Monazite Behaviour during Metamorphic Evolution of a Diamond-bearing Gneiss

2020 ◽  
Author(s):  
Igor Petrík ◽  
Marian Janák ◽  
Iwona Klonowska ◽  
Jaroslaw Majka ◽  
Niko Froitzheim ◽  
...  
Keyword(s):  
Granulite Facies ◽  
Age Dating ◽  
Science Center ◽  
Rock Composition ◽  
Thermally Activated ◽  
Eu Anomaly ◽  
Small Crystals ◽  
Icp Ms ◽  
Nappe Complex ◽  
Seve Nappe Complex

<p>We studied monazite behaviour in UHP diamond-bearing gneiss from Saxnäs in the Seve Nappe Complex of the Scandinavian Caledonides (Petrík et al., 2019). Although the rock has been re-equilibrated under  granulite facies and partial melting conditions, the UHP stage is recorded by the presence of diamond. Microdiamonds occur in situ as inclusions in garnet, kyanite and zircon, either as single-crystal or polyphase inclusions with Fe-Mg carbonates, rutile and CO<sub>2</sub>. Two garnet types have been recognised: dominant Grt I  with inclusions of diamond found mostly in the garnet rims, which suggests that originally the bulk of Grt I grew at UHP conditions. Grt II, forming small crystals, overgrowths on, or domains within Grt I originated by dehydration melting reactions involving breakdown of phengite and clinopyroxene during decompression. Monazite occurs in the rims of Grt I close to microdiamond, where garnet shows the highest pyrope content and a secondary peak of yttrium. Such a position indicates thermally activated diffusion under high temperature at the end of prograde metamorphism. Based on such textural relations, we argue that monazite formed at UHP conditions.</p><p>Monazite composition shows negative Eu anomalies and moderate Y contents, which is not in agreement with common interpretation that UHP conditions necessarily lead to the absence of Eu anomaly and low Y content due to absence of plagioclase and high garnet content. We explain this by the effect of whole-rock composition. LA ICP MS analyses show that whole-rock budget is controlled by monazite, apatite and garnet, all having negative Eu anomalies. Whole rock composition is successfully modelled by (wt. %) garnet 16, apatite 3, monazite 0.06. We conclude that the Eu anomaly is inherited from the source rock, not reflecting the coexistence with plagioclase and/or K-feldspar, which are unstable at UHP conditions. Uniform garnet abundance (16 vol. %) above 20 kbars predicted by pseudo-section modelling explains the lack of Y decrease due to the increase of garnet content at UHP conditions. Our results suggest that the effect of the whole-rock composition may be more important than that of coexisting phases.</p><p>U-Th-Pb chemical age dating of monazites yields an isochron centroid age of 472 ±3 Ma. We interpret this age as monazite growth under UHP conditions related to subduction of the Baltican continental margin in Early Ordovician time.</p><p>This work was supported by the projects APVV-14-0278 and APVV-18-0107, National Science Center “CALSUB” 2014/14/E/ST1/00321</p><p>Reference: Petrík, I., Janák, M., Klonowska, I., Majka, J., Froitzheim, N., Yoshida, K., Sasinková, V., Konečný, P., Vaculovič, T. 2019. Journal of Petrology doi: 10.1093/petrology/egz051</p>

Monazite behaviour during metamorphic evolution of a diamond-bearing gneiss: a case study from the Seve Nappe Complex, Scandinavian Caledonides

2019 ◽  
Author(s):  
I Petrík ◽  
M Janák ◽  
I Klonowska ◽  
J Majka ◽  
N Froitzheim ◽  
...  
Keyword(s):  
Granulite Facies ◽  
Age Dating ◽  
Prograde Metamorphism ◽  
Metamorphic Evolution ◽  
Heavy Rare Earth Element ◽  
Rock Composition ◽  
Scandinavian Caledonides ◽  
Nappe Complex ◽  
The Matrix ◽  
Seve Nappe Complex

Abstract Monazite is a common mineral in metapelitic rocks including those which underwent ultra-high pressure (UHP) metamorphism. During metamorphic evolution monazite adapts its composition to the changing mineral assemblage, especially in its heavy rare earth element contents. We studied this process in diamond-bearing gneiss containing monazite, from Saxnäs in the Seve Nappe Complex of the Scandinavian Caledonides. Although the rock has been re-equilibrated under granulite facies and partial melting conditions, it still preserves minerals from the UHP stage: garnet, kyanite, rutile, and especially diamond. Microdiamonds occur in situ as inclusions in garnet, kyanite and zircon, either as single-crystals or polyphase inclusions with Fe-Mg carbonates, rutile and CO2. Both monazite and diamond occur in the rims of garnet showing the highest pyrope content and a secondary peak of yttrium. Such a position indicates thermally activated diffusion under high temperature at the end of prograde metamorphism. Monazite compositions show negative Eu anomalies, which we interpret to be inherited from the source rock, not reflecting the coexistence with plagioclase and/or K-feldspar which are unstable at UHP conditions. Our results suggest that the effect of whole-rock composition may be more important than that of coexisting phases. The UHP monazite was most likely formed from allanite during subduction and prograde metamorphism. The monazites included in garnet and kyanite are mostly unaltered, whereas those in the matrix show breakdown coronas consisting of apatite, REE-epidote/allanite and REE carbonate, likely formed due to pressure decrease and cooling. U-Th-Pb chemical age dating of monazites yields an isochron centroid age of 472 ±3 Ma. We interpret this age as monazite growth under UHP conditions related to subduction of the Baltica continental margin in Early Ordovician time.

scholarly journals U-Pb Zircon Dating of Migmatitic Paragneisses and Garnet Amphibolite from the High Pressure Seve Nappe Complex in Kittelfjäll, Swedish Caledonides

Minerals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 295 ◽  
Author(s):  
Michał Bukała ◽  
Jarosław Majka ◽  
Katarzyna Walczak ◽  
Adam Włodek ◽  
Melanie Schmitt ◽  
...  
Keyword(s):  
Granulite Facies ◽  
Passive Margin ◽  
Metamorphic Zircon ◽  
Garnet Amphibolite ◽  
Iapetus Ocean ◽  
Icp Ms ◽  
Nappe Complex ◽  
The Matrix ◽  
Seve Nappe Complex ◽  
Ree Patterns

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.

Dating polymetamorphism using titanite: Linking trace elements, textures, and ages

2021 ◽  
Author(s):  
Jesse Walters ◽  
Alicia Cruz-Uribe ◽  
Won Joon Song ◽  
Joshua Stone ◽  
Hanna Brooks ◽  
...  
Keyword(s):  
Trace Elements ◽  
Trace Element ◽  
Bulk Composition ◽  
Granulite Facies ◽  
Compositional Variation ◽  
Excimer Laser Ablation ◽  
Eu Anomaly ◽  
Fluid Infiltration ◽  
Icp Ms ◽  
The University

<p>Here we present titanite U-Pb dates from two banded calc silicate gneisses (SSP18-1A and 1B) from western Maine. Mineral textures and compositions display multiple phases of metamorphism. The peak lower granulite facies assemblage is Di + Kfs + Pl + Ttn, with little to no calcite present. Late Czo + Tr replaces Di + Pl, suggesting an influx of X<sub>H2O</sub> > 0.90 fluids. Nearby metapelites show the transition from sillimanite-bearing to muscovite-bearing assemblages, indicating that fluid infiltration may be widespread. Compositional maps of clinopyroxene in SSP18-1B show fracturing and rehealing of early Fe-rich diopside with late Mg-rich diopside. Both samples exhibit overprinting of An-rich plagioclase by increasingly Ab-rich plagioclase. Titanite grains in both samples exhibit BSE textures and compositional variation consistent with multiple phases of growth and dissolution-reprecipitation reactions.</p><p>Titanite trace element and U-Pb data were collected by LA-ICP-MS at the University of Maine using an ESI NWR193<sup>UC</sup> excimer laser ablation system coupled to an Agilent 8900 ICP-MS. Single spot ages range from 280 to 400 Ma with 12-20 Ma propagated 2SE. Four composition-date domains are identified in SSP18-1B: A. 400 ± 8 Ma (dark BSE cores), B. 372 ± 4 Ma (bright BSE cores), C. 342 ± 6 Ma (bright BSE cores, no Eu anomaly), and D. 302 ± 3 Ma (dark BSE rims, low LREE). Titanite Fe and Y concentrations increase with decreasing date, whereas Sr concentrations decrease. In clinopyroxene, Fe and Y decrease between high Fe-diopside and late Mg-diopside, placing the fracturing and rehealing events between 400 and 372 Ma. Strontium concentrations in titanite decrease between subsequent generations of plagioclase, diopside, and titanite, suggesting a continual fractionation of Sr from the reactive bulk composition. Low LREE in ca. 300 Ma titanite domains in both samples are consistent with the formation of texturally late allanite and clinozoisite, thus constraining the timing of the high X<sub>H2O</sub> fluid infiltration event. Zr-in-titanite temperatures for rims in the quartz-bearing SSP18-1B give a weighted mean T of 764 °C at 4.5 GPa, consistent with the muscovite-absent sillimanite-bearing assemblage in garnet cores from metapelite samples. However, the 100-150 °C lower Grt-Bt temperatures for metapelites are not consistent with peak metamorphic phase equilibria. Our data demonstrate the utility of linking titanite textures and trace element concentrations with those of other minerals to reveal past metamorphic and deformational events. Additionally, we show that titanite may reliably preserve U and Pb isotopic ratios, trace elements, and textures over subsequent high-T metamorphic events.</p>

scholarly journals Ba- and Ti-enriched dark mica from the UHP metasediments of the Seve Nappe Complex, Swedish Caledonides

Mineralogia ◽  
2015 ◽  
Vol 46 (1-2) ◽  
pp. 41-50
Author(s):  
Jarosław Majka ◽  
Łukasz Kruszewski ◽  
Åke Rosén ◽  
Iwona Klonowska
Keyword(s):  
Granulite Facies ◽  
Stability Field ◽  
Metasedimentary Rocks ◽  
High Pressure Metamorphism ◽  
Nappe Complex ◽  
Crystallochemical Formula ◽  
Seve Nappe Complex ◽  
The Mean ◽  
End Members ◽  
Parental Rock

AbstractWe report on the occurrence of peculiar Ba- and Ti-enriched dark mica in metasedimentary rocks that underwent high-pressure metamorphism in the diamond stability field followed by decompression to granulite facies conditions. The mica occurs as well-developed preserved laths in a quartzofeldspathic matrix. The mean concentrations of BaO and TiO2in the mica are 11.54 and 7.80wt%, respectively. The maximum amounts of these components are 13.38wt% BaO and 8.45wt% TiO2. The mean crystallochemical formula can be expressed as (K0.54Ba0.39Na0.02Ca0.01)Σ0.96(Fe1.37Mg0.85Ti0.50Al0.29Mn0.01Cr0.01)Σ3.03(Si2.59Al1.41)Σ4.00O10(OH1.30O0.66F0.02S0.01)Σ1.99, withoxyannite,oxy-ferrokinoshitaliteand siderophyllite as dominating end-members. Based on the petrographical observations, it is proposed that the dark mica was formed at a rather late stage in the evolution of the parental rock, i.e. under granulite facies conditions.

Late Neoproterozoic granulite facies metamorphism of the Upper Gneiss unit (Seve Nappe Complex) in the Váivančohkka-Salmmečohkat area, northern Scandinavian Caledonides 

2021 ◽  
Author(s):  
Riccardo Callegari ◽  
Katarzyna Walczak ◽  
Grzegorz Ziemniak ◽  
Christopher Barnes ◽  
Jaroslaw Majka
Keyword(s):  
Partial Melting ◽  
Thermal Evolution ◽  
Granulite Facies ◽  
Stability Field ◽  
Granulite Facies Metamorphism ◽  
Scandinavian Caledonides ◽  
Nappe Complex ◽  
Seve Nappe Complex ◽  
Break Up ◽  
Late Neoproterozoic

<p>Here, we present preliminary petrochronological results of paragneisses and schists containing bodies of metamafic rocks belonging the Upper Gneiss unit that occurs within the Seve Nappe Complex (SNC) in the Váivančohkka-Salmmečohkat area, north of the lake Torneträsk in northern Sweden and Norway.</p><p>At the outcrop scale, the paragneiss is pervasively foliated and bears features of migmatization. It hosts garnet amphibolite bodies that are locally transected by leucocratic veins. Thin section observations of the paragneiss reveal a mineral assemblage composed of Q+Grt+Amp+Bi±Pl±Ms±Sil±Ru. The leucocratic vein contains Q+Pl+Ms+Bi+Grt+Kfs±Sil. Importantly, some of the studied gneisses contain quartz, exhibiting lobate boundaries, as well as garnet surrounded by melt rim. The presence of quartz forming pseudomorphs after melt was also identified and observed to host both monophase and fluid inclusions. All of these microtextures are indicative of partial melting.</p><p>Preliminary pressure-temperature estimates derived using conventional geothermobarometry and phase equilibrium modelling corroborated petrographic observations. The peak metamorphic conditions were estimated to 8–10kbar and 800–850°C, i.e., in the stability field of melt.</p><p>Uranium-Pb zircon and Th-U-total Pb monazite dating of the migmatitic paragneiss yielded consistent age estimates of 602±5Ma and 599±3Ma, respectively. Nearly the same U-Pb age of 604±7Ma was obtained for the zircon from the leucocratic vein transecting the amphibolite within the studied gneiss. Interestingly, no Caledonian zircon nor monazite were identified. Considering the textural position of the dated zircon and monazite, as well as their chemical character, we suggest that these minerals date the partial melting event recorded by the rocks.</p><p>Regionally, we interpret that the Upper Gneiss unit of SNC in the Váivančohkka-Salmmečohkat area could be a northern continuation of the Leavasvággi gneiss associated with the Vassačoru Igneous Complex of SNC in the Kebnekaise region. Notably, the latter reveals evidence of high temperature metamorphism at c. 600Ma (Paulsson and Andréasson 2002) and its mafic component (see also Rousku et al. in this session) could be an equivalent to the metamafic rocks enclosed within the Upper Gneiss unit. The Leavasvággi gneiss and the Upper Gneiss unit together with similar rocks farther north in Indre Troms and in Corrovare which also yield a c. 610-600Ma age of high grade overprint (Gee et al. 2016; Kjøll et al. 2019). Altogether, these areas with only localized Caledonian influence diverge from traditional models developed for the SNC farther south and offer an additional insight into the development of the late Neoproterozoic margin of Baltica at the early stages of Iapetus opening.</p><p>This study was supported by the National Science Centre (Poland) grant no. 2019/33/B/ST10/01728 to J. Majka.</p><p>References</p><p>Gee et al. 2016. Baltoscandian margin, Sveconorwegian crust lost by subduction during Caledonian collisional orogeny. GFF 139, 36–51.</p><p>Kjøll et al. 2019. Timing of break-up and thermal evolution of a pre-Caledonian  Neoproterozoic exhumed magma-rich rifted margin. Tectonics 38, 1843-1862.</p><p>Paulsson & Andréasson 2002. Attempted break-up of Rodinia at 850 Ma: geochronological evidence from the Seve–Kalak Superterrane, Scandinavian Caledonides. JGS, 159, 751-761.</p>

Timing of deformation, metamorphism and leucogranite intrusion in the lower part of the Seve Nappe Complex in central Jämtland, Swedish Caledonides

2021 ◽  
Author(s):  
Iwona Klonowska ◽  
Anna Ladenberger ◽  
David G. Gee ◽  
Pauline Jeanneret ◽  
Yuan Li
Keyword(s):  
High Pressure ◽  
White Mica ◽  
Detrital Zircons ◽  
Amphibolite Facies ◽  
Foreland Basins ◽  
Middle Ordovician ◽  
Metamorphic History ◽  
Icp Ms ◽  
Nappe Complex ◽  
Seve Nappe Complex

