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Examples of alluvial deposits

The Cariboo, British Columbia.

The Cariboo, with Barkerville its capital, was the premier placer gold district of British Columbia. It lies in the central part of the province within the plateau region bounded by the Coast Range on the west and Cariboo and other mountain ranges on the east. The placer gold production of the district is probably of the order of 2.5 to 3 million ounces.

The Cariboo is a deeply dissected region with low rounded hills and an irregular pattern of streams, creeks and gulches. The weathering and erosion that gave rise to the dissection of the country evidently originated in early Tertiary time and extended throughout that period. In Pleistocene time a stagnant ice sheet lay over the land, removing much of the weathered mantle at higher elevations but having little effect on the placer deposits in most of the valleys. The bedrock is folded and faulted phyllite, quartzite, argillite, slate and limestone of the lower Paleozoic Cariboo Group. These enclose a host of quartz bodies ranging from stringers, blows and boudins to fairly well defined quartz-vein zones and siliceous replacements in the limestones. All these deposits are auriferous, some of the vein zones and siliceous replacements having been mined extensively. The principal minerals in the auriferous deposits are pyrite, galena, chalcopyrite, sphalerite, cosalite, bismuthinite, arsenopyrite, pyrrhotite, scheelite and free gold.

The placers of the Cariboo (Barkerville) district, discovered in 1860, are now largely exhausted after having yielded probably over 2.5 million ounces of gold. The principal productive creeks were Williams and Lightning, but a number of shorter creeks produced considerable quantities of gold. Several types of auriferous gravels are found in the district, and the gold has had a complex history following its release from the deposits and rocks during extensive oxidation and erosion in Tertiary time. First there was an extensive accumulation of gravels and gold in the valleys during a gradual period of Tertiary uplift. This was followed in Pleistocene time by the development of valley glaciers and stagnant ice sheet, the later protecting the Tertiary gravels from scouring and destruction. Slight uplift after the disappearance of the glaciers rejuvenated the streams forming auriferous gravels:

(1) Ancient stream gravels resting on the bedrock.
These averaged 1.7 m. in thickness and were the richest and most important of the auriferous gravels. Quarts pebbles were rare. The gravels consisted of weathered and water-worn pebbles of country rock. The gold was coarse, very little flour or fine scale gold being present. The accompanying heavy minerals were pyrite, scheelite, galena and barite.

(2) Interglacial stream gravels.
The gold in these gravels was essentially the same as mentioned above. Most of pay streak were lean but fairly extensive.

(3) Auriferous glacial outwash gravels.
The gold was very disseminated in these gravels with uneconomical values.

(4) Postglacial stream gravels.
Some were very productive, but the pay streaks were thin. Some of the gold was in the surface gravels on the benches was coarse, but the majority was scattered and fine.

The placer gold of this district varied in fineness from 775 to 950 as compared with the vein gold, which varied from 850 to 910.

The Choco, Colombia.

The Choco and other districts of Colombia were worked since early times with batea and calabash pans. The placers are river and bench gravels that yield abundant Au/Pt in ratios from 100:1 to 1:3. The country rocks are Tertiary conglomerates, sandstones, shales and various types of volcanics and serpentinized basic intrusives. Quartz veins with gold, silver, lead and zinc are widespread at the contact zones between tertiary granite intrusives and andesites, greenstones and metasediments.

The Guiana Shield, Venezuela and Guyana

The alluvial placers of this district are characterized by very fine gold particles (70% < 140 mesh) disseminated in gravels and sands mainly derived from Roraima Plateau sandstones and conglomerates. The origin of gold is still questionable as a relative absence of primary deposits hardly justifies the existence of very large and widespread volumes of gold placers. The pay streaks are very rich (1 to 10 g Au/m3) in upper parts of Roraima plateaux and diminishing downstream. As in Colombia, platinoids are present in gravels.

In resent placers gold is commonly accompanied by small to moderate amounts of native platinoids, particularly in terrains characterized by ultrabasic or basic intrusives with associated Ni-Cu-Co sulphide deposits.

In addition to gold, many placers with platinoids have alluvial diamonds in economical grades (0.24 cts/m3).

