2024 |
Yang B, Offler R, Fitzherbert JA, Folkes C, Dwyer R, Clark C, 'Basin provenance and its control on mineralisation within the Early Devonian Cobar Basin, western Lachlan Orogen, eastern Australia', Australian Journal of Earth Sciences, 71 211-230 (2024) [C1]
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2023 |
Doucet LS, Li Z-X, Brennan D, Offler R, Gamaleldien H, Ware B, et al., 'Precambrian History of the Pacific Mantle Domain: New Constraints from Woodsreef and Port Macquarie Serpentinized Spinel Harzburgites of the New England Orogen, Australia', JOURNAL OF PETROLOGY, 64 (2023) [C1]
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Nova |
2023 |
Maravelis AG, Offler R, Botziolis C, Pantopoulos G, Scott A, Landenberger B, Collins WJ, 'Provenance of a Late Permian retroarc foreland basin along the eastern Gondwanan margin: northern Sydney Basin, eastern Australia', GEOLOGICAL MAGAZINE, 160 1535-1555 (2023) [C1]
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Nova |
2021 |
Maravelis AG, Offler R, Pantopoulos G, Collins WJ, 'Provenance and tectonic setting of the Early Permian sedimentary succession in the southern edge of the Sydney Basin, eastern Australia', GEOLOGICAL JOURNAL, 56 2258-2276 (2021) [C1]
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Nova |
2021 |
Offler R, Boyd R, 'Source of detritus in subducted turbidites, tectonic mélange, port macquarie block, southern new england orogen, australia a geochemical perspective', Journal of Geology, 129 49-62 (2021) [C1]
A tectonic mélange containing blueschists and eclogites, Middle Ordovician mid-ocean ridge basalt, cherts, and clastic sediments occurs at Port Macquarie in the southern New Engla... [more]
A tectonic mélange containing blueschists and eclogites, Middle Ordovician mid-ocean ridge basalt, cherts, and clastic sediments occurs at Port Macquarie in the southern New England Orogen, Australia. The clastics are quartz-poor and are dominated by mafic volcanic and fragmented plagioclase clasts; felsic volcanic clasts are less common. They exhibit erosional bases, graded bedding, load structures, and lithologies ranging from laminated mudstones to pebbly sandstones. Based on these features, they are interpreted as turbidites. During subduction, these turbidites were deformed and metamorphosed under prehnite¿pumpellyite and lower greenschist facies conditions. Geo-chemically, they have a calc-alkaline, intra-oceanic arc signature; show no recycling; and have been derived from a provenance dominated by mafic volcanic rocks of basaltic-andesite composition. Further, chemical index of alteration (44¿69) and Index of Compositional Variability (0.8¿2.4) data reveal they show little weathering and are immature. The lack of weathering of rocks in a location where tropical climatic conditions existed is attributed to extreme erosion associated with a dynamic setting resulting in rapid transportation of the sediments to the fore arc basin and subsequently to the trench. As a consequence, little time was available for weathering to take place. The detritus in the turbidites is thought to have been derived from Late Ordovician volcanics in the Macquarie Arc and fore arc basin sequences of the Murrawong Formation. The cherts with which they are associated record both a continental and oceanic arc geochemical signature.
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Nova |
2021 |
Offler R, 'Geochemistry and provenance of lower Permian sedimentary rocks, Nambucca Block, southern New England Orogen', Australian Journal of Earth Sciences, 68 992-1004 (2021) [C1]
It is well documented that sediments record geochemical signatures that reflect the composition and tectonic setting of the rocks providing the detritus for them. This is true of ... [more]
It is well documented that sediments record geochemical signatures that reflect the composition and tectonic setting of the rocks providing the detritus for them. This is true of the turbidites in the Nambucca Block that record compositions that vary from basaltic to rhyodacitic but are dominantly andesitic to dacitic. They show chondrite and N-MORB patterns, characteristic of calc-alkaline, continental arc rocks, namely light REE (av. La/Yb) N = 6.3) and Th enrichment, Ti, Nb and Ta depletion, and substantial within plate components (Nb/Yb; 0.65¿5.16; x = 3.15). Rare occurrences of rocks with intra-oceanic island arc affinities and felsic volcanic rocks showing tectonic fabrics occur, indicating more distal sources contributed detritus. Most detritus in the turbidites has been derived from the calc-alkaline, continental rocks of the Keepit arc, some from the subduction¿accretion sequences of the Tablelands Complex. CIA [Al2O3/(Al2O3+Na2O + K2O + CaO)×100] values (48¿83; x = 68) indicate that erosion of these arc sequences occurred during glacial, temperate and humid conditions at different times. Further, index of chemical variability values (0.3¿1.85; x = 0.85) reveal a compositional maturity and a high percentage of clays in the source rocks suggesting a passive tectonic setting in which minimal uplift and extensive weathering took place.KEY POINTS Metasediments in the Nambucca Block record geochemical signatures typical of calc-alkaline, continental, arc rocks. Detritus in metasediments was derived from the Keepit arc and Tablelands Complex, southern New England Orogen. Source rocks were subjected to glacial, temperate and humid conditions at different times.
