Journal articles on the topic 'Metamorphic rocks New Caledonia'
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Dallmeyer, R. David, and R. Damian Nance. "40Ar/39Ar whole-rock phyllite ages from late Precambrian rocks of the Avalon composite terrane, New Brunswick: evidence of Silurian–Devonian thermal rejuvenation." Canadian Journal of Earth Sciences 31, no. 5 (May 1, 1994): 818–24. http://dx.doi.org/10.1139/e94-075.
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Several variably deformed and metamorphosed, late Precambrian volcanic–sedimentary successions have been recognized within the Avalon composite terrane exposed in the Caledonian Highlands of southern New Brunswick. Whole-rock samples of metasedimentary phyllite and phyllitic metatuff from the oldest (ca. 600–635 Ma) Avalonian succession display similar, internally discordant 40Ar/39Ar age and apparent K/Ca spectra. Intermediate-temperature gas fractions were experimentally evolved solely from very fine grained, cleavage-aligned white micas. These yield apparent ages between ca. 430 and 410 Ma, and are interpreted to closely date a static Late Silurian – Early Devonian thermal rejuvenation.Evidence for a Silurian – Devonian thermal event has not been previously documented in Avalonian rocks of the Caledonian Highlands (Caledonia assemblage). However, a thermal overprint of similar age (ca. 400 Ma) is recorded by metamorphic muscovite in high-grade gneisses and platformal metasedimentary rocks (Brookville assemblage), which are in tectonic contact with the low-grade Caledonia assemblage. These potentially correlative thermal overprints may provide minimum age constraints on the juxtaposition of these contrasting tectono-stratigraphic assemblages, which are likely to have been palinspastically separate tectonic elements during the earliest Paleozoic.
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Maurizot, P., B. Sevin, S. Lesimple, J. Collot, J. Jeanpert, L. Bailly, B. Robineau, M. Patriat, S. Etienne, and C. Monnin. "Chapter 9 Mineral resources and prospectivity of non-ultramafic rocks of New Caledonia." Geological Society, London, Memoirs 51, no. 1 (2020): 215–45. http://dx.doi.org/10.1144/m51-2016-9.
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AbstractThe mineral resources of the non-ultramafic rocks of New Caledonia and its Exclusive Economic Zone can be classified according to their host rocks. The metallic mineral resources are essentially associated with volcanic and magmatic activity. Non-economic volcanogenic massive sulfide deposits with Cu and Au are located in the Late Carboniferous Koh Ophiolite and in the Late Cretaceous Poya Terrane. Base metals, Au and Ag of the sedimentary–exhalative type are present in the metamorphic Diahot-Panié Metamorphic Complex, associated with syn-rift volcanism. An Au–Sb metallogenic province is associated with the post-obduction Late Oligocene granitoids and co-genetic hydrothermal silica–carbonate (listwanite) zones in the Peridotite Nappe; Au is disseminated in the granites and Sb occurs as lodes in the silica–carbonate. Among the non-metallic mineral resources, barite, gypsum, magnesite, phosphate, clays, dimension stones, limestone for use as cement and as a neutralizer, and aggregates are all present. Gemstones such as jade and chrysoprase are only used locally. Late Cretaceous coal, which was briefly exploited in the past, is now considered to be a source rock for an offshore potential oil and gas system. Petroleum prospectivity is currently focused on the Fairway Basin. Several low-enthalpy thermo-mineral springs with a weak geothermal energy potential are known on Grande Terre.
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Ghent, E. D., J. C. Roddick, and P. M. Black. "40Ar/39Ar dating of white micas from the epidote to the omphacite zones, northern New Caledonia: tectonic implications." Canadian Journal of Earth Sciences 31, no. 6 (June 1, 1994): 995–1001. http://dx.doi.org/10.1139/e94-088.
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An 40Ar/39Ar study of white micas from high-pressure metamorphic rocks of northern New Caledonia yielded cooling ages of 37 ± 1 Ma for both epidote and omphacite zone samples. Whole-rock samples from the lawsonite zone yielded ages in the range 44–51 Ma with complicated age spectra, probably reflecting both detrital and newly grown micas. The areal extent of the mica samples, over 300 km2, suggests that the epidote and omphacite zone rocks cooled through the muscovite closure temperature, about 350 °C, as a coherent cooling unit. Simple thermal modeling suggests that these rocks could have closed at similar times if the unroofing rate were greater than 2–10 mm∙a−1. Lawsonite zone rocks occur structurally within about 0.5 km of garnet–omphacite rocks, suggesting the possibility of major postmetamorphic tectonic displacement.
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Maurizot, P., D. Cluzel, S. Meffre, H. J. Campbell, J. Collot, and B. Sevin. "Chapter 3 Pre-Late Cretaceous basement terranes of the Gondwana active margin of New Caledonia." Geological Society, London, Memoirs 51, no. 1 (2020): 27–52. http://dx.doi.org/10.1144/m51-2016-11.
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AbstractThe basement under the Late Cretaceous unconformity in New Caledonia consists of three amalgamated terranes. They are all oceanic, arc-related and developed offshore from the eastern Gondwana active margin during periods of marginal basin development. Téremba Terrane is composed of deep sea Permian to Mesozoic arc-derived volcanic rocks and greywackes. The Koh–Central Terrane includes at its base an ophiolite with island arc tholeiites and boninites (Koh Ophiolite) of Late Carboniferous to Early Permian age overlain by a thick sequence of greywacke (Central Range Volcaniclastic Rocks) of Permian to Late Jurassic age. The Téremba Terrane and the Koh–Central Terrane may be part of the same forearc basin, with the rocks from the Koh–Central Terrane deposited in a deeper environment. The Boghen Terrane is a metamorphic complex composed of schists, broken formations and mafic–ultramafic mélange, derived from mixed terrigenous and volcanic sources. The overall fine grain size and laminar bedding suggest deep sea and more distal deposition than the other terranes. The maximum depositional ages from detrital zircons suggest deposition during the Early Jurassic to Early Cretaceous. The terrane is interpreted as a metamorphosed subduction complex that includes blueschist and greenschist facies metamorphic rocks exhumed through the Koh–Central Terrane. At a regional scale, the nature of these three pre-Late Cretaceous terranes confirms the existing palaeogeographical reconstructions, which locate New Caledonia outboard the ocean–continent subduction that surrounded Gondwana during the Paleozoic and Early Mesozoic. A detailed analysis of these terranes and their relationship with East Australian terranes of the same age shows that a marginal basin system probably existed between mainland Gondwana and proto-New Caledonia and closed before the Late Cretaceous. A tentative detailed reconstruction of this margin during the Carboniferous–Early Cretaceous period is proposed.
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AOKI, K., B. F. WINDLEY, S. MARUYAMA, and S. OMORI. "Metamorphic P–T conditions and retrograde path of high-pressure Barrovian metamorphic zones near Cairn Leuchan, Caledonian orogen, Scotland." Geological Magazine 151, no. 3 (August 13, 2013): 559–71. http://dx.doi.org/10.1017/s0016756813000514.
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AbstractThe metamorphic P–T conditions and associated relationships of the Barrovian zones near Glen Muick were re-examined by focusing on the petrology and thermodynamics of rocks at Cairn Leuchan, where garnetite lenses and layers occur in surrounding garnet amphibolite in the highest-grade sillimanite zone. The representative mineral assemblages in the garnet-rich lenses and garnet amphibolite are garnet + quartz + clinopyroxene + plagioclase + amphibole ± epidote, and garnet + amphibole + quartz + plagioclase ± clinopyroxene ± epidote, respectively. The chemical compositions of constituent minerals are the same in both garnetite and garnet amphibolite. The metamorphic P–T conditions of these rocks were estimated by thermodynamic calculations. The results show that the rocks underwent high-pressure granulite facies metamorphism at P = c. 1.2–1.4 GPa and T = c. 770–800°C followed by amphibolite facies metamorphism at P = c. 0.5–0.8 GPa and T = c. 580–700°C. Integration of our new results with previously published data suggests that the retrograde P–T trajectory of the highest-grade Barrovian metamorphic rocks marks a temperature decrease during decompression from a crustal depth of the high-pressure granulite facies, which is much deeper than previously considered.
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MAJKA, JAROSLAW, STANISLAW MAZUR, MACIEJ MANECKI, JERZY CZERNY, and DANIEL K. HOLM. "Late Neoproterozoic amphibolite-facies metamorphism of a pre-Caledonian basement block in southwest Wedel Jarlsberg Land, Spitsbergen: new evidence from U–Th–Pb dating of monazite." Geological Magazine 145, no. 6 (September 10, 2008): 822–30. http://dx.doi.org/10.1017/s001675680800530x.
