内蒙古呼伦贝尔早中生代花岗岩的年代学和岩石地球化学研究：对岩石成因和地球动力学机制的制约

微细粒钛铁矿的回收制约着我国攀西地区钛资源的高效开发利用。四川某矿业公司的斜板溢流原矿属辉石、橄榄石混合型钛铁矿，且粒度极细，-19 μm产率为79.22％，其中TiO2分布率为87.54％。研究结果表明，预先采用强磁选可有效消除部分超微细粒钛辉石、橄榄石等易浮杂质对浮选分离的不利影响，磁选精矿通过一次粗选五次精选一次精扫选流程，可获得钛精矿产率为21.85％，TiO2品位为47.44％，回收率为62.89％的良好指标，为矿山高效利用钛资源提供了合理的技术方案。

Study on New Beneficiation Technology for a Refractory Ultrafine Ilmenite Ore in Panxi

Hulun Buir, Inner Mongolia, is located at the northeastern part of the North China Craton, with a large area of Mesozoic granites. These granites are of great significance for studying the evolution, tectonic environment and dynamic mechanism of the lithosphere beneath the North China Craton. However, few have been studied on the genesis, tectonic setting and emplacement mechanisms of the monzonitic granites from the Hulun Buir. In this paper, based on field geological survey, systematic studies have been carried out on early Mesozoic granite from the Hulun Buir in terms of major and trace element compositions as well as zircon U-Pb isotope dating. Zircon U-Pb isotope dating shows that these granites were the product of magmatic activity in the Early Triassic (251.1 ±1.2 Ma) and Early Jurassic (187.4 ±1.1 Ma). Early Triassic and Jurassic granites belong to high-K calc-alkaline types. These granites are rich in light rare earth elements (LREEs) and large ion lithophile elements (e.g., Rb, Th, U, K), but relatively depleted in high field strength elements (HFSEs) such as Nb, Zr, Hf, P, Ti, which are similar to the average distribution pattern of Chinese monzonitic granites. The incorporated results of the trace element characteristics and the geological research studies show that the Hulun Buir Mesozoic granites were formed in the crystallization differentiation of crust-derived magma. Early Triassic granite intrusive rocks were formed in intraplate extensional environments; the tectonic setting of early Jurassic granite formation was related to the interaction between continental crusts and the subduction of the oceanic crust (i.e., Paleo-Asian Ocean) towards the continental crust (i.e., Siberian plate), i.e. the oceanic subduction-collision environment, and the subduction was mixed with a certain amount of oceanic crust components. The occurrence of the high-potassium granite also suggested the subduction and collision of the oceanic crust of the Eurasian Ocean, implying that the Early Mesozoic intrusive rocks were probably formed in the orogenic belt (island arc and active continental margin). This study can provide an important geological basis for non-ferrous metal prospecting in the Hulun Buir.