Evolution of continental crust in the Proterozoic : growth and reworking in orogenic systems
(2015) In Litholund theses- Abstract
- To understand the growth of continental crust, the
balance between juvenile mantle derived extraction,
infracrustal reworking and crustal recycling, needs to be
estimated. Since the beginning of the century, the use of
coupled in situ zircon U–Pb, Lu–Hf and O isotope analyses
as a tool to address these questions have increased
exponentially. Numerous compilations of ever growing
datasets have been presented, leading to new, and sometimes
contrasting models of continental growth. Many
of theses models, however, suffer from a number of
assumptions, including a mantle reservoir that has been
homogeneously and linearly depleted since the... (More) - To understand the growth of continental crust, the
balance between juvenile mantle derived extraction,
infracrustal reworking and crustal recycling, needs to be
estimated. Since the beginning of the century, the use of
coupled in situ zircon U–Pb, Lu–Hf and O isotope analyses
as a tool to address these questions have increased
exponentially. Numerous compilations of ever growing
datasets have been presented, leading to new, and sometimes
contrasting models of continental growth. Many
of theses models, however, suffer from a number of
assumptions, including a mantle reservoir that has been
homogeneously and linearly depleted since the Hadean.
Further, the use of (mainly) detrital zircon, taken out
of their geological context, and the application of their
depleted model-ages clearly hamper the validity of these
models.
To accurately address the question regarding continental
crustal growth using combined zircon U–Pb-Lu–Hf(-O)
isotope data, one needs to have contextual control and
minimise the uncertainties of the applied models.
In papers included in this thesis such an approach has
been used on three different Palaeo- to Meso-Proterozoic
orogenic belts; in Fennoscandia, in North American
Grenville and in the Birimian terrane of the West African
craton.
The eastern part of the Sveconorwegian Province, located
in the southwestern part of the Fennoscandian Shield, is
made up of granitiod rocks that were emplaced through
sequential tapping of a reservoir that formed through
mixing between a 2.1–1.9 Ga juvenile component and
Archaean crust. Between 1.7 and 1.4 Ga the continental
crust of the Eastern Segment was reworked with little or
no generation of new crust.
Further to the west, in the Idefjorden terrane of the
Sveconorwegian Province, 1.65 to 1.33 Ga rocks have
isotopic signatures that indicate reworking of older
continental crust, including sediments. However, overall
the isotopic signatures in the Idefjorden terrane indicate
an increase in juvenile material with time, consistent with
development of an extensional back-arc rift geotectonic
setting, accommodating deposition of the local metasedimentary
basin, Stora Le-Marstrand.
Isotope data from rocks within the Grenville orogen in
subsurface Ohio suggest a common c. 1.65 Ga juvenile
source to a majority of the sampled bedrock. Emplacement
of this juvenile crustal contribution was followed
by sequential reworking of that reservoir with little or no
additional contribution to the source.
The c. 2.31–2.06 Ga Birimian terrane in Ghana, West
African craton, is a commonly cited example of plume
initiated crustal growth, that is known to have largely
juvenile signatures. However, we can show that reworked
Archaean crust contribute in a much larger extent than
previously known, once again highlighting the importance
of infracrustal reworking during emplacement of
continental crust. Further, the emplacement of felsic
rocks during the Eoeburnean pre-dates suggested plume
related rocks, contradicting a suggested plume initiated
crustal growth.
Collectively, these studies highlight the importance of
infracrustal reworking in Palaeo- to Meso-Proterozoic
accretionary orogens. These studies also provide good
examples of combined zircon U–Pb-Lu–Hf-(O) isotope
analyses on rocks and rock suites with known affinity
where the validity of chosen models can be justified. (Less) - Abstract (Swedish)
- Popular Abstract in Swedish
För att förstå tillväxten av den kontinentala jordskorpan
är det nödvändigt att kunna uppskatta balansen mellan
juvenilt bidrag från manteln, infra-krustal omarbetning
av jordskorpa och transport av krustalt material tillbaka
till manteln. Sedan början av seklet har användandet
av in situ U–Pb, Lu–Hf och O-isotop analyser av
mineralet zirkon som ett verktyg för att adressera dessa
frågor ökat exponentiellt. Många sammanställningar av
ständigt växande databaser, som använder kombinerade
U–Pb-Lu–Hf och/eller U–Pb-Lu–Hf-O isotop-data,
har presenterats tillsammans med modeller som påvisar
globala... (More) - Popular Abstract in Swedish
För att förstå tillväxten av den kontinentala jordskorpan
är det nödvändigt att kunna uppskatta balansen mellan
juvenilt bidrag från manteln, infra-krustal omarbetning
av jordskorpa och transport av krustalt material tillbaka
till manteln. Sedan början av seklet har användandet
av in situ U–Pb, Lu–Hf och O-isotop analyser av
mineralet zirkon som ett verktyg för att adressera dessa
frågor ökat exponentiellt. Många sammanställningar av
ständigt växande databaser, som använder kombinerade
U–Pb-Lu–Hf och/eller U–Pb-Lu–Hf-O isotop-data,
har presenterats tillsammans med modeller som påvisar
globala konsekvenser för den kontinentala jordskorpans
tillväxt. Många av dessa modeller, lider dock av
ett antal antaganden, bland annat inkluderandet av en
homogen mantelreservoar som utarmats linjärt sedan
jordens skapelse.
