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Coupling of P–T–t–D histories of eclogite and metagreywacke—Insights to late Ordovician–Silurian crustal folding events recorded in the Beishan Orogen (NW China) J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-07-30 Jérémie Soldner, Pavla Štípská, Karel Schulmann, Chao Yuan, Robert Anczkiewicz, Dariusz Sala, Yingde Jiang, Yunying Zhang, Xinyu Wang
The Beishan complex is composed of orthogneiss and metagreywacke that both enclose bodies of eclogite and serves as a unique example for comparative petrological study of all these lithologies. The rocks show the earliest regional steep N‐S striking fabric (S2) preserved in low strain domains that are reworked by ubiquitous steep N‐NE dipping cleavage (S3). The eclogite shows an almost isotropic fabric
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Reconstruction of the prograde PT history of high‐P migmatitic paragneisses via melt‐reintegration approach and thermodynamic modelling (Allochthonous Complexes, NW Iberian Massif) J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-07-03 Irene Novo‐Fernández, Richard Albert, Ricardo Arenas, Antonio Garcia‐Casco, Rubén Díez Fernández, Sonia Sánchez Martínez, Axel Gerdes, Christian De Capitani
The Upper Units of the allochthonous complexes of the NW Iberian Massif constitute a terrane with continental affinity. They represent the vestiges of a Cambrian magmatic arc developed in the periphery of Gondwana (West African Craton) which was involved in the Devonian Variscan collision, undergoing high‐P, high‐T metamorphism. This includes ultramafic rocks, high‐P mafic rocks (eclogites and granulites)
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Hercynian subduction‐related processes within the metamorphic continental crust in Calabria (southern Italy) J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-07-03 Fabrizio Tursi, Richard Spiess, Vincenzo Festa, Rosa Anna Fregola
Linking the deformation history of mylonitized continental rocks to the progress of devolatilization reactions that trigger reaction softening is critical for the understanding of crustal scale processes. We have analysed the field geometries and microstructures of deformed rocks within the southern Hercynian belt in Calabria, as well as modelled the pressure–temperature–deformation (P–T–d) trajectory
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Multi‐stage metamorphism by progressive accretion of continental blocks, example from the Western Hindu Kush J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-06-30 Hezbullah Moiny, Shah Wali Faryad, Renata Čopjaková, Radim Jedlicka
Basement rocks from the Western Hindu Kush preserve evidence of multiple metamorphic and magmatic events that occurred along the boundary between the Archean–Proterozoic Afghan Central and Afghan–Tajik Blocks. To verify the different metamorphic stages or events, mineral textures and phase equilibria in metamorphic basement rocks and their age relations to magmatic episodes have been investigated.
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Mineral equilibrium constraints on the feasibility of diffusive H2O‐fluxed melting in the continental crust J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-06-23 Lorena A. Tafur, Johann F. A. Diener
Generation of granitic melt is believed to occur predominantly by melting through the breakdown of hydrous minerals. However, melting due to the influx of H2O has been recognized in anatectic amphibolite facies tonalitic grey gneisses, metagreywackes and low‐P metapelites, and has consequently been proposed as an alternative mechanism for the generation of granitic melt. Melting induced by H2O addition
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Simultaneous operation of opposing reaction mechanisms: The influence of matrix heterogeneity on post‐kinematic garnet crystallization in an inverted metamorphic sequence J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-06-17 Freya R. George, Fred Gaidies
Metapelites from the inverted Barrovian sequence in the Sikkim Himalaya (northeast India) are shown to be largely continuous with respect to their bulk rock compositions, microstructures and pressure–temperature–time–deformation (P–T–t–D) histories. However, the upper garnet–lower staurolite zone demarcates a region of microstructurally anomalous post‐kinematic garnet populations contained within strongly
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Multiple P–T–d–t paths reveal the evolution of the final Nuna assembly in northeast Australia J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-06-15 Silvia Volante, Amaury Pourteau, William J. Collins, Eleanore Blereau, Zheng‐Xiang Li, Matthijs Smit, Noreen J. Evans, Adam R. Nordsvan, Chris J. Spencer, Brad J. McDonald, Jiangyu Li, Christina Günter
The final assembly of the Mesoproterozoic supercontinent Nuna was marked by the collision of Laurentia and Australia at 1.60 Ga, which is recorded in the Georgetown Inlier of NE Australia. Here, we decipher the metamorphic evolution of this final Nuna collisional event using petrostructural analysis, major and trace element compositions of key minerals, thermodynamic modelling, and multi‐method geochronology
