges. The results of this comparison show that the summit depth of Monowai changed from 69 m below sealevel in 1998 to 135 m in 2004, a difference of - 66 m, and the location of the shallowest point moved ~200 m to the NNW. However, the maximum depth change between the surveys is - 105 m and is located near the 1998-summit, which in 2004 is south of the new headwall scarp on the SE flank of the volcano. The total area of significant depth change is 1.26 x 10 6 m 2 ,andthe decrease in volume is 6.12 x 10 7 m 3 (or 0.06 km 3 ). From the distribution of the depth changes it is also clear that four things occurred between the surveys: removal of volume from slope failure, the subsequent addition of volume from an eruptive vent within the new slide scar, the removal of part of that additional volume by a further slope failure, and the addition of more volume within the eruptive vent. Therefore, the volume removed by slope failure was probably closer to 0.1 km 3 whereas the volume added back by eruption is approximately 0.03 km 3 . It is not known whether the slide triggered the eruption or visa versa, but the recent history of frequent volcanic activity at Monowai suggests that an eruption-triggered slide maybemorelikely. POSTER FINGERPRINTING SLAB–DERIVED AQUEOUS FLUIDS IN THE MANTLE SOURCES OF ARC LAVAS: AN EXAMPLE FROM THE SOUTHERN KERMADEC ARC R.J. Wysoczanski 1 ,I.C.Wright 2 ,J.A.Gamble 3 , E.H. Hauri 4 , J.F. Luhr 5 ,S.M.Eggins 6 , &M.R.Handler 1 1 IFREE, Japan Agency for Marine Earth Science and Technology, Yokosuka, Japan. 2 National Institute of Water and Atmospheric Research, Wellington, New Zealand. 3 Dept. of Geology, National University of Ireland, University College Cork, Ireland. 4 Dept. of Terrestrial Magnetism, Carnegie Institution of Washington, USA. 50 th Kaikoura05 -98- Kaikoura 2005
5 Dept. of Mineral Sciences, Smithsonian Institution, Washington, USA. 6 Research School of Earth Sciences, Australian National University, Canberra. (richardw*jamstec.go.jp) Convergent margins, where oceanic lithosphere is subducted back into the mantle, form the key interface for large–scale element recycling between ocean, crust, mantle, and atmosphere. Recycling of elements in occurs as sediments and altered oceanic crust (AOC) in the subducting slab dehydrate and/or melt, releasing water and mobile elements into the overlying mantle wedge, initiating melting and the generation of arc magmatism. The composition of arc magmas reflects these multiple sources and is further complicated by assimilation of arc crust and hydrothermal fluids and brines as the magma ascends. Deconvolving the origin and transport mechanism of slab fluids and melts in subduction zones requires identifying tracer elements specific to a source and/or mechanism. Fluid-mobile elements such as Cl, Ba, and Pb provide the potential to investigate the composition and source of aqueous fluids derived from the subducting slab in arc systems. In the southern Kermadec arc – Havre Trough (KAHT) pillowbasalt glasses have water (~1.5 wt.%) and carbon (
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CHARACTERISATION OF NEW ZEALAND NEP
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myrtaceous. One 20 mm diameter flow
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ange of lower resolution or fragmen
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CRETACEOUS-EOCENE TRANSGRESSION MAR
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consists of a well-developed canyon
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model. The relative position of the
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converts to plate theory. Thus, the
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and on the following morning the mi
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the LGM grass peak. This period of
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offshore west coast to offshore eas
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4 Institut de Recherche pour le Dé
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VEGETATION AND CLIMATE CHANGE AT TH
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wider range. The youngest layer has
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few normal faults visible especiall
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TRACKING CRUSTAL DIFFERENTIATION AN
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EMPIRICAL SCALING RELATIONS FOR SEI
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hydrovolcanic eruptions then took p
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and that the MTL marks a Late Carbo
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faunal changes within these cores w
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material at subsurface depths of se
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survived through in low numbers in
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in the TVZ and southern Havre Troug
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Tephra beds are commonly used to ai
Page 47 and 48: The MCC is bounded by deep-seated t
Page 49 and 50: distal alluvial plains where large
Page 51 and 52: Many of the molluscs in the highly
Page 53 and 54: incremental slip history and paleoe
Page 55 and 56: This paper explores what we know of
Page 57 and 58: volcanism and a linear vent oriente
Page 59 and 60: These areas are also described in
Page 61 and 62: 3D IMAGING OF THE FORE- AND BACKTHR
Page 63 and 64: ascending methane fluids/gases of p
Page 65 and 66: THE GRIFFENS ROAD TEPHRAS: VALUABLE
Page 67 and 68: sideritic concretions that occur in
Page 69 and 70: with 63.8%, and then [3] with 49.9%
Page 71 and 72: U-Th-Ra disequilibria data. In part
Page 73 and 74: landslide tsunami in the past. Rece
Page 75 and 76: core complex mode, temperature driv
Page 77 and 78: truncating three plutonic suites of
Page 79 and 80: active, andesitic White Island volc
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Page 83 and 84: oundaries and with immature source
Page 85 and 86: The new era of commercial viability
Page 87 and 88: TECTONICS OF THE GALATEA BASIN USIN
Page 89 and 90: performed by the electron backscatt
Page 91 and 92: 25km northeast of the volcano. Alth
Page 93 and 94: Most of the tectonic blocks in the
Page 95 and 96: TECTONIC AND NON-TECTONIC CAUSES OF
Page 97: The continental shelf of the Povert
Page 101 and 102: Adams CJ...........................
Page 103 and 104: Naish T............................
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