Late Jurassic intraplate faulting in eastern Australia: A link to subduction in eastern Gondwana and plate tectonic reorganisation

Abstract

Eastern Gondwana was subjected to subduction processes during the Middle-Late Jurassic, but how these processes affected intraplate deformation in eastern Australia is poorly understood.Here we present 40 Ar/ 39 Ar, K-Ar, and Rb-Sr geochronological data from illitic clay-bearing fault gouges associated with the northern part of the 200 km long, N-striking, dextral strikeslip, Demon Fault in eastern Australia. We show a major range of geochronological ages at 162.99±0.74 -152.1±4.8 Ma, indicating that the Demon Fault was active during the Late Jurassic. This period partially coincides with the Middle-Late Jurassic deposition of widespread ash-fall tuffs in the Clarence-Moreton, Surat, and Eromanga basins. We propose that Middle-Late Jurassic intraplate tectonism in eastern Australia was influenced by subduction processes farther east, which produced extensive calc-alkaline magmatism in New Zealand from ~170 Ma. A global plate reorganisation event, related to the development of Early-Middle Jurassic sea-floor spreading of the Pacific Plate, possibly acted as the driving mechanism responsible for the intensification of magmatism and intraplate faulting in eastern Gondwana.

Precambrian faulting episodes and insights into the tectonothermal history of North Australia: Microstructural evidence and K–Ar, <sup>40</sup>Ar–<sup>39</sup>Ar, and Rb–Sr dating of syntectonic illite from the intracratonic Millungera Basin

“…In summary, most samples with their various size fractions yield consistent Rb-Sr isochron and individual K-Ar ( 40 Ar-39 Ar) ages. This finding is similar to those reported by some recent studies that presented robust and comprehensive Rb-Sr, 40 Ar-39 Ar, and K-Ar age data for high diagenetic and anchizonal fault gauge illites (e.g., Middleton et al, 2014;Rosenbaum et al, 2015;Babaahmadi et al, 2019). Discrepancy in Rb-Sr and K-Ar ages for few samples, e.g., Dob-441 <2 m (K-Ar age is older) and Dob-449.1 (K-Ar ages are younger), may result from sample heterogeneity (hand-specimen and micro scale, see Figs.…”

“…Such linear relations for fault gouge clays representing acid-leached residue and untreated aliquots and consisting of both 2M and 1M illite can be interpreted as unequivocal indication of a complete isotopic equilibration of the entire illite population during episodic fluid flow episodes controlled by deformation events (cf. Mutlu et al, 2010;Isik et al, 2014;Middleton et al, 2014;Rosenbaum et al, 2015;Babaahmadi et al, 2019). The Rb-Sr isochron ages (1041 ± 46 Ma and 1023 ± 12 Ma) for <2 m fractions of samples JC-360.7, JC-440.5 ( Fig.…”

“…In some tectonically active regions, mineral assemblages from the fault rocks and their parent rocks are significantly different, whereby parent rocks do not contain any alteration minerals with new mineral growth being restricted to the fault rocks. This indicates that the heat and fluid flows associated with mineral authigenesis were not controlled by regional tectonic events in these regions, but rather confined to the areas within the fault zone (e.g., Uysal et al 2006;Isik et al, 2014;Babaahmadi et al, 2019). However, the relation between large-scale fluid flow and seismic events has long been reported (e.g., Bruhn et al, 1994;Eichhubl et al, 2010;Faulkner et al, 2010;Lupi et al, 2010 and references therein).…”

“…Direct dating of brittle faulting is crucial for determining the absolute timing of inscrutable time-space distribution of tectonothermal events in concealed Precambrian terranes. Over the last decade, dating of illitic clay from near-surface fault gouges has increasingly become a routine approach to defining the timing of brittle deformations (van der Pluijm et al, 2001;Uysal et al, 2006;Mutlu et al, 2010;Mancktelow, 2004, Zwingmann et al, 2010;Duvall et al, 2011;Hetzel et al, 2013, Torgersen et al, 2014Mancktelow et al, 2016, Viola et al, 2016Babaahmadi et al, 2019). This technique has been particularly useful in better understanding the development of convergent plate boundaries and continental collisions (e.g., van der Pluijm et al, 2001;Duvall et al, 2011;Isik et al, 2015;Babaahmadi et al 2019), movements along transform plate margins (Uysal et al, 2006;Mutlu et al, 2009;Boles et al, 2015), and the formation of orocline bending accompanied by regional strike-slip faulting (Rosenbaum et al, 2015).…”

Early Jurassic palaeoenvironments in the Surat Basin, Australia – marine incursion into eastern Gondwana

“…While the type of Mesozoic basins represented in eastern Australia have been debated (e.g., Veevers et al, 1982;Fielding et al, 1990;Gallagher, 1990;Yago and Fielding, 1996;Babaahmadi et al, 2019), our analysis and results supports the hypothesis that the Surat Basin sediments were deposited landward of a large subduction zone, and thus the basin represents a retroarc foreland configuration. As pointed out by Jones and Veevers (1983), the co-occurrence of labile sediments shed into the basin from the east, and coals through much of the stratigraphic section (i.e., the Middle-Late Jurassic Walloon Coal Measures) is best explained by persistent subsidence, high water tables, rapid sedimentation, and an orogen to the east.…”