Carrapateena, Khamsin, Fremantle Doctor

South Australia, SA, Australia

Main commodities: Cu Au U
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The Carrapateena iron oxide copper-gold deposit, which is located within the Olympic IOCG Province on the eastern rim of the preserved Gawler craton in northern South Australia, is ~100 km SSE of Olympic Dam and ~130 km north of Port Augusta in South Australia, immediately to the SW of the Carrapateena embayment on the central-western shore of Lake Torrens.

Regional Setting

Carrapateena, Olympic Dam, Prominent Hill, Moonta-Wallaroo and Hillside and all of the other significant known IOCG mineralised systems of the Gawler craton are hosted within Palaeo- to Mesoproterozoic rocks and are distributed along the eastern edge of the currently preserved craton to define the Olympic IOCG Province.

The oldest rocks of the Gawler craton comprise Mesoarchaean to early Palaeoproterozoic metamorphics and igneous suites that form a core to the craton, immediately to the west of the Olympic IOCG Province. On its eastern margin, and within the Olympic IOCG Province, this older nucleus was overlain after ~2000 Ma by the Hutchison Group, a sequence of subaerial to shallow marine clastic and chemical metasedimentary rocks, with minor felsic and mafic volcanic rocks, that were deposited on a continental passive margin (Parker, 1993; Daly et al., 1998). Along the eastern margin of the craton, including the Carrapateena district, the cratonic core and the Hutchison Group were both intruded by ~1850 Ma granitoids of the Donington Suite during the Cornian orogeny (Hand et al., 2007; Reid et al., 2008). This suite is dominated by granodiorite gneiss, with subordinate metamorphosed alkali-feldspar granite, gabbronorite, tonalite and quartz monzonite intrusions with mafic dykes (Ferris et al., 2002). Between ~1770 and 1740 Ma, subsequent to the emplacement of the Donington Suite, extension along the eastern, northern and western margins of the craton, resulted in the development of a series of extensive basins, some of which contain bimodal volcanic rocks, including the Wallaroo Group, which is extensively developed within the Olympic IOCG Province and is an important host to IOCG alteration and mineralisation. During the Palaeoproterozoic, the Curnamona Province is believed to have collided with and been accreted to the Gawler craton in the east. A major linear discontinuity in magnetic and gravity data beneath the Neoproterozoic cover of the Adelaide Geosyncline intracratonic rift complex is interpreted to mark the suture zone (Hayward and Skirrow, 2010, and sources quoted therein). The interval between ~1730 and ~1630 Ma encompasses the Kimban orogeny (1730 to 1690 Ma), Ooldean Event (1660 to 1630 Ma), and the widespread emplacement of various felsic igneous rocks, and formation of several small intracontinental sedimentary basins (Hand et al., 2007).

Towards the close of the Palaeoproterozoic, from ~1630 to 1615 Ma, the Nuyts Volcanics and St Peter Suite bimodal magmas were emplaced in the southwestern part of the Gawler craton, which although poorly exposed, cover an extensive area (Fanning et al., 2007). Between ~1600 and ~1575 Ma the centre of magmatism shifted eastward with the development of the high-volume intrusive Hiltaba Suite and extensive co-magmatic bimodal Gawler Range Volcanics (GRV) to form a large felsic igneous province (covering a preserved area of >25 000 km2) over the central and eastern parts of the Gawler craton, including the Olympic IOCG Province. Between 1580 to 1550 Ma, magmatism progressed eastward to form the Benagerie volcanics and Bimbowrie Suite I- and S-types in the Curnamona Province, the easternmost development of the diachronous eastnortheast-trending corridor of continental I- and A-type magmatism that extends across the Gawler and Curnamona cratons from the St Peter Suite in the southwestern part of the craton (Hayward and Skirrow, 2010).

Known significant IOCG districts/deposits within the Olympic IOCG Province, including Carrapateena, are found where oxidised (magnetite-series), A-type granitoid plutons of the 1595 to 1575 Ma Hiltaba Suite which were emplaced into an accreted Palaeoproterozoic terrane, and where mafic volcanic rocks of the lower GRV are most abundant. These rocks were emplaced during a short-lived episode of NNW-SSE extension that approximately coincided with eruption of the GRV (~1595 to 1590 Ma), preceded and followed by more protracted NW-SE to NNW-SSE contraction (Hayward and Skirrow, 2010).

