AMGAMGMineralogical Society

Applied MineralogistThe

Web: www.minersoc.org/amg.htmlTwitter: www.twitter.com/amg_minEmail: amgminsoc@gmail.com

The Bulletin of the pplied ineralogy roupA M G

March 2020Volume 5Number 1

From the AMG committeeHello and welcome to the March edition of Applied

Mineralogist! We present a special feature on brand new

research on and how it helps us apatite in volcanic rocks

to understand and crustal magma evolution porphyry

deposits formation. Read about the first meetings this

year and . Finally, test your mineralogical : MDSG VMSG

vocabulary on the . mineralogy crossword

Ÿ Summary of VMSG by Kevin Wong (p. 2)

In this issue:

Ÿ Summary of MDSG 2020 by Holly Andrews (p. 1)

Ÿ The record of crustal magma evolution deciphered by apatite

in volcanic rocks by Chetan Nathwani (p. 3 - 5)

Ÿ #AppliedMineralogy (p. 4)

Ÿ Announcement of the IAEG meeting (p. 5)

Ÿ Mineralogy Crossword (p. 6)

March 2020, 5(1). Page 1

Charlie Compton-Jones

Adam EskdaleEdited by:Stefan HornHolly Andrews Georgian Manuc

Prize winners

The theme of the conference was “metals for a green future”, with talks divided into the following sessions: Critical Metals, Gold, Porphyry Systems, Ni-Cu-PGE, Base Metal Deposits, Hydrothermal Processes and Methods. In total, there were 29 talks. There were also 3 keynote talks by Prof. John Dilles (Oregon State University), Prof. Sarah Gleeson (GFZ Potsdam; talk sponsored by AMG) and Prof. John Thompson

(PetraScience Consultants Inc).The Mineral Deposits Studies Group (MDSG) had its rd th th

43 annual winter meeting in London from the 6 -8January 2020. It was hosted at the Natural History Museum, organised by Prof. Jamie Wilkinson and the London Centre for Ore Deposits and Exploration (LODE) research group. Dr Richard Sillitoe presented a “Porphyry Copper Deposits from Top to Bottom” workshop on 6�� January prior to the Icebreaker.

The Rio Tinto Best Talk Prize: Chetan Nathwani (PhD candidate, Natural History Museum) for: “The magmatic evolution of the Yarabamba batholith, Southern Peru: protracted magmatism culminating in multi-centred giant porphyry Cu-Mo mineralisation”.Anglo American Best Poster Prize: Emily Brugge (PhD candidate, Natural History Museum) for “Apatite inclusions in Zircon: records of porphyry melt evolution”.MDSG Project Prize: George Stonadge for his master thesis (PhD candidate, University of Leicester). This prize is awarded by a panel of academics to the best undergraduate or master thesis.

Mineral Deposit Studies Group Mee�ng (MDSG), 6��-8�� January, London

Summary report by Holly Andrews, Imperial College London

Photo from mdsg.org.uk

MDSG conference dinner in the Earth Hall, Natural History Museum.

March 2020, 5(1). Page 2

Finally, a big thank you to the organising committee of

Paul Cole, Michelle Harris, and Irene Manzella for

coordinating a successful and productive VMSG

meeting (including an exceptional conference dinner

and party), and all the best to the organising

committee of next year's VMSG, to be held at the

University of Manchester.

Congratulations to the two VMSG student prize

winners, Gregor Weber (University of Geneva) for his

poster on Thermochemical modelling of eruptible

magma chemistry, and Sally Law (University of

Edinburgh) for her talk titled Olivine reveals removal of

mantle lithosphere, coincident with the onset of

rhyolitic volcanism in the Taupo Volcanic Zone, New

Zealand. A special mention also to Hannah Buckland

and James Crosby, runners-up for the poster and talk

prizes respectively.

This year, VMSG was hosted by the University of

Plymouth. Despite a chilly, rainy backdrop, several

hundred delegates from research institutions across

the UK and Europe made the trip to the south of

England to share their recent progress in unravelling

the causes, correlations, and consequences that both

drive and result from worldwide volcanic activity. With

over 50 presentations and 100 posters split across

seven research symposia, this year's VMSG had

something for and from everyone across the

volcanological community. Topics covered included

new advances in volcanic hazards, r isk and

communication, magma storage and transport, and

volcanic monitoring and the forecasting of eruptions.The keynote speakers reflected the diversity of

volcanologists present at this meeting. Kathy Cashman

(University of Bristol) highlighted issues volcanologists

face when developing a conceptual model for volcano

forecasting; Constanza Bonadonna (University of

Geneva) discussed risk modelling on the island of

Vulcano; Johan Lissenberg (Cardiff University)

illustrated his research on understanding magmatic

processes at mid-ocean ridges and lower oceanic

crust; Mike Cassidy (University of Oxford) contrasted

the controls on eruptive and effusive volcanic

eruptions. This year's VMSG award went to David Pyle

(University of Oxford), who additionally presented a

keynote on his research over the course of his career,

titled Living with volcanoes: past, present and future.

