An Analysis Of The New Indicators In Geochemical Exploration Of Porphyry Type Copper Deposits

Geochemical anomaly is shown in the form of geochemical indicator, and geochemical indicator is a kind of geochemical variable that can provide geological prospecting information, which can be measured directly or indirectly. With the increasing depth and difficulty of geological prospecting geochemical indicators are in a higher demand, and it is meaningful to explore'new geochemical indicators to improve the success rate of prospecting.This paper takes the Chengmenshan porphyry copper deposit of Jiangxi province and the Wunugetushan porphyry copper-molybdenum deposit of Inner Mongolia as the research object, and do some research on the distribution of elements involving the enriched and depleted characteristics of elements for the purpose of extraction of exploration geochemical indicators of porphyry copper-polymetallic deposits.Results show that: (1) the mineralization is accompanied by extensive enrichments in chalcophile elements of Au, Ag, As, Sb, Bi, Hg, W-Mo group elements of W, Sn, Mo, chalcophile dispersed elements of Cd,In,Se, mineralized elements of S,I, and major elements of Fe, (2) in contrast, compared to respective abundance of acid rocks major elements of Mg,Ca,Na, lithophile elements of Ba,Sr,Rb, iron group elements of Ni, rare elements of Li,Nb,Ta and rare-earth elements are depleted over or around the porphyry-type deposit.One characteristic which depleted elements have is the depleted elements are just related to whether the mineralization happens or not. The extensive depletion exists in the whole ore-forming stage, in which there is no consistent correlation with the strength of mineralization, and the contents of depleted elements decrease in various degree comparing to their own abundance of acid rocks. The other is the depletion of elements intensifies with the enhanced mineralization(Cu content increase),such as Ba, Sr,CaO.The integration of enriched elements and depleted elements are much more efficient in indicating the favorable anomalies. The study in the drill hole of the Wunugetushan found that the values of Cu/Ba, Cu/Sr, Cu/Na2O, Cu/CaO have obvious differences between the non-mineralization and mineralization drill hole which is helpful for indicating the favorable anomalies of mineralization, which can lay the foundation for the establishment of quantitative indicators for geochemical anomalies appraising.Based on the difference in mobilities of elements in the process of porphyry-type minerlization, it established two comprehensive geochemical indicators of Na₂O/K₂O and CaO/MgO in this paper. They decrease with the enhanced strength of Cu mineralization which can be used to evaluate the strength of the porphyry-type mineralization, and then appraise the prospects of Cu anomalies for mineralization.In order to better display the practicality and effectiveness of the geochemical exploration new indicators for evaluation of metallogenic prospects, demonstration works are lauched in the Zuantianshan area. The Zuantianshan area has a good ore-forming geological background, but there is not mineral deposit which has industrial value found until now. Through the study of the enriched elements and depleted elements occurred in the area respectively and compositively to assess the anomalies prospect for minerlization and finally confirm the existence of mineralization.