Y4 Presentation of introduction to Targeting and the terrane-scale targeting (presented to sponsors at the final PDT Meeting in Kalgoorie May 2007)

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 leans heavily on interpretation of potential field data. Forward modelling and inversion of cross-sections, based on solid geology maps, provide better than a first approximation but reliability decreases with extrapolation from the sections. Stereo-models of crustal architecture are possible using closely spaced sections but they are more rigorously produced by 3D inversion. Inversion programs derive a physical property distribution that reproduces potential field observations in a manner consistent with a series of model parameters and geological constraints. The inversion techniques used in this study are based on the smooth-model potential field inversion software, MAG3D and GRAV3D, developed at the University of British Columbia?Geophysical Inversion Facility (UBC?GIF). We tuned some of the parameters and modified the methods for use in regional-scale rather than deposit-scale inversions. The volume of crust chosen for study, centred on the Olympic Dam deposit, is 150 kmx ? 150 kmy ? 10 kmz. Because a buffer is required to minimise edge effects, we model a volume of 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 an Intel? Pentium? 4 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 software support 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 reasonable models 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 as guides to ore. Such predictions are amenable to testing available in exploration programs.

Legacy product - no abstract available

Legacy product - no abstract available

Geoscience Australia is the national mapping agency, providing fundamental geoscientific data in support of mineral and petroleum exploration.

The Laurieton area was visited on 29th-30th January by N.H. Fisher and D.E. Gardner, with R. McLeod, field assistant. Boring and sampling were carried out of a beach deposit south of Grants Head where North Coast Minerals Ltd., are erecting a treatment plant. A brief examination was also made of the area south of Pt. Perpendicular, where exploratory boring was in progress. The deposit south of Grants Head is 2 miles north of the entrance to Camden Haven Inlet and about 4 miles by road from Laurieton. The area that was examined south of Pt. Perpendicular and Camden Head is 2 miles east of Laurieton.

Legacy product - no abstract available

In December, 1950, the Pakistan Government filed a formal application to Australia, through the Technical Assistance to South-East Asia Co-operation Scheme, for three geologists to carry out geophysical surveys in Pakistan. In May 1951, the geologists, J.F. Ivanac and D.M. Traves of the Bureau of Mineral Resources and D. King of the South Australian Mines Department, arrived in Pakistan. Their instructions were to carry out a geological survey of a portion of the Gilgit Agency, and to discuss with the Director of the Pakistan Geological Survey or any other Government Officer familiar with the problem, the alluvial gold deposits of Chitral River and the lignite deposits of West Bengal and Sind. Field investigations commenced from Gilgit in June 1951, and the party spent four months in the region. This report gives an account of the visit and the results of the investigation.

A survey of deposits of radio-active minerals was carried out in an area between Coongan and Yule Rivers, Pilbara Goldfield, W.A., during September and October, 1948. This was a continuation of the survey commenced in the previous year (Record 1947/078). The survey was mainly confined to an inspection of localities from which radio-active minerals had previously been reported. Some other mineral localities were inspected, and the Geiger counter was used extensively on many types of rocks and detrital materials in the areas examined. In this way an occurrence of radio-active columbite was found at Mount Francisco, and columbite and tantalite were therefore included among the minerals to be investigated. Alluvial samples were all concentrated by means of a yandie. Rough estimates of the reserves of radio-active minerals were made. The findings of the survey are outlined in this report. The geology of the area and the occurrence of radio-active minerals are described. Accompanying geological plans are included.

Black sand on beaches in Knocker Bay, near Black Point, and at Record Bay, Port Essington, has been noticed from time to time by Captain F.E. Wells, who mentioned these occurrences to the writer. Opportunity was taken during a recent visit to the locality to secure a sample from the beach at Record Point. The presence of black sand on a narrow beach between Black and Reef Points was confirmed by observations from the ship through binoculars. The locality, general geology of the area, and the occurrence of black sand at Record Point are described in this report. The results of the laboratory examination of the sample are recorded.