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Eocene migmatite formation and diachronous burial revealed by petrochronology in NW Himalaya, Zanskar J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-06-15 Pavla Štípská, Prokop Závada, Stephen Collett, Andrew R. C. Kylander‐Clark, Bradley R. Hacker, Anne‐Sophie Tabaud, Martin Racek
In this contribution, we highlight the importance of in‐situ monazite geochronology linked to P−T modelling for identification of timescales of metamorphic processes. Barrovian‐type micaschists, migmatites and augengneiss from the Gumburanjun dome in the southeastern extremity of the Gianbul dome, NW Himalaya, have been studied in order to correlate the early stages of Himalayan metamorphism at different
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Iterative thermodynamic modelling—Part 1: A theoretical scoring technique and a computer program (Bingo‐Antidote) J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-06-09 Erik Duesterhoeft, Pierre Lanari
This paper introduces the software solution Bingo‐Antidote for thermodynamic calculations at equilibrium based on iterative thermodynamic models. It describes a hybrid strategy combining the strength of Gibbs energy minimization (GEM) and inverse thermobarometry models based on the comparison between the modelled and observed mineral assemblage, modes and compositions. The overall technique relies
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High‐P (P = 1.5–1.8 GPa) blueschist from Elba: Implications for underthrusting and exhumation of continental units in the Northern Apennines J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-05-12 Samuele Papeschi, Giovanni Musumeci, Hans‐Joachim Massonne, Francesco Mazzarini, Eric James Ryan, Giulio Viola
The Acquadolce Subunit on the Island of Elba, Italy, records blueschist facies metamorphism related to the Oligocene–early Miocene stages of continental collision in the Northern Apennines. The blueschist facies metamorphism is represented by glaucophane‐ and lawsonite‐bearing metabasite associated with marble and calcschist. These rock types occur as lenses in a schistose complex representing foredeep
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High‐P granulites of the Songshugou area (Qinling Orogen, east‐central China): Petrography, phase relations, and U/Pb zircon geochronology J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-04-12 Thomas Bader, Lifei Zhang, Xiaowei Li, Bin Xia, Leander Franz, Christian de Capitani, Qingyun Li
High‐pressure (HP) granulites provide telling records of mineral reactions at upper mantle to lower crustal levels and key information on the fate of material in subduction systems. The latter especially applies when they abut eclogite and mantle dunite because such rock associations are crucial for understanding the incompletely known processes at the interface of converging plates. A continental
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Cold subduction zone in northern Calabria (Italy) revealed by lawsonite–clinopyroxene blueschists J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-04-08 Fabrizio Tursi, Caterina Bianco, Andrea Brogi, Alfredo Caggianelli, Giacomo Prosser, Giovanni Ruggieri, Eleonora Braschi
Lawsonite blueschists are important markers of cold subduction zones, subjected to intense fluid circulation. This is because lawsonite preservation in exhumed blueschists and eclogites is typically linked to cold exhumation paths, accompanied by hydration. In the Catena Costiera (Calabria, southern Italy), lawsonite–clinopyroxene blueschists of the Diamante–Terranova Unit, affected by ductile shearing
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Deciphering late Devonian–early Carboniferous P–T–t path of mylonitized garnet‐mica schists from Prins Karls Forland, Svalbard J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-04-06 Karolina Kośmińska, Frank S. Spear, Jarosław Majka, Karol Faehnrich, Maciej Manecki, Karsten Piepjohn, Winfried K. Dallmann
Quartz‐in‐garnet inclusion barometry integrated with trace element thermometry and calculated phase relations is applied to mylonitized schists of the Pinkie unit cropping out on the island of Prins Karls Forland, western part of the Svalbard Archipelago. This approach combines conventional and novel techniques and allows deciphering of the pressure–temperature (P–T) evolution of mylonitic rocks, for
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P–T–t evolution of the Cycladic Blueschist Unit in Western Anatolia/Turkey: Geodynamic implications for the Aegean region J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-03-12 Mete Çetinkaplan, Osman Candan, Roland Oberhänsli, Masafumi Sudo, Bénédicte Cenki‐Tok
Eclogite and blueschist facies rocks occurring as a tectonic unit between the underlying Menderes Massif (MM) and the overlying Afyon Zone/Lycian Nappes and the Bornova Flysch Zone in western Anatolia represent the eastward continuation of the Cycladic Blueschist Unit (CBU) in Turkey. This high‐P unit is attributed to the closure of the Pindos Ocean and consists of (a) a Triassic to Upper Cretaceous
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Metamorphic P‒T paths and Zircon U–Pb ages of Archean ultra‐high temperature paragneisses from the Qian’an gneiss dome, East Hebei terrane, North China Craton J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-03-04 Ting Liu, Chunjing Wei
