Innovative analytical and geophysical technologies for detecting blind polymetallic orebodies in southern Spain
The first objective of the project, and probably the most problematical, was to discover an economic polymetallic sulphide deposit in the Spanish part of the Iberian Pyrite Belt (IPB), through the development of an effective low cost exploration methodology. This was based on improved reasoned geological deduction, and on the development, testing and application of new and powerful exploration and analytical tools in the fields of geophysics and geochemistry. The project hinged around several closely linked poles of interest with the immediate aim of discovering a base metal and precious metal sulphide deposit. Beginning with the results of standard exploration methods (geological, geophysical and geochemical surveys), it was necessary to develop: new exploration tools (gas sampler, 3-axis electromagnetic system) for use in the field or for resolving exploration-related geological problems; more powerful synergic systems of data processing (3-dimensional geophysical and geological modelling, multidataset processing, regional database); an analytical tool capable of providing varied geochemical data rapidly and cheaply (inductively coupled plasma-mass spectrometry (ICP-MS) laser ablation probe) for use in the laboratory; a methodology based on the new tools and on improved geological deduction. The new tools that have been developed and the new geological data that have been acquired can be integrated into a mineral exploration methodology. The gas sampler and the 3-axis EM prove are direct prospecting tools that find their place in the investigation of preselected anomalies. The gravimetric modelling software is a data interpretation tool which can be used for modelling the possible shapes and sizes of know orebodies and for interpreting virgin anomalies. The ICP-MS laser ablation probe is a laboratory tool used in the detailed studies required for defining and controlling geological selection criteria. The criteria that have been defined as a result of this project are relevant to all stages of mineral exploration, from the selection of a potential mineralized province or geological series to the evaluation of an orebody. The proposed exploration methodology is based on mainly the results of the project work and has not involved an exhaustive evaluation of existing methods. Nevertheless the suitability of each tool and criterion must be considered in the light of the local conditions under which it is to be used. In conclusion, one of the aims of the project, that of developing new exploration techniques based both on new technological tools and on an improved methodological approach, was fulfilled, with geophysical and analytical tools being developed as planned. The other aim of the project, that of discovering a polymetallic deposit in a traditional mining province in decline was not successful. This was due in part to the inherent risk in all mineral exploration, which is high despite the great improvement in exploration methodology.