Based on geologic, seismic and drilling data of basins in China, the basic types of "truncation and onlap" unconformities are examined and their temporal and spatial variation and geologic significances are explored. The "truncation and onlap" unconformities and superimposing styles of overlying and underlying strata vary under different tectonic settings. Under extensional settings, there are three basic superimposing styles and unconformities, such as parallel superimposing style and unconformity with breaking outward, parallel superimposing style and unconformity with breaking inward, as well as superimposing and unconformity style with rotation. Under compressional settings, there are four basic types, such as overlap superimposing style and unconformity on fold, syn-depositional fold superimposing style and unconformity, anticline-syncline superimposing style and unconformity, as well as superimposing style and unconformity in overlap-filling incised valley on top of folds. "Truncation and onlap" unconformities always superimposed each other in space, and exhibit three kinds of superimposed unconformities, i.e., superimposed unconformities formed under continuous uplifting, under transition of uplifting, and under propagation of deposition center. They may also change with time too, i.e., tilting, rotating, folding, and migration. Controlled by the migration of basin depocenters, it is shown that there are unconformities formed under the transition of paleogeomorphy or subsidence center, under the migration of fault-sag, and under the slipping of detachment fault. "Truncation and onlap" unconformities are important positions for traps and significant pathways for hydrocarbon migration, and they are favorable sites for ore deposit and resources occurrence.
New whole-rock major and trace elements, and zircon U Pb and Hf-Nd isotope compositions are reported for the Karamay dikes, enclaves, and host granites in the West Junggar, NW China. Zircon U -Pb dating of the l（aramay pluton yields an age of 300.7 ~ 2.3 Ma for the enclave and 300.0 ~ 2.6 Ma for the host granite, which was intruded by dike with an age of 298 Ma. The host granites exhibit relatively low SiO2 contents and A/CNK and Ga/Al ratios, low initial 87Sr/86Sr ratios （0.703421 0.703526） and positive eHf（t） （5.5--14.1） and eNd（t） （7.3--8.1） values with a young model age, suggesting that they are I-type granites and were mainly derived from a juvenile lower crustal source. The enclaves and dikes belong to an andesitic calc-alkaline series and have high MgO concentrations at low silica content and positive eHf（t） （7.6--13.2, 14.2--14.9） and εNd（t） （6.8-8.3, ~6.9） values. They are enriched in LILEs （Rb, Ba and U） and LREE and depleted in HFSEs （Nb and Ta） with insignificant negative Eu anomalies, indicating that the melts were derived from an enriched lithospheric mantle modified by subducted oceanic crust-derived melts and minor fluids, followed by fractional crystallization. The Karamay host granites and enclaves are of mixed origin and are most probably formed by the interaction between the lower crust-and lithospheric mantle-derived magmas, and were intruded by the unmixed dikes subsequently. The upwelling mantle through a slab window in an island arc environment might have triggered partial melting of the lithospheric mantle and its subsequent interaction with the granitic magma, further suggesting that the ridge subduction played an important role in the crustal growth of West lun^gar.
In January 2010, the Suining Ms5.0 earthquake occurred in central Sichuan Basin, with the epicenter in Moxi-Longnvsi structural belt and a focal depth of 10 km. Based on structural interpretations of seismic profiles in this area, we recognized a regional detachment fault located at a depth of 9-10 km in the Presinian basement of the Suining area, transferring its slipping from NW to SE orientation. This detachment fault slipped from NW to SE, and underwent several shears and bends, which caused the basement to be rolled in and the overlaying strata fold deformation. It formed a fault-bend fold in the Moxi area with an approximate slip of 4 km. Correspondingly, the formation of the Moxi anticline is related to the detachment fault. With the earthquake＇s epicenter on the ramp of the detachment fault, there is a new point of view that the Suining earthquake was caused by re-activation of this basement detachment fault. Since the Late Jurassic period, under the influence of regional tectonic stress, the detachment fault transfered its slip from the Longmen Mountains （LMS） thrust belt to the hinterland of the Sichuan Basin, and finally to the piedmont zone of southwest Huayingshan （HYS）, which indicates that HYS might be the final front area of the LMS thrust belt.
LU RenqiHE DengfaJOHN SuppeMA YongshengGUAN ShuweiSUN YanpengGAO Jinwei
