3D Computational Modeling On The Architecture And Dynamic Process Of The Metallogenic System In Yueshan Orefield In Anqing, China

The architecture and geodynamic processes are critical for understanding the matellogenic system. It is not easy to understand and illustrate the architecture and geodynamic processes of the complex matellogenic systems thoroughtly and accurately. Computational modeling has become one of the most effective means for researching such systems.The Yueshan orefield, located in Huaining, Anhui province, is one of the most important orefields in the lower-middle Yangtze metallogenic belt. The deposits in this orefield, mainly of skarns associated closely to the Yueshan felsic hypabyssal intrusion, are a very complicated metallogenic system. In this thesis, the Yueshan orefield is researched through computastional modeling, based on the analysis of the geological background and investigation of the deposits geology. By the3D shape simulation of the orebodies and related geological factors, the spatial architecture of the matellogenic system and the regularity of orebodies location are revealsed. By modeling the cooling process of the Yueshan intrusion, the dynamic mechanism and controlling factors for ore formation localisation are investigated. The main outcomes in this thesis include the following5aspects.1) On the GoCAD platform, a set of methods for simulating the complex geological bodies are developed according to the features of geological objects. By Section-TIN method and continuous profile data, model of orebodies with constant trending direction is constructed. Based on TIN constrained by curve border and data on crossed profile, surfaces with stable normal direction, such as stratum and fault, are modeled. Based on data on several different directions continuous profile, methods of Section-TIN and local constrained optimization are used to model intrusion with branches. These methods result in the ideal models that are smoothly surfaced as well as constrainted best the the original data.2) A programme is developed by using the C++programming to convert GoCAD solid model to tetrahedron meshed FLAC3D model for dynamic calculation. It absolutely faciliates model construction and grid discretization of complex geological bodies that are general difficult for the modeling the geodynamics of the complex metallogenic systems3) The3D shape modeling of the orebodies and related geological factors demonstrates that the shape of contact zone of the intrusion controls the orebodies location. It is discovered that the orebodies were generally localised in the specific sites where the shape of contact zone has sharp change.4) The modeling of spatial distribution of ore-related elements demonstrates that the concentration is related to the main faults, the shape of contact zone and the fold. The ore elements are concentrated toward the fault F1and F6, the turning positions of the contact zone and the fold hinge, suggesting that F1and F6can not only cut the orebodies, but also play an important role in ore enriching.5) Computational modeling experiments on the syn-tectonic cooling dynamics process of Yueshan intrusion are carried out, and the results are as follows. Fluid-focusing dilation spaces resulted from coupled mechano-thermo-hydrological processes are the favorable positions for the skarn orebodies locating on the contact zone. The uneven distributiong of fluid-focusing dilation spaces related to the shape of the contact zone is the main cause for the uneven distributiong of orebodies on the contact zone. The mixing reaction of fluids from different origin and the decrease of fluid pressure in the fluid-focusing dilation spaces are the main reason for ore precipitation.