There are three sources of gold, in order of importance, according to writer's research:
(1) An extensive paleoplacer (conglomerate) within the Roraima plateaux, which yields coarse gold often presenting crystallized forms (960 fineness).
(2) Basic intrusives (gabbroic) quartz rich, presenting extensive pyritization and sericitization, intrusives. Gold derived from this source is characterized by very fine round particles (870 - 920 fineness) dispersed in gravels. The presence of secondary pyrite in pay streaks and absence of any mechanical abrasions or flattening suggests that chemical transport is involved. The source is disseminated pyrite within the intrusive bodies.
(3) Precambrian greenstones related gold-quartz, gold-quartz-pyrite and quartz-gold-tourmaline veins (860 fineness).


The origins, according to writer's observations, of alluvial diamonds are:

(1) Uranium-thorium-bearing conglomerate within Roraima plateau. Diamonds derived from this source are colored green to brown by radioactivity.

(2) Very thick (up to 500 m.) subvertical dikes (possibly volcanic root feeders) in Precambrian country rocks. These diamonds present zirconium inclusions and are not colored by radioactivity.


Boyle R. W., 1979: The geochemistry of gold and its deposits, Canada Geol. Survey Bull. 280, 584 p.
Averill, C.V. 1946: Placer mining for gold in California. Div. Geol. Mines, Bull., 135, 377 p.
Barkovskaya, M.B. 1963: Some features of the formation of economic grade heavy minerals concentration in basins of deposition; Econ. Geol., v. 58, p. 1357-1358
Bateman, A.M. 1950: Economic mineral deposits, 2nd. ed.; John Wiley & Sons, Inc., New York, 916 p.
Bilibin, Y.A. 1938: The principles of placer geology; G. O. N. T. I., Moscow, 505 p.
Boericke, W.F. 1933: Prospecting and operating small gold placers, John Wiley & Sons, Inc., New York, 136 p.
Crane, W.R. 1908: Gold and silver; John Wiley & Sons, Inc., New York, 727 p.
Crampton, F.A. 1937: Occurance of gold in stream placers; Mining J., v. 20, no. 16, p. 3-4, 33-34.
Fayzullin, R.M. 1968: Problem of intermediate collectors of gold; Int. Geol. Rev., v. 10, no. 12, p. 1383-1385.
Fisher, M.S. 1935: The origine and composition of alluvial gold, with special reference to the Morobe goldfield, New Guinea; Inst. Min. Metall. Bull. London, no. 365, p. 1-46.
Fricker, A.G. 1976: Placer gold-measurement and recovery; Symp. on Sampling Practices in the Mineral Ind.; Australas Inst. Min. Metall., Parkville, Australia, p. 115-127.
Gardner, E.D. and Johnson, C.H. 1934: Placer mining in the western United States;
Pt. I, General information, hand shoveling, and ground sluicing; U.S. Bur. Mines, Inform. Circ. 6786, 74 p.:
Pt. II, Hydraulicking, treatment of placer concentrates, and marketing of gold; U.S. Bur. Mines, Inform. Circ. 6787, 89 p.:
Pt. III, Dredging and other forms of, mechanical handling of gravel, and drift mining; U.S. Bur. Mines, Inform. Circ. 6788, 82 p.
Griffith, S.V. 1960: Alluvial prospecting and mining, 2nd. Ed.; Pergamon Press, Inc., New York, 245 p.
Gruttennk, J.A. 1950: The origin of the residual gold deposits of Surinam (Dutch Guyana); Geol. Mijnhouw, no.3, p. 89-93.
Gorbunov, F.Z. 1959: On the distances travelled by alluvial gold from its native sources; Sov. Geol., no.6, p.98-l05.
Harrison, H.L.H. 1962: Alluvial mining for tin and gold; Mining Publications, Ltd., London, 313 p.
Idriess, I.L. 1933: Prospecting for gold, 4th ed.; Angus and Robertson, Ltd., Sydney, Australia, 293 p.