Tectonism subsequently appears to have migrated northwards and westward, with the ~1570 to 1540 Ma Kararan and 1470 to 1440 Ma Coorabie orogenies respectively. The Archaean to Mesoproterozoic crystalline basement rocks of the Gawler craton were not subjected to any substantial deformation after ~1450 Ma until the early Palaeozoic Delamerian orogeny (Parker, 1993). Much of the Olympic IOCG Province is overlain by flat lying Neoproterozoic to Lower Palaeozoic sedimentary rocks of the Stuart Shelf, equivalents of the sedimentary succession of the Adelaide Geosyncline intracratonic rift complex which separates the Gawler craton and Curnamona Province and was the result of extension preceding and during the rifting and break-up of the Rodinia supercontinent from immediately to the east of the Curnamona Province.

Carrapateena Geology and Mineralisation

The Carrapateena deposit is hosted by strongly brecciated granitoids (variably foliated and/or sheared gneissic quartz-granite and quartz-diorite) which have been dated at 1857±6 Ma and are assigned to the Palaeoproterozoic Donington Suite. It occurs within the core of a north-south oriented, 30 x 100 km mass of that suite, that is overlain 10 to 15 km to the west by ~1590 Ma mafic and felsic volcanic rocks of the Gawler Range Volcanics, which are comagmatic with the Hiltaba Suite granitoids that host the Olympic Dam deposit.

The ore deposit lies beneath a ~470 m thickness of flat lying Neoproterozoic sedimentary rocks, and occupies a north-south elongated area of approximately 800 x 600 m at the unconformity surface with the underlying Palaeoproterozoic host rocks. It is reflected by a broad, weak and diffuse 200 nT magnetic peak and a slightly offset, ellipsoidal, 3.5 km diameter, 2 mGal gravity anomaly.

Mineralisation is confined to a steeply plunging, pipe-like body of hematite and hematite-granite breccia, the Carrapateena Breccia Complex (CBC), which is interpreted to be cut at its centre by an east-west- to eastnortheast-trending complex zone of faulting. To the north of this inferred zone of faulting, the mineralised mass is wedge-shaped, tapering rapidly downward into the fault zone and may conceivably follow that structure to depth.

The Carrapateena Breccia Complex (CBC) varies from heterolithic clast- to matrix-supported hematite-rich breccias. Many of the clasts are milled and rounded such that the 'breccia' may have the appearance of a 'conglomerate' when samples are viewed in isolation. The clasts are predominantly of medium grained, gneissic diorite, with granite gneiss and vein quartz, variably altered to chlorite, sericite and hematite, as well as hematite-dominated clasts of earlier breccia phases within a matrix with a variety of textures that has also been altered to an assemblage of hematite, quartz and sericite. Higher grade copper intersections are typically associated with a grey hematite matrix within strongly brecciated granite.

To the south, the CBC comprises an irregular, ~300 to 400 m diameter, ellipsoidal-cylindrical mineralised body that has been traced by drilling from the unconformity to a depth in excess of 1 km below that surface, from where it continues unclosed.

Mineralisation is zoned laterally outward, and to the north, vertically downward, from bornite to chalcopyrite-bornite to chalcopyrite to chalcopyrite-pyrite. Three kernels of bornite-rich mineralisation have been delineated, one wedge-shaped zone to the northeast that tapers southward into the inferred central zone of faulting, and two steeply plunging elongate zones, one above the other, in the upper and lower parts of the core to the main mineralised pipe-like mass of the CBC in the south.

The principal alteration minerals are hematite, chlorite and sericite, with locally abundant quartz and carbonate (siderite and/or ankerite), and secondary barite, monazite, anatase, magnetite, apatite, fluorite and zircon.

