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P M Black - One of the best experts on this subject based on the ideXlab platform.
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comparison of skid resistance performance between Greywackes and melter slag aggregates in new zealand
International Safer Roads Conference 2nd 2008 Cheltenham United Kingdom, 2008Co-Authors: D J Wilson, P M BlackAbstract:This paper discusses and compares the skid resistance performance of three natural Greywacke aggregates and an artificial melter slag aggregate used in New Zealand as road surfacing chip. The comparison includes surface friction test results of the accelerated polishing of laboratory prepared samples and the coefficient of friction as measured by the dynamic friction tester. Furthermore the paper shows what occurs to the microtexture of the aggregate surface by the use of scanning electron microscope (SEM) photographs and how the performance in terms of 'polishing' and measured skid resistance relates to the aggregate mineralogy, grain size and, in the case of Greywackes, to their degree of lithification and diagenesis. The paper concludes that the polished stone value (PSV) test cannot be reliably used as a predictor of an aggregates performance. However, the newly developed accelerated polishing method and subsequent surface friction testing developed at the University of Auckland, when combined with an understanding of the aggregates microscopic properties and the geological forming processes of the aggregate, can explain long term skid resistance performance.
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very low grade metamorphism in basement Greywacke terranes of the northern and central north island new zealand
Gondwana Research, 2002Co-Authors: S Woldemichael, P M BlackAbstract:Abstract Metamorphism in the late Permian to early Cretaceous North Island basement Greywackes has been investigated using petrography and clay mineral crystallinity. Several terranes are represented in the North Island Greywackes and the study area includes Murihiku, Manaia Hill, Bay of Islands and Omahuta terranes and the Melange Zone. Very low-grade metamorphic events in the Greywackes have produced mineral assemblages of zeolite to pumpellyite-actinolite Greywacke facies. Zeolite facies Greywackes are characterized by the assemblage Zeo (Lmt, Anl, Hul)+Qtz±Ab±Cal± Chl±I±I/S* observed in the entire Murihiku terrane and in the eastern part of the Bay of Islands terrane and the Melange Zone. The entire Manaia Hill, most of the Bay of Islands, the eastern area of the Omahuta terranes and the central part of the Melange Zone are at prehnite-pumpellyite facies with mineral assemblages of Prh+Qtz+Chl+Pmp+Ab+± Ill±Cal±Lmt. Pumpellyite-actinolite facies with the mineral assemblage of Pmp±Act+Qtz+Ab+Chl±Ep±Ill±Cal±Chl occurs in the western part of the Melange Zone and the Omahuta terrane. Illite (IC) and chlorite (ChC) crystallinity values of Greywackes are very similar and range from diagenetic zone to anchizone. Metamorphic conditions indicated by the IC and ChC and mineral facies are in excellent agreement and correlate as follows: crystallinity diagenetic-zone with the zeolite mineral facies, crystallinity lower anchizone with prehnite-pumpellyite mineral facies and crystallinity upper anchizone with pumpellyite-actinolite mineral facies. The general increase in the metamorphic grade from east to west, except in Murihiku terrane, is compatible with the sequence of accretion expected in a subduction environment.
Trevor Ireland - One of the best experts on this subject based on the ideXlab platform.
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crustal evolution of new zealand evidence from age distributions of detrital zircons in western province paragneisses and torlesse Greywacke
Geochimica et Cosmochimica Acta, 1992Co-Authors: Trevor IrelandAbstract:Abstract Individual zircon grains from three Western Province paragneisses and a sample of Torlesse Greywacke have been dated by ion microprobe mass spectrometry. The paragneisses have zircon age distributions that indicate maximum ages of deposition of Ordovician to Devonian with Cretaceous metamorphism. Archean zircons as old as 3400 Ma have been identifiedand distinct components are present at 1700 Ma, 1050 Maand 500–600 Ma. These characteristics are identical to zircon age distributions in Ordovician sediments from eastern Australia suggesting a common provenance. The Torlesse Greywacke has a Permian-Triassic sedimentary age and the zircons are predominantly 260 Ma old. Rounded detrital zircons in the Greywacke range in age from 340 to 1240 Ma with peaks in the age distribution at 500–600 Ma and 1100 Ma, similar to that seen from the Western Province paragneisses. However, this does not necessarily require a western origin for Torlesse sediments. Further work is required to establish whether the zircon age distribution in the Western Province paragneisses and eastern Australian sediments is a regional characteristic of the Pacific margin of Gondwana.
Prosun Bhattacharya - One of the best experts on this subject based on the ideXlab platform.
