The Xigaze ophiolite (Tibet): a peculiar oceanic lithosphere

Nicolas, Adolphe; Girardeau, J.; Marcoux, Jean; Dupré, Bernard; Wang, Xibin; Yougong, Cao; Zheng, Haixiang; Xiao, Xia

doi:10.1038/294414a0

Cited by 225 publications

(99 citation statements)

References 18 publications

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“…There are several subparallel tectonic belts, which from North to South include the Gangdese magmatic arc, a continental margin molasse belt, a fore-arc flysch belt, the YarlungZangbo suture itself, a Triassic flysch belt and a band of shelf sedimentary rocks along the northern margin of the Indian Block. Scattered along the suture zone are several ophiolites, which represent relics of Neotethyan oceanic lithosphere (e.g., Nicolas et al, 1981;Allegre et al, 1984;Girardeau et al, 1985;Wang et al, 1987;Zhou et al, 1996;Hao et al, 1999;Wang et al, 1999). The Dagzhuka ophiolite lies in the middle segment of the suture zone and represents an extension of the Xigaze ophiolite to the west.…”

Section: Introductionmentioning

confidence: 99%

“…However, these rocks are strongly depleted in Nb and Ta but enriched in Th and Rb, features characteristic of island arc lavas. Thus, the Dagzhuka ophiolite is believed to have formed in a supra-subduction zone environment, possibly a fore-arc basin.ophiolite has a well-preserved lithologic sequence ranging from mantle peridotite at the base to pillow lava at the top and thus provides an ideal environment in which to study the evolution of the Tethyan ocean basin (Nicolas et al, 1981;Girardeau et al, 1985;Wang et al, 1987).Although the ophiolite has been studied extensively, there is no agreement as to its origin or tectonic setting. For example, Girardeau et al (1985) suggested that it formed at mid-oceanic ridge whereas Wang et al (1999) favored formation in a small, multi-stage oceanic basin.…”

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confidence: 99%

“…ophiolite has a well-preserved lithologic sequence ranging from mantle peridotite at the base to pillow lava at the top and thus provides an ideal environment in which to study the evolution of the Tethyan ocean basin (Nicolas et al, 1981;Girardeau et al, 1985;Wang et al, 1987).…”

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Geochemistry and tectonic environment of the Dagzhuka ophiolite in the Yarlung-Zangbo suture zone, Tibet.

Xia

Chen

et al. 2003

Geochem. J.

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The Cretaceous Dagzhuka ophiolite lies in the middle segment of the Yarlung-Zangbo suture zone, Tibet, and has a well-preserved ophiolitic section including a mantle sequence, cumulate complex, diabase dyke swarm and basaltic lavas. Compared to the primitive mantle, tectonized peridotites in the Dagzhuka ophiolite are depleted in Al, Ca, Ti and high field strength elements, but relatively enriched in large ion lithophile elements (Rb, Ba, Th). They have U-shaped, chondrite-normalized REE patterns suggesting an early stage of depletion by partial melting, followed by enrichment from slab-derived fluids. These features support a model in which the mantle peridotites at Dagzhuka formed in a forearc setting. The diabases and basalts are low-K tholeiites depleted in LREE, with compositions similar to N-MORB. However, these rocks are strongly depleted in Nb and Ta but enriched in Th and Rb, features characteristic of island arc lavas. Thus, the Dagzhuka ophiolite is believed to have formed in a supra-subduction zone environment, possibly a fore-arc basin.ophiolite has a well-preserved lithologic sequence ranging from mantle peridotite at the base to pillow lava at the top and thus provides an ideal environment in which to study the evolution of the Tethyan ocean basin (Nicolas et al., 1981;Girardeau et al., 1985;Wang et al., 1987).Although the ophiolite has been studied extensively, there is no agreement as to its origin or tectonic setting. For example, Girardeau et al. (1985) suggested that it formed at mid-oceanic ridge whereas Wang et al. (1999) favored formation in a small, multi-stage oceanic basin. Here we report the results of extensive field and laboratory studies over the past decade and present a new interpretation of the ophiolite. New major and trace element data place important constraints on the tectonic setting of the Dagzhuka ophiolite and suggest that it formed in a supra-subduction zone environment.

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Section: Introductionmentioning

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Geochemistry and tectonic environment of the Dagzhuka ophiolite in the Yarlung-Zangbo suture zone, Tibet.

Xia

Chen

et al. 2003

Geochem. J.

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“…The Purang ophiolite massif is one of the most spectacular exposures of western extension along the Indus-Yarlung Zangbo Suture between the Himalayan passive margin and the Gangdise active margin, which is a mantle thrust sheet of more than 650 km 2 , extending NWW in the western Tibet (Nicolas et al, 1981;Yang et al, 2011).The Purang ophiolite consists mainly of spinel peridotites, including serpentinized harzburgite, minor lherzolite and chromite-bearing dunite associated with small amounts of olivine pyroxenite. Gabbro and diabase dike were observed intruding and cutting through spinel peridotites.…”

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Rodingite in the Purang Ophiolite and Its Geological Implication, Southwest Tibet

Kong

Chen

et al. 2015

Acta Geologica Sinica (Eng)

