Download Report

RiPetERò
Ricerca Petrologica (e non solo) in Emilia Romagna
10 aprile 2015, ore 10
Dipartimento di Scienze Biologiche Geologiche e Ambientali
Via Zamboni 67 (ex plesso Geologia)
AULA G1
Info @: [email protected]
[email protected]
1
Programma Scientifico
10:00 Daniele Brunelli (unimore)
RiPetERò – Ricerca Petrologica in Emilia Romagna
Il senso di questa giornata
10:10 Pierpaolo Giacomoni (unife)
RECONSTRUCTION OF MAGMATIC CONDITIONS DRIVING
ERUPTIONS AT MT. ETNA
During the recent activity of Mount Etna eruptions are triggered by magma
mixing or by decompression of shallow (6-4 km b.s.l.) magma batches. In such
a type of feeding system, mixing occurs between magmas with similar
geochemical features but that underwent to different fractionation histories,
constrained by the intensive physical parameters of the magmatic system:
pressure (P), temperature (T), oxygen fugacity (fO2) and volatiles content
(XH2O-CO2).
In this contribution, we face up different aspects of the crystallization history of
Etnean magmas from the mantle source to the surface, focusing on textural
and compositional variations of clinopyroxene and plagioclase as a tool to
record changes in the physical and chemical parameters of the magmatic
system.
Crystal-melt equilibrium equations and thermodynamic modeling were applied
to determine the chemical and physical constraints of the magmatic system.
The overall picture highlights that Mt. Etna feeding system is a vertically
extended and continuous without any extended long-lived magma chambers.
Crystallization occurs under polybaric conditions which at least two magma
ponding levels between 10-8 km b.s.l. and 6-4 km b.s.l. At these depths, basic
magmas with different water content frequently mix some months before
eruptions.
10:30 Daniele Redi (unibo)
SOMMA-VESUVIUS’S ACTIVITY OVER THE LAST 33 kA
YEARS: A MINERAL CHEMISTRY PROSPECTIVE
The composition of pristine mineral phases within volcanic products can
provide useful information to better understand volcanoes' behaviour. A
detailed study of clinopyroxenes and olivines led to indicate magma residence
times and magma supply rate as the likely main factors controlling eruption
style at Somma-Vesuvius
10:50 Emiliano Barbieri (unimore)
INTERAZIONE TRA UN PUNTO CALDO E UN RIFT EVOLUTO:
IL RUOLO E L’EVOLUZIONE CHIMICA DEL PLUME AFAR
Il Plume Afar è da sempre considerato come uno degli attori principali,
coinvolti nelle dinamiche di rifting che interessano la regione orientale della
placca africana, ma la sua persistenza attuale al di sotto della Depressione
Dancala è ancora causa di dibattito. Il confronto tra i basalti moderni e quelli
più antichi, legati all'impatto della testa del punto caldo, è fondamentale per
identificare le sorgenti magmatiche alla base del moderno magmatismo Afar,
nonché per modellarne gli apporti e la loro evoluzione nel tempo. I dati
geochimici ottenuti in questo lavoro, hanno permesso di caratterizzare con
precisione i moderni basalti eruttati nell'Afar settentrionale e nella regione di
Asal, delineando una zonazione del segnale del plume e la sua decrescita
allontanandosi dall'Erta Ale Range, probabilmente corrispondente all’attuale
localizzazione del punto caldo. I rilevanti arricchimenti in elementi in tracce e i
rapporti isotopici testimoniano che, nonostante l'instaurarsi di un setting
geologico prossimo all’oceanizzazione, l'apporto principale di fusi è legato
ancora a processi relativamente profondi (> 80 km). Ciò che si può osservare
è un graduale mutamento dei contributi dei diversi domini del mantello
2
coinvolti, conseguente all’eterogenetià interna del Plume Afar e alla crescente
importanza assunta dall’astenosfera, come sorgente magmatica, a scapito del
mantello litosferico, soggetto, nel tempo, a importanti processi di erosione
termomeccanica.
