Geochemistry and geochronology of dolerite dykes from the Daba and Dongbo peridotite massifs, SW Tibet: Insights into the style of mantle melting at the onset of Neo-Tethyan subduction

Cheng, Chien-Min; Zheng, Hangping; Kapsiotis, Argyrios; Liu, Weiliang; Lenaz, Davide; Velicogna, Matteo; Zhong, Ling; Huang, Qiangtai; Yuan, Yajuan; Xia, Bin

doi:10.1016/j.lithos.2018.10.023

Cited by 16 publications

(5 citation statements)

References 83 publications

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“…Moreover, our data indicate that there is no correlation between U-Pb age and crystal morphology or internal texture of the examined zircons. In addition, the existence of a single zircon age population in each rock specimen indicates that the investigated zircons were crystallized from the rock-forming melts and are unlikely of xenocrystic origin [13,44].…”

Section: Uranium-pb Dating Of Zirconsmentioning

confidence: 99%

Geochemistry and Geochronology of Ophiolitic Rocks from the Dongco and Lanong Areas, Tibet: Insights into the Evolution History of the Bangong-Nujiang Tethys Ocean

et al. 2019

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The Bangong-Nujiang Suture Zone (BNSZ) in central Tibet hosts a series of dismembered Jurassic ophiolites that are widely considered as remnants of the vanished Meso-Tethys Ocean. In this study we present new compositional, isotopic, and geochronological data from anorthosites and gabbros of the Dongco and Lanong ophiolites in order to test several hypotheses about the nature of subduction in the Bangong-Nujiang Tethys Ocean (BNTO) during the Mesozoic era. Uranium–Pb dating of magmatic zircons separated from the Dongco anorthosites yielded an (average) age of 169.0 ± 3.7 Ma. Zircons separated from the Lanong anorthosites and gabbros yielded U–Pb ages of 166.8 ± 0.9 Ma and 167.3 ± 1.1 Ma, respectively. Zircons separated from the Dongco and Lanong anorthosites have positive εHf(t) values (5.62–15.94 and 10.37–14.95, respectively). The Dongco anorthosites have moderate initial 87Sr/86Sr (0.703477–0.704144) and high εNd(t) (+6.50 to +7.91). The Lanong anorthosites have high (87Sr/86Sr)i (0.706058–0.712952) and εNd(t) in the range of −1.56 to +2.02. Furthermore, the Lanong gabbros have high (87Sr/86Sr)i (0.705826–0.706613) and εNd(t) in the range of −0.79 to +4.20. Most gabbros from Dongco and a few gabbros from Lanong show normal mid-ocean ridge basalt (N-MORB)-like primitive mantle (PM)-normalized multi-element patterns. In contrast, most gabbros from Lanong show U-shaped chondrite-normalized rare earth element (REE) profiles. The investigated gabbros are characterized by wide ranges of δEu {(Eu)N/[(Sm)N*(Gd)N]1/2} values (0.83–2.53), indicating that some of them are cumulative rocks. The trace element contents of all anorthosite samples imply that their composition was controlled by cumulative processes. The geochemical and isotopic compositions of the non-cumulative gabbros from Dongco (δEu: 0.95–1.04) and Lanong (δEu: 0.83–1.03) indicate that their parental melts were derived from melting of heterogeneously depleted, juvenile mantle reservoirs. These rocks have arc-related affinities, indicating that their mantle sources were influenced by minor inputs of subducted lithospheric components. Our preferred hypothesis for the origin of the non-cumulative gabbros from Dongco is that they were formed in a transient back-arc basin (BAB) setting in the middle-western segment of the BNTO, whereas our preferred scenario about the origin of the non-cumulative gabbros from Lanong is that they were generated in a forearc setting in the middle part of the BNTO. We conclude that both geotectonic settings were developed in response to the northward subduction of the BNTO during the Middle Jurassic.

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Section: Uranium-pb Dating Of Zirconsmentioning

confidence: 99%

Geochemistry and Geochronology of Ophiolitic Rocks from the Dongco and Lanong Areas, Tibet: Insights into the Evolution History of the Bangong-Nujiang Tethys Ocean

et al. 2019

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“…For BCR-2, many different values (−0.04, −0.02, −0.01, 0, 0.07, and 0.69) were measured by other authors [40,42,[44][45][46][47][48], while the LOI value in this study was −0.06. For BHVO-2, many different values ranging from −0.88 to 0.97 were measured by other authors [40,[42][43][44][45][46][47][49][50][51][52][53][54][55], while the LOI in this study was −0.55. For JH-1, the LOI in this study was 2.13, which is higher than the recommended value of 1.78.…”

Section: Accuracy and Precisionmentioning

confidence: 42%

Comparative Study of Three Mixing Methods in Fusion Technique for Determining Major and Minor Elements Using Wavelength Dispersive X-ray Fluorescence Spectroscopy

Zhang

Xue

Liu

et al. 2020

Sensors

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Accurate analysis using a simple and rapid procedure is always the most important pursuit of analytical chemists. In this study, a new sample preparation procedure, namely the shaker cup (SH) method, was designed and compared with two sample preparation procedures, commonly used in the laboratory, from three aspects: homogeneity of the sample–flux mixture, potential for sample contamination, and sample preparation time. For the three methods, a set of 54 certified reference materials (CRMs) was used to establish the calibration curves, while another set of 19 CRMs was measured to validate the results. In the calibration procedures, the matrix effects were corrected using the theoretical alpha coefficient method combined with the experimental coefficient method. The data of the major oxides (SiO2, TiO2, Al2O3, TFe2O3, MnO, MgO, CaO, Na2O, K2O, and P2O5) and minor elements (Cr, Cu, Ba, Ni, Sr, V, Zr, and Zn) obtained by wavelength dispersive X-ray fluorescence spectroscopy (WD-XRF) were compared using two derivative equations based on the findings by Laurence Whitty-Léveillé. The results revealed that the WD-XRF measured values using the SH method best agreed with the values recommended in the literature.