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The Yarlung Zangbo Suture Zone (YZSZ) separates the Lhasa block of the Eurasian plate to the north from the Indian plate to the south, along a ~2000km discontinuous E-W trending suture zone, several heterogeneous remnants of the Neo-Tethyan oceanic floor have been preserved from the subduction recycling. The Purang ophiolite massif is one of the most spectacular exposures of western extension along the Indus-Yarlung Zangbo Suture between the Himalayan passive margin and the Gangdise active margin, which is a mantle thrust sheet of more than 650 km 2 , extending NWW in the western Tibet (Nicolas et al., 1981;Yang et al., 2011).The Purang ophiolite consists mainly of spinel peridotites, including serpentinized harzburgite, minor lherzolite and chromite-bearing dunite associated with small amounts of olivine pyroxenite. Gabbro and diabase dike were observed intruding and cutting through spinel peridotites. Along the northern margin there is a mélange of serpentinized harzburgite, tectonically overlying upper Triassic-Cretaceous clastic rocks. Partly serpentinized harzburgite accounts for more than 80% of the ultramafic rocks. Lherzolite, dunite and olivine pyroxenite mostly occur as irregular blocks or bands within the harzburgite, some of which have clear boundaries with the host .Rodingites occur as lens, block or vein along the fracture in the south margin of the Purang ultramfic massif, and it is associated with relatively intense serpentinizated peridotite. Since the Purang ultramfic rocks suffered only weak to moderate serpentinization, rodingite only experienced early stage mineral assemblage of rodingitization (Li et al., 2007(Li et al., , 2008. Rodingite has intense crack texture and consists of amphibole, clinoziosite and chlorite. Accessory minerals are titanite and ilmenite. No relict primary minerals were found. Two generations of amphibole were found, the early one has edenitic composition, whiles the late amphiboles are Mghornblende, actinolite to tremolite, formed during rodingitization. Epidote-group minerals are clinozoisites and chlorite is clinochlore in composition.Rodingites from the Purang area contain average SiO 2 ~48.65%, CaO ~ 9.89%, TFe 2 O 3 ~4.34%, Na 2 O + K 2 O < 2%. Additionally, they have extraordinarily high MgO ~23.92% and low TiO 2 < 0.02% in average. Bulk-rock recalculation indicates the protolith of rodingite is a dark olivine gabbro. Loss of ignition (LOI) varies from 1.83-3.23 wt%, reflecting weekly degrees of rodingitization.The chondrite normalized composition of the rodingite generally displays a slightly depleted LREE pattern. The multi-element diagram normalized to primary mantle presents that all samples are enriched in U, Pb and Sr anomalies, but almost depleted in other trace elements with negative anomalies in part high-field strength elements (e.g. Nb, Ti, Y). The ∑REE of rodingite is much lower than that in the gabbroic diabase, but higher than that of spinel-bearing ultramafic rocks in the Pruang massif.As conclusions, the Purang rodingite shows a mantle source p...

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Two‐layered oceanic lithospheric mantle in a Tibetan ophiolite produced by episodic subduction of Tethyan slabs

Xiong

Griffin

Zheng

et al. 2017

Geochem Geophys Geosyst

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The origin and evolution of the Yarlung Zangbo ophiolites (South Tibet, China) is the key to the tectonics of the Neo‐Tethyan Ocean between Greater India and Asia and the underlying upper mantle dynamics. This study presents a detailed investigation of the Zedang ultramafic body (comprising a harzburgitic and a lherzolitic domain) in the eastern Yarlung Zangbo Suture. Major‐element compositions and Ti, Y, and HREE concentrations in peridotites and their minerals indicate that the harzburgites experienced higher degrees of melting than the lherzolites (∼13–19% versus ∼7–12%). The overall enrichment of LREE, Zr, and Sr in harzburgites and their clinopyroxenes suggest that the harzburgites were pervasively metasomatized (cryptically) by silicate melts. The harzburgites also record local strong metasomatism close to melt channels. Nd isotopes indicate that both metasomatic agents were derived from forearc basaltic magmas that intruded the harzburgites at ∼130–120 Ma. The lherzolites did not experience such metasomatism. Thermometry shows that the harzburgites experienced a thorough, lower‐temperature reequilibration process in lithosphere, while the lherzolites rapidly accreted from the asthenosphere and preserved high equilibration temperatures (up to ∼1320°C). Comparable enrichment in fluid‐mobile elements and radiogenic Sr‐isotope compositions in both harzburgitic and lherzolitic pyroxenes reflect slab‐fluid infiltration into both mantle domains. All the evidence and the presence of subduction‐related chromitites in the harzburgites suggest that the Zedang harzburgites formed in a possibly Jurassic mature subduction system, while the lherzolites accreted later in an early Cretaceous forearc during subduction initiation. The two‐layered lithospheric mantle reflects the episodic subduction of the Tethyan slabs.

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The Xigaze ophiolite (Tibet): a peculiar oceanic lithosphere

Cited by 225 publications

References 18 publications

Geochemistry and tectonic environment of the Dagzhuka ophiolite in the Yarlung-Zangbo suture zone, Tibet.

Geochemistry and tectonic environment of the Dagzhuka ophiolite in the Yarlung-Zangbo suture zone, Tibet.

Rodingite in the Purang Ophiolite and Its Geological Implication, Southwest Tibet

Two‐layered oceanic lithospheric mantle in a Tibetan ophiolite produced by episodic subduction of Tethyan slabs

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