168 Laurentia Without Borders: Pre-Pangea Intercontinental Connections

The ancient core of North America is surrounded by Neoproterozoic to early Paleozoic rifts, indicating former juxtaposition with several other cratons. This session will explore these former connections and their paleogeographic, tectonic, and paleoenvironmental implications.

Tuesday, 21 October 2025
8:00 AM - 12:00 PM
HBGCC, 217C

A Mesoproterozoic Tectonic and Metallogenic link between Laurentia and Southeastern Australia: New Evidence from Tasmania’s Rocky Cape Group

Paper number: 168-8
Program: Technical Sessions
Time: 10:00 AM – 10:15 AM

Authors

Abstract

The Belt-Purcell Basin of western North America hosts severeal significant sediment-hosted metal deposits, including the Sullivan Pb-Zn-Ag deposit and numerous Cu-Co prospects. Plate tectonic reconstructions propose a Mesoproterozoic connection between Laurentia and eastern Australia, with the Rocky Cape Group in northwest Tasmania interpreted as a correlative basin to the Belt-Purcell Supergroup. However, until recently, sediment-hosted Cu-Pb-Zn±Co prospects in northwest Tasmania were thought to be Devonian in age, associated with post-orogenic granite intrusions.

Here, we present new in-situ U-Pb geochronology of monazite, xenotime, and apatite, combined with Pb isotope data from galena, to test this correlation. Mineralisation ages from five Cu-Pb-Zn±Co prospects in the Rocky Cape Group indicate a protracted history of hydrothermal activity between ~1350 Ma and ~900 Ma. The oldest mineralisation ages (c. 1350–1280 Ma) coincide with sedimentation in the Belt-Purcell Basin and the East Kootenay Orogeny, suggesting syn-sedimentary to early diagenetic mineralisation processes, similar to those proposed for Belt-Purcell ore systems. Later resetting events at ~1250 Ma, ~1100 Ma, and ~900 Ma correspond with basin-wide metamorphism and fluid flow events also recognised in the Belt-Purcell Basin, further supporting a shared tectonic and metallogenic evolution until at least the Neoproterozoic.

Our revised plate tectonic reconstruction positions Tasmania adjacent to the Belt-Purcell Basin during the Mesoproterozoic, forming a contiguous sedimentary and metallogenic corridor between Laurentia and southeastern Australia. The geochronological similarities in mineralisation and metamorphic events, along with detrital zircon correlations, reinforce this paleogeographic link.

These findings challenge previous assumptions that Tasmania’s sediment-hosted prospects are solely related to Devonian magmatic events and suggest that southeastern Australia, like the Belt-Purcell Basin, may be underexplored for Mesoproterozoic sediment-hosted Cu-Co mineral systems. This study highlights the importance of integrating high-precision mineral geochronology with plate reconstructions to refine global mineral system models and identify new exploration frontiers.

Geological Society of America Abstracts with Programs. Vol. 57, No. 6

doi: 10.1130/abs/2025AM-413824

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