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AbstractSouthwest Spitsbergen, Wedel Jarlsberg Land, consists of two Proterozoic crustal blocks with differing metamorphic histories. Both blocks experienced Caledonian greenschist-facies metamorphism, but only the southern block records an earlier pervasive M1 amphibolite-facies metamorphism and strong deformational fabric. In situ EMPA total-Pb monazite geochronology from both matrix and porphyroblast inclusion results indicate that the older M1 metamorphism occurred at 643 ± 9 Ma, consistent with published cooling ages of c. 620 Ma (hornblende) and 580 Ma (mica) obtained from these same rocks. This region thus contains a lithostratigraphic profile and metamorphic history which are unique within the Svalbard Archipelago. Documentation of a pervasive late Neoproterozoic Barrovian metamorphism is difficult to reconcile with a quiescent non-tectonic regime typically inferred for this region, based on the occurrence of rift-drift sequences on the Baltic and Laurentian passive margins. Instead, our new metamorphic age implies an exotic origin of the pre-Devonian basement exposed in SW Spitsbergen and supports models of terrane assembly postulated for the Svalbard Archipelago.
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Aoki, K., B. F. Windley, S. Maruyama, and S. Omori. "Discussion of ‘Metamorphic P–T and retrograde path of high-pressure Barrovian metamorphic zones near Cairn Leuchan, Caledonian orogen, Scotland’." Geological Magazine 151, no. 4 (March 4, 2014): 758–63. http://dx.doi.org/10.1017/s0016756813001106.
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K. Aoki, B. F. Windley, S. Maruyama & S. Omori reply: First, we thank Viete, Oliver & Wilde for their interesting and thought-provoking comments on the timing of the high-pressure granulite facies (HGR) metamorphism recorded in metamorphic rocks at Cairn Leuchan, Scotland, published by Aoki et al. (2013). Based on new metamorphic data of garnetites and garnet-amphibolites at Cairn Leuchan and new zircon U–Pb ages of amphibolitized eclogite at Tomatin, we suggested in our publication that the HGR metamorphism was retrograde after eclogite facies before the c. 470 Ma ‘Barrovian metamorphism’. Viete, Oliver & Wilde however speculate that the HGR metamorphism at Cairn Leuchan may have occurred at c. 1000 Ma, as a result of their new U–Pb zircon age of the Cowhythe Gneiss at Portsoy and from previous studies of the geological structure and geochronology. We are grateful for this opportunity to describe, albeit in a preliminary manner, our new understanding and tectonic model of the Caledonian orogen in Scotland and western Ireland of which the Barrovian metamorphism is a key component. A reply to a comment is not the correct place to propose an entirely new paradigm for such a classic orogen, but we will present our model more fully in a future publication.
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Uruski, C., and P. Baillie. "MESOZOIC EVOLUTION OF THE GREATER TARANAKI BASIN AND IMPLICATIONS FOR PETROLEUM PROSPECTIVITY." APPEA Journal 44, no. 1 (2004): 385. http://dx.doi.org/10.1071/aj03014.
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A paradigm of New Zealand petroleum geology was that the oldest source rocks known in the region were of Cretaceous age, so any older sedimentary rocks were considered to be economic basement. Two major projects have revealed that this is not universally the case and that a Jurassic petroleum system should now be considered.Firstly, the Astrolabe 2D speculative survey, acquired by TGS-NOPEC in 2001, has revealed that a significant section underlies the traditional Cretaceous petroleum systems. Secondly, the Wakanui–1 well, drilled by Conoco, Inpex and Todd in 1999, which has recently become open-file, penetrated a Mid-Jurassic coal measure sequence.Jurassic rocks, including coal measure units, are known onshore in New Zealand, They are part of the Murihiku Supergroup, one of the basement terranes comprising the Permian to Cretaceous volcanic arc that forms the basement rocks of the present New Zealand landmass. Wherever they have been seen in outcrop, these rocks generally record low grade metamorphism and have been discounted as petroleum source rocks. Where rocks of the same age were deposited distal to the volcanic arc (and the effects of heat and pressure), however, they may form components of an effective petroleum system.The New Caledonia Basin, extending more than 2,000 km from Taranaki to New Caledonia, may have been the site of a Mesozoic back-arc basin. Jurassic coal measure successions and their equivalent marine units may be locally, or regionally important as source rocks. Implications of a Jurassic petroleum system for prospectivity of the region are investigated.
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Majka, Jarosław, Karolina Kośmińska, Stanisław Mazur, Jerzy Czerny, Karsten Piepjohn, Maciej Dwornik, and Maciej Manecki. "Two garnet growth events in polymetamorphic rocks in southwest Spitsbergen, Norway: insight in the history of Neoproterozoic and early Paleozoic metamorphism in the High Arctic." Canadian Journal of Earth Sciences 52, no. 12 (December 2015): 1045–61. http://dx.doi.org/10.1139/cjes-2015-0142.
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Geochronological studies in northern Wedel Jarlsberg Land, southwestern Svalbard (Norway), showed that the Tonian (c. 950 Ma) igneous rocks were subjected to metamorphism during the Torellian (c. 640 Ma) and early Caledonian (470–460 Ma) events. Predominant augen gneisses, derived from a Tonian protolith, are intercalated in that area, with schists comprising two distinct metamorphic mineral assemblages. The M1 (Torellian) assemblage containing garnet-I + quartz + plagioclase-I + biotite-I + muscovite-I was formed under amphibolite-facies conditions at c. 550–600 °C and 5–8 kbar (1 kbar = 100 MPa). The M2 (Caledonian) assemblage comprising garnet-II + quartz + plagioclase-II + biotite-II + muscovite-II + zoisite + chlorite crystallized at c. 500–550 °C and 9–12 kbar, corresponding to epidote–amphibolite facies conditions. The M2 mineral assemblage constitutes the pervasive Caledonian fabric of the schists that was subsequently reactivated in a left-lateral strike-slip shear regime. The subsequent c. 70° clockwise rotation of the original structure to its present position was caused by a large-scale passive rotation during the Paleogene Eurekan orogeny. The new pressure–temperature estimates suggest that metamorphic basement in the study area was consolidated during the Torellian middle-grade event and then overprinted by Caledonian moderate- to high-pressure subduction-related metamorphism. A following sinistral shear zone assembled the present structure of basement units. Our results pose a question about the possible extent of Torellian precursor to the Caledonian basement across the High Arctic and the scale of its subsequent involvement in early Caledonian subduction. In conjunction with previous studies, the results suggest a possible correlation between southwestern Spitsbergen and the Pearya Terrane in Ellesmere Island.
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POTEL, S., R. FERREIRO MÄHLMANN, W. B. STERN, J. MULLIS, and M. FREY. "Very Low-grade Metamorphic Evolution of Pelitic Rocks under High-pressure/Low-temperature Conditions, NW New Caledonia (SW Pacific)." Journal of Petrology 47, no. 5 (February 21, 2006): 991–1015. http://dx.doi.org/10.1093/petrology/egl001.
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Moczydłowska, Małgorzata. "Comments on ‘Evidence for a Caledonian orogeny in Poland’ by J. D. Johnston, J. A. Tait, J. H. Oliver and F. G. Murphy." Transactions of the Royal Society of Edinburgh: Earth Sciences 86, no. 3 (1995): 227–30. http://dx.doi.org/10.1017/s0263593300002236.
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In a recent paper Johnston et al. (1994) have provided an innovative interpretation of the tectonostratigraphic relationships between distinct terranes juxtaposed along the Intra–Sudetic Fault in the Sudetes Mountainsof the Polish Variscides. They identified this fault as a major crustal fracture between Gondwana and Baltica, rramed the Tornquist Suture, resulting from the closure of the Tornquist Sea during the Caledonian orogeny. This interpretation is based on new U/Pb ages on zircon and titanite from igneous and metamorphic rocks (Oliver et al. 1993), field observations and reassessment of pre–existing data. Previously, the Sudetes were generally thought to haveformed during the Hercynian orogeny, although Caledonian age deformation was also inferred (Oberc 1977, 1986; Don 1984, 1986, 1990).
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HELLMAN, F. J., D. G. GEE, T. GJELSVIK, and A. M. TEBENKOV. "Provenance and tectonic implications of Palaeoproterozoic (c. 1740 Ma) quartz porphyry clasts in the basal Old Red Sandstone (Lilljeborgfjellet Conglomerate Formation) of northwestern Svalbard's Caledonides." Geological Magazine 135, no. 6 (November 1998): 755–68. http://dx.doi.org/10.1017/s0016756898001757.
