Five generations of monazite in Langtang gneisses: implications for chronology of the Himalayan metamorphic core

Kohn, Matthew J.; Wieland, M.; Parkinson, C. D.; Upreti, B. N.

doi:10.1111/j.1525-1314.2005.00584.x

Cited by 239 publications

(258 citation statements)

References 58 publications

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“…This mineral may grow directly from the melt, or form due to final melt crystallization (see also Högdahl et al 2012). Notwithstanding this problem, a general trend of increasing Y content from initial melting up to melt crystallization has been observed (Kohn et al 2005). Given this, the youngest monazite should be the richest in Y, which is a consequence of garnet consumption during melting or postcrystallization retrogression during cooling.…”

Section: Y-th-u Systematics and Monazite Growthmentioning

confidence: 99%

“…The typically negligible amount of common Pb in the monazite lattice provides a unique opportunity for non-isotopic chemical electron microprobe (EPMA) dating (e.g., Suzuki and Adachi 1991;Montel et al 1996;Williams et al 2006;Suzuki and Kato 2008;Spear et al 2009). This feature of monazite is, in many cases, the greatest advantage, because the very high spatial resolution of the EMPA allows the dating of fine-scale compositional domains (e.g., Terry et al 2000;Dahl et al 2005;Kohn et al 2005;Pyle et al 2005;Mahan et al 2006;Krenn et al 2009;Petrík and Konečný 2009). …”

Section: Introductionmentioning

confidence: 99%

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Multiple monazite growth in the Åreskutan migmatite: evidence for a polymetamorphic Late Ordovician to Late Silurian evolution in the Seve Nappe Complex of west-central Jämtland, Sweden

Majka

Be’eri-Shlevin²,

Gee³

et al. 2012

J. Geosci.

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Monazite from granulite-facies rocks of the Åreskutan Nappe in the Scandinavian Caledonides (Seve Nappe Complex, Sweden) was dated using in-situ U-Th-total Pb chemical geochronology (CHIME). Multi-spot analyses of a non-sheared migmatite neosome yielded an age of 439 ± 3 Ma, whereas a sheared migmatite gave 433 ± 3 Ma (2σ). Although the obtained dates are rather similar, a continuous array of single dates from c. 400 Ma to c. 500 Ma suggests possibly a more complex monazite age pattern in the studied rocks. The grouping and recalculation of the obtained results in respect to Y-Th-U systematics and microtextural context allowed distinguishing several different populations of monazite grains/growth zones. In the migmatite neosome, low-Th and low-Y domains dated at 455 ± 11 Ma are considered to have grown under highgrade sub-solidus conditions, most likely during a progressive burial metamorphic event. The monazites with higher Th and lower Y yielded an age of 439 ± 4 Ma marking the subsequent partial melting event caused by decompression. The youngest (423 ± 13 Ma) Y-enriched monazite reveals features of fluid-assisted growth and is interpreted to date the emplacement of the Åreskutan onto the Lower Seve Nappe. In the sheared migmatite, the high-Th and low-U (high Th/U) monazite with variable Y contents yielded an age of 438 ± 4 Ma, which is interpreted to date the partial melting event. Relatively U-rich rims on some of the monazite grains again reveal features of fluid-assisted growth, and thus their age of 424 ± 6 Ma is interpreted as timing of the nappes emplacement. These results call, however, for further more precise, isotopic (preferably ion microprobe) dating of monazite in the studied rocks.

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Section: Y-th-u Systematics and Monazite Growthmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multiple monazite growth in the Åreskutan migmatite: evidence for a polymetamorphic Late Ordovician to Late Silurian evolution in the Seve Nappe Complex of west-central Jämtland, Sweden

Majka

Be’eri-Shlevin²,

Gee³

et al. 2012

J. Geosci.

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“…The debris-covered surface of Lirung Glacier is spatially heterogeneous and within the thermal survey area there are large boulders, gravel, sand, patches with dry shrubs, supraglacial ponds, and ice cliffs. The geology and consequently the supraglacial debris in this part of the valley largely consists of gneiss and quartzite (Kohn et al, 2005). Since all these surfaces have different emissivities, spatially distributed emissivity data is required to derive an accurate surface temperature.…”

Section: Object-based Emissivity Correctionmentioning

confidence: 99%

Mapping Surface Temperatures on a Debris-Covered Glacier With an Unmanned Aerial Vehicle

et al. 2018

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A layer of debris cover often accumulates across the surface of glaciers in active mountain ranges with exceptionally steep terrain, such as the Andes, Himalaya, and New Zealand Alps. Such a supraglacial debris layer has a major influence on a glacier's surface energy budget, enhancing radiation absorption, and melt when the layer is thin, but insulating the ice when thicker than a few cm. Information on spatially distributed debris surface temperature has the potential to provide insight into the properties of the debris, its effects on the ice below and its influence on the near-surface boundary layer. Here, we deploy an unmanned aerial vehicle (UAV) equipped with a thermal infrared sensor on three separate missions over one day to map changing surface temperatures across the debris-covered Lirung Glacier in the Central Himalaya. We present a methodology to georeference and process the acquired thermal imagery, and correct for emissivity and sensor bias. Derived UAV surface temperatures are compared with distributed simultaneous in situ temperature measurements as well as with Landsat 8 thermal satellite imagery. Results show that the UAV-derived surface temperatures vary greatly both spatially and temporally, with −1.4 ± 1.8, 11.0 ± 5.2, and 15.3 ± 4.7 • C for the three flights (mean ± sd), respectively. The range in surface temperatures over the glacier during the morning is very large with almost 50 • C. Ground-based measurements are generally in agreement with the UAV imagery, but considerable deviations are present that are likely due to differences in measurement technique and approach, and validation is difficult as a result. The difference in spatial and temporal variability captured by the UAV as compared with much coarser satellite imagery is striking and it shows that satellite derived temperature maps should be interpreted with care. We conclude that UAVs provide a suitable means to acquire surface temperature maps of debris-covered glacier surfaces at high spatial and temporal resolution, but that there are caveats with regard to absolute temperature measurement.

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“…Due to the fact that monazite contains negligible amounts of common Pb relative to radiogenic Pb (Parrish 1990), it is possible to use the chemical Th-U-total Pb method employing an electron microprobe to constrain its age (Jercinovic and Williams 2005;Jercinovic et al 2008;Konečný 2004;Montel et al 1996;Pyle et al 2005;Spear et al 2009;Adachi 1991, 1994;Suzuki and Kato 2008). Although chemical dating of monazite is mostly used in metamorphic petrology (Finger and Krenn 2007;Kohn et al 2005;Liu et al 2007;Rosa-Costa et al 2008;Tickyj et al 2004;Williams et al 2007), it has also found applications in constraining the ages of magmatic events with high precision (Just et al 2011).…”

Section: Introductionmentioning

confidence: 99%

U-total Pb timing constraints on the emplacement of the granitoid pluton of Stolpen, Germany

Lisowiec¹,

Budzyń²,

Słaby³

et al. 2014

Acta Geologica Polonica

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ABSTRACT:Lisowiec, K., Budzyń, B., Słaby, E., Schulz, B., and Renno, A.D. 2014. Th-U-total Pb timing constraints on the emplacement of the granitoid pluton of Stolpen, Germany. Acta Geologica Polonica, 64 (4), 457-472. Warszawa.Monazite from the Stolpen monzogranite (SE Germany) was studied to constrain the Th-U-total Pb age of pluton formation. Monazite grains demonstrate subtle to distinct patchy zoning related to slight compositional variations. Textural and compositional characteristics indicate that the monazite formed in a single magmatic event in a slightly heterogeneous system, and was only weakly affected by secondary alteration, which did not disturb the Th-U-Pb system. Chemical dating of the monazite gave a consistent age of 299 ± 1.7 Ma. The current study presents the first geochronological data for the Stolpen granite. It provides evidence that Stolpen is the youngest Variscan granitic intrusion in the Lusatian Granodiorite Complex and indicates that magmatic activity related to post-collisional extension in this region lasted at least 5my longer than previously assumed.

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Five generations of monazite in Langtang gneisses: implications for chronology of the Himalayan metamorphic core

Cited by 239 publications

References 58 publications

Multiple monazite growth in the Åreskutan migmatite: evidence for a polymetamorphic Late Ordovician to Late Silurian evolution in the Seve Nappe Complex of west-central Jämtland, Sweden

Multiple monazite growth in the Åreskutan migmatite: evidence for a polymetamorphic Late Ordovician to Late Silurian evolution in the Seve Nappe Complex of west-central Jämtland, Sweden

Mapping Surface Temperatures on a Debris-Covered Glacier With an Unmanned Aerial Vehicle

U-total Pb timing constraints on the emplacement of the granitoid pluton of Stolpen, Germany

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