Reserves and Resources

An audited inferred (OZ Minerals, 2011) resource for the main deposit, in the southern half of the deposit area, at a cut-off of 0.7% Cu, totals:
    203 Mt @ 1.31% Cu, 0.56 g/t Au, 0.27 kg/t U
308, 6 g/t Ag;
The northern half, has a potential to contain a further:
    25 to 45 Mt @ 1.0 to 1.1% Cu, 0.4 g/t Au, 0.14 kg U

The estimated Mineral Resource at 31 October 2012 (Oz Minerals ASX Release, 21 January, 2013) has been upgraded to:
    Indicated Resource at
      0.3% Cu cut-off - 392 Mt @ 0.97% Cu, 0.39 g/t Au, 165 ppm U, 4.2 g/t Ag;
      0.5% Cu cut-off - 282 Mt @ 1.20% Cu, 0.48 g/t Au, 197 ppm U, 5.2 g/t Ag;
      0.7% Cu cut-off - 202 Mt @ 1.43% Cu, 0.56 g/t Au, 227 ppm U, 6.2 g/t Ag;
    Inferred Resource at
      0.3% Cu cut-off - 368 Mt @ 0.58% Cu, 0.21 g/t Au, 120 ppm U, 2.3 g/t Ag;
      0.5% Cu cut-off - 193 Mt @ 0.76% Cu, 0.26 g/t Au, 144 ppm U, 2.8 g/t Ag;
      0.7% Cu cut-off -   90 Mt @ 0.96% Cu, 0.30 g/t Au, 162 ppm U, 3.6 g/t Ag;
    Total Resource at
      0.3% Cu cut-off - 760 Mt @ 0.78% Cu, 0.30 g/t Au, 143 ppm U, 3.3 g/t Ag;
      0.5% Cu cut-off - 475 Mt @ 1.02% Cu, 0.39 g/t Au, 175 ppm U, 4.2 g/t Ag;
      0.7% Cu cut-off - 292 Mt @ 1.29% Cu, 0.48 g/t Au, 207 ppm U, 5.4 g/t Ag;

Ore reserves at 18 August, 2014 and mineral resources at 31 November 2013 (OZ Minerals ASX releases), were:
  Indicated + inferred resources at 0.3% Cu cutoff - 800 Mt @ 0.8% Cu, 0.3 g/t Au, 3.3 g/t Ag, 0.155 kg/t U;
  probable reserves, lift 1 from 470 to 970 m below surface - 110 Mt @ 0.9% Cu, 0.5 g/t Au, 5.3 g/t Ag;
  probable reserves, lift 2 from 970 to 1470 m below surface - 160 Mt @ 1.0% Cu, 0.4 g/t Au, 4.3 g/t Ag;
  TOTAL probable reserves - 270 Mt @ 0.9% Cu, 0.4 g/t Au, 4.5 g/t Ag.

JORC compliant Mineral resources as at 25 September 2015 (OZ Minerals press release to the ASX) were as follows, based on a AUD 120/t NSR (AUD=USD 0.78) cut-off:
  Indicated resource - 55 Mt @ 2.4% Cu, 0.9 g/t Au, 11.7 g/t Ag, 335 ppm U;
  Inferred resource 6 Mt @ 2.5% Cu, 0.7 g/t Au, 11.6 g/t Ag, 257 ppm U;
  TOTAL resource 61 Mt @ 2.4% Cu, 0.9 g/t Au, 11.7 g/t Ag, 328 ppm U.

JORC compliant Mineral resources as at 18 November 2016 (OZ Minerals press release to the ASX August, 2017) were as follows, based on a AUD 70/t NSR cut-off:
  Measured resource - 61 Mt @ 1.4% Cu, 0.6 g/t Au, 6.3 g/t Ag;
  Indicated resource - 65 Mt @ 1.6% Cu, 0.6 g/t Au, 7.0 g/t Ag;
  Inferred resource - 8 Mt @ 0.8% Cu, 0.4 g/t Au, 3.5 g/t Ag;
  TOTAL resource 134 Mt @ 1.5% Cu, 0.6 g/t Au, 6.5 g/t Ag.

For more detail see: Porter, T.M., 2010 - The Carrapateena Iron Oxide Copper Gold Deposit, Gawler Craton, South Australia: a Review; in Porter, T.M., (ed.), Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective, v. 3 - Advances in the Understanding of IOCG Deposits; PGC Publishing, Adelaide, pp. 191-200.