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The Lilljeborgfjellet Conglomerate Formation composes the lower part of the alluvial Siktefjellet Group of northwestern Spitsbergen's Old Red Sandstone succession. Siktefjellet strata are of late Silurian or early Devonian age, but lack precise age-diagnostic fossils. They are unconformably overlain by conglomerates and sandstones of the Red Bay Group, which contain a well established fish fauna of Lochkovian age. The Lilljeborgfjellet Conglomerate rests with a major unconformity on high-grade (with eclogites) schists and gneisses, with associated corona gabbros and granitic gneisses. Previous isotope-age studies have shown that these igneous rocks yield U/Pb ages of c. 950 Ma, and that the eclogite facies metamorphism may be of Caledonian or late Neoproterozoic age. The high P/high T rocks are intercalated with and overlain by schists affected only by Caledonian amphibolite facies metamorphism, recorded by 40Ar/39Ar and Rb/Sr cooling ages of 400–430 Ma.In the Lochkovian Red Bay Group of the Raudfjorden Graben, two horizons of tuffites occur, interbedded with sandstones. New studies of eight zircons from these volcanic rocks have provided single-zircon lead-evaporation ages of c. 950 and c. 1350 Ma; one yielded 440 Ma. All these zircons are probably derived from the underlying basement rocks, the ages being significantly older than the Devonian host strata (c. 410 Ma).The clasts in the Lilljeborgfjellet Conglomerate are generally angular to subrounded and derived locally from the underlying high-grade metamorphic complex. A subordinate (usually less than 1%, but up to about 10%) component of the clasts is a quartz porphyry that is not known in the exposed bedrock anywhere in northwestern Spitsbergen. The quartz porphyries are better rounded than the other clasts; however, the maximum diameter reaches 1.5 metres, indicating that transport distances are unlikely to have exceeded a few kilometres. Three quartz porphyry boulders have been dated by the single-zircon lead-evaporation method and shown to be of Palaeoproterozoic age, yielding ages of 1735±4, 1736±5 and 1739±5 Ma that have not previously been detected in the northwestern part of Svalbard's Caledonides.The quartz porphyry clasts show no evidence of the widespread high-grade tectonothermal activity of Mesoproterozoic and early Palaeozoic age that influenced northwestern Spitsbergen. It is therefore concluded that the most probable source of these clasts lies to the east in the unexposed basement beneath the Old Red Sandstones of the Andrèeland–Dicksonland Graben. The Lilljeborgfjellet quartz porphyry clasts are closely similar in age to the granitic rocks of Ny Friesland. Whereas the latter were subject to Caledonian high amphibolite facies metamorphism, the quartz porphyry clasts have only been affected by a low greenschist facies overprint. Nevertheless, the similarity in age suggests an affinity to Ny Friesland and it is proposed here that the Breibogen–Bockfjorden Fault defines the most important boundary between Svalbard's Caledonian terranes.
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GREILING, R. O., J. C. GRIMMER, H. DE WALL, and L. BJÖRK. "Mesoproterozoic dyke swarms in foreland and nappes of the central Scandinavian Caledonides: structure, magnetic fabric, and geochemistry." Geological Magazine 144, no. 3 (May 2007): 525–46. http://dx.doi.org/10.1017/s0016756807003299.
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As an example of microstructural and magnetic fabric evolution, and geochemistry of mafic dykes during a subsequent orogenic overprint, a major Mesoproterozoic dyke complex in Scandinavia, the Västerbotten complex of the Central Scandinavian Dolerite Group, is traced westwards into the crystalline nappes of the early Phanerozoic Caledonian orogen. Using geophysical, field, microscopic, magnetic and geochemical information, dykes and sills are characterized, and their overprint during Caledonian orogeny documented. The Västerbotten complex is composed of sets of dykes, trending NE–SW, NW–SE and WNW–ESE, respectively. Similar dykes are exposed in allochthonous positions (Lower and Middle allochthons) in the Caledonian fold-and-thrust belt. The autochthonous dykes are generally undeformed and retain both their primary texture and mineralogy. Chilled margins are well preserved. In the Caledonian Lower and Middle allochthons, similar dykes in crystalline basement rocks are progressively faulted and sheared when proceeding from the marginal to the interior parts of the orogen. Dyke margins are more likely to be sheared than the interior parts of dykes. In the Lower Allochthon, under very low- and low-grade metamorphic conditions, dykes are distinctly less competent than granitic host rocks. Thick dykes are more competent than gneisses; thin dykes do not show such competence contrasts. In the Middle Allochthon, metre-scale dykes with patches of altered plagioclase phenocrysts can still be discerned in low-strain domains. Highly sheared dykes are drawn out to thin layers of centimetre thickness. Dykes are deformed together with the crystalline country rocks under greenschist-grade metamorphic conditions without major competence contrasts. Magnetic fabrics show an evolution similar to the silicate mineral fabrics. The magnetic fabrics in the dykes are transformed successively from ferromagnetic–magmatic in the Autochthon to ferromagnetic deformational in the Lower Allochthon and, finally, paramagnetic deformational in the Middle Allochthon. As a consequence, the magnetic susceptibility decreases for several orders of magnitude. Geochemically, the dykes are dominantly sub-alkaline basalts typical for continental tholeiites and can be distinguished from the Neoproterozoic dykes in the Särv-Nappe equivalents (highest part of the Middle Allochthon), which show a more MORB-like (E-MORB) magmatic signature. Preliminary age information from a dyke in the Lower Allochthon of the Børgefjell area and the Middle Allochthon is consistent with the assumption that these dykes are time equivalent with the Central Scandinavian Dolerite Group. Therefore, the studied dykes may represent an extension of the Västerbotten complex or a new complex of the Central Scandinavian Dolerite Group. According to section restorations, the Caledonian allochthons were situated further WNW relative to their present position, and, originally, the mafic dykes cut across all of the Fennoscandian lithosphere, at least to the present Atlantic margin and the earlier passive margin of the Baltica terrane. As a consequence, these dykes may provide a link for pre-Caledonian and pre-Grenvillian plate reconstructions.
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MAJKA, JAROSŁAW, YARON BE’ERI-SHLEVIN, DAVID G. GEE, JERZY CZERNY, DIRK FREI, and ANNA LADENBERGER. "Torellian (c. 640 Ma) metamorphic overprint of Tonian (c. 950 Ma) basement in the Caledonides of southwestern Svalbard." Geological Magazine 151, no. 4 (November 13, 2013): 732–48. http://dx.doi.org/10.1017/s0016756813000794.
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AbstractIon microprobe dating in Wedel Jarlsberg Land, southwestern Spitsbergen, provides new evidence of early Neoproterozoic (c. 950 Ma) meta-igneous rocks, the Berzeliuseggene Igneous Suite, and late Neoproterozoic (c. 640 Ma) amphibolite-facies metamorphism. The older ages are similar to those obtained previously in northwestern Spitsbergen and Nordaustlandet where they are related to the Tonian age Nordaustlandet Orogeny. The younger ages complement those obtained recently from elsewhere in Wedel Jarlsberg Land of Torellian deformation and metamorphism at 640 Ma. The Berzeliuseggene Igneous Suite occurs in gently N-dipping, top-to-the-S-directed thrust sheets on the eastern and western sides of Antoniabreen where it is tectonically intercalated with younger Neoproterozoic sedimentary formations, suggesting that it provided a lower Tonian basement on which upper Tonian to Cryogenian sediments (Deilegga Group) were deposited. They were deformed together during the Torellian Orogeny, prior to deposition of Ediacaran successions (Sofiebogen Group) and overlying Cambro-Ordovician shelf carbonates, and subsequent Caledonian and Cenozoic deformation. The regional importance of the late Neoproterozoic Torellian Orogeny in Svalbard's Southwestern Province and its correlation in time with the Timanian Orogeny in the northern Urals as well as tectonostratigraphic similarities between the Timanides and Pearya (northwestern Ellesmere Island) favour connection of these terranes prior to the opening of the Iapetus Ocean and Caledonian Orogeny.
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Kos'ko, M., and E. Korago. "Review of geology of the New Siberian Islands between the Laptev and the East Siberian Seas, North East Russia." Stephan Mueller Special Publication Series 4 (September 17, 2009): 45–64. http://dx.doi.org/10.5194/smsps-4-45-2009.
