Dual length-scale modelling of the formation mechanism relevant to the Caixiashan Pb-Zn deposit, Xinjiang, China: Effects of regional-model bottom boundary-conditions on mineralization patterns

• To numerically simulate the mineralization process in the Caixiashan deposit. • To identify the controlling mineralization mechanism in the Caixiashan deposit. • To examine effects of boundary-conditions on the Caixiashan deposit formation. • To use numerical modelling methods for predicting the location of an ore deposit. The Caixiashan Pb-Zn deposit is located in the polymetallic metallogenic belt, which belongs to the Central Tianshan Terrane, Xinjiang, China. Although extensive field observation and laboratory experiment studies of using traditional geological, geochemical and geophysical methods were carried out for investigating the mineralization system relevant to the Caixiashan Pb-Zn deposit, no research work has been conducted, to date, to simulate the ore-forming processes of this particular deposit through using advanced numerical-modelling methods. In order to fill this gap, this study utilizes the recently-proposed numerical-modelling approach of utilizing dual length-scale models, which contains a deposit (small length-scale) model and a regional (large length-scale) model and uses the finite element method (FEM) as well, to numerically simulate the hydrothermal ore-forming processes relevant to the Caixiashan Pb-Zn deposit. Special consideration is concentrated on investigating the effects of the regional-model bottom boundary-conditions on the formation of the Caixiashan Pb-Zn deposit. The key findings of this study have elucidated that: (1) the convection of pore-fluid is the predominant dynamic mechanism, which controls the formation of the Caixiashan Pb-Zn deposit; (2) although the numerically-simulated grade of the Caixiashan Pb-Zn deposit may depend on the regional-mode bottom boundary-conditions, the numerically-simulated location of this deposit does not; (3) the numerical-modelling approach of utilizing dual length-scale models is very useful in numerically modelling the formation mechanism relevant to the Caixiashan Pb-Zn deposit.