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

More documents

Recommendations

Info

large volumes of A-type magmatism in Queensland may shed light on the significance of its apparently rare equivalent in NZ. Thus A-type magmatism at ~130 Ma in NZ may explain the sudden major HiSY flux as being due to heat associated with an otherwise largely unrecognised incursion of asthenospheric mantle-derived magmas, probably by slab rifting or roll back. In Queensland, by analogy, the “extension-related” magmatism may also have been “intra-arc”, rather than strictly intracontinental. ORAL PROGRESS ON QMAP FIORDLAND Turnbull 1 , A. Allibone 2 , R. Jongens 1 , H. Fraser 1 ,A.Tulloch 1 1 Institute of Geological and Nuclear Sciences, Private Bag 1930, Dunedin 2 School of Earth Science, James Cook University, Townsville, Q4811, Australia (i.turnbull*gns.cri.nz) Work on the Fiordland QMAP sheet has been under way for four field seasons with the southern twothirds of Fiordland now largely mapped. Some of the more significant findings of the work to date are highlighted on this poster. Schistose amphibolite facies metasediments, previously interpreted as the upper plate of a Western Fiordland Block, are now known to extend as far south as Chalky Inlet rather than terminating in Dusky Sound. These metasediments, and several younger granitoid units, strike across the mouth of Dusky Sound and indicate that the Dusky Fault does not extend out to sea as previously postulated. Movement is instead accommodated on a major SW-trending fault that crosses the coast near West Cape; consequently the Dusky Fault, previously thought to separate distinct Western and Southern Fiordland Blocks, appears to be of local rather than regional importance. Ordovician graptolitic shales and interbedded sandstone and quartzite previously included in a Southern Fiordland Block, as well as the schistose amphibolite facies rocks, are intruded by the Brothers and c. 350 Ma Evans Plutons, indicating that they have been in close proximity since the mid Paleozoic. The c. 30+ granitoid plutons mapped show regional variations in composition and age across southern Fiordland. Carboniferous plutons are largely confined to the area between Dusky Sound and the Princess Mountains, and include at least 3 distinct groups, one of which correlates with the Ridge Orthogneiss on Stewart Island. Gabbroic, dioritic and related LoSY granodioritic rocks, c. 170-140 Ma old, similar to those mapped in northern Stewart Island and northeastern Fiordland, form a belt of heterogeneous variably deformed intrusions that extends from northeast of Lake Manapouri to the Princess Mountains. The presence of the c. 164 Ma Lake Mike Granite in SW Fiordland indicates this Jurassic plutonism locally extended further west. Younger HiSY plutons, correlated with the Separation Point Suite, form a narrow belt extending south from the western side of Lake Manapouri to Lake Poteriteri. Elsewhere in southern Fiordland, Cretaceous HiSY rocks are restricted to isolated plutons in the eastern Hunter Mountains and south of Dusky Sound. Numerous LoSY tonalitic to leucogranitic plutons, some dated at c. 130-135 Ma, occur in SW Fiordland; their affinity with other documented suites is not yet clear. Cretaceous and Cenozoic sedimentary rocks had generally been mapped and described prior to the QMAP programme. However, newly discovered fossiliferous Pleistocene sediments that fill a submarine canyon east of Puysegur Point give valuable control on tectonic uplift rates for flights of marine terraces in SW Fiordland. The Grebe Shear Zone, previously interpreted as the boundary between Eastern and Southern Fiordland Blocks, is cut by probably Early Cretaceous (Separation Point Suite) granitoids, implying correlation with the Gutter Shear Zone on Stewart Island. Innumerable brittle faults have been mapped; some offset the contacts of the Western Fiordland Orthogneiss. Demonstrable Late Quaternary faulting is rare. POSTER WORKING TOWARD A HIGH-PRECISION RECORD OF MT TARANAKI ERUPTIONS AND ASH FALLS, NEW ZEALAND M. Turner 1 , S. Cronin 1 ,M.Bebbington 2 , B. Stewart 1 ,V.Neall 1 and I. Smith 3 1 Institute of Natural Resources, Massey University, Palmerston North, New Zealand 2 Institute of Information Sciences and Technology, Massey University, Palmerston North, New Zealand 3 Department of Geology, University of Auckland, Auckland, New Zealand (M.B.Turner*massey.ac.nz) A probabilistic assessment of eruption recurrence at any volcano requires quantification of the frequency and magnitude of each style of possible volcanic hazard. Existing eruption age data for frequency analysis at Taranaki is, as for many volcanoes, poorly constrained and relies on a few radiocarbon dates from widely distributed stratigraphic sections on and around the volcano. We have extracted what seems to be the highest resolution record yet of Taranaki volcanism from peaty lacustrine sediments within a small lake, 50 th Kaikoura05 -90- Kaikoura 2005
25km northeast of the volcano. Although not directly downwind of Mt Taranaki, this site holds >90 Holocene tephras, which have been sampled within the top 4 m of sediment. Ten new radiocarbon dates throughout the length of this core enable a very detailed sedimentation rate curve to be established and each individual tephra layer can be assigned an age based on its position within the core. This key site is correlated to syn-eruptive deposits in other locations, including those on the edifice, by physical and petrological characteristics as well as titanomagnetite mineral chemistry fingerprinting techniques. By using these tephras as age horizons, other proximal eruption deposits which are not in the distal record can also be assigned a relative age and added to the event database. The new database will be used to develop the first comprehensive probabilistic eruption forecast for ash eruptions from Mt Taranaki. A