| PDF: | |
| Time: | 2016 |
| Journal: | Acta Petrologica Sinica |
| Volumn: | 32 |
| Issue: | 4 |
| Pages: | 1101-1113 |
| Type: | SCI |
| Author: | Yanquan Wang,Deyou Sun,Junfeng Shan,Jun Li,Yulong,Huang,Siwei Li |
Abstract: | Liaohe segment located in the transitional zone of Tan-Lu fault, is mainly composed of Paleogene volcanic-sedimentary rock series with a depth of 7000m. We conducted detailes studies on 7 wells of Shahejie formation. The results reveal that the Eocene volcanic rocks are mainly composed of basalt rocks and trachytic rocks, with SiO2 contents varying from 45.20% to 59.55%, which were dominated by alkaline lavas. Basaltic rocks were barely rich in Ti, not lack in Nb, Ta. Trachytic rocks show geochemical affinities similar to basalt rocks but depleted in Sr, P and Ti. They have similar Sr-Nd isotopic compositions. Basalt rocks have very enriched isotope characteristics with ISr=0.7033~0.7042, εNd(t)=3.56~5.86,which is consistent with the isotope composition of trachytic rocks (ISr=0.7035~0.7045, εNd(t)=3.25~4.46). Their Sr-Nd isotopes were similar with OIB. Based on the comprehensive studies, we suggested that Eocene volcanic rocks were the product of partial melting of mantle wedge replaced by slab-derived fluid, which intruded above in the back-arc extensional condition. Two distinct rocks generate from magma through differentiation in the magma chamber. The change from destructive settings in Mesozoic to a continental rift environment in Paleogene may be derived from the interaction between Asia plate and Pacific plate. In this process, the large-scale strike-slip movements of Tan-Lu fault controlled the contemporary asthenosphere-derived volcanicity. |