Leapfrog’s structural trend

By Peter Joynt

It is not often in geology that mineralisation or geological units behave in a consistent planar fashion. The earlier article on interpolation and anisotropy by Kirk Spragg outlined a detailed explanation of Leapfrog’s global trend and how it affects the interpolation of points. This article aims to give users an introduction to the application of structural trends and how they can be applied to a model to handle different situations.

What is a Structural Trend?

A structural trend is a generalisation of the global trend that allows changes in direction of continuity over a defined surface. Instead of being based on a plane like the global trend with the user defining the ellipsoid ratios, the structural trend is based on a surface. This surface can be any shape or orientation usually defined by geological constraints such as faulting, foliation etc. The surface is then effectively down sampled to determine the local trend at each point on the mesh to give the user an anisotropy that varies throughout the defined space. This makes the structural trend perfect for geological units or mineralisation that is not planar. The structural trend does not determine the final surface; this is still done by the interpolant and the data points used. In Leapfrog the default interpolant type is isotropic, which lets us more easily visualise trends that are often hard to pick up when looking at raw data. Figures 1, 2 and 3 show the difference between an isotropic interpolant, global trend and a structural trend.

Isotropic interpolant modeled in Leapgfrog software.

Figure 1: Isotropic interpolant

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New Zealand: the shaky isles

By Sam Bain

New Zealand has a lot of earthquakes. Many of you will have heard of the recent deadly Christchurch earthquake sequence. Some of you may know about the relatively large earthquake sequence that occurred near Seddon, a small town to the south of Wellington, New Zealand’s capital, in 2013. Perhaps those strange types out there with a passion for seismology might have noticed the relatively common occurrence of medium to large earthquakes near New Zealand on the USGS earthquake map. They might not realise that in a typical month New Zealand experiences approx. 3000 earthquakes (I am cheating a bit here as around one third of these are too small to be felt). On average, New Zealanders felt 414 earthquakes larger than magnitude 4 each year from 1960 to 2011.

New Zealand Earthquake Map

Map showing earthquakes throughout New Zealand over the last year. The categorisation by colour refers to the intensity of the shaking experienced from the earthquakes. The shaking intensity is largely controlled by the earthquake magnitude and location relative to the person being shaken (especially depth). For clarity, the huge number of weak earthquakes have not been shown. Image from GNS Science Geonet website .

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Getting a handle on complex geology

By Desmond Subramani

South Deep Mine has some complex geology, it is located near Westonaria, around 50km from Johannesburg, South Africa. The mine is regarded as a “flagship ore reserve”, but it hasn’t always been that way. Historical complications and the complex nature of the location has meant years of work to understand the geology. Leapfrog Geo has been an important aspect in improving the geological models within the mine’s geological team. This post highlights some of the challenges and how Leapfrog Geo proved to be a useful solution.

The Geologists of South Deep and leapfrog gathered outside the offices at South Deep’s Twin Shaft.

The Geologists of South Deep and leapfrog gathered outside the offices at South Deep’s Twin Shaft.

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Building a geological model – Part 3 of 3

By Andrew Cantwell

Creating a first pass interpolant

This video continues on from part 2 of building a geological model in Leapfrog.

The process outlined in this video is simplified – the idea of this blog post is to give an understanding of the speed and ease of creating a first pass interpolant which can then be refined to give a more reasonable model.

You won’t hear any narration in this video but captions have been provided to explain the basic steps. If you’re after a more detailed description of the model building process then please contact your local support team.

We recommend you view this video in full screen mode. It may take approximately 30 seconds after you press play to switch to High Definition (given your internet connection allows it).

The main steps in this video include:

  • Viewing the assay data
  • Using some of the visualisation options to gain a basic understanding of the trend
  • Creating an interpolant model
  • Adjusting some basic parameters to get a more realistic model.

If you missed the previous videos in the model building series you can view Part 1 or Part 2 on this blog.

 

Further reading:
Case Study – can implicit modelling be used to model complex geology.

