| Mafic rock | |
 Troctolite 76535 from the Apollo 17 landing site | |
| Composition | |
|---|---|
| olivine, calcic plagioclase, minor pyroxene |
Troctolite /ˈtrɒktəlaɪt/ (from Greek τρώκτης 'trout' and λίθος 'stone') is a mafic intrusive rock type. It consists essentially of major but variable amounts of olivine and calcic plagioclase along with minor pyroxene. It is an olivine-rich anorthosite, or a pyroxene-depleted relative of gabbro. However, unlike gabbro, no troctolite corresponds in composition to a partial melt of peridotite. Thus, troctolite is necessarily a cumulate of crystals that have fractionated from melt.[1]
Troctolite is found in some layered intrusions such as in the Archean Windimurra intrusion of Western Australia, the Voisey's Bay nickel-copper-cobalt magmatic sulfide deposit of northern Labrador,[2] the Stillwater igneous complex of Montana, the Duluth Complex of the North American Midcontinent Rift,[3] and the Tertiary Rhum layered intrusion of the island of Rùm, Scotland.[4] Troctolite is also found, for example, in the Merensky Reef of the Bushveld Igneous Complex, South Africa and in the Lizard complex in Cornwall.[5]
