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[en] A brief outline is given of the theory and techniques of the potassium-argon, rubidium-strontium and fission-track dating methods and related isotope studies which are currently in use at the Institute of Nuclear Sciences, DSIR. Some limitations of each technique are set out in terms of age range and materials for dating, and the appropriate choice of various mineral and rock types and subsequent age interpretations are discussed. The organisation of project proposals and categories is described and procedures for sample submission and documentation are given

[en] This paper presents an account of carrying out a hazard analysis to define the safety requirements for an autonomous robotic excavator. The work is also relevant to the growing generic class of heavy automated mobile machinery. An overview of the excavator design is provided and the concept of a safety manager is introduced. The safety manager is an autonomous module responsible for all aspects of system operational safety, and is central to the control system's architecture. Each stage of the hazard analysis is described, i.e. system model creation, hazard definition and hazard analysis. Analysis at an early stage of the design process, and on a system that interfaces directly to an unstructured environment, exposes certain issues relevant to the application of current hazard analysis methods. The approach taken in the analysis is described. Finally, it is explained how the results of the hazard analysis have influenced system design, in particular, safety manager specifications. Conclusions are then drawn about the applicability of hazard analysis of requirements in general, and suggestions are made as to how the approach can be taken further

[en] The Coromandel Peninsula comprises the central subaerial part of the late Cenozoic Cormandel Volcanic Zone (CVZ) of New Zealand and hosts the Hauraki Goldfield. Some 73 K-Ar and 9 zircon fission-track dates representative of 28 lithographic volcanic units mapped on the peninsula are reported, and more than 250 major element analyses of volcanic rocks, including all the dated rocks, have been collated and their broad geochemical affinities used to underpin the stratigraphy and volcanic history of the region

[en] Several of the present mountain ranges of the West Coast of New Zealand were the site of basin sedimentation during the Tertiary. The Paparoa Range, South Island, New Zealand, is one such example. It is composed of Early Cretaceous and older granitoid and gneissic suites which were first unroofed in the Cretaceous during a period of extension associated with the fragmentation of the Pacific margin of Gondwana. Burial in the late Eocene - Oligocene occurred as Tertiary sediments accumulated on this basement. A second period of uplift removed the sedimentary cover and exposed the basement rocks once again to the surface. Fission-track dating of zircons and apatites from these basement rocks yields ages which constrain these periods of movement. Zircon ages are Cretaceous and indicate that most of the basin was not buried to depths greater than 8 km. The apatite ages show irregular but progressive younging from east to west, which is interpreted as an increase in amount of resetting. The eastern edge retains apatite ages (c. 72 Ma) typical of the major Late Cretaceous uplift/cooling event recognised in earlier studies and considered here as the 'basement' apatite age. Westward, the amount of annealing, equated with depth of Tertiary burial and/or increased uplift rate, generally increases to the point where the Cretaceous age is replaced by one of Miocene resetting. Groupings of apatite fission-track ages are tentatively interpreted as representing small blocks with slightly different thermotectonic histories, separated by faults trending in a NNE-SSW direction, which may have controlled both burial and uplift. (author). 22 refs., 4 figs., 2 tabs

[en] Full text: Nine zircon and eighteen apatite fission-track analyses have been made in order to determine the low temperature cooling history of the Shuswap metamorphic core complex, western Canada. The zircons vary in apparent age from 53.9 ± 5.6 to 37.5 ± 5.0 Ma and the apatites from 48.5 ± 3.2 to 27.7 ± 3.4 Ma. In the footwall of the detachment faults defining the core complex, the cooling histories show a similarity until temperatures of ∼250 C were reached at about 45 Ma. From then on, activity on two normal faults, the Columbia River Fault and the Victor Creek Fault, controlled the regional cooling pattern. The ages and the combination of ages fall into four groups and on the basis of the fission-track data, we suggest that the region can now be divided into four thermotectonic units which are the result of differing tectonic controls during regional extension. Additionally, a complete cooling history of the Shuswap core complex can now be reconstructed, using constraints from U-Pb, Rb-Sr and K-Ar age data from several authors as well as the fission track results presented here. Copyright (1999) Geological Society of Australia

