TO DEFINE TENTATIVELY GUIDELINES FOR THE EXPLORATION OF SEVERAL TYPES OF MINERALIZATIONS LINKED TO GRANITES AND ANATEXIS.
This contribution to the development of geochemical methods in mineral exploration focuses on granite related mineralisations. Earlier studies provided evidence for the importance of a magmatic contribution in W-bearing skarns and the genetic similarities between skarns and other types of W-bearing ores (veins, greisens). The present study enlarges the scope of our previous investigations in two main directions:
it concerns a wider range of metallic associations which are related to acid magmatism, namely the Fe-(Cu)-W, W-Mo, W-Sn and Ta-Sn (Nb, Li) orTa-W(Nb) associations;
it provides a deeper insight into the nature of the associated magmatism and the differentiation processes which concentrate the ore elements - in particular, magmatic rocks have been studied not only for themselves (chemistry, internal evolution, ore potential), but also as elements of magmatic suites that reflect more deep seated differentiation processes, a task which often lead us to develop our geochemical investigations on a regional scale.
Granite related mineralizations have been studied involving a wide range of metallic associations which are related to acid magmatism, namely the iron (copper) tungsten, tungsten molybdenum, tungsten tin (niobium, lithium or tantalum tungsten (niobium) associations.
The research provides a deeper insight into the nature of the associated magmatism and the differentiation processes which concentrate the ore elements; in particular, magmatic rocks have been studied not only for themselves (chemistry, internal evolution, ore potential), but also as elements of magmatic suites that reflect more deep seated differentiation processes.
Magmatic processes are thought to concentrate ore metals and they offer an almost unique possibility of predictive modelling and hence may provide quantitative methods to check the economic interest of a given prospect.
In order to prospect tantalum, niobium, tungsten, tin and molybdenum both magmatic processes and hydrothermal processes have to be taken under careful examination.
Only magmatic suites linked by fractional crystallization are to be selected in a given region, and those exhibiting large ranges of evolution seem to be the most promising ones. Preconcentration of the ore elements during evolution seems to be a prerequisite for further concentration processes. The nature of magmatism also plays a role in the level of the magmatic concentrations. Efficient geochemical tools to distinguish fluid sources are the combination of oxygen and strontium isotopic compositions and rare earth element (REE) distribution in magmatic and hydrothermal minerals.
Reconstitution of hydrothermal events and fluid channelways are very important in exploration especially in the search of extensions of known ore bodies. Adequate tools are hydrogen isotopic composition and trace element composition in hydrothermal muscovites and calcium bearing hydrothermal minerals, and distribution contours of some trace elements mapped in small granitic cupolas .
Finally ore reserves may be evaluated in some favourable cases using mass balance calculations between parent liquids and lixiviated rocks, given the knowledge of the mode of magmatic differentiation.
THIS JOINT PROJECT IS BASED ON A COMPARATIVE STUDY OF VARIOUS TYPES OF MO, W, SN, TA, NB, LI MINERALIZATIONS IN WESTERN EUROPE. THE ELEMENTS ASSOCIATIONS WILL BE EXAMINED FROM TWO POINTS OF VIEW: THE FIRST WILL CONSIDER THE DIFFERENT GEOLOGICAL ENVIRONMENTS I E HIGH LEVEL GRANITES AND ANATECTIC DOMAINS, THE SECOND WILL STUDY THE VARIOUS METALLOGENIC ASSOCIATIONS (MO-W, W, W-SN, W-NB, TA OR LI-SN-NB-TA).
WE INTEND TO DEFINE QUANTITATIVELY THE SPECIALIZATION OF MAGMATISM MODELLING AND TO CHARACTERIZE THE ASSOCIATED HYDROTHERMAL SYSTEMS. THE STUDY WILL BE BASED ON THE GEOCHEMISTRY OF MAJOR AND TRACE ELEMENTS, ON ISOTOPES AND FLUID INCLUSIONS.
Funding SchemeCSC - Cost-sharing contracts