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The Marvelous fissure was also developed at the Mother Lode mine. Some higher grade parts are associated with reddish sandy limestone, breccia, and gouge, suggesting ore deposition within a chimney or similar cavern. The orebody is bordered by copper-bearing disseminations and veinlets except at its base. The orebody has many similarities to the nearby Bonanza vein (MC093), including becoming larger and richer in its lowermost, southwestern parts. The width decreases upwards from a sharp base on a bedding-plane fault near a stromatolite layer 30 meters stratigraphically above the Nikolai Greenstone. It strikes 34-40 E and dips steeply to the southeast. The Mother Lode vein orebody is about 1000 meters long, up to 8 meters wide at its base, and 90 meters high. The breccia zones, thought by MacKevett and others (1997) to be early collapse breccia along solution-enlarged fissures, laterally envelop the orebodies and extend stratigraphically upward above them. These fissures show minor displacement of bedding in the Chitistone Limestone and localize breccia and trangressive dolomite alteration.

Steep, northeast-trending fissures up to 300 meters long are another important control on the location of the major orebodies. The development of intertidal carbonate facies with stromatolites, bacterial mats, gypsum, and anhydrite in the lower Chitistone Limestone is one important control on the development and location of the orebodies.

The base of the mineralization is usually about 27 to 37 meters stratigraphically above the contact of the Chitistone Limestone with the underlying Upper Triassic Nikolai Greenstone. The Mother Lode vein and other nearby orebodies are localized in the lower part of the Upper Triassic Chitistone Limestone. This ore was accessed from both the Mother Lode and Bonanza mines, which developed 12 levels between surface exposures at about 1,800 meters elevation on the Bonanza vein (MC093) to depths at elevations of about 1,450 meters. The largest orebody is the Mother Lode vein, which produced 507,000 tons of ore containing 12.05 percent copper. The Mother Lode mine produced 1,216,000 tons of ore containing 12.39 percent copper. This record largely summarizes information provided by MacKevett and others (1997). MacKevett and others (1997) provide an excellent synthesis and interpretation of the structure, stratigraphy, economic geology, and geochemistry of these deposits. Cobb and MacKevett (1980) refer to the many Federal government publications, dating from the time of the Bonanza discovery in 1900, that contain information about them. Bateman and McLaughlin (1920) and Lasky (1929) provide important descriptions of the geology, mineralogy, and structure of these deposits. No other metals were of economic importance in these orebodies. The estimated 536,000 tons of copper recovered was accompanied by the recovery of about 100 tons of silver (MacKevett and others, 1997). Together they produced 4 million metric tons of ore with a grade of 13 percent copper. These mines developed several different orebodies but their underground workings were interconnected. Geology: The Mother Lode, Bonanza (MC093), Jumbo (MC091), and Erie (MC083) mines, all on the ridge between McCarthy Creek and Kennicott and Root Glaciers, produced significant amounts of high-grade copper ore when they were operated by Kennecott Copper Corporation between 19. The Mother Lode mine is shown on the McCarthy C-5 quadrangle (1993 edition). This is locality 91 of MacKevett (1976) Cobb and MacKevett (1980) included this mine under the name 'Kennecott Copper Corp.'. It is at an elevation of about 5,300 feet, 2,600 feet east of Bonanza Peak (elevation 6983) and about 300 feet east of the center of section 14, T. Location: The Mother Lode mine is at the head of a small cirque valley on the west valley wall of McCarthy Creek (MacKevett, 1970 ). The locality is in the Wrangell-Saint Elias National Park and Preserve.