University of Tasmania, Australia

Geological and geochemical vectors to mineralisation at the Resolution porphyry copper-molybdenum deposit, Arizona

The Resolution Project is located three miles east of Superior, Arizona, USA. It was discovered by Magma Copper Co. and BHP Billiton via underground and surface drilling in an exploration campaign that ran from 1994 to 1998. Exploration conducted by Kennecott Exploration Co. from 2001 to 2003 confirmed a large body of copper mineralization at a depth of more than 1300m below surface. Resolution Copper Mining LLC (RCML) now holds 100 per cent of the assets and liabilities of the project, is owned 55 per cent by Resolution Copper Company and 45 per cent by BHP Copper Inc.

The Resolution deposit is a world-class porphyry Cu-Mo system located beneath a minimum of 1000m of post-mineral cover. The deposit is hosted in a sequence of sedimentary and intrusive rocks varying in age from Precambrian to early-Tertiary. It is strongly host-rock controlled with the best grades typically found in strongly altered and mineralized Precambrian diabase and limestone. Several faults with >200m displacement are present within the area of the deposit, but the bulk of movement was apparently pre-mineral and does not appear to offset mineralization.

Although its ultimate size has not been fully defined, the deposit is characterized by consistent +1 per cent Cu mineralization in suitable host rocks above an elevation of 750m below sea level, and extends over an area of at least 2km in an east-northeast direction and 1.5km in a north-northwest direction. Its thickness is locally greater than 500m. Significant but lower-grade mineralization extends beyond this defined body of strong mineralization. The total inferred resource is 1,341 Mt @ 1.51% Cu and 0.040% Mo, making Resolution, together with Hugo Dummett (Mongolia) and Pebble (Alaska), one of the three exceptionally high-grade giant porphyry copper deposits discovered in the past decade. Resolution is currently ranked 16^th out of the world’s largest porphyry Cu deposits in terms of contained copper metal.

This PhD study will investigate the geological setting of the Resolution deposit and will focus on key features to help understand how its location could be predicted from anomalous aspects of the district-scale geology. Research will involve:

• Drill core logging and mapping to determine the geological and structural controls on mineralisation, including evaluations of the basin architecture and possible reasons for the thick accumulation of Cretaceous volcaniclastic rocks and minimal amount of Paleozoic basement in the mineralised block that hosts Resolution
• Evaluation of possible genetic relationships, via geochronological and geochemical techniques, between Resolution and the nearby Magma high sulfidation vein and lower grade Superior East porphyry copper deposit, to establish if there is useful vectoring information in the near-surface, lower grade mineralised centres that could help to predict the existence of Resolution
• Detailed mineral chemistry (epidote, chlorite, pyrite) and sulfur isotopic zonation studies to help test whether geochemical vectors to mineralisation can be determined from the propylitic halo to Resolution, in order to help in the exploration for similar deep-seated, high-grade porphyry targets