DEPOSIT TYPES – DEPOSIT MODELS – DEPOSIT STYLES
OCCURRENCE MODEL
– MINERALISING EVENT – MINERAL SYSTEM
– MINERAL PROCESS
A Discussion
At the present time most agencies record a mineral occurrence and may or may not assign a deposit type to it. Most agencies do not record information on mineral systems in their datasets. Indeed most do not have fields to capture data on a mineralising event leading to a specific mineral system. The more traditional
‘district’ or goldfield is recorded however.
The current schema currently shows a class for deposit model and mineral system. In my opinion they can be combined. If by system one means occurrences/deposits derived from the same process then model and system are the same.
The concept of a mineral system needs discussion.
The issue of a definitive deposit type list also requires discussion .
This is covered in the following pages:
My conclusions are:
On deposit type :
The best solution is for a standard table for deposit type descriptors but this requires resolution at a national level first. In the interim it is reasonable to generate a model that accepts a local/ national/state “list’ identified by standard xml conventions.
Mineral system is an attribute of the mineral deposit and possibly should be modelled as such. A mineral system could contain –
Type
Group
Age
Includes Deposit types
NSW can provide a local example to use as an initial classification of type.

1. The individual deposit/ occurrence
Using the Australian experience separate (state/federal) geoscience agencies have lists for deposit types that usually describe the ‘trap’ or depositional site. A recent example is the list compiled for deposits in British Columbia. The terminology used ranges from local examples to being generic in nature. These lists can be extensive and cover a range of concepts or ‘models’.
For example to take an example from Ewers the volcanic associated massive sulphide deposits or skarn and carbonate replacement deposits refer to the host rocks or forming the trap.
Other terms describe a ‘setting’ eg epithermal adularia – gold deposits where the mineralising fluids and gases have deposited at a certain crustal level.
Some deposits are defined by the process of deposition eg placer.
Some structural settings are also used to describe a deposit type.
All of the terms are valid in the local setting and emphasise the difficulty of generating a list that could be universally acceptable. There is the possibility of creating an abbreviated list for Australia similar to the one provided by Ewers.
This is a decision for GGIPAC following discussion by the working group.
The best solution is for a standard table for deposit type descriptors but this requires resolution at a national level first.
In the interim it is reasonable to generate a model that accepts a local/ national/state
“list’ identified by standard xml conventions.

2. Mineral systems
A higher deposit group is required for deposits that are related and derived from the same event. This is generally described as a mineral system.
The concept of a mineral system is well established. The process of mineralisation (magmatic – fluid/gas – mechanical) can lead to a single deposit or a range of deposits of differing “deposit types”.
The complete system is described by a number of workers as a cycle from ore generation, transport, deposition in traps and residual outflow.
It is therefore possible to describe a mineral system as having a number of characteristics.
It is an event occurring over a period of time.
It involves mineral transport by either magmatic, fluid/gas, or sedimentary processes.
Systems have distinctive characteristics (fluid chemistry etc)
Systems may include a number of deposit types (traps)
NSW has established a prototype table linking deposit types to systems and describing their characteristics. The chart is near completion. The interim chart is available and will be tabled in Melbourne.
Once again in the absence of a commonly accepted classification this can be included as a local list.
In the case of NSW it is intended that each system be identified as a specific event. This is not necessary for this generic model where identification of a system type and group is sufficient.
The mineral system is an attribute of the mineral deposit and possibly should be modelled as such.
A mineral system could contain –
Type and
Deposit Group (see example below)
Age
Includes Deposit types
NSW can provide a local example to use as an initial classification of type.

Mineral System Terms
– Example
TYPE – reduced SEDEX systems
GROUP –Broken Hill type, Selwyn type, Cobar Cu-Au, Cobar Pb-Zn-Ag.
DEPOSIT TYPE
– (Broken Hill varieties) Corruga type, Thakaringa type,
Broken Hill type etc.
Note that there may be repetition of terms between group and deposit type. This is acceptable.
PROBLEMS
The mineral system contains one or more deposit types. These are not defined as a reference table at present. It can be
REFERENCES
This discussion paper is currently lacking prior references to terms and concepts etc.
They will be added to an amended document and posted to Twiki.