DESCRIPTION:
Mining and Mineral Resources

Most of the metallic minerals mined in the world, such as copper, gold, silver, lead, and zinc, are associated with magmas found deep within the roots of extinct volcanoes located above subduction zones. Rising magma does not always reach the surface to erupt; instead it may slowly cool and harden beneath the volcano to form a wide variety of crystalline rocks (generally called plutonic or granitic rocks). Some of the best examples of such deep-seated granitic rocks, later exposed by erosion, are magnificently displayed in California's Yosemite National Park. Ore deposits commonly form around the magma bodies that feed volcanoes because there is a ready supply of heat, which convectively moves and circulates ore-bearing fluids. The metals, originally scattered in trace amounts in magma or surrounding solid rocks, become concentrated by circulating hot fluids and can be redeposited, under favorable temperature and pressure conditions, to form rich mineral veins.

The active volcanic vents along the spreading mid-ocean ridges create ideal environments for the circulation of fluids rich in minerals and for ore deposition. Water as hot as 380 degrees C gushes out of geothermal springs along the spreading centers. The water has been heated during circulation by contact with the hot volcanic rocks forming the ridge. Deep-sea hot springs containing an abundance of dark-colored ore minerals (sulfides) of iron, copper, zinc, nickel, and other metals are called "black smokers." On rare occasions, such deep-sea ore deposits are later exposed in remnants of ancient oceanic crust that have been scraped off and left ("beached") on top of continental crust during past subduction processes. The Troodos Massif on the Island of Cyprus is perhaps the best known example of such ancient oceanic crust. Cyprus was an important source of copper in the ancient world, and Romans called copper the "Cyprian metal"; the Latin word for copper is cyprium.

The Earth's crust, on which we live and depend, is in large part the product of millions of once-active volcanoes and tremendous volumes of magma that did not erupt but instead cooled below the surface. Such persistent and widespread volcanism has resulted in many valuable natural resources throughout the world. ... Over many thousands of years, heated groundwater has concentrated valuable minerals, including copper, tin, gold, and silver, into deposits that are mined throughout the world.

Between 1931 and 1935, Mr. Wade Dean's "Glacier Mining Company" mined solfatara deposits for sulfur in the gently sloping area north of the summit of Mount Adams. The summit crater is the center of the most intensive alteration; primary sulfur deposits occur there with gypsum, alum and silica.

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Gravity and teleseismic studies suggest that a large silicic magma chamber ... lies beneath the Clear Lake volcanic field. This reservoir is thought to be the heat source for The Geysers geothermal field ... Associated epithermal deposits of mercury and gold include the Sulphur Bank Mine (still the site of active mercury deposition) and the McLaughlin Mine (a major disseminated gold deposit in an outlier of the Clear Lake volcanics) ...

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The Ijen volcano complex consists of a group of small stratovolcanoes constructed within the large 20-kilometer-wide Ijen (Kendeng) caldera. The north caldera wall forms a prominent arcuate ridge, but elsewhere the caldera rim is buried by post-caldera volcanoes, including Gunung Merapi stratovolcano, which forms the 2799 meter high point of the Ijen complex. Immediately west of Gunung Merapi is the renowned historically active Kawah Ijen volcano, which contains a nearly one-kilometer-wide, turquoise-colored, acid crater lake. The picturesque lake is the site of a labor-intensive sulfur mining operation, in which sulfur-laden baskets are hand-carried from the crater floor.

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The metal deposits of the southern Cascades are in stockworks or breccia zones and narrow fissure veins, containing only moderate amounts of copper and small amounts of lead, zinc, molybdenum, gold, and silver. Predominant ore minerals are pyrite, magnetite, chalcopyrite, bornite, galena, and sphalerite. At some occurrences these minerals are accompanied by free gold, especially in the oxidized parts of the veins. Common secondary copper minerals associated with chalcopyrite and bornite consist of azurite, malachite, and chrysocolla. Tourmaline is a common accessory mineral at several copper mineralized breccia deposits.

The metal deposits of the southern Cascades are confined to certain areas in the St. Helens and Washougal mining districts. In the Washougal district the deposits occur chiefly along the eastern edge of the Silver Star Granodiorite. In the St. Helens district the deposits occur chiefly in the southeastern part of the Mount Margaret stock, and along the south-central section of the Goat Mountain stock. Outside the boundaries of the St. Helens and Washougal districts, several copper-gold deposits occur in the Camp Creek area of McCoy Creek in north-central Skamania County, whereas the major gold-producing area of southwestern Washington has been the Wind River area of southeastern Skamania County.

The St. Helens and Washougal mining districts, the southernmost mining districts in Washington, are on the western slopes of the Cascade Mountains. The Washougal district includes parts of south-western Skamania County and part of eastern Clark County. The St. Helens district is chiefly in north-western Skamania County, but includes part of north-eastern Cowlitz County and part of south-central Lewis County. Mountainous country prevails throughout both districts. Hillsides are steep and the summits of most mountains are rounded. However, several of the highest mountains contain alpine-type summits characterized by talus-covered slopes and craggy summits. ... In the St. Helens district, elevations range from a low of 600 feet on the Cowlitz River to a high of 5,858 feet on the summit of Mount Margaret. In the Washougal district elevations range from 200 feet on the Washougal River to a high of 4,390 feet on the summit of Silver Star Mountain. The general summit level for the southern Cascade region is around 4,000 feet. Numerous streams form a dendritic drainage pattern in the region. Major drainage systems include the Green, Cowlitz, Lewis, Toutle, Washougal, Cispus, and Wind Rivers.

The majority of the metallic mineral occurrences of southwestern Washington are within the St. Helens and Washougal mining districts; however, these districts have never been major producers of metals in Washington. As early as 1892, mining claims were staked for copper, gold, and silver in the St. Helens district; at the turn of the century discoveries of these metals, as well as lead and zinc, were made in the Washougal district. In the early 1900's many deposits in both districts underwent exploratory and development work, several small shipments of copper ore were made, but no property developed into a major mine. Many mining operations were abruptly halted by devastating forest fires that destroyed much of the virgin timber of the southern Cascades. In the Washougal district, the Yacolt burn of 1902, swept through 290,000 acres of timbered land. Other forest fires, though not as extensive as the Yacolt burn, occurred in 1917, 1918, 1919, 1922, 1927, 1929, and 1936. These fires destroyed the structures at many mines. Some mining operations were resumed, but at many properties mining ceased because capital was no longer available.

Mining History of the Southern Washington Cascades and Mount St. Helens -- Excerpt from: Moen, 1977

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Mining claims for copper, gold, and silver were staked in the St. Helens mining district north of the volcano as early as 1892. ... Mining fever broke out about 1900, and hundreds of claims were staked in the Spirit Lake area as prospectors sought high-grade vein deposits. About 14 tons of copper ore from the Sweden Mine were hauled to a Tacoma smelter in 1905 and used to cast the bronze statue of Sacajawea for the Lewis and Clark Exposition held in Portland, Oregon, which commemorated the 100th anniversary of their expedition. ... Other mines in the area included the Margaret (Earl) group. Although thousands of prospect pits and more than 11,000 feet of underground workings were dug, the veins proved difficult to work and contained only modest amounts of gold and silver. By 1929, most of the mines had been abandoned, although exploratory work continued sporadically until the eruption of 1980.

Mining History of the Southern Washington Cascades and Mount St. Helens -- Excerpt from: Moen, 1977

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