Thunder Bay Regional Meeting hosted by the Association of Professional Geoscientists of Ontario.

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The Department of Geology presents

IAN R. DASTI
Master of Science in Geology Thesis Defense

"The Geochemistry and Petrogenesis of the Ni-Cu-PGE Shakespeare Deposit, Ontario, Canada"

Friday, March 7, 2014
2:30 pm
CB 3031

45th Annual Symposition - Friday January 31st

THE DEPARTMENT OF GEOLOGY

THESIS SEMINARS 2013-2014
PROGRESS REPORTS

AYAT BAIG
"Characterisation of the alteration halo around MAX Mo porphyry using trace element geochemistry"

BENJAMIN KUZMICH
"A progress report on the petrogenesis of the gabbroic intrusions and their associated Fe-Ti-V mineralisation within the McFaulds greenstone belt, Superior Province, Northern Ontario, Canada"

Thursday, November 28, 2013
at 2:00 p.m. in CB 3031

GEOLOGY DEPARTMENT SEMINAR SERIES
Canadian Society of Exploration Geophysicists
2014 Distinguished Lecture Tour

BERND MILKEREIT
Teck Chair of Exploration Geophysics, Department of Earth Sciencess
University of Toronto

"Seismic Imaging in the Presence of Strong Contrasts - How forgetful are
seismic waves?"

Thursday, November 21, 2013
at 2:00 p.m. in CB 3031

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Seismic imaging is an important geophysical tool for delineating and monitoring the earth’s subsurface structure and its oil, gas and mineral resources. Owing to the earth’s heterogeneity, such subsurface structures exist at different scales (sizes) with lateral and vertical variations in physical properties such as contrasts in bulk and shear moduli, and densities. Over the past decade, seismology entered a new era. Solving elastic and visco-elastic wave equations on large supercomputers, accurate and complete simulations for heterogeneous 3D earth models became a reality – replacing exact solutions for layered earth models. Seismic methods illuminate subsurface structures using compressional and shear waves. Recorded signal at surface and borehole seismic sensor locations arise from reflection, refraction, transmission, scattering and attenuation of elastic waves at lithological contacts, structural boundaries and the Earth's free surface, where abrupt and gradual changes in physical rock properties occur. The effects of heterogeneities on seismic wave propagation can be described in terms of different propagation regimes and physical rock property contrasts: quasi-homogeneous for heterogeneities too small to be seen by seismic waves, Rayleigh scattering, Mie scattering and small-angle scattering. These scattering regimes cause characteristic amplitude, phase and travel time fluctuations. After a few time steps, however, the transmitted and forward scattered seismic wave fields “heal”, thus limiting the resolving power of seismic imaging. Examples of strong constrasts include the Earth’s free surface, seafloor topography, permafrost layers, gas and gas hydrate accumulations, and massive sulfide mineral deposits. Consequently, the presence of strong contrast provides an interesting challenge for a wide range of controlled source seismic imaging and passive source seismic monitoring studies. A modeling study of elastic seismic wave propagation through an underground mine with low velocity and low density backfill illustrates lateral amplitude, travel time and phase variations.

BIOGRAPHY:
Bernd Milkereit is the Teck Chair of Exploration Geophysics at the Department of Earth Sciences of the University of Toronto (since 2001).  For more than 30 years, Bernd has worked at the intersection between mineral resources and exploration seismology. He carried out research projects on coal and groundwater before moving into hardrock seismic imaging and exploration for deep mineral deposits in the crystalline crust. He maintains a strong interest in international scientific drilling projects.  Previous to his current position Bernd was a research scientist the Geological Survey of Canada (1985-1996) and professor of geophysics at Kiel University, Germany (1996-2001).

GEOLOGY DEPARTMENT SEMINAR SERIES

Geological Association of Canada
2013-2014 Howard Street Robinson Lecturer:

DR. JACOB HANLEY
Department of Geology, Saint Mary’s University, Halifax, Nova Scotia

"The origin and role of volatiles in the formation of magmatic Ni-Cu-platinum-group element deposits:  What have we learned from fluid and melt inclusions?"

