Magmatic depositssulfides Ni and Cr PGE

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Magmatic depositssulfides (Ni and Cr) PGE
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Alkali feldspars at low pressures two
complete solid solutions with a solvus
Immiscibility field
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???? ??? ???() ??? Native Copper Cu 100 ???
Chalcopyrite CuFeS2 34.5 ??? Bornite Cu5FeS4
63.3 ??? Chalcocite Cu2S 79.8 ? ? Covellite CuS
66.4 ???? Enargite Cu3AsS4 48.3 ????
Tetrahedrite (Cu,Fe)12As4S13 57.0 ??? Tennantite
(Cu,Fe)12Sb4S13 52.1 ??? Cuprite Cu2O 88.8 ???
Tenorite CuO 79.8 ??? Malachite CuCO3.Cu(OH)2
57.3 ??? Azurite2 CuCO3.Cu(OH)2 55.1 ???
Chalcocyanite CuSO4 ?? Chalcanthite
CuSO4.5H2O ???? Cuprocopiapite CuFe43(SO4)6(OH)2.
20H2O ???? Chrysocolla CuSiO3.2H2O 36.0
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??? ??? ??? ??? (Millerite) NiS ????
(Pentlandite) (Fe,Ni)9S8 ( Co ?1-3), Pt,
Pd ????? (Violarite) FeS.Ni2S3 ???? (Nickeline)
NiAs ???? (Gersdorffite) NiAsS ????
(Breithauptite) NiSb ????? (Garnierite)
Ni(Si4O10)(OH)4.4H2O (NiOlt46) ???? (Nimite)
(Ni,Mg)6(Si4O10)(OH)8 ????? (Ni-Nontronite)
(NiO1-2) ?? (Anrabergite) Ni3(AsO4).8H2O (NiO37)
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Characteristics of PGE in magmatic processes
????(platinum group elements,??PGE)???(Ru)??(Rh)?
?(Pd)??(Os)??(Ir)??(Pt)?????????????????? (??1112
),????????????(??21.422)????? ???????????????????
????,??????? ?????,???????? ?????????,???????????
,??????,??? ????????????????????Os?Ru?Ir?????? ???
????????????????????????????? ???,????????????????
????????????,?????????Pt 2.0g/t,Pd 1.3g/t, Os
1.0g/t,Ir 0.7g/t,Rh 0.5g/t,Ru 1.3g/t?????,????????
??????????????????????,???????? ?????????????,???
????????????? ???????????
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Sudbury, Ontario
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• SUDBURY MINING CAMP
• To date, the Sudbury mining camp has produced
• in excess of 16 billion pounds of nickel,
• 15 billion pounds of copper,
• 85 million ounces of silver,
• 17 million ounces of platinum, and 3 million
  ounces of gold and remains, to this day, Canadas
  principal producer of platinum.
• Currently, there are 35 producing mines in the
  Sudbury Camp.

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• GEOLOGY OF THE SUDBURY REGION
• The Sudbury region is dominated by a large 60 km
  long by 30 km wide elliptical depression known as
  the Sudbury Structure which lies at the junction
  of three unique geological-structural provinces
  the granitic gneissic basement rocks of the
  Archean Superior Province to the north, the
  supracrustal metasediments and metavolcanics of
  the Early-Proterozoic Southern Province to the
  south, and the Middle-Proterozoic Grenville Front
  Tectonic Zone.

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• GEOLOGY OF THE SUDBURY STRUCTURE
• The Sudbury Structure constitutes the largest
  known concentrations of nickel-copper-PGE bearing
  sulfide minerals in the world. Due to its
  economic importance, the structure is one of the
  most intensively studied and documented regions
  of the Canadian Shield.
• Stratigraphically, from top to bottom, the
  Sudbury Structure consists of the Whitewater
  Group of sediments, the underlying Sudbury
  Igneous Complex (SIC), and brecciated footwall
  rocks surrounding the SIC.

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• The Whitewater Group
• Infilling the central depression of the Sudbury
  Structure are the Whitewater Group sediments that
  consist of, from top to bottom
• the Chelmsford Formation greywacke,
• the Onwatin Formation manganese-rich slate,
• and the Onaping Formation volcaniclastic/breccia
  sequence.

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• The Sudbury Igneous Complex
• Underlying the Whitewater Group is the
  Sudbury Igneous Complex (SIC). The SIC consists
  of a lower zone of augite-bearing norite a thin
  middle layer (Transition Zone) consisting of
  norite grading upwards into quartz gabbro and an
  upper zone of micropegmatite/granophyre. At the
  base of the lower zone is a discontinuous zone of
  inclusion and sulfide-rich norite-gabbro commonly
  known as the Contact Sublayer (Sublayer). The
  Sublayer occurs as gently dipping sheets or
  irregular lenses along the base of the SIC or as
  small bodies in radial depressions or troughs in
  the base of the SIC called embayments, and as
  steeply dipping dikes called offsets which
  intrude into the adjacent footwall. The Sublayer
  is typically gabbroic in the base of the SIC and
  in the embayments, and typically quartz-diorite
  in the offset dikes. All Ni-Cu-PGE deposits of
  the Sudbury Structure are contained within the
  Sublayer and related structures such as the
  offset dikes.

