A STUDY OF LATE-PROTEROZOIC HOST ROCKS, THEIR STYLE OF ALTERATION AND THE AGE OF MINERALIZATION AT THE DEEP RIVER GOLD PROSPECT, RANDOLPH AND MOORE COUNTIES, NORTH CAROLINA

Preliminary core examination and field mapping of rocks hosting Cu–Au–Mo mineralization 100 km southwest of Chapel Hill, NC have shown a possible contact between the older Virgilina volcanic Sequence and the younger Uwharrie Formation and Albemarle Sequence. More detailed examination of this contact may reveal structural discordances that are characteristic of Virgilina deformation.

Drill cores show a sequence of well–foliated ash tuffs overlain by alternating bands of dacitic feldspar–quartz crystal tuffs and lithic crystal tuffs, and a well-foliated mudstone or siltstone that is in fault contact with an intensely folded lapilli tuff. The observed types of alteration include dominantly quartz–pyrite and quartz–sericite–pyrite, but minor fluorite and K–feldspar are present locally. A comparison of geochemical data and observed alteration shows that except for the weathered part of the profile, the metallic mineralization correlates positively with quartz–pyrite alteration. Furthermore the Cu, Au and Mo anomalies trend dominantly NNW. Field mapping and measurements in drill core show that foliation strikes northeast and dips moderately to steeply and consistently northwest. Therefore a possible link between the mineralization and structures is being considered.

Preliminary U–Pb zircon analyses from a porphyritic dacite or crystal tuff, yields an age of 551 ± 1.1 Ma. If this age turns out to be an intrusive age, then the prospect is most likely hosted by the Virgilina volcanic arc sequence. Alternatively, if the age turns out to be stratigraphic, then the prospect is hosted by the Uwharrie Formation. Pending Re–Os age dates from a molybdenite sample should determine the timing relationship between mineralization and host rock deposition or intrusion.