Mountain range in northern North China during the Early Mesozoic: evidence from granite

Where and when plateaus or mountain ranges ever formed in the geological history is an interesting topic. This possibility is discussed according to the relationship between the geochemistry of granitic rocks and pressures of magma production. Granitic rocks may be divided into five types in terms of their Sr and Yb contents (1) adakites with Sr>400×10-6 and Yb<2×10-6, (2) Himalaya-type granites with Sr<400×10-6 and Yb<2×10-6, (3) Guangxi-type granites with Sr>400×10-6 and Yb>2×10-6, (4) Zhe-Min-type granites with Sr<400×10-6 and Yb>2×10-6, and (5) Nanling-type granites with Sr<100×10-6 and Yb>2×10-6. Except for the Guangxi type whose connotation is unclear, the differences of the Sr and Yb contents between the other four types of granitic rocks are related to depths of their magma production in the crust. The adakite magma is in equilibrium with the residual phase eclogite at pressures >1.5 GPa, which corresponds to a crustal thickness of >50 km. The Himalaya-type granitic magma is in equilibrium with high-pressure granulite with garnet and plagioclase as the main residual phases. It forms at pressures of 0.8-1.5 GPa, which are equivalent to a crustal thickness of 40 to 50 km. The Zhe-Min-type granitic magma is in equilibrium with amphibolite facies (plagioclase+amphibole) with a pressure <1 GPa, equivalent to a normal crustal thickness (30-40 km). The Nanling-type granitic magma forms in an extensional environment with a normal or thinner crustal thickness (30 km or less). According to the above-mentioned criteria and available U-Pb age data and geochemical dataset of granitic rocks, we recognized an Early-Mid Mesozoic (Triassic-Early Jurassic), E-W-striking mountain range in northern North China, called the northern North China Mountain Range. This mountain range is about 3,000 km in length E-W, 200 to 500 km in width N-S and 3,000 to 5,000 m in height. The range started uplift in the Early and Middle Triassic and the uplift reached the culmination in the Late Triassic. After the Early Jurassic it collapsed and disappeared, indicating a strong compressive tectonic and rapid uplift event in North China due to the collision between the Siberian block and North China block.