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Klondike Gold District |
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Yukon Territory, Canada |
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Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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The Klondike gold deposits are located near Dawson City in the central western section of the Yukon Territory of northern Canada.
The great bulk of the 300 tonnes of gold taken from the district (to 1993) has come from placers, with less than 0.5% being from hard rock lode deposits. There has been controversy as to whether the alluvial gold originated from the numerous, dispersed gold-quartz veins in the region or from Plio-Pleistocene epithermal alteration of young gravels which has been demonstrated to occur locally.
The mesothermal gold bearing quartz veins are of earliest Cretaceous age and hosted by Permian middle to upper greenschist facies meta-sediments and meta-igneous rocks of the Yukon-Tanana terrane. They occur in brittle, extensional structures formed during the late Jurassic to early and middle Cretaceous uplift which followed the early Jurassic imbrication. The veins are massive, un-banded quartz with localised carbonate flooding and/or pyritisation of the wall rocks.
The only significant lode deposit exploited was the Lone Star mine which yielded 30 kg of fine gold from 7650 t of ore grading 5.1 g/t Au.
The Klondike placer gold accumulations are located in the un-glaciated portion of the western Yukon Plateau which was formed during the Tertiary and slopes gently to the south. The White Channel Deposits of Pliocene to early Pleistocene age and the glacio-fluvial deposits of the Klondike Gravels filled the valleys draining this Plateau. The Klondike Gravels do not carry economic gold concentrations as they are the result of a regional glaciation. Subsequent incision by down cutting streams developed another two levels of gravel deposition in the district.
The White Channel Deposits are up to 35 m thick and formed terraces up to 50 to 100 m above the present stream levels. They are composed of 14 different lithofacies ranging from laminated silt and clay to disorganised massive boulder gravel, although sorting and stratification generally increases upwards in the sequence, with the top 15 m being interbedded with the Klondike Gravels.
Economic gold is not found in the well sorted sediments of the White Channel Deposits, but is only concentrated in the lower few metres, characterised by poorly sorted gravelly lithologies immediately above bedrock. The White Channel sediments have been subjected to an almost complete replacement of igneous and metamorphic silicates by clays as a result of early Pleistocene hydrothermal activity at less than 200° C. This alteration is dominantly in the form of kaolinitic clay which is geochemically anomalous with respect to base metals and sulphur. Gold is found in both placer deposits and in colluvium, particularly near and downslope of known lode gold occurrences. As well as the accumulations in the White Channel deposits, placer gold is also found in river terrace and stream gravels deposited by incised streams following the Klondike Gravels.
For more detail consult the reference(s) listed below.
The most recent source geological information used to prepare this decription was dated: 1999.
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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Selected References:
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Chapman R J, Mortensen J K, Crawford E C and Lebarge W, 2010 - Microchemical Studies of Placer and Lode Gold in the Klondike District, Yukon, Canada: 2. Constraints on the Nature and Location of Regional Lode Sources : in Econ. Geol. v.105 pp. 1393-1410
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Chapman R J, Mortensen J K, Crawford E C and Lebarge W, 2010 - Microchemical Studies of Placer and Lode Gold in the Klondike District, Yukon, Canada: 1. Evidence for a Small, Gold-Rich, Orogenic Hydrothermal System in the Bonanza and Eldorado Creek Area : in Econ. Geol. v.105 pp. 1369-1392
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Knight J B, Morison S R, Mortensen J K 1999 - The relationship between placer Gold particle shape, rimming and distance of fluvial transport as exemplified by Gold from the Klondike district, Yukon Territory, Canada: in Econ. Geol. v94 pp 635-648
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Knight J B, Mortensen J K, Morison S R 1999 - Lode and placer Gold composition in the Klondike district, Yukon Territory, Canada: implications for the nature and genesis of Klondike placer and lode Gold deposits: in Econ. Geol. v94 pp 649-664
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MacKenzie D J, Craw D and Mortensen J, 2008 - Structural controls on orogenic gold mineralisation in the Klondike goldfield, Canada: in Mineralium Deposita v43 pp. 435-448
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Rushton R W, Nesbitt B E, Muehlenbachs K 1993 - A fluid inclusion and stable isotope study of Au Quartz veins in the Klondike district, Yukon Territory, Canada: a section through a Mesothermal vein system: in Econ. Geol. v88 pp 647-678
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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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