Carlin–type gold deposit
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Carlin–type gold deposits are sediment-hosted disseminated gold deposits. These deposits are characterized by invisible gold in arsenic rich pyrite and arsenopyrite. This dissolved kind of gold is cal
Goldstrike (Post–Betze) Mine, Carlin Trend, Nevada, the largest Carlin-type deposit in the world, containing more than 35,000,000 ounces of gold.
Turquoise Ridge (Getchell Mine) gold ore, FoV ~5 /cm across. Grade ~0.35 oz Au/ton. Altered Comus fm. mud/shale with highly contorted bedding (post-depositional, soft-sediment deformation). The rock has been decalcified and weakly silicified.
Coupled substitution
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Coupled substitution is the geological process by which two elements simultaneously substitute into a crystal in order to maintain overall electrical neutrality and keep the charge constant. In formin
Example on bottom where albite (Na Al Si3O8) changes to anorthite (Ca Al2Si2O8), Al3+ replaces Si4+ and Ca2+ for Na+
Diopside can be converted into
Jadeite by coupled substitution