High-T heating stage: application for igneous petrogenesis and mantle processes

- melt inclusions as key tools -

SZABÓ, Csaba

Lithosphere Fluid Research Lab (LRG),

Department of Petrology and Geochemistry,

Institute of Geography and Earth Sciences,

Eötvös University (ELTE), Budapest

H-1117 Budapest (HUNGARY)

http://lrg.elte.hu

ANNO 1998ELTE

LRG

http://lrg.elte.hu/oktatas/

• Stage + controller:

• Small ceramic furnace with a hole at the bottom, covered by sapphire, to provide transmitted light for observation during experiment.

• Quartz lid window for observation.

• Gas valves to purge the sample chamber with inert gas.

• Water valves hooked up with a sealed circulating water tank to keep the stage at low T during heating experiment.

High-T heating stage (Linkam)

Purpose of use of the stage: - to study melt inclusions,- to obtain (partially) homogenized melt,- to record melting sequence (crystallization,

identification of phases).

PART-I: Forewords on melts and melt inclusions

PART-II: Method of melt inclusion study, instrumental/analytical techniques

PART-III: Magma drops in olivine, spinel, clinopyroxene, plagioclase andquartz phenocrysts of volcanic rocks (+apatite, zircon)

PART-IV: Silicate melts and melt inclusions as evidences for mantleenrichment, interaction, and immiscibility

Melt inclusions, in general, are small droplets of any kind of melts enclosed in a host mineral, which were trapped accidentally at lithospheric mantle and crustal temperatures and pressures, and subsequently quenched or partially

or totally crystallized.

Why do we study melt inclusions trapped under lithosphere conditions andoccurring in any kind of rocks?

To figure out physical conditions of trapping and compositions of the trapped melt(behind these, evolution, interaction, crystallization/solidification, immiscibility, etc.)

Possible melts trapped under lithospheric mantle and crustal conditions regardlessof primary or secondary entrapment:

• Silicate melt (ultramafic, mafic, neutral and acidic rocks)

• Carbonatite melt (alkali and ultramafic rocks)

• [Sulfide melt (ultramafic and mafic rocks)]

In the lithosperic environments silicate melt inclusions are the most abundant,however carbonatite [and sulfide] melt inclusions also occur and are relevant to thefocus of interest.

Mantle melts – in general

Examples for different melt inclusions

Primary silicate melt inclusion in orthopyroxene from spinel lherzolite xenolith in basalt (Hungary)

Primary silicate melt inclusion inorthopyroxene from pyroxenite xenolith inbasalt (Hungary)

Interstitial sulfide inclusion in spinel lherzolitexenolith in lamprophyre (Hungary)

opx

glass

bubble

pn

cp

MSS olcpx

opx

glass

bubble

Primary silicate melt inclusions in spinelfrom basalt (Albania)

30 m 30 m

10 m200 m

CO2 50 m

PART-I: Forewords on melts and melt inclusions

PART-II: Method of melt inclusion study, instrumental/analytical techniques

PART-III: Magma drops in olivine, spinel, clinopyroxene, plagioclase andquartz phenocrysts of volcanic rocks (+apatite, zircon)

PART-IV: Silicate melts and melt inclusions as evidences for mantleenrichment, interaction, and immiscibility

Method of melt inclusion study

Room temperature

Low temperature(freezing experiments)

Petrography (presence of glass, crystallized and/orvolatile phases, rations)

Image analysis

SEM

Major element chemical analysis (EPMA) on solidphases mass balance calculation (rough estimationof bulk composition)

Spectroscopic methods (e.g., Raman, IR): volatilecontent of glass, fluid phases, + solid precipitations

Microthermometry on fluid phases of melt inclusions

Spectroscopic methods (e.g., Raman) during phasetransitions

useful for:• silicate• carbonatite• (sulfide)

useful for:• silicate• carbonatite

Instrumental techniques

Heating experiments (homogenization): heat melt quench

• high-T stages mounted on petrographic microscopes (direct info on changes)

