fluidincbis

8/10/2019 fluidincbis

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An animated introduction to fluidinclusions

by

A H RankinSchool of Earth Sciences and Geography

Kingston University, Surrey KT1 2EE

http://www.kingston.ac.uk/esg/facilities/fluidinc.ppt


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The following slides illustrate how primary(P) and secondary (S) inclusions developduring crystal growth and healing ofsecondary fractures

Aqueous solution

Crystal

Some animation has been added

To see changes hit return


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Formation of Primary and

Secondary inclusions

primary inclusions form during

primary crystal growth often alonggrowth zones

secondary inclusions form after primary growth, usually alonghealed micro-fractures


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P

S


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Inclusions formed from trapping of

homogeneous aqueous fluid will developvapour bubbles on cooling due to differentialthermal contraction of fluid and host mineral.

The next slide shows groups of two phase(vapour- liquid) primary and secondaryinclusions with distinctly different vapour-

liquid ratios, indicative of different PTtrapping conditions


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Contraction vapour bubbles


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25oC

0oC

Vapor

Liquido


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The next slides show more complex aqueousinclusions with daughter minerals, liquidcarbon dioxide and liquid hydrocarbons (oil)


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Multiphase inclusion with daughterand/or captive minerals

Chalcopyrite halite


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The halite daughter mineral indicates high salinities (above26 wt.%) which may be estimated from the solutiontemperature of halite.

The chalcopyrite crystal here is either a captive or truedaughter phase. But such opaque minerals are reluctant todissolve even if they are true daughters


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CO 2-rich aqueous inclusion

CO 2 vapour CO 2 Liquid


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Liquid CO 2 will only be seen in the inclusion below the critical point of CO 2 (31 oC).

On cooling the CO 2 will react with water toform clathrates (ice like compounds).

On more rapid cooling solid CO 2 will form. If pure, melting will occur at the triple point of

CO 2 (-56.6o

C). If other volatiles, e.g. nitrogenor methane, are present the meltingtemperature will be lowered


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Oil-water inclusion

Vapour Oil


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Liquid petroleum may be identified as an immiscible phasewithin an inclusion, by its brownish colour or UVfluorescence (as shown in the next slide)


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The following slides show the homogenisation

of liquid and vapour in a two phase aqueousinclusion during laboratory heating. Thetemperature at which this occurs is the

Homogenisation temperature (Th) The bubblereturns on cooling.Heating

Cooling


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

0oC

-100 oC

Temperature of Homogenisation Th


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

-100 oC

0oC


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350 oC

25oC

0oC

-100 oCFreezing after Supercooling


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

0oC

-100 oC


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350 oC

25oC

0oC

-100 oCLast ice melting temperature Tm(ice)


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The next slides illustrate the use of heating and freezing datafor simple two phase aqueous inclusions.

Heating and freezing data (Th, Tfm, Tmice) are interpreted in

terms of the simple H 2O and NaCl-H 2O systems


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Principle of fluid inclusion geothermometry

PVT diagram for pure water 1.0

0.5

0

50 150 350

Isochore(g/cc)

Critical point

Liquid

Vapour


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Consider an inclusion trapped at a giventemperature and pressure (Tt, Pt)

1.0

0.5

0

50 150 350 Tt

PtIsochore(g/cc)

Critical point

Liquid

Vapour


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Beyond this point the inclusion cools alongthe L=V curve and a vapour bubble nucleates

1.0

0.5

0

50 150 350 Tt

PtIsochore(g/cc)

Critical point

Liquid

Vapour


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Continued cooling results in further shrinkageof liquid and growth of the vapour bubble

1.0

0.5

0

50 150 350 Tt

PtIsochore(g/cc)

Critical point

Liquid

Vapour


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On heating along the V/L curve, the liquidexpands and the bubble shrinks

1.0

0.5

0

50 150 350 Tt

PtIsochore(g/cc)

Critical point

Liquid

Vapour


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Until the bubble disappears at the

homogenisation temperature (Th) 1.0

0.5

0

50 150 350 Th Tt

PtIsochore(g/cc)

Critical point

Liquid

Vapour


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The point Th uniquely defines the isochorealong which the inclusions originally cooled1.0

0.5

0

50 150 350 Th Tt

PtIsochore(g/cc)

Critical point

Liquid

Vapour


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With continued heating the inclusion followsthe original isochore

1.0

0.5

0

50 150 350 Th Tt

PtIsochore(g/cc)

Critical point

Liquid

Vapour


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The difference between Th and Tt is known asthe Pressure Correction

1.0

0.5

0

50 150 350 Th Tt

PtIsochore(g/cc)

Critical point

Liquid

Vapour


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The bubble reappears on cooling and Th can be re-determined

1.0

0.5

0

50 150 350 Th Tt

PtIsochore(g/cc)

Critical point

Liquid

Vapour

Phase diagram for NaCl-H2O showing stability


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0.1 oC

-20.8 oC

Ice + NaCl.2H 2O + V

Ice + L+ V

L + V NaCl+L+V

NaCl.2H 2O+L+ V

Weight % NaCl

T e m p e r a t u r e

o C

-50

25

-25

0

3020100

Phase diagram for NaCl H2O showing stabilityfields for halite, hydrohalite, liquid and vapour

An inclusion with 10 wt.% solution cooled below


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0.1 oC

-20.8 oC


Ice + L+ V

L + V NaCl+L+V

NaCl.2H 2O+L+ V

Weight % NaCl


o C

-50

25

-25

0

3020100

An inclusion with 10 wt.% solution cooled below0oC does not form ice because of metastability

Rapid cooling below the eutectic temperature (Te)


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0.1 oC

-20.8 oC


Ice + L+ V

L + V NaCl+L+V

NaCl.2H 2O+L+ V

Weight % NaCl


o C

-50

25

-25

0

3020100

ap d coo g be ow t e eutect c te pe atu e ( e)is usually needed before the inclusion freezes

On heating first melting (Tfm) occurs at -20.8


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0.1 oC

-20.8 oC


Ice + L+ V

L + V NaCl+L+V

NaCl.2H 2O+L+ VTfm

Weight % NaCl


o C

-50

25

-25

0

3020100

g g ( )(Te), evident by unlocking of the vapour bubble

Continued heating results in the melting of the last


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0.1 oC

-20.8 oC


Ice + L+ V

L + V NaCl+L+V

NaCl.2H 2O+L+ VTfm

Weight % NaCl


o C

-50

25

-25

0

Tm (ice)

3020100

g gice crystal (Tm_ice) at -6 oC

Continued heating results in the melting of the last


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0.1 oC

-20.8 oC


Ice + L+ V

L + V NaCl+L+V

NaCl.2H 2O+L+ VTfm

Weight % NaCl


o C

-50

25

-25

0

Tm (ice)

3020100

g gice crystal (Tm_ice) at -6 oC

Principle of fl id incl sion geothermometr


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Principle of fluid inclusion geothermometry

based on PVT diagram for pure water 1.0

0.5

0

PtIsochore(g/cc)

Critical point

Liquid

Vapour

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