PETROGRAFIA REGIONALE

a.a. 2014-2015

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Sergio Rocchisergio.rocchi@unipi.it

URL corso: http://www.dst.unipi.it/dst/rocchi/SR/PR.htmlURL registro: http://unimap.unipi.it/registri/dettregistriNEW.php?re=61052::::&ri=4258

Università di PisaDipartimento di Scienze della Terra

Corso di Laurea Magistrale in Scienze e Tecnologie Geologiche

PROGRAMMA•Toolbox

•geochimica elementi in traccia•geochimica isotopica•geocronologia

•Ciclo Alpino-Appenninico •Stadio di rift Adria-Europa

•Magmatismo intraplacca Triassico-Creataceo•Stadio Oceanico.

•Magmatismo Giurassico e associazioni ofiolitiche del bacino oceanico Ligure-Piemontese•Sedimenti oceanici

•Stadio di arco magmatico•Vulcanismo Oligo-Miocenico della Sardegna•Areniti dell’Appennino settentrionale

•Stadio postcollisionale Alpino•Magmatismo intrusivo delle Alpi e Vulcanismo Eocenico-Oligocenico del Veneto

•Stadio postcollisionale Appenninico ed estensione continentale•Tuscan Metamorphic basement: pre-Variscan times, Variscan Sardinia, Variscan Tuscany•Magmatismo Miocenico-Quat. della Provincia Magmatica Toscana; magmi felsici e mafici della PMT•Vulcanismo Quaternario della Provincia Magmatica Romana e Umbra•Vulcanismo Plio-Quaternario della Provincia Campana•Il problema delle rocce ultrapotassiche

•Stadio di retroarco ed oceanizzazione Tirrenica.•Vulcanismo Plio-Quaternario della Sardegna e del Tirreno meridionale (sottomarino)

•Subduzione ionica.•Vulcanismo Quaternario dell’arco e dei seamounts eoliani

•Avampaese Apulo-Africano •M. Vulture•Etna e Monti Iblei

•Rift del Canale di Sicilia•Vulcanismo Plio-Pleistocenico di Linosa e Pantelleria

PETROGRAFIA REGIONALE

a.a. 2014-2015Sergio Rocchi

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TRACE ELEMENTS TOOLBOX

FRACTIONATION• trace elements

• partial melting YES, if D≠1 • FC : fractional crystallization YES, if D≠1 • AFC : assimilation-FC YES, if D≠1 • time NO

• trace element ratios• partial melting YES, if DA≠DB • FC : fractional crystallization YES, if DA≠DB • AFC : assimilation-FC YES • time NO

• radiogenic isotope ratios• partial melting NO (if equilibrium melting) • FC : fractional crystallization NO (if closed system) • AFC : assimilation-FC YES (open system) • time YES

TRACE ELEMENTS• Big Bang

• 1010K• light nuclei

• spallation• cosmic ray

bombardment of 12C, 16O

• stellar fusion• T>5x107K• Taz: 5x109K: Si–>Fe

• neutron capture• supernova neutron flux• neutron turn to proton

stellar fusion

neutron capture

spallation

Big Bang

Rogers (2008)

TRACE ELEMENTS• la comprensione della natura dell'interno della Terra è basata, oltre i 100 km di profondità, sullo studio di un processo fisico: la propagazione delle onde sismiche

• per comprendere la natura chimica dell'interno della Terra e degli altri pianeti del Sistema Solare si studiano le meteoriti

• meteorite phases: silicates, sulfides, metals• l'analisi di queste fasi indica come ogni elemento sia segregato preferenzialmente in una di esse

• si possono così classificare gli elementi in• elementi litofili concentrati nelle fasi silicatiche • elementi siderofili concentrati nelle fasi metalliche • elementi calcofili concentrati nelle fasi a solfuri • elementi atmofili concentrati in fase gassosa

TRACE ELEMENTS - COSMOCHEMICAL

Rogers (2008)

TRACE ELEMENTS - COSMOCHEMICAL CLASSIFICATION

atmosphereidrosphere

NHe Ne Ar Kr Xe

OH Cl Br I

Li Be B FNa Mg Al SiK CaSc TiRb Sr Y Zr NbCs Ba REE Hf U Th

C P W Ta

Fe Ni V Cr Mn ZnCo Ga Sn

Ru Rh PdOs Ir Pt Au

Ge As SeMo Sb Te

Re

SCu Ag cd InHg Tl Pb Bi

ATMOPHILE

LITHOPHILE

CHALCOPHILE

SIDEROPHILE

crustmantle

core

sulfides

TRACE ELEMENTS• “compatible” elements •facilmente accomodabili nei minerali ignei che cristallizzano per primi

