New Advances in Geochemical Exploration - Dr. David Cooke

"New Advances in Geochemical Exploration - Detecting the Subtle, but Giant, Geochemical Footprints of Porphyry Cu and Au Deposits Using Mineral Chemistry".
Dr. David Cooke is the Director of CODES, the Centre for Ore Deposit and Earth Sciences, at the University of Tasmania. David and his research team have been investigating porphyry and epithermal systems for over three decades, investigating genetic aspects, characterizing deposits, and developing innovative new geochemical and geological exploration tools to aid discovery. David is an Associate Editor of Economic Geology, and was a recipient of the Haddon Forrester King Medal from the Australia Academy of Sciences (2018), the Society of Economic Geologists’ Silver Medal (2013), and the Thayer Lindsley Distinguished Lecturer award (2005).
Porphyry deposits are the world’s largest repositories of copper and molybdenum and are major sources of gold and silver, making them one of the key exploration targets for major mining companies. Mineralization is spatially, temporally, and genetically related to hydrous, oxidized porphyritic intrusions that are emplaced into the shallow crust. Fluids released from the intrusive complex alter the surrounding rock mass, producing an enormous volume of alteration that extends for several kilometers vertically and in some cases more than 10 km laterally from the causative intrusions. Exploration techniques for porphyry deposits are well established, with key geological, geochemical, and geophysical properties providing useful guidelines for exploration that prove particularly effective at detecting mineralization within 1-2 km of the ore zone - these features define the exploration ‘footprint’ of porphyry deposits.
The most distal forms of porphyry-related alteration produce subtle, subdued mineralogical transformations of the primary rock mass and sparse veins, making it challenging to recognize whether these features are part of a porphyry system or some other style of background alteration or metamorphism. Over the past two decades, significant research efforts have been devoted to mineral chemistry studies using laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) that have unlocked the exploration potential of distal alteration, expanding the detectable geochemical footprint in some cases to more than 5 km from the intrusive center, and providing tools for screening porphyry and background alteration. Under optimal conditions, trace element analyses of distal alteration minerals can provide tools to help predict the likely direction and distance to mineralized centers, and provide indications of the potential metal endowment of a mineral prospect. This presentation will provide several examples of how mineral chemistry can potentially aid exploration for volcanic-hosted and carbonate-hosted porphyry deposits.