11:10 Claudio Natali (unife)
PICRITES ASSOCIATED TO NORTHERN ETHIOPIAN-YEMENI
CFB AND THEIR RELEVANCE TO MANTLE PLUME
PROCESSES
Geochemical and petrological data indicate that the 30 Ma Northern Ethiopian
continental flood basalts and picrites were generated in connection with the
“Afar plume”. Previous studies [1] show that: a) Basaltic lavas appear zonally
arranged with Low-Ti tholeiites (LT) in the west, High-Ti tholeiites (HT1) to the
east and very High-Ti transitional basalts and picrites (HT2,TiO2 4-6.5 wt%)
closer to the Afar triple junction; b) the P-T conditions of magma generation
increased from 1.3 GPa/1200 °C to 3.0 GPa/1500 °C from west to east; that is,
from the outer zones (LT) to the core of the plume head where HT2 ultratitaniferous picrites were generated.
Further sampling has been carried out in the inferred plume axial zone
(Lalibela area) focusing on picrite rocks, as well in the Yemeni counterpart
where analogous HT2 products (including picrites) are recorded in the
Manakhah section.
New isotopic data integrated with those available in the literature [2] show
correlations between TiO2 (and other incompatible elements) and Sr-Nd-PbHe isotopic data, thus defining the isotopic fingerprint of the plume-related
metasomatic agents. The comparison of isotopic signatures between bulk rock
and clinopyroxene phenocrysts highlight the petrogenetic complexity of the
HT2 basalt-picrite suite that could be ascribed to: 1) wide PT range of magma
formation; 2) dynamic partial melting and lithosphere interaction during
uprising and 3) magma mixing during crystallization.
Phase equilibria constraints and melt inclusion data, as well as trace element
distribution indicate that, despite the occurrence of olivine cumulus processes,
many picrite-basalt lavas represent true near primary magmas.
Petrological modeling indicates that the resulting metasomatized mantle
sources were characterized by hydrous, iron-titanium-alkali rich exotic
parageneses including amphibole, phlogopite and Ti-bearing minerals.
(L. Beccaluva1, G. Bianchini1, R. Ellam2, A. Savo1, F. Siena1, F. Stuart2)
2
Scottish Universities Environmental Research Center, East Kilbride, Glasgow
(UK)
[1] Beccaluva et al. (2009). J. Petrol. 50, 1377-1403.
[2] Pik et al. (1999). Geochim. Cosmochim. Acta 63, 2263-2279.
11:30 Claudia Gori (unipr)
PIROSSENI SINTETICI PER APPLICAZIONI CERAMICHE
Progetto giovani, linea Materiali avanzati (in particolare ceramici) per
applicazioni strutturali
L’obiettivo dell’attività di dottorato è definire la composizione, le caratteristiche
strutturali, le proprietà fisiche, colorimetriche ed elettromagnetiche di pirosseni
sintetici e delle loro soluzioni solide. La struttura del pirosseno, resistente alle
alte temperature e alla lisciviazione, è considerata un potenziale candidato per
la produzione di pigmenti ceramici. Per studiare e caratterizzare il
comportamento dei pirosseni in campo ceramico e definire la resa del colore
dovuta all’introduzione di elementi coloranti (di transizione) nei siti cationici
della struttura, si studiano pirosseni a Zn2+, Co2+, Mg2+, Mn2+, Fe2+, etc.,
ottenuti con tecniche di sintesi in condizioni di alta pressione e alta
temperatura (presso i laboratori dell’Istituto IMEM di Parma).
I campioni sintetici ottenuti vengono analizzati con diverse tecniche:
diffrazione da raggi X su polveri (XRD) e da cristallo singolo, per ottenere
3
informazioni sulla struttura cristallina e sulla distribuzione degli ioni cromofori
nei siti cristallografici; microscopia elettronica a scansione (SEM) con annessa
microanalisi EDS, per ottenere informazioni chimico-composizionali dei
campioni; spettroscopia (FT-IR, micro-Raman, Mössbauer, EXAFS-XANES) e
colorimetria, per ottenere informazioni sulla struttura locale all’intorno dei
cromofori e sulle cause del colore. L’insieme dei dati può portare ad
applicazioni di tipo tecnologico nell’ambito dell’industria ceramica. Si
prevedono anche possibili studi e implicazioni nella geochimica degli elementi
minori nei pirosseni del mantello terrestre.
