ACT - A new magnetic tensor approach to mapping magnetic rock properties and cover depth using AI

Title : A new magnetic tensor approach to mapping magnetic rock properties and cover depth using AI

Date : 12th of November, Drinks and food from 4:30 for a 5pm start.

Presenter : David Pratt, Manager Research & Development, Tensor Research.

Location : Geoscience Australia, Scrivener Room.

Abstract

The presentation covers the use of an expert system AI method applied to magnetic gradient tensor data for mapping depth of cover and formation properties as a constrained 3D geological problem. The constraint takes advantage of an often, overlooked fact that the basement unconformity surface dominates the magnetic response measured in conventional airborne magnetic surveys. This dominance allows us to recover the rock properties and depth of the formations that are truncated by the basement unconformity. Recovery of rock property information from airborne surveys gives us the opportunity to look at old data with new eyes for the stones that were never turned.

Exploration under cover is very important to the discovery of new resources to replace existing mines as old resources are depleted. The magnetic method has evolved into an important tool for understanding the subsurface geology and location of favourable environments suitable for the emplacement of a broad range of economic minerals. A large part of the value is derived from qualitative interpretation of the spatial relationships and mapping of the inferred geology. However, much valuable information about the rock properties and cover depth is never recovered from the survey data.

Advances in the understanding of geologically constrained processing of the survey data along with rapid improvements in data quality and reduced line spacing promises to deliver higher resolution information on magnetic properties. Improved estimation of magnetic susceptibility provides guidance on the possible range of rock types associated with individual magnetic anomalies.

Magnetic remanence, often considered as inconvenient for interpretation, is an important indicator of a geological event, which in some cases may be associated with a mineralising process. We can now recover subtle magnetisation information indicative of magnetic remanence that is essentially invisible in a magnetic image. In many cases, subtle remanence events are lost in the low contrast blue areas of an image, yet these may contain clues to mineralising events.

About the speaker:

Manager Research & Development, Tensor Research. He holds a B.Sc. (Hons) and M.Sc. from the University of Sydney in Geology and Geophysics and a Ph.D. in Physics from the University of Newcastle. His early career started with the NSW Geological Survey, and then he worked as a geophysical consultant until 1984 when he co-founded Encom Technology. He was Managing Director from 2001 until it was acquired by Pitney Bowes Software in 2007. In 2010 he started Tensor Research with two colleagues to focus on advanced potential field research. He received the ASEG’s Grahame Sands Award in 2010 and Laric Hawkins Award in 2013.