GRSG Conference 2022: Orbit to Outcrop

Title: Hyperspectral Imaging of Early-Earth Hydrothermal Processes

Author: Frank van Ruitenbeek


We are investigating hydrothermal processes using airborne hyperspectral imaging, airborne geophysics, and surface field mapping in the paleo-Archean Coongan greenstone sequence in the Pilbara craton in Western Australia. The greenstone sequence is well exposed and shows laterally and vertically continuous cross-sections through ~3.4 Ga volcanic and volcano-sedimentary rocks.

The rock outcrops contain abundant signs of hydrothermal activity in the Paleo-Archean. The excellent exposure, lack of significant surface weathering and vegetation cover, and preservation of primary geological structures and textures make the sequence ideal for studying Early Earth hydrothermal processes, which in this belt are linked to hydrothermal mineral deposits and early-life habitats.

Preliminary results show that we can identify paleo-surfaces within the sequence in which hydrothermal discharge occurred, and different types of early-life habitats. Many strata are hydrothermally altered, and at least two episodes of hydrothermal fluid discharge have be identified.

Discharge zones may be connected to kilometre long feeder dykes that crosscut the stratigraphy. The spatial relationships between deposits and hydrothermal alteration minerals suggest that some deposits are linked to the hydrothermal alteration processes and architecture. 

Integrating airborne geophysical and hyperspectral imagery with field data is crucial in the geological interpretation workflow and target definition for fieldwork follow-up. The different data sets each provide complementary information required for reconstruction and the geology and paleo-hydrothermal processes. The results of this ongoing study may provide fundamental insights into the early Earth processes related to deposit formation and early-life habitats.