High‐and Ultrahigh‐Pressure Rocks

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Deposits".

Deadline for manuscript submissions: closed (15 December 2019) | Viewed by 19203

Special Issue Editors


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Guest Editor
1. Department of Earth Sciences, Uppsala University, 752 36 Uppsala, Sweden
2. Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, 30-059 Kraków, Poland
Interests: collisional orogens; metamorphic petrology; metasomatism; exhumation mechanisms of HP-UHP terranes

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Guest Editor
Faculty of Geology, Geophysics and Environmental Protection, AGH University of Science and Technology, 30-059 Kraków, Poland
Interests: petrochronology; diamond formation; deep subduction

Special Issue Information

Dear Colleagues,

We invite you to submit contributions on high- and ultrahigh-pressure (HP-UHP) rocks. These rocks record processes of deep subduction of the oceanic and continental crust. Direct observation of the geological phenomena occurring at mantle depths in subduction–collision zones is basically impossible. However, understanding the interaction of the Earth’s crust and mantle resulting from plate movements, in particular in the deep subduction environment, is crucial for further understanding of convergent plate boundary dynamics. Enhancing our knowledge of the equilibration of rocks (or lack of) during subduction–exhumation cycle(s), the exchange of energy and mass during such cycles between crust and mantle, the deformation of subducted slabs, tectonic processes associated with HP/UHP metamorphism and seismometamorphism is of great value for advanced understanding of the Earth’s dynamics. Therefore, we welcome both original and review papers concerning (but not limited to) following aspects: (i) pressure–temperature–time–deformation evolutionary paths of HP-UHP lithologies; (ii) rates of metamorphic processes in HP-UHP rocks; (iii) tectonic phenomena leading to the burial and exhumation of deeply subducted rocks; (iv) crust–mantle interaction and deep element recycling; as well as (v) triggering mechanisms for intermediate depth seismicity.

This Special Issue is organized together with the 13th International Eclogite Conference (IEC) (Petrozavodsk, Karelia, Russia, 24–27 June 2019), hence participants of the IEC are especially welcome to submit their contributions. However, all other authors are also welcome to contribute to this issue.

Prof. Dr. Jaroslaw Majka
Dr. Iwona Klonowska
Guest Editors

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Keywords

  • Eclogite
  • Blueschist
  • Subduction
  • Exhumation
  • HP/UHP metamorphism
  • Thermobarometry
  • Chronometry
  • Element recycling
  • Earthquake
  • Geodynamic evolution

Published Papers (5 papers)

