ﺎﮭﺒﺳاورو ﮫﯿﺋﺎﻣﺮﺤﻟا ﻞﯿﻟﺎﺤﻤﻟا ﺎﮭﺒﺳاورو ﮫﯿﺋﺎﻣﺮﺤﻟا ﻞﯿﻟﺎﺤﻤﻟا
Hydrothermal Solutions and their Mineral Hydrothermal Solutions and their Mineral
Deposits Deposits
n
ﻰﺘﻟا ﺐﺳاوﺮﻟا ﻚﻠﺗ ﻰھ ﮫﯿﺋﺎﻣﺮﺤﻟا ﮫﯿﻧﺪﻌﻤﻟا ﺐﺳاوﺮﻟاو تﺎﻣﺎﺨﻟا n
ﻰﺘﻟا ﺐﺳاوﺮﻟا ﻚﻠﺗ ﻰھ ﮫﯿﺋﺎﻣﺮﺤﻟا ﮫﯿﻧﺪﻌﻤﻟا ﺐﺳاوﺮﻟاو تﺎﻣﺎﺨﻟا ﮫﻔﻠﺘﺨﻣ هراﺮﺣ تﺎﺟرد ﻰﻓو ﮫﻧﺪﻌﻤﻣ ﮫﯿﺋﺎﻣ ﻞﯿﻟﺎﺤﻣ ﮫﻄﺳاﻮﺑ نﻮﻜﺘﺗ ﮫﻔﻠﺘﺨﻣ هراﺮﺣ تﺎﺟرد ﻰﻓو ﮫﻧﺪﻌﻤﻣ ﮫﯿﺋﺎﻣ ﻞﯿﻟﺎﺤﻣ ﮫﻄﺳاﻮﺑ نﻮﻜﺘﺗ ..
n
،ﺮﺻﺎﻨﻌﻟا ﻢﻈﻌﻤﻟ ﮫﻋﻮﻨﺘﻣو هﺮﯿﺒﻛ ﮫﻋﻮﻤﺠﻣ ﺐﺳاوﺮﻟا هﺬھ ﻢﻀﺗ n
،ﺮﺻﺎﻨﻌﻟا ﻢﻈﻌﻤﻟ ﮫﻋﻮﻨﺘﻣو هﺮﯿﺒﻛ ﮫﻋﻮﻤﺠﻣ ﺐﺳاوﺮﻟا هﺬھ ﻢﻀﺗ تﺎﻣﺎﺨﻟا هﺬھ ﮫﻠﺜﻣأ ﻦﻣو تﺎﻣﺎﺨﻟا هﺬھ ﮫﻠﺜﻣأ ﻦﻣو ::
..١١
ﮫﯿﻠﺘﻜﻟا ﮫﯿﻧﺎﻛﺮﺒﻟا تاﺪﯿﺘﯾﺮﺒﻜﻟا ﺐﺳاور ﮫﯿﻠﺘﻜﻟا ﮫﯿﻧﺎﻛﺮﺒﻟا تاﺪﯿﺘﯾﺮﺒﻜﻟا ﺐﺳاور Volcanogenic
Volcanogenic
Massive Sulfide (VMS) Deposits Massive Sulfide (VMS) Deposits
..٢٢
ﮫﯿﻗﺮﻌﻟا ﺐﺳاوﺮﻟا ﮫﯿﻗﺮﻌﻟا ﺐﺳاوﺮﻟا Vein Deposits
Vein Deposits
..٣٣
ىﺮﯿﻓرﻮﺒﻟا سﺎﺤﻨﻟا ﺐﺳاور ىﺮﯿﻓرﻮﺒﻟا سﺎﺤﻨﻟا ﺐﺳاور Porphyry Copper Deposits
Porphyry Copper Deposits
..٤٤
نرﺎﻜﺴﻟا ﺐﺳاور نرﺎﻜﺴﻟا ﺐﺳاور Skarn Deposits
Skarn Deposits
Origins of the Solutions Origins of the Solutions
n
n
Magmatic Sources Magmatic Sources
n
n
Meteoric water (ground water) sources Meteoric water (ground water) sources
n
n
Seawater sources Seawater sources
n
n
Regional Metamorphism ! Regional Metamorphism !
