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The Shahongshan pluton is located at the junction of Gansu Province and Inner Mongolia, which is at the intersection of the North China plate, the Tarim plate and the Kazakhstan plate. In addition, the tectonic magmatic activity is widely distributed. In this paper, the LA-ICP-MS zircon U-Pb dating, petrology, major and trace element analysis were carried out on the rocks of Shahongshan pluton, including granite porphyry and syenogranite, in order to unravel the regional intrusion age, rock genesis and the tectonic evolution of the Beishan orogenic belt. LA-ICP-MS Zircon U-Pb dating show that the weighted average age of the granite porphyry and syenogranite was (294.7±4.0) Ma, and (284.2±4.0) Ma, respectively, indicating that they formed in Early Permian. Petrological geochemical analyses show that granites of the Shahongshan pluton belong to calcium-alkaline to high potassium-calcium alkaline rock series, which are characterized by high silicon (74.79%～76.28%), alkali-rich (6.01%～8.30%), and aluminous (A/CNK=1.40～1.89). The total amount of rare earth elements was high, with enrichment in the light rare earth element (LREE; average 251.60×10−6) and depletion in the heavy rare earth element (HREE; average 45.52×10−6). The standardization curve of chondrite meteorite was significantly right-tilted, the LREE/HREE ratios of 5.35～5.68 and LaN/YbN values of 7.93～9.81, indicating a remarkable fractionation of light and heavy rare earths elements. The samples had obvious negative Eu anomalies. Trace elements are relatively enriched with large ionic lipophilic elements Rb, strong incompatible elements Th, U and high field strength elements Zr and Hf, and significant losses are lost to high field strength elements Ba, Nb, Ti and P. In combination with the regional geological background, The A-type granite, represented by the flesh red granite porphyry, was formed in an extensional environment and has specific petrological, mineralogical and geochemical characteristics. Its magma source is mainly crust-derived material, and may be mixed with a small amount of mantle-derived material. The I-type granites, represented by the flesh red syenogranite, may be related to the crystallization differentiation of mantle-derived magma, the partial melting of metamorphic igneous rocks in the lower crust, or the remelting of crust sediments modified by mantle-derived magma. The formation of the Shahongshan pluton is related to the post-collisional tensile environment and local compressive stress in the Early Permian, and has undergone complex processes of magma ascent, separation and crystallization, assimilation and contamination, and mixing. It is concluded that the tectonic background of Shahongshan pluton is the post-collisional plate rift valley environment.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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