• furnace technique (no direct observation)

Chemical analysis:

• EMPA (major elements): heated inclusions (solid phases of inclusions)

• SIMS (trace elements): heated inclusions (solid phases of inclusions)

[LA-ICP-MS: unhomogenized inclusions (whole inclusion is ablated)]

[LA-MC-ICP-MS: unhomogenized inclusions (especially on sulfides)]

High temperature(heating experiments)

Homogenization experiments at mantle temperatures

Problems:

volatile content (usually high-p is necessaryfor total homogenization)

post-entrapment crystallization (amount of wallcrystals, sulfide)

useful for:• silicate• carbonatite

• Stage + controller:

• Small ceramic furnace with a hole at the bottom, covered by sapphire, to provide transmitted light for observation during experiment.

• Quartz lid window for observation.

• Gas valves to purge the sample chamber with inert gas.

• Water valves hooked up with a sealed circulating water tank to keep the stage at low T during heating experiment.

High-T heating stage (Linkam)

Purpose of use of the stage: - to study melt inclusions,- to obtain (partially) homogenized melt,- to record melting sequence (crystallization,

identification of phases).

PART-I: Forewords on melts and melt inclusions

PART-II: Method of melt inclusion study, instrumental/analytical techniques

PART-III: Magma drops in olivine, spinel, clinopyroxene, plagioclase andquartz phenocrysts of volcanic rocks (+apatite, zircon)

PART-IV: Silicate melts and melt inclusions as evidences for mantleenrichment, interaction, and immiscibility

Significance of magma drops in ol, sp, cpx, plag, q, zrn, apPetrography

• primary or secondary silicate melt inclusions

• post-entrapment crystallization (not a closed system!)

on the wall

in the inclusion partially or totally recrystallized silicate melt inclusions

• reheating to have trapped melt

Composition of the trapped (primary? primitive?) melt

right composition (should be compared to relevant phase diagram, Frezzotti, 2001)• volatile

bubble (CO2, H2S, CH4, N2)

glass (H2O, Cl, F, S)

Provide information on• change in composition (fractionation, magma mixing)• degassing/partitioning process during crystallization/solidification • immiscibility• post entrapment crystallization

Mafic magma drops in olivine phenocrystsOlivine phenocrysts in basalt (Hungary, Russia, Israel, Korea, etc.) contain silicate melt inclusions (Smi), spinel inclusions (Sp) ±CO2 fluid inclusions

Reflected light

Transmitted light

Phases of silicate melt inclusions (sequence of crystallization):olivine - on the wallsulfide (sulf)Al-spinel (sp)rhöniteclinopyroxene (cpx)apatite(±amphibole)glass (gl, Na- & K-rich )CO2(–rich) bubble

Trapping conditions:>1250 oC, >7 kbars

Mafic magma drops in spinel phenocrysts

Spinel as a host: • early crystallizing phase coexisting with olivine composition of the trapped melt• oxide no reaction with the enclosed silicate melt but post-entrapment crystallization

of Cr-spinel happened

Cr-spinel (micro)phenocrysts in alkali basalt (Albania, Korea, etc.) contain silicate melt inclusions

Trapping conditions: min. 1250 oC

Mafic magma drops in olivine (and spinel) phenocrysts

35 40 45 50 55 60 65 70 750

2

4

6

8

10

12

14

16

Na

2O

+K2O

SiO 2

Andesite

Dacite

Trachyte

Trachy-dacite

Trachy-andesite

Trachy-basalt

TephriteBasanite

Tephri-phonolite

Phonolite

Foidite

glass in unheated smi HTU

glass in unheated smi PK

homogenized smi HTUhost rock HTU

homogenized smi PKhost rock PK

Major element compositions (TAS diagram) of heated silicate melt inclusions (smi) and host basalts (Hungary)