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Abstract. The New Siberian Islands comprise De Long Islands, Anjou Islands, and Lyakhov Islands. Early Paleozoic, Mesozoic and Cenozoic sediments and igneous rocks are known on the De Long Islands. Cambrian slate, siltstone, mudstone and silicified limestone occur on Bennett Island. Ordovician volcanogenic turbidites, lavas, and small intrusions of andesite-basalt, basalt, dolerite, and porphyritic diorite were mapped on Henrietta Island. The igneous rocks are of calc-alkaline island arc series. The Ordovician age of the sequence was defined radiometrically. Early Paleozoic strata were faulted and folded presumably in the Caledonian time. Early Cretaceous sandstone and mudstone are known on Bennett Island. They are overlain by a 106–124 Ma basalt unit. Cenozoic volcanics are widespread on the De Long Islands. Zhokhov Island is an eroded stratovolcano. The volcanics are mostly of picrite-olivine type and limburgite. Radiometric dating indicates Miocene to Recent ages for Cenozoic volcanism. On the Anjou islands Lower-Middle Paleozoic strata consist of carbonates, siliciclastics, and clay. A Northwest-southeast syn-sedimentary facies zonation has been reconstructed. Upper Paleozoic strata are marine carbonate, clay and siliciclastic facies. Mudstone and clay predominate in the Triassic to Upper Jurassic section. Aptian-Albian coal bearing deposits uconformably overlap lower strata indicating Early Cretaceous tectonism. Upper Cretaceous units are mostly clay and siltstone with brown coal strata resting on Early Cretaceous weathered rhyolite. Cenozoic marine and nonmarine silisiclastics and clay rest upon the older units with a transgressive unconformity including a weathering profile in the older rocks. Manifestations of Paleozoic and Triassic mafic and Cretaceous acidic magmatism are also found on these islands. The pre-Cretaceous structure of the Anjou islands is of a block and fold type Late Cimmerian in age followed by faulting in Cenozoic time. The Lyakhov islands are located at the western end of the Late Cimmerian South Anyui suture. Sequences of variable age, composition, and structural styles are known on the Lyakhov Islands. These include an ancient metamorphic sequence, Late Paleozoic ophiolitic sequence, Late Mesozoic turbidite sequence, Cretaceous granites, and Cenozoic sediments. Fold and thrust imbricate structures have been mapped on southern Bol'shoi Lyakhov Island. North-northwestern vergent thrusts transect the Island and project offshore. Open folds of Jurassic–Early Cretaceous strata are characteristic of Stolbovoi and Malyi Lyakhov islands. Geology of the New Siberian Islands supports the concept of a circum Arctic Phanerozoic fold belt. The belt is comprised of Caledonian, Ellesmerian, Early Cimmerian and Late Cimmerian fold systems, manifested in many places on the mainland and on islands around the Arctic Ocean. Knowledge of the geology of the New Siberian Islands has been used to interpret anomalous gravity and magnetic field maps and Multi Channel Seismic (MCS) lines. Two distinguishing structural stages are universally recognized within the offshore sedimentary cover which correlate with the onshore geology of the New Siberian Islands. Dating of the upper structural stage and constituent seismic units is based on structural and stratigraphic relationships between Late Mesozoic and Cenozoic units in the archipelago. The Laptev Sea–western East Siberian Sea seismostratigraphic model for the upper structural stage has much in common with the seismostratigraphic model in the American Chukchi Sea.
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Veselovskiy, Roman V., Róbert Arató, Tanya E. Bagdasaryan, Alexander V. Samsonov, Alexandra V. Stepanova, Andrey A. Arzamastsev, and Mariya S. Myshenkova. "New Apatite Fission-Track Data from the Murmansk Craton, NE Fennoscandia: An Echo of Hidden Thermotectonic Events." Minerals 10, no. 12 (December 6, 2020): 1095. http://dx.doi.org/10.3390/min10121095.
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For a long time, the thermal history of northeastern (NE) Fennoscandia in the Phanerozoic and Precambrian remained unknown, since no thermochronological studies were carried out within the Kola Peninsula area. Two years ago, we developed the first model of tectono-thermal evolution of the Kola Peninsula territory for the last 1.9 Gyr using a set of newly obtained apatite fission-track (AFT) and Ar/Ar thermochronological data. However, the low-temperature history of the most ancient tectonic unit of the northeastern part of the Kola Peninsula—the Archean Murmansk craton—remained poorly constrained due to the lack of AFT data. In this paper, we present the first results of AFT studies of 14 samples representing intrusive and metamorphic Precambrian rocks, located within the Murmansk craton of NE Fennoscandia. AFT ages and track length distributions indicate a similar tectono-thermal evolution of Precambrian tectonic units in NE Fennoscandia over the last 300 Myr. The AFT ages are distributed between ca. 177 and ca. 384 Ma; their median value, ~293 Ma, confirms the presence of a previously identified hidden thermal event that took place at about 300 Ma. However, a detailed analysis of the AFT age distribution shows the presence of three statistically distinguishable age components: 180–190 Ma (C1), 290–320 Ma (C2) and 422 Ma (C3). We assume that the relatively young AFT ages of C1 may originate from apatite crystals with low thermal resistivity. Remarkably, this value coincides with the initial stage of the Barents Sea magmatic province activity during large-scale plume-lithospheric interaction, as well as with the assumed age of an enigmatic remagnetization event throughout the Kola Peninsula. C2 ages can be observed in both the gabbroic and non-gabbroic samples, whereas C3 ages can only be found in gabbro. It is supposed that C2 ages, similarly to the Central Kola terrane, correspond to a cooling event related to the denudation of a thick sedimentary cover, representing a continuation of the Caledonian foreland basin towards NE Fennoscandia. C3 ages may be associated with a thermal event corresponding to the Caledonian collisional orogeny.
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Higgins, A. K. "Geology of central and eastern North Greenland." Rapport Grønlands Geologiske Undersøgelse 128 (December 31, 1986): 37–54. http://dx.doi.org/10.34194/rapggu.v128.7923.
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A historical review of geological research in North Greenland is followed by a summary of the main results of the 1978-80 GGU expeditions to the region. New outcrops of Archaean and early Proterozoic crystalline rocks are recorded only as xenoliths in dykes and volcanic centres. A revised stratigraphy is applied to the middle Proterozoic Independence Fjord Group sandstones, while petrographic and isotopic studies have been made of the cross-cutting Midsommersø dolerites and the overlying Zig-Zag Dal Basalt Formation. No convincing evidence has been found of a Carolinidian orogenic episode separating these units from succeeding late Proterozoic sedimentary sequences. Lower Palaeozoic sediments dominate North Greenland and are divided into southern shelf and northern trough successions; new or revised stratigraphies are now applied in both settings. The shelf-trough boundary can be shown to have moved south with time, and a major early Silurian expansion of the trough is related to shelf subsidence and a new phase of turbidite deposition derived from the rising East Greenland Caledonian mountains. Devonian - Middle Carboniferous (Ellesmerian) deformation brought deposition to a close and created the North Greenland fold belt, in which deformation intensity and metamorphic grade increase northwards. Thin-skinned thrusting in association with west or south-facing folds is important in southern areas; this is one of the main differences in interpretation compared to earlier work in the fold belt. New outcrops of post-ElIesmerian sediments (Wandel Sea Basin) have mainly been recorded as fault or thrust bounded sequences; a new stratigraphy is applied to the Wandel Sea Basin succession. Cretaceous - Tertiary events include a suite of volcanic centres, dyke swarms, the Kap Washington Group volcanics, and faults and thrusts of Tertiary (Eurekan) age; all have been studied anew, as have the Quaternary deposits.
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Samson, Scott D., Sandra M. Barr, and Chris E. White. "Nd isotopic characteristics of terranes within the Avalon Zone, southern New Brunswick." Canadian Journal of Earth Sciences 37, no. 7 (July 1, 2000): 1039–52. http://dx.doi.org/10.1139/e00-015.
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Nd isotopic data are presented for rock units in four terranes within the traditional Avalon Zone of southern New Brunswick. Initial εNd values for igneous rocks within the Caledonia terrane range from -1.6 to +4.6, whereas values for sedimentary rocks range from -8.4 to +3.6. A granite within the Kingston terrane has εNd(438 Ma) = +4.0. Nd isotopic compositions for the Kingston and Caledonia terranes are similar to those of the Mira terrane in Cape Breton Island, the Antigonish Highlands of Nova Scotia, and plutonic rocks of eastern Newfoundland. Each of these regions may be a dismembered part of a single terrane, the Avalon terrane sensu stricto. Initial εNd values for rocks from the Brookville terrane range from -1.3 to +2.8. The Coverdale anorthosite within the Brookville terrane has a present day εNd value of -12.1 and a depleted mantle model age of 1.3 Ga, similar to Mesoproterozoic anorthosites in Laurentia. Clastic sedimentary rocks in the Green Head Group have εNd(750 Ma) values of -2.0 and -10.9. Viewed as a whole, the Brookville terrane is isotopically more evolved than the Caledonia terrane. Initial εNd values for rocks in the New River terrane range from -2.9 to 0.0. The Nd isotopic composition of the Brookville and New River terranes are thus similar to one another and have isotopic character similar to that of the Bras d'Or terrane of Cape Breton Island. It is suggested that all three regions belong to a single terrane (Bras d'Oria).
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Vitale Brovarone, A., P. Agard, P. Monié, A. Chauvet, and A. Rabaute. "Tectonic and metamorphic architecture of the HP belt of New Caledonia." Earth-Science Reviews 178 (March 2018): 48–67. http://dx.doi.org/10.1016/j.earscirev.2018.01.006.
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Grambling, Jeffrey A., Michael L. Williams, Christopher K. Mawer, and Roger F. Smith. "Metamorphic evolution of Proterozoic rocks in New Mexico." Geological Society, London, Special Publications 43, no. 1 (1989): 461–67. http://dx.doi.org/10.1144/gsl.sp.1989.043.01.42.
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Sevin, B., P. Maurizot, D. Cluzel, E. Tournadour, S. Etienne, N. Folcher, J. Jeanpert, et al. "Chapter 7 Post-obduction evolution of New Caledonia." Geological Society, London, Memoirs 51, no. 1 (2020): 147–88. http://dx.doi.org/10.1144/m51-2018-74.