[en] Basement rocks of Paleogene sedimentary basins form the present physiographic highs on the West Coast of South Island, New Zealand. Apatite and zircon fission-track ages of these basement rocks allow interpretations to be made on the depths of Paleogene burial and the Miocene uplift history of the Victoria Range. Apparent apatite fission-track ages increase generally with elevation from 10 to 37 Ma. The ages of the high-altitude samples represent uplift of rocks that have been only partially annealed during burial, while the young samples (i.e., those between 10 and 16 Ma) have been buried sufficiently deeply to allow annealing of all pre-existing tracks. A rapid uplift pulse at this time reflects a major phase of compressional tectonics. Zircon ages also exhibit a general altitudinal correlation, but are not fully reset, and hence indicate that burial was to depths of less than 8 km. (author). 17 refs., 2 figs., 2 tabs

[en] Complete and partial annealing of fission tracks is a phenomenon often associated with regions that have undergone tectonism: it is generally identified by a length reduction of the spontaneous fission tracks. Depending on the mineral type and dating technique used, it is not always appropriate to measure track length. In a study of ages of the granitoid rocks of the West Coast, South Island, New Zealand, it became apparent that at some sites the fission tracks in zircons and sphenes had undergone varying degrees of annealing, identified by the large spread of single crystal ages relative to the estimated uncertainties. The data also indicate that different grains of the same mineral may have different annealing characteristics. We have attempted a new approach to the problem by determining age clusters based on a weighted least squares criterion to delineate any significant groupings. In cases of complete to partial annealing the youngest age cluster so defined may better represent the last cooling event than the sample as a whole. Examples are presented, but it is stressed that the approach should be used with caution in order that geological interpretations are meaningful. (author)

[en] A cold-fluid model for a self-organized electron spiral toroid (EST) is presented. In the present model, the electrons are assumed to undergo energetic spiral motion along a hollow torus with a fixed ion background, the electron mean free path is assumed to be long compared with the torus size, and the minor radius of the EST is assumed to be small compared with the major radius. Using this model, the equilibrium and stability properties of the electron flow in the self-organized EST are analyzed. It is found that a class of self-organized EST equilibria exists with or without an externally applied toroidal magnetic field. It is shown that in the absence of any applied toroidal magnetic field, the EST equilibria are stable at high electron densities (i.e., at high toroidal self-magnetic fields), although they are unstable at low electron densities (i.e., at low toroidal self-magnetic fields)

[en] New LA-ICP-MS U-Pb zircon ages of tuffs, from the northern Taranaki coastal section constrain depositional ages of the Mount Messenger Formation to 9.69 ± 0.12 and 9.43 ± 0.17 Ma at the Mohakatino and Tongaporutu rivers, respectively, and the Urenui Formation near Waiau Stream to 8.45 ± 0.10 Ma. Our preferred new radiometric-biostratigraphic age model comprises lower and upper intervals characterised by relatively low and high un-decompacted sedimentation rates of 102 ± 96 m/Ma (MSWD = 6.0) and 1358 ± 144 m/Ma (MSWD = 1.32), respectively. The poor linear fit to the lower interval could indicate either variable sedimentation rates, or an unconformity (0.7 ± 0.2 Ma) in the upper Mohakatino Formation or at the base of the Mount Messenger Formation. The 1569 m-thick upper interval between Mohakatino River and Waiau Stream was deposited in 1.16 ± 0.01 Ma between 9.67 + 0.07/-0.05 and 8.52 + 0.06/-0.07 Ma. Predicted ages for intra-Tongaporutuan bioevents (e.g. base Tukemokihi Coiling Zone) do not overlap their assigned ages, highlighting the importance of propagating uncertainties into bioevent absolute ages and opportunities for future improvements to the age model, namely using high-precision geochronology to acquire ages for additional tuffs and improve precision of existing ages. (author)