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“…Fields of MORB, oceanic island basalt, and global subducting sediment (GLOSS) fields are shown (Chauvel, Lewin, Carpentier, Arndt, & Marini, 2008; Hofmann, 1997; Nowell et al, 1998), Indian Ocean normal‐type MORB (N‐MORB) (Mahoney et al, 1998), Réunion hotspot (Bosch et al, 2008; Fisk, Upton, Ford, & White, 1988). Data of mafic rocks from Yarlung Zangbo Suture Zone (YZYZ) ophiolites (Cheng et al, 2018; T. Liu et al, 2018; Niu et al, 2006; Zhang et al, 2005, 2019; Zhang, Liu, Wu, Zhang, & Ji, 2016)…”

Section: Discussionmentioning

confidence: 99%

“…The Group‐II amphibolites exhibit ( 87 Sr/ 86 Sr) i values of 0.706103 to 0.706303, ( 143 Nd/ 144 Nd) i ratios of 0.512851 to 0.512936, and ε Nd (t) values of +5.81 to +7.47. As compared to Group‐I amphibolites, their initial Nd isotopic compositions show depleted nature and are indistinguishable (+5 to +10) (Figure 11) from those of mafic rocks in the Yarlung Zangbo Suture Zone ophiolites (Cheng et al, 2018; C. Zhang et al, 2016, 2019; F. Liu et al, 2015; T. Liu et al, 2018; Niu et al, 2006; S.‐Q. Zhang et al, 2005; C. Zhang et al, 2016).…”

Section: Discussionmentioning

confidence: 99%

Petrological and geochemical characterization of metamorphic sole rocks beneath the RasKoh ophiolite, western Pakistan: Implication for a Late Cretaceous supra‐subduction zone‐type forearc

et al. 2021

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Small, isolated outcrops of metamorphic sole rocks to the RasKoh ophiolite are exposed south‐east of the RasKoh Arc range, western Pakistan. These crop out as thin slices beneath the sheared serpentinites, and consist of amphibolites, epidote‐bearing amphibolites, and muscovite‐rich amphibolites with granoblastic, grano‐nematoblastic, and porphyroblastic textures. Geochemically, amphibolites present two compositional groups. Group‐I amphibolites are alkaline and enriched in light rare‐earth elements (LREE; LaN/YbN = 11.47–11.60) with Sr‐Nd isotopic compositions of (87Sr/86Sr)i = 0.705481–0.706128, (143Nd/144Nd)i = 0.512668–0.512672, and lower values of εNd(t) (+2.24 to +2.32). While, Group‐II amphibolites are tholeiitic with LREE‐depleted signatures (LaN/YbN = 0.88–1.31), (87Sr/86Sr)i = 0.706103–0.706303, (143Nd/144Nd)i = 0.512851–0.512936, and higher values of εNd(t) (+5.81 to +7.47). Primitive mantle‐normalized and other geochemical diagrams indicate that the protoliths for Group‐I amphibolites are oceanic island basalts (OIB). Conversely, Group‐II amphibolites are more akin to subduction‐related arc tholeiites with geochemical signatures, slightly enriched in large‐ion lithophile elements and with negative Nb‐Ta anomalies. The geothermobarometric results estimate that these rocks were metamorphosed at amphibolite facies at 690°C and 6.5 kbar. Alkaline volcanism is well documented from the other Mesozoic ophiolites of Neo‐Tethyan suture zones. We suggest that the OIB accreted to the base of the obducted plate at an early stage, whereas the island arc tholeiites (IAT) basalts metamorphosed and accreted to the base of the RasKoh ophiolite at a later stage. The OIB‐ and IAT‐type magmas as protolith of amphibolites suggest that the RasKoh ophiolite was emplaced in a supra‐subduction zone‐type forearc in Late Cretaceous (ca. 68–64 Ma).

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Geochemistry and geochronology of dolerite dykes from the Daba and Dongbo peridotite massifs, SW Tibet: Insights into the style of mantle melting at the onset of Neo-Tethyan subduction

Cited by 16 publications

References 83 publications

Geochemistry and Geochronology of Ophiolitic Rocks from the Dongco and Lanong Areas, Tibet: Insights into the Evolution History of the Bangong-Nujiang Tethys Ocean

Geochemistry and Geochronology of Ophiolitic Rocks from the Dongco and Lanong Areas, Tibet: Insights into the Evolution History of the Bangong-Nujiang Tethys Ocean

Comparative Study of Three Mixing Methods in Fusion Technique for Determining Major and Minor Elements Using Wavelength Dispersive X-ray Fluorescence Spectroscopy

Petrological and geochemical characterization of metamorphic sole rocks beneath the RasKoh ophiolite, western Pakistan: Implication for a Late Cretaceous supra‐subduction zone‐type forearc

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