Trace elements and growth patterns in quartz from the Alubaogeshan granite in the Maodeng Mo-Bi-Sn-Cu deposit, southern Great Xing’an Range, NE China

Abstract

The Maodeng Mo-Bi-Sn-Cu deposit is located in the southern segment of the Great Xing’an Range in northeastern China. The Alubaogeshan complex is the major intrusion in this region, which is composed of porphyritic monzogranite (PMG), granite porphyry (GP), and alkali feldspar granite (AFG). We conducted SEM-CL and LA-ICP-MS analyses to examine internal textures and trace elements of quartz from three facies, aiming to uncover the petrogenetic connections among the different lithologies. Quartz phenocrysts from PMG and GP exhibit smudged pre-resorption core, and post-resorption quartz overgrowths with higher Ti concentration and CL intensity, whereas quartz from AFG shows a taxitic structure, with an outward decrease in Ti concentration and CL intensity. There is a positive correlation between CL intensity and Ti content in magmatic quartz. The Al/Ti and Ge/Ti ratios in quartz indicate that the degrees of differentiation of PMG and GP are comparable and relatively low, while that of AFG is high. Trace element contents also exhibit characteristic evolution during magmatic differentiation, with the higher Al, Be, Ge, Rb, and B, and the lower Ti contents in quartz from the highly evolved AFG, and the higher Ti values in quartz from the less evolved PMG. A strong correlation between Al and Li concentrations suggests that Li+ is a primary charge compensator of Al3+ substituting for Si4+ in quartz, with the remaining Al3+ equilibrating with H+. The entry of Al into quartz is mainly controlled by crystallization temperature in the less evolved granite, but magmatic differentiation exerts a key role in the highly evolved granite. Magma differentiation is a primary factor influencing Ge incorporation into quartz. Quartz crystals from PMG and GP display textural and chemical evidence of high-Ti, -CL, and -temperature overgrowth, indicating multiple recharges of mafic magma into the felsic magma chamber. This process could have supplied abundant metals to the granitic magma system and contributed to the formation of the Maodeng deposit.