M. Feely1, F. Lindner1, J. George2, J. Parnell3, 24th October 2017 - 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

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

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

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.

Fluid Inclusion Classification Type 2 Type 1 Type 3 Type 3

UV Light Microscopy and Microthermometry Type 2 Type 3 Fracture filled

Confocal Laser Raman Microscopy of Type 2 Fluid Inclusions

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.

P/T Modelling of Quartz Amethyst Crystallization

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

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.

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 Thanks