hydrothermal
system
Composition of the Solutions Composition of the Solutions
n
n The principle ingredient of hydrothermal solutions is a The principle ingredient of hydrothermal solutions is a brine
brine –– hot waterhot water
n
n Containing dissolved salts such as NaCl, KCl, CaSOContaining dissolved salts such as NaCl, KCl, CaSO4 4 and CaCl
and CaCl22
n
n The range in salinity varies from that of seawater to The range in salinity varies from that of seawater to about ten times the salinity of seawater
about ten times the salinity of seawater
n
n Capable of dissolving small amounts of elements such as Capable of dissolving small amounts of elements such as Au, Ag, Cu, Pb and Zn
Au, Ag, Cu, Pb and Zn
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n High temperatures increase the effectiveness of High temperatures increase the effectiveness of the brines to dissolve metals
the brines to dissolve metals
Causes of Mineral Precipitation Causes of Mineral Precipitation
n
n a convection cell is required to maintain a a convection cell is required to maintain a constant precipitation
constant precipitation
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n Rapid movement of the fluid into porous layers Rapid movement of the fluid into porous layers (open fractures such as veins and brecciated
(open fractures such as veins and brecciated rocks
rocks) )
n
n Sudden cooling of the fluids leads to rapid Sudden cooling of the fluids leads to rapid
precipitation of minerals over a limited region precipitation of minerals over a limited region
n
n Boiling, rapid pressure decrease, reactions with Boiling, rapid pressure decrease, reactions with adjacent rock types, and mixing with seawater adjacent rock types, and mixing with seawater can also cause rapid precipitation and the
can also cause rapid precipitation and the concentration of mineral deposits.
concentration of mineral deposits.
Fumaroles
Fumaroles
Fumaroles
Hot Spring
Divergent Plates (MOR)
VMS Black Smoker
Characteristics of VMS Deposits Characteristics of VMS Deposits
n
n VMS deposits are major sources of Cu and Zn VMS deposits are major sources of Cu and Zn and significant quantities of Au, Ag, Pb, Se, Cd, and significant quantities of Au, Ag, Pb, Se, Cd, Bi, Sn as well as minor amounts of other metals.
Bi, Sn as well as minor amounts of other metals.
n
n VMS occur in lensVMS occur in lens--like or tabular bodies like or tabular bodies
parallel to the volcanic stratigraphy or bedding.
parallel to the volcanic stratigraphy or bedding.
n
n the predominant hosts are volcanic rocks and the predominant hosts are volcanic rocks and fine
fine--grained, claygrained, clay--rich sediments.rich sediments.
n
n Iron sulfide (pyrite, pyrrhotite) with Iron sulfide (pyrite, pyrrhotite) with
chalcopyrite, sphalerite, and galena are the chalcopyrite, sphalerite, and galena are the principal economic minerals.
principal economic minerals.
Mineral and Metal Zoning Mineral and Metal Zoning
n
n Cu is usually high relative to Zn + Pb in the core Cu is usually high relative to Zn + Pb in the core of the pipe and in the spine of the massive
of the pipe and in the spine of the massive
sulfides. The ratio of Zn + Pb to Cu increases sulfides. The ratio of Zn + Pb to Cu increases around the outside of the pipe and towards the around the outside of the pipe and towards the upper part and margins of the massive zone. Au upper part and margins of the massive zone. Au and Ag usually are highest in the fringe areas.
and Ag usually are highest in the fringe areas.
Barite also tends to occur at fringes.
Barite also tends to occur at fringes.
