Zircon U-Pb age and Hf isotope of intrusive rocks from the Yawa area in the west part of southern Lhasa terrane, Tibet

The Lhasa terrane developed widespread magmatism along its southern margin in the Mesozoic to Cenozoic Period. However, relative small number of studies has conducted for the magmatic rocks from the west part of the southern Lhasa terrane, especially for the Mesozoic magmatic rocks. This contribution presented a study of zircon U-Pb age and Hf isotope for the newly found Mesozoic to Cenozoic intrusive rocks from the Yawa area in the west part of southern Lhasa terrane, and identified Late Triassic gabbro and dioritic porphyrites (210 similar to 208Ma), Late Jurassic porphyritic monzogranites (ca. 155Ma) and Eocene granitic porphyry (ca. 50Ma). The Late Triassic gabbro and dioritic porphyrite have highly radiogenic zircon Hf isotopic compositions with eHf(t) values of +1.9 similar to +6.2 and-3.0 similar to +7. 4, respectively; while the Late Jurassic porphyritic monzogranite and the Eocene granitic porphyry show low initial zircon Hf isotope values of epsilon(Hf)(t) varying in ranges of- 10. 0 similar to -5. 2 and- 7. 9 similar to -2. 7, respectively, and their corresponding crustal model ages, which can be divided into two groups of 1534 similar to 1836Ma and 1297 similar to 1624Ma, respectively, indicate the existence of the recycled Paleoproterozoic and Mesoproterozoic crustal materials, respectively. In combination with literature data, the Yawa-Dajiaco area underwent obvious crustal growth due to the subduction of Neo-Tethyan ocean. The generation of juvenile crust exhibit gradient trends of increase both from Mesozoic to Early Cenozoic and from inland to trench.