11:50 Jasmine Petriglieri (unipr)
PRELIMINARY STUDY ON POLYMORPHS OF SERPENTINE
OF THE KONIAMBO MASSIF (NEW CALEDONIA)
Serpentinites are rocks formed mostly by serpentine group minerals:
chrysotile, antigorite, lizardite and polygonal serpentine. They are formed by
hydration of ultramafic rocks rich in olivine and contain up to 13 wt% H2O.
They play an essential role in numerous geological settings and control the
rheology of the lithosphere where aqueous fluids interact with ultramafic rocks
[1]. The fibrous type (e.g. chrysotile) of serpentine group minerals, along with
several amphibole varieties (e.g. actinolite, tremolite), are the major
components of asbestos family. Unfortunately, the breathing of fine fibrous
asbestos powder is linked to diseases such as pleural mesothelioma and
asbestosis. The identification of the main varieties of the serpentine group,
laminated or fibrous, requires some attention due to public health problems
and for the safety of the operators. There are many studies in the literature
about the characterization of the minerals of this family, but a complete
methodology, able to distinguish the different polymorphs of the group, is still
lacking. This work introduces an innovative analytical strategy that allows to
recognize these polymorphs, involving Raman spectroscopy. The Koniambo
massif is part of a mountain chain located along the west coast of Grande
Terre island, the main island of New Caledonia archipelago. It is composed of
three major lithological assemblages of mantle and crustal origin: a strongly
serpentinized harzburgite-dunite sequence at the base, followed by a spinel
dunite sequence and at the top a succession of layers of harzburgite and
minor dunite, which changes to harzburgite on the summit. These associations
overlap the Poya Unit, a portion of the upper part of the oceanic crust
containing basalts, gabbros and dolerites. All these sequences represent
portions of obducted oceanic plate as a result of compressive tectonics [2].
Samples, coming from the basal and middle sequences of the massif, were
studied by means of optical microscopy, scanning electron microscopy with Xray microanalysis (SEM-EDS) and Raman spectroscopy. The main
contribution provided by optical microscopy and SEM analysis is the
observation of textural relationships and morphological features of the different
phases. Moreover, Raman spectroscopy is essential during the identification
of the polymorphs of serpentine group. Raman peaks observed in the highfrequency spectral range 3550-3850 cm-1 associated with OH stretching
vibrations, allow the identification of chrysotile, lizardite, antigorite and
polygonal serpentine varieties [3]. However, spot analyses alone are not fully
adequate for the study of the relationship between the different varieties of
serpentine in complex samples, such as in natural ophiolites. This limit was
overcome by performing two-dimensional Raman maps. The main advantage
is to recognize the serpentine polymorphs directly on the sample, within their
textural environment at the micrometer scale. Raman maps were obtained on
a square or rectangular matrix of point: typical size was 25x25 point, with a
step between 1 and 2 micrometers. The acquisition time for each point was
about 60 seconds. The false color images were obtained by associating the
intensities of the different colors to the area of the OH stretching bands
characteristic of the different polymorphs. The areas were determined by fitting
of the Raman spectra using gauss-lorentzian functions, after a proper
background removal. All the measurements were carefully calibrated using
spectral lamps. The experimental method developed in this work allowed the
full characterization of the serpentinization process of the studied samples.
4
This strategy is very effective in the study of mineralogical-petrologic samples,
but it can be extended to other fields of investigation, such as the
characterization of building materials or the analysis of lung tissue biologicalhistological samples of patients suffering from asbestosis or pleural
mesothelioma.
[1] Guillot S. and Hattori K. (2013) Elements, 9, 95-98.
[2] Ulrich M. et al (2010). Lithos, 115, 223-236.
[3] Auzende A. L. and Daniel I. (2004) Phys Chem Minerals, 31, 269-277.