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Nova |
2019 |
Offler R, Zwingmann H, Foden J, Sutherland FL, Graham IT, 'Age and composition of dykes emplaced before and during the opening of the Tasman Sea-source implications', AUSTRALIAN JOURNAL OF EARTH SCIENCES, 66 1129-1144 (2019) [C1]
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Nova |
2018 |
Offler R, Huang HQ, 'Middle-Late Devonian nascent back arc formation, southern New England Orogen, NSW, Australia', Gondwana Research, 63 250-267 (2018) [C1]
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Nova |
2018 |
Offler R, Lennox P, Yan J, Pratt W, 'Comment on "Orocline-Driven Transtensional Basins: Insights From the Lower Permian Manning Basin (Eastern Australia)" by White et al. (2016)', TECTONICS, 37 391-395 (2018)
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2017 |
Yan J, Lennox PG, Offler R, 'The structural evolution of the Northern Hastings Block and southern Nambucca Block, southern New England Orogen, eastern Australia', Australian Journal of Earth Sciences, 64 871-887 (2017) [C1]
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Nova |
2016 |
Offler R, Fergusson CL, 'Proto-Pacific-margin source for the Ordovician turbidite submarine fan, Lachlan Orogen, southeast Australia: Geochemical constraints', Sedimentary Geology, 334 53-65 (2016) [C1]
The Early Palaeozoic proto-Pacific Pacific margin of Gondwana was characterised by a huge turbidite submarine fan with abundant clastic detritus derived from unknown sources withi... [more]
The Early Palaeozoic proto-Pacific Pacific margin of Gondwana was characterised by a huge turbidite submarine fan with abundant clastic detritus derived from unknown sources within Gondwana. These deposits are widespread in the Lachlan Orogen of southeast Australia and include the Ordovician Adaminaby Group. Here we show that the mudstones and sandstones of the Adaminaby Group have chemical compositions that indicate the detritus in them was derived from a felsic, continental source similar in composition to Post Archean Australian Shales (PAAS). Chondrite normalised REE patterns showing LREE enrichment, flat PAAS normalised patterns and elemental ratios La/Sc, Cr/Th, Cr/V, Th/Sc and Th/U, have been used to support this interpretation. The dominance of quartz, and to a lesser degree plagioclase and biotite in the sandstones, suggests that the source was mainly granodioritic to tonalitic in composition. Th/Yb and Ta/Yb ratios indicate that the source was probably calc-alkaline, continental and shoshonitic. In addition, the presence of detrital muscovite, low-grade metamorphic and felsic volcanic clasts, demonstrates that a low-grade metamorphic terrane and volcanic arc contributed to the detritus observed in the samples. The presence of well-rounded zircons and tourmalines, very high Zr contents, high Zr/Sc and higher Cr/V ratios in some samples particularly in the Shoalhaven River area, indicate that some of the detritus was recycled.SiO2 versus (Al2O3 + K2O + Na2O) plots suggest the source areas experienced conditions varying from humid/semi-humid to semi-arid. Textural features and weathering trends of samples from all locations follow a curved pathway on Al2O3 - (CaO* + Na2O) - K2O (ACNK) diagrams, and indicate that the clays formed from weathering had been K-metasomatised prior to penetrative deformation. Chemical indices of alteration (CIA) reveal that even the freshest sandstones are altered and others are moderately to strongly altered. Discrimination diagrams involving major, trace and REE strongly support a collisional/continental volcanic arc setting that was substantially eroded to produce the plutonic detritus observed in the sandstones. The collisional setting accords with that proposed previously by other authors who suggested that it developed during the Delamerian Orogeny, resulting in the uplifted source areas providing detritus that inundated the backarc and forearc sites of the Macquarie Arc. Some of the detritus, however, may have been derived from a continental arc that existed in the late Cambrian along the margin of the Ross Orogen. Based on palaeocurrent analyses in previous studies and shoshonitic signature of the detritus, it is proposed that the Cambrian volcanics along the eastern active margin of Gondwana provided much of the detritus in the Adaminaby Group. Zircons with the Grenvillian signature suggest that some detritus were also derived from the Ross Orogen.
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Nova |
2016 |
Yan J, Lennox PG, Offler R, 'History of faulting in the Northern Hastings Block, southern New England Orogen', Australian Journal of Earth Sciences, 63 821-841 (2016) [C1]
Brittle failure is common in the Devonian to Permian rocks in the Northern Hastings Block (NHB) and is manifested by faults of different orientation and kinematic histories, but t... [more]
Brittle failure is common in the Devonian to Permian rocks in the Northern Hastings Block (NHB) and is manifested by faults of different orientation and kinematic histories, but the timing of fault movement is not well defined. In this study, faults in the NHB were analysed with the map pattern of cross-cutting faults used to estimate the relative time of movement and relationship to other faults. We defined five episodes of faulting or fault reactivation that affected the NHB. The Yarras Fault System on the southwestern side of the NHB and the Parrabel Fault and related faults on the eastern side of the NHB are the two major fault systems responsible for transporting and rotating the NHB in the late Carboniferous. Faults on the eastern, northeastern and northern part of Parrabel Dome started and stopped moving after emplacement of the Hastings Block and before the intrusion of the Werrikimbe Triassic granitoids. We suggested that the movement on the major bounding faults is related to the accommodation of the NHB to the folding and cleavage development in the adjoining Nambucca Block, and is associated with the earliest part of the Hunter¿Bowen Orogeny. Limited dextral movement on the extensions of the Taylors Arm Fault System caused minor displacements in the northeastern part of the NHB during the Late Triassic. Some small faults cut the Triassic granitoids or Triassic Lorne Basin sediments indicating tectonic activity continued post-Triassic.
