RECONSTRUCTING SOUTHERN LAURENTIA’S PROTEROZOIC SOURCE-TO-SINK SEDIMENTARY DISTRIBUTION SYSTEM

Provenance analysis is a powerful tool for investigating sediment delivery networks, constraining the timing and tempo of magmatic events, and reconstructing the tectonic evolution of orogenic belts and basins. Increasingly, basin analysis studies have tried to quantify detrital zircon (DZ) contributions using mixture modeling to better constrain source to sink relationships. However, forward mixture modeling commonly applied to Phanerozoic-Modern systems requires significant prior knowledge including the number of unique sediment sources, their geology, and their full range of ages, limiting their utility in deep time. To overcome this challenge, we use an inverse mixture modeling approach, non-negative matrix factorization (NMF), to reconstruct the number and age distributions of paleo-source regions to 1.8-1.4 Ga metasedimentary rocks deposited in Proterozoic orogenic basins of the Southwest USA. We compiled >16,000 DZ U-Pb ages from >190 samples for this novel statistical analysis. NMF analysis shows the data are best explained by the following reconstructed endmember distributions representing unique sediment source regions: Laurentian pre-1.8 Ga endmembers, unimodal distributions between 1.79 and 1.65 Ga that correspond to arc magmatism, and a 1.6-1.5 Ga endmember likely derived from Australian cratons. Pre-1.8 Ga endmembers dominate >1.78 Ga Mojave Province and Gunnison block samples and is diluted after 1.75 Ga relative to 1.8-1.7 Ga source contributions. This may reflect removal or burial of pre-1.8 Ga sources or greater relative input from 1.8-1.7 Ga arcs. Samples deposited during the 1.72-1.69 Ga Yavapai orogeny are dominantly derived from 1.8-1.7 Ga sources, reflecting uplift of Paleoproterozoic arcs in the Yavapai hinterland. Basins deposited during the 1.68-1.60 Ga Mazatzal orogeny contain variable components of recycled 1.8-1.7 Ga and arc-derived 1.7-1.6 Ga grains. Mesoproterozoic metasedimentary rocks yield variable amounts of 1.8-1.6 Ga DZ and 1.6-1.5 Ga grains, consistent with interpretations of multiple basins that dominantly received locally derived detritus. These quantitative constraints provide a synoptic perspective on sedimentary provenance and tectonism in the Southwest and highlight the utility of NMF for constraining source to sink processes in deep time.