Significance of Zr-in-Rutile Thermometry for Deducing the Decompression P–T Path of a Garnet–Clinopyroxene Granulite in the Moldanubian Zone of the Bohemian Massif

Usuki, Tadashi; Iizuka, Yoshiyuki; Hirajima, Tsuyoshi; Svojtka, Martin; Lee, Hao‐Yang; Jahn, Bor‐ming

doi:10.1093/petrology/egx050

Cited by 18 publications

(6 citation statements)

References 77 publications

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“…The peak P-T conditions of the Gföhl Unit have been estimated at around 1.6-2.0 GPa and 900-1100 °C (e.g., Carswell and O'Brien, 1993;Cooke and O'Brien, 2001;Usuki et al, 2017) for granulite and 2-5 GPa and 800- Beard et al, 1992). (b) Geological map of the study area (modified from Cháb et al, 2007 andJanoušek et al, 2020).…”

Section: Geological Settingmentioning

confidence: 99%

Multiple origins of UHP eclogites in a garnet peridotite block (Nové Dvory, Czech Republic) and short duration of heating

ITAMI

Nakamura

Yasumoto

et al. 2022

Journal of Mineralogical and Petrological Sciences

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The origins of eclogite associated with garnet peridotite in continent-continent collision belts are still debated. We performed petrological studies of eclogites collected from a garnet peridotite block from Nové Dvory in the Gföhl Unit of the Moldanubian Zone in the Variscan orogenic belt, Czech Republic. The eclogite was divided into three types: one kyanite (Ky)-bearing and two Ky-free types. Garnet and omphacite in the Ky-bearing eclogite have lower Fe contents than those in the Ky-free eclogite. Furthermore, the Ky-free eclogite was divided into two types on the basis of Ca content in garnet: Ca-rich (X grs > 0.32) and Ca-poor (X grs < 0.32) types, except for Ca-poor rim compositions. Application of conventional geothermobarometers to the Ky-bearing type and the Ky-free type with Ca-rich garnet yielded similar pressure-temperature (P-T ) conditions (3.2-4.8 GPa and 920-1160 °C) to those of previous studies, whereas the Ky-free type with Ca-poor garnet yielded slightly lower P-T conditions (3.1-3.4 GPa and 950-990 °C) than the other two types. The observed chemical variation of garnet is probably due to the difference in origins, whereby, according to our new results and previous findings, the Kybearing eclogite was derived from plagioclase-bearing crustal gabbro, whereas the Ky-free eclogite with Ca-rich garnet was derived from a crystal cumulate possibly in the mantle wedge. In the Ky-free eclogite samples with Ca-poor garnet, chemical compositions of garnet and omphacite are different from those in the other Ky-free samples, and those samples with Ca-poor garnet would have a different origin from the others. One of the Kyfree type with Ca-poor garnet retains garnet grains with chemical zonings probably created during the prograde history, although the eclogite underwent the extremely high temperature (~1000 °C) metamorphism. Calculated diffusion distances in garnet reach 0.5 mm during 2 million years, even if we adopted a low value of diffusion coefficient data. Thus, the residence time of the eclogite at the peak meatamorphic conditions would have been shorter than at least 2 million years. The subsequent decompression and cooling after the peak metamorphism were also probably very fast to avoid the chemical homogenization of garnet.

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Section: Geological Settingmentioning

confidence: 99%

Multiple origins of UHP eclogites in a garnet peridotite block (Nové Dvory, Czech Republic) and short duration of heating

ITAMI

Nakamura

Yasumoto

et al. 2022

Journal of Mineralogical and Petrological Sciences

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“…Zr-in-rutile geothermometry (ZIR) is a relatively new method and is used mainly for determining crystallization temperatures of rutile in various metamorphic and igneous rocks [67]. The key requirement for using the ZIR method is the determination of the Zr concentration in the rutile structure.…”

Section: Rutile Mineral Chemistry Occurrence and Zr-in-rutile (Zir) G...mentioning

confidence: 99%

Rutile Mineral Chemistry and Zr-in-Rutile Thermometry in Provenance Study of Albian (Uppermost Lower Cretaceous) Terrigenous Quartz Sands and Sandstones in Southern Extra-Carpathian Poland

