ISOTOPIC CONSTRAINTS ON THE ORIGIN OF GOLD DEPOSITS AT THE HAILE GOLD MINE, LANCASTER COUNTY, SC

Gold at the Haile Gold Mine, in the Carolina Slate Belt, is found mainly within silicified metasediments of the Richtex Formation near the contact with the underlying metavolcanic Persimmon Fork Formation. Previous studies at Haile have led to two incompatible explanations for the origin of mineralization. Some researchers have proposed an orogenic model based on structural relationships within the deposit, suggesting that gold was deposited from fluids derived during regional metamorphism (Tomkinson, 1988: Hayward, 1992). Others have proposed an epithermal model based in part on mineralogy and isotopic data (Crowe, 1995: Foley et al., 2001: Ayuso et al., 2005). The location of the deposit along the volcano-sedimentary transition, Re-Os ages on MoS₂, and contrasting structural data also provide evidence for this model. Both explanations have important and differing implications for exploration in the surrounding Slate Belt, so further data that clarifies the origin of these deposits is useful in a broader regional exploration context.

Previous small-scale oxygen isotope studies of whole rock samples at Haile (Feiss and Wenner, 1989: Kline and Criss, 1998) suggest an epithermal system was responsible for mineralization. In order to help resolve the ore genesis debate at Haile by continuing with this line of evidence, a more in depth isotopic study focusing mainly on quartz has been conducted. Oxygen isotopic values of quartz from silicified zones, stockwork breccias, and different generations of veins have been measured in an attempt to constrain the source of fluids responsible for their formation. As silicification is strongly associated with mineralization at Haile, fluids responsible for silicification can also reasonably be considered responsible for ore formation. Gold is also associated with pyrite, so δ³⁴S values of a set of pyrite samples from the deposit were also determined.

The δ¹⁸O values for the quartz samples range from 5.9 to 9.1 per mil. Assuming a fluid temperature of 300° C, the fluids responsible for silicification at Haile would have δ¹⁸O values between -1.0 and +2.2 per mil which is typical for an epithermal system, but outside the range expected in orogenic systems. The δ³⁴S values of pyrite range from -1.6 to +3.4 per mil, and are consistent with values from other Slate Belt deposits (Eager, 1997).