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Haile |
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South Carolina, USA |
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Au Ag Mo
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Super Porphyry Cu and Au
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The Haile gold mine is located in the Carolina Slate Belt, 5 km NE of Kershaw in southern Lancaster County, South Carolina, USA, in the north-central part of the state (#Location: 34° 35' 12"N, 80° 31' 54"W).
The Carolina Slate Belt, or Carolina Terrane extends 600 km from eastern Virginia to central Georgia and is up to 140 km wide in North Carolina. The Carolina Terrane is predominantly composed of Neoproterozoic to Cambrian metaigneous and metasedimentary rocks. It has a prominent structural flexure in central South Carolina near Haile. Structural trends to the SW are east–northeasterly, whereas those northeast of the flexure are northeasterly (Hibbard et al., 2002).
The Carolina Superterrane is composed of a number of terranes, (the Carolina, Charlotte, Augusta-Dreher Shoals and the Kings Mountain terranes) which include volcanic arcs, and were accreted to the North American craton during the Late Ordivician to Silurian (Hibbard et al., 2010). Gold mineralization at Haile (~549 Ma; Mobely et al., 2014) occurred during suturing of the Carolina and adjacent Charlotte arcs, coincident with emplacement of the Longtown and Little Mountain stitching plutons (Barker et al., 1998).
Four general tectonothermal events are recognised in the Carolina Terrane, including (Hibbard et al., 2002):
• Late Neoproterozoic to Early Cambrian Virgilina events (617 to 544 Ma) comprising folding, foliation and faulting accompanied by granite plutonism;
• Late Ordovician to Silurian Taconian events (457 to 425 Ma), with upright folding and a penetrative axial plane cleavage accompanied by greenschist facies metamorphism;
• The Devonian events of the Gold Hill-Silver Hill dextral shear zone (393 to 381 Ma) that juxtaposes the Carolina and Charlotte terranes; and
• Late Paleozoic Alleghanian events (333 to 286 Ma)the produced ductile mylonitic shear zones e.g., Hyco, Modoc shears (Hibbard et al., 1998) with orogenic quartz veins and greenschist to amphibolite facies metamorphism and granite plutonism.
Post-tectonic granites were intruded into the Carolina Superterrane at the end of the Alleghanian orogeny. The Liberty Hill (293±15 Ma) and Pageland (296±5 Ma) granite plutons which belong to this episode, are exposed west and north of Haile. Carboniferous intermediate to mafic dykes and prominent NW-trending Mesozoic dolerite dykes intrude the Carolina Terrane. Triassic to Early Jurassic rifting formed a number of sedimentary basins. Erosion and a sub-tropical, humid weathering palaeoenvironment formed saprolite up to 40 m deep in the region since the Mesozoic. Regional transgression during the Cretaceous resulted in the deposition of a southeastward-thickening apron of kaolinitic sands and clay above the saprolite. Continental uplift and regression of the Atlantic Ocean have led to continued erosion.
Mineralisation at Haile is exposed along an ENE-trending anticlinorium within a strongly deformed ENE-trending structural domain of the Carolina Terrane. It occurs at or near the contact between sequences of metamorphosed volcanic and sedimentary rocks that are of Neoproterozoic to Early Cambrian age (580 to 530 Ma). Deformation is dominantly ductile with ENE trending fold axes and isoclinal folding overprinted by shearing and local brecciation. Haile is hosted in foliated siltstones and greywackes in the upper part of the ~3 km thick Persimmon Fork Formation deposited at ~555 to 551 Ma in a submarine
slope environment (Maher et al., 1991, Hibbard et al., 2002). The Persimmon Fork Formation is largely composed of andesitic metavolcanic and tuffaceous rocks, with mineralisation at Haile primarily hosted by the sheared upper laminated unit of the formation. At Haile this formation is composed of greywacke, conglomerate, sandstone, siltstone and laminated siltstone grading upward into volcanic tuffs and volcaniclastic rocks. Sedimentary interbeds are common in the volcanic-dominated upper portion of the Persimmon Fork. These sedimentary rocks are conformably overlain by volcanic rocks, with contacts that are often gradational. The volcanic rocks are light grey to pale green with blocky weathering patterns in contrast to the platy metasediments. Upper sections of the formation contain poorly sorted, rounded to angular volcanic clasts in lithic tuffs. Volcaniclastic units are commonly interbedded with the tuffs and indicate variable volcanic and detrital inflows over time. The Persimmon Fork Formation is conformably overlain by mudstones and siltstones of the Richtex Formation marking a transition from volcanic to basinal sedimentation at ~550 Ma.
Haile gold mineralisation occurs as a 5 x 1.5 km cluster of moderately to steeply-dipping ore lenses within a ENE-trending anticlinorium. At least eleven named en echelon gold deposits with are recognised at Haile, distributed a over a 3.5x 1 km area. From west to east these include the Champion, 601, Small, Mill Zone, Haile, Ledbetter, Mustang, Red Hill, Palomino, Snake and Horseshoe. Ore body geometry, depth, size, grade, mineralogy and alteration vary from deposit to deposits. The geometry of ore zones is strongly controlled by post-mineral folding and the location within the Haile anticlinorium. Some of the deposits coalesce, particularly in the central part of the district around the large Ledbetter deposit. Ore lenses are typically 50 to 300 m long, 20 to 100 m wide, and 5 to 30 m thick. They are boat shaped where cut at surface.