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AbstractThe post-obduction formations of Grande Terre, New Caledonia, comprise igneous intrusions, regolith cover, and marine and terrestrial sedimentary rocks. Two restricted Late Oligocene granitoid bodies are intruded into the Peridotite Nappe and its substrate in the south of the island. Thick regolith cover developed over the Peridotite Nappe from the Late Oligocene or earlier. The Népoui Group comprises Late Oligocene–Early Miocene mixed marine carbonate and siliciclastic deposits. It mainly reworks the Peridotite Nappe and its regolith cover. Its development pattern is mainly controlled by tectonic uplift and subsidence. The Gwa N'Doro Formation on the eastern coast and the Fluvio-lacustrine Formation in the south are remnants of the Miocene–Present river network. Offshore, thick Oligocene to Neogene sedimentary successions are imaged by seismic surveys on the margins of Grande Terre, although these successions have not been drilled and remain undated. Several dredges have recovered shallow Miocene sedimentary rocks, indicating substantial Neogene subsidence. Quaternary formations are represented inland by aeolianite, vertisols and calcrete and offshore by the large barrier reef–lagoon complex, the onset of which is dated at c. 400 ka. This chapter discusses the different models proposed for the post-obduction evolution of Grand Terre.
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Vitale Brovarone, A., and P. Agard. "True metamorphic isograds or tectonically sliced metamorphic sequence? New high-spatial resolution petrological data for the New Caledonia case study." Contributions to Mineralogy and Petrology 166, no. 2 (May 29, 2013): 451–69. http://dx.doi.org/10.1007/s00410-013-0885-2.
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GHENT, EDWARD D., MAVIS Z. STOUT, P. M. BLACK, and R. N. BROTHERS. "Chloritoid-bearing rocks associated with blueschists and eclogites, northern New Caledonia." Journal of Metamorphic Geology 5, no. 2 (April 1987): 239–54. http://dx.doi.org/10.1111/j.1525-1314.1987.tb00382.x.
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Tajčmanová, Lucie, Paola Manzotti, and Matteo Alvaro. "Under Pressure: High-Pressure Metamorphism in the Alps." Elements 17, no. 1 (February 1, 2021): 17–22. http://dx.doi.org/10.2138/gselements.17.1.17.
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The mechanisms attending the burial of crustal material and its exhumation before and during the Alpine orogeny are controversial. New mechanical models propose local pressure perturbations deviating from lithostatic pressure as a possible mechanism for creating (ultra-)high-pressure rocks in the Alps. These models challenge the assumption that metamorphic pressure can be used as a measure of depth, in this case implying deep subduction of metamorphic rocks beneath the Alpine orogen. We summarize petro-logical, geochronological and structural data to assess two fundamentally distinct mechanisms of forming (ultra-)high-pressure rocks: deep subduction; or anomalous, non-lithostatic pressure variation. Furthermore, we explore mineral-inclusion barometry to assess the relationship between pressure and depth in metamorphic rocks.
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Labrado, Amanda, Terry L. Pavlis, Jeffrey M. Amato, and Erik M. Day. "The tectonic significance of the Early Cretaceous forearc-metamorphic assemblage in south-central Alaska based on detrital zircon U–Pb dating of sedimentary protoliths." Canadian Journal of Earth Sciences 52, no. 12 (December 2015): 1182–90. http://dx.doi.org/10.1139/cjes-2015-0046.
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A complex array of faulted arc rocks and variably metamorphosed forearc accretionary complex rocks form a mappable arc–forearc boundary in southern Alaska known as the Border Ranges fault (BRF). We use detrital U–Pb zircon dating of metasedimentary rocks within the Knik River terrane in the western Chugach Mountains to show that a belt of Early Cretaceous amphibolite-facies metamorphic rocks along the BRF was formed when older mélange rocks of the Chugach accretionary complex were reworked in a sinistral-oblique thrust reactivation of the BRF during a period of forearc plutonism. The metamorphic subterrane of the Knik River terrane has a maximum depositional age (MDA) of 156.5 ± 1.5 Ma and a detrital zircon age spectrum that is indistinguishable from the Potter Creek assemblage of the Chugach accretionary complex, supporting correlation of these units. These ages contrast strongly with new and existing data that show Triassic to earliest Jurassic detrital zircon ages from metamorphic screens in the plutonic subterrane of the Knik River terrane, a fragmented Early Jurassic plutonic assemblage generally interpreted as the basement of the Peninsular terrane. Based on these findings, we propose the following new terminology for the Knik River terrane: (1) “Carpenter Creek metamorphic complex” for the Early Cretaceous “metamorphic subterrane”, (2) “western Chugach trondhjemite suite” for the Early Cretaceous forearc plutons within the belt, (3) “Friday Creek assemblage” for a transitional mélange unit that contains blocks of the Carpenter Creek complex in a chert–argillite matrix, and (4) “Knik River metamorphic complex” in reference to metamorphic rocks engulfed by Early Jurassic plutons of the Peninsular terrane that represent the roots of the Talkeetna arc. The correlation of the Carpenter Creek metamorphic complex with the Chugach mélange indicates that the trace of the BRF lies ∼1–5 km north of the map trace shown on geologic maps, although, like other segments of the BRF, this boundary is blurred by local complexities within the BRF system. Ductile deformation of the mélange is sufficiently intense that few vestiges of its original mélange fabric exist, suggesting the scarcity of rocks described as mélange in the cores of many orogens may result from misidentification of rocks that have been intensely overprinted by younger, ductile deformation.
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Salata, Dorota, and Alfred Uchman. "New interpretation of the provenance of crystalline material from Oligocene flysch deposits of the Skole Nappe, Poland: evidence from heavy minerals and clasts in the Nowy Borek section." Geologos 25, no. 2 (August 1, 2019): 163–74. http://dx.doi.org/10.2478/logos-2019-0015.
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Abstract The Futoma Member (Oligocene, Rupelian) of the Menilite Formation is present only in the northern part of the Skole Nappe. Some diatomitic layers of this member in the Nowy Borek section contain coarse-grained detrital material composed of a variety of metamorphic, volcanic and sedimentary rock fragments. The material derives from primary and secondary sources. Most abundant are debris of metamorphic rocks, mostly gneisses and mica schists. The metamorphic origin of these rocks is confirmed by the composition of heavy mineral assemblages and garnet chemistry. These rocks could have been transported from a local source located close to the margin of the Skole Basin or within that basin. The volcanic rocks reflect Paleogene volcanic activity that was widespread in the Carpathian region. Cherts, which could have been subjected to synsedimentary erosion, may have been derived from the older portions of the same formation.
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Kumar, B. Rajesh, Harsha Vardhan, and M. Govindaraj. "A new approach for estimation of properties of metamorphic rocks." International Journal of Mining and Mineral Engineering 3, no. 2 (2011): 109. http://dx.doi.org/10.1504/ijmme.2011.042426.
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Espeland, Marianne, Kjell Arne Johanson, and Rasmus Hovmöller. "Early Xanthochorema (Trichoptera, Insecta) radiations in New Caledonia originated on ultrabasic rocks." Molecular Phylogenetics and Evolution 48, no. 3 (September 2008): 904–17. http://dx.doi.org/10.1016/j.ympev.2008.06.006.
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Xiao, Ling-Ling, and Min-Hua Chen. "Metamorphic Age Comparison and Its Implications between the Zuoquan and Zanhuang Complexes in the Central North China Craton, Based on LA-ICP-MS Zircon U–Pb Dating." Minerals 9, no. 12 (December 13, 2019): 780. http://dx.doi.org/10.3390/min9120780.
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The Trans-North China Orogen (TNCO) is well-known as an early Precambrian orogenic belt in the North China Craton (NCC). Three meaningful groups of metamorphic ages have been reported in the metamorphic complexes throughout the TNCO, including c. 1.85 Ga, c. 1.95 Ga, and c. 2.5 Ga. The spatial distributions and relationships of these ages provide notable insight into the formation timing and tectonic evolution of the NCC basement. The Zuoquan and Zanhuang complexes are exposed in the south–central TNCO and are adjacent to the Eastern Block. In order to place new constraints on the timing of two phases of metamorphism that occurred in the complexes, combined U–Pb and rare earth element analyses were performed on zircons from different types of metamorphic rocks. Uranium–Pb zircon dating in this study shows that two groups of metamorphic ages of 1.88–1.85 Ga and 2.48–2.46 Ga were commonly recorded by metamorphic rocks in the Zanhuang and Zuoquan complexes, respectively. Our previous geochronological studies showed that metamorphic ages of c. 2.51 Ga and c. 1.90 Ga were locally recorded in the Zanhuang and Zuoquan complexes, respectively. These data indicate that metamorphic rocks in the two complexes underwent at least two phases of metamorphism, i.e., 2.51–2.46 Ga (Phase I) and 1.90–1.85 Ga (Phase II). In combination with previous studies regarding reaction microstructures, metamorphic pressure–temperature paths, and geochronology, the Phase II metamorphic ages are interpreted to be linked to the collision between the Western and Eastern Blocks along the TNCO between 1.97 Ga and 1.80 Ga, whereas the Phase I metamorphic ages, as a result of an earlier and extensive tectono-thermal event that occurred in the Eastern and Western Blocks of the NCC, were related to underplating of mantle-derived magma. It is inferred that the rocks with c. 2.51–2.46 Ga metamorphic ages in the two complexes formed in the Eastern Block and underwent regional metamorphism during that period, and then were tectonically involved in the TNCO and experienced c. 1.90–1.85 Ga metamorphism. Metamorphic peaks occurred at different crustal levels in the orogen, resulting in distinct metamorphic ages and peak conditions preserved by metamorphic rocks in the two complexes.