probabilistic temporal model is then required to handle the stochastic nature of the observed record, as well as the imprecision and inaccuracy inherent in the age data obtained via radiocarbon dating/sedimentation rates and that of the correlation uncertainties. Such models are usually assembled using techniques from renewal theory, (marked) point processes, or hidden (semi-)Markov models. Combining the resulting model with a quantitative assessment of the styles and properties of eruptions possible at Taranaki will allow the model parameters to be estimated, and the goodness of fit to the observed record assessed. A suitably well fitting model can then provide a probabilistic forecast of future eruptions at Taranaki. POSTER MASS TRANSFER IN SUBDUCTION ZONES: AN ELEMENTAL AND ISOTOPIC PERSPECTIVE Simon Turner & Rhiannon George GEMOC, Macquarie University, Sydney, NSW, 2109, Australia (sturner*els.mq.edu.au) Little doubt remains that subduction zone lavas contain elements recycled from the subducting slab. However, whether the key agents of this mass transfer are fluids, supercritical fluids or melts has major implications for the thermal structure of the mantle wedge. The evidence for contributions from both subducted sediment and altered oceanic crust are compelling and in most arcs their relative proportions vary inversely. Thus, so-called “fluidrich” lavas with high Ba/Th and Sr.Th ratios have low 87 Sr/ 86 Sr and 10 Be/ 9 Be etc and the converse is true for the so-called “sediment-rich”lavas with elevated La/Sm. A complicating factor is that many individual arcs tend to be dominated by one endmember. Nevertheless, experimental partition coefficient data are consistent with the differences between the fluid and sediment components being formed in the presence of different residual mineralogies. Sediment fluids appear to be poor in incompatible elements, relative to those derived from altered oceanic crust and cannot easily replicate the sediment end-member. We suggest that subducted sediments dehydrate at relatively shallow levels and that these fluids are not strongly sampled by arc lavas. Altered oceanic crust may dehydrate more extensively and to greater depths and may be buffered against melting. Model melts of dehydrated sediment residues provide a much better simulation of the inferred sediment endmember but may require ~800 C at ~ 2GPa, consistent with recent temperature-dependant viscosity models. These general inferences are strongly supported by 10 Be and U-series isotope data which suggest that the sediment (melt) endmember is added 100’s kyr to several Myr prior to eruption whereas addition of fluid components continues until a few 1000 yrs prior to eruption. Thus, the fluid and sediment end-member contributions are separate in composition, space and time. These data argue strongly against the involvement of any single supercritical fluid. ORAL DEVELOPMENTS IN THE EAST COAST BASIN, NORTH ISLAND, NEW ZEALAND. Chris Uruski, Brad Field, Rob Funnell, Chris Hollis, Andy Nicol & Guy Maslen Institute of Geological & Nuclear Sciences PO Box 30368 Lower Hutt, New Zealand (c.uruski*gns.cri.nz) The East Coast Basin saw oil production in the late 19 th century from wildcat wells near oil seeps. By the mid-20 th century, geology was being applied to oil exploration, but with little success. In the late 20 th century seismic techniques were added to the exploration arsenal and several gas discoveries were made. At each stage it was recognised that exploration in this difficult but tantalising basin required more information than was available. Continuing work by exploration companies as well as by the Institute of Geological & Nuclear Sciences (GNS) has begun to reduce the risk of exploration. Source rocks have been identified and sophisticated thermal models show that petroleum is being generated and expelled from them as witnessed by the more than 300 oil and gas seeps onshore. Numerous reservoir facies have been recognised from outcrop studies and depositional models are being refined. All components of petroleum systems have been demonstrated to be 50 th Kaikoura05 -91- Kaikoura 2005
Page 1 and 2:
CHARACTERISATION OF NEW ZEALAND NEP
Page 3 and 4:
myrtaceous. One 20 mm diameter flow
Page 5 and 6:
ange of lower resolution or fragmen
Page 7 and 8:
CRETACEOUS-EOCENE TRANSGRESSION MAR
Page 9 and 10:
consists of a well-developed canyon
Page 11 and 12:
model. The relative position of the
Page 13 and 14:
converts to plate theory. Thus, the
Page 15 and 16:
and on the following morning the mi
Page 17 and 18:
the LGM grass peak. This period of
Page 19 and 20:
offshore west coast to offshore eas
Page 21 and 22:
4 Institut de Recherche pour le Dé
Page 23 and 24:
VEGETATION AND CLIMATE CHANGE AT TH
Page 25 and 26:
wider range. The youngest layer has
Page 27 and 28:
few normal faults visible especiall
Page 29 and 30:
TRACKING CRUSTAL DIFFERENTIATION AN
Page 31 and 32:
EMPIRICAL SCALING RELATIONS FOR SEI
Page 33 and 34:
hydrovolcanic eruptions then took p
Page 35 and 36:
and that the MTL marks a Late Carbo
Page 37 and 38:
faunal changes within these cores w
Page 39 and 40: material at subsurface depths of se
Page 41 and 42: survived through in low numbers in
Page 43 and 44: in the TVZ and southern Havre Troug
Page 45 and 46: 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
Page 81 and 82: and voluminous than at any on Earth
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: performed by the electron backscatt
Page 93 and 94: Most of the tectonic blocks in the
Page 95 and 96: TECTONIC AND NON-TECTONIC CAUSES OF
Page 97 and 98: The continental shelf of the Povert
Page 99 and 100: 5 Dept. of Mineral Sciences, Smiths
Page 101 and 102: Adams CJ...........................
Page 103 and 104: Naish T............................
show all

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

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?