Terminology Flashcards
Gauge
Commercially valueless mineral in which ore is found
Carlin-Type Deposit
A sediment-hosted, disseminated gold deposit. Gold is found microscopically within pyrite and arsenopyrite.
Argillization
Replacement of feldspars with clay minerals. Especially in wall rocks adjacent to mineral veins.
Carlin Trend
The largest and most famous trend hosting carlin-type deposits
Calcareous
To be mostly or partly composed of calcium carbonate. Used as a descriptor; “Silty calcareous host rocks”
Sulfidation
The addition of sulfur to a mineral (Fe + 2S -> FeS2)
Epithermal System
network of veins and hydrothermal fluids that permeate the crust of the earth between the magma chamber
and the surface of the earth. Often have economic Au, Ag or Cu deposits.
Supergene Alteration
Alteration that is caused close to the surface, generally by meteoric water.
Hypogene Processes
Processes that occur deep below Earth’s surface and tend to form primary minerals.
Supergene Vs. Hypogene Processes
Hypogene processes occur deep below earth’s surface and tend to create primary minerals, whereas Supergene occurs near the Earth’s surface and tends to create secondary minerals.
Au-Rich Porphyry Copper Deposit
Large, relatively low grade, epigenetic, intrusion-related deposits. These deposits occur close to or in granitic intrusive rocks that are porphyritic in texture.
Skarn
Skarn is a metamorphic rock that has been chemically and mineralogically altered by metasomatism.
Porphyry
“Porphyritic”: Textural term for an igneous rock consisting of large-grained crystals dispersed in a fine-grained silicate rich, generally aphanitic matrix or groundmass. The larger crystals are called phenocrysts.
Metasomatism
The alteration of rocks by hot, chemically-active fluids that flow or diffuse through the rocks and cause recrystallization and compositional change.
Epigenetic
Formed later than the surrounding or underlying rock formation.