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WENDT, ANKE S., ALAN P. M. VAUGHAN, and ALEXANDER TATE. "Metamorphic rocks in the Antarctic Peninsula region." Geological Magazine 145, no. 5 (June 23, 2008): 655–76. http://dx.doi.org/10.1017/s0016756808005050.
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AbstractThe distribution of metamorphic rocks in the Antarctic Peninsula region, new quantitative peak pressure–temperature data along the Antarctic Peninsula, and a literature review on the current knowledge of metamorphic conditions in the Antarctic Peninsula region have been compiled into a single metamorphic map. The pressure–temperature data for the Antarctic Peninsula indicate (1) burial of supracrustal rocks to low to mid-crustal depth along the eastern and western side of the Antarctic Peninsula and on some islands adjacent to the western side of the peninsula; (2) uplift of lower- to mid-crustal metamorphic rocks along major shear and fault zones; and (3) a reversed succession of metamorphic grades for the western domain of the Antarctic Peninsula region compared to the eastern domain along the Eastern Palmer Land Shear Zone (EPLSZ) of the Antarctic Peninsula. The metamorphic data are consistent with oblique convergence between Alexander Island (the Western Domain), Palmer Land (Central Domain) and the Gondwana margin (the Eastern Domain), supporting a model of (1) exhumation and shearing of the higher pressure rocks from central western (up to 9.4 kbar) and from northeast (7 kbar to 9 kbar) Palmer Land, (2) the exhumation and shearing of low to medium pressure rocks in western Palmer Land and along the Eastern Palmer Land Shear Zone, and (3) shallow burial and subsequent exhumation of sediments of the Gondwana margin along the Eastern Palmer Land Shear Zone. Based on the high-amphibolite grade rocks exposed in central western Palmer Land, our data also support earlier suggestions that the Eastern Palmer Land Shear Zone is the surface expression of a northwest- to west-dipping, deep-level, high-temperature crustal shear zone extending below the western part of the Central Domain of the Antarctic Peninsula.
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Maurizot, P., D. Cluzel, M. Patriat, J. Collot, M. Iseppi, S. Lesimple, A. Secchiari, et al. "Chapter 5 The Eocene Subduction–Obduction Complex of New Caledonia." Geological Society, London, Memoirs 51, no. 1 (2020): 93–130. http://dx.doi.org/10.1144/m51-2018-70.
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AbstractConvergence and subduction started in the Late Paleocene, to the east of New Caledonia in the South Loyalty Basin/Loyalty Basin, leading to the formation of the Subduction–Obduction Complex of Grande Terre. Convergence during the Eocene consumed the oceanic South Loyalty Basin and the northeasternmost margin of Zealandia (the Norfolk Ridge). The attempted subduction of the Norfolk Ridge eventually led to the end-Eocene obduction. Intra-oceanic subduction started in the South Loyalty Basin, as indicated by high-temperature amphibolite (56 Ma), boninite and adakite series dykes (55–50 Ma) and changes in the sedimentation regime (55 Ma). The South Loyalty Basin and its margin were dragged to a maximum depth of 70 km, forming the high-pressure–low-temperature Pouébo Terrane and the Diahot–Panié Metamorphic Complex, before being exhumed at 38–34 Ma. The obduction complex was formed by the stacking from NE to SW of several allochthonous units over autochthonous Zealandia, including the Montagnes Blanches Nappe (Norfolk Ridge crust), the Poya Terrane (the crust of the South Loyalty Basin) and the Peridotite Nappe (the mantle lithosphere of the Loyalty Basin). A model of continental subduction accepted by most researchers is proposed and discussed. Offshore continuations and comparable units in Papua New Guinea and New Zealand are presented.
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Barr, Sandra M., Susan C. Johnson, Greg R. Dunning, Chris E. White, Adrian F. Park, Markus Wälle, and Amanda Langille. "New Cryogenian, Neoproterozoic, and middle Paleozoic U–Pb zircon ages from the Caledonia terrane, southern New Brunswick, Canada: better constrained but more complex volcanic stratigraphy." Atlantic Geology 56 (July 9, 2020): 163–87. http://dx.doi.org/10.4138/atlgeol.2020.007.
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New U–Pb zircon ages from volcanic, plutonic, and sedimentary units in the Avalonian Caledonia terrane of southern New Brunswick provide better timing constraints in this geologically complex area. Previous ca. 620 Ma ages from the Broad River Group are now corroborated by additional dates from felsic tuff in the Gordon Falls Formation and rhyolite in the former Fairfield (now East Branch Black River) Formation of 620 ± 5 Ma and 622 ± 1.9 Ma, respectively. Combined with ages ranging from ca. 625 Ma to 615 Ma from crosscutting plutons, the data suggest that the minimum age of the Broad River Group is about 615 Ma. A quartzfeldspar porphyry dyke in mafic volcanic rocks of the previously undated Long Beach Formation yielded an igneous crystallization age of 685 ± 10 Ma, the oldest unit yet dated in the Caledonia terrane but similar in age to porphyry in the Stirling belt in the Avalonian Mira terrane of Nova Scotia. The age of the Coldbrook Group was constrained previously by U–Pb (zircon) ages of volcanic rocks between 560 and 550 Ma as well as by similar ages from comagmatic plutons. Five additional samples from both volcanic and plutonic units lie in the same range of 560–550 Ma, including errors, demonstrating that the Coldbrook Group and related plutons formed in less than 10 million years. Such a large volume of mainly felsic magma erupted and emplaced in a short time span suggests a “supereruption/supervolcano” environment such as the late Cenozoic southwestern USA but not yet recognized at ca. 560–550 Ma elsewhere in Avalonia. Two units yielded Paleozoic ages: felsite of the Bloomsbury Mountain Formation with a zircon population at 427 ± 9 Ma, indicating a Silurian maximum emplacement age, and dacite of the Grassy Lake Formation with several zircon grains at 382.8 ± 8.3 Ma, indicating a maximum age of middle Devonian, the first rocks of this age to be identified in the Caledonia terrane.
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Sturm, Robert. "Microscopy and Microanalysis of Corona Textures in Eclogitic Greenschists from the Eastern Alps, Austria." Microscopy Today 16, no. 2 (March 2008): 26–31. http://dx.doi.org/10.1017/s1551929500055899.
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Metamorphic rocks formed under conditions of high temperature (>600°C) and high lithological pressure (>1 GPa) and being subject to a subsequent tectonic uplift commonly include a remarkable number of fascinating mineral textures. One type of these well known and extensively described high-grade metamorphic textures are the so-called corona structures or reaction rims which, by definition, are primarily based on metamorphic reactions that cause the formation of concentric layers of new mineral phases separating an older and unstable mineral core from a newer and equally unstable mineral matrix. In other words, corona structures in metamorphic rocks preserve evidence of changes in the environmental conditions (temperature, pressure, fugacity of H2O) experienced by the rock during its tectonometamorphic history.
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Maurizot, P., A. Bordenave, D. Cluzel, J. Collot, and S. Etienne. "Chapter 4 Late Cretaceous to Eocene cover of New Caledonia: from rifting to convergence." Geological Society, London, Memoirs 51, no. 1 (2020): 53–91. http://dx.doi.org/10.1144/m51-2017-18.
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AbstractIn New Caledonia, the cover refers to the autochthonous Late Cretaceous to Paleogene sedimentary and volcanic formations unconformably overlying the basement rocks and underlying the allochthonous nappes. The first period of deposition, broadly from the Late Cretaceous to Paleocene (c. 105–56 Ma) was controlled by extension and rifting. The second period, broadly the Eocene (c. 56–34 Ma), was dominated by convergence and contraction. The Late Cretaceous part of the cover consists of synrift conglomerates and coal-bearing deposits with interlayered bimodal, subduction-related and intra-plate volcanic rocks. The post-rift deposits are deep water sedimentary rocks deposited under anoxic conditions with reduced terrigenous input. The Paleocene to Eocene formations, mainly carbonates, attest to profound palaeogeographical changes and a switch to a different geodynamic regime, linked to the onset of Eocene convergence. The Middle to Late Eocene formations are typically composed of turbidites and breccias. They were deposited in a typical flexural foreland basin context as an upwards-coarsening sequence topped by an olistostrome. They are associated with tectonic convergence and east-dipping subduction that led to the end-Eocene obduction of ophiolitic nappes. This two-fold evolution, extension then compression, can be integrated in the wider framework of the plate tectonic evolution of the SW Pacific.