Heating experiment crystallization in smi &fractionation of host basalt

Host basaltbulk rock

Mafic magma drops in olivine (and spinel) phenocrysts

Heated and exposed silicate melt inclusion in olivine for SIMS

0.1

1

10

Ba NbK LaCe Sr P Nd SmEuTiDy Y Yb

Roc

k/O

IB

Sun/McDonough. (1989)

heated smi HTU (1250 °C)

heated smi PK (1250 °C)host basalt HTU

host basalt PK

1

10

100

1000

La Ce Nd Sm Eu Dy Er Yb

Roc

k/C

hond

rite

s

REEs-Nakamura (1974)

heated smi HTU (1250 °C)

heated smi PK (1250 °C)host basalt HTU

host basalt PKTrace element compositions of heated silicate melt inclusions (smi) and host basalts (Hungary)

Trace element distributions of in smi and host basalt pairs:P (apatite), similarities <-> differences (magma mixing)

PART-I: Forewords on melts and melt inclusions

PART-II: Method of melt inclusion study, instrumental/analytical techniques

PART-III: Magma drops in olivine, spinel, clinopyroxene, plagioclase andquartz phenocrysts of volcanic rocks (+apatite, zircon)

PART-IV: Silicate melts and melt inclusions as evidences for mantleenrichment, interaction, and immiscibility

Significance of silicate melts and melt inclusions

Provide information on:

• enrichment of incompatible elements mantle metasomatism (cryptic and modal)

• mantle/melt interaction crystallization process, (modal metasomatism)

• formation of melt partial melting at source region depletion in incompatible

elements at source region (and enrichment of incompatible elements in melts)

• melt immiscibility partitioning of elements, crystallization process

• physical properties of mantle (lattice preferred orientation, elastic feature,

anisotropy

Silicate glasses in mantle rocksThe presence of silicate glasses in mantle rocks always indicate in-situ melting or migration of melts/fluids

Interstitial glass patches

Open-system

Interstitial silicate melt pockets

partial melting (depletion) or metasomatism (enrichment)?

”Closed”-system

Silicate melt inclusion enclosed in mantle minerals

Mantle minerals may trap and preserve the composition of high-pressure-temperature melts, since the large elastic modulus of their host phase prevents them from low-pressure chemical re-equilibration and decompression during ascent/cooling (e.g. Schiano & Bourdon 1999)

lucky case

0.25 cm

OpxOpx

Cpx

CpxIncl

200 m

Q

CO2

Gl

250 mOpx

QzSmi

Petrography: - Smi primary and secondary- Smi: glass and CO2 bubble

Silicate melt inclusions in mantle rock - pyroxenite

Quartz (Qz) and CO2-bearing silicate melt inclusions (Smi) in pyroxenite xenolith, Hungary.

Heating experiments of smi Raman spectroscopy of CO2

Density=0.87-1.18 g/cm3

Entrapment pressure >1.1 GPa

Depth of the present day uppermost mantle

~960 °C melting temperature

Glass composition - major elements:

Glass composition - major elements:

Opx+qz+cpx+amp(?) fractionation from a hybrid melt formed on peridotite-slab-melt interface

Silicate melt inclusion composition (LA-ICP-MS) - trace elements:

Rutile+plagioclase(?)+garnet in the source subducted oceanic crust?

rutileplagioclase?apatite?

garnet

Ni-content in SMI 139-635 ppm; Cr-content in SMI 187-851 ppm reaction with peridotite

Silicate melt inclusions in mantle rocks - peridotite

Primary silicate melt inclusions (smi) in clinopyroxene (cpx) and secondary silicate melt inclusions in orthopyroxene (opx) from lherzolite xenolith (Hungary) Smi phases: products of post-entrainment crystallization, glass (gl), mica, fluid bubble

The same evolved melt(high volatile content)

The same process fractionation (where?)

Raman spectroscopy of fluid bubble in silicate melt inclusion

Cooling experiment

Beside CO2, H2O in peridotite (microthermometry also indicates)