12:10 Claudia Stangarone (unipr)
UNRAVELLING THERMAL EMISSIVITY SPECTRA OF THE
MAIN MINERALS ON MERCURY’S SURFACE BY MEANS OF
EXPERIMENTAL AND AB INITIO CALCULATED IR-HT
VIBRATIONAL FREQUENCIES
Tribaudino, M.1, Prencipe, M.2
1
Università degli Studi di Parma, DiFeST, “Macedonio Melloni”
2
Università degli Studi di Torino, Dipartimento di Scienze della Terra
My PhD is articulated on two parallel lines: a first one, theoretical, based on
the calculation of IR vibrational frequencies at different environmental
conditions (high temperature) of minerals that are considered to be the major
constituents of Mercury’s surface (pyroxenes and feldspar); on the other hand,
an experimental investigation, based on the collection and interpretation of
experimental data (thermal emissivity spectra, IR reflectance measurements).
The project involves several steps. First one: to simulate spectroscopic
properties of the candidate phases at room conditions, with the least possible
number of empirical a priori information. To do so, calculations are performed
using CRYSTAL14, a quantum chemistry program for ab initio methods. The
calculations are being carried out at the University of Parma, where the
program CRYSTAL14 runs on the available computing resources. The studied
phases are some clino and orthopyroxenes, namely diopside and enstatite,
and albite feldspar. The room temperature IR and Raman experimental
spectra were simulated, including peak positions and intensities.
Second step involves the calculation of HT/IR vibrational frequencies, in
cooperation with the Dipartimento di Scienze della terra of Turin University. At
present the simulation of the IR frequencies at higher temperature of enstatite
is in progress.
A third step will be the experimental collection and processing of HT/IR
spectra of the considered minerals (pyroxenes and feldspars), which is
forseen to be carried out at the Institute of Planetary Research (BerlinAdlershof, DLR), collaborating with IR spectroscopy laboratory/Planetary
Emissivity Laboratory (PEL).
The goal is to test and simulate the environmental conditions of the inner
planets of Solar System, creating models to interpret planetary spectral
signatures of the above mineralogical families. The aspected results will
provide also an experimental background to develop and to understand data
that will be collected by MERTIS, a spectrometer developed by DLR, that will
be on board of the next ESA spacecraft, BepiColombo, whose launch is
scheduled for July 2016.
References
Helbert, J., and Maturilli, A. (2009) The emissivity of a fine-grained labradorite
sample at typical Mercury dayside temperatures. Earth and Planetary Science
Letters, 285, 347–354.
Dovesi R., Saunders V. R., Roetti C., Orlando R., Zicovich-Wilson C. M.,
Pascale F., Civalleri B., Doll K., Harrison N. M., Bush I. J., D’Arco P., Llunell
M., Causà M. & Noël Y. 2014. CRYSTAL14 User's Manual. University of
Torino.
Donaldson H, Cheek L. C., Pieters C. M., Mustard J. F., Greenhagen B.T.,
Thomas I. R. and. Bowles E., 2014. Global assessment of pure crystalline
5
plagioclase across the Moon and implications for the evolution of the primary
crust J. Geoph Research: Planets Volume 119, Issue 7, pages 1516–1545
12:30 Deborah Lo Pò (unibo)
QUANTIFYING FERRIC IRON CONTENT IN HEMATITE-RICH
METASEDIMENTS: A THERMODYNAMIC MODELLING
APPROACH
No more lengthy titration procedure or painful assumption on stoichiometry of
minerals. Just go perplex and calculate an effective ferric iron amount for your
metapelite
12:50 Pausa tarallucci e vino
14:00 Valentina Brombin (unife)
PETROLOGICAL STUDY OF THE LITHOSPHERIC SEGMENT
RESPONSIBLE FOR THE TERTIARY SUDALPINE MAGMATIC
PROVINCE
The Tertiary Magmatic Province of Veneto (VTMP) in the North-East of Italy
represents the most important magmatic province of the Adria Plate and is
composed of five districts: Val d’Adige, Marosticano, Lessini Hills, Berici Hills
and Euganei Hills. In these areas basaltic lithotypes-from tholeiitic to
nephelinitic in composition- are found. Lessinean and Marostican nephelinites
and basanites rocks carry mantle xenoliths (mainly lherzolites and
hazburgites). This large range of basic magmas was erupted due to
extensional tectonics in the Southern Alps intraplate domain during the
Paleogene. From 70s up to now, extensive, but fragmented, geochemical and
petrological studies of mantle xenoliths have characterized the VTMP
lithospheric domain. The new challenge is now to enrich the sampling of the
district (basaltic rocks and mantle inclusions) in order to determine (1) spatial
and time variations of basalts and xenoliths’ major, minor chemical elements
and isotopic signatures; (2) volumetric and effusion ratios of Tertiary Sudalpine
Magmatic Province lavas; (3) the amount of issued volatiles during the
effusion of Tertiary Sudalpine Magmatic Province lavas.