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petrology and geochemistry of Greywackes from the aravalli supergroup rajasthan india and the tectonic evolution of a proterozoic sedimentary basin
Precambrian Research, 1994Co-Authors: D M Banerjee, Prosun BhattacharyaAbstract:The Proterozoic Aravalli Supergroup in south-central Rajasthan, western India is predominantly composed of coarse, low-grade meta-arenites, carbonates, Greywackes, interbedded fine-grained silty arenites and metapelites resting on an Archaean basement complex of gneisses, schists and high-grade metasediments. We have differentiated four lithofacies (A, B, C and D) within the Greywacke suite, each with characteristic QFL composition, grain size and major, trace and rare earth element concentrations. Tectonic setting for each facies type could only be discriminated using QmFLt plots. Greywackes of facies A and D were derived from a recycled orogen and facies B was derived from arc-related andesitic source rocks. A continental block provenance is indicated for the silty arenites of facies C. This petrofacies-based interpretation shows good agreement with environmental reconstructions based on lithofacies and sedimentary structure analyses. The only exception is facies B, whose andesitic parentage as deduced from petrofacies analysis could not be demonstrated at its outcrop. These provenance discriminations were tested through tectonic setting interpretations based on major, trace and rare earth elements. The geochemical data broadly confirmed the tectonic interpretations made on the basis of the petrological attributes. Use of these laboratory-based methods in conjunction with field measurements of primary sedimentary structures allow us to discriminate provenance and tectonic setting fairly precisely. A Proterozoic plate model with subduction to the west has been proposed to explain the sedimentological variation in the Aravalli Supergroup.
Dave Craw - One of the best experts on this subject based on the ideXlab platform.
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stratigraphy and provenance of pliocene Greywacke bearing conglomerate cardrona valley otago new zealand
New Zealand Journal of Geology and Geophysics, 2003Co-Authors: M Mcdonnell, Dave CrawAbstract:Abstract A synclinal sedimentary basin in the Cardrona valley, Otago, New Zealand, has formed along the Nevis‐Cardrona Fault Zone, a major fault zone associated with late Cenozoic Alpine Fault related deformation. The sedimentary basin records a conformable transition from Miocene low‐energy fluviolacustrine sedimentation to fluvial gravel deposits (>300 m thick) associated with late Miocene‐Pliocene initiation of mountain building in the region. The lower gravel unit, the Tuohys Breccia (new name), contains mainly subangular schist clasts, with subordinate quartz, derived from the uplifted schist basement adjacent to the sedimentary basin. This unit is conformably overlain by the Waiorau Conglomerate (new name), which contains up to 80% Greywacke clasts. There is no Greywacke basement in the Cardrona area, and these gravels must have been transported >60 km. The Greywacke clasts have a high quartz (c. 40%) and feldspar content (c. 40%) and low lithic content (c. 20%), typical of Torlesse Terrane, rather ...
N Mortimer - One of the best experts on this subject based on the ideXlab platform.
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early cretaceous Greywacke from colville knolls new zealand
New Zealand Journal of Geology and Geophysics, 2020Co-Authors: N Mortimer, C. J. Adams, I C WrightAbstract:ABSTRACTBlocks of Greywacke sandstone were dredged from the Colville Knolls, on the margin of the Zealandia continent, in 1989. Re-examination shows them to be quartz-poor feldspathic litharenites ...
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torlesse Greywacke and haast schist source for pliocene conglomerates near reefton new zealand
New Zealand Journal of Geology and Geophysics, 2001Co-Authors: N Mortimer, Rupert Sutherland, Simon NathanAbstract:Abstract Late Miocene‐Quaternary conglomerates in the Inangahua valley record provenance changes which can be related to tectonic activity in the northern South Island. Conglomerate clasts within the early Miocene Rotokohu Coal Measures comprise mainly metamorphosed quartzose Greywacke with subordinate granitoids, consistent with an essentially local clastic source from west of the Alpine Fault. In contrast, conglomerates of the late Pliocene Old Man Group (Larry Schist and Cronadun Conglomerates) are dominated by Rakaia Terrane (Older Torlesse) Greywacke and Haast Schist clasts from east of the Alpine Fault, which is c. 50 km southeast of the study area. A complete range of textural and metamorphic grades is present, confirming that oligoclase zone Alpine Schist was being exhumed during Pliocene time. The 50–70°‐dipping Pliocene beds are unconformably overlain by subhorizontally dipping late Quaternary gravels (Tophouse and Speargrass Formations), which, like the Miocene conglomerates, are composed of qu...
