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FORMATION OF SEDIMENTARY ROCK-HOSTED STRATIFORM COPPER DEPOS

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on 1 April 2015

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Transcript of FORMATION OF SEDIMENTARY ROCK-HOSTED STRATIFORM COPPER DEPOS

FORMATION OF SEDIMENTARY ROCK-HOSTED STRATIFORM COPPER DEPOSITS THROUGH EARTH HISTORY
From Hitzman et al., 2010
Núria Pujol Solà
Advanced Ore Deposits II
University of Geneva
18/03/2015

Introduction
Sediment-hosted stratiform copper deposits (SSC)
or
Sedimentary rock-hosted stratiform copper deposits

*Relatively thin (3m) sulfide-bearing zones preconcordant with lithologic layering*
Mineralized zone: sheetlike - tabular - roll-front

Important for worldwide production of:
- 20-25% Cu
- 80% Co
- Pb, Zn, Ag, U,
Au, PGE , Re
Geodynamic setting and age distribution
Adapted from Hitzman et al., 2010
Basin architecture
Host-rock and mineralization ages
Critical factors for deposit formation
REFERENCES
Sedimentary intracratonic basins
Initial stages of rift
Contact between:
- basal red-beds
- marine sediments (presence of evaporites)
Temporal distribution nonrandom
After atmosphere oxygenation (Early Paleoproterozoic)
From Paleoproterozoic to Tertiary
Supergiants
>24Mt Cu
Giants
>2Mt Cu
Adapted from Hitzman et al., 2010
Distinct spikes of deposits formation
Katangan basin
Zechstein basin
Kodaro - Udokan basin
Pangea break-up
Rodinia break-up
Nena break-up (?)
Deposits formation
Process involving:
- source of metals
- source of sulfur
- metal-transporting
fluid
- transport paths
- mobile reductants
- thermal or
hydraullic pump
- trapping factors


Adapted from Robb, 2005
Hitzman, M.W., Selley D. and Bull S. (2010): Formation of sedimentary rock-hosted stratiform copper deposits through Earth history. Economic Geology, 105, 627-639.

Robb, L. (2005): Introduction to ore forming processes. Blackwell Publishing. Oxford. 374pp
THANK YOU FOR
YOUR ATTENTION
Features for supergiant deposits:
- large fluid accumulations
- fluid convection
- focused precipitation
- hydrologically closed basin
- long mineralization period (hundreds of million years)
Basal synrift red-beds with volcanic rocks
- oxidized fluids source
- metals source
Marine/lacustrine sediments postrift
- contained reductant: in situ organic matter or migrated HC
Evaporite layers
- seal
- generation of dense residual brines

Mineralization best developed in basin margins (pinch-out) where there is fluid overpressure.
From Hitzman et al., 2010
Sulfides postdate sedimentation
Mineralization can occur:
- from early diagenesis
- to basin inversion and metamorphism
Complex multistage of precipitation
- oxidized metal source bed
- reduced facies -> metal traps
- saline brines: leach metals and transport
Fluids released in focused zones
Passive margin -> fluid migration -> no deposit formation
Aborted rift -> closed hydrologic system -> deposit formation
Contain of high-salinity basinal fluids for long times
Adapted from Hitzman et al., 2010
- Deposits formed in sedimentary rocks located 20-30º from the paleoequator and in relatively quiescent basins


Tectonic configuration during late Permian.

Incipient rifting ->
several intracratonic basins

Mineralization period >100my
Formation of supergiant deposits
Exploration considerations
Giant deposits do not correlate with maximum evaporite deposition
During Neoproterozoic and Permian:
- continent break-up
- major glacial events (even in low latitudes during Neoproterozoic)

Gacial events consequences:
Glacial event -> melting -> increased sedimentation rates -> increased compactation -> accelerated salt tectonics -> fluid convection
Mg increased in seawater (low sea level) -> increase in sulphate
Sulfate-rich seawater-> increased sulfur that can be fixed (in Cu sulfides)

Seawater composition may be important for supergiant deposits formation
From Hitzman et al., 2010
From Hitzman et al., 2010
Target periods with suitable plate tectonic configuration
Perform geologic studies to confirm the appropriate sedimentary structure

Supergiant deposits could be found in Permian or Neoproterozoic basins

Better understanding of paleoplates configuration -> critical for future exploration

Only a few sediment-hosted stratiform copper districts -> specific and unique conditions needed -> rare throughout Earth history
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