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Nova |
2015 |
Stokes N, Fergusson CL, Offler R, 'Backarc basin and ocean island basalts in the Narooma Accretionary Complex, Australia: setting, geochemistry and tectonics', Australian Journal of Earth Sciences, 62 37-53 (2015) [C1]
The Cambrian¿Ordovician Wagonga Group contains basalts at Melville Point and Barlings Beach, 20¿km south of Batemans Bay, New South Wales. At Melville Point, the succession has ba... [more]
The Cambrian¿Ordovician Wagonga Group contains basalts at Melville Point and Barlings Beach, 20¿km south of Batemans Bay, New South Wales. At Melville Point, the succession has basal altered basalts overlain by chert and interbedded siliceous mudstone of the Wagonga Group, in turn overlain by turbidites and chert of the Adaminaby Group with a latest Cambrian to earliest Ordovician age. By contrast, at Barlings Beach, basalt is associated with highly disrupted chert (tectonic mélange), various slivers of mudstone and turbidites, and turbidites of the Adaminaby Group. Immobile elements in the basalts show consistent patterns that allow the magmatic affinity and tectonic setting to be determined in spite of pervasive hydrothermal alteration and subsequent lower greenschist facies metamorphism that accompanied strong folding and multiple foliation development. The Melville Point basalts show Ti/V ratios transitional between arc and MORB and therefore may have formed in either a forearc or backarc basin setting. However, these rocks have higher Ti/V ratios, LREE, Th and Nb than found in forearc basalts and are therefore considered to have formed in a backarc basin setting. In contrast to Melville Point, most basalts at Barlings Beach have a geochemical signature distinctive of ocean island settings like those reported from elsewhere in the Wagonga Group. We believe these rocks developed in a Cambrian backarc basin setting. In the Early to Middle Ordovician, much of the ocean basin was inundated by quartzose turbidites followed by basin destruction with accretion/underplating at a Late Ordovician¿early Silurian Benambran subduction zone and formation of the Narooma Accretionary Complex.
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Nova |
2015 |
Offler R, Lennox PG, Phillips G, Yan J, 'Comment on: "Does the Manning Orocline exist? New structural evidence from the inner hinge of the Manning Orocline (eastern Australia)" by Li and Rosenbaum (2013). Gondwana Research', Gondwana Research, 27 1686-1688 (2015) [C3]
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Nova |
2015 |
Phillips G, Offler R, Rubatto D, Phillips D, 'High-pressure metamorphism in the southern New England Orogen: Implications for long-lived accretionary orogenesis in eastern Australia', Tectonics, 34 1979-2010 (2015) [C1]
New geochemical, metamorphic, and isotopic data are presented from high-pressure metamorphic rocks in the southern New England Orogen (eastern Australia). Conventional and optimal... [more]
New geochemical, metamorphic, and isotopic data are presented from high-pressure metamorphic rocks in the southern New England Orogen (eastern Australia). Conventional and optimal thermobarometry are augmented by U-Pb zircon and 40Ar/39Ar phengite dating to define pressure-temperature-time (P-T-t) histories for the rocks. The P-T-t histories are compared with competing geodynamic models for the Tasmanides, which can be summarized as (i) a retreating orogen model, the Tasmanides formed above a continuous, west dipping, and eastward retreating subduction zone, and (ii) a punctuated orogen model, the Tasmanides formed by several arc accretion, subduction flip, and/or transference events. Whereas both scenarios are potentially supported by the new data, an overlap between the timing of metamorphic recrystallization and key stages of Tasmanides evolution favors a relationship between a single, long-lived subduction zone and the formation, exhumation, and exposure of the high-pressure rocks. By comparison with the retreating orogen model, the following links with the P-T-t histories emerge: (i) exhumation and underplating of oceanic eclogite during the Delamerian Orogeny, (ii) recrystallization of underplated and exhuming high-pressure rocks at amphibolite facies conditions coeval with a period of rollback, and (iii) selective recrystallization of high-pressure rocks at blueschist facies conditions, reflecting metamorphism in a cooled subduction zone. The retreating orogen model can also account for the anomalous location of the Cambrian-Ordovician high-pressure rocks in the Devonian-Carboniferous New England Orogen, where sequential rollback cycles detached and translated parts of the leading edge of the overriding plate to the next, younger orogenic cycle.
