1. M. Feely1, F. Lindner1, J. George2, J. Parnell3,
24th October Seattle, USA
Using fluid inclusion studies to investigate the source of hydrocarbon fluids in the Miocene Snoqualmie Granite, North Cascades, WA, USA
Alessandra Costanzo1
M. Feely1, F. Lindner1, J. George2, J. Parnell3,
S. Bowden3, M. Baba3 P. Owens4
1GeoFluids Research Group, National University of Ireland Galway
2Cascade Scepters, Maple Valley, WA, USA
3Geofluids Group, School of Geosciences, University of Aberdeen, UK
4Centre for Microscopy & Imaging, National University of Ireland Galway

2. Snoqualmie Granodiorite
Geological Setting
Green Ridge Breccia
Snoqualmie Granodiorite
Quartz Monzonites
Gabbros and Diorite
10km

4. Amber Oil-bearing Inclusions
1 cm
0.5cm
Oil inclusions in amethyst, North Cascades Range, Washington State.

5. Fluid Inclusion Petrography of Quartz Euhedra
Type 1 - Liquid-rich two-phase (L+V) aqueous inc.
Type 2 - Black solid-bearing two-phase (L+S) inc.
Type 3 - Amber oil-bearing two-phase (Loil+Laq) inc.

6. Fluid Inclusion Classification
Type 2
Type 1
Type 3
Type 3

7. UV Light Microscopy and Microthermometry
Type 2
Type 3
Fracture filled

8. Confocal Laser Raman Microscopy of Type 2 Fluid Inclusions

9. Gas Chromatography-Mass Spectrometry
Green Ridge Breccia
Portion of m/z 191 chromatogram from extract of amber coloured oil, showing distribution of hopanes.
Portion of m/z 217 and 218 chromatograms from extract of oil, showing distribution of steranes.
Ternary plot of relative proportions of C27, C28 and C29 steranes in the oil sample.

10. P/T Modelling of Quartz Amethyst Crystallization

11. How did the hydrocarbon fluid enter the amethyst in the Green Ridge Breccia?
(Adapted from Chitwood, 1976)

12. Summary of Findings Three different FI types:
Type 1 primary aqueous inclusions
Type 2 and 3 hydrocarbon inclusions
Type 2 oil composition is mainly bitumen;
Type 3 oil composition consists of hopanes and steranes (terrestrial/lacustrine environment);
links are made between the oil generation and the fossil-rich shales and mudstones of the Guye Sedimentary Member of the Naches Fm.;
tectonothermal events are invoked to generate the hydrocarbon and to transport it into the Green Ridge Breccia.

13. Costanzo, Feely, Linder, George, Parnell, Bowden, Baba, Owens
Using fluid inclusion studies to investigate the source of hydrocarbon fluids in the Miocene Snoqualmie Granite, North Cascades, WA, USA
Costanzo, Feely, Linder, George, Parnell, Bowden, Baba, Owens
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