Orogenic Gold Deposits: Classification and Crustal Distribution

Vocabulary flashcards detailing key terminology, classification criteria, crustal depths, tectonic environments, and representative deposit examples from Groves et al. (1998) on orogenic gold deposits.

Orogenic gold deposits

Epigenetic, structurally hosted gold-bearing quartz-carbonate vein systems formed during compressional to transpressional deformation processes at convergent plate margins in accretionary and collisional orogens, emplaced across a crustal depth range from $15\text{--}20\,\text{km}$ to near-surface environments.

Epizonal orogenic gold deposits

A crustal-depth subclass of orogenic gold deposits formed at depths of less than $6\,\text{km}$ and within a temperature range of $150\text{--}300^\circ\text{C}$.

Mesozonal orogenic gold deposits

A crustal-depth subclass of orogenic gold deposits formed at depths of $6\text{--}12\,\text{km}$ and within a temperature range of $300\text{--}475^\circ\text{C}$.

Hypozonal orogenic gold deposits

A crustal-depth subclass of orogenic gold deposits formed at depths greater than $12\,\text{km}$ and at temperatures exceeding $475^\circ\text{C}$.

Mesothermal deposits (Lindgren classification)

An ore deposit class originally defined by Waldemar Lindgren (1933) as forming at depths of approximately $1.2\text{--}3.6\,\text{km}$ ($1{,}200\text{--}3{,}600\,\text{m}$) and temperatures of $200\text{--}300^\circ\text{C}$, characterized by the absence of high-temperature minerals such as tourmaline, biotite, hornblende, pyroxene, and garnet.

Hypothermal deposits (Lindgren classification)

An ore deposit class defined by Waldemar Lindgren (1933) that formed at depths exceeding $3{,}600\,\text{m}$ and temperatures of $300\text{--}500^\circ\text{C}$, featuring higher-temperature alteration assemblages.

Xenothermal

A classification term coined by Buddington (1935) to describe ore deposits formed under high-temperature conditions at shallow to moderate crustal depths, covering $P\text{--}T$ conditions from leptothermal to hypothermal.

Crustal continuum model

A metallogenic concept proposed by Groves (1993) describing orogenic lode-gold deposition over a continuous vertical crustal profile spanning temperatures of $180\text{--}700^\circ\text{C}$ and pressures of $< 1\text{ to }5\,\text{kbar}$.

Cyclic fault-valve behavior

A structural mechanism described by Sibson et al. (1988) in which extreme fluid-pressure fluctuations within high-angle faults generate flat-lying extensional veins and mutually cross-cutting steep fault veins.

Turkic-type orogen

An accretionary orogenic model described by Sengor and Okurogullari (1991) in which a subduction zone steps progressively seaward, causing a series of gold systems and plutons to develop and become systematically younger towards the trench.

Orogenic gold ore fluids

Low-salinity ($3\text{--}10\,\text{eq. wt}\%\,\text{NaCl}$), near-neutral $H_2O\text{--}CO_2 \pm CH_4$ fluids with elevated $CO_2$ concentrations of $> 5\,\text{mol}\%$ that transport gold as a reduced sulfur complex.

Salsigne gold deposit

An orogenic gold deposit hosted in Cambrian sedimentary rocks of the French Massif Central that represents the world's largest historical producer of arsenic.

Racetrack deposit

An Archaean gold deposit in the Yilgarn craton of Western Australia emplaced at shallow depths ($\le 2.5\,\text{km}$) from $CO_2$-poor fluids, featuring epithermal-like comb, cockade, crustiform, and colloform textures.

Lachlan terrane

A $2{,}000\text{-km}$-wide Palaeozoic turbidite fan sequence in eastern Australia where gold mineralization (such as the Bendigo-Ballarat area) developed via intraplate compressional deformation rather than along suture zones between accreted terranes.

Carlin-type gold deposits

Epigenetic sedimentary rock-hosted gold deposits formed at temperatures of $200\text{--}300^\circ\text{C}$ and depths of $2\text{--}3\,\text{km}$ in regions of back-arc extension and continental crust thinning, characterized by submicron gold, intense silicification, and carbonate dissolution.