Användandet av framför allt detritala zirkoner tagna ur
sitt geologiska sammanhang, och tillämpningen av dess
modell-åldrar, försvagar trovärdigheten hos dessa modeller.
För att ta itu med frågan om den kontinentala
jordskorpans tillväxt, med hjälp av kombinerad zirkon
U–Pb-Lu–Hf (-O) isotop-data, måste man ha kontextuell
kontroll och minimera osäkerheterna i de tillämpade
modellerna.
I denna avhandling har ett sådant tillvägagångssätt använts
på tre olika Palaeo- och Meso-Proterozoiska (2500–1000
miljoner år gamla) orogena bälten; i den Fennoskandiska
skölden, i nordamerikanska Grenville provinsen och i den
Birimiska terrängen på den västafrikanska kratonen.
Den östra delen av den Svekonorvegiska provinsen (belägen
i de sydvästra delarna av den Fennoskandiska skölden)
skapades genom sekventiell omarbetning av en reservoar
som bildades genom blandning mellan en 2.1–1.9
miljarder år gammal juvenil komponent samt Arkeisk
skorpa. Från 1.7 till och med 1.4 miljarder år sedan
genererades den kontinentala jordskorpan med liten eller
ingen tillförsel av juvenilt material.
Längre västerut, i Idefjordsterrängen av Svekonorvegiska
provinsen, återfinns 1.65–1.33 miljarder år gammal
berggrund med isotopsignaturer som indikerar omarbetning
av äldre kontinental jordskorpa och sediment.
På det hela taget indikerar dock isotopsignaturerna från
berggrunden i Idefjordsterrängen en ökning av juvenilt
material med tiden. Detta är i linje med en retirerande
öbåge, samtida med avsättning av den lokala sedimentära
bassängen, Stora Le-Marstrand.
Trender i isotopdata från den Grenvilliska orogenen
under Ohio föreslår juvenilt bidrag från manteln för ca.
1.65 miljarder år sedan, följt av sekventiell omarbetning
av denna reservoar med litet eller inget ytterligare bidrag
från manteln.
Den ca. 2.31–2.06 miljarder år gamla Birimiska terrängen
i Ghana, är känd för att till hög grad uppvisa juvenila
signaturer. Men vi kan visa att omarbetad Arkeisk skorpa
bidragit i mycket större utsträckning än tidigare känt,
vilket återigen betonar vikten av infrakrustal omarbetning
under bildandet av kontinental jordskorpa. Vi kan
även påvisa att denna terräng, som normalt beskrivs som
bildad via initialt bidrag från en mantelplym, har granitiska
bergarter som är äldre än de mafiska leden. Detta
påvisar istället en subduktionsrelaterad tillväxt för den
kontinentala krustan i denna terräng.
Tillsammans understryker dessa studier vikten av infrakrustal
omarbetning i Palaeo- och Meso-Proterozoiska
ackretionsorogener. Dessa studier ger också goda exempel
på tillämpning av kombinerade zirkon U–Pb-Lu–Hf
(-O) isotop- analyser av berggrund med känd affinitet,
där valet av använda modeller kan styrkas. (Less)
Please use this url to cite or link to this publication:
https://lup.lub.lu.se/record/7853963
- author
- Petersson, Andreas LU
- supervisor
- opponent
-
- Professor Hawkesworth, Chris, University of St Andrews
- organization
- publishing date
- 2015
- type
- Thesis
- publication status
- published
- subject
- keywords
- crustal reworking, Proterozoic, O-isotopes, Lu–Hf, U–Pb, zircon, Crustal growth
- in
- Litholund theses
- issue
- 24
- pages
- 171 pages
- publisher
- Department of Geology, Lund University
- defense location
- Dept. of Geology, Lund University, Sölvegatan 12, 223 62, Lund, Sweden
- defense date
- 2015-10-02 13:15:00
- ISSN
- 1651-6648
- 1651-6648
- ISBN
- 978-91-87847-05-9
- 978-91-87847-06-6
- language
- English
- LU publication?
