Mineral Systems in Mineral Potential Evaluation
Ferenc Molnár
STAKEHOLDER SEMINAR, 06 MAY 2015, ROVANIEMI www.gtk.fi
Subjects of Presentation
•Mineral system approach, mineral system models •The MINSYSPRO project and consortium •Orogenic gold mineral systems - methods of research - examples for determination of critical processes and parameters; Hattu Schist belt, Peräpohja Belt, Central Lapland Greenstone Belt •Links to mineral prospectivity mapping
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Gold
Mineral Systems, Models and Mineral Potential Evaluation
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Mineral Systems - all geological factors that control origin and preservation of mineral deposits Mineral System Model - definition of sources transportation accumulation re-mobilisation mappable parameters Mineral potential evaluation -incorporation of mappable parameters of mineral system models into mineral prospectivity evaluations
approach
modeling
prospecting
ore components
Geodynamic processes – Source rocks
Structures
Vectors to ore
Primary and secondary dispersion
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Mineral Systems: Critical Processes and Parameters
Accumulation processes
Critical processes
Critical parameters
Geological features
Mappable
criteria
Change in physical state of fluids
Change in chemical state of fluids
Characteristics of fluid/rock interaction
Primary Transportation Deposition Preservation/Re-mobilization mobilization
Alteration mineralogy Rocks with favourable chemistry Chemical gradients
in composition of rocks
Geophysical response Lithogeochemistry Remote sensing response
Processes in Mineral Systems and Mappable Criteria
Modified after McCuaig et al., 2010 Link between mineral system research 3D modeling and mineral prospectivity mapping
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Mineral Systems and Mineral Prospectivity in Finnish Lapland
MINSYSPRO
Academy of Finland supported project on primary mineral resources Consortium: Geological Survey of Finland University of Oulu Experts from foreign universities UK, Sweden, France, Norway From 09.2014, four years
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What was the idea behind the project?
-Mineral system approach
-Critical processes and footprints (vectoring) in orogenic gold and magmatic mineral systems
-Conversion of critical processes into mappable criterias
-Incorporation of parameters of critical processes and mappable criterias into 2D-3D geological models
-Forward modeling
-Transferring of the new knowledge and mappable criterias to conceptual and empirical mineral prospectivity mapping
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New targets for mineral exploratiom
Workflow of the Project
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Research on Orogenic Gold Mineral Systems:
Outstanding Questions - Examples
Sources of ore forming fluids and components -magmatic, metamorphic, other? Footprints of gold enrichments - which parameters are applicable for vectoring towards ore? Multiple mineralization events - different stages in one system or superimposition of independent systems? Effect of superimposing events on composition and quality of ore - dispersion or concentration?
Hattu Schist Belt
Central Lapland Greenstone Belt
Kuusamo Belt Peräpohja Belt
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ORE
10-100s km
100s µm
OVERPRINT
REMOBILIZATION
Studies of minerals at the micro scale can be used to decipher processes at the km+ scale
BSE image, sulfides (bright) in primary silicates (med grey) with alteration (dk gray)
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Repetition of processes at all scales
Nu AttoM HR-ICP-MS with laser microprobe
Nu Plasma MC-ICP-MS with laser microprobe
JEOL JSM 7100F high resolution
FE-SEM
Mineralogy Geochronology, stable and radiogenic isotopes, trace elements
Linkam MDSG 600 microT
Fluid inclusions
Cutting Edge Analytical Tools Applied in Mineral System Research at GTK
In situ high analyses with high spatial resolution Simple sample preparation – mostly polished thin sections Multiple isotope/trace element/fluid inclusion analyses from the same sample and even from the same mineral grain.
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Tourmaline veining in intrusive rocks
Massive tourmalinization in metasedimentary units
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Magmatic Metasedimentary
Source of Fluids Boron Isotopes in Tourmaline , Hattu Schist Belt, Eastern Finland
Source of Fluids: Potential Use of Unconventional Stable Isotopes
Hattu Schist Belt, Eastern Finland
Copper and sulphur isotope analyses in chalcopyrite by LA MC ICPMS
Magmatic fluids
Fluids from the metasediments
Further research on -Proterozoic orogenic gold systems - Fe, Zn and Mo isotopes
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Tonalite weak alteration
Feldspar porphyry Strong alteration and
disseminated ore
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Fluid Sources – Mappable Criterias
ORE No
ORE
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Mappable criteria? - Geophysical response?