Khamsin Deposit

The satellite Khamsin copper-gold deposit, ~10 km to the northwest of Carrapateena, is also an iron oxide copper-gold (IOCG) occurrence. Mineralisation is hosted within the Khamsin Breccia Complex, a polymictic granite-hematite-carbonate breccia which is surrounded by altered Donington Suite granite and some dykes, and is overlain by approximately 460 to 680 m of mostly Neoproterozoic sedimentary cover. Mineralisation occurs as fine- to medium-grained blebby disseminations of chalcopyrite, rare bornite and minor chalcocite, and mostly occur as either disseminations in the breccia matrix or within clasts (OZ Minerals ASX release, 2014).
  The first drill hole into the deposit intersected 440.6 m @ 0.43% Cu, 0.08 g/t Au from 1005.4 m depth, including 26.7 m @ 1.48% Cu, 0.13 Au g/t from 1005.4 m, within a broader zone of 569.6 m @ 0.39% Cu, 0.08 g/t Au from 1003 m (Oz Minerals ASX Release, 21 January, 2013). The hole was drilled at a dip of -55° and azimuth of 173°. This mineralised intersection comprises a strong, grey hematite and chlorite altered, clast and matrix supported, heterolithic granite breccia.
  The alteration and mineralisation style encountered is comparable to that intersected on the margins of the main Carrapateena deposit. This mineralisation coincides with a significant gravity feature that is both larger in size and has the same intense residual gravity response as that related to the Carrapateena deposit. It displays a prominent co-incident magnetic feature located within the central portion of the gravity anomaly. Depths to basement for Khamsin vary between 480 and 630 m below surface (Oz Minerals, 2013).
  The Khamsin prospect was previously the Salt Creek anomaly that was tested by a number of vertical drill holes in the late 1970s and early 1980s following the discovery of Olympic Dam, targeting the gravity and/or aeromagnetic highs. One of these holes, SASC04, was completed at 1250 m and intersected hematite-sericite altered granitoids of the Mesoproterozoic Donington Suite from a depth of 540 m to the bottom of the hole, but without significant sulphide or associated copper mineralisation.

Mineral resources at 26 May 2014 (OZ Minerals ASX release), were:
  Indicated + inferred resources at 0.3% Cu cutoff - 202 Mt @ 0.6% Cu, 0.1 g/t Au, 1.7 g/t Ag, 0.086 kg/t U.

Fremantle Doctor

An arm of the broadly coincident ~1.5 mGal gravity and 200 nT magnetic anomalies that reflect the Carrapateena deposit extend a further 2 km to the north-east overlie the Freemantle Doctor deposit and represent a continuation of iron oxide alteration. This deposit is hosted within Donington Suite granite and is unconformably overlain by ~480 m of unmineralised Neoproterozoic sediment rocks. Mineralisation and alteration is similar to that at Carrapateena.

Mineral Resources at 12 November 2018 (OZ Minerals ASX release), were:
  Inferred resources at 0.4% Cu cutoff - 104 Mt @ 0.7% Cu, 0.5 g/t Au, 3 g/t Ag.

The most recent source geological information used to prepare this summary was dated: 2012.     Record last updated: 6/12/2018
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.

  References & Additional Information
   Selected References:
Hayward N and Skirrow R,  2010 - Geodynamic Setting and Controls on Iron Oxide Cu-Au (±U) Ore in the Gawler Craton, South Australia: in Porter T M, (Ed),  2010 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective PGC Publishing, Adelaide   v.3 pp. 119-146
Katona, L.,  2020 - Geophysical signatures of IOCG prospects in the Olympic Cu-Au Province: in    Mesa Journal   v.92, pp. 26-37.
Porter T M,  2010 - The Carrapateena Iron Oxide Copper Gold Deposit, Gawler Craton, South Australia: a Review: in Porter T M, (Ed), 2010 Hydrothermal Iron Oxide Copper-Gold and Related Deposits: A Global Perspective PGC Publishing, Adelaide   v.3 pp. 191-200
Zhu, Z.,  2016 - Gold in iron oxide copper-gold deposits: in    Ore Geology Reviews   v.72, pp. 37-42.

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 takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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