- yes
- id
- bb33da18-045c-4ea2-9f3e-816e3742b681 (old id 7853963)
- date added to LUP
- 2016-04-01 13:15:41
- date last changed
- 2025-04-04 13:55:54
@phdthesis{bb33da18-045c-4ea2-9f3e-816e3742b681, abstract = {{To understand the growth of continental crust, the<br/><br> balance between juvenile mantle derived extraction,<br/><br> infracrustal reworking and crustal recycling, needs to be<br/><br> estimated. Since the beginning of the century, the use of<br/><br> coupled in situ zircon U–Pb, Lu–Hf and O isotope analyses<br/><br> as a tool to address these questions have increased<br/><br> exponentially. Numerous compilations of ever growing<br/><br> datasets have been presented, leading to new, and sometimes<br/><br> contrasting models of continental growth. Many<br/><br> of theses models, however, suffer from a number of<br/><br> assumptions, including a mantle reservoir that has been<br/><br> homogeneously and linearly depleted since the Hadean.<br/><br> Further, the use of (mainly) detrital zircon, taken out<br/><br> of their geological context, and the application of their<br/><br> depleted model-ages clearly hamper the validity of these<br/><br> models.<br/><br> To accurately address the question regarding continental<br/><br> crustal growth using combined zircon U–Pb-Lu–Hf(-O)<br/><br> isotope data, one needs to have contextual control and<br/><br> minimise the uncertainties of the applied models.<br/><br> In papers included in this thesis such an approach has<br/><br> been used on three different Palaeo- to Meso-Proterozoic<br/><br> orogenic belts; in Fennoscandia, in North American<br/><br> Grenville and in the Birimian terrane of the West African<br/><br> craton.<br/><br> The eastern part of the Sveconorwegian Province, located<br/><br> in the southwestern part of the Fennoscandian Shield, is<br/><br> made up of granitiod rocks that were emplaced through<br/><br> sequential tapping of a reservoir that formed through<br/><br> mixing between a 2.1–1.9 Ga juvenile component and<br/><br> Archaean crust. Between 1.7 and 1.4 Ga the continental<br/><br> crust of the Eastern Segment was reworked with little or<br/><br> no generation of new crust.<br/><br> Further to the west, in the Idefjorden terrane of the<br/><br> Sveconorwegian Province, 1.65 to 1.33 Ga rocks have<br/><br> isotopic signatures that indicate reworking of older<br/><br> continental crust, including sediments. However, overall<br/><br> the isotopic signatures in the Idefjorden terrane indicate<br/><br> an increase in juvenile material with time, consistent with<br/><br> development of an extensional back-arc rift geotectonic<br/><br> setting, accommodating deposition of the local metasedimentary<br/><br> basin, Stora Le-Marstrand.<br/><br> Isotope data from rocks within the Grenville orogen in<br/><br> subsurface Ohio suggest a common c. 1.65 Ga juvenile<br/><br> source to a majority of the sampled bedrock. Emplacement<br/><br> of this juvenile crustal contribution was followed<br/><br> by sequential reworking of that reservoir with little or no<br/><br> additional contribution to the source.<br/><br> The c. 2.31–2.06 Ga Birimian terrane in Ghana, West<br/><br> African craton, is a commonly cited example of plume<br/><br> initiated crustal growth, that is known to have largely<br/><br> juvenile signatures. However, we can show that reworked<br/><br> Archaean crust contribute in a much larger extent than<br/><br> previously known, once again highlighting the importance<br/><br> of infracrustal reworking during emplacement of<br/><br> continental crust. Further, the emplacement of felsic<br/><br> rocks during the Eoeburnean pre-dates suggested plume<br/><br> related rocks, contradicting a suggested plume initiated<br/><br> crustal growth.<br/><br> Collectively, these studies highlight the importance of<br/><br> infracrustal reworking in Palaeo- to Meso-Proterozoic<br/><br> accretionary orogens. These studies also provide good<br/><br> examples of combined zircon U–Pb-Lu–Hf-(O) isotope<br/><br> analyses on rocks and rock suites with known affinity<br/><br> where the validity of chosen models can be justified.}}, author = {{Petersson, Andreas}}, isbn = {{978-91-87847-05-9}}, issn = {{1651-6648}}, keywords = {{crustal reworking; Proterozoic; O-isotopes; Lu–Hf; U–Pb; zircon; Crustal growth}}, language = {{eng}}, number = {{24}}, publisher = {{Department of Geology, Lund University}}, school = {{Lund University}}, series = {{Litholund theses}}, title = {{Evolution of continental crust in the Proterozoic : growth and reworking in orogenic systems}}, url = {{https://lup.lub.lu.se/search/files/3262815/7854093.pdf}}, year = {{2015}}, }