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The late Miocene Monte Capanne and Porto Azzurro plutons are investigated by means of coupled U–Pb zircon and 40Ar/39Ar white mica dating to test the occurrence of long‐lived magmatic systems in the upper crust. Zircon crystallized for >1 Ma in both plutonic systems, with supersolidus conditions overlapping for ~220 ka indicating previously unrecognized co‐existence of the two reservoirs. The development of the Porto Azzurro high T‐aureole is post‐dated by continuous igneous zircon crystallization until ~6.0 Ma. By linking crystallization to post‐emplacement cooling of late‐stage pulses in both western and eastern Elba we constrain long‐lived sizeable reservoirs (possibly the same reservoir) in the Tyrrhenian upper crust between ~8 and 6 Ma. [ABSTRACT FROM AUTHOR]

U-Pb dating and Hf-isotope provenance analysis of detrital zircons from the glaciogenic lower Permian Grant Group of the Canning Basin indicate sources principally from basement terranes in central Australia, with subordinate components from terranes to the south and north. Integrating these data with field outcrop and subsurface evidence for ice sheets, including glacial valleys and striated pavements along the southern and northern margins of the basin, suggests that continental ice sheets extended over several Precambrian upland areas of western and central Australia during the late Paleozoic ice age (LPIA). The youngest zircons constrain the maximum age for contemporaneous ice sheet development to the late Carboniferous (Kasimovian), whereas palynology provides a minimum age of early Permian (Asselian-Sakmarian). Considering the palynological age of the Grant Group within the context of regional and global climate proxies, the main phase of continental ice sheet growth was possibly in the Ghzelian-Asselian. The presence of ice sheets older than Kasimovian in western and central Australia remains difficult to prove given a regional gap in deposition possibly covering the mid-Bashkirian to early Ghzelian within the main depocentres and even larger along basin margins, and the poor evidence for older Carboniferous glacial facies. There is also no evidence for extensive glacial facies younger than mid-Sakmarian in this region as opposed to eastern Australia where the youngest regional glacial phase was Guadalupian. [ABSTRACT FROM AUTHOR]

The first δ30Sidiatom data from lacustrine sediment traps are presented from Lake Baikal, Siberia. Data are compared with March surface water (upper 180 m) δ30SiDSi compositions for which a mean value of +2.28 ‰ ± 0.09 (95% confidence) is derived. This value acts as the pre-diatom bloom baseline isotopic composition of waters (δ30SiDSi initial). Open traps were deployed along the depth of the Lake Baikal south basin water column between 2012-2013. Diatom assemblages display a dominance (>85%) of the spring bloom species Synedra acus var radians, so that δ30Sidiatom compositions reflect spring bloom utilisation. Diatoms were isolated from open traps and in addition, from 3 monthly (sequencing) traps (May, June and July 2012) for δ30Sidiatom analyses. Mean δ30Sidiatom values for open traps are +1.23 ‰ ± 0.06 (at 95% confidence and MSWD of 2.9, n = 10) and, when compared with mean upper water δ30SiDSi signatures, suggest a diatom fractionation factor (εuptake) of −1.05 ‰, which is in good agreement with published values from oceanic and other freshwater systems. The near constant δ30Sidiatom compositions in open traps demonstrates the full preservation of the signal through the water column and thereby justifies the use and application of the technique in biogeochemical and palaeoenvironmental research. Data are finally compared with lake sediment core samples, collected from the south basin. Values of +1.30 ‰ ± 0.08 (2σ) and +1.43 ‰ ± 0.13 (2σ) were derived for cores BAIK13-1C (0.6-0.8 cm core depth) and at BAIK13-4F (0.2-0.4 cm core depth), respectively. Trap data highlight the absence of a fractionation factor associated with diatom dissolution (εdissolution) down the water column and in the lake surface sediments, thus validating the application of δ30Sidiatom analyses in Lake Baikal and other freshwater systems, in palaeoreconstructions. [ABSTRACