Petrological, geochronological, and geochemical potential accounting for continental subduction and exhumation: A case study of felsic granulites from South Altyn Tagh, northwestern China

Abstract Deciphering the formation and geodynamic evolution of high-pressure (HP) granulites in a collisional orogeny can provide crucial constraints on the geodynamic evolution of subduction-exhumation. To fully exploit the geodynamic potential of metamorphic rocks, it is necessary to constrain the metamorphic ages, although it is difficult to link zircon and monazite ages to metamorphic evolution. A good case study for understanding these geodynamic processes is felsic granulites in the Bashiwake area, South Altyn Tagh. Petrographic observations suggest that the studied felsic granulites have suffered multi-stage metamorphism, and the distinct metamorphic events were documented by compositional zoning and high Y + heavy rare earth element (HREE) concentrations in the large garnet porphyroblast. Zircon U-Pb dating yielded two major age clusters: one age cluster at ca. 900 Ma represents the age of the protolith for the felsic granulite, and another age cluster at ca. 500 Ma represents the post-UHT (ultrahigh temperature) stage based on the rare earth element distribution coefficients between zircon and garnet. Meanwhile, in situ monazites U-Pb dating yielded a weighted mean 206Pb/238U age of 482 ± 3.5 Ma, and the monazite U-Pb age was interpreted to be in agreement with the metamorphic zircon rims data, which together with zircon recorded the cooling time after the UHT stage. Whole-rock major and trace elements as well as Sr-Nd isotopes suggest that the protolith of the felsic granulite derived from partial melting of ancient crustal materials with the addition of mantle materials. Integrating these results along with previous studies, we propose that the felsic granulites metamorphosed from the Neoproterozoic granitic rocks, and the granitic rocks with associated mafic-ultramafic rocks suffered a common high-pressure–ultrahigh temperature (HP-UHT) metamorphism and subsequent granulite-facies metamorphism. A tentative model of subduction-relamination was proposed for the geodynamic evolution of the Bashiwake unit, South Altyn Tagh.

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Rare earth element distribution in tropical coastal wetland sediments: a case study from Vembanad estuary, southwest India

Arabian Journal of Geosciences ◽

10.1007/s12517-015-2246-0 ◽

2016 ◽

Vol 9 (3) ◽

Cited By ~ 5

Author(s):

M. C. Manoj ◽

Biswajeet Thakur ◽

Vandana Prasad

Keyword(s):

Rare Earth ◽

Rare Earth Element ◽

Earth Element ◽

Coastal Wetland ◽

Element Distribution ◽

Southwest India ◽

Rare Earth Element Distribution

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Rare-earth element distribution in Archaean gneisses and anorthosites, Godthåb area, West Greenland

Earth and Planetary Science Letters ◽

10.1016/0012-821x(74)90142-3 ◽

1974 ◽

Vol 22 (4) ◽

pp. 328-338 ◽

Cited By ~ 71

Author(s):

R.K. O'Nions ◽

R.J. Pankhurst

Keyword(s):

Rare Earth ◽

Rare Earth Element ◽

Earth Element ◽

Element Distribution ◽

West Greenland ◽

Rare Earth Element Distribution

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Transport and transformation of riverine neodymium isotope and rare earth element signatures in high latitude estuaries: A case study from the Laptev Sea

Earth and Planetary Science Letters ◽

10.1016/j.epsl.2017.08.010 ◽

2017 ◽

Vol 477 ◽

pp. 205-217 ◽

Cited By ~ 10

Author(s):

Georgi Laukert ◽

Martin Frank ◽

Dorothea Bauch ◽

Ed C. Hathorne ◽

Marcus Gutjahr ◽

...

Keyword(s):

Rare Earth ◽

Rare Earth Element ◽

High Latitude ◽

Earth Element ◽

Laptev Sea ◽

Transport And Transformation ◽

The Laptev Sea

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Geology and geochemistry of Huronian rhyolites and low-Ti continental tholeiites from the Thessalon region, central Ontario

Canadian Journal of Earth Sciences ◽

10.1139/e87-130 ◽

1987 ◽

Vol 24 (7) ◽

pp. 1360-1385 ◽

Cited By ~ 19

Author(s):

Wayne T. Jolly

Keyword(s):

Rare Earth ◽

Rare Earth Element ◽

Earth Element ◽

Magma Mixing ◽

Mantle Metasomatism ◽

Granitic Rocks ◽

Heavy Rare Earth Element ◽

Tonalitic Gneiss ◽

Oceanic Basalts ◽

Low K

Bimodal volcanism associated with early phases of Huronian rifting in central Ontario, dated about 2450 Ma, produced low-Ti tholeiitic basalts and two varieties of crustally derived calc-alkaline rhyolite. Early tholeiites are characteristically highly evolved, have Mg* values from 30 to 50, and display pronounced enrichment in large-ion lithophile elements (LILE) and light rare-earth element (LREE) in comparison with modern oceanic basalts, fractionated heavy rare-earth element (HREE) patterns, and low Ti, Zr, P, Nb, Ba, and K abundances. Ti/Zr ratios rise progressively in early basalts and associated basaltic andesite fractionates from about 35 in early flows to 55 in central units. Late basalts also carry enriched LILE and LREE, but, in contrast to early types, have average Mg* values greater than 50 and lower rare-earth element (REE) abundances with flat HREE patterns. They also display negative Ba, Nb, and P anomalies on chondrite-normalized distribution diagrams, but lack low K, Zr, and Ti contents. Their Ti/Zr ratios of about 80 approach chondritic levels. Melting models suggest the differences are explained by lower degrees of fusion (as low as 10%) in a hydrated, LILE- and LREE-enriched peridotite during generation of the early basalts, leaving a residue containing appreciable garnet, amphibole, Ti oxides, zircon, and apatite.Erupted simultaneously with the basalts were two distinctive rhyolite types: (1) a low-LILE, high-LREE group (25% of analysed specimens), derived by −20% melting of granulitic siliceous tonalitic gneiss, presumably at deep crustal levels, and (2) a high-LILE, low-LREE group (75%), derived, probably at shallower levels, by ≤ 30% melting in granitic rocks with pegmatitic or leucogranitic compositions. Mutual magma mixing of basalts and rhyolites during early stages of volcanism produced abundant hybrid andesites, but the frequency of contamination is much lower in later units.Hypothetical subcontinental source compositions, calculated from the Raleigh equation, suggest that the Huronian mantle had already undergone a complex history. Low Ba, Nb, P, Ti, and depleted HREE abundances compared with abundances for modern oceanic basalts suggest that a basaltic melt had already been withdrawn from this source during Archean time. Subsequently, an episode of hydrous metasomatism enriched the source in LILE and LREE. The latter event resulted from (1) subcontinental mantle metasomatism by previous Archean subduction, (2) mantle metasomatism during the terminal Archean Kenoran Orogeny, or (3) a wave of hydrous metasomatism accompanying Huronian mantle convection immediately preceding volcanism.

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