Emplacement of the Argyle diamond deposit into an ancient rift zone triggered by supercontinent breakup

Abstract

Argyle is the world’s largest source of natural diamonds, yet one of only a few economic deposits hosted in a Paleoproterozoic orogen. The geodynamic triggers responsible for its alkaline ultramafic volcanic host are unknown. Here we show, using U-Pb and (U-Th)/He geochronology of detrital apatite and detrital zircon, and U-Pb dating of hydrothermal titanite, that emplacement of the Argyle lamproite is bracketed between 1311 ± 9 Ma and 1257 ± 15 Ma (2σ), older than previously known. To form the Argyle lamproite diatreme complex, emplacement was likely driven by lithospheric extension related to the breakup of the supercontinent Nuna. Extension facilitated production of low-degree partial melts and their migration through transcrustal corridors in the Paleoproterozoic Halls Creek Orogen, a rheologically-weak rift zone adjacent to the Kimberley Craton. Diamondiferous diatreme emplacement during (super)continental breakup may be prevalent but hitherto under-recognized in rift zones at the edges of ancient continental blocks.

(D)rifting in the 21st century: Key processes, natural hazards and geo-resources

“…Natural H 2 is a true wildcard in the energy transition. Still very much underexplored, the vast expanses of exhumed mantle rocks in advanced rift systems and passive margins imply that huge volumes of natural H 2 are formed during rifting (Liu et al, 2023). Perhaps, as Gaucher (2020) argues, the coming years will see the start of a flourishing natural H 2 industry.…”

“…This migration can be explained by progressive removal of the cratonic keel by convective mantle instabilities. For example, the Argyle diamond deposit in the intracontinental rift in the Halls Creek Orogen (Australia) was driven by the break-up of the Nuna supercontinent (Olierook et al, 2023).…”

“…Even so, carbonation is much more efficient when mafic rocks are available, such as mantle rocks or basalts (Matter and Kelemen, 2009). Fresh mantle rocks may be exhumed along the rift axis or spreading ridge During the break-up stage in magma-poor systems, as well as during the drifting stage in slow spreading systems (e.g., Albers et al, 2021;Liu et al, 2023). CO 2 could be artificially injected into these exhumed mantle rocks for storage via enhanced carbonation (e.g., Olajire, 2013;Snaebjörnsdóttir et al, 2020).…”