2712±4 –2717±8 Ma 2725 ± 12 Ma
Zircon 207Pb-206Pb ages :
Zircon 207Pb-206Pb age
Mappable Criterias – Geophysical Response Petrophysical Properties of Mineralized Source Rocks and Barren Intrusions
Pampalo Mine, Hattu schist Belt
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Effect of Remobilisation on the Quality of Ore Pampalo Mine, Hattu schist belt
Ar-Ar thermochronology
Lead isotopes: galena, hydrothermal K-feldspar Late Svecofennian (1.81 Ga) K-metasomatism
Late Svecofennian (1.81 Ga) thermal event
K-feldspar deposition
High grade ore in K-feldspar-bearing alteration zones
Mappable K-anomalies
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Molar element ratios in the host rocks compared tomolar element ratios of alteration mineralsss
Trap 1: uraninite grains
Uranogenic lead in Pb-minerals
Traps for Formation of High Grade Gold Concentration Rompas, Peräpohja Schist Belt
(U,Pb*)O2 UO2 + Pb*2+
2Au(HS)2ˉ + H2 + Pb*2+ 2Au + Pb*S + 3H2S
2Au(HS)2
ˉ+ 2H2 + Pb*2+ Au2Pb* + 4H2S
[Au2Te4]4- + 2H2 + 4Pb*2+ 2Au + 4Pb*Te + 4H+
Trap 2: pyrobitumen nodules
Scavenging of sulphur from gold transporting fluids
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Gold
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Geochronology of multiple hydrothermal events: Kuotko, Central Lapland Greenstone Belt
Early arsenopyrite bearing mineralization superimposed by native bismuth-gold-pyrrhotite
in veins with multiple carbonate deposition
1739 Ma
1808 Ma
1814 Ma
1822 Ma
1778 Ma
Hydrothermal xenotime from carbonate veins: U-Pb geochronology by LA MC ICPMS
Aspy
Bi
Au
Po
Intercept at 1854 ± 14 Ma MSWD = 0.28
Probablity of fit 0.96
Intercept at 1769 ± 9 Ma MSWD = 0.49
Probablity of fit 0.97
Critical processes of ore formation and preser-vation manifested by mappable geological and geophysical features
Mineral system research
Spatial and temporal dis-tribution of geological features that record critical processes
2D-3D-4D modelling Conceptual and empirical
evaluation of mineral potential and selection of areas for exploration
Mineral prospectivity mapping
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Summary
Research on critical processes and key parameters Models and mineral prospectivity of orogenic gold mineral systems; workgroup 1 mapping, workgroup 3 Ferenc Molnár Vesa Nykänen Hugh O`Brien Satu Mertanen Peter Sorjonen-Ward Tero Niiranen Sayeb Muhammad Eeva-Lisa Laine Antonin Richard (France) Ilkka Lahti Ian Pitcairn (Sweden) Jouni Lerssi Harry Oduro (U.K.) Ilkka Suppala Holly Stein (USA/Norway) Postdoctoral researcher Postdoctoral researcher from 01.01.2015 from 01.09.2016 to 30.08.2018 Alexander Middleton T.B.N.
Research teams: orogenic gold mineral systems and mineral prospectivity mapping
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Research teams: magmatic mineral systems
Univeristy of Oulu: GTK: Eero Hanski Hannu Huhma Shenghong Yang Yann Lahaye Markku Pirttijärvi Tuomo Karinen Wolfgang Maier, (U.K.) Jukka Konnunaho Tuomo Törmanen Two Master’s students (2x3 months) Doctoral student First Quantum Oy.: from 01.09.2014 to 30.08.2018 Petri Peltonen Marko Moilanen
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Kuotko area
Levijärvi- Luokinen
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Suurikusikko – Europe`s largest gold producer, Kistala shear zone, typical orogenic gold deposit Kuotko area – typical orogenic gold with some atypical features, higher metamorphic grade at the northern termination of the Kistala shear zone Levijärvi-Luokinen – orogenic gold deposits with atypical metal associations at the conjunction of the Kistala and Sirkka shear zones Saattopora – orogenic gold deposit with some atypical features along the Sirkka shear zone
Orogenic gold targets in the Central Lapland Greenstone Belt
Suurikusikko
Saattopora
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