ISOTOPE RATIO AND TRACE ELEMENTAL IMAGING OF MINERALS BY SECONDARY ION MASS SPECTROMETRY

WE PROPOSE TO DEVELOP SECONDARY ION MASS SPECTROMETRY (SIMS)BASED IMAGING ISOTOPE RATIO TECHNIQUES FOR ISOTOPIC MICROANALYSIS OF MINERAL DEPOSITS. WE WILL COMBINE THIS CAPABILITY WITH SIMS BASED TRACE ELEMENT MICROANALYSIS. THEPETROGENESIS OF ORE DEPOSITS OFTEN INVOLVES AN AQUEOUS SOLUTION BY WHICH THE ORE-BEARING COMPONENTS ARE TRANSPORTED. THESE HYDROTHERMAL SOLUTIONS ALSO TRANSPORT SULFUR. DIFFERENT AQUEOUS PROCESSES GIVE RISE TO DIFFERENT (34)S/(32)S ISOTOPE FRACTIONATIONS. THE (34)S/(32)S RATIOS CAN PROVIDE IMPORTANT INDICATIONS OF THE SULFUR ORIGIN, AND BY EXTENSION, THE ORIGIN OF ECONOMICALLY IMPORTANT METALS. ISOTOPE RATIO AND TRACE ELEMENT IMAGING SHOW THE INTERRELATIONSHIPS OF DIFFERENT MINERAL GENERATIONS. THESE GENERATIONS OFTEN COEXIST WITHIN A SINGLE MINERAL GRAIN. WEHAVE DEMONSTRATED THAT IMAGING SIMS CAN SUCCESSFULLY IDENTIFY THE LOCATION OF TRACE GOLD LEVELS ("INVISIBLE" GOLD) IN PYRITE RIMS, AND THAT ISOTOPE RATIO IMAGING OF METEORITIC MATERIALS HIGHLY ENRICHED IN DEUTERIUM IS POSSIBLE. HOWEVER, EXTENSION TO (34)S/(32)S ISOTOPE RATIO IMAGING REQUIRES FURTHER INNOVATION AND MANY CAREFUL MEASUREMENTS. IN PHASE II, WE WILL EXTEND THESE IMAGING TECHNIQUES TO MICROANALYTICAL AGE DATING AND MICROANALYTICAL TRACE ELEMENT PETROGENESIS.