Keywords:ore deposit, metal content, fluid flow, geostatistics, advection-diffusion
Fluids play an important role in various aspects related to ore deposits and are crucial to the formation and development of ore deposits. This study aims to develop a method combines spatial statistics and physical law for metal contents in an ore deposit. Semivariogram clarified spatial correlation structure of the metal data and then kriging and sequential Gaussian simulation were used to generate spatial distribution of ore grade in three-dimensions. Transports of ore fluid and deposition process of metals were assumed as a physical process governed by the advection and diffusion. Analytical and numerical solution of an advection-diffusion equation was applied to ore grade data by calculating key parameters, advective velocity and diffusion coefficient. In order to simulate accurately, parameters were then revised as variables in different zone according to geological structure and geostatistical model. Matsumine and Fukazawa mines, typical large kuroko deposits in the Hokuroku district, Akita Pref., northern Japan, are selected to verify the combined method. Metal elements such as Cu, Zn, and Pb (chief metals of kuroko) of drilling cores were used for the spatial and physical modeling analyses. This method termed SPG (Spatial modeling by joint use of Physical law & Geostatistics) presents general main paths of ore fluid with respect to source, flow direction, and flow rate. The same technique and SPG are applied to a hydrothermal deposit in Sulawesi Islands, Indonesia. As the result, high metal content zones are well clarified and characterized, and a fluid flow pattern that formed the zones is expressed as colloidal texture which could indicate temperature and pressure changes in shallow subvolcanic activities.
Acknowledgments: The authors wish to express their gratitude to Dowa Metals & Mining Co., Ltd. and Hanaoka Eco-System Co., Ltd. for providing the precious drilling investigation materials.