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Nova |
2014 |
Och DJ, Offler R, Zwingmann H, 'Constraining timing of brittle deformation and fault gouge formation in the Sydney Basin', Australian Journal of Earth Sciences, 61 337-350 (2014) [C1]
Structural and K-Ar dating studies of gouge in N-S, NNE and E-W-trending faults in four locations in the Sydney-Hunter region are reported. The fault zones are manifest as joint s... [more]
Structural and K-Ar dating studies of gouge in N-S, NNE and E-W-trending faults in four locations in the Sydney-Hunter region are reported. The fault zones are manifest as joint swarms and highly brecciated zones containing gouge with authigenic illite produced as a result of fluid infiltration. Strike-slip movement accompanied by minor dip-slip, normal movement occurred on the NNE faults, with dip slip on N-S and E-W-trending faults. In this study, gouge from a NE-trending, steep, SE-dipping fault showing dip-slip movement at Cut 10, on the Hunter Expressway and from an E-W-trending, steep south-dipping, normal fault at the Westside Open Cut, Lake Macquarie have been analysed. K-Ar dating of illite and illite-smectite in fractions extracted from fault gouges in areas unaffected by a thermal overprint reveals ages varying from 166 to 119 Ma for the <2 µm and finer fractions, and a mean age of ca 120 Ma for the <0.4 µm fraction. In the Sydney area and the Westside Open Cut coal mine, Lake Macquarie, the ages obtained from similar size fractions both for the gouge and for the host rocks are younger (134-76 Ma; av. <0.4 µm = 111 Ma). The data indicate influence of a thermal overprint associated with subsurface magmas emplaced during the early stages of the rifting of eastern Gondwana during the early Cretaceous. © 2014 © 2014 Geological Society of Australia.
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Nova |
2013 |
Lennox PG, Offler R, Yan J, 'Discussion of Glen R.A. and Roberts J. 2012: Formation of Oroclines in the New England Orogen, Eastern Australia. In: Oroclines (Eds.) Stephen Johnston and Gideon Rosenbaum, Journal of the Virtual Explorer, volume 43, paper 3.', Journal of the Virtual Explorer, 44 1-10 (2013) [C1]
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Nova |
2012 |
Prendergast EI, Offler R, 'Underplated seamount in the Narooma accretionary complex, NSW, Australia', Lithos, 154 224-234 (2012) [C1]
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Nova |
2012 |
Prendergast EI, Offler R, Zwingmann H, 'Adaminaby Group west of Batemans Bay: Deformation and metamorphism of the Narooma accretionary complex, NSW', Australian Journal of Earth Sciences, 29 1049-1066 (2012) [C1]
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Nova |
2011 |
Offler R, Phillips G, Fergusson CL, Green TJ, 'Tectonic implications of early paleozoic metamorphism in the Anakie Inlier, Central Queensland, Australia', Journal of Geology, 119 467-485 (2011) [C1]
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Nova |
2011 |
Prendergast EI, Offler R, Phillips D, Zwingmann H, '40Ar/39Ar and K-Ar ages: Early paleozoic metamorphism and deformation in the Narooma accretionary complex, NSW', Australian Journal of Earth Sciences, 58 21-32 (2011) [C1]
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2011 |
Phillips G, Offler R, 'Contrasting modes of eclogite and blueschist exhumation in a retreating subduction system: The Tasmanides, Australia', Gondwana Research, 19 800-811 (2011) [C1]
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Nova |
2011 |
Offler R, Murray C, 'Devonian volcanics in the New England Orogen: Tectonic setting and polarity', Gondwana Research, 19 706-715 (2011) [C1]
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Nova |
2010 |
Phillips G, Hand M, Offler R, 'P-T-X controls on phase stability and composition in LTMP metabasite rocks - A thermodynamic evaluation', Journal of Metamorphic Geology, 28 459-476 (2010) [C1]
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Nova |
2009 |
Turner S, Haines P, Foster D, Powell R, Sandiford M, Offler R, 'Did the Delamerian Orogeny start in the Neoproterozoic?', Journal of Geology, 117 575-583 (2009) [C1]
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Nova |
2009 |
Fergusson CL, Offler R, Green TJ, 'Late Neoproterozoic passive margin of East Gondwana: Geochemical constraints from the Anakie Inlier, central Queensland, Australia', Precambrian Research, 168 301-312 (2009) [C1]
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Nova |
2009 |
Lennox PG, Offler R, 'Kinematic history of serpentinites in the faulted margins of the Hastings Block, New England Orogen, eastern Australia', Australian Journal of Earth Sciences, 56 621-638 (2009) [C1]
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Nova |
2009 |
Och DJ, Offler R, Zwingmann H, Braybrooke J, Graham IT, 'Timing of brittle faulting and thermal events, Sydney region: Association with the early stages of extension of East Gondwana', Australian Journal of Earth Sciences, 56 873-887 (2009) [C1]
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Nova |
2009 |
Offler R, Och DJ, Phelan D, Zwingmann H, 'Mineralogy of gouge in north-northeast-striking faults, Sydney region, New South Wales', Australian Journal of Earth Sciences, 56 889-905 (2009) [C1]
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Nova |
