PETROGRAFIA REGIONALE

Transcript

1 Università di Pisa Dipartimento di Scienze della Terra Corso di Laurea Magistrale in Scienze e Tecnologie Geologiche PETROGRAFIA REGIONALE a.a Sergio Rocchi sergio.rocchi@unipi.it URL corso: URL registro: 1 Toolbox geochimica elementi in traccia geochimica isotopica geocronologia PROGRAMMA 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

2 PETROGRAFIA REGIONALE a.a Sergio Rocchi TRACE ELEMENTS TOOLBOX 3

3 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 FC : fractional crystallization AFC : assimilation-fc time NO (if equilibrium melting) NO (if closed system) YES (open system) YES Big Bang K light nuclei spallation cosmic ray bombardment of 12 C, 16 O stellar fusion T>5x10 7 K Taz: 5x10 9 K: Si >Fe neutron capture supernova neutron flux neutron turn to proton TRACE ELEMENTS Big Bang stellar fusion neutron capture spallation Rogers (2008)

4 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)

5 TRACE ELEMENTS - COSMOCHEMICAL CLASSIFICATION ATMOPHILE LITHOPHILE Li Be B Na Mg Al Si K Ca F Sc Ti Rb Sr Y Zr Nb Cs Ba REE Hf U Th N He Ne Ar Kr Xe O H Cl Br I atmosphere idrosphere crust mantle SIDEROPHILE C P W Ta core Fe Ni Co Ga Sn V Cr Mn Zn Ru Rh Pd Os Ir Pt Au Ge As Se Mo Sb Te Re S Cu Ag cd In Hg Tl Pb Bi sulfides CHALCOPHILE compatible elements facilmente accomodabili nei minerali ignei che cristallizzano per primi abundant in the mantle TRACE ELEMENTS 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)

6 low concentration ideal mixing: Raoult s law TRACE ELEMENTS 10! ai = Xi non-ideal mixing: Henry s law ai j = ki j Xi j distribution coefficient partition coefficient Ka/b = concentration of the element in phase a / concentration in b 0.1! 0.01! bulk distribution coefficient 0.001! D = S n pa Ka/l where n=numbers of minerals f (X, T, P) ! 1! La! Ce! Pr!Nd!Sm!Eu!Gd!Tb!Dy!Ho!Er!Tm!Yb! Lu! olivine! opx! cpx! plag! spinel! garnet! amph! 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

7 TRACE ELEMENTS - PARTIAL MELTING - CAUSES magma generates when the geotherm overcomes the solidus curve TEMPERATURA mantle partial melting yields basaltic magmas crust partial melting yields rhyolitic magmas melting is possible if: A.increase of source T (unlikely in the mantle, common in the crust) PRESSIONE - PROFONDITA' geoterma C A liquido B.decrease of ource P (adiabatic decompression by thinning of the overlying mantle) solido B solido + liquido C.Solidus moves to lower (fluids into the source) curva temperature di Solidus (inizio fusione) curva T di Liquidus (fusione completa) 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

8 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 = S n pa Ka/l where n = number of minerals entering the melt D0 = S n 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)]

9 depleted mantle non-modal batch melting REE primitive mantle non-modal batch melting REE incompatible elements TRACE 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

10 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)

11 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? % arricchimento dovuto al componente subduttivo SZ WP M Cs Rb Th Tl Ba Ta U Nb K Ce Pr La Pb Sr P Zr Sm Gd Tb Y Er Yb Nd Hf Eu Ti Dy Ho Tm Lu Ba Rb Th U Sr La Ce Pr Nd Sm Gd

12 TRACE ELEMENTS - DISCRIMINATION DIAGRAMS TRACE ELEMENTS - DISCRIMINATION DIAGRAMS

13 TRACE ELEMENTS - DISCRIMINATION DIAGRAMS TRACE ELEMENTS

14 TRACE ELEMENTS - MAGMA VS SEDIMENTS PETROGRAFIA REGIONALE a.a ISOTOPE GEOCHEMISTRY TOOLBOX 28

15 ISOTOPIC EVOLUTION OF SR esr>0 87 Sr/ 86 Sr UR ( 87 Rb/ 86 Sr=0.0827) partial melt (enriched) residual solid (depleted) esr=0 esr<0 Earth s formation mantle partial melting Today SR-ND SYSTEMATICS OF MORBS

16 SR-ND SYSTEMATICS OF OCEANIC BASALTS Faure (1986) SR-ND SYSTEMATICS OF CONTINENTAL BASALTS Faure (1986)

17 SR-ND SYSTEMATICS OF VOLCANIC ARCS Faure (1986) MAGMA MIXTURES Lustrino & Wilson (2007)

18 MAGMA MIXTURES Faure (1986) RB-SR AGE DETERMINATION isochron line y = b + mx m = e lt - 1»»» t = 1/l ln(m+1) b = ( 87 Sr/ 86 Sr)i 87 Sr/ 86 Sr isochron line b=( 87 Sr/ 86 Sr)i m WR Kfs Bt 87 Rb/ 86 Sr

19 ISOTOPIC EVOLUTION OF ND end>0 143 Nd/ 144 Nd CHUR ( 147 Sm/ 144 Nd=0.1967) residual solid (depleted) partial melt (enriched) end=0 end<0 Earth s formatio mantle partial melting Today ND MODEL AGE end = [( 143 Nd/ 144 Nd)sample(t) / ( 143 Nd/ 144 Nd)CHUR(t) 1] x 10 4 end> end=0 end<0 143 Nd/ 144 Nd residual solid (depleted) partial melt (enriched) CHUR ( 147 Sm/ 144 Nd=0.1967) Today mantle partial melting Earth s formation

20 ND MODEL AGE end = [( 143 Nd/ 144 Nd)sample(t) / ( 143 Nd/ 144 Nd)CHUR(t) 1] x 10 4 end=8.6 end = [( 143 Nd/ 144 Nd)sample(t) / ( 143 Nd/ 144 Nd)CHUR(t) 1] x 10 4 Depleted Mantle end = T ( 147 Sm/ 144 Nd=0.222) end=0 CHUR ( 147 Sm/ 144 Nd=0.1967) 143 Nd/ 144 Nd Today Earth s formation ND MODEL AGE Depleted Mantle end = T end 0 CHUR ( 147 Sm/ 144 Nd=0.1967) Today crust partial melting mantle partial melting Earth s formation

21 ND MODEL AGE T CHUR = 1 λ ln 1+ (143 Nd / 144 Nd) sample ( 143 Nd / 144 Nd) CHUR ( 147 Sm / 144 Nd) sample ( 147 Sm / 144 Nd) CHUR TDM TDM Depleted Mantle end = T ( 147 Sm/ 144 Nd=0.222) end 0 CHUR ( 147 Sm/ 144 Nd=0.1967) Today crust partial melting mantle partial melting Earth s formation