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Research

26 pages, 10069 KiB  
Article
Water Content in Garnet from Eclogites: Implications for Water Cycle in Subduction Channels
by Yiren Gou, Qin Wang, Yan Li and Richard Wirth
Minerals 2020, 10(5), 410; https://doi.org/10.3390/min10050410 - 30 Apr 2020
Cited by 3 | Viewed by 3072
Abstract
Garnet from eclogites often shows very heterogenous and extremely high hydroxyl concentration. Eight eclogite samples were selected from the Sulu ultrahigh-pressure terrane and the Sumdo high-pressure metamorphic belt (Lhasa). The mean hydroxyl concentration in pyrope-rich and almandine-rich garnet varies from 54 to 427 [...] Read more.
Garnet from eclogites often shows very heterogenous and extremely high hydroxyl concentration. Eight eclogite samples were selected from the Sulu ultrahigh-pressure terrane and the Sumdo high-pressure metamorphic belt (Lhasa). The mean hydroxyl concentration in pyrope-rich and almandine-rich garnet varies from 54 to 427 ppm H2O and increases with the retrogression degree of eclogites. TEM observations reveal nanometer-sized anthophyllite exsolutions and clinochlore inclusions in water-rich domains in garnet, where anthophyllite is partly replaced by clinochlore. Because of overlapping of the infrared stretching absorption bands for structural OH in garnet and chlorite, it is impossible to exclude contribution of chlorite inclusions to the estimated hydroxyl concentration in garnet. The broad band near 3400 cm−1 is attributed to molecular water and nanometer-sized chlorite inclusions. Anthophyllite exsolutions may be formed by decomposition of hydrous garnet from ultrahigh-pressure eclogites during exhumation. Significant amounts of water can be stored in garnet from massif eclogites in the forms of hydroxyl in garnet and nanometer-sized inclusions of anthophyllite and clinochlore, as well as fluid inclusions. Amphibolite facies retrograde metamorphism can significantly increase both hydroxyl concentration and water heterogeneity in garnet from massif eclogites. These nano-inclusions in garnet provide a window to trace the water cycle in subduction channels. Full article
(This article belongs to the Special Issue High‐and Ultrahigh‐Pressure Rocks)
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24 pages, 14585 KiB  
Article
U-Pb Zircon Dating of Migmatitic Paragneisses and Garnet Amphibolite from the High Pressure Seve Nappe Complex in Kittelfjäll, Swedish Caledonides
by Michał Bukała, Jarosław Majka, Katarzyna Walczak, Adam Włodek, Melanie Schmitt and Anna Zagórska
Minerals 2020, 10(4), 295; https://doi.org/10.3390/min10040295 - 25 Mar 2020
Cited by 8 | Viewed by 3227
Abstract
The Seve Nappe Complex exposed in the Kittelfjäll area of the northern Scandinavian Caledonides comprises a volcano-sedimentary succession representing the Baltica passive margin, which was metamorphosed during the Iapetus Ocean closure. Garnet amphibolites, together with their host migmatitic paragneisses, record a potential (U)HP [...] Read more.
The Seve Nappe Complex exposed in the Kittelfjäll area of the northern Scandinavian Caledonides comprises a volcano-sedimentary succession representing the Baltica passive margin, which was metamorphosed during the Iapetus Ocean closure. Garnet amphibolites, together with their host migmatitic paragneisses, record a potential (U)HP event followed by decompression-driven migmatization. The garnet amphibolites were originally thought to represent retrogressively altered granulites. The petrological and geochemical features of a studied garnet amphibolite allow for speculation about a peridotitic origin. Zirconium (Zr) content in rutile inclusions hosted in garnet in paragneisses points to near-peak temperatures between 738 °C and 780 °C, which is in agreement with the c. 774 °C obtained from the matrix rutile in the garnet amphibolite. The matrix rutile in multiple paragneiss samples records temperatures below 655 °C and 726 °C. Whereas the LA-ICP-MS U-Pb dating of zircon cores revealed the age spectrum from Paleoproterozoic to early Paleozoic, suggesting a detrital origin of zircon cores in paragneisses, the metamorphic zircon rims show an Early Ordovician cluster c. 475–469 Ma. Additionally, zircon cores and rims from the garnet amphibolite yielded an age of c. 473 Ma. The REE patterns of the Caledonian zircon rims from the paragneisses show overall low LREE concentrations, different from declining to rising trends in HREE (LuN/GdN = 0.49–38.76). Despite the textural differences, the cores and rims in zircon from the garnet amphibolite show similar REE patterns of low LREE and flat to rising HREE (LuN/GdN = 3.96–65.13). All zircon rims in both lithologies display a negative Eu anomaly. Hence, we interpret the reported ages as the growth of metamorphic zircon during migmatization, under granulite facies conditions related to exhumation from (U)HP conditions. Full article
(This article belongs to the Special Issue High‐and Ultrahigh‐Pressure Rocks)
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19 pages, 24747 KiB  
Article
Metamorphic Evolution of Garnet-Bearing Ultramafic Rocks in the Hujialin Area, Sulu Ultrahigh-Pressure Orogenic Belt, Eastern China
by Zeli Wang, Shukai Zhang, Xu-Ping Li, Songjie Wang, Dan Wang, Fan-Mei Kong, Jianguo Liu, Zengsheng Li, Dapeng Li, Jian Wang and Yongqiang Yang
Minerals 2020, 10(3), 225; https://doi.org/10.3390/min10030225 - 29 Feb 2020
Cited by 1 | Viewed by 3360
Abstract
The Rizhao Hujialin area is located in the central Sulu ultrahigh-pressure orogenic belt, where garnet clinopyroxenite is exposed in the upper part of an ultramafic rock complex and serpentinized dunite is exposed in its lower part. Based on textural criteria, the garnet clinopyroxenites [...] Read more.