Thursday, November 7, 2013
at 2:00 p.m.
in CB 3031

Fluid and melt inclusions trapped in mineral crystals can provide a record of the physical and chemical conditions at the time that ore metals were transported by fluids and magmas, and in some cases, can constrain the actual conditions of deposit formation in magmatic-hydrothermal ore systems. Fluid and melt inclusions are preserved within pegmatite bodies and cumulus minerals within mafic-ultramafic layered intrusions that host economic concentrations of the platinum-group elements (‘PGE’) (e.g., Bushveld Complex, South Africa; Stillwater Complex, Montana). In the majority of these intrusions, the earliest volatile phase to have exsolved from the crystallizing intrusions was a relatively anhydrous carbonic fluid (CO₂-dominated). As crystallization proceeded, volatiles appear to have become increasingly water-rich and saline, consistent with the relative saturation limits of carbonic and aqueous fluids in mafic silicate liquids.

The latest stage volatiles in the layered intrusions were unusual halide melts (only slightly hydrous molten salts) of relatively simply composition (NaCl±KCl, CaCl₂) with salinities in excess of 90 wt% eq. NaCl or CaCl₂. These volatiles were trapped at minimum temperatures of ~750-800^oC, near the eutectic temperature for water-saturated felsic (late, intercumulate) liquid. Heterogeneous entrapment of late-stage silicate melt and halide melt provides unambiguous evidence for the coexistence of both phases. However, experimental constraints on the nature of exsolved volatiles from mafic silicate liquids suggest that the halide melt phases cannot represent an exsolved phase from that coexisting silicate liquid, since this would require unrealistically high (initial) Cl:H₂O ratios for the parental silicate liquid. Analysis of rhyodacitic silicate melt inclusions that coexist with the halide melt inclusions show that the coevally-trapped silicate melt had low Cl:H₂O ratios, as expected from experimentally constrained volatile solubilities. Similarly, the salt melt phases could not have evolved via the crystallization of hydrous magmatic minerals (e.g., biotite, apatite) since their abundances in the intrusions are very low.

The most plausible explanation for the halide melt phases involves the “dehydration” of an initially lower salinity aqueous fluid. This may have occurred by the reaction of the aqueous fluid with nominally-anhydrous minerals such as pyroxene, or by the late-stage alteration of cumulus minerals to hydrous mineral assemblages. Through the use of conventional hydrothermal experimental techniques, it can be shown that the reaction of a volumetrically-minor CaCl₂-rich aqueous fluid (20 wt% eq. CaCl₂) with the assemblage diopside-enstatite-quartz at near-solidus conditions (700^oC, 0.4 kbar) results in the formation of tremolite by the reaction of H₂O with the initially anhydrous mafic mineral assemblage. The resulting salinity of the saline phase, trapped as synthetic inclusions in quartz, was > 96 wt% eq. CaCl₂, consistent with the water-poor nature of the salt melt inclusions observed in most layered intrusions globally.

In-situ analyses of these inclusions by laser ablation ICP-MS show that they transported precious metals, including the PGE and, therefore, must be considered potentially responsible for modifying the metal concentration of primary igneous silicate and sulfide liquids prior to the formation of magmatic ore deposits, or remobilizing the precious metals at near-solidus to post-solidus conditions.

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GEOLOGY DEPARTMENT SEMINAR SERIES

Presentation by guest speakers:

SEAMUS MAGNUS
Precambrian Geoscientist, Ontario Geological Survey, Sudbury ON

and

VICTORIA LEE
Aggregate Resource Geologist, Ontario Geological Survey, Sudbury ON

"Ontario Geological Survey (OGS) Summer 2014 Field Assistant Recruitment"

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Thursday, November 14, 2013
at 2:00 p.m.
in CB 3031

GEOLOGY DEPARTMENT SEMINAR SERIES

Presents a seminar by:
ANDREW CHEATLE, P. Geo.
President, Association of Professional Geoscientists of Ontario

"Introduction to the Association of Professional Geoscientists
of Ontario"

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Thursday, October 17, 2013
at 2:00 p.m.
in CB 3031

GEOLOGY DEPARTMENT SEMINAR SERIES

Presents a seminar by:
DR. STEPHEN KISSIN
Professor Emeritus, Geology Department
Lakehead University

"Canadian meteorites - an update on meteorites recovered in my time at
Lakehead University"

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Thursday, October 10, 2013
at 2:00 p.m.
in CB 3031
Coffee and cookies provided