The East Hebei terrane of North China Craton is characterized by the dome‐and‐keel structure, a common feature in most Archean cratons, where supracrustal rocks of granulite facies commonly occur as enclaves or rafts in tonalite–trondhjemite–granodiorite (TTG) gneisses. The metamorphic P–T paths of the granulites are significant for addressing the Archean tectonic regimes. Two types of granulite facies
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Paleoproterozoic UHT metamorphism with isobaric cooling (IBC) followed by decompression–heating in the Khondalite Belt (North China Craton): New evidence from two sapphirine formation processes J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-02-19 Shujuan Jiao, Jinghui Guo
Interpretation of reaction microstructures may provide constraints on the P–T path followed by rocks, with implications for the geodynamic evolution. Sapphirine generally occurs in diverse microstructures in ultrahigh‐temperature (UHT) Mg–Al‐rich granulites. Understanding multi‐stage sapphirine formation processes and the resultant P–T path may provide insights into the cause of UHT metamorphism, which
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Deep crustal source of gneiss dome revealed by eclogite in migmatite (Montagne Noire, French Massif Central) J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-02-19 Donna L. Whitney, Clémentine Hamelin, Christian Teyssier, Natalie H. Raia, Megan S. Korchinski, Nicholas C. A. Seaton, Brian C. Bagley, Anette von der Handt, Françoise Roger, Patrice F. Rey
In orogens worldwide and throughout geologic time, large volumes of deep continental crust have been exhumed in domal structures. Extension‐driven ascent of bodies of deep, hot crust is a very efficient mechanism for rapid heat and mass transfer from deep to shallow crustal levels and is therefore an important mechanism in the evolution of continents. The dominant rock type in exhumed domes is quartzofeldspathic
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Granulites record the tectonic evolution from collisional thickening to extensional thinning of the Tongbai orogen in central China J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-02-16 Qiang‐Qiang Zhang, Xiao‐Ying Gao, Ren‐Xu Chen, Yong‐Fei Zheng
A combined study of petrology and geochemistry was carried out for granulites from the Tongbai orogen in central China. The results reveal the tectonic evolution from collisional thickening to extensional thinning of the lithosphere at the convergent plate boundary. Petrographic observations, zircon U–Pb dating, and pseudosection calculations indicate that the granulites underwent four metamorphic
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Cryptic metasomatic agent measured in situ in Variscan mantle rocks: Melt inclusions in garnet of eclogite, Granulitgebirge, Germany J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-02-04 Alessia Borghini, Silvio Ferrero, Patrick J. O’Brien, Oscar Laurent, Christina Günter, Martin A. Ziemann
Garnet of eclogite (formerly termed garnet clinopyroxenite) hosted in lenses of orogenic garnet peridotite from the Granulitgebirge, NW Bohemian Massif, contains unique inclusions of granitic melt, now either glassy or crystallized. Analysed glasses and re‐homogenized inclusions are hydrous, peraluminous, and enriched in highly incompatible elements characteristic of the continental crust such as Cs
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Complete metamorphic cycle and long‐lived anatexis in the c. 2.1 Ga Mistinibi Complex, Canada J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-01-23 Antoine Godet, Carl Guilmette, Loic Labrousse, Donald W. Davis, Matthijs A. Smit, Jamie A. Cutts, Marc‐Antoine Vanier, Isabelle Lafrance, Benoit Charette
Secular changes in the architecture, thermal state, and metamorphic style of global orogens are thought to have occurred since the Archean; however, despite widespread research, the driving mechanisms for such changes remain unclear. The Paleoproterozoic may prove to be a key era for investigating secular changes in global orogens, as it marks the earliest stage of an eon that saw the onset of modern‐style
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Pre‐orogenic upper crustal softening by lower greenschist facies metamorphic reactions in granites of the central Pyrenees J. Metamorph. Geol. (IF 4.046) Pub Date : 2020-01-07 Laura Airaghi, Nicolas Bellahsen, Benoît Dubacq, David Chew, Claudio Rosenberg, Emilie Janots, Maxime Waldner, Valérie Magnin
Pre‐kinematic greenschist facies metamorphism is often observed in granites and basement units of mountain belts, but rarely dated and accounted for in orogenic cycle reconstructions. Studying pre‐kinematic alteration is challenging because of its usual obliteration by subsequent syn‐kinematic metamorphism often occurring at conditions typical of the brittle–ductile transition. It is, however, to be
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Subduction and accumulation of lawsonite eclogite and garnet blueschist in eastern Australia J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-12-11 Renée Tamblyn, Martin Hand, David Kelsey, Robert Anczkiewicz, David Och
Lawsonite eclogite and garnet blueschist occur as metre‐scale blocks within serpentinite mélange in the southern New England Orogen (SNEO) in eastern Australia. These high‐P fragments are the products of early Palaeozoic subduction of the palaeo‐Pacific plate beneath East Gondwana. Lu–Hf, Sm–Nd, and U–Pb geochronological data from Port Macquarie show that eclogite mineral assemblages formed between