Volcanic and Magma�c Studies Group Mee�ng (VMSG), 7��-9�� January 2020, Plymouth

A summary report by Kevin Wong, University of Leeds

VMSG award Winner David Pyle during his talk. photo by Paul Cole from Twitter.

March 2020, 5(1). Page 3

The record of crustal magma evolu�on deciphered by apa�te in volcanic rocks: applica�ons to igneous petrology and in understanding porphyry ore deposit forma�on

, Natural History Museum, LondonChetan Nathwani

Introduc�on

The last decade has seen a surge in the applica�on of

LA-ICP-MS in determining trace element chemistry in

petrogene�c studies and explora�on for mineral

deposits. In par�cular, igneous accessory phases have

a�racted a large amount of interest since these can

capture snapshots of the evolu�on of magmas and can

provide insights into processes determining the

occurrence of valuable ore deposits. The largest

accumula�ons of copper in the Earth's crust, porphyry

copper deposits, are formed in subduc�on zones from

the exsolu�on of metal-charged fluids from large upper

crustal arc magma reservoirs. However, these deposits

are only formed in very par�cular segments in

magma�c arcs, and within narrow �me windows during

arc evolu�on.

Interes�ngly, these metallogenic epochs are marked

by dis�nc�ve changes in the trace element chemistry of

arc magmas towards more hydrous and frac�onated

composi�ons (high Sr/Y, high La/Yb and high Eu) [1].

This is thought to reflect tectonic perturba�ons that

enhance crustal compression, causing magmas to stall

in the lower crust and “stew up” their vola�les.

Typically, in a dry magma in the lower crust, plagioclase

is stable and is the dominant frac�ona�ng mineral

phase. However, if we kick up the pressure and the

water content, the mineral assemblage switches to

being amphibole-dominated (in which Yb and Y are

compa�ble) at the expense of plagioclase (in which Sr

and Eu are compa�ble), which causes these dis�nct

changes in geochemical ra�os [2]. Eventually when

these magmas reach the upper crust, they have

accumulated substan�al quan��es of fluid, metal and

sulfur, so that they can generate a giant porphyry

copper deposit [3]. The chemical fingerprints of this

are u�lised in explora�on, since they can narrow down

magma�c districts and regions that are predisposed to

generate these large porphyry copper systems (i.e.

metallogenically fer�le systems). These chemical

signatures of a long-lived lower crustal magma

evolu�on (Sr/Y, La/Yb and high Eu) have also been

employed as indicators of crustal thickening and to

track arc magma petrogenesis [4]. The common

approach of using whole-rock chemistry as indicators

of this deep-seated magma history holds limita�ons,

since these chemical signatures can be obscured by

later magma�c, or even hydrothermal processes.

Despite its low abundance in rocks, apa�te has an

array of uses in geoscience due to its ability to

incorporate and concentrate a huge number of

elements across the periodic table. It is widely used in

fission track da�ng, radiometric da�ng, trace element

geochemistry and in tracking the vola�le budgets of

melts and fluids. We wanted to test whether apa�te

crystals in igneous rocks may provide a tool to track

and decipher the long-lived lower crustal magma

history from other magma evolu�on processes. Our

study focused on volcanic rocks from the Cenozoic of

Central Chile that cover a window of arc magma�sm

that culminated in the Earth's most economically

valuable porphyry copper mineralisa�on event,

Apa�te: an archive of magma�c evolu�on

Figure 1. Scanning electron microscope image of apa�te crystals in the samples studied. (A) Apa�te microphenocryst containing zircon inclusion. (B) Apa�te inclusions in magne�te (mgt) crystal exsolving ilmenite (ilm). (C) SEM-cathodoluminescene image showing two zoned apa�te microphenocrysts.

Solu�ons Crossword: 1. Troilite, 2. Hoodoo, 3. Vitrinite, 4. Sylvite, 5. Kimberley, 6. Germanium, 7. Brown, 8. Apa�te, 9. Aquamarine, 10. Goblin, 11. Olivine

March 2020, 5(1). Page 4

Deciphering magma�c evolu�on using apa�te trace

element chemistry

valuable porphyry copper mineralisa�on event, forming Los Pelambres, Rio Blancos-Los Bronces and El Teniente. The genesis of these deposits is marked by a dis�nct shi� in magma chemistry towards high Sr/Y, high La/Yb and high Eu composi�ons.