•abundant in the mantle

•“incompatible” elements •Difficilmente accomodabili nelle strutture dei minerali ignei

• abundant in the crust

•r too large, ionic bond (LILE: Large Ion Lithophile Element)

•z too high, covalent bond (HFSE: High Field Strength Element)

Gill (1996)

TRACE ELEMENTS• low concentration• ideal mixing: Raoult’s law

•ai = Xi

• non-ideal mixing: Henry’s law•aij = kij Xij

• distribution coefficient• partition coefficient

•Ka/b = concentration of the element in phase a / concentration in b

• bulk distribution coefficient•D = Sn pa Ka/l •where n=numbers of minerals•f (X, T, P) 0.0001!

0.001!

0.01!

0.1!

1!

10!

La!Ce!Pr!Nd!Sm!Eu!Gd!Tb!Dy!Ho!Er!Tm!Yb!Lu!

olivine!

opx!

cpx!

plag!

spinel!

garnet!

amph!

http://earthref.org/GERM/

TRACE ELEMENTS - GEOLOGICAL CONTROL• partial melting

•batch melting• fractional (Rayleigh) melting

• crystal fractionation•equilibrium crystallization•fractional (Rayleigh) crystallization

• contamination•AFC•zone refining

• dynamic processes•dynamic melting•RTF (Replenishement, Tapping, Fractionation)

• sedimentary processes• hydrothermal and metasomatic processes

TRACE ELEMENTS - PARTIAL MELTING - CAUSES•magma generates when the geotherm overcomes the solidus curve

•mantle partial melting yields basaltic magmas

•crust partial melting yields rhyolitic magmas

•melting is possible if:

solidosolido

+ liquido

liquido

curva temperaturedi Solidus

(inizio fusione)

curva T diLiquidus(fusione

completa)

geoterma

TEMPERATURA

PRES

SIO

NE

- PR

OFO

ND

ITA'

C

A

B

A.increase of source T (unlikely in the mantle, common in the crust)

C.Solidus moves to lower (fluids into the source)

B.decrease of ource P (adiabatic decompression by thinning of the overlying mantle)

TRACE ELEMENTS - PARTIAL MELTING - TYPES• heat-induced melting

•collision belt (continental crust)

• decompression melting•mid-ocean ridge •intraplate (hotspot, intracontinental rift)

• volatile-induced melting•subduction zone

• batch melting•melt and solid residue remain in equilibrium during melting•melt accumulates•melt segregates as a batch from the residue

• fractional melting• incremental melting

TRACE ELEMENTS - BATCH MELTING

• F = fraction of melt formed (wt%)• D = bulk distribution coefficient• C0 = concentration of the element in the solid source• CL = concentration of the element in the batch melt

• C0 = F CL + (1-F) CS • C0 = F CL + (1-F) D CL

• CL = C0 / [F + D(1-F)]

TRACE ELEMENTS - NON-MODAL MELTING

• P = Sn pa Ka/l where n = number of minerals entering the melt

• D0 = Sn Xa Ka/l where n = number of minerals in the source

• D = (D0 – F P) / (1 – F)

• CL = C0 / [F + D(1-F)] • CL = C0 / [D0 + F(1+P)]

TRACE ELEMENTS

• depleted mantle•non-modal batch melting

•REE

• primitive mantle•non-modal batch melting

•REE•incompatible elements

TRACE ELEMENTS - MULTIELEMENT PLOTS• element ordering

•mobile elements increases incompatibility from left to right

•immobile elements increases incompatibility from right to left

• normalization•chondrite•primitive mantle•MORB

TRACE ELEMENTS - MULTIELEMENT PLOTS

• MORB•chondrite-normalized•N-MORB normalized

Sanfilippo & Tribuzio (2011)

TRACE ELEMENTS - MULTIELEMENT PLOTS• OIB

•REE: chondrite-normalized•incompatible elements: primitive mantle-normalized

Rocchi et al. (2002); Nardini etal. (2009)

TRACE ELEMENTS - MULTIELEMENT PLOTS

• CAB-VAB-IAB•incompatible elements: N-MORB mantle-normalized

TRACE ELEMENTS - COVERGENT SETTING

• mantle wedge (convective mantle-subcont. lithosphere)•OIB (oceanic and cont.) vs. MORB•% “within-plate” enrichment

• componente subduttivo•conservative elements• non-conservative elements (slab-derived ⇒ slab-related)

•% “subduction zone” enrichment

• crust•lower crust

•melting of mafic sources•MASH-refilling

•upper crust•melting of pelitic sources•AFC-MFC

• island arc vs contin. arc• crustal contribution?