<p>The new LA-ICP-MS zircon isotope age data from paragneiss, amphibolite and two leucogranite intrusions in the Lower Seve Nappe of the Åre synform in the Caledonides of central Jämtland provide evidence of both Silurian and Ordovician tectonothermal histories. Well established concordant c. 468 and c. 470 Ma magmatic ages for the Så quarry leucogranite, which cut earlier foliations and folds in the host-rock amphibolites and paragneisses, imply a tectonothermal history prior to the Middle Ordovician (c. 469 Ma), perhaps synchronous with what has been previously recognized in the Seve Nappe Complex of Norrbotten (e.g. Root & Corfu, 2012), 400 km farther north in the Swedish Caledonides, and very recently also in the Middle Seve Nappe in central Jämtland (Walczak et al. 2020).</p><p>The field relationships and data presented here show that magmatic activity occurred during the early Silurian (c. 443 Ma) and earlier during the Early to Middle Ordovician (c. 469 Ma), and that deformation and metamorphism took place both prior to and after c. 469 Ma. The Lower Seve rocks from the nearby COSC-1 drill core have been metamorphosed in the upper amphibolite facies, however, the remnants of the high-pressure metamorphic history are preserved in the relic minerals, including high-silica white mica, in the garnet-bearing mica schists. The exact age of the high-pressure metamorphism is not known so far; however, it predates the 460-430 Ma amphibolite facies deformation recorded by titanites in the amphibolites (Giuntoli et al. 2020).    </p><p>Zircons in an amphibolite proved to be highly discordant but indicate Early Silurian metamorphism during isoclinal folding. Detrital zircons in a paragneiss are dominated by Sveconorwegian populations, but also include a range of younger Neoproterozoic grains down to the Early Ediacaran (c. 600 Ma).</p><p>This new evidence of early Caledonian deformation and metamorphism indicates that the Seve tectonothermal history in central Jämtland probably started early in the Ordovician, or before. Subduction and accretion along the Baltoscandian outer margin occurred prior to the Scandian continent-continent collision, with Siluro-Devonian emplacement of the Seve Nappe Complex across the foreland basins onto the Baltoscandian platform.</p><p>References:</p><p>Giuntoli, F., Menegon, L., Warren, C.J., Darling, J., Anderson, M.W. 2020. Tectonics, 39, e2020TC006267, https://doi.org/10.1029/2020TC006267.</p><p>Root, D., Corfu, F. 2012. Contributions to Mineralogy and Petrology, 163, 769-788, https://doi.org/10.1007/s00410-011-0698-0.</p><p>Walczak, K., Barnes, C.J., Majka, J., Gee, D.G. Klonowska, I., 2020. Geoscience Frontiers (in press), https://doi.org/10.1016/j.gsf.2020.11.009.</p><p>This work is financially supported by the National Science Centre (Poland) research project no. 2018/29/B/ST10/02315 and is part of the ICDP project “Collisional Orogeny of the Scandinavian Caledonides.”</p>

NEW AGES CONSTRAIN TIMING OF CALEDONIAN METAMORPHISM ACROSS VÄSTERBOTTEN, SEVE NAPPE COMPLEX, SWEDEN

2020 ◽  
Author(s):  
Emily O. Walsh ◽  
◽  
Michael W. McRivette ◽  
Morgan Casarez ◽  
Jillian Shew ◽  
...  
Keyword(s):  
Nappe Complex ◽  
Seve Nappe Complex

scholarly journals Zircon U–Pb Dating and Lu-Hf Isotope of the Retrograded Eclogite from Chicheng, Northern Hebei Province, China

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xu Kong ◽  
Xueyuan Qi ◽  
Wentian Mi ◽  
Xiaoxin Dong
Keyword(s):  
Regional Metamorphism ◽  
Granulite Facies ◽  
Amphibolite Facies ◽  
Metamorphic Event ◽  
Isotopic Data ◽  
Metamorphic Condition ◽  
Eu Anomaly ◽  
Facies Metamorphism ◽  
Eclogite Facies ◽  
Plagioclase Gneiss

We report zircon U–Pb ages and Lu-Hf isotopic data from two sample of the retrograded eclogite in the Chicheng area. Two groups of the metamorphic zircons from the Chicheng retrograded eclogite were identified: group one shows characteristics of depletion in LREE and flat in HREE curves and exhibit no significant Eu anomaly, and this may imply that they may form under eclogite facies metamorphic condition; group two is rich in HREE and shows slight negative Eu anomaly indicated that they may form under amphibolite facies metamorphic condition. Zircon Lu-Hf isotopic of εHf from the Chicheng eclogite has larger span range from 6.0 to 18.0, which suggests that the magma of the eclogite protolith may be mixed with partial crustal components. The peak eclogite facies metamorphism of Chicheng eclogite may occur at 348.5–344.2 Ma and its retrograde metamorphism of amphibolite fancies may occur at ca. 325.0 Ma. The Hongqiyingzi Complex may experience multistage metamorphic events mainly including Late Archean (2494–2448 Ma), Late Paleoproterozoic (1900–1734 Ma, peak age = 1824.6 Ma), and Phanerozoic (495–234 Ma, peak age = 323.7 Ma). Thus, the metamorphic event (348.5–325 Ma) of the Chicheng eclogite is in accordance with the Phanerozoic metamorphic event of the Hongqiyingzi Complex. The eclogite facies metamorphic age of the eclogite is in accordance with the metamorphism (granulite facies or amphibolite facies) of its surrounding rocks, which implied that the tectonic subduction and exhumation of the retrograded eclogite may cause the regional metamorphism of garnet biotite plagioclase gneiss.

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