Kotowski¹,

Nejbert²,

Olszewska-Nejbert³

2021

Minerals

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The geochemistry of detrital rutile grains, which are extremely resistant to weathering, was used in a provenance study of the transgressive Albian quartz sands in the southern part of extra-Carpathian Poland. Rutile grains were sampled from eight outcrops and four boreholes located on the Miechów, Szydłowiec, and Puławy Segments. The crystallization temperatures of the rutile grains, calculated using a Zr-in-rutile geothermometer, allowed for the division of the study area into three parts: western, central, and eastern. The western group of samples, located in the Miechów Segment, is characterized by a polymodal distribution of rutile crystallization temperatures (700–800 °C; 550–600 °C, and c. 900 °C) with a significant predominance of high-temperature forms, and with a clear prevalence of metapelitic over metamafic rutile. The eastern group of samples, corresponding to the Lublin Area, is monomodal and their crystallization temperatures peak at 550–600 °C. The contents of metapelitic to metamafic rutile in the study area are comparable. The central group of rutile samples with bimodal distribution (550–600 °C and 850–950 °C) most likely represents a mixing zone, with a visible influence from the western and, to a lesser extent, the eastern group. The most probable source area for the western and the central groups seems to be granulite and high-temperature eclogite facies rocks from the Bohemian Massif. The most probable source area for the eastern group of rutiles seems to be amphibolites and low temperature eclogite facies rocks, probably derived from the southern part of the Baltic Shield.

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“…For example, rutile in garnet has been used to constrain prograde P–T paths by combining its textural distribution and Zr‐in‐rutile geothermometry (e.g. Schantl et al, 2019; Usuki et al, 2017). In addition, prograde compositional growth zoning may be preserved in garnet despite high metamorphic peak temperatures, especially if slow‐diffusing trace elements like rare earth elements (REE)+Y are considered (e.g.…”

Section: Introductionmentioning

confidence: 99%

Repeated Caledonian burial and ultrafast cooling and exhumation of high‐pressure granulite facies rocks from the Blåhø Nappe on the island of Fjørtoft, Western Gneiss Region, Norway

Liu

Massonne

2023

Journal Metamorphic Geology

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The allochthonous Blåhø Nappe in the Nordøyane ultra high pressure (UHP) domain, Western Gneiss Region in Norway, acts as a window to examine geological processes occurring in continent–continent collisional zones, but many aspects regarding its tectonometamorphic evolution remain debated and elusive. In this contribution, an integrated study including major‐ and trace‐element zoning in garnet, phase equilibrium modelling and the simulation of cation diffusion in garnet was conducted on two high‐pressure (HP) granulite facies rocks from the Blåhø Nappe on the island of Fjørtoft. The results shed new light on the complex geodynamic processes that act in continent–continent collisional zones and finally shape collisional orogens. Phengite, biotite, amphibole, zoisite‐allanite and low‐Zr rutile enclosed in garnet likely attest to a prograde eclogite facies metamorphism for the studied rocks. Pressure–temperature (P–T) conditions of ~1.5–1.6 GPa and 615–670°C were retrieved for this stage. An extensive re‐equilibration under peak HP granulite facies conditions of ~1.5 GPa and 925 ± 50°C followed. Subsequently, the rocks were cooled and reburied to eclogite facies conditions of ~1.8–1.9 GPa and 805–825°C. This was followed by a final stage of decompression and cooling to amphibolite facies conditions of ~650–780°C and 0.5–1.0 GPa. Cooling and exhumation rates of >400°C/Ma and >75 km/Ma, respectively, indicating an ultrafast temperature and pressure decrease are estimated for this stage from simulations of cation diffusion in garnet. The anticlockwise P–T path obtained here is relatively complete and compatible with a repeated burial history during the Caledonian orogeny but not with UHP conditions proposed for the Blåhø Nappe. Our model proposes that the rocks later forming the Blåhø Nappe were buried to lower crustal depths of approximately 55 km equating to a geothermal gradient of ~13°C/km during the early Caledonian orogeny. Subsequent heating of these rocks to HP granulite facies conditions was likely driven by slab break‐off and hot mantle upwelling. Baltica underthrusting during the Scandian continent–continent collision cooled and transported the Blåhø Nappe to greater depths. The obtained cooling and exhumation rates indicate ultrafast exhumation, presumably in an exhumation channel.

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Significance of Zr-in-Rutile Thermometry for Deducing the Decompression P–T Path of a Garnet–Clinopyroxene Granulite in the Moldanubian Zone of the Bohemian Massif

Cited by 18 publications

References 77 publications

Multiple origins of UHP eclogites in a garnet peridotite block (Nové Dvory, Czech Republic) and short duration of heating

Multiple origins of UHP eclogites in a garnet peridotite block (Nové Dvory, Czech Republic) and short duration of heating

Rutile Mineral Chemistry and Zr-in-Rutile Thermometry in Provenance Study of Albian (Uppermost Lower Cretaceous) Terrigenous Quartz Sands and Sandstones in Southern Extra-Carpathian Poland

Repeated Caledonian burial and ultrafast cooling and exhumation of high‐pressure granulite facies rocks from the Blåhø Nappe on the island of Fjørtoft, Western Gneiss Region, Norway

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