Origin and influence of a Late Mesozoic multistage I‐ and A‐type granitic complex in northern Fujian Province, South China

Abstract

The Late Mesozoic Pucheng granitic complex in northern Fujian Province is composed of the Chengbu and Shipi peralkaline A-type granitoids, the Pucheng A-type granitoid, and the Yongxing I-type granitoid. The Chengbu and Shipi peralkaline granitoids were dated at 160 and 130 Ma, respectively, and are explained by the melting of meta-igneous rocks with T DM 2 of 1.70 Ga and 2.01 to 2.05 Ga. The Pucheng A-type granitoid was emplaced at 110 and 102 Ma and is divided into two groups. Group 1 comprises the extremely felsic A-type granite (SiO 2 > 73 wt.%), high FeO T /MgO (>16), and low Ga/Al ratios and Zr + Nb + Ce + Y content. Group 2 contains a lessevolved A-type granite with high Zr + Nb + Ce + Y content. Both groups can be explained by dehydration melting of meta-igneous rocks at low pressure. The diversity between the two groups was caused by different physicochemical environments. The Yongxing I-type granite, which is abundant in mafic microgranular enclaves, was emplaced at 106 ± 1 Ma. It can be explained by the mingling of mantle-derived and crustal-derived magmas. Our data along with previously published data demonstrate that the northern Fujian Province was under an extensional environment from 160 to 100 Ma. This was caused by the NW-trending subduction of the palaeo-Pacific Plate. The Jurassic peralkaline granitoids were probably generated in a rift environment as a result of the reactivation of pre-existing faults caused by the initial subduction of the palaeo-Pacific Plate. The Early Cretaceous peralkaline granitoids may represent a rift environment as a tectonic response from low-angle subduction to an increasing subduction dip angle. The 100 Ma granitoids derive from an intraplate extensional environment caused by the roll-back of the palaeo-Pacific Plate.

Fault diagnosis mechanism of gears and bearings for coal mining equipment in a complex geological environment

“…Figure 3 is the structural diagram of the gear after the deformation of the teeth and grooves. Assuming that there is vertical load on the axis at the upper and lower ends of the structure, it is represented by p 1 and p 2 (Wang et al, 2018).…”