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  • Hernan Ugalde – Geological Modeling of Geophysical Data: Beyond the 3D inversion black box, v2.0

Hernan Ugalde – Geological Modeling of Geophysical Data: Beyond the 3D inversion black box, v2.0

  • 11 Sep 2012
  • 4:00 PM - 5:00 PM
  • OBA Conference Centre, Conference Room C&D, Suite 200, 20 Toronto Street in Toronto

Hernan Ugalde, Senior Geophysicist Consultant, Paterson, Grant & Watson Limited will give a presentation on

Geological Modeling of Geophysical Data: Beyond the 3D inversion black box, v2.0

Download the TGDG presentation here

Over the past 5-10 years and in parallel with the advent of faster and more powerful computers and 3D inversion algorithms, 3D inversion of geophysical data has recently become the ultimate modelling and interpretation target tool for many exploration mining companies. The same applies to semi-automatic interpretation routines: we have many new tools that provide the user with various different views or different aspects of the data. Thus, while we are able to generate many different views of the data, not enough time is spent thinking on which information is of interest to the exploration program. Do we just drill on the “big purple anomaly”? Or should we rather stop and think about the mineralization-rich alteration zone that has destroyed magnetite and therefore is situated next to the big mag anomaly? What is the nature of the exploration target being sought, and which aspect of that target is amenable to geophysical detection and modeling?

Based on the scale of the problem and the availability of a-priori geological information, 3D inversion might not be the more efficient way to model the data. Instead, the combined use of simple tools like 3-point solutions of topographic data combined with edge detection routines from geophysical data (SED, CET) can provide with a wealth of strike and dip information that can be used in the construction of a preliminary geological model. Similarly, simple single-anomaly inversion algorithms can provide with first order estimates of depth to top and dip of the magnetic/gravimetric sources. This preliminary geological model can further be incorporated as first-order information into the input mesh for a 3D constrained inversion scenario.

“Old” tools like 2D/2.5D modelling of profile-based data and the inversion of single-anomalies using simple geometries are not so interesting anymore and they are often disregarded as unexciting, or dull when compared to 3D cubes of data. Yet 2D tools impose parameters that have more geological meaning; for example a dipping slab must have parallel sides just like a lithological unit. For more regional problems, 2D-2.5D sections have the advantage of being easier to handle and giving the user full control of the modelled geology.

On this talk we will review case studies from Bathurst Mining Camp, NB; an hematite-rich iron exploration project in NWT and other cases where a geological forward modelling approach made the difference.

Hernan Ugalde obtained a BSc and MSc in Geophysics at University of Chile in Santiago. After 3 years at the Geological Survey of Chile (Sernageomin) he joined Paterson, Grant & Watson Limited’s Santiago office in 1997. In 2001 he moved to Canada to pursue a Ph.D. at University of Toronto. He obtained his PhD in Geophysics in 2006. Then he went to McMaster University as a postdoc/research scientist from 2006-2011, where he worked mostly in Bathurst, NB, Sudbury, ON and Newfoundland while keeping his links to PGW as a part-time consulting geophysicist. In 2011 he returned full time to PGW, where he has been doing processing, interpretation and modelling of geophysical data with geological tendencies.

When: Tuesday September 11, 2012, 4–5 pm followed by networking and refreshments immediately afterward

Where: Meeting at the OBA Conference Centre, Conference Room C&D, Suite 200, 20 Toronto Street in Toronto. Refreshments sponsored by PGW Consultants afterward at the Metropolitan Restaurant Bar, 20 Victoria Street, Toronto.

Admission Cost: free for TGDG Members and students.

New memberships: New annual TGDG memberships for the 2012-2013 season will be available at the meeting for $25, the same low, low price as last year.

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