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• There are two types of offset dikes
• 1. radial, which appear to stem directly from the
  Sublayer
• and intrude into the footwall rocks radially
  away from the SIC.
• 2. concentric dikes, which are thought to be
  related to ring
• faults and may be connected to the Sublayer at
  depth or
• represent accumulations of melt rock associated
  with
• pseudo-tachylyte formation.

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• Origin of the Sudbury Structure
• Existing evidence for the origin of the Sudbury
  Structure supports a meteorite impact. This
  includes the irregular and dike-like bodies of
  pseudo-tachylyte breccias (Sudbury and Footwall
  breccias) up to 70 km from the margins of the
  structure shatter cones in rocks marginal to the
  structure the 1.8 km-thick volcaniclastics/brecci
  as of the Onaping formation (interpreted as
  fallback breccia) and shock deformation lamellae
  in quartz and feldspar in country rock inclusions
  within the Onaping formation. The following
  summarizes the evolution of the Sudbury area.

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• MINERALIZATION AND DEPOSIT TYPES OF THE SUDBURY
  STRUCTURE
• Sudbury ores are typically zoned. Fractional
  crystallization of a monosulfide solid solution
  from a sulfide melt is believed to have given
  rise to a cumulate phase rich in Fe, Co, Rh, Ru,
  Ir and Os (pyrrhotite-rich ores) and a
  fractionated liquid rich in Ni, Cu, Pt, Pd, and
  Au (chalcopyrite and PGE-rich ores). In some
  cases, the liquid phase is then believed to have
  migrated out from the Sublayer and further
  fractionated to form Cu and PGE rich footwall
  ores.
• Common Ni and Cu-ore minerals consist of
  pyrrhotite, pentlandite, chalcopyrite with minor
  pyrite, and cubanite (CuFe2S3).
• Sudbury Ni-Cu-PGE sulfide mineralization occurs
  in three deposit settings

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• Contact deposits or embayment deposits
• Located along the lower contact of the SIC in
  association with the norite-gabbro
  inclusion-bearing Sublayer. The Sublayer may be
  up to 100 metres thick. The greatest thicknesses
  are found in kilometer-size radial embayments
  within which are smaller, secondary troughs or
  terraces. The highest sulfide concentrations in
  the Sublayer are found within these embayments
  where sulfide distribution is further controlled
  by the terraces. Large concentrations of sulfides
  and nickel are often found in footwall deposits
  immediately adjacent to the terraces. Cu/Ni
  ratios are typically lowest in the Sublayer and
  increase towards the Footwall Breccia.
• The Sublayer constitutes a well defined
  exploration target and has been a prolific
  producer over the years. Consequently contact
  deposits comprise 21 of the 35 mines in the
  Sudbury area. Contact deposits at the base of the
  SIC are still currently being mined by both
  Falconbridge and Inco at the Falconbridge, Garson
  and Levack mines.

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• Footwall deposits
• Zones of sulfide mineralization in the form of
  stringers, veins, massive sheets and/or
  disseminated sulfide which appear to have
  migrated outwards from the Sublayer and/or
  Footwall Breccia and penetrated deeply into the
  footwall rocks. The Frood-Stobie Mine, which is
  estimated to have originally contained a geologic
  resource of 450 to 500 million tonnes, is the
  largest and best example of a footwall deposit.
  This mine lies at the east end of the South Range
  Breccia Belt and is situated almost 2 km into the
  footwall.
• Offset Dike deposits
• Associated with radial and concentric
  quartz-diorite dikes that extend from the
  Sublayer into the footwall rocks. Mineralization
  typically occurs as disseminated to massive
  sulfides within the dikes. The massive sulfide
  bodies are often rimmed by a halo of disseminated
  material that is often found along the contacts
  of the dike. Examples of offset deposits include
  Nickel Offsets along the Foy Offset dike, and the
  Copper Cliff North and South mines and the Totten
  Mine along the Copper Cliff Offset and
  Worthington Offset dikes, respectively.

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Great Dyke 330 mile long, 4 mile wide, consists
of layers of ultrabasic rocks now largely
altered to serpentine. The dyke deposits are
bands of chromite about 8 inches
thick. Stillwater, Montana an E-W belt about 50
km long and 1 km wide. Muskox, NW Territories a
Pre-Cambrian layered ultramafic complex.