Exploration

Geochemical Exploration

Geochemical methods are used extensively during grass root exploration and used in conjunction with Geophysics to regionally locate potential ore bodies within an Exploration Licence area.

The aim is to find some concentration of elements or compounds sufficiently above the “norm” to be called an anomaly, which may indicate mineralization or hydrocarbon accumulations within the region.

Before Geologists even enter the field they need to know what techniques they should apply and this is determined by the type of Ore Body they are exploring for.

Ore Body Characteristics for Geochemical exploration can be grouped as follows;

1. Genetic type

2. Geological Formation

3. Indicator minerals and elements

4. Halo formations

5. Zonality

Data collection can be achieved using the following techniques;

Drilling

To prove the physical existence of the resource you must drill to penetrate the ore body.

Drilling can be split into 3 main types:

RAB
RC
Diamond

As you move from RAB to Diamond drilling the following attributes change:

Speed of drilling decreases eg RAB 1100m per day, Diamond 100m per day
Cost increases eg RAB $10/m, Diamond $100/m
Quality of information gained eg RAB is low quality whilst Diamond is high quality

A successful drill programme starts with early planning and negotiation with the contract drilling company.

Below is a Mindmap that was used to design a successful drilling campaign in Far North Queensland

Geophysical Exploration

There are two main types of Geophysical methods;

Those that utilise the natural fields produced by the Earth
Those that require an energy input into the Earth

The natural field methods use the;

Gravitational
Magnetic
Electrical
Electro-magnetic fields created by the Earth.

Localised studies of variations in the field’s strength can locate concealed geological ore bodies at depth, such as the Massive Copper Porphyry Deposit of Escondida, Chile.

The artificial method requires the generation of local electrical/electromagnetic fields in the substrata to locate anomalies along strike. Also included in this group is the use of Seismic waves which are heavily used in the Oil industry to locate Oil bearing strata and Potential Oil traps (Salt Domes).

Exploration departments utilise a variety of Geophysical methods dependent on what type of Orebody they are exploring for (see table below).

JORC

JORC and CIM

The resource forms the core asset of the mining company, resources can be categorised using either the JORC (Australian) or CIM (Canadian) codes.

JORC (image)

CIM (image)

Differences (table)

Each code has a set of criteria that determines what type of resource the mining company has, and can only be determined by a competent person.

Mining an Inferred Resource is regarded as working in the high risk / low confidence arena, whilst mining a Measured Resource is a low risk and high confidence project more likelyhood of successful.