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New Zealand geology: a brief overview

By Sam Bain

When geologists visit the Leapfrog offices they often end up chatting with our geo’s about the spectacular geology that can be found here in New Zealand. We can usually recommend some interesting outcrops to visit when travelling our country. Today I thought I would try to give an overview of this geology. Given the tectonic complexity of this area, it will be a very simplified description but hopefully it will provide a starting point for those who are interested. In the long term I hope to look in more detail at some specific sites.

New Zealand is a section of Zealandia, a much larger submerged continental landmass. Zealandia extends a significant distance east into the Pacific Ocean and south towards Antarctica. It also extends towards Australia in the north-west. This submerged continent is dotted with topographic highs that sometimes form islands. Some of these, such as the main islands (North and South), Stewart Island, and the Chatham Islands, are settled. Other smaller islands are eco-sanctuaries with carefully controlled access.

The submerged landmass of Zealandia

The submerged landmass of Zealandia

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Building a geological model – Part 2 of 3

By Andrew Cantwell

This video continues on from part 1 of building a geological model in Leapfrog.

You won’t hear any narration in this video but captions have been provided to explain the basic steps. If you’re after a more detailed description of the model building process then please contact your local support team.

We recommend you view this video in full screen mode. It may take approximately 30 seconds after you press play to switch to High Definition (given your internet connection allows it)

The main steps in this video on building a geological model include:

  • How to create a new geological model
  • Creating depositional surfaces
  • Editing a surface using a polyline
  • Activating surfaces to produce volumes
  • Creating dykes
  • Editing interval selections
  • Adjusting the chronological order of the surfaces
  • Creating intrusions

If you missed part 1 you can view the post here

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Video: Importing and manipulating data – Building a geological model in Leapfrog Geo – Part 1 of 3

By Andrew Cantwell

This video provides a short and simple introduction to importing data into Leapfrog, as well as manipulating the data to make it easier to model. It is the first video in a series of 3 that will be posted on our blog over the next couple of weeks. The video provides captions to explain the basic steps but does not include any narration or detailed description of the entire model building process which is covered in Leapfrog Geo Fundamentals training.

The main steps in this video about importing and manipulating the data include:

  • Importing drillholes
  • Selecting columns for import
  • Fixing errors in the drilling
  • Importing the topography points
  • Creating a topography & adjusting the resolution
  • Simplifying the geology by creating a grouped column
  • Using the interval selection tool to select intervals which can be split up

Part 2 of this video series is available here

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Grade shells vs. mineralised zones

By Lisa Swinnard

There is more than one way to create a boundary surrounding a cut-off grade in Leapfrog; however the different techniques used to create these boundaries rely on different underlying concepts. Which tool to select will depend on the ultimate purpose for building the boundaries.

The typical way to create these boundaries is by building grade shells using the Interpolant tool in Leapfrog. Interpolated grade shells are built by using the known drillhole or point data to interpolate values infinitely across the boundary extents; isosurfaces (grade shells) are then created to link up identical values. Grade shells created by interpolation represent a “soft boundary”, as it is not possible to snap these isosurfaces (grade shells) to contact points on drillholes. Grade shells created using interpolation are ideal tools for exploration drillhole targeting.

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The risk of megathrust generated tsunamis

By Sam Bain

Natural disasters are often staggering in their scale, but few can compare to the shocking extent of damage and life loss resulting from the 2004 Indian Ocean and the 2011 Tohoku-Oki earthquakes and accompanying tsunamis.

We have all seen the horrifying images and videos from these events. The spread of mobile phones with reasonable quality cameras means that within hours of a disaster images begin to appear on the net. For me, there is one video in particular which captures the terrifying raw power unleashed by these disasters. It was captured from on top of a solid building and shows the rapid speed and destructiveness of the tsunami. It also clearly demonstrates the huge amount of displaced water that is involved.

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Making a scene – Leapfrog Saved Scene

By Sam Bain

Imagine you have built an amazing geological model. You have identified and fixed the problems in the core logging, you have reconciled the lithology labels used by the different historical surveys of the area, your geological surfaces are consistent with the data and make geological sense, your grade model has been built taking into account the geological structures and you are happy with its predictions. Is that your job done? No, of course not.

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