2008 |
Phillips G, Hand M, Offler R, 'P-T-t-deformation framework of an accretionary prism, southern New England Orogen, eastern Australia: Implications for blueschist exhumation and metamorphic switching', Tectonics, 27 1-15 (2008) [C1]
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Nova |
2008 |
Offler R, Foster DA, 'Timing and development of oroclines in the southern New England Orogen, New South Wales', Australian Journal of Earth Sciences, 55 331-340 (2008) [C1]
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Nova |
2006 |
Offler R, Shaw S, 'Hornblende gabbro block in serpentinite Melange, Peel-Manning Fault System, new South Wales, Australia: Lu-Hf and U-Pb isotopic evidence for mantle-derived, Late Ordovician igneous activity', Journal of Geology, 114 211-230 (2006) [C1]
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2006 |
Roberts J, Offler R, Fanning M, 'Carboniferous to Lower Permian stratigraphy of the southern Tamworth Belt, southern New England Orogen, Australia: boundary sequences of the Werrie and Rouchel blocks', Australian Journal of Earth Sciences, 53 249-284 (2006) [C1]
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Nova |
2005 |
Sakai H, Kikawa E, Offler R, Zwingmann H, 'Paleomagnetic and K-Ar dating studies of Late Cretaceous basaltic dykes intruding Late Permian sediments of Newcastle Coal Measures, Newcastle, Australia - Relationship to the opening of the Tasman Sea', Polar Geoscience, 18 58-66 (2005) [C1] |
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Nova |
2004 |
Zwingmann H, Offler R, Wilson TC, Cox SF, 'K-Ar dating of fault gouge in the northern Sydney Basin, NSW, Australia-implications for the breakup of Gondwana', Journal of Structural Geology, 26 2285-2295 (2004) [C1]
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Nova |
2004 |
Roberts J, Offler R, Fanning M, 'Upper Carboniferous to Lower Permian volcanic successions of the Carroll-Nandewar region, Northern Tamworth Belt, Southern New England Orogen, Australia', Australian Journal of Earth Sciences, 51 205-232 (2004) [C1]
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Nova |
2004 |
Offler R, Glen RA, Hyodo H, Jiang Z, 'Subduction of arc basaltic andesite: implications for the tectonic history of the southern New England Fold Belt', Australian Journal of Earth Sciences, 51 819-830 (2004) [C1]
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Nova |
2004 |
Sano S, Offler R, Hyodo H, Watanabe T, 'Geochemistry and Chronology of Tectonic Blocks in Serpentinite Mélange of the Southern New England Fold Belt, NSW, Australia', Gondwana Research, 7 817-831 (2004) [C1]
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Nova |
2002 |
Offler R, Gamble J, 'Evolution of an intra-oceanic island arc during the late Silurian to late Devonian, New England fold belt', Australian Journal of Earth Sciences, 49 349-366 (2002) [C1]
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Nova |
2002 |
Johnston A, Offler R, Liu S, 'Structural fabric evidence for indentation tectonics in the Nambucca block, southern New England fold belt, New South Wales', Australian Journal of Earth Sciences, 49 407-421 (2002) [C1]
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Nova |
2001 |
Kramer WA, Weatherall GD, Offler R, 'Origin and correlation of tuffs in the Permian Newcastle and Wollombi coal measures, NSW, Australia, using chemical fingerprinting', International Journal of Coal Geology, 47 115-135 (2001) [C1]
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2000 |
Seccombe PK, Offler R, Ayshford S, 'Origin of the magnetite skarn at Tallawang, NSW: Preliminary sulfur isotope results', Centre for Isotope Studies - Research Report, 1995-2000, 1995-2000 56-58 (2000) [C1] |
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1998 |
Offler R, McKnight S, Morand V, 'Tectonothermal history of the western Lachlan Fold Belt, Australia: insights from white mica studies', Journal of Metamorphic Geology, 16 531-540 (1998) [C1]
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1998 |
Offler R, Miller JM, Gray DR, Forster DA, Bale RJ, 'Crystallinity and bo spacing of K-white micas in a paleozoic Accretionary Complex, Eastern Australia: Metamorphism, Palaeogeotherms, and Structural Style of an Underplated Sequence', The Journal of Geology, 106 495-509 (1998) [C1]
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1997 |
Offler R, O'Hanley DS, Lennox P, 'Tectonic significance of veins and associated structures, Woodsreef, NSW.', Australian Journal of Earth Sciences, 19 226-241 (1997) |
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1996 |
Jenkins RB, Offler R, 'Metamorphism and deformation of an Early Permian extensional basin sequence: The Manning Group, southern new England Orogen', AUSTRALIAN JOURNAL OF EARTH SCIENCES, 43 423-435 (1996)
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1995 |
Roberts J, Leitch EC, Lennox PG, Offler R, 'Devonian-Carboniferous stratigraphy of the southern Hastings Block, New England Orogen, eastern Australia', AUSTRALIAN JOURNAL OF EARTH SCIENCES, 42 609-633 (1995)
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1995 |
LANDENBERGER B, FARRELL TR, OFFLER R, COLLINS WJ, WHITFORD DJ, 'TECTONIC IMPLICATIONS OF RB-SR BIOTITE AGES FOR THE HILLGROVE PLUTONIC SUITE, NEW-ENGLAND FOLD BELT, NSW, AUSTRALIA', PRECAMBRIAN RESEARCH, 71 251-263 (1995)
