Applications of Raman microspectroscopy to fluid inclusions phase identification

© 2012 HORIBA Scientific. All rights reserved.

Applications of Raman microspectroscopy to fluid inclusions phase identification.

S. Mamedov *, R. S. Darling**

*Horiba Scientific, Edison, NJ, USA**SUNY Cortland, Cortland, USA


Provide identification of molecules in inclusions such as CO2, CH4, N2, -SH, H2O as an aid to understanding the geochemistry of rock formation as it evolved.

Calibrated relative intensities can provide concentration ratios.

Peak shifts indicate pressure of inclusion. Maps and depth profiles provide insight into the structure of

the inclusion, but are susceptible to artifacts due to the instability in the position of the bubbles.

Information from Raman Spectroscopy of Fluid Inclusions


Experimental Set Up

Laser – 532 nm, 25 mWObjective – Olympus x100, N.A. 0.9Mapping step size – 0.1 microns


Quartz, cristobalite and amorphous SiO2

Raman spectra of SiO2

Intensity

-20

0

20

40

60

80

100

120

140

Inte

nsity

(cps

)

100 200 300 400 500 600 700 800 900 1 000 1 100Raman Shift (cm-1)

696

.0

128

.9

208

.8

264

.7

354

.6

393

.5

465

.4 421

.4

234

.8

491

.3

442

.4

606

.1

803

.8


Image of the box vein cavities (now in the NYS museum collection); Source of photo: Dale, N.C., 1924, The box-vein of Lyonsdale, Lewis County, N.Y., New York State Museum Bulletin 251. The quartz-lined cavities contain the secondary CH4 inclusions we analyzed.

Box vein location in northern NYS. Yellow are Grenville metamorphic & igneous rocks of the Adirondacks, Blue & purple are lower-middle Paleozoic sedimentary rocks.


-40

-30

-20

-10

0

10

20

30

40

Y (µ

m)

-40 -20 0 20 40X (µm)

4 µm

Inclusion 1


Inclusion 1In

tens

ity (c

ps)

200 400 600 800 1 000 1 200 1 400 1 600 1 800 2 000 2 200 2 400 2 600 2 800 3 000 3 200 3 400 3 600 3 800 4 000Raman Shift (cm-1)

306

3.6

127

.3 2

05.4

264

.0

354

.5 3

93.1

401

.5 4

64.4

695

.5

807

.5

992

.3

108

1.2

116

0.5

123

1.2

232

6.5

291

0.8

294

9.7

CH4

N2

SiO2

Raman spectrum in the center of the inclusion. Laser 532 nm, confocal hole 1000 microns = spectrum from full depth of inclusion.


Inclusion 1 – distribution of methane, carbon and SiO2

-40

-30

-20

-10

0

10

20

30

40

Y (µ

m)

-40 -20 0 20 40X (µm)

4 µm

-20

-15

-10

-5

0

5

10

15

Y (µ

m)

-10 0 10 20X (µm)

1 µm1 µm1 µm

Red – CH4

Green – SiO2

Blue - carbon


-40

-30

-20

-10

0

10

20

30

40

Y (µ

m)

-40 -20 0 20 40X (µm)

4 µm

20

40

60

80

100

120

140

160

180

200

Inte

nsity

(cnt

/sec

)

-20 -10 0 10 20 30 40 50Z (µm)

RedGreenBlueRed – CH4

Green – SiO2

Blue - carbon

Inclusion 1 – depth profile in the center


0

200

400

600

800

1 000

1 200

1 400

Inte

nsity

(cnt

/sec

)

1 000 2 000 3 000 4 000 5 000Raman Shift (cm-1)

-40

-30

-20

-10

0

10

20

30

40

Y (µ

m)

-40 -20 0 20 40X (µm)

4 µm

20

40

60

80

100

120

140

160

180

200

Inte

nsity

(cnt

/sec

)-20 -10 0 10 20 30 40 50

Z (µm)

RedGreenBlue

Red – CH4

Green – SiO2

Blue - carbon


0

100

200

300

400

500

600

700

Inte

nsity

(cnt

/sec

)

1 000 2 000 3 000 4 000 5 000Raman Shift (cm-1)

“Second peak” in methane concentration due to the fact that second order line from carbon between 2878 and 2973 cm-1 overlaps with line of CH4 at 2910 cm-1.


Inclusion 1

-40

-30

-20

-10

0

10

20

30

40

Y (µ

m)

-40 -20 0 20 40X (µm)

4 µm

Black dots – photo induced damages due to the interaction of the laser beam with something on the inner surface of the inclusion. Spectral features are the same at high and low power (no damages) and it looks like amorphous carbon.


0

500

1 000

1 500

2 000

2 500

3 000

3 500

Inte

nsity

(cnt

/sec

)

1 000 2 000 3 000 4 000Raman Shift (cm-1)

0

200

400

600

800

1 000

1 200

1 400

1 600

1 800

Inte

nsity

(cnt

/sec

)

1 000 2 000 3 000 4 000Raman Shift (cm-1)

Red – CH4

Green – SiO2

No carbon detected in this inclusion


-40

-30

-20

-10

0

10

20

30

40

Y (µ

m)

-40 -20 0 20 40X (µm)

4 µm 100

200

300

400

500

600

700

800

Inte

nsity

(cnt

/sec

)

-30 -20 -10 0 10 20 30 40Z (µm)

RedGreen


Inte

nsity

(cps

)

500 1 000 1 500 2 000 2 500 3 000 3 500 4 000Raman Shift (cm-1)

511

.1

120

.3 2

01.0

259

.0 3

53.3

402

.5 4

62.2

806

.5

107

9.3

138

0.3

115

8.3

127

6.0

698

.2 344

4.0

324

6.9

Inclusion 2

-40

-30

-20

-10

0

10

20

30

40

Y (µ

m)

-40 -20 0 20 40X (µm)

4 µm

Inclusion contains water


Inclusion 3

-40

-30

-20

-10

0

10

20

30

40

Y (µ

m)

-40 -20 0 20 40X (µm)

4 µm


0

500

1 000

1 500

2 000

2 500

3 000

Inte

nsity

(cnt

/sec

)

1 000 2 000 3 000 4 000Raman Shift (cm-1)0

200

400

600

800

1 000

Inte

nsity

(cnt

/sec

)

1 000 2 000 3 000 4 000Raman Shift (cm-1)

Red – CH4

Green – SiO2

No carbon detected in this inclusion


50

100

150

200

250

300

350

400

Inte

nsity

(cnt

/sec

)

-30 -20 -10 0 10 20 30 40Z (µm)

RedGreen-40

-30

-20

-10

0

10

20

30

40

Y (µ

m)

-40 -20 0 20 40X (µm)

4 µm


Homogenization Temperatures

The two inclusions on which Raman data obtained show up lowering the Th measurements. Inclusions not probed with the laser give a uniform Th of -82.5C to -82.6C.

1 3


Raman spectroscopy is a practical exploration tool to study geological materials including fluid inclusions.With its high spatial resolution, Raman spectroscopy is very useful to determine the composition of the embedded fluids and gas phase.Imaging of fluid inclusion allows obtain information about distribution of liquid and gas phase and detect thin layer of water or carbon on the surface.Light induced changes are observed in some inclusionsInclusions on which Raman spectra obtained show lowering in Th (-85.7C and -94.7 C) but inclusions not probed with the laser give a uniform Th of -82.5C to -82.6C. It was found that there is a shift of 2914 cm-1 band of CH4 to 2910.8 cm-1 which can be explained by high pressure in the inclusion.

Summary


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Applications of Raman microspectroscopy to fluid inclusions phase identification