Genesis and Preservation of a Uranium-Rich Paleozoic Epithermal System with a Surface Expression (Northern Flinders Ranges, South Australia): Radiogenic Heat Driving Regional Hydrothermal Circulation over Geological Timescales

Abstract

preservation of a uranium-rich Paleozoic epithermal system with a surface expression (Northern Flinders Ranges, South Australia): radiogenic heat driving regional hydrothermal circulation over geological timescales, Astrobiology, 2011; 11(6) Authors may also deposit this version on his/her funder's or funder's designated repository at the funder's request or as a result of a legal obligation, provided it is not made publicly available until 12 months after official publication. Research ArticlesGenesis The surface expressions of hydrothermal systems are prime targets for astrobiological exploration, and fossil systems on Earth provide an analogue to guide this endeavor. The Paleozoic Mt. Gee-Mt. Painter system (MGPS) in the Northern Flinders Ranges of South Australia is exceptionally well preserved and displays both a subsurface quartz sinter (boiling horizon) and remnants of aerial sinter pools that lie in near-original position. The energy source for the MGPS is not related to volcanism but to radiogenic heat produced by U-Th-K-rich host rocks. This radiogenic heat source drove hydrothermal circulation over a long period of time (hundreds of millions of years, from Permian to present), with peaks in hydrothermal activity during periods of uplift and high water supply. This process is reflected by ongoing hot spring activity along a nearby fault. The exceptional preservation of the MGPS resulted from the lack of proximal volcanism, coupled with tectonics driven by an oscillating far-field stress that resulted in episodic basement uplift. Hydrothermal activity caused the remobilization of U and rare earth elements (REE) in host rocks into (sub)economic concentrations. Radiogenicheat-driven systems are attractive analogues for environments that can sustain life over geological times; the MGPS preserves evidence of episodic fluid flow for the past *300 million years. During periods of reduced hydrothermal activity (e.g., limited water supply, quiet tectonics), radiolytic H 2 production has the potential to support an ecosystem indefinitely. Remote exploration for deposits similar to those at the MGPS systems can be achieved by combining hyperspectral and gamma-ray spectroscopy.

Early Cretaceous glacial environment and paleosurface evolution within the Mount Painter Inlier, northern Flinders Ranges, South Australia

“…All four STM samples presented in this paper (including the Hore et al, 2015 sample) contain detrital zircons yielding U-Pb ages younger than the STM composite sample presented by Brugger et al (2011), whose youngest zircon grain was dated at 315 ± 9 Ma and led them to interpret the STM as a Permian tillite.…”

“…Determination of the age of the STM at Mt Gee has been difficult, with suggested ages ranging from Neoproterozoic (Sturtian) (Youles, 1986) through Permian (Brugger et al, 2011) to as young as Cenozoic (Coats & Blissett, 1971).…”

“…The youngest zircons, aged in (Hore et al, 2015). (e) Sample DC6/MG07 Sprigg Costean (Brugger et al, 2011;W€ ulser, 2009). (f) Sample DC1 East Painter (W€ ulser, 2009).…”

“…In addition to our new data, on the AgeDisplay (Sircombe, 2004) zircon population plots (Figure 24) we include sample R2021406 (Hore et al, 2015) and the concordant zircon LA-ICPMS 206 Pb/ 238 U data analyses obtained by W€ ulser (2009) from two STM samples, DC6 from Mt Gee and DC1 from East Painter. The age of the youngest concordant zircon grain from the Mt Gee sample (DC6) is 315 ± 9 Ma (Brugger et al, 2011;W€ ulser, 2009) and the East Painter sample (DC1) is 165 ± 2 Ma (W€ ulser, 2009). The relatively young age gained from DC1, in particular, is of interest, but we suggest caution in its acceptance as the presentation of the W€ ulser (2009) data is ambiguous, and resampling of the East Painter location (DC1) is recommended.…”

An in situ, micro-scale investigation of inorganically and organically driven rare-earth remobilisation during weathering

“…The Mt Painter Domain cooled below 200°C at 330–320 Ma (McLaren et al , 2002; Mitchell et al , 2002) and slow cooling from >110°C occurred during the Late Carboniferous to Early Permian. Final cooling took place during the Palaeocene to the Eocene, however current relief and relatively high erosion rates are a result of on-going tectonic uplift at rates of 30–160 m Myr –1 due to range-front reverse faulting (Mitchell et al , 2002; Brugger et al , 2005; Quigley et al , 2007; Brugger et al , 2011).…”