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1993 |
DIRKS P, OFFLER R, COLLINS WJ, 'TIMING OF EMPLACEMENT AND DEFORMATION OF THE TIA GRANODIORITE, SOUTHERN NEW-ENGLAND FOLD BELT, NSW - IMPLICATIONS FOR THE METAMORPHIC HISTORY', AUSTRALIAN JOURNAL OF EARTH SCIENCES, 40 103-108 (1993)
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1992 |
Little TA, Holcombe RJ, Gibson GM, Offler R, Gans PB, McWilliams MO, 'Exhumation of late Paleozoic blueschists in Queensland, Australia, by extensional faulting', Geology, 20 231-234 (1992)
Blueschists in southeastern Queensland, Australia, record a Carboniferous history of subduction and metamorphism at >6 kbar. A later thermal overprint associated with intrusion... [more]
Blueschists in southeastern Queensland, Australia, record a Carboniferous history of subduction and metamorphism at >6 kbar. A later thermal overprint associated with intrusion of S type granitoids ca. 306 Ma and regional greenschist facies metamorphism accompanied formation of ductile fabrics in the lower plate of an oceanic-protolith metamorphic core complex. Late Carboniferous extensional deformation in this part of the New England orogen may have accompanied outstepping of the subduction trench, or rollback and steepening of the paleo-Pacific plate during development of a wide zone of asthenospheric upwelling and continental back-arc extension. -Authors
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1992 |
OHANLEY DS, OFFLER R, 'CHARACTERIZATION OF MULTIPLE SERPENTINIZATION, WOODSREEF, NEW-SOUTH-WALES', CANADIAN MINERALOGIST, 30 1113-1126 (1992)
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1992 |
LITTLE TA, HOLCOMBE RJ, GIBSON GM, OFFLER R, GANS PB, MCWILLIAMS MO, 'EXHUMATION OF LATE PALEOZOIC BLUESCHISTS IN QUEENSLAND, AUSTRALIA, BY EXTENSIONAL FAULTING', GEOLOGY, 20 231-234 (1992)
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1992 |
DIRKS P, HAND M, COLLINS WJ, OFFLER R, 'STRUCTURAL METAMORPHIC EVOLUTION OF THE TIA COMPLEX, NEW-ENGLAND FOLD BELT - THERMAL OVERPRINT OF AN ACCRETION SUBDUCTION COMPLEX IN A COMPRESSIONAL BACK-ARC SETTING', JOURNAL OF STRUCTURAL GEOLOGY, 14 669-688 (1992)
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1992 |
OFFLER R, WHITFORD DJ, 'WALL-ROCK ALTERATION AND METAMORPHISM OF A VOLCANIC-HOSTED MASSIVE SULFIDE DEPOSIT AT QUE RIVER - TASMANIA - PETROLOGY AND MINERALOGY', ECONOMIC GEOLOGY AND THE BULLETIN OF THE SOCIETY OF ECONOMIC GEOLOGISTS, 87 686-705 (1992)
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1990 |
Offler R, Whitford DJ, Andrew AS, Sun S-S, 'A stable isotope study of the alteration zone surrounding the Que River Cu-Pb-Zn deposits, Tasmania. Research Report (1989-1990), Centre for Isotope Studies.', Research Report, Centre for Isotope Studies., 65-67 (1990) |
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1989 |
FARRELL TR, OFFLER R, 'GREEN-SCHIST FACIES METAMORPHISM OF A RIFT BASIN SEQUENCE, BREADALBANE, NSW', AUSTRALIAN JOURNAL OF EARTH SCIENCES, 36 337-349 (1989)
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1987 |
BAJWAH ZU, SECCOMBE PK, OFFLER R, 'TRACE-ELEMENT DISTRIBUTION, CO-NI RATIOS AND GENESIS OF THE BIG CADIA IRON-COPPER DEPOSIT, NEW-SOUTH-WALES, AUSTRALIA', MINERALIUM DEPOSITA, 22 292-300 (1987)
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1987 |
Offler R, Hand M, Bale R, 'b
In the Southern New England Fold Belt, N.S.W., Australia, bo studies of K-white micas have shown that the Tamworth Belt and Tablelands Complex contain sequences with distinctive m... [more]
In the Southern New England Fold Belt, N.S.W., Australia, bo studies of K-white micas have shown that the Tamworth Belt and Tablelands Complex contain sequences with distinctive metamorphic imprints. The white micas in the forearc basin sediments of the Tamworth Belt record low pressure conditions, whilst those in the accretionary complex sequences of the Tablelands Complex show an intermediate pressure character. The results are in accord with the plate tectonic models proposed for the Southern New England Fold Belt. Illite crystallinity analyses have revealed that rocks of diagenetic to lower anchimetamorphic grade are developed in the forearc succession and diagenetic to epimetamorphic grade in the accretionary complex, with grade increasing progressively from south to north. They also indicate that the Peel Fault System is not a major zone of thrusting. -Authors
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1985 |
Pemberton JW, Offler R, 'Significance of clinopyroxene compositions from the Cudgegong volcanics and Toolamanang volcanics; Cudgegong-Mudgee district, NSW, Australia.', Mineralogical Magazine, 49 591-599 (1985)
Clinopyroxenes as phenocrysts and in the groundmass of these altered basalts and basaltic andesites are considered to have crystallized at moderate (5-6 kbar) and falling P at T =... [more]
Clinopyroxenes as phenocrysts and in the groundmass of these altered basalts and basaltic andesites are considered to have crystallized at moderate (5-6 kbar) and falling P at T = or >900o-1000oC. Probe analyses show that they have a restricted compositional range and minor Fe enrichment from core to rim. It is suggested that they crystallized under hydrous conditions, with rising fO2 resulting in a Fe-Ti oxide appearing as a primary phase. -R.A.H.
