
In
geology, a lode is a deposit of
metalliferous ore that fills or is embedded in a
fissure (or crack) in a
rock formation or a
vein of ore that is deposited or embedded between layers of rock.
The current meaning (ore vein) dates from the 17th century, being an
expansion of an earlier sense of a "channel, watercourse" in
late Middle English, which in turn is from the 11th-century meaning of ''lode'' as a ‘course, way’.
The generally accepted
hydrothermal model of lode deposition posits that metals dissolved in hydrothermal solutions (hot spring fluids) deposit the gold or other metallic minerals inside the fissures in the pre-existing rocks. Lode deposits are distinguished primarily from
placer deposits, where the ore has been eroded out from its original
depositional environment and redeposited by
sedimentation. A third process for ore deposition is as an
evaporite.
A stringer lode is one in which the rock is so permeated by small veinlets that rather than mining the veins, the entire mass of ore and the enveined
country rock is mined. It is so named because of the irregular branching of the veins into many
anastomosing stringers, so that the ore is not separable from the country rock.
One of largest silver lodes was the
Comstock Lode in Nevada, although it is overshadowed by the more recently discovered
Cannington Lode in Queensland, Australia. The largest gold lode in the United States was the
Homestake Lode. The
Broken Hill Lode in South Australia is the largest lead-zinc lode ever discovered.
See also
*
Lodestone, known just as ''lode'' in the 16th and 17th centuries.
[The ''New Oxford American Dictionary'' (''NOAD''), 3rd edition.][
*Mother lode, the principal vein
*Ore genesis
*Thickness
]
Notes
Category:Ore deposits
Category:Mineralogy
Category:Economic geology
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