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| Titel |
Gold potential in the Dalradian rocks of NW Northern Ireland: GIS-based prospectivity analysis using Tellus data |
| VerfasserIn |
P. A. J. Lusty, P. M. McDonnell, A. G. Gunn, B. C. Chacksfield, M. Cooper |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250024256
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| Zusammenfassung |
| Geographic Information Systems (GIS) are essential tools for the management and
integration of the large amounts of multivariate spatial data used in mineral exploration.
Prospectivity analysis combines these datasets, in the context of a mineral deposit model, to
produce a map showing the distribution of potential for a particular type of mineral deposit.
In this example Arc-Spatial Data Modeller software has been used to analyse the
prospectivity for orogenic vein gold mineralisation in the Dalradian rocks of north-western
Northern Ireland. A knowledge-driven (fuzzy logic) approach was used because of the
small number of gold deposits within the area. Fuzzy logic is used in situations
where information is inexact and the use of classical set theory is inappropriate.
Fuzzy logic allows assignment of weightings to exploration data on a continuous
scale from 1 (full membership) to 0 (full non-membership). This allows a level of
uncertainty or ‘fuzziness’ to be incorporated into the modelling. The key stages of
prospectivity analysis are: (1) analysis of the deposit model to determine key exploration
indicators; (2) data processing, interpretation and analysis to extract key indicators; (3)
assignment of weightings, zones and styles of influence to key indicators; and (4)
calculation of prospectivity. This research is based largely on new geochemical and
geophysical data resulting from the Tellus Project in Northern Ireland. The Tellus Project
involved geochemical and airborne geophysical surveys over the whole of Northern
Ireland carried out between 2004–6 with funding from the Government of Northern
Ireland.
The study area (3074 km2) is underlain mainly by Neoproterozoic rocks of the Dalradian
Supergroup (ca. 590 Ma) which form part of the Caledonide orogenic belt. The Dalradian
Supergroup comprises a thick succession of semi-pelites, psammites and pelites, with
graphitic pelite horizons that host much of the known gold mineralisation. In the Sperrin
Mountains two advanced gold projects, Curraghinalt and Golan Burn, and an operating mine,
Omagh (Cavanacaw), are hosted by Dalradian rocks. The Dalradian rocks of Northern Ireland
were extensively deformed during the Grampian Orogeny and at least four phases of
deformation are recognised. On a deposit scale distinct differences are observed between
Curraghinalt and Cavanacaw including orientation of principal structures, mineralogy and
geochemistry.
The mineral prospectivity analysis integrated a range of datasets including: 1:250 000
scale geological mapping, mineral occurrences, fault vectors, Tellus drainage geochemistry
and geophysics. In order to assess the differences between the Curraghinalt and Cavanacaw
mineral deposit models separate prospectivity models were parameterised. The key
differences between the two models relate to the weightings attached to the structural vectors
and the significance given to particular chemical elements in the drainage geochemical
dataset.
The prospectivity analysis identified several areas prospective for orogenic-style gold
mineralisation. Many of the prospective zones either coincide with known occurrences of
orogenic gold mineralisation or areas considered highly prospective based upon
previous work, validating the process and the model results. The use of specific models
for the Curraghinalt and Cavanacaw deposits has produced significant differences
in the location and extent of the target areas which provide a basis for focusing
exploration for orogenic gold deposits in this region. Detailed examination of all
available data and ground truthing is required in order to validate these targets. In
addition to delineating new areas favourable for gold mineralisation the prospectivity
mapping has provided new insight into possible regional controls on the location of
mineralisation and into the geology of this area. Please fill in your abstract text. |
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