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1985 |
Aguirre L, Offler R, 'Burial metamorphism in the western Peruvian trough: its relation to Andean magmatism and tectonics.', Magmatism at a Plate Edge: the Peruvian Andes, 59-71 (1985)
The Mesozoic-Cainozoic volcanic rocks of the Andes exhibit spilite-keratophyre alteration due to a combination of burial and hydrothermal metamorphism rather than contact metamorp... [more]
The Mesozoic-Cainozoic volcanic rocks of the Andes exhibit spilite-keratophyre alteration due to a combination of burial and hydrothermal metamorphism rather than contact metamorphism. Highest-grade assemblages occur in the basal parts of volcanic-deposition cycles formed by coupled subsidence and subduction. Metamorphic mineralogy for Peruvian volcanics is tabulated and 55 probe analyses are presented. The highest intensity of burial metamorphism in the Casma group reflects high geothermal gradients during aborted formation of a marginal basin. Comparison is made with central Chile and Patagonia, where metamorphism is characterized by lower geothermal gradients and mantle diapirism, respectively.-R.J.P.
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1985 |
OFFLER R, PRENDERGAST E, 'SIGNIFICANCE OF ILLITE CRYSTALLINITY AND B0 VALUES OF K-WHITE MICA IN LOW-GRADE METAMORPHIC ROCKS, NORTH HILL END SYNCLINORIUM, NEW-SOUTH-WALES, AUSTRALIA', MINERALOGICAL MAGAZINE, 49 357-364 (1985)
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1985 |
PEMBERTON JW, OFFLER R, 'SIGNIFICANCE OF CLINOPYROXENE COMPOSITIONS FROM THE CUDGEGONG VOLCANICS AND TOOLAMANANG VOLCANICS - CUDGEGONG-MUDGEE DISTRICT, NSW, AUSTRALIA', MINERALOGICAL MAGAZINE, 49 591-599 (1985)
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1985 |
Offler R, Prendergast E, 'Significance of illite crystallinity and b
For 80 slates and phyllites of late Silurian-early Carboniferous age in this area in the NE portion of the Lachlan fold belt, W of Sydney, illite crystallinity values vary from 0.... [more]
For 80 slates and phyllites of late Silurian-early Carboniferous age in this area in the NE portion of the Lachlan fold belt, W of Sydney, illite crystallinity values vary from 0.40 DELTA o 2theta (CuKalpha ) on the Molong anticlinorium to 0.12 DELTA o 2theta within the axis of the synclinorium, suggesting anchizonal to epizonal metamorphic conditions. This is in agreement with previous observations of a change from prehnite-pumpellyite facies (in the anticlinoria adjacent to the synclinorium) to middle greenschist facies in the axis (M.A. 69-2599). The mean b value from the pelitic rocks is 9.017 A, in close agreement with that for the adjacent Capertree anticlinorium. Statistical tests indicate two b populations in the Hill End synclinorium (9.010 and 9.022 A) with the lower values concentrated in the S portion of the structure; the higher geothermal gradient indicated by the lower b values is attributed to the presence of granitic intrusions at shallower depths than elsewhere in the synclinorium.-R.A.H.
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1984 |
Seccombe PK, Lau JL, Lea JF, Offler R, 'Geology and ore genesis of silver-lead-zinc-copper sulphide deposits, Sunny Corner, NSW.', Proceedings of the Australasian Institute of Mining & Metallurgy, 289 51-57 (1984)
The stratiform and vein-type pyritic Ag-Pb-Zn-Cu sulphide deposits of Sunny Corner, NSW, are hosted by acid volcanic and clastic sedimentary rocks of Middle Silurian to early Devo... [more]
The stratiform and vein-type pyritic Ag-Pb-Zn-Cu sulphide deposits of Sunny Corner, NSW, are hosted by acid volcanic and clastic sedimentary rocks of Middle Silurian to early Devonian age. The rocks have been subjected to low-grade regional metamorphism (prehnite-pumpellyite facies) and three phases of folding and four faulting events are recognized. Pyrite is intensely fractured, indicating brittle deformation. Chalcopyrite and galena exhibit deformation twins and slip planes indicating ductile deformation; sphalerite and chalcopyrite show straight and curved grain boundaries and dihedral angles of 120o as evidence of annealing recrystallization. Sulphur isotope ratios for 22 samples from five deposits range from 1.7 to 10.7per mille and average 7.4per mille. Sulphur isotope data are similar to those from other stratiform sulphide deposits in acid volcanic rocks of late Silurian age in the E Lachlan Fold Belt, especially Woodlawn and Captains Flat, and together with other features of the mineralization, suggest a volcanic exhalative origin for the Sunny Corner deposits.-H.K.H.
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1984 |
OFFLER R, 'SUBCALCIC, FE-RICH AMPHIBOLES IN META-DOLERITES, GLENROCK-STATION, NSW, AUSTRALIA', MINERALOGICAL MAGAZINE, 48 47-52 (1984)
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1984 |
Offler R, 'Subcalcic, Fe-rich amphiboles in meta-dolerites, Glenrock Station, NSW, Australia.', Mineralogical Magazine, 48 47-52 (1984)
Sub-greenschist-facies metamorphism has produced unusual Fe-rich, actinolitic amphiboles in metadolerites in this area approx 300 km N of Sydney. Microprobe analyses show edenite,... [more]
Sub-greenschist-facies metamorphism has produced unusual Fe-rich, actinolitic amphiboles in metadolerites in this area approx 300 km N of Sydney. Microprobe analyses show edenite, riebeckite, ferritschermakite and Ti-tschermakite coupled substitutions. Their high Fe content is attributed to high aFe2+ and aFe3+ in the fluid phase produced during the breakdown of clinopyroxene, hornblende, magnetite and ilmenite; the high aFe2+ led to Fe2+ occupying the B site, resulting in production of sub-calcic amphiboles.-R.A.H.
