Monazite behaviour during isothermal decompression in pelitic granulites: a case study from Dinggye, Tibetan Himalaya

Wang, Jia-Min; Wu, Fu‐Yuan; Rubatto, Daniela; Liu, Shi-Ran; Zhang, Jinjiang; Liu, Xiaochi; Yang, Lei

doi:10.1007/s00410-017-1400-y

Cited by 65 publications

(17 citation statements)

References 142 publications

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“…Typically, monazites are more susceptible to resorption during peak temperature than zircon (Yakymchuk & Brown, 2014). However, some older monazite relicts can survive complete dissolution if the monazite is large enough or armored by larger grains such as garnet or feldspar (Catlos et al, 2002;Wang et al, 2017). The preservation of Eocene prograde metamorphic domains in this work may reflect to the incomplete dissolution and/or armoring of the monazite grains.…”

Section: Tectonic Implicationsmentioning

confidence: 86%

Eocene Metamorphism and Anatexis in the Kathmandu Klippe, Central Nepal: Implications for Early Crustal Thickening and Initial Rise of the Himalaya

et al. 2021

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Note: Rock samples were collected in Kathmandu Nepal in summer of 2016 and 2017. The monazite trace elements and ages data were analyzed at the Institute of Geology and Geophysics, Chinese Academy of Sciences by Gautam Prashad Khanal and Jia-Min Wang in 2019. S2.1: Eu N /Eu* N distribution over the 208 Pb/ 232 Th ages. S2.2: HREE distribution over the 208 Pb/ 232 Th ages. S2.3: Yn N /Gd N distribution over the 208 Pb/ 232 Th ages. S2.4: BSE images of the monazites used for grain separate monazite dating. S2.5: BSE images of the monazites in thinsection used for in-situ monazite dating. S2.1: EuN/Eu*N distribution over the 208 Pb/ 232 Th ages. Caption: Plot of Eu N /Eu* N ratio versus Pb 208 /Th 232 age for the analysed monazite grains in the study area.The black bars represent 2 sigma age error, red rectangle represent older cores, and blue circle represent younger rims while green triangle represent insitu grains hosted in Bt, Qz or Kfs. Grey arrows in samples 17KN10 and 17KN09 show feldspar growth trend with decreasing age. S2.2: HREE distribution over the 208 Pb/ 232 Th ages. Caption: Plot of normalised Heavy Rare Earth Elements (HREE N) versus Pb 208 /Th 232 age for the analysed monazite grains in the study area. The black bars represent 2 sigma age error, red rectangle represent older cores, and blue circle represent younger rims while green triangle represent insitu grains hosted in Bt, Qz or Kfs. Grey arrows in samples 17KN10, 17KN09 and 17KN07 show garnet breakdown trend with decreasing age. S2.3: Yn N /Gd N distribution over the 208 Pb/ 232 Th ages. Caption: Plot of Yb N /Gd N ratio versus Pb 208 /Th 232 age for the analysed monazite grains in the study area. The black bars represent 2 sigma age error, red rectangle represent older cores, and blue circle represent younger rims while green triangle represent insitu grains hosted in Bt, Qz or Kfs. Grey arrows in samples 17KN10, 17KN09 and 17Kn07 show garnet breakdown trend with decreasing age. S2.4: BSE images of the monazites grain separates showing laser spot. Caption: Selected BSE images of dated monazite separate grains showing spot locations. The black circles are 24μm and the numbers represent 208 Pb/ 232 Th ages in Ma. S2.5: BSE images of the monazites in thin section showing laser spot. Caption: The thinsection plane polarised image (Upper figure) showing location and textural control of the dated monazites for the sample 17KN09. The red boxes represent the monazite location, red circles laser spot which are 24μm and the red numbers represent 208 Pb/ 232 Th ages in Ma.

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Section: Tectonic Implicationsmentioning

confidence: 86%

Eocene Metamorphism and Anatexis in the Kathmandu Klippe, Central Nepal: Implications for Early Crustal Thickening and Initial Rise of the Himalaya

et al. 2021

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“…These features commonly indicate monazite recrystallization in the presence of aqueous fluids or hydrous melts (e.g. Kelly, Harley, & Mӧller, ; Štípská et al., ; Wang et al., ; Williams, Jercinovic, Harlov, Budzyń, & Hetherington, ). This process is compatible with the here‐invoked anatexis at temperatures significantly above 700°C.…”

Section: Discussionmentioning

confidence: 99%

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

Liu

Massonne

2019

Journal Metamorphic Geology

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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, the ‘diamondiferous’ kyanite–garnet gneiss from the Blåhø Nappe on Fjørtoft was revisited to determine if such a process was correct. Two types of garnet, porphyroblastic garnet‐1 and fine‐grained garnet‐2, were recognized in the gneiss. The core of garnet‐1 is poor in Ca and documents P–T conditions of 1.2–1.3 GPa at c. 880°C based on pseudosection modelling. The inner rims of garnet‐1 and the core of garnet‐2 are both richer in Ca, recording P–T conditions of 1.35–1.45 GPa and 770–820°C. Application of conventional geothermobarometry on the outer rim of garnet‐1 and the rim of garnet‐2 yielded retrograde P–T conditions of 0.75–0.90 GPa and 610–685°C. These estimates define an anticlockwise P–T path at pressures below 1.5 GPa. Accessory monazite was dated with the electron microscope. Relicts of detrital monazite in the gneiss point to Sveconorwegian and possibly also Cryogenian provenance for the detritus of the sedimentary protolith. Metamorphic monazite in the gneiss records a wide age range from 460 to 380 Ma, with a peak c. 435 Ma and a shoulder at 395 Ma. These data suggest that the original (Ediacaran?) Baltica margin sediment (gneiss protolith) was transported to the base of an overlying plate during the early Caledonian (pre‐Scandian) orogeny. A long residence time of the metasedimentary rock at this base caused its heating to 880°C and homogenization of the early garnet chemistry. The late Caledonian (Scandian) collision between Baltica and Laurentia led to further burial, during which the studied gneiss was close to the former surface of the downgoing continental plate and, thus, cooled. The reconstructed P–T–t path confirms the multiple burial history of the Blåhø Nappe but contradicts previous ideas of deep burial of the Fjørtoft gneiss to more than 100 km.

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“…2 stage 4) and also the characteristic inverted metamorphism induced in the footwall of the hot extruded bodies (LeFort 1975). Even today the base of the thickened crust is at eclogite facies conditions so it is not surprising that several locations of anatectic HHC gneisses, in some cases c. 200 km south of the ITSZ, contain eclogites overprinted by granulite-facies assemblages at Oligocene to Miocene times (Groppo et al 2007;Cottle et al 2009;Grujic et al 2011;Warren et al 2011a, b;Lombardo et al 2016;Wang et al 2015Wang et al , 2017Corrie et al 2016).…”

Section: Metamorphic Evolution Of the Himalayamentioning

confidence: 99%

Tso Morari coesite eclogite: pseudosection predictions v. the preserved record and implications for tectonometamorphic models

O’Brien

2018

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Ultrahigh-pressure eclogites of the Tso Morari area, NW Himalaya (Ladakh, India), have been intensively investigated petrographically and petrologically with surprisingly different results. Metamorphic subduction paths based on mineral isopleths in pressure-temperature pseudosections in some studies claim concave (to the temperature axis) pressure-temperature paths predicting significant Ca-Mg-Fe garnet growth in the lawsonite and glaucophane fields: a prediction at odds with abundant epidote/clinozoisite and sodic-calcic amphibole inclusions in garnet interiors more probable along a convex path. One study deduced strong heating still at high pressures and proposed a felsic diapir rising through the mantle wedge: an explanation strongly at odds with well-documented glaucophane cores to barroisite replacing matrix omphacite requiring a cold exhumation most likely back up the subduction channel. In addition, matrix magnesite rimmed by dolomite suggests pressures well into the coesite (if not diamond) stability field: something neglected in most studies. Despite the application of modern analytical and thermodynamic modelling tools, the peak conditions attained by Tso Morari ultrahigh-pressure rocks are often poorly deduced and at odds with simple observations. Is this problem perhaps hindering the reliable identification of new ultrahigh-pressure terranes?

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Monazite behaviour during isothermal decompression in pelitic granulites: a case study from Dinggye, Tibetan Himalaya

Cited by 65 publications

References 142 publications

Eocene Metamorphism and Anatexis in the Kathmandu Klippe, Central Nepal: Implications for Early Crustal Thickening and Initial Rise of the Himalaya

Eocene Metamorphism and Anatexis in the Kathmandu Klippe, Central Nepal: Implications for Early Crustal Thickening and Initial Rise of the Himalaya

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

Tso Morari coesite eclogite: pseudosection predictions v. the preserved record and implications for tectonometamorphic models

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