Early Cretaceous potassium-riched alkaline volcanic rocks were discovered in the Suhongtu area, Inner Mongolia. These volcanic rocks display higher total alkaline contents (K₂O+Na₂O=5.20%~8.92%), K₂O/Na₂O (K2O/Na2O=0.59~1.03) and TiO₂ (1.59%~2.05%) and characteristics of shoshonites series rocks. Chondrite normalized rare earth element patterns and primitive mantle normalized trace element patterns show slightly positive and negative Eu anomalies (δEu=0.88~1.11) and the enrichment of large ion lithophile elements (LILE), light rare earth elements (LREE) and high field strength elements (HFSE). Suhongtu volcanic rocks show similar geochemical characteristics to those of Siziwangqi and Southern Baiyun’ebo volcanic rocks. These volcanic rocks did not experience obvious contamination of crustal materials. Negative Nb and Ta anomalies probably imply the influence of the subducted slab of Paleo-Asian Ocean crust. Trace elements and isotopic analysis indicate that the Suhongtu and Siziwangqi shoshonites magmas were derived from EMⅠ enrichmental asthenosphere mantle altered by materials from the subducted slab of the Paleo-Asian Ocean crust, and the Southern Baiyun’ebo volcanic rocks was from a less-degree enriched source. However, their petrogenesis is similar to the depleted mantle source with various degree of enrichment. In combination with the regional geology, the middle and western part of the north margin of Northern China Craton (NCC), along which Siziwangqi, Southern Baiyun’ebo and Suhongtu volcanic rocks distributed, probably showed an similar extensional environment after orogenic period in Early Cretaceous. After the closure of the Paleo-Asian Ocean in Late Triassic, a NS-trending compressive process developed in the north margin of NCC, which led the thickening of crust and the delamination of lithosphere. Then the remelting of the subducted slab of the Paleo-Asian Ocean crust, and the melt resulted in enrichment of the depleted asthenosphere mantle, and the upwelling and partial melting of the enriched mantle asthenosphere mentle formed EW-distributed Early Cretaceous shoshonites.

To deepen the understanding on tectonic evolution of Beishan Moutain, granite pluton which lies in the north of Qiaowan, northern margin of Dunhuang block (south belt of Beishan Mountain), Gansu province, is studied in geochronology and geochemistry. The hornblende granite contains a LA-ICP MS zircon U-Pb aged at 303.7±2.4 Ma. Its ε_Hf(t) value varies from -1.2 to 5.8, ε_Nd(t) value is high (-0.40 to -0.06), and (⁸⁷Sr/⁸⁶Sr)_i (0.704524 to 0.705062) is relatively low. The pluton apparently belongs to sub-alkline and high-K cal-alkaline series (K₂O is 4.09% to 5.58%, K₂O/Na₂O is 1.34 to 2.07) and shows as I-type granite with metaluminous-peraluminous characteristics for A/CNK is between 0.92 and 1.04. The hornblende granite pluton has LILE enrichment, especially rich in Pb, Rb, Th, and U, depleted in HFSE (Nb, Ta) obviously in spidergram. It also has a rich LREE and flat HREE in REE patterns with no or extremely weak Eu anomalies (δEu = 0.67 to 1.17). From the ε_Hf(t), ε_Nd(t) values and geochemical characteristics, it can be concluded that the pluton is a mixture of crustal and mantle derived magma. The mantle derived magma may be directly from anatexis magma in deep mantle and then underplate below the continental crust. Based on regional geology and the geochemical characteristics, the hornblende granite pluton in the north of Qiaowan was formed during post-collision period, which suggests the collision of Beishan Mountain is already finished in late Carboniforous.

The Permian granitoids are widespread in Urad Zhongqi, Inner Mongolia, and are located on the middle segment of the northern margin of the North China Plate. The granitoids consist mainly of quartz diorite and granodiorite. They show a calc-alkaline I-type affinity and are characterized by dominant biotite in dark mineral, low A/ CNK (0. 77- 1. 04) . They have the geochemical characteristics similar to adakites by ≥56% SiO₂ ( 55. 70% -68. 65% ) , ≥15% Al₂O₃ ( 15. 32% -22. 87% ) , low Y ( 2. 82-20. 89 μg/ g) and Yb ( 0. 25-2. 24 μg/g) , enrichment of LILE ( large-ion lithophile elements) and LREE (e.g. Ba = 627-2124 μg/ g, Sr = 327-968 μg/ g, Sr/Y = 32. 2-211, ( La/Yb)_N = 5. 83-81. 1) , and mostly evidently positive Eu anomalies (δEu = 0. 63-2.25 ). They are interpreted as post-collisional calc-alkaline granitoids, formed mainly by partial melting of the overthickened continental lower crust due to underplating of EM1-type mantle-derived basaltic magma. Biotite ⁴⁰Ar/³⁹Ar ages of Beiqigetao Pluton, Talabuji Pluton, Ageru Pluton and Baoerhantumiao Pluton are respectively 260 ±3, 258 ±1, 260 ±3 and 258 ±2 Ma, which indicate they were emplaced during the Late Permian.

