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Hillendale, Fairbreeze |
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KwaZulu-Natal, South Africa |
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Ti Zr
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Hillendale and Fairbreeze heavy mineral sand (HMS) ilmenite - zircon deposits are located to the south-west of Richards Bay in KwaZulu-Natal and approximately 175 km north of Durban in South Africa. Hillendale is 10 km south-west of Richards Bay and Fairbreeze is approximately 30 km further to the south-west.
Both of these deposits are located within the Late Tertiary-Pleistocene KwaZulu-Natal dune corridor developed along the KwaZulu-Natal coastline, interpreted to represent the remnants of a large coastal dune system that formed on the Mozambique coastal plain during the late Pliocene at approximately 3 Ma.
The KwaZulu-Natal coastline was generated by rifting processes during the Jurassic to Cretaceous breakup of Gondwanaland. By the end of the Cretaceous, the current coastline was established, and since then, local modifications have resulted from tectonic uplift, eustatic changes and flexuring of the continent. During the Tertiary and Pleistocene the Mozambique coastal plain was subjected to several marine transgression-regression cycles, with a major Eocene transgression resulting in deposition of marine sands on the coastal plain.
Beach gravels and dunes up to 100 m above mean sea level are common along this coastline and there appear to be at least two major beach elevations at 30 m and 60 m above sea level (asl). Pleistocene dune ridges are prominent along the KwaNatal shoreline. The highest dunes are dominated by homogenous red sands of the Berea Formation that preserve many aeolian features, wih the red colouration believed to be due to weathering of heavy minerals under tropical conditions. Evidence for submergence of some of the Pleistocene dunes is unequivocal, while relict submerged dunes are also present off the coast, recording periods when the sea-level was 70 m lower than the present sea-level.
The heavy minerals within the sand units were derived from the rocks from the Mesoarchaean granite-gneiss-migmatite-greenstone basement of the eastern Kaapvaal craton, the 1.1 Ga Natal Metamorphic Belt, the lower Palaeozoic sediments of the Natal Group, the Permo-Carboniferous to Cretaceous sediments of the Karoo Supergroup, and the thick Jurassic Drakensberg (or Karoo) dolerites, that underwent fluvial transport to the sea during protracted erosion and were subsequently concentrated within the beach environments by near shore wave and wind action.
The Hillendale deposit represents a paleo-spit formed at the mouth of the paleo-Mhlatuze River. It consists of dominantly Berea Formation red sands lesser discontinuous lenses of medium to coarse yellow to dark orange sands that are low in silt and clay and total HM. The deposit is approximately 3.8 km long, 600 m wide and generally between 18 m to 21 m thick. The total HM content is between 1% and 25% with economic HMs making up 10% to 70% of the total HM suite. Grades are locally variable but as a unit Hillendale can be considered relatively homogeneous. The silt content of the sands ranges from 15% to 25% is largely due to weathering.
The Fairbreeze deposits represent paleo-strandlines and beaches that developed adjacent to headlands. The deposits are distributed over a total strike length of approximately 10 km and a width of 700 m and are divided into five separate blocks, Fairbreeze blocks A, B, C and D. Like Hillendale, the Fairbreeze Project deposits are hosted within Berea Formation sands, although at Fairbreeze these sands are distributed above a variable bed-rock surface. In the extreme north, sandstones and shales of the Vryheid Formation outcrop to the southeast. Between the A and B blocks, sandstones and grits of the Natal Group lithologies are exposed, the Berea Formation sands are generally absent, and the overburden that is developed above the bedrock comprises fine-grained, silt-poor wind blown sands.
The Fairbreeze A and B blocks apparently represent two parts of a set of strandline deposits separated by a bedrock outcrop. Strandlines represent tabular zones of concentrated heavy mineral accumulations that are preserved by gradual marine regression that leaves the strandline above the level of marine erosion. Block A varies from 18 to 63 m thick, averaging 38 m. Block B is similar to Block A with lower total HM and higher silt and clay contents. Block C is interpreted to be a beach deposit formed on the low energy side of an ancient headland that projected into the sea where heavy minerals accumulated against the headland, while the lighter minerals were continually remobilised by wind transport, resulting in concentration of the heavy minerals. Block C is more homogeneous, averaging 10% to 15% HM with 60% to 80% economic HMs. Both the total grades and proportion of zircon increases with depth. The Fairbreeze Block D represents a set of strandlines deposited to the east of Fairbreeze Blocks A, B and C, during progressive sea-level regression. It has a lower grade and varies in thickness from 18 m in the South to 34 m in the North, with grades averaging from 5% to 8% HM in the strandlines and an economic HM component accounting for approximately 50% of the HM. The Fairbreeze deposits contain an average of 30% silt.
The Hillendale deposit covers an area of approximately 300 ha with reserves and resources as follows:
Proved + Probable reserves - 30 Mt of ore @ 6.9% HM containing 60% Ilmenite, 3.5% Rutile, 8% Zircon, 1.6% Leucoxene.
Measured + Indicated resources - 48.7 Mt of ore @ 3.8% Ilmenite.
The Fairbreeze deposits cover an area of approximately 380 hectares with reserves and resources as follows:
Proved + Probable reserves - 182 Mt of ore @ 6.4% HM containing 60% Ilmenite, 3.3% Rutile, 8% Zircon, 1.7% Leucoxene.
Proved + Probable reserves - 229 Mt of ore @ 6.4% HM containing 3.6% Ilmenite.
The most recent source geological information used to prepare this decription was dated: 2007.
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.
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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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