We analysed the trace element chemistry of the

apa�te crystals in our volcanic rocks (Fig. 1) by LA-ICP-

MS. The apa�te trace element data showed a clear

correla�on in Sr/Y and Eu/Eu* (a measure of the

magnitude of the Eu anomaly) both within a single

sample and between samples (Fig. 2A). This indicates

that apa�te is a reliable tracer of the evolu�on of Sr/Y

and the Eu anomaly of the melt. We used Mg in apa�te

as a proxy for melt differen�a�on to track how Sr/Y

and Eu/Eu* change as the melt evolves (Fig. 2B). This

demonstrates that apa�te does not record a trend of

increasing Sr/Y with increasing Mg, and therefore does

not record the development of the high Sr/Y

determined by lower crustal magma evolu�on (where

amphibole frac�onates). This is not unexpected, since

we know that apa�te would not crystallise at the

temperatures and pressures found in the lower crust.

However, when apa�te does crystallise in the shallow

crust, it can inherit the signature of a melt that

previously evolved in the lower crust (high Sr/Y, high

Eu/Eu*). We modelled frac�ona�on of amphibole

from a primi�ve melt and found it produced an

increase in Sr/Y and Eu/Eu* that produced the hidden

or “cryp�c” trend, not seen in the apa�te

composi�ons (Fig. 2). Therefore, apa�te in volcanic

rocks is recording a deep frac�ona�on process that is

rarely exposed. We found that the apa�tes that have

the strongest signal of lower crustal evolu�on, are

derived from rocks that formed in thickened arc crust

and may indicate magma composi�ons predisposed to

form porphyry ore deposits.

Figure 2 Trace element chemistry of apa�te in volcanic rocks. Eu/Eu* vs. Sr/Y. Sr/Y vs. Mg. Dashed line shows apa�te A Bcomposi�ons from a model that frac�onates an amphibole-dominant assemblage from a primi�ve melt composi�on, indica�ng that the high Sr/Y and Eu/Eu* in apa�te can be accounted for by lower crustal magma evolu�on.

#AppliedMineralogy @ J. Leutholdvia EGU GMPV Division

@ J. Leuthold

From your #ThinSectionThursdays, #FieldworkFridays

& #MineralMondays, our #AppliedMineralogy

winner is...

with a beautiful gabbro in transmitted light from the

Rum Layered Intrusion, Scotland.

March 2020, 5(1). Page 5

Nathwani, C. L., Loader, M. A., Wilkinson, J. J., Buret, Y., Sievwright, R. H., Hollings, P. (2020) Mul�-stage arc magma evolu�on recorded by apa�te in volcanic r o c k s . G e o l o g y , 4 8 ( 4 ) . h�ps://doi.org/10.1130/G46998.1

This ar�cle is based on the paper:

References

Our approach demonstrates that apa�te entrained

as crystal cargo in volcanic erup�ons can record

valuable informa�on on the composite evolu�on of

arc magmas in the crust. Since the informa�on

recorded by apa�te indicates protracted lower crustal

magma evolu�on, it can poten�ally indicate the

metallogenic fer�lity of arc magmas.

[1] Richards, J. P., & Kerrich, R. (2007). Special paper: Adakite-like rocks: Their diverse origins and ques�onable role in metallogenesis. Economic Geology. 102(4), 536-576.

Though apa�te can record the signature of lower crustal magma evolu�on, apa�te is co-crystallising with other mineral phases in the shallow crust that can modify the melt chemistry. We found that within single samples, trends in Mg, Sr/Y and Eu/Eu* were clear which always showed decreasing Sr/Y and Eu/Eu* with decreasing Mg (i.e. as the melt evolves, apa�te is slowly recording the melt decreasing in Sr/Y and Eu/Eu*). This is consistent with apa�te crystallising with a phase that is removing the Sr and Eu from the melt – probably plagioclase (Sr and Eu are compa�ble in plagioclase) – which is the dominant phenocryst phase in the rock. Consequently, though apa�te is recording this interes�ng lower crustal frac�ona�on signature, this signal in apa�te is gradually overprinted by later melt evolu�on. We therefore conclude that apa�te can track mul�ple stages of arc magma evolu�on.

Summary and conclusions

[2] Müntener, O., Kelemen, P. B., & Grove, T. L. (2001). The role of H O during crystalliza�on of primi�ve arc magmas 2

under uppermost mantle condi�ons and genesis of igneous pyroxenites: An experimental study. Contribu�ons to Mineralogy and Petrology. 141(6), 643-658.

[4] Profeta, L., Ducea, M. N., Chapman, J. B., Paterson, S. R., Gonzales, S. M. H., Kirsch, M., Petrescu, L., & DeCelles, P. G. (2015). Quan�fying crustal thickness over �me in magma�c arcs. Scien�fic Reports 5, p. 17786.