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Schmidt, Silke, Thorsten J. Nagel, and Nikolaus Froitzheim. "A new occurrence of microdiamond-bearing metamorphic rocks, SW Rhodopes, Greece." European Journal of Mineralogy 22, no. 2 (April 13, 2010): 189–98. http://dx.doi.org/10.1127/0935-1221/2010/0022-1999.
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Watkins, James M., and Michael A. Antonelli. "Beyond Equilibrium: Kinetic Isotope Fractionation in High-Temperature Environments." Elements 17, no. 6 (December 1, 2021): 383–88. http://dx.doi.org/10.2138/gselements.17.6.383.
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Igneous and metamorphic rocks exhibit greater isotopic heterogeneity than expected from equilibrium. Large nonequilibrium isotope effects can arise from diffusion and chemical reactions, such as crystal growth and dissolution. The effects are time-dependent and can, therefore, be used to probe timescales of igneous and metamorphic processes that are inaccessible to direct observation. New discoveries of isotopic variability in nature, informed by diffusion and reaction modeling, can provide unique insights into the formation of rocks in the interiors of planetary bodies.
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Genthon, Pierre, Jean-Lambert Join, and Julie Jeanpert. "Differential weathering in ultramafic rocks of New Caledonia: The role of infiltration instability." Journal of Hydrology 550 (July 2017): 268–78. http://dx.doi.org/10.1016/j.jhydrol.2017.04.059.
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Maurizot, P., B. Sevin, S. Lesimple, L. Bailly, M. Iseppi, and B. Robineau. "Chapter 10 Mineral resources and prospectivity of the ultramafic rocks of New Caledonia." Geological Society, London, Memoirs 51, no. 1 (2020): 247–77. http://dx.doi.org/10.1144/m51-2016-17.
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AbstractThe main metallic mineral resources of New Caledonia are hosted by the obducted Peridotite Nappe. Ni, Co, Cr and the Pt group elements (PGEs) are specific to this ultramafic terrane. Cr, as podiform chromitite in the uppermost mantle, is the only hypogene metal mined economically in the past. The largest chromitite deposits are located in the lherzolitic Tiébaghi Massif. Supergene Ni and Co deposits are concentrated by the tropical climate that has prevailed since the Miocene. New Caledonian lateritic Ni deposits account for 10% of the global Ni resources. Hydrous Mg silicate and oxide types coexist in a single deposit. A local genetic model based on geomorphological evolution is proposed. Sc is a prospective resource associated with these supergene deposits. The PGEs are a prospective resource associated with chromite, with potential in the hypogene, supergene and fluvio-littoral domains. Pt and Pd are the most significant elements. The transition zone between the upper mantle and crustal cumulates constitutes a regional Pt–Pd-enriched horizon. The concentrations are related to small disseminated chromite lenses in a pyroxene-rich lithology. The PGEs are concentrated in weathering profiles. The value of chromite-rich sands as placers or sand beach deposits might be enhanced by the occurrences of PGEs.
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Maurizot, P., J. Collot, D. Cluzel, and M. Patriat. "Chapter 6 The Loyalty Islands and Ridge, New Caledonia." Geological Society, London, Memoirs 51, no. 1 (2020): 131–45. http://dx.doi.org/10.1144/m51-2017-24.
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AbstractThe Loyalty Ridge lies to the east and NE of the Norfolk Ridge. The three main Loyalty Islands (Maré, Lifou and Ouvéa) emerge from the ridge at the same latitude as Grande Terre. The islands are uniformly composed of carbonate deposits, except for Maré, where Middle Miocene intra-plate basalts and associated volcaniclastic rocks form restricted outcrops. Miocene rhodolith limestones constitute the bulk of the carbonate cover of the three islands. On Maré, these platform accumulations are locally topped by a dolomitic hardground, which, in turn, is covered by Pliocene–Pleistocene coral-bearing formations. These coral reef constructions are preserved as elevated rims over all three islands and define an atoll stage in their development. The Pleistocene–Holocene palaeoshoreline indicators include fringing bioconstructions and marine notches and record both eustatic sea-level changes and tectonic deformation. The ridge has been in the forebulge region in front of the active Vanuatu subduction zone since the Pliocene and each of the three islands has been uplifted and tilted to varying degrees. Offshore, the Loyalty Ridge continues northwards to the d'Entrecasteaux Zone and southwards to the Three Kings Ridge. Although typically volcanic, the nature of the deep Loyalty Ridge remains unknown.
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Zozulya, Dmitry, Kåre Kullerud, Erling Ravna, Yevgeny Savchenko, Ekaterina Selivanova, and Marina Timofeeva. "Mineralogical and Geochemical Constraints on Magma Evolution and Late-Stage Crystallization History of the Breivikbotn Silicocarbonatite, Seiland Igneous Province in Northern Norway: Prerequisites for Zeolite Deposits in Carbonatite Complexes." Minerals 8, no. 11 (November 20, 2018): 537. http://dx.doi.org/10.3390/min8110537.
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The present work reports on new mineralogical and whole-rock geochemical data from the Breivikbotn silicocarbonatite (Seiland igneous province, North Norway), allowing conclusions to be drawn concerning its origin and the role of late fluid alteration. The rock shows a rare mineral association: calcite + pyroxene + amphibole + zeolite group minerals + garnet + titanite, with apatite, allanite, magnetite and zircon as minor and accessory minerals, and it is classified as silicocarbonatite. Calcite, titanite and pyroxene (Di36–46 Acm22–37 Hd14–21) are primarily magmatic minerals. Amphibole of mainly hastingsitic composition has formed after pyroxene at a late-magmatic stage. Zeolite group minerals (natrolite, gonnardite, Sr-rich thomsonite-(Ca)) were formed during hydrothermal alteration of primary nepheline by fluids/solutions with high Si-Al-Ca activities. Poikilitic garnet (Ti-bearing andradite) has inclusions of all primary minerals, amphibole and zeolites, and presumably crystallized metasomatically during a late metamorphic event (Caledonian orogeny). Whole-rock chemical compositions of the silicocarbonatite differs from the global average of calciocarbonatites by elevated silica, aluminium, sodium and iron, but show comparable contents of trace elements (REE, Sr, Ba). Trace element distributions and abundances indicate within-plate tectonic setting of the carbonatite. The spatial proximity of carbonatite and alkaline ultramafic rock (melteigite), the presence of “primary nepheline” in carbonatite together with the trace element distributions indicate that the carbonatite was derived by crystal fractionation of a parental carbonated foidite magma. The main prerequisites for the extensive formation of zeolite group minerals in silicocarbonatite are revealed.
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Och, D. J., E. C. Leitch, G. Caprarelli, and T. Watanabe. "Blueschist and eclogite in tectonic melange, Port Macquarie, New South Wales, Australia." Mineralogical Magazine 67, no. 4 (August 2003): 609–24. http://dx.doi.org/10.1180/0026461036740121.
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Abstract The Rocky Beach Metamorphic Melange contains metre-scale phacoids of high-P low-T metamorphic rocks embedded in chlorite-actinolite schist. The phacoids include eclogite, glaucophane schist and omphacitite and provide evidence for four episodes of metamorphism with mineral assemblages: M1 = actinolite-glaucophane-titanite-apaite, M2 = almandine-omphacite-lawsonite ±quartz, M3 = phengite- glaucophane-K-feldspar-quartz, and M4 = chlorite-actinolite-calcite-quartz-titanite-white mica ± albite ± talc. M1-M3 occurred at a Neoproterozoic-Early Palaeozoic convergent plate boundary close to the eastern margin of Gondwana. Peak metamorphic conditions were attained during the static phase M2, with temperatures of ~560°C and pressures in excess of 1.8 GPa, equivalent to a depth of burial of at least 54 km.
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Uzel, Jessica, Yves Lagabrielle, Serge Fourcade, Christian Chopin, Pierre Monchoux, Camille Clerc, and Marc Poujol. "The sapphirine-bearing rocks in contact with the Lherz peridotite body: New mineralogical data, age and interpretation." BSGF - Earth Sciences Bulletin 191 (2020): 5. http://dx.doi.org/10.1051/bsgf/2019015.