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Evidence for UHP anatexis in the Shuanghe UHP paragneiss from inclusions in clinozoisite, garnet, and zircon J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-12-05 Qiang Liu, Jörg Hermann, Shu Zheng, Junfeng Zhang
The Shuanghe garnet‐bearing paragneiss from the Dabie ultra‐high–pressure (UHP) orogen occurs as an interlayer within partially retrogressed eclogite. A first UHP metamorphic stage at 680°C, 3.8–4.1 GPa is documented by Zr‐in‐rutile temperatures coupled with phengite inclusions (Si = 3.55) in clinozoisite and grossular‐rich garnet. Relic matrix phengite and phengite inclusions in zircon rims display
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Microstructurally controlled trace element (Zr, U–Pb) concentrations in metamorphic rutile: An example from the amphibolites of the Bergen Arcs J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-11-25 Jo Moore, Andreas Beinlich, Jennifer K. Porter, Cristina Talavera, Jasper Berndt, Sandra Piazolo, Håkon Austrheim, Andrew Putnis
As a common constituent of metamorphic assemblages, rutile provides constraints on the timing and conditions of rock transformation at high resolution. However, very little is known about the links between trace element mobility and rutile microstructures that result from synmetamorphic deformation. To address this issue, here we combine in situ LA‐ICP‐MS and sensitive high‐resolution ion microprobe
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Mineral assemblages and phase equilibria of metabasites from the prehnite–pumpellyite to amphibolite facies, with the Flin Flon Greenstone Belt (Manitoba) as a type example J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-11-20 Paul G. Starr, David R. M. Pattison, Doreen E. Ames
An exceptionally well‐exposed part of the Flin Flon Greenstone Belt (Manitoba/Saskatchewan) is used to characterize the mineral assemblage evolution associated with prehnite–pumpellyite through amphibolite facies metamorphism of basalts. Data from these rocks are combined with a large literature data set to assess the ability of current thermodynamic models to reproduce natural patterns, evaluate the
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Calibration of oxygen isotope fractionation and calcite‐corundum thermometry in emery at Naxos, Greece J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-11-12 Rachelle B. Turnier, Yaron Katzir, Kouki Kitajima, Ian J. Orland, Michael J. Spicuzza, John W. Valley
Corundum (Crn), including sapphire, occurs in emery pods surrounded by marble on the island of Naxos, Greece. The emery formed from bauxite deposited in karst that was metamorphosed to 400–700°C at 20–15 Ma. Many of these rocks initially appeared well suited for refractory accessory mineral (RAM) thermometry, which uses oxygen isotope fractionation between a RAM – corundum – and a modally dominant
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Muscovite dehydration melting: Reaction mechanisms, microstructures, and implications for anatexis J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-10-30 Brendan Dyck, David J. Waters, Marc R. St‐Onge, Mike P. Searle
Dehydration melting of muscovite in metasedimentary sequences is the initially dominant mechanism of granitic melt generation in orogenic hinterlands. In dry (vapour‐absent) crust, muscovite reacts with quartz to produce K‐feldspar, sillimanite, and monzogranitic melt. When water vapour is present in excess, sillimanite and melt are the primary products of muscovite breakdown, and any K‐feldspar produced
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Diachronic metamorphic and structural evolution of the Connecticut Valley–Gaspé trough, Northern Appalachians J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-10-21 Morgann Perrot, Alain Tremblay, Gilles Ruffet, Loic Labrousse, Félix Gervais, Fabien Caroir
The Connecticut Valley–Gaspé (CVG) trough represents a major, orogen‐scale Silurian–Devonian basin of the Northern Appalachians. From Gaspé Peninsula to southern New England, the CVG trough has experienced a contrasting metamorphic and structural evolution during the Acadian orogeny. Along its strike, the CVG trough is characterized by increasing strain and polyphase structures, and by variations in
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Polymetamorphism in high‐T metamorphic rocks: An example from the central Appalachians J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-10-06 Kirkland S. Broadwell, Mark J. Caddick, James S. Beard
Contact metamorphism associated with mafic intrusives is one of several mechanisms that has been invoked to produce extensive high‐temperature (HT) metamorphism and associated partial melting of the crust. Indisputable evidence for polymetamorphism in these settings can be difficult to decipher because both melt loss and retrogression (i.e. rehydration) can erase or obscure the records of earlier HT
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The significance of Mn‐rich ilmenite and the determination of P–T paths from zoned garnet in metasedimentary rocks from the western Cape Breton Highlands, Nova Scotia J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-10-01 Travis McCarron, Christopher R. M. McFarlane, Fred Gaidies
