In order to study the distribution of fractures controlled by layer curvature, fold and fault-related folds in East Kuqa, including one anticline (Biyoulebaoguzi Anticline profile), one fault-bent fold (Kezilenuergou Faultbent Fold profile) and one drag fold (Yangxia Coal-mine Drag-fold profile), are selected as investigating profile, and density of their structural factures and the layer curvature of middle-lower Jurassic and Triassic are measured. The result shows that the layer curvature has an effect on the fracture density; structural fractures are easier to be developed in the layers with larger curvature compared with those with smaller one within the same stratum. Besides, there is a positive linear relationship between fracture density and layer curvature. The mechanics of layer curvature’s effect on structural fracture from angle of solid mechanics is discussed: fracture density is tightly related to stress distribution, and stress is proportional to curvature in bent beam model; hence, a positive linear relationship exists between the fracture density and layer curvature, which is applied to both elastic and plastic folds.

By the use of well logging data, the tectonic fracture porosity was calculated, the influence of tectonic fractures to Young’s modulus was quantitatively described with the theory that the development of tectonic fractures would decrease the value of Young’s modulus, and the “Fracture Evaluation Indicator ( f )” was first proposed to evaluate the levels of tectonic fracture development. The development evaluation of Ahe low porosity and low permeability sandstone fractures was carried out with the fracture evaluation indicator, and the evaluating results showed that the Well Yinan-2 areas and the glutenite with mudstone segment of Ahe formation are the most tectonic fracture developed places in the horizontal and vertical plane of Yinan-Tuzi areas respectively.

Rb-Sr isochronal ages and chemical data are reported for the Alxa alkaline-rich intrusive rocks, western Inner Mongolia, China. These alkaline-rich intrusive rocks have elevated contents of total alkali w(K₂O+Na2O) with an average of 12.70%. They are consisting mainly of K-feldspar, quartz, plagioclase, biotite and/or amphibole. Rb-Sr whole rock-minerals ages determination indicates that the isochronal ages are(250±18) Ma and (213.0±9.8) Ma for Suhaitu and Wenduerhao intrusion, respectively. The dated isotopic ages demonstrate that the Alxa alkaline-rich intrusive rocks belong to Indosinian alkaline magma activity. The similarities and differences of the alkaline-rich intrusive rocks distributed in the Alxa Fault Block and those distributed along the northern margin of the North China Block and the Tarim Block are compared and discussed. The authors deduce that during late Palaeozoic-Indosinian period, the Alxa Fault Block and the North China Block may be located in the same geodynamic system, but the Tarim Block may be located in a different geodynamic system.