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Sapphirine-bearing rocks are described in the Aulus Basin (Ariège, France) in a contact zone between the Lherz peridotitic body and Mesozoic metasediments which underwent the Pyrenean Cretaceous high-temperature, low-pressure metamorphic event (Monchoux, 1970, 1972a, 1972b). Sapphirine crystals occur in layered clastic deposits characterized by an uncommon suite of Al-Mg-rich minerals. A detailed petrographic study of sixteen samples representative of the diversity of the Lherz sapphirine-bearing rocks is presented. These rocks include breccias and microbreccias with various compositions. Some samples are composed of polymineralic clasts and isolated minerals that derive from regionally well-known protoliths such as ultramafic rocks, meta-ophites, “micaceous hornfels”, and very scarce Paleozoic basement rocks. Nevertheless, a large portion of the sapphirine-bearing clastic suite is composed of mono- and polymineralic debris that derive from unknown protolith(s). We define a "sapphirine-bearing mineral suite” (SBMS) composed of monomineralic debris including: sapphirine + enstatite + aluminous spinel + Mg-amphiboles + Ca-amphiboles + kornerupine + accessory minerals (apatite, diopside, rutile, serpentine, smectite, tourmaline, vermiculite and a white mica). We highlight the dominance of metamorphic Keuper clastic materials in the studied rocks and the presence of inclusions of anhydrite and F-, Cl-, Sr-rich apatite in minerals of the Al-Mg-rich suite. The brecciated texture and the presence of unequivocal sedimentary features suggest that the sapphirine-bearing rocks were mechanically disaggregated and then experienced winnowing in underwater conditions with poor mixing between the different sources. We measured U-Pb rutile age data in order to provide constraints on the age of (one of) the protolith(s) of those clastic deposits. The obtained age (98.6 + 1.2 Ma) is interpreted as the age of metamorphism of this protolith of the SBMS. Previous works interpreted the Lherz sapphirine-bearing rocks as crustal protoliths modified at depth along the contact with the ultramafic rocks of the Lherz body during their ascent towards shallower depths. These new data imply: (i) an Upper Triassic to Lower Jurassic origin for the main protolith of the sapphirine-bearing rocks; (ii) the metamorphism of this protolith along an active hot crust–mantle detachment during Cenomanian times with the involvement of metasomatic, brine-type fluids; and (iii) its brecciation during the exhumation of the material due to the evolution of the detachment, followed by subsequent sedimentary reworking of the metamorphic material.
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Kozhoukharova, Evgenia. "Metamorphism – the invisible life of the rocks." Review of the Bulgarian Geological Society 82, no. 3 (December 2021): 58–60. http://dx.doi.org/10.52215/rev.bgs.2021.82.3.58.
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Three types of metamorphism are developed on the metamorphic complexes of the Rhodope Massif: a, widespread regional; b, high thermobaric in shear zones of friction and c, metasomatism, each with its own thermodynamic system. Friction generates energy that deforms, disintegrates and destroys minerals, subsequently recrystallized into new rocks.
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Degeling, H., S. Eggins, and D. J. Ellis. "Zr budgets for metamorphic reactions, and the formation of zircon from garnet breakdown." Mineralogical Magazine 65, no. 6 (December 2001): 749–58. http://dx.doi.org/10.1180/0026461016560006.
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AbstractThe construction of zirconium (Zr) budgets for metamorphic reactions in high-grade rocks provides new insight into zircon growth during metamorphism. In this study we target reactions involving garnet, as they enable zircon growth to be related to known pressure and temperature conditions. Two reactions involving the breakdown of Zr-bearing garnet from Rogaland, SW Norway have been investigated in detail, showing contrasting behaviour of Zr, with zircon formation being subject to the solubility of Zr in product phases. In the decompression reaction garnet + sillimanite + quartz → cordierite, Zr released during garnet breakdown cannot be incorporated into the cordierite structure, resulting in zircon nucleation and growth. In contrast, for the reaction garnet + biotite + sillimanite + quartz → osumilite + orthopyroxene + spinel + magnetite, no new zircon growth takes place, despite the garnet involved containing more than double the Zr concentration of the former reaction. In the latter case, all the Zr released by garnet breakdown can be detected in the product phases osumilite and orthopyroxene, thereby preventing growth of new metamorphic zircon. This study highlights the potential for high resolution geochronology in metamorphic rocks by relating zircon growth to specific metamorphic reactions.
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MENG, EN, CHAO-YANG WANG, ZHUANG LI, YAN-GUANG LI, HONG YANG, JIA CAI, LEI JI, and MENG-QI JIN. "Palaeoproterozoic metasedimentary rocks of the Ji'an Group and their significance for the tectonic evolution of the northern segment of the Jiao–Liao–Ji Belt, North China Craton." Geological Magazine 155, no. 1 (July 24, 2017): 149–73. http://dx.doi.org/10.1017/s0016756817000632.
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AbstractIn this paper we present new petrological and whole-rock geochemical data for the Palaeoproterozoic metasedimentary rocks in the upper part of the Ji'an Group within the Jiao–Liao–Ji Belt, China, as well as zircon U–Pb age dates andin situLu–Hf isotope data. The new data improve our understanding of the original nature of the metasedimentary rocks, further providing insights into their tectonic setting and the evolutionary history of the northern segment of the Jiao–Liao–Ji Belt. The zircons can be divided into two groups, viz., one of magmatic origin and the other of metamorphic origin. Zircon U–Pb dating gave mean or statistical peak ages for the magmatic zircons at 2035, 2082, 2178, 2343–2421, 2451–2545, 2643–2814 and 2923–3446 Ma, and mean peak ages for the metamorphic zircons at 1855 and 1912 Ma, which indicate a maximum depositional age of 2.03 Ga and two-stage metamorphic events atc. 1.91 and 1.85 Ga for the metasedimentary rocks. Geochemical data show that (1) the protoliths of these rocks were mainly sandstones, greywackes and claystones, together with some shales; (2) the main sources of the sedimentary material were Palaeoproterozoic granites and acid volcanic rocks, with minor contributions from Archaean granitic rocks; and (3) the sediments were deposited in an active continental margin setting. Moreover, along the northeastern margin of the Eastern Block of the North China Craton there is evidence of ancient crustal materials as old as 3.76 Ga, and multiple crustal growth events at 3.23–3.05, 2.80–2.65, 2.54–2.45 and 2.28–2.08 Ga.
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Patten, C. G. C., I. K. Pitcairn, F. Molnár, J. Kolb, G. Beaudoin, C. Guilmette, and A. Peillod. "Gold mobilization during metamorphic devolatilization of Archean and Paleoproterozoic metavolcanic rocks." Geology 48, no. 11 (July 21, 2020): 1110–14. http://dx.doi.org/10.1130/g47658.1.
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Abstract Volcanic rocks in Archean and Paleoproterozoic greenstone belts are abundant and have been suggested as a potential Au source for orogenic Au deposits. The behavior of Au during metamorphism of these rocks is, however, poorly known. We present ultra-low-detection-limit Au analyses from a suite of variably metamorphosed rocks from the Archean La Grande subprovince, Canada, and the Paleoproterozoic Central Lapland greenstone belt, Finland. Both areas are well endowed in Au and have great potential for discovery of new orogenic Au deposits. The metavolcanic rocks in these belts are grouped into tholeiite and calc-alkaline magmatic series, for which the protolith Au contents are calculated using Au versus Zr/Y power-law regressions from greenschist facies samples. In the tholeiitic rocks, Au is compatible during magmatic processes and decreases with differentiation, whereas in the calc-alkaline rocks, Au is incompatible and increases with differentiation. Mass-variation calculations show that as much as 77% and 59% of the initial Au content is lost during progressive metamorphism to upper amphibolite facies conditions (>550 °C) in La Grande and Central Lapland respectively. This study highlights, first, that metavolcanic rocks release Au during metamorphism in Archean and Paleoproterozoic greenstone belts and are thus a good potential source rocks for orogenic Au deposits; second, that the Au fertility of the metavolcanic rocks is controlled by their mantle source and magmatic evolution; and third, that the metamorphic devolatilization model can be applied to Archean and Paleoproterozoic orogenic Au deposits.
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Vlahov, Alexander. "XRD graphitization degrees: a review of the published data and new calculations, correlations, and applications." Geologica Balcanica 50, no. 1 (April 2021): 11–35. http://dx.doi.org/10.52321/geolbalc.50.1.11.
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A system for transformation, correlation, and unification of subordinations between d002 (Å) of semi-graphite and graphite, graphitization degrees and metamorphic temperature was created. The existing equations in the literature were analyzed and new equations, which determine correlation relationships between these parameters, were formulated. The effect of factors that control graphitization processes (temperature, general pressure and tectonic stress, structure and origin of primary carbon matter, orientation of carbon formations, fluids, mineral and chemical composition, and duration of processes) was also considered. It was concluded that the structural state of semi-graphite and graphite is reversible, and this can be used for facies diagnostics and studying of metamorphic history of graphite-bearing metamorphic rocks. A new scale for graphitization degrees was proposed.
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Yatsenkо, O. V. "A NEW PALEONTOLOGICAL STUDY OF METAMORPHIC ROCKS OF THE KRYVYI RIH SERIES." Collection of Scientific Works of the Institute of Geological Sciences of the NAS of Ukraine 2 (April 30, 2009): 23–25. http://dx.doi.org/10.30836/igs.2522-9753.2009.147863.
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Trépanier, S., L. Mathieu, and R. Daigneault. "CONSONORM_LG: New Normative Minerals and Alteration Indexes for Low-Grade Metamorphic Rocks." Economic Geology 110, no. 8 (November 9, 2015): 2127–38. http://dx.doi.org/10.2113/econgeo.110.8.2127.
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HIROI, Yoshikuni. "Pictorial 4: New Indicator of Partial Melting of High-grade Metamorphic Rocks." Journal of Geography (Chigaku Zasshi) 106, no. 5 (1997): Plate11—Plate12. http://dx.doi.org/10.5026/jgeography.106.5_plate11.
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