This paper reports a paleomagnetic study of Jurassic rocks from the Ordos Basin in the North China Block (NCB). A recent remagnetization and a high‐temperature and/or high‐coercivity component with dual polarities have been isolated. The Middle Jurassic pole (74°N, 233°E, A95=5°) is roughly consistent with previous results, and the Lower Jurassic pole (82°N, 286°E, A95=7°) is located between the late Triassic and Middle Jurassic poles. These results, combined with paleomagnetic results from adjacent blocks, suggest that 1) the pole for the NCB suffered an angular displacement of 47°+/− 8° between the late Triassic and Middle Jurassic, 2) the SCB underwent final accretion to the NCB in the Middle Jurassic, and 3) accretion of the NCB to Siberia was not complete until the late Jurassic and possibly even until the early Cretaceous.

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S U M M A R YA palaeomagnetic study has been made of samples collected from the Permo-Triassic type section near Taiyuan, Shanxi Province in the North China Block. No results were obtained from the Upper Carboniferous Shanxi and Taiyuan Formations. Results from the Permian Lower and Upper Shihezi and Shiqianfeng Formations and from the Lower Triassic Liujiagou Formation were restricted mainly to the red shale and red mudstone horizons that were preferentially sampled for this study. After thermal demagnetization, the following pole positions were obtained: Lower Permian (Lower Shihezi Formation, N = 11 samples) 20.9"N, 1.4"E with d p = 6.1" and dm = 12.2"; Upper Permian (combined Upper Shihezi and Shiqianfeng Formations, N = 89 samples) 47.8"N, 357.4"E with d p = 2.3" and dm = 4.3"; Lower Triassic (Liujiagou Formation, N = 25 samples) 50.0°N, 351.O"E with d p = 3.7" and dm = 7.0". The sequence crosses the younger boundary of the Permo-Carboniferous reversed (Kiaman) superchron, and the polarity sequence observed suggests that this superchron ended in mid-Ufimian times. A minimum of 13 polarity zones (seven normal and six reverse) then follow before the Permo-Triassic boundary. This is in excellent agreement with currently available observations worldwide.

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Summary A palaeomagnetic study of Lower Cretaceous continental sediments from the south‐southwestern part of the Ordos basin, North China block (NCB), has been carried out. Stepwise thermal demagnetization was used to isolate magnetic components. The low‐temperature component is generally removed between 200 °C and 350 °C and corresponds to the Earth's present field direction. A high‐temperature component of magnetization, with two polarities, was defined from 10 sites with D = 16.4°, I = 50.5° (K= 50.8, α95= 6.8°). The corresponding pole position is located at 75.8°N, 208.7°E (dp= 6.1°, dm= 9.1°). This Lower Cretaceous pole compares well with the hairpin loop of the Eurasian synthetic APW path (Besse & Courtillot 1991) that is inferred from the North American, Eurasian, African and Indian plates. The available late Mesozoic palaeomagnetic data from the NCB and adjacent South China block (SCB) are reviewed. Comparison of these data suggests important intraplate deformation: the area to the east of the Tancheng‐Lujiang fault may have undergone local clockwise post‐Cretaceous rotations of 10‐29° relative to the stable western craton of the NCB. The data also indicate that no palaeomagnetically significant eastward movement of the SCB with respect to the NCB and Eurasia occurred after the Cretaceous.

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The Central Asian Orogenic Belt (CAOB), which formed by closure of the Paleo-Asian Ocean, is one of the largest Phanerozoic accretionary orogens on Earth. However, the timing of final closure of the Paleo-Asian Ocean remains debated. Here we present new zircon U-Pb dating, oxygen fugacity estimates, and whole-rock geochemical and Sr-Nd isotopic data from intermediate and felsic intrusive rocks in the Chunhua area of NE China to constrain their petrogenesis and assess the tectonic implications for the evolution of the eastern CAOB. Zircon U-Pb dating indicates that the intrusive rocks formed in the late Permian (257-261 Ma). Based on their chemical compositions, two groups of rocks can be identified. Group Ι consists mainly of dioritic rocks (e.g., gabbroic diorites, diorites and tonalites) with relatively low SiO 2 but high MgO contents and Mg# values. Petrological and geochemical characteristicsshow that Group Ι rocks were formed by mixing of mantle-and crust-derived magmas.Mafic microgranular enclaves within Group Ι rocks have high MgO contents (up to 9 wt%) and depleted isotopic compositions (ε Nd (t) = +4.3 to +7.2), and probably represent mafic end-member magmas derived from a metasomatized lithospheric mantle, which subsequently were injected into the felsic crustal magmas. In contrast, Group ΙI rocks are mostly granodiorites characterized by high SiO 2 and low Mg# values, with high Sr/Y and La/Yb ratios. These rocks were probably generated by partial melting of mafic lower crust with little or no addition of mantle materials.Trace element modeling suggests that intracrustal differentiation was dominated by hornblende fractionation and caused the high Sr/Y and La/Yb signatures of Group ΙI

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