Energy Critical Elements in the English Lake District ... · Beryllium Germanium Natural graphite...
Transcript of Energy Critical Elements in the English Lake District ... · Beryllium Germanium Natural graphite...
Energy Critical Elements in the English Lake District -
Scar Crags, Dale Head North
Giulio Solferino & Nathan Westwood
3rd International Critical Metals Conference – Edinburgh, April 29 – May 03, 2019
Contents
‐ Introduction
‐ Scar Crags and Dale Head North
‐ Geology
‐ Minerals & Paragenesis
‐ A story of magma and sediments
‐ Oddities
Introduction
Taken directly from the European Commissions most recent (2017) critical materials review.
27 different raw materials are now considered to be ‘critical’ according to the Commission which has increase by 9 from the last review (2014)
2017 Critical Raw MaterialsAntimony Fluorspar LREEs Phosphorus
Baryte Gallium Magnesium Scandium
Beryllium Germanium Natural graphite Silicon metal
Bismuth Hafnium Natural rubber Tantalum
Borate Helium Niobium Tungsten
Cobalt HREEs PGMs Vanadium
Coking coal Indium Phosphate rock
Introduction
Olivetti, E. A., Ceder, G., Gaustad, G. G., Fu, X., Joule (2017), 1, 229.
Introduction
• The UK relies almost entirely on EU and other international
sources for its Co supply. Yet, there might be viable sources
within the British Isles.
• Noticeably, in the Lake District several Co‐bearing
mineralisations were flagged (back in the seventies and
eighties)
https://www.euchems.eu/wp‐content/uploads/2019/01/The‐Periodic‐Table‐and‐us‐Handley‐European‐Commission.pdf
IntroductionWhy?Lake District is host to a vast network of high quality mineral deposits which have not been studied for a number of years. Also, easily accessible.
Many of the mineral deposits are unique and have very unusual geochemistry
W (wolframite and scheelite at Carrock Fell Mine), Sb (Stibnite and berthierite at the Robin Hood and Wet Swine Gill veins) and pure graphite (C, in the form of nodules within metamorphosed veins at Seathwaite/Borrowdale).
Introduction
Scar Crags and Dale Head North
Where? Northern ‘English Lake District’
Scar Crags and Dale Head NorthSkiddaw Group Formations Early‐mid Ordovician
mostly epiclastic sedimentary rocks
Borrowdale and Eycott volcanics Mid‐late Ordovicianmostly volcanics (lava, tuff, ignimbrite)
Largely concealed batholith Late‐Ordovician to Mid‐Devonian
Map inspired by: Earthwise.bgs.ac.uk, 2017
Causey Pike Fault
GeologyScar Crags:Hosted by Kirkstile Fm. (Skiddaw group)
Siltstone and mudstone
‘Bleached’ shalesMetasomatic aureole of intrusive synchronous to the Shap Granite.
Causey Pike Fault
Dale Head North:Hosted by Buttermere Fm. (Skiddaw Group)Siltstone, mudstones, and sandstones.
Fluids that forms veins must cross through all surrounding/underlying rocks
At DHN some of those rocks are tuffs and ignimbrites (BVG)
Geology
Minerals & Paragenesis
New findings:
Sulpharsenides are solid‐solutions of Co‐Fe‐Ni
There are REE minerals
Gold
Bismuth in large amounts
So, what critical elements?
As, Bi, Co, REE, Sb, Se*, Te*
*There are some unidentified Bi‐Te and Bi‐Se
Minerals & Paragenesis
1 mm
0.5 mm
Microphotograph: RL, PPL
Microphotograph: RL, XPL
Cob
Apy
All
All
All
Gla
Aln
Aln
Qz
Chl
Cpy
Sph
Minerals & Paragenesis
Minerals & Paragenesis Sulpharsenides – S‐bearing
Silicates, etc. – S‐free
A story of magma and sedimentsPieces of the jigsaw puzzle:
Similarities of minerals (sulpharsenides, chlorite, quartz, bismuth)
Underlying batholith/intrusives
Exaggerated geothermal gradient (Caledonian Orogeny + intrusion of ‘Lake’ batholith) strong convection of meteoric and/or connate waters
Mineralisation emplaced as fault plane infill (both)
Diverse structural settings: SC – Causey Pike Fault vs DHN – no thrust fault
Metasomatic aureole at SC [NOTE: No disseminated sulphides S‐free magmatic fluids?]
First stage ‘early’ precipitation of silicates, oxides, and phosphates at DHN [S‐free (magmatic) fluids?]
Diverse host (and underlying) rocks: SC – epiclastic siltstone vs DHN – volcaniclastic, tuffs
A story of magma and sediments THE STORY THEN:
Early stage:
Scar Crags: Thrust fault controls emplacement of intrusion (raised dome and/or stock‐like ridge) and it fluxes lots of S‐free magmatic fluids into the relatively porous siltstones (metasomatic aureole)
Dale Head North: A near‐vertical fault plane acts as preferential pathway for magmatic fluids resurgence, leading to vein‐type mineralisation (S‐free, silicates, oxides, phosphates)
Late stage:
Scar Crags: A near‐vertical fault develops and become the preferential trap for magmatic fluids resurgence (focussing of flow) and ‘catchment’ of circulating connate/meteoric waters (these contains metals and sulphur scavenged by surrounding rocks) = MIXED FLUID ORE
Dale Head North: The near‐vertical fault remains the preferential trap for magmatic fluids resurgence (focussing of flow) but by now it also act as ‘catchment’ of circulating waters = MIXED FLUID ORE
A story of magma and sediments: Early STAGE (t1)
Magmatic fluid mineralisation (S‐free) Magmatic fluid metasomatism (S‐free)
A story of magma and sediments: Late STAGE (t2)
Mixed fluids mineralisation: Magmatic + Meteoric/Connate During late stage the convection of meteoric/formation water is much more developed
Oddities: 1. Probably Ce‐Bastnaesite
50 μm EDS spectrum
BSE image
20 μm
100 μm
EDS spectrum
BSE images
Oddities: 2. Probably Xenotime
Thank you for your attentionQuestions?
My typical style is to finish with a ‘thing of beauty’ – This time: The Ferrari Monza SP2
FUTURE PROGRESSES (limited by funds availability):
‐ Thin sections of host rock (petrography, effects of ‘bleaching’)
‐ Whole rock X‐ray fluorescence: Non‐bleached vs. bleached siltstone
‐ O, H stable isotopes on quartz (possibly also chlorite)
‐ S stable isotopes on sulpharsenides
‐ Fluid inclusion study (quartz)
‐ LA‐ICP‐MS on fluid inclusions
Sb elemental map – up to 5 wt%
Alloclasite with a cobaltite inclusion