The study of Neoarchean S-type granite, with obvious tectonic significance, which lies in Hejiao area, Darhan Muminggan Lianheqi, Inner Mongolia, in major elements, trace elements and SHRIMP zircon U-Pb geochronology provided further evidence for understanding the nature of tectonic setting of the northern margin of North China plate at the end of Neoarchean. The major elements features of Hejiao granite indicate that it belongs to cal-alkaline series with strongly peraluminous characteristics and Rittman index σis between 0. 54 and 0. 57. The granite has high total rare earth elements (REE) values(243.8- 427. 1 μg/g), and enriches light REE relative to the heavy ones, and has negative anomalies characteristics in Eu ( ( La/ Yb)_N = 14. 88-18. 18, Eu^* / Eu = 0. 31- 0. 65) . In addition, it depletes high field strength elements( HFSE) , such as Nb, Ta, Zr, Hf and Ti. The trace elements characteristics of Hejiao granite reflect that it is formed under post-collisional tectonic setting and it is from normal thick continental crust in low pressure-high temperature conditions, which are similar to the formation conditions of Lachlan fold belt in Australia. The SHRIMP U-Pb zircon age of Hejiao granite is 2556 ±8 Ma. Strongly peraluminous S-type granite of Hej iao indicates that, in the end of Neoarchean, a continent-continent collision event probably occurred at the middle segment of north margin of North China plate, and that the sanukite with the same age in Guyang area, was possibly formed at post-collisional tectonic setting rather than subduction zone.

The xenolith-bearing Miocene basalts in Siziwang County, Inner Mongolia, are characterized with high-K (1. 16 %

Two types of cumulate gabbros are exposed in Wulatezhongqi area, Inner Mongolia, including amphibole gabbros and olive gabbros. The major petrogenetic minerals in the Wengeng gabbros are olive, pyroxene, plagioclase and hornblend. Based on electron microprobing analysis (EMPA), pyroxene is diopside and plagioclase is bytownite of An86 in amphibole gabbros. They also show geochemical characteristics of enriched in LILE (K，Rb，Sr，Ba), and depleted in HFSE (Nb，Ta，Zr). According to the diagrams of Al₂-TiO₂, Wo-En-Fs and An-Mg′, the amphibole gabbros are suggested to be generated at an island arc. Whereas olivine of the olive gabbros belongs to chrysolite with high Fo74, plagioclase is bytownite of An80, and pyroxene is enstatite. The geochemistry of the olive gabbros is characterized by low SiO₂ and high MgO contents, enriched in LILE (K，Rb，Sr，Ba) and LREE, and unfractionation in HFSE. All above evidences suggest that the olive gabbros are derived from a depleted mantle source in a mid-oceanic ridge or an island arc setting. According to the diagrams of Wo-En-Fs and An-Mg′, the olive gabbros are suggested to be formed in a back-arc basin setting. The formation of Wengeng gabbros may be related to the subduction of the Paleoasian ocean plate. The Wengeng gabbros should be an important lithological record of the Paleoasian ocean closure.

The early Cretaceous basalts in the Siziwangqi area, Inner Mongolia, are characterized by shoshonite. These rocks are enriched in large ion lithophile elements (LILE),light rare earth elements (LREE), and depleted in high field strength elements (HFSE). The chemical characteristics are similar to the oceanic island basalt (OIB). Trace element ratios such as Rb/Nb, K/Nb, Zr/Nb, Th/Nb and Th/La are consistent with the EM1-OIB geochemical signatures. Their ²⁰⁶Pb/²⁰⁴Pb, ²⁰⁷Pb/²⁰⁴Pb and ²⁰⁸Pb/²⁰⁴Pb ratios are in the ranges of 17.18 to 17.81, 15.40 to 15.50 and 37.54 to 38.05, respectively, showing the EM1 geochemical signatures. The progressive enrichment of lead concentration with almost unchanging Pb isotopic ratios, preclude the possibility that the magmas were contaminated by crustal materials. The shoshonitic parental magma was derived from the small degree decompression melting of asthenosphere mantle. The Siziwangqi shoshonite is the product of lithospheric thinning of the North China craton.

Siziwangqi of Inner Mongolia is located on the north margin of North China Craton, the junction of North China Craton and Siberia. Granulite xenoliths are found there in Cretaceous basalt. These xenoliths are mainly plagioclase-pyroxenite. The K-Ar isotopic dating of the basalt is between 108.6--128.4 Ma. These granulite xenoliths are not only important for understanding the composition and interaction between the lower lithosphere and the mantle, but also direct evidence for Mesozoic delamination of North China Craton.

There is a genetic relationship between the granites and their tectonic setting. Because activity of magma is controlledby the tectonic environment. In every stage of crustal evolution, the component of granites shows out a regular tendency, in which the major, trace and rare earth elements were changed. A serial methods were set up by mathematical models with granites in the typical tectonic environments. There are two diagrams for the tectonic interpretation especially for extentional environment. One is AFC diagram which is a reflection of major element in various grantic rocks. Another is F1-F2 diagram which is set up by step-discriminatory analysis. The methods to calculate the parameter ofdiagrams are showed in the paper. They can be used to discriminate the tectonic environment in which the granite sets.