1934: Gold-dust and ashes; the romantic story of the New Guinea goldfields; Angus and Robertson, Ltd., Sydney. Australia, 285 p.
Ivensen, Y.P., Levin, V.I. and Nuzhnov S.V. 1963: Placer deposits. Gold-bearing conglomerates; Str. Zemnoi Kory Yakutii Zakonomer. Razmeshcheniya Polez. Iskop., Y. P. Ivensen, ed., Izd. "Nauka", Moscow, U.S.S.R., p.325-330. (Chem. Abstr., v. 73, 27541w.)
1969: The types of fossil gold placers in various formations and methods of prospecting for them; USSR Acad. Sci., Sib. Div., Yakutsk Branch, "Nauka" Publishing House, Moscow, 210 p.
Johnston, W.A. and Uglow, W.L. 1926: Placer and vein gold deposits of Barkerville, Cariboo district, British Columbia; Geol. Surv. Can., Mem. 149, 246 p.
Lindgren, W. 1894: An auriferous conglomerate of Jurassic age from the Sierra Nevada; Am. J. Sci., ser. 3, v. 47, p. 275-280.
1895: Characteristic features of California gold-quartz veins; Geol. Soc. Am., Bull., v. 6, p. 221-240.
1896: The gold-quartz veins of Nevada City and Grass Valley districts, California; U.S. Geol. Surv., 17th Annu. Rep., Pt. 2, p. 1-262.
1901: Metasomatic processes in fissure-veins; Am. Inst. Mm. Eng., Trans., v. 30, p. 578-692.
1902: Test for gold and silver in shales from western Kansas; U.S. Geol. Surv., Bull. 202, 21 p.
1905-1906: Metasomatic processes in the gold deposits of western Australia; Econ. Geol., v. I, p. 530-544.
1906: Occurrence of albite in the Bendigo veins; Econ. Geol., v. I, p. 163-166.
1909: Metallogenetic epochs; Econ. Geol., v. 4, p. 409-420.
1910: The hot springs of Ojo Caliente and their deposits; Econ. Geol., v.5, p.22-27.
1911: The Tertiary gravels of the Sierra Nevada of California; U.S. Geol., Surv., Prof. Pap. 73, 226 p.
1915: Processes of mineralization and enrichment in the Tintic mining district; Econ. Geol., v. 10, p. 225-240.
1917: Gold and silver deposits in North and South America; Am. Inst. Mm. Metall. Eng., Trans., v. 55, p. 883-909.
1920: Vein filling at Bendigo, Victoria; Econ Geol., v. 15, p. 312-314.
1927: Magmas, dikes, and veins; Am. Inst. Mm. Metall. Eng., Trans., v. 74, p. 71-126.
1933: Mineral deposits, 4th ed.; McGraw-Hill Book Co., Inc., New York, 930 p.
1937: Succession of minerals and temperatures of formation in ore deposits of magmatic affiliations; Am. Inst. Mm. Metall. Eng., Trans., v. 126, p. 356-376.
Liversidge, A.
1893a: On the origin of moss gold; J. R. Soc. N.S.W., v. 27. p. 287-298.
1893b: On the condition of gold in quartz and calcite veins; R. Soc. N.S.W., v. 27, p. 299-303.
1893e: On the origin of gold nuggets; R. Soc. N.S.W., v. 27, p. 303-343.
1893d: On the crystallization of gold in hexagonal forms; R. Soc. N S W v. 27, p. 343-346.
1897a: Presence of gold in natural saline deposits and marine plants; J. Chem. Soc. (London), v.71, p.298-299.
1897b: The crystalline structure of gold and platinum nuggets and gold ingots; 3. Chem. Soc. (London), v. 71, p. 1125-1131.
MacKay, B.R. 1921: Beauceville map-area, Quebec; Geol. Surv. Can., Mem. 127, 105 p.
McConnell, R.G. 1905: Report on the Klondike gold fields; Geol. Surv. Can., Annu. Rep., Pt. B, v.14, p. l-7l. Also Geol. Surv. Can. Mem. 284, p. 64-113.
1907: Report on gold values in the Klondike high-level gravels; Geol. Surv. Can. Rep. No. 979, 34 p. Also Geol. Surv. Can., Mem. 284, p. 217-238.
Mertie, J.B. 1921: Lode mining in the Juneau and Ketchikan districts; in Mineral resources of Alaska; U.S. Geol. Surv. Bull. 714, p. 105-128.
