Date of Award

1-1-2012

Document Type

Campus Access Thesis

Department

Earth and Ocean Sciences

Sub-Department

Geology

First Advisor

Gene M Yogodzinski

Abstract

New Re-Os measurements from molybdenite from three samples of mineralized drill core at the Haile Gold Mine, SC have yielded ages of 548.7 ± 4.2, 549.0 ± 3.1, 548.4 ± 2.4 and 541.2 ± 2.3. These combined ages suggest molybdenite formation at Haile occurred between approximately 540 and 552 Ma. The very fine-grained nature of molybdenite made it impossible to obtain pure, non-magnetic, mineral separates from the Haile samples. Two Re-Os ages reported outside of the 540-552 time window are interpreted as inaccurate, based on low Re abundances and relatively high common Os, indicating low purity molybdenite separates having ages that may have been significantly influenced by Re and Os in contaminant minerals. Broadly correlative Mo and Au abundances in drill samples produced during the recent phase of exploration at Haile, and the common presence of molybdenite in Au-bearing horizons indicate that Au mineralization at Haile probably also occurred in the 540-552 time window. The Re-Os molybdenite ages reported here establish a close chronological association between Au mineralization and the time of peak magmatism in the Haile area in the 545-558 Ma time window (Ayuso et al., 2005 - Econ Geol). These results indicate the hydrothermal systems that produced the Haile deposit were driven by volcanism at a time when the Carolina Slate Belt, which is exotic to North America, was still in a peri-Gondwana location. New constraints interpreted to reflect the accretion of the Carolina Slate Belt determined from 40Ar-39Ar measurements on two biotite samples collected from alkaline dikes cross-cutting the Haile deposit and U-Pb measurements of zircons collected from the Dutchman Creek Gabbro, a post orogenic pluton, have yielded ages of 311.27±3.0, 311±1.53 and 313.5 ± 5 Ma. The significant offset between these ages and the time of molybdenite formation along with the close chronological association between Au mineralization and the time of peak magmatism in the Haile area appear to rule out models that associate mineralization at Haile with metamorphism during accretion of the Slate Belt to Laurentia.

New U-Pb zircon dating of two samples collected from different rock units (metavolcanic and metasedimentary) in a single drill hole on the Haile property indicate that stratigraphy is out of sequence. U-Pb measurements on zircons collected from the metavolcanic unit yielded an age of 565.2 ± 11.3 Ma that was located at a depth in the drillhole above the metasedimentary sample, which contained significantly younger zircons. This geologic relationship, with metavolcanic rocks overlying metasedimentary rocks, is present throughout the Haile property. These measurements indicate that the units have been overturned by folding, or that the metavolcanic rocks have been emplaced by faulting over the metasedimentary rocks. New 40Ar-39Ar measurements of non-foliated biotite within mineralized horizons at Haile, which are interpreted to reflect a late stage metamorphic event, have yielded ages of 389.95 ± 1.25 and 388.35 ± 1.17 Ma. These measurements document the complex deformational history of the Haile deposit but based on interpretations of geochronological data presented in this study was not the driving force behind Au mineralization.

Rights

© 2012, Reid McCall Mobley

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