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Discontinuous ophiolites within the Indus–Tsangpo suture zone (ITSZ) in southern Tibet represent remnants of Neo‐Tethyan oceanic lithosphere, which are considered to have formed during the late Jurassic to early Cretaceous. We report field observations, petrological and geochronological data for some mafic intrusions in a tectonic mélange in the southern ophiolitic belt of the western ITSZ. Zircon from a gabbro yields an age of 243 ± 1 Ma with εHf(t) values of +7.9 to +13.2. Rare earth element (REE) pattern of this rock resembles that of normal mid‐ocean ridge basalt. We suggest that such gabbro and surrounding mafic–ultramafic rocks represent the remnants of middle Triassic oceanic lithosphere in the ITSZ. Our findings indicate that the Neo‐Tethys Ocean between India and the Lhasa terrane existed from at least the middle Triassic, contrasting with the commonly held view that the Neo‐Tethys Ocean opened along the northern edge of Gondwana during the late Triassic–early Jurassic. [ABSTRACT FROM AUTHOR]

Discontinuous ophiolite suites along the Yarlung Zangbo suture zone (YZSZ) in southern Tibet representing remnants of the Neo‐Tethyan oceanic lithosphere are considered to be formed between Late Jurassic and Early Cretaceous. Older ophiolite or ophiolitic mélange (e.g. Triassic) to reveal the initial evolution the Neo‐Tethyan ocean within the YZSZ have rarely been documented so far. The western YZSZ extending from the Saga to Ladakh area are composed of the northern ophiolitic sub‐belt, the Zhongba terrane and the southern ophiolitic sub‐belt. In this study, we document structural, petrological and geochronological data of mafic intrusions from the Mayoumu massif in the southern ophiolitic sub‐belt of the western YZSZ. Two lithos‐tectonic sub‐units, the southern ophiolitic complex and the northern ophiolitic mélange, are recognized in the Mayoumu massif in terms of structural pattern and petrology. LA‐ICP‐MS zircon U‐Pb dating of gabbro from the ophiolitic mélange yields an age of 243 ± 1 Ma with zircon ∊Hf(t) values of +7.9 to +13.2. Two samples of diabase samples from the ophiolite yield ages of 131±1 Ma and 124±1 Ma with zircon ∊Hf (t) values ranging from +10.8 to +15.0 and +12.3 to +15.4, respectively. Geochemically, rare earth elements (REEs) patterns show that these mafic intrusions are similar to those of the normal mid‐ocean‐ridge basalt (N‐MORB). Enrichment of fluid‐mobile elements (e.g. Rb and Ba) and depletion of Nb, and Ta suggest that these intrusions were possibly originated from melting of a depleted mantle source influenced by subducted slab. Our data strongly confirms that the Neo‐Tethyan ocean between the Lhasa terrane and Gondwana had been existed since the Middle Triassic at least. The ages of the two diabases from the ophiolitic complex reveal that mafic magma activities within the Neo‐Tethyan ocean could be as a continuing process during 120–130 Ma. Emplacement and preservation of older ophiolitic recorder during evolution of the Neo‐Tethyan Ocean may be closely related to the occurrence of the Zhongba micro‐terrane within the western YZSZ. [ABSTRACT FROM AUTHOR]