Numerical Modelling Of Structural Reactivation With Implications For The Huangjindong Gold Deposit In The Northern Hunan Province,China

Dilational zones generated by during structural deformation plays an important role in the formation of many hydrothermal ore deposits.Previous studies suggest that dilations are prone to occur in reactivated pre-existing structures.The Jiangnan Orogen is an important gold-polymetallic belt in China.It has undergone multiple intracontinental tectonomagmatic events during the Caledonian,Indosinian,and Yanshanian since it was formed during the Neoproterozoic,numerous gold-polymetallic ore deposits and occurrences occur within reactivated structures in this orogen.In the Huangjindong gold deposit of the Jiangnan Orogenic Belt,South China,fracture zones are well-developed and control the distribution of ore bodies.However,it is still unclear which stress field is most suitable to produce structure dilation that localize gold mineralization.In this study,numerical modelling of deformation was conducted to examine the relationship between the distribution of strain and gold mineralization in the Huangjindong gold deposit with using FLAC3 D software.The modeling results demonstrate that during EW-trending tectonic compression,the positive volumetric strain(dilation)is well developed within the pre-existing fracture zones,which correspond well with the localization distribution of known gold veins.During compression,the development of the dilation zones may be enhanced due to the increase of depth,which may be favorable to gold mineralization at depth.In addition,the location relationship between the pre-existing structures and the fault will would affect the development of the dilation zones,and the preexisting structures located in the hanging wall of the fault is more relatively conducive to the generation of the dilation zones.Different fault angles also affect the generation of dilation zones,and fault dip less than 60° are more conducive to the generation of dilation zones.The lithology of stratigraphic unit has had a slight influence on the generation of the dilation zones.The modeling results highlight the importance of pre-existing fracture zones in gold exploration in the Jiangnan Orogenic Belt.