0

20

40

60

80

100

Ba Rb Th U Sr La Ce Pr Nd Sm Gd

% arricchimento dovuto al componente subduttivo

CsTl

RbBa

ThU

TaNb

KLaCe

PbPr

SrPNd

Zr Sm Gd TbHf Eu Ti Dy

YHo

ErTm

YbLu

0.1

1

10

100

SZSZ

WPWP

MM

TRACE ELEMENTS - DISCRIMINATION DIAGRAMS

TRACE ELEMENTS - DISCRIMINATION DIAGRAMS

TRACE ELEMENTS - DISCRIMINATION DIAGRAMS

TRACE ELEMENTS

TRACE ELEMENTS - MAGMA VS SEDIMENTS

PETROGRAFIA REGIONALE

a.a. 2014-2015

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ISOTOPE GEOCHEMISTRY TOOLBOX

ISOTOPIC EVOLUTION OF SR

residual solid (depleted)

partial

melt

(enri

ched)

UR (87 Rb/86 Sr=0.0827)

87Sr

/86Sr

Earth’sformation Todaymantle

partialmelting

0.7045eSr=0

eSr>0

eSr<0

SR-ND SYSTEMATICS OF MORBS

SR-ND SYSTEMATICS OF OCEANIC BASALTS

Faure (1986)

SR-ND SYSTEMATICS OF CONTINENTAL BASALTS

Faure (1986)

SR-ND SYSTEMATICS OF VOLCANIC ARCS

Faure (1986)

MAGMA MIXTURES

Lustrino & Wilson (2007)

MAGMA MIXTURES

Faure (1986)

RB-SR AGE DETERMINATION• isochron line• y  =  b  +  mx  • m  =  elt-­‐1    »»»      t  =  1/l  ln(m+1)  • b  =  (87Sr/86Sr)i

87Rb/86Sr

87Sr

/86Sr

WR Kfs Bt

isochron line

b=(87Sr/86Sr)im

ISOTOPIC EVOLUTION OF ND

residu

al solid

(deple

ted)

partial melt (enriched)

CHUR (147 Sm/144 Nd=0.1967)

143 N

d/14

4 Nd

Earth’sformatio Todaymantle

partialmelting

0.512638eNd=0

eNd>0

eNd<0

ND MODEL AGE• eNd = [(143Nd/144Nd)sample(t) / (143Nd/144Nd)CHUR(t) – 1] x 104

residual solid (depleted)

partial melt (enriched)CHUR ( 147Sm/ 144Nd=0.1967)

143 N

d/14

4 Nd

Earth’sformationToday mantle

partialmelting

0.512638eNd=0

eNd>0

eNd<0

ND MODEL AGE

• eNd = [(143Nd/144Nd)sample(t) / (143Nd/144Nd)CHUR(t) – 1] x 104

Depleted Mantle eNd = 8.6 – 1.91 T ( 147Sm/ 144Nd=0.222)

CHUR ( 147Sm/ 144Nd=0.1967)

143 N

d/14

4 Nd

Earth’sformationToday

0.512638eNd=0

eNd=8.6

• eNd = [(143Nd/144Nd)sample(t) / (143Nd/144Nd)CHUR(t) – 1] x 104

ND MODEL AGE

Depleted MantleeNd = 8.6 – 1.91 T

CHUR (147Sm/144Nd=0.1967)

Earth’sformation

Today mantlepartialmelting

0eNd

crustpartialmelting

ND MODEL AGE

Depleted MantleeNd = 8.6 – 1.91 T

(147Sm/144Nd=0.222)

CHUR (147Sm/144Nd=0.1967)

Earth’sformationToday mantle

partialmelting

0eNd

crustpartialmelting

TDM

TDM

TCHUR =1λln 1+

(143Nd /144 Nd)sample − (143Nd /144 Nd)CHUR

(147Sm /144 Nd)sample − (147Sm /144 Nd)CHUR

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