Pilbara 3D interactive model

The Archaean Pilbara Craton of northwester Western Australia is composed of the 3.6-2.8 Ga North Pilbara granitoid-greenstone terrain and the unconformably overlying volcano-sedimentary sequences (Mount Bruce Supergroup) of the 2.77-2.3 Ga Hamersley Basin (Blake 1993).

Rocks include basalts, ultra-mafics and clastic sediments including sandstone, chert and conglomerate. This relatively well exposed province is an excellent example of how airborne gamma-ray spectrometry can be used to map bedrock types (including zonation within the granites) and structures (Wellman 1999).

Layer descriptions:
Layer 1: Gamma-ternary image with K in red, Th in green and U in blue. Late-stage granites appear in saturated white colours, whereas mafic and ultra-mafic rocks appear in black hues. Over the northern part of the image large colluvial and alluvial fans are distinguished by high K.
Layer 2: First vertical derivative of the total magnetic intensity. The image highlights major bedrock and structural contacts. Note the textural differences between the granites and ultra-mafic rocks.
Layer 3: Ternary Landsat TM image (RGB). Red highlights clay, hydrosilicates and carbonates using the second principal component of combined ratio bands 5/4 and 5/7; Blue largely corresponds to silica (e.g., quartz-rich sand and felsic rocks) using the additions of bands 7 and 1; and green highlights iron oxides based on the 5/4 ratio.

Figure captions (right):
Figure A: Spine of greenstone outcrop with granite over the valley floor
Figure B: Granite outcrop forming tors
Figure C: Chert ridges with skeletal soils over bedrock. Surface radioelement responses will relate to bedrock geochemistry and mineralogy.