Gold mineralisation is mostly hosted by folded laminated siltstone and greywacke of the upper Persimmon Fork Formation and is capped by less permeable volcanic rocks. Mineralisation is typically within 100 m of a sediment-volcanic contact. Mineralised zones at Ledbetter, Red Hill and Snake are partly hosted in volcanic rocks. Mineralisation is disseminated and occurs in silicified and pyrite-rich metasediments with local K feldspar and molybdenite. Mineral zonation is a quartz-sericite-pyrite±K feldspar±gold → sericite ± pyrrhotite → propylitic (chlorite-calcite-epidote) haloes. The quartz-sericite-pyrite mineralised zones are tens of metres wide. Sericite envelopes vary from tens to hundreds of metres in thickness and
are controlled by the protolith, structural permeability and post-mineral folding. Quartz is dominant (60 to 80%), pyrite is moderate (1 to10%), and sericite is variable at 5 to 20% within the mineralized zones. Two silicification events are recognised, namely an early phase of massive silicification which is finely disseminated to diffuse and a later phase manifested as matrix fill in tectonic and hydrothermal breccias and as stock work veinlets. Sericite alteration occurs as sericite schists resulting from sericite replacement of micaceous layers in metasediments. Bleaching and/or argillisation is weakly developed within and adjacent to sericite zones. Propylitic alteration is characterised by increased chlorite (5 to 20%) and a mottled texture with blebs of 3 to 5 mm calcite aggregates. Late calcite ± quartz veining is focused along fault zones.
High-grade zones with >3 g/t Au are characterised by intense silicification, anastomosing quartz veins, hydrothermal breccias and >1% fine-grained pyrite. The pyrite grain size is typically <20 µm and occurs as stringers, lenses and banded layers of stratabound massive sulphide including that in graded beds and reworked sulphidic sedimentary rocks. High grade zones are concentrated where ENE faults coincide with anticline axes in folded metasedimentary rocks adjacent to overlying metavolcanic rocks. The Horseshoe deposit, which averages >4 g/t Au and occurs within a tight anticline, is dissected by ENE-trending, NW-dipping faults.
Haile is the second largest historic gold producer in the eastern US, having yielded 23 tonnes of gold to 1990 over an episodic 160 year mining history.
Combined open pit and underground Mineral Resources at the end of 2016 (NI 43-101 Technical Report, SRK Consulting 2017) were:
Measured + Indicated Resource - 61.9 Mt @ 1.84 g/t Au for 113.9 t of gold;
Inferred Resource - 12.3 Mt @ 1.7 g/t Au for 20.9 t of gold.
Remaining Ore Reserves and Mineral Resources as at 31 December, 2018 (Oceanagold Media Release, March 2019) were:
Measured + Indicated Resource
Haile open pit - 53 Mt @ 1.55 g/t Au for 82 t of gold, at a 0.45 g/t Au cutoff;
Haile underground - 2.7 Mt @ 5.68 g/t Au for 15 t of gold, at a 1.17 g/t Au cutoff;
Proved + Probable Reserve included in Mineral Resources
Haile open pit - 51.3 Mt @ 1.57 g/t Au for 80 t of gold, at a 0.45 g/t Au cutoff;
Haile underground - 3.1 Mt @ 4.38 g/t Au for 13.6 t of gold, at a 1.5 g/t Au cutoff.
This summary is drawn from: SRK Consulting, 2017 - Haile Gold Mine, Lancaster County, South Carolina, an NI 43-101 Technical Report prepared for OceanaGold Corporation, 360p.
For more detail see the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 2017.
Record last updated: 12/9/2019
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd. Unauthorised copying, reproduction, storage or dissemination prohibited.
Haile
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Selected References:
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Alarifi, S.S., Kellogg, J.N. and Ibrahim, E., 2021 - Geophysical Study of Gold Mineralized Zones in the Carolina Terrane of South Carolina: in Econ. Geol. v.116, pp. 1309-1328.
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Ayuso R S, Wooden J L, Foley N K, Seal R R and Sinha A K 2005 - U-Pb Zircon Ages and Pb Isotope Geochemistry of Gold Deposits in the Carolina Slate Belt of South Carolina: in Econ. Geol. v100 pp 225-252
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Foley N, Ayuso R A, Seal R 2001 - Remnant colloform Pyrite at the Haile Gold deposit, South Carolina: a textural key to genesis: in Econ. Geol. v96 pp 891-902
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Hayward N 1992 - Controls on syntectonic replacement mineralization in parasitic antiforms, Haile Gold mine, Carolina Slate Belt: in Econ. Geol. v87 pp 91-112
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Mobley R M, Yogodzinski G M, Creaser R A and Berry J M, 2014 - Geologic History and Timing of Mineralization at the Haile Gold Mine, South Carolina : in Econ. Geol. v.109 pp. 1843-1862
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge. It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published. While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo, its employees and servants: i). do not warrant, or make any representation regarding the use, or results of the use of the information contained herein as to its correctness, accuracy, currency, or otherwise; and ii). expressly disclaim all liability or responsibility to any person using the information or conclusions contained herein.
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