1940: Placer gold in Alaska; J. Wash. Acad. Sci., v. 30, p. 93-124.
1954: The gold pan: a neglected geological tool; Econ. Geol., v. 49, p. 639-65.
1969: Economic geology of the platinum metals; U.S. Geol. Surv., Prof. Pap. 630, 120 p.
Park, J. 1897: The geology and veins of the Hauraki goldfields; N.Z., Inst. Mm. Eng., Session 1897, 105 p.
1908: The geology of the Cromwell subdivision western Otago division; NZ., Geol. Surv., Bull. No. 5, (New Series) 92 p.
1927: A textbook of mining geology; Charles Griffin and Co. Ltd., London.
Raeburn, C. and Milner, R.H. 1927: Alluvial prospecting; Thomas Murby & Co., London, 478 p.
Romanowitz, C.M., Bennett, H.J. and Dare, W.L. 1970: Gold placer mining: Placer evaluation and dredge selection; U.S. Bur. Mines, Inform. Circ. 8462, 56 p.
Shilo, N.A. 1956: Some peculiarities of placer formation in the zone of permafrost development; Sov. Geol., v. 53, p. 102-117.
1960: The role of subpolar climate in the formation and disposition of placer deposits; in The principles of the disposition of useful minerals IV, Placer deposits; U.S.S.R. State Sci. Tech. Publ. House Lit. Mining, p. 2029.
1963: Some features of the composition of alluvial placers in the Yana-Kolyma belt; Tr. Sev. Vost. Kompleks. Nauch. Issled. Inst. no. 3, p. 87-l05. (Chem. Abstr., v. 61, 9304e.)
1968: Certain problems of auriferous lodes and placers; Int. Geol. Rev., v. 10, no. 11, p. 1241-1246.
1970a: Placer-forming ore formation and their relation to placer deposits Probl. Geol. Rossypei, Soveshch., (DokI.) 3rd, 1969, V.I. Smirnov, ed., Sev. Vost. Kompleks. Inst.; Magadan, U.S.S.R., p. l3-24. (Chem. Abstr., v. 75, 23807f.)
1970b: Placer-forming minerals and placer deposits; Pacific Geol., no. 2, p. 29-33. (Chem. Abstr., v. 74, 14825n.)
1971: The problems of the geology of gold; Earth-Sci. Rev., v. 7, p. 215-225.
1973: Metal content of placers of the northwestern Pacific area; Aust., Bur. Mm. Resour., Geol. Geophys. Bull., no. 141, p. 221-222.
1974: Gold and gold-silver inineralization in the Okhotsk-Chukotka volcanic belt and some problems of ore formation; Zap. Leningrad. Gorn. Inst., v. 67, no. 2, p. 20-34. (Chem. Abstr., v. 83, 82774f.)
Trofimov, V.S. 1964: Basic factors controlling the formation and location of mineral placers; Lithol. Miner. Resour., no. 6, p. 5-18.
1969: The origin of gold in certain ancient conglomerates; in The problem of the occurrence of metals in ancient conglomerates in the U.S.S.R.; "Nauka" Publ. House, Moscow-Leningrad, p. 58-63.
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Tyrrell, J.B. 1912: The law of the pay-streak in placer deposits; Inst. Mm. Metall., Trans., v. 21, p. 593-613.
1915: Gold on the North Saskatchewan River; Can. Mm. Inst., Trans., v. 18, p. 160-173.
Weatherbe, D. 1907: Dredging for gold in California; Mining Scientific Press, San Francisco, 217 p.
Wells, J.H. 1973: Placer examination Principles and Practice; U.S. Dep. Interior, Bur. Land Management, Tech. Bull. 4, 204 p.
West, J.M. 1971: How to mine and prospect for placer gold; U.S. Bur. Mines, Inform. Circ. 8517, 43 p.
1975: Gold; U.S. Dep. Interior, Bur. Mines, Miner. Year b., v. 1, 1974, p. 603-626.

[ Placer Deposits 1  2  3  Eluvial  5  6  Alluvial  8  9  10  Examples  12  13  14  15 ]

Maps of alluvial gold deposits in: California, Western Canada, Eastern Canada, Russia, World
Maps of primary gold deposits in: Precambrian, Paleozoic, Mesozoic, Cenozoic Rocks

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March, 2011