The Rizhao Hujialin area is located in the central Sulu ultrahigh-pressure orogenic belt, where garnet clinopyroxenite is exposed in the upper part of an ultramafic rock complex and serpentinized dunite is exposed in its lower part. Based on textural criteria, the garnet clinopyroxenites were divided into three types: Equigranular garnet, porphyroclastic garnet, and megacrystic garnet pyroxenites. The garnet clinopyroxenites have convex-upward chondrite-normalized rare earth element patterns, large positive Pb anomalies, and depletion of high-field-strength elements (e.g., Nb, Zr, and Ti), suggesting a mantle source protolith overprinted by fluid metasomatism. Petrographic, mineral chemistry, phase equilibrium modeling, and zircon U–Pb geochronology data show that the evolutionary stages of the Hujialin garnet clinopyroxenites were as follows: Stage I: formation of the magmatic protoliths; stage II: formation of megacrystic garnet pyroxenite accompanying subduction; stage III: formation of porphyroclastic or equigranular garnet clinopyroxenite with a mineral assemblage of garnet + clinopyroxene + ilmenite + humite accompanying initial exhumation at ~215.0 ± 5.7 Ma; stage IV = progressive cooling and decompression associated with the crystallization of water-bearing minerals such as clinochlore and pargasite at 206 Ma; and Stage V = late epidote amphibolite-facies retrograde metamorphism producing a mineral assemblage of garnet + clinopyroxene + amphibole + chlorite + epidote + ilmenite at ~180–174 Ma associated with fluid activity in shear–tensional fractures and/or pores. The P-T conditions of the peak metamorphism were estimated at 4.5 ± 0.5 GPa and 800 ± 50 °C. Retrograde metamorphism recorded conditions of 1.0 GPa and 710 ± 30 °C during the exhumation and cooling process. The mineral transformation from early high-Al clinopyroxene to garnet and to late diopside records the general metamorphic evolution during subduction and exhumation, respectively. One zircon U–Pb analysis presents the Palaeoproterozoic age of 1817 ± 40 Ma, which is coeval with widespread magmatic and metamorphic events in the North China Craton. Full article
(This article belongs to the Special Issue High‐and Ultrahigh‐Pressure Rocks)
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23 pages, 8738 KiB  
Article
Timing of Paleozoic Exhumation and Deformation of the High-Pressure Vestgӧtabreen Complex at the Motalafjella Nunatak, Svalbard
by Christopher J. Barnes, Katarzyna Walczak, Emilie Janots, David Schneider and Jarosław Majka
Minerals 2020, 10(2), 125; https://doi.org/10.3390/min10020125 - 31 Jan 2020
Cited by 16 | Viewed by 2900
Abstract
The Vestgӧtabreen Complex exposed in the Southwestern Caledonian Basement Province of Svalbard comprises two Caledonian high-pressure units. In situ white mica 40Ar/39Ar and monazite Th-U-total Pb geochronology has resolved the timing of the tectonic evolution of the complex. Cooling of [...] Read more.
The Vestgӧtabreen Complex exposed in the Southwestern Caledonian Basement Province of Svalbard comprises two Caledonian high-pressure units. In situ white mica 40Ar/39Ar and monazite Th-U-total Pb geochronology has resolved the timing of the tectonic evolution of the complex. Cooling of the Upper Unit during exhumation occurred at 476 ± 2 Ma, shortly after eclogite-facies metamorphism. The two units were juxtaposed at 454 ± 6 Ma. This was followed by subaerial exposure and deposition of Bullbreen Group sediments. A 430–400 Ma late Caledonian phase of thrusting associated with major sinistral shearing throughout Svalbard deformed both the complex and the overlying sediments. This phase of thrusting is prominently recorded in the Lower Unit, and is associated with a pervasive greenschist-facies metamorphic overprint of high-pressure lithologies. A c. 365–344 Ma geochronological record may represent an Ellesmerian tectonothermal overprint. Altogether, the geochronological evolution of the Vestgӧtabreen Complex, with previous petrological and structural studies, suggests that it may be a correlative to the high-pressure Tsäkkok Lens in the Scandinavian Caledonides. It is suggested that the Vestgӧtabreen Complex escaped to the periphery of the orogen along the sinistral strike-slip shear zones prior to, or during the initial stages of continental collision between Baltica and Laurentia. Full article
(This article belongs to the Special Issue High‐and Ultrahigh‐Pressure Rocks)
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13 pages, 2826 KiB  
Article
Original Calibration of a Garnet Geobarometer in Metapelite
by Chun-Ming Wu
Minerals 2019, 9(9), 540; https://doi.org/10.3390/min9090540 - 06 Sep 2019
Cited by 38 | Viewed by 6052
Abstract
In many metapelitic assemblages, plagioclase is either CaO-deficient or even absent. In such cases, all the widely applied, well-calibrated plagioclase-related geobarometers lose their usage. Fortunately, it has been found that a net-transfer reaction including intracrystalline Fe2+–Ca2+ exchange in garnet is [...] Read more.
In many metapelitic assemblages, plagioclase is either CaO-deficient or even absent. In such cases, all the widely applied, well-calibrated plagioclase-related geobarometers lose their usage. Fortunately, it has been found that a net-transfer reaction including intracrystalline Fe2+–Ca2+ exchange in garnet is pressure-sensitive, therefore, a garnet geobarometer can be empirically calibrated under pressure–temperature (P–T) conditions of 430~895 °C and 1~15 kbar. The chemical composition range of the calibrant garnet is XCa = 0.02~0.29 and XFe = 0.42~0.91, and covers the majority of garnet in metapelite. The total error of this geobarometer was estimated to be within ±1.3 kbar. The application of this garnet geobarometer to metamorphic terranes certifies its applicability, and this geobarometer can play a unique role, especially when plagioclase is absent or CaO-deficient. Metamorphic P–T conditions can be simultaneously determined by the garnet–biotite pair through the application of the present garnet geobarometer in combination with a well-calibrated garnet-biotite geothermometer. Full article
(This article belongs to the Special Issue High‐and Ultrahigh‐Pressure Rocks)
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