Abstract

Knowledge of the spatial and temporal relationships between fluid flow, the generation of structures, and crustal architecture is essential to understanding a mineral system. In regions dominated by cover, such knowledge strongly depends on interpretation of potential field data. Forward modelling and inversion of cross-sections, based on solid geology maps, provide valid approximations of 3D crustal geometries but reliability of interpolation decreases away from section planes. Models of crustal architecture are more rigorously produced by 3D inversion. Inversion programs derive physical property distributions that reproduce potential field observations consistent with a set of model parameters and geological constraints. The inversion techniques used in this study are based on the potential field inversion software, MAG3D and GRAV3D, developed at the University of British Columbia-Geophysical Inversion Facility (UBC-GIF). These programs have largely been used at the deposit-scale, but we modified the approach and settings for use at a regional-scale. The volume of crust chosen for study, centred on the Olympic Dam deposit, is 150 kmx 150 kmy 10 kmz. It comprises Archaean granulites, Palaeoproterozoic orthogneiss and metasediments (including BIFs), and early Mesoproterozoic felsic and mafic intrusives and extrusives. Zones of Fe oxide alteration are distributed throughout the upper parts of the crustal volume. Because a buffer is required to minimise edge effects, the volume for inversion is expanded to 198 kmx 198 kmy 18 kmz, discretised into 1 kmx 1 kmy 0.5 kmz cells. A series of trial inversions were run on a desktop PC with a 2.0 GHz processor and 2 GB of RAM. The initial trials were designed to investigate the feasibility of doing regional-scale inversions and to show where development of methods and support software were needed. For tractable computation, it is necessary to split each volume into a number of overlapping tiles that can be processed independently then rejoined. Even so, runs took up to 40 hours. The time elapsed can be substantially reduced if processing is performed as a distributed application across a network with each PC dedicated to a single tile. The inherent non-uniqueness of potential field inversion means that, even after some models have been rejected on 'geo-logical' grounds, a number of models consistent with the solid geology and 2D cross-section forward modelling, inter alia, will remain. Tests that prove or disprove the models may be devised, but actual physical testing may not be practical. However, we can make probabilistic determinations of the distribution of Fe oxide alteration, which may be used to map likely fluid pathways and guides to Fe oxide Cu-Au ore. Such predictions are amenable to testing through current exploration practice.
Google map showing geographic bounding box with values North bound -30.0 East bound 137.25 West bound 136.5 South bound -31.0
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Product Type/Sub Type

dataset - PowerPoint

Constraints

license
Creative Commons Attribution 3.0 Australia Licence

IP Owner

Commonwealth of Australia (Geoscience Australia)

Author(s)

Date (publication)

2004

Product Type

dataset

Topic Category

geoscientificInformation

Keywords

PowerPoint
geochemistry
Earth Sciences

Resource Language

English

Resource Character Set

utf8

Resource Security Classification

unclassified

Geographic Extent

North bound
-30.0
East bound
137.25
West bound
136.5
South bound
-31.0

Lineage

Unknown

Digital Transfer Options

onLine

DISTRIBUTION Format

pdf

Distributor

Role
distributor
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address

Metadata File Identifier

a05f7892-eb48-7506-e044-00144fdd4fa6

Metadata Standard Name

ANZLIC Metadata Profile: An Australian/New Zealand Profile of AS/NZS ISO 19115:2005, Geographic information - Metadata

Metadata Standard Version

1.1

Metadata Date Stamp

2008-11-18

METADATA SECURITY CLASSIFICATION

unclassified

Metadata Contact

Role
pointOfContact
Organisation Name
Geoscience Australia
City
Canberra
Administrative Area
ACT
Postal Code
2601
Country
Australia
Email Address
Downloads
For information on acquiring this product,
please contact the Geoscience Australia Sales Centre via:

fax:
+61 2 6249 9960; or
phone:
1800 800 173 (within Australia);
 
+61 2 6249 9966 (outside Australia).

Please note that support hours are 9 am to 5 pm weekdays