40Ar/39Ar Ages of the metamorphic rocks and basalts in E،¯rou area of Shuanghu, northern Xizang and its significance

Category Petrology
Group GSI.IR
Location International Geological Congress,oslo 2008
Author Zhang, Yuxun۱; Wang, Liquan۲; Pan, Guitang۲; Zhu, Dicheng۲
Holding Date 20 September 2008

Actinolite and altered-pyroxene phenocryst, severally separated from the chlorite-actinolite schist and pillow basalt in the E،¯rou area of Shuanghu located in the eastern part of the Shuanghu-Longmuco suture zone, respectively yield well-defined 40Ar/39Ar plateau ages of 235.9،ہ2.6Ma and 232.5،ہ2.4Ma. Both ages, being the unexceptionable correspondence, are interpreted to date the tectonothermal event of the subducting-collision along the Shuanghu-Longmuco suture zone. The subducting-collision in the Qiangtang region made the most part of the Shuanghu-Longmuco suture zone and its northern flank (i.e. the northern Qiangtang basin) to be translated the foreland basin during the late Middle Triassic to early Late Triassic, and the regional unconformity located the bottom of the Upper Triassic and the basal conglomerate above it are considered to be the important marks of the geological record for the collision. The protolith of the chlorite-actinolite schist are mainly the volcanic-sedimentary rocks with enrichment in the basalt. The chlorite-actinolite schist and the altered pillow-basalt, obviously characterized by being high in TiO2, P2O5 and MgO and LREE-enriched patterns with negative Eu anomalies and tumescence patterns for trace elements with enrichment in Nb, Ta and Ti, take typically on character of the OIB-type alkaline basalt.