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Defining IOCG signatures through compositional data analysis: A case study of lithogeochemical zoning from the Olympic Dam deposit, South Australia.
- Source :
-
Ore Geology Reviews . Feb2019, Vol. 105, p86-101. 16p. - Publication Year :
- 2019
-
Abstract
- Graphical abstract Highlights • First definition of geochemical IOCG mineralisation signature in the Olympic Dam. • The IOCG signature is formed by associations of Cu-U 3 O 8 -Se-S and Au-W-Mo-As-Sb. • Au-W-Mo-Sb-As forms a ∼1800 m deep corridor in the south-eastern lobe of the deposit. • The PCA allows delineation of ore body within a disseminated ore deposit. Abstract The Olympic Dam Cu-U-Au-Ag deposit is dominantly composed of mineralised hematite-breccias and occurs entirely within the Roxby Downs Granite. Multivariate statistical analysis of a large whole-rock, 15 m-interval geochemical dataset (10,565 samples) was undertaken to identify geochemical signatures characteristic of iron-oxide copper gold (IOCG)-style mineralization and constrain the conspicuous lithogeochemical zonation observed at Olympic Dam. Statistical analyses include principal component analysis on centred logratio (clr)-transformed data coupled with hierarchical clustering. Certain groups of elements that can be interpreted in terms of an evolving hydrothermal system relative to host lithologies are derived from data analysis: granitophile (U-W-Sn-Mo); siderophile (Ni-Co); chalcophile (Ag-Bi) and related elements (As-Sb and Au-Te). The distributions of elements within each group are investigated through three vertical cross-sections and are compared with known lithological and Cu-(Fe)-sulphide zonation. Throughout the Olympic Dam Breccia Complex, the IOCG signature is defined by multi-element combinations of the commodity metals Cu, U, Au, and Ag, coupled with a range of trace elements. Overall, the IOCG signature overlaps well with Fe-metasomatism despite mismatch which is likely due to discrete styles of mineralisation found only on the margins of the deposit and also to the presence of mineralised domains within Fe-poor zones. The IOCG signature is composed of two geochemical associations, which exhibit distinct spatial distributions. The first group, Cu-U 3 O 8 -Se-S, shows concentric zonation whereas the second group, Au-W-Mo-Sb-As, forms a vertical ∼1800 m deep corridor in the southeastern lobe of the deposit. The specific Au-W-Mo-As-Sb signature could potentially be generic within IOCG systems across the Olympic Cu-Au province and if so, would provide a proxy model for near-mine exploration. [ABSTRACT FROM AUTHOR]
- Subjects :
- *ANALYTICAL geochemistry
*COPPER ores
*ORE deposits
*MINERALIZATION
*GEOLOGY
Subjects
Details
- Language :
- English
- ISSN :
- 01691368
- Volume :
- 105
- Database :
- Academic Search Index
- Journal :
- Ore Geology Reviews
- Publication Type :
- Academic Journal
- Accession number :
- 134596823
- Full Text :
- https://doi.org/10.1016/j.oregeorev.2018.12.013