T141 Dynamics of Earliest Earth Systems

Monday, 23 September 2024
1:30 PM - 5:30 PM
212A

CONSTRAINING UPLIFT IN THE 3.2 GA PILBARA CRATON THROUGH PROVENANCE ANALYSIS OF THE CORBOY FORMATION

Paper number: T141-3
Program: Technical Sessions
Time: 1:55 PM – 2:10 PM

Authors

Abstract

The modern tectonic regime, marked by horizontal differential motion of lithospheric plates, is crucial for a long-lasting habitable surface through nutrient recycling, climate regulation, and forming life-sustaining environments. However, the timing of plate tectonics' origin and preceding regimes remains unclear. The 3.2 Ga Corboy Formation in the Pilgangoora Syncline is proposed as the earliest basin formed by plate tectonics in the Pilbara Craton in a 1986 non-peer reviewed thesis. Here, we reevaluate the claim that it formed via rifting by conducting a provenance study to determine the uplift and erosion sourcing the basin’s submarine channel complex. We conducted conglomerate clast counts, sandstone petrography, detrital zircon (DZ) geochronology, and paleoflow measurements to identify the sources shedding into the basin.

Through stratigraphy, we observe an initial decline in black chert clasts followed by an increase, mirrored by an initial rise and then decrease in silicified mafic tuffaceous clasts. There is a decline in quartzite and sandstone clasts. Sandstone petrography shows an increase in monocrystalline quartz and feldspar and a decrease in lithic grains. Detrital quartz cathodoluminescence highlights constant plutonic sources, with volcanic quartz dwindling through time. DZ geochronology shows a progressive increase in younger age peaks through stratigraphy, shifting from 3.66 Ga, 3.59 Ga, and 3.515 Ga ages to the addition of 3.446 and 3.428 Ga ages, to a dominance of 3.30 Ga ages in the youngest units.

The younging of DZ age peaks, increase in quartz and feldspar grains, and prevalence of plutonic detrital quartz suggest progressive erosion into deeper intruded material. Supracrustal rocks source material throughout stratigraphy, but their relative amount and variety drop over time, evidenced by decreased volcanic detrital quartz, reduced lithic grains, and a shift to black chert clasts higher in stratigraphy. Paleoflow orientation and interpreted sources indicate that the Carlindi and possibly the western flank of the Muccan domes were the main sources for the Corboy Formation. Significant uplift exposed plutonic material potentially due to erosion off an active margin or uplift associated with doming. Future sedimentological work will further constrain the tectonic setting.

Geological Society of America Abstracts with Programs. Vol. 56, No. 5

doi: 10.1130/abs/2024AM-401494

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