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1984 |
OFFLER R, AGUIRRE L, 'MINERAL CHEMISTRY OF LOW-GRADE METAMORPHIC ROCKS, WESTERN ANDES, PERU', NEUES JAHRBUCH FUR MINERALOGIE-ABHANDLUNGEN, 150 229-246 (1984)
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1982 |
OFFLER R, 'GEOCHEMISTRY AND TECTONIC SETTING OF IGNEOUS ROCKS IN THE GLENROCK STATION AREA, NSW', JOURNAL OF THE GEOLOGICAL SOCIETY OF AUSTRALIA, 29 443-455 (1982)
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1981 |
OFFLER R, BAKER CK, GAMBLE J, 'PUMPELLYITES IN 2 LOW-GRADE METAMORPHIC TERRANES NORTH OF NEWCASTLE, NEW-SOUTH-WALES AUSTRALIA', CONTRIBUTIONS TO MINERALOGY AND PETROLOGY, 76 171-176 (1981)
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1981 |
AGUIRRE L, LEVI B, OFFLER R, 'LOW-GRADE BURIAL METAMORPHISM IN THE ANDES', JOURNAL OF THE GEOLOGICAL SOCIETY, 138 633-633 (1981) |
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1980 |
OFFLER R, AGUIRRE L, LEVI B, CHILD S, 'BURIAL METAMORPHISM IN ROCKS OF THE WESTERN ANDES OF PERU', LITHOS, 13 31-42 (1980)
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1979 |
OFFLER R, 'PYROXENES IN ALTERED VOLCANIC-ROCKS, GLENROCK-STATION, NSW, AUSTRALIA', MINERALOGICAL MAGAZINE, 43 497-503 (1979)
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1978 |
AGUIRRE L, LEVI B, OFFLER R, 'UNCONFORMITIES AS MINERALOGICAL BREAKS IN BURIAL METAMORPHISM OF ANDES', CONTRIBUTIONS TO MINERALOGY AND PETROLOGY, 66 361-366 (1978)
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1976 |
Offler R, Diessel C F K, 'The aplication of reflectance determinations on coalified and graphitised plant fragments to metamorphic studies', Journal of the Geological Society of South Australia, 23 293-297 (1976) |
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1976 |
Offler R, Diessel CFK, 'The application of reflectance determinations on coalified and graphitized plant fragments to metamorphic studies', Journal of the Geological Society of Australia, 23 293-297 (1976)
In many sedimentary rocks, small quantities of plant fragments (phytoclasts) are present. During prograde metamorphism, they undergo coalification and graphitiza-tion concomitant ... [more]
In many sedimentary rocks, small quantities of plant fragments (phytoclasts) are present. During prograde metamorphism, they undergo coalification and graphitiza-tion concomitant with the recrystallization of the inorganic detritus. The degree of coalification, or rank, can be quantified by measuring the reflectance of the phytoclasts. Measurement of this optical parameter has been applied mainly to rank-variation analyses in sedimentary basins and, to a lesser degree, to oil and gas exploration, stratigraphical and structural problems, and to contact and burial metamorphic rocks as an indicator of rank. In this paper, the potential of reflectance studies of phytoclasts in metamorphic rocks, is further developed. It is shown that phytoclast reflectivity is a more sensitive indicator of thermal perturbations than are silicate minerals, and that it is a useful indicator of grade in areas where index minerals are not developed. Furthermore, examples are given showing that isorank lines delineated from reflectance data reveal, on a regional scale, a metamorphic imprint similar to that of the silicate assemblages, and that metamorphic variables other than pressure and temperature may be involved in metamorphic reactions. © 1976 Taylor & Francis Group, LLC.
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1975 |
Offler R, Offler R, Diessel CFK, 'Change in physical properties of coalified and graphitised phytoclasts with grade of metamorphism', N. Jb. Miner. Mh., 1 11-26 (1975) |
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1973 |
DIESSEL CFK, OFFLER R, 'RELATIONSHIP BETWEEN GRAPHITE RANK AND METAMORPHIC GRADE IN MOUNT-LOFTY-RANGES, SOUTH-AUSTRALIA', SEARCH, 4 497-499 (1973)
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1973 |
Offler R, Offler R, 'The relationship between graphite rank and metamorphic grade in the Mt. Lofty Ranges, S. A.', Search, 4 497-499 (1973) |
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1968 |
FLEMING PD, OFFLER R, 'PRE-TECTONIC METAMORPHIC CRYSTALLIZATION IN MT LOFTY RANGES SOUTH AUSTRALIA', GEOLOGICAL MAGAZINE, 105 356-& (1968)
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1968 |
Offler R, Fleming P, 'A Synthesis of Folding and Metamorphism in the Mt Lofty Ranges, South Australia. (1968) [C1]
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1963 |
Offler R, Offler R, 'Structural geology of the Strathalbyn Anticline, South Australia', Transactions of the Royal Society of South Australia, 87 199-208 (1963) |
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