The Jumping Brook Metamorphic Suite in the western Cape Breton Highlands of Nova Scotia is part of an inverted Barrovian sequence that formed during a Late Silurian–Early Devonian promontory–promontory collision in the Canadian Appalachians. In this study, systematic discrepancies between geochemical observations and thermodynamic model predictions led to the discovery of a systematic relationship
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Quartz‐in‐garnet and Ti‐in‐quartz thermobarometry: Methodology and first application to a quartzofeldspathic gneiss from eastern Papua New Guinea J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-09-08 Joseph P. Gonzalez, Jay B. Thomas, Suzanne L. Baldwin, Matteo Alvaro
Mineral inclusions are ubiquitous in metamorphic rocks and elastic models for host‐inclusion pairs have become frequently used tools for investigating pressure–temperature (P–T) conditions of mineral entrapment. Inclusions can retain remnant pressures () that are relatable to their entrapment P–T conditions using an isotropic elastic model and P–T–V equations of state for host and inclusion minerals
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Decoding the complex internal chemical structure of garnet porphyroblasts from the Zermatt area, Western Alps J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-09-04 Kurt Bucher, Tobias Björn Weisenberger, Oliver Klemm, Sebastian Weber
Garnet is a prototypical mineral in metamorphic rocks because it commonly preserves chemical and textural features that can be used for untangling its metamorphic development. Large garnet porphyroblasts may show extremely complex internal structures as a result of a polycyclic growth history, deformation, and modification of growth structures by intra‐ and intercrystalline diffusion. The complex internal
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On the petrology of brittle precursors of shear zones – An expression of concomitant brittle deformation and fluid–rock interactions in the ‘ductile’ continental crust? J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-07-25 Thomas Leydier, Philippe Goncalves, Pierre Lanari, Emilien Oliot
The inherited localization model for shear zone development suggests that ductile deformation in the middle and lower continental crust is localized on mechanical anisotropies, like fractures, referred to as shear zone brittle precursors. In the Neves area (Western Tauern Window, Eastern Alps), although the structural control of these brittle precursors on ductile strain localization is well established
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Migmatites record multiple episodes of crustal anatexis and geochemical differentiation in the Sulu ultrahigh‐pressure metamorphic zone, eastern China J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-06-28 Kun Zhou, Yi‐Xiang Chen, Yong‐Fei Zheng, Li‐Juan Xu
Partial melting of ultrahigh‐pressure (UHP) metamorphic rocks is common during collisional orogenesis and post‐collisional reworking, indicating that determining the timing and processes involved in this partial melting can provide insights into the tectonic evolution of collisional orogens. This study presents the results of a combined whole‐rock geochemical and zirconological study of migmatites
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Seemingly disparate temperatures recorded in coexisting granulite facies lithologies J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-06-26 Simon Schorn, Johann F.A. Diener
Phase equilibrium modelling of a conformable sequence of supracristal lithologies from the Bushmanland Subprovince of the Namaqua–Natal Metamorphic Complex (South Africa) reveals a disparity of some 60–70°C in estimated peak metamorphic temperature. Aluminous metapelites were equilibrated at ~770–790°C, whereas two‐pyroxene granulite and garnet–orthopyroxene–biotite gneiss record distinctly higher
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Rutile inclusions in garnet from a dissolution‐reprecipitation mechanism J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-06-25 Shyh‐Lung Hwang, Pouyan Shen, Hao‐Tsu Chu, Tzen‐Fu Yui, Yoshiyuki Iizuka, Hans‐Peter Schertl
Metamorphic garnet commonly contains needle‐like rutile inclusions as well as equant rutile inclusions that surround quartz inclusions and range in size from submicrometer to nanometer. Although the origin of these equant rutile inclusions, that is, exsolution or non‐exsolution, has important implications for petrological and tectonic processes, the crystallographic characteristics of these inclusions
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Petrochronology of oxidized granulites from southern Peru J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-06-14 Chris Yakymchuk, Adrian Rehm, Zhuoheng Liao, John M. Cottle
Sapphirine–quartz granulites from the Cocachacra region of the Arequipa Massif in southern Peru record early Neoproterozoic ultrahigh‐temperature metamorphism. Phase equilibrium modelling and zircon petrochronology are used to quantify timing and pressure–temperature (P–T) conditions of metamorphism. Modelling of three magnetite‐bearing sapphirine–quartz samples indicates peak temperatures of >950°C
