|
Tolukuma |
|
|
Papua New Guinea |
| Main commodities:
Au Ag
|
|
 |
|
|
 |
Super Porphyry Cu and Au
|
IOCG Deposits - 70 papers
|
All papers now Open Access.
Available as Full Text for direct download or on request. |
|
|
The Tolukuma low sulphidation adularia-sericite epithermal gold deposit is located in the Central province of Papua New Guinea, some 100 km north of Port Moresby.
The oldest rocks in the district surrounding Tolukuma are the Kagi Metamorphics, the metasedimentary section of the Cretaceous to Eocene Owen Stanley Metamorphics which were deformed during the middle Miocene. Locally the Kagi Metamorphics are known as the Auga Beds, comprising slate, siltstone, sub-greywacke, feldspathic sandstone, limestone and pebble conglomerate, which locally contain zones of highly carbonaceous material. Unconformably overlying the Owen Stanley Metamorphics are the late Miocene to Pliocene volcanics and intercalated sediments with sub-volcanic intrusions of the Mt Davidson Volcanics equivalents, a basic to intermediate volcanic complex developed within a north-south trending 10 to 20 km wide graben. These volcanics and sediments host the Tolukuma mineralisation. Pliocene deformation produced NW and NE trending, near vertical tensional fractures with little displacement.
In the Tolukuma deposit area the Kagi Metamorphics are in probable fault contact with the Mt Davidson Volcanics equivalents. The latter are the host to the mineralisation and comprise intermediate to basic pyroclastics (fine ash flow, feldspathic crystal and crystal lithic tuff to agglomerate) and lavas (andesites and basalts, but predominantly hornblende-feldspar porphyritic andesites) cut by frequent narrow dykes of porphyritic andesite to basalt.
Gold mineralisation is present in several sub-vertical quartz vein zones within the Mt Davidson Volcanics equivalents, located along two 115° striking faults that are 500 m apart and also in a north trending dilational zone connecting these two structures. The veining ranges form 1 to >10 m in thickness, averaging 2 to 3 m. The southern fault and dilational zone are the Tolukuma vein, the northern is the 120 vein, with the majority of the >5 g/t Au being within the former while lower and more erratic grades are in the 120 vein and the northern parts of the Tolukuma vein. High grade (>5 g/t Au) mineralisation occurs over a maximum vertical interval of 275 m.
Mineralised veins are predominantly quartz (where stongly mineralised it is a white, saccharoidal variety with abundant pseudomorphs after carbonates) with variable pyrite and lesser (generally <1%) base metal sulphides. Accessories include clay, manganosiderite, adularia, albite and leucoxene. Adularia is a common accessory associated with vein quartz. The vein types recognised include simple and banded veins, vein breccias, brecciated veins and hydrothermal breccias. Alteration includes early pervasive propylitisation, while phyllic (illite-quartz-pyrite) and argillic (illite-smectite) haloes extend up to several tens of metres outward from the veins into the host rocks.
The drill indicated resource quoted in 1988 was 1.07 Mt @ 22.0 g/t Au at a cut-off of 4 g/t Au.
Reserves and resources in 2003 are quoted as (from Durban Roodepoort Deep Ltd, website):
Proven+probable reserve - 0.16 Mt @ 15 g/t Au for 2.4 t Au
Measured+indicated+inferred resource - 0.3 Mt @ 29.9 g/t Au for 9.0 t Au
For detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 2003.
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.
|
|
|
|
Langmead R P, McLeod R L 1990 - Tolukuma Gold deposit: in Hughes F E (Ed.), 1990 Geology of the Mineral Deposits of Australia & Papua New Guinea The AusIMM, Melbourne Mono 14, v2 pp 1777-1781
|
|
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.
|
Top | Search Again | PGC Home | Terms & Conditions
|
|
