The Middle Neoproterozoic meta-gabbro from the North Lhasa terrane of Tibet and its geological implications

The Precambrian evolution of the ancient terranes in the Tibetan Plateau and their roles in the assembly of Gondwana supercontinent remain unclear. This paper reports SHRIMP zircon U-Pb dating and zircon Hf isotopic analysis data of the meta-gabbro from the Nyainqentanglha Group of North Lhasa terrane, Tibet. Zircon U-Pb dating yielded a weighted mean age of 663±7Ma, which represents the crystallization age of the protolith of meta-gabbro and is reported for the first time for the North Lhasa terrane. The meta-gabbro has low ε_Hf(t) values (-1.5 to +2.3), suggesting an enriched magma source. Considering previous Precambrian studies in the North Lhasa terrane, the authors hold that the meta-gabbros were probably formed in an orogenic setting. The Nyainqentanglha Group is actually composed of a suite of tectonic slices with different sizes, ages, and petrogenesises. Thus, it should be disassembled in the future research. The metamorphic and magmatic records in the Nyainqentanglha Group are comparable with those of the East African orogen, suggesting that the North Lhasa terrane probably originated from the northern segment of the East African orogen during the assembly of Gondwana supercontinent.