In this presentation I’ll summarize the petrological state of art of Tertiary
Magmatic Province of Veneto, highlighting the lack of crucial geochemical
information in this well-known magmatic district.
14:20 Bibiana Förster (unibo)
A HAND SAMPLE VIEW ON THE THE ULTEN ZONE
The Ulten Zone is thought to be a bunch of amphibole-rich peridotites with
garnet. Right, but there’s more than that
14:40 Beatrice Pelorosso (unife)
PETROLOGICAL STUDY OF GREENE POINT MANTLE
XENOLITHS, NORTHERN VICTORIA LAND, ANTARCTICA
A petrological study of mantle, anhydrous spinel-bearing lherzolites and
harzburgites from Greene Point (GP) (Northern Victoria Land, NVL), have
been carried out, with the aim to characterize the lithospheric mantle beneath
NVL.
Based on mineral major and trace element models, this mantle domain is
supposed to represent a residuum after 10 and 20% of partial melting.
Moreover, melting models and isotopic results evidence the large contribution
of tholeiitic melts percolating through peridotites in producing the geochemistry
of GP mantle xenolith suite. At fixed P of 15 kbar, T and fO2 (950°C; Δlog fO2
(QFM) -1.70 to -0.38) values, calculated on the basis of Ballhaus et al., 1991
geothermometer, confirm the tendency for anhydrous GP xenolith population
6
to have higher equilibration T and comparable redox condition with respect to
the nearby hydrous Baker Rocks peridotites.
15:00 Arianna Secchiari (unipr)
GEOCHEMISTRY AND TECTONIC SIGNIFICANCE OF ULTRADEPLETED PERIDOTITES OF NEW CALEDONIA
In spite of pervasive serpentinisation and prominent weathering, New
Caledonia hosts one of the largest supra-subduction mantle section worldwide
and hence provides an unique opportunity to study upper mantle processes
along convergent margins. The New Caledonia Peridotitic Nappe consist of an
“atypical” ophiolitic sequence, dominated by harzburgitic rocks with minor
spinel and plagioclase lherzolites. Cumulitic mafic-ultramafic rocks are also
present at the top of the sequence in the Massif du Sud, while basalts are
completely absent. Although these ophiolites have been studied for almost 30
years, their age, origin and geodynamic evolution still remain unclear.
Previous geochemical studies revealed that harzburgites are ultradepleted
rocks, making their geochemical characterization an analytical challenge.
Lherzolites, on the other hand, are still poorly known and their geodynamic
affinity is uncertain. In this presentation we will focus on the petrographic,
mineralogical and geochemical chracterization of a new set of peridotites from
New Caledonia. We will also show the first Sr-Nd isotope data obtained for
these rocks. Our results are consistent with a multi-stage history of melting,
deformation, recrystallization and melt-rock interaction. Radiogenic isotope
analyses (Sr, Nd, Pb) on a new batch of samples (in progress) will provide
unique informations about the isotopic composition of depleted mantle
domains preserved in supra-subduction ophiolites. In addition, Sm-Nd
geochronology on separated cpx-plagioclase pairs from gabbroic rocks is
expected to provide time constraints on the magmatic event that originated the
New Caledonia intrusive sequence and on the the geodynamic evolution of the
South Pacific zone.
7