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Diamond Deposits, Replacement Deposits, SEDEX Deposits,
silver and/or base metal sulphides with gangue minerals of quartz, calcite, adularia, baryte and
fluorite. Alteration minerals include quartz, adularia, illite, chlorite and kaolinite. Permeability and structures exert a strong control on the location of these deposits. Fluid origins are dominantly
meteoric with the metals deriving from either deep magmatic sources or from leaching of the host volcanics/sediments. Epithermal deposit generally occur as veins, breccias or disseminations.
Adularia-Sericite Model
Acid Suplhate Model
magmatic and meteoric fluid origins.
Carlin-type deposit model
sequences. They are generally formed by the exhalation of hot, metal rich fluids onto the seafloor
and have strong connections with the modern day "black smoker" deposits formed at spreading
ridges. The deposits represent major sources of copper, zinc, lead, gold and silver in a high grade
low tonnage ratio. Gangue minerals exist in the form of quartz, chlorite, barite, gypsum and
carbonate. Also known as volcanic-exhalative deposits in contrast to the similar SEDEX
(sedimentary exhalative) deposits which are formed in sedimentary sequences.
VMS Deposit Model
rocks and alluvial deposits formed by the erosion of these deposits. The deposits form as clusters
with a pipe like form and are produced by an explosive volcanic eruption just below a volcanic
vent.. The diamonds are thought to form at depths of 150-300km and brought to the surface as xenocrysts in kimberlite/lamproite magmas. The magmas must rise to the surface at a speed of
around 70km/hr in order to prevent re-equilibriation of the carbon to graphite.
Diamond Deposit Model
These deposits form by metasomatism which is the addition or subtraction of material
by hot fluids.
Greisen Deposit Model
Skarn Deposit Model
SEDEX Deposit Model
Information in the text gathered from Evans 1997: Ore Geology and Industrial Minerals, and
my own study collections.
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