[3] Chiaradia, M., & Caricchi, L. (2017). Stochas�c modelling of deep magma�c controls on porphyry copper deposit endowment. Scien�fic Reports 7(1), 1-11.

The Irish Associa�on for Economic Geology (IAEG) was founded in 1973 with the primary goal of providing a forum for geoscien�sts working in economic geology in Ireland.

At the turn of each decade the Associa�on organises an interna�onal conference. The 2020 conference will be:

Minerals 2020 Europe’s Past, Present and Future

Venue: Salthill Hotel, Galway, IrelandDate: 14th – 16th May 2020

Website: h�ps://www.iaeg.ie/page-18136; Contact: chairperson@minerals2020.ie

The conference will explore Europe’s past mining tradi�on, document the current ac�vity and look to the future for the sector. The conference will address these through the following technical sessions:

• Se�ng the scene: a series of talks on the current state of the minerals sector in Europe.• Precambrian metallogeny: following a scene se�ng keynote address on Precambrian geology and metallogeny there will

be a series of deposit specific talks.• Caledonian metallogeny: following a scene se�ng keynote address on Caledonian geology and metallogeny there will be a

series of deposit specific talks.• Hercynian metallogeny: following a scene se�ng keynote address on Hercynian geology and metallogeny there will be a

series of deposit specific talks.• Alpine metallogeny: following a scene se�ng keynote address on Alpine geology and metallogeny there will be a series of

deposit specific talks.• The future: a series of talks looking at how the minerals sector is likely to evolve in the next decade and addressing issues

of relevance to the sector.

Interested in joining the Mineralogical Society and Applied Mineralogy Group? Go to: for membership details.http://www.minersoc.org/

Mineralogical Society

Mar ‘20 24 - 26

Calendar

AMGAMG

Founded in 1963 by Norman F.M. Henry, the AMG is a special interest group of the Mineralogical Society of Great Britain and Ireland. We encourage and promote the study and research of mineralogy applied to ores and related industrial mineral materials. This encompasses: ore microscopy, fluid inclusions, nuclear minerals, coals, refractories, slags, ceramics, building materials, nuclear waste disposal, carbon capture and storage, down-hole borehole alteration, and mineral-related health hazards.

About Us

Editorial

Thank you to those who have contributed to this issue of

Applied Mineralogist. Please forward any articles, comments or

notices of events and conferences to . amgminsoc@gmail.com

All previous issues of Applied Mineralogist are available at

www.minersoc.org/amg-applied-mineralogist

Thanks for reading; our next Applied Mineralogist will be

out in June 2020. Keep up on what is happening in the

meantime by following us on twitter .@amg_min

We welcome applications from both individuals or

organisations for funding in support of events covered in the

AMG remit. Further guidelines on how to apply can be found at

www.minersoc.org/amg-funding

The AMG provides bursaries for postgraduate students in

the disciplines of Applied Mineralogy, Crystallography, and

Petrology and Geochemistry. Bursaries are intended to support

conference attendance and associated travel costs, although

other activities may be considered. Application guidelines can

be found at www.minersoc.org/amg-bursaries

Please note there are two bursary application deadlines

each year: 1st March and 1st September. Requests for funding

must be received well in advance of the event to allow for

consideration by the committee.

AMG Postgraduate Bursaries

If you would like to become more involved in the AMG,

elections are held yearly at the AGM. Spaces for Student

Representatives come up regularly. If you would like to be

considered for a committee spot please email Eimear Deady

(Chair).

Funding

Get Involved

Notices

Metamorphic Studies Group RiP Mee�ngSt. Andrews, Scotland

May ‘2014 - 16

Jun ‘203 - 5

Geochemistry Group 50th Ann. Symp. & GGRiPOxford, England

Jun ‘2021 - 26

Sep ‘20 6 - 10

European Mineralogical Conference (EMC)Krakow, Poland

Oct ‘20 23

Diffusion in Minerals, Rocks and Melts:Pi�alls and poten�alLondon, England

1

2

3 4

5

76

8

9

10

11

11. Mineral found in Mediterranean food

3. Maceral, which got its name from glass

9. Poseidon's favourite gemstone

1. Variety of pyrrho�te and isotope standard

10. Early German miners named cobalt a�er this fantas�c creature

6. Cri�cal metal used in solar panels

5. City of the “Big Hole” in South Africa

2. Magical rock forma�on in deserts

4. It comes last in the evapora�on sequence

7. Streak colour of chromite

8. A hungry Phosphate

Mineralogy Crossword

Solu�ons are at the bo�om of Page 3

Goldschmidt ConferenceHonolulu, Hawaii

Minerals 2020 (IAEG)Galway, Ireland