Mining Decision Model On Weathered Crust Elution-deposited Rare Earth Ore

As a strategic resource, weathered crust rare earth ore (also named "ion-absorbed rare-earth"), known as "industrial vitamin", is of wide application value. The rare earth exists in ion and can’t be extracted by using the traditional processing method.The mining technologies invented by China’s science and technology personnel include pool leaching, heap leaching and in-situ leaching,although the pool leaching is now obsolete.Certain resources loss and ecological environment destruction will be caused both by heap leaching process and in-situ leaching. Under the background of ecological protection and "rare earth lawsuit loss" in the arbitration, the scientific selection of rare earth mining technology and timing are beneficial to resources protection and ecological environment.Integrating theories of mining, mineral processing, geology, engineering, geotechnical, ecology, economics, management science, environment discipline theory, policy tendency of the mining process of weathered crust rare earth ore is analyzed from the perspective of industry regulation based on the externality theory. A net value decision model and cloud decision-making model are established under the condition of the bottom bedrock integrity and ore deposit mining resources certainty and uncertainty. The major research conclusions are as follows:(1) The environmental damage and resource loss of the weathered crust rare earth ore are divided into explicit damage and implicit damage, resource loss into temporary loss and permanent losses. An "iceberg model" of weathered crust rare earth ore mining is established according to its negative externalities.(2) Some concepts, such as the actual marginal external cost, nominal marginal external cost, actual marginal social cost, are put forward based on the externality theory. Research results show that:heap leaching is liable to be excessively restricted while in-situ leaching tends to be overtly promoted. In addition, collecting sewage charges is favorable to limiting pollution emissions under the condition of undamaged deposit bottom bedrock; otherwise, the opposite is true.(3) The economic net value model is established under the condition of certainty bottom bedrock integrity and resource reserves. This model considers eco-environment cost factors, including comprehensive resource acquisition recovery, forest ecosystem service function value compensation. Three kinds of net present value rate decision models, including ecological self repair after in-situ leaching, in-situ leaching artificial restoration and heap leaching are put forward.(4) A shadow pricing model of mixed rare earth oxide is established under the condition of uncertainty illuviation for the ion-adsorption rare earth. Using rare earth mine A as the case, it is concluded that in-situ leaching mining technology is better than heap leaching at the current pre-tax shadow price 160,500 yuan/ton for the mixed rare earth oxide. In additional,the application condition of in-situ leaching and heap leaching is discussed as the critical condition λ=2.29.That heap leaching is better than in-situ leaching when λ> 2.29,otherwise,,in-situ leaching is better than heap leaching.Furthermore,it is the optimal timing when mixed rare earth oxide shadow price is more than 157,900 yuan/ton.(5) A cloud decision-making model is established under the condition of uncertainty weathering crust type illuviation and reaource reserves. Research results show that heap leaching process better than that of in situ leaching mining process under the condition of uncertainty.