Pyrite, sphalerite, galena
2
2. Vein Deposits . Vein Deposits
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n Convergent margins are good regions to develop Convergent margins are good regions to develop vein deposits. Igneous intrusions and
vein deposits. Igneous intrusions and
metamorphism provide fluids which can metamorphism provide fluids which can penetrate into the overlying deformed
penetrate into the overlying deformed sedimentary rocks.
sedimentary rocks.
n
n As hot (hydrothermal) fluids rise towards the As hot (hydrothermal) fluids rise towards the surface from cooling intrusive rocks through surface from cooling intrusive rocks through
fractures, faults, brecciated rocks, porous layers fractures, faults, brecciated rocks, porous layers and other channels they cool or react chemically and other channels they cool or react chemically with the country rock.
with the country rock.
Conjugate vein sets,
Golden Mile, Australia
3
3. Porphyry Copper Deposits . Porphyry Copper Deposits
n
n Definition: Definition: large, relatively low grade, intrusionlarge, relatively low grade, intrusion-- related deposits. in granitic intrusive rocks that related deposits. in granitic intrusive rocks that are porphyritic in texture.
are porphyritic in texture.
n
n The major products are Cu and Mo or Cu and The major products are Cu and Mo or Cu and Au.
Au.
n
n The country rock alteration is distinctive and The country rock alteration is distinctive and changes as you approach mineralization.
changes as you approach mineralization.
n
n Where sulfide mineralization occurs, surface Where sulfide mineralization occurs, surface weathering often produces rusty
weathering often produces rusty--stained stained bleached zones (Gossan).
bleached zones (Gossan).
Simple porphyry Simple porphyry system
system
Alteration Associated with Porphyry Alteration Associated with Porphyry
Deposits Deposits
n
n The alteration assemblages form distinct zones The alteration assemblages form distinct zones around the intrusion, with a shell of
around the intrusion, with a shell of potassicpotassic alteration grading outward through a shell of alteration grading outward through a shell of cream or green quartz and sericite (
cream or green quartz and sericite (phyllicphyllic), ), white, chalky clay (
white, chalky clay (argillicargillic) and then greenish ) and then greenish chlorite, epidote, sodic plagioclase and
chlorite, epidote, sodic plagioclase and carbonate (
carbonate (propyliticpropylitic) alteration zones into ) alteration zones into unaltered country rock.
unaltered country rock.
From inner to outer From inner to outer (may be incomplete) (may be incomplete)
n
nSilicic core Silicic core
n
nPotassic zonePotassic zone
n
nPhyllic zonePhyllic zone
n
nAgrillic zoneAgrillic zone
n
nPropyllitic zonePropyllitic zone
Ore Zoning Ore Zoning
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n Central barren coreCentral barren core..
n
n Mineralization here tends to be disseminatedMineralization here tends to be disseminated
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n Main ore shellMain ore shell
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n Increase pyrite moving outward to an ore Increase pyrite moving outward to an ore peripheral pyrite shell
peripheral pyrite shell
n
n Veinlet mineralization more importantVeinlet mineralization more important
n
n Shells show a special relationship to the Shells show a special relationship to the alteration
alteration
n
n Highest CuHighest Cu--values often near the phyllic values often near the phyllic ––
potassic boundary potassic boundary
What to look for in the field What to look for in the field
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n Dykes and granitic rocks with porphyritic Dykes and granitic rocks with porphyritic textures.
textures.
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n Breccia zones with angular or locally rounded Breccia zones with angular or locally rounded fragments; look for sulfides between fragments fragments; look for sulfides between fragments or in fragments.
or in fragments.
n
n Epidote and chlorite alteration. Epidote and chlorite alteration.
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n Quartz and sericite alteration. Quartz and sericite alteration.
n
n Secondary biotite alteration. Secondary biotite alteration.
n
n Largest manLargest man--made excavation made excavation (Bingham, USA)
(Bingham, USA)
n
n 22..5 5 miles wide and miles wide and 00..5 5 miles deepmiles deep
