A short course on the why, how, and what of geophysical inversion

Presented by the B.C. Geophysical Society

Date: April 24th – 26th 2013

Address: SFU Downtown Campus; Vancouver BC

Registration:  Registration is now open!  Please fill out attached pdf form (link below) and click submit.  Registration will be complete once payment is made via Paypal link.  Delegates are asked to choose one workshop day among April 25th or 26th.

Day 1 – Presentations

Introduction to inversion in exploration

• Reasons for doing inversion
• Range of inversion options: magnetics, gravity, EM, IP-resistivity, seismic
• Fitting geology and data

 Background on inversion

• Unconstrained/constrained
• Joint and collaborative
• The future of inversion

Before inversion – forward modeling

• forward modeling
• petrophysics drives the story
• complexity vs. adequacy 

Case studies

• Potential fields
• EM
• IP-resistivity

Day 2 – Workshop with Case Studies
Multi-disciplinary teams will use geological, geophysical and geochemical data from two deposits (Babine Lake porphyry Cu-Mo, BC and Minto Cu, YK) to develop exploration targets. Teams will present their evaluations of the data to stimulate group discussion.

Inversion results for the available geophysical surveys will be presented to demonstrate state-of-the-art technology (http://geosoft.com/, http://www.mirageoscience.com/) and best practices.

 The BCGS would like to thank RedTail Metals and Capstone Mining Corp. for providing access to the Babine Lake and Minto data sets.

Where: Chairman Room – Westin Bayshore Hotel, 1601 Bayshore Drive Vancouver

When: 7:30 am – Tuesday, January 29th, 2013.

Registration: Sold out

Speaker: James Siddorn
                 Practice Leader (Structural Geology) for SRK Consulting, Toronto

Topic/Abstract: “Advanced Geological Interpretation of Aeromagnetic Data: Applied Indirect Exploration Targeting”

Aeromagnetic surveys are a widely recognized exploration technique in mineral exploration especially in covered terranes. They are often not used to their full potential, with direct anomaly targeting and lineament analyses conducted but little else. The real value in aeromagnetic data can be unlocked integrating multiple datasets into the interpretation of the data with the aim to produce a coherent geological map which outlines the structural and geological history.

Geological models are a primary component of the interpretation process; in order to present an interpretation of the geology of the region there needs to be a coherent framework of stratigraphic and structural principles that form the basis of the interpretation. Individual rock unit and structural elements identified on the aeromagnetic images can then be related to components of the geological models. Individual structures can be interpreted in both a time and space context, with an outline of when and how faults moved. In turn, the spatial distribution of mineral deposits in relation to structures becomes evident and can be related to the geological evolution of the region, not just the geometry.

Advanced aeromagnetic interpretations should produce structural/geological maps showing the relative timing of structural events with a focus on commodity specific exploration targeting. This talk will outline an interpretation method with examples of final products for a series of geological terranes.

SPEAKER: Justin Granek (MSc)

TITLE: Computing Geologically Consistent Models from Geophysical Data

DATE: Wednesday, November 28th 2012

TIME: 4:30pm

LOCATION: Room 451, 409 Granville (UK Building at Granville and Hastings)

ABSTRACT: The difficulty of finding economically viable mineral deposits has motivated the development of new exploration methodologies. This has led to greater efforts from the geophysical community to incorporate available sources of geological and geophysical information. Since the suite of available data types is diverse, the synthesis of multiple sources of information into a single coherent model can present many difficulties. In particular, the incorporation of geological constraints in the inversion of geophysical data has been investigated by various researchers.

While valuable information can be gleaned from geological data, a challenge remains due to the disconnect between geological units and geophysical property values. Though descriptive, a distinct geological unit is not always able to uniquely characterize the physical properties of a volume of earth, and vice versa. Interpretation and translation to and from geological and geophysical units can introduce bias based on the expert’s experience.

Current methodologies which exist to incorporate geological and geophysical information into inversion typically suffer from at least one of the following issues: either they require the user to interpret physical property values from geological information, or else they require the user to define some range of influence for each measurement in the model. Imposing constraints on a model which are biased in one of these ways can lead to recovered models unsupported by the data.

The introduced methodology differs from previous attempts at incorporation of a priori information since it applies statistical classification of in situ physical property measurements (as opposed to physical property values inferred from geology) as the basis for constraints. Statistical classification, combined with the iterative nature of the scheme, act to propagate the information from the downhole physical property logs through-out the model with minimum user input required. This automated approach reduces the potential for bias from unsupported constraints, while maximizing the integration of the classification results.