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Oxygen isotope speedometry in granulite facies garnet recording fluid/melt–rock interaction (Sør Rondane Mountains, East Antarctica) J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-06-06 Fumiko Higashino, Daniela Rubatto, Tetsuo Kawakami, Anne‐Sophie Bouvier, Lukas P. Baumgartner
In situ analysis of a garnet porphyroblast from a granulite facies gneiss from Sør Rondane Mountains, East Antarctica, reveals discontinuous step‐wise zoning in phosphorus and large δ18O variations from the phosphorus‐rich core to the phosphorus‐poor rim. The gradually decreasing profile of oxygen isotope from the core (δ18O = ~15‰) to the rim (δ18O = ~11‰) suggests that the 18O/16O zoning was originally
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The field and microstructural signatures of deformation‐assisted melt transfer: Insights from magmatic arc lower crust, New Zealand J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-05-29 Uvana Meek, Sandra Piazolo, Nathan R. Daczko
Melt must transfer through the lower crust, yet the field signatures and mechanisms involved in such transfer zones (excluding dykes) are still poorly understood. We report field and microstructural evidence of a deformation‐assisted melt transfer zone that developed in the lower crustal magmatic arc environment of Fiordland, New Zealand. A 30–40 m wide hornblende‐rich body comprising hornblende ± clinozoisite
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Titanite dates crystallization: Slow Pb diffusion during super‐solidus re‐equilibration J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-05-29 Michael I. H. Hartnady, Christopher L. Kirkland, Chris Clark, Catherine V. Spaggiari, R. Hugh Smithies, Noreen J. Evans, Brad J. McDonald
Titanite can be found in rocks of wide compositional range, is reactive, growing or regrowing during metamorphic and hydrothermal events, and is generally amenable to U–Pb geochronology. Experimental evidence suggest that titanite has a closure temperature for Pb ranging from 550 to 650°C, and thus titanite dates are commonly interpreted as cooling ages. However, this view has been challenged in recent
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Two‐stage Variscan metamorphism in the Canigou massif: Evidence for crustal thickening in the Pyrenees J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-05-14 Luc de Hoÿm de Marien, Benjamin Le Bayon, Pavel Pitra, Jean Van Den Driessche, Marc Poujol, Florence Cagnard
The Variscan metamorphism in the Pyrenees is dominantly of the low‐pressure–high‐temperature (LP‐HT) type. The relics of an earlier, Barrovian‐type metamorphism that could be related to orogenic crustal thickening are unclear and insufficiently constrained. A microstructural and petrological study of micaschists underlying an Ordovician augen orthogneiss in the core of the Canigou massif (Eastern Pyrenees
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Testing the fidelity of thermometers at ultrahigh temperatures J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-05-08 Chris Clark, Richard J. M. Taylor, Tim E. Johnson, Simon L. Harley, Ian C. W. Fitzsimons, Liam Oliver
A highly residual granulite facies rock (sample RG07‐21) from Lunnyj Island in the Rauer Group, East Antarctica, presents an opportunity to compare different approaches to constraining peak temperature in high‐grade metamorphic rocks. Sample RG07‐21 is a coarse‐grained pelitic migmatite composed of abundant garnet and orthopyroxene along with quartz, biotite, cordierite, and plagioclase with accessory
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The truth and beauty of chemical potentials J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-05-02 R. Powell, K. A. Evans, E. C. R. Green, R. W. White
This essay in honour of Mike Brown addresses aspects of chemical equilibrium and equilibration in rocks, with a focus on the role that chemical potentials play. Chemical equilibrium is achieved by diffusive flattening of chemical potential gradients. The idea of equilibration volume is developed, and the way equilibration volumes may evolve along a pressure–temperature path is discussed. The effect
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Slow cooling versus episodic fluid injections: Deciphering the Caledonian orogeny in Vestvågøy, Lofoten islands, Norway J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-04-26 Herbert W. Fournier, James K. W. Lee, Alfredo Camacho
The determination of the thermal (temperature–time) histories of high‐P metamorphic terranes has been commonly based on the concepts of slow cooling and closure temperatures. In this paper, we find that this approach cannot reconcile a geochronological data set obtained from the amphibolite‐facies allochthonous Leknes Group of the Lofoten islands, Norway, which reveals an extremely complex thermal
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Mesozoic to Cenozoic tectono‐metamorphic history of the South Pamir–Hindu Kush (Chitral, NW Pakistan): Insights from phase equilibria modelling, and garnet–monazite petrochronology J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-04-25 Mathieu Soret, Kyle P. Larson, John M. Cottle, Matthijs Smit, Alex Johnson, Sudip Shrestha, Asghar Ali, Shah Faisal
The Karakoram–Hindu Kush–Pamir and adjacent Tibetan plateau belt comprise a series of Gondwana‐derived crustal fragments that successively accreted to the Eurasian margin in the Mesozoic as the result of the progressive Tethys ocean closure. These domains provide unique insights into the thermal and structural history of the Mesozoic to Cenozoic Eurasian plate margin, which are critical to inform the
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Subduction metamorphism of serpentinite‐hosted carbonates beyond antigorite‐serpentinite dehydration (Nevado‐Filábride Complex, Spain) J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-04-12 Manuel D. Menzel, Carlos J. Garrido, Vicente López Sánchez‐Vizcaíno, Károly Hidas, Claudio Marchesi
At sub‐arc depths, the release of carbon from subducting slab lithologies is mostly controlled by fluid released by devolatilization reactions such as dehydration of antigorite (Atg‐) serpentinite to prograde peridotite. Here we investigate carbonate–silicate rocks hosted in Atg‐serpentinite and prograde chlorite (Chl‐) harzburgite in the Milagrosa and Almirez ultramafic massifs of the palaeo‐subducted
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Ultrahigh‐pressure and high‐P lawsonite eclogites in Muzhaerte, Chinese western Tianshan J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-04-12 Zeng Lü, Lifei Zhang, Ji Yue, Xiaoli Li
Lawsonite eclogites are crucial to decipher material recycling along a cold geotherm into the deep Earth and orogenic geodynamics at convergent margins. However, their tectono‐metamorphic role and record especially at ultrahigh‐pressure (UHP) conditions are poorly known due to rare exposure in orogenic belts. In a ~4 km long cross‐section in Muzhaerte, China, at the western termination of the HP‐UHP
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A revised petrological model for subducted oceanic crust: Insights from phase equilibrium modelling J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-04-12 David Hernández‐Uribe, Richard M. Palin
Many geological and geodynamical studies of metamorphism in subduction zones have relied upon worldwide compilations of modelled slab‐top pressure–temperature (P–T) conditions, although recent evaluation of such data sets suggests that these predictions are ~100–300°C colder at any given pressure than the conditions recorded by exhumed metamorphic rocks. As such, geochemical, petrological and geophysical
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Closed system behaviour of argon in osumilite records protracted high‐T metamorphism within the Rogaland–Vest Agder Sector, Norway J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-04-11 Eleanore Blereau, Chris Clark, Fred Jourdan, Tim E. Johnson, Richard J. M. Taylor, Peter D. Kinny, Martin Danišík, Martin Hand, Ela Eroglu
Here, we present results of the first 40Ar/39Ar dating of osumilite, a high‐T mineral that occurs in some volcanic and high‐grade metamorphic rocks. The metamorphic osumilite studied here is from a metapelitic rock within the Rogaland–Vest Agder Sector, Norway, an area that experienced regional granulite facies metamorphism and subsequent contact metamorphism between 1,100 Ma and 850 Ma. The large
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The timing of migmatization in the northern Arabian–Nubian Shield: Evidence for a juvenile sedimentary component in collision‐related batholiths J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-03-28 Bar Elisha, Yaron Katzir, Andrew R. C. Kylander‐Clark, Tzahi Golan, Matthew A. Coble
Collision‐related granitoid batholiths, like those of the Hercynian and Himalayan orogens, are mostly fed by magma derived from metasedimentary sources. However, in the late Neoproterozoic calcalkaline (CA) batholiths of the Arabian–Nubian Shield (ANS), which constitutes the northern half of the East African orogen, any sedimentary contribution is obscured by the juvenile character of the crust and
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Integrated garnet and zircon–titanite geochronology constrains the evolution of ultra‐high–pressure terranes: An example from the Sulu orogen J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-03-25 Da Wang, Jeffrey D. Vervoort, Christopher M. Fisher, Hui Cao, Guangxu Li
Dating ultra‐high–pressure (UHP) metamorphic rocks provides important timing constraints on deep subduction zone processes. Eclogites, deeply subducted rocks now exposed at the surface, undergo a wide range of metamorphic conditions (i.e. deep subduction and exhumation) and their mineralogy can preserve a detailed record of chronologic information of these dynamic processes. Here, we present an approach
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P–T evolution and episodic zircon growth in barroisite eclogites of the Lanterman Range, northern Victoria Land, Antarctica J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-03-21 Taehwan Kim, Yoonsup Kim, Moonsup Cho, Jong Ik Lee
Prograde P–T–t paths of eclogites are often ambiguous owing to high variance of mineral assemblages, large uncertainty in isotopic age determinations and/or variable degree of retrograde equilibration. We investigated these issues using the barroisite eclogites from the Lanterman Range, northern Victoria Land, Antarctica, which are relatively uncommon but free of retrogression. These eclogites revealed
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A paired metamorphic belt in a subduction‐to‐collision orogen: An example from the South Qilian–North Qaidam orogenic belt, NW China J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-03-21 Xiucai Li, Manlan Niu, Chris Yakymchuk, Qi Wu, Changlei Fu
The early Palaeozoic South Qilian–North Qaidam orogenic belt in northwestern China records a nearly complete history of early‐stage long‐lived oceanic subduction–accretion followed by late‐stage continental collision. Most previous studies have focused on low dT/dP metamorphism (HP–UHP) in this belt whereas the paired high dT/dP belt in the hinterland has received little attention. In this contribution
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Phase equilibrium modelling of the amphibolite to granulite facies transition in metabasic rocks (Ivrea Zone, NW Italy) J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-03-19 Barbara E. Kunz, Richard W. White
The development of thermodynamic models for tonalitic melt and the updated clinopyroxene and amphibole models now allow the use of phase equilibrium modelling to estimate P–T conditions and melt production for anatectic mafic and intermediate rock types at high‐T conditions. The Permian mid‐lower crustal section of the Ivrea Zone preserves a metamorphic field gradient from mid amphibolite facies to
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Grain‐scale dependency of metamorphic reaction on crystal plastic strain J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-03-19 Timothy Chapman, Geoffrey L. Clarke, Sandra Piazolo, Victoria A. Robbins, Patrick W. Trimby
The Breaksea Orthogneiss in Fiordland, New Zealand preserves water‐poor intermediate and mafic igneous rocks that were partially recrystallized to omphacite granulite and eclogite, respectively, at P ≈ 1.8 GPa and T ≈ 850°C. Metamorphic reaction consumed plagioclase and produced grossular‐rich garnet, jadeite‐rich omphacite, clinozoisite and kyanite. The extent of metamorphic reaction, identified by
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An anticlockwise P–T–t path at high‐pressure, high‐temperature conditions for a migmatitic gneiss from the island of Fjørtoft, Western Gneiss Region, Norway, indicates two burial events during the Caledonian orogeny J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-03-19 Penglei Liu, Hans‐Joachim Massonne
The Blåhø Nappe on the island of Fjørtoft, which represents an isolated portion of the Seve Nappe Complex in the Western Gneiss Region, Norway, has been suggested to have experienced two deep burial cycles during the Caledonian orogeny. However, evidence on this multiple burial process by the derivation of a pressure–temperature–time (P–T–t) path has never been given in the literature. In this study
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Microstructure and compositional changes across biotite‐rich reaction selvedges around mafic schollen in a semipelitic diatexite migmatite J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-03-19 Lina Lin, Edward W. Sawyer
Biotite‐rich selvedges developed between mafic schollen and semipelitic diatexite in migmatites at Lac Kénogami in the Grenville Province of Quebec. Mineral equilibria modelling indicates that partial melting occurred in the mid‐crust (4.8–5.8 kbar) in the range 820–850°C. The field relations, petrography, mineral chemistry and whole‐rock composition of selvedges along with their adjacent mafic schollen
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Monazite as a monitor for melt‐rock interaction during cooling and exhumation J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-02-15 Alexander M. Prent, Andreas Beinlich, Laura J. Morrissey, Tom Raimondo, Chris Clark, Andrew Putnis
Granulite facies cordierite–garnet–biotite gneisses from the southeastern Reynolds Range, central Australia, contain both orthopyroxene‐bearing and orthopyroxene‐free quartzofeldspathic leucosomes. Mineral reaction microstructures at the interface of gneiss and leucosome observed in outcrop and petrographically, reflect melt‐rock interaction during crystallization. Accessory monazite, susceptible to
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Divergent behaviour of Th and U during anatexis: Implications for the thermal evolution of orogenic crust J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-02-07 Chris Yakymchuk, Michael Brown
Mobilization and migration of the heat‐producing elements (HPE) during anatexis is a critical process in the development of orogenic systems, the evolution of continental crust and the stabilization of cratons. In many crustal rocks the accessory minerals are the dominant hosts of Th and U, and the behaviour of these minerals during partial melting controls the concentrations of these elements in draining
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Preservation of high‐P rocks coupled to rock composition and the absence of metamorphic fluids J. Metamorph. Geol. (IF 4.046) Pub Date : 2019-02-07 Alasdair Skelton, Alexandre Peillod, Johannes Glodny, Iwona Klonowska, Carolina Månbro, Karin Lodin, Uwe Ring
Eclogites, blueschists and greenschists are found in close proximity to one another along a 1‐km coastal section where the Cyclades Blueschist Unit (CBU) is exposed on SE Syros, Greece. Here, we show that the eclogites and blueschists experienced the same metamorphic history: prograde lawsonite blueschist facies metamorphism at 1.2–1.9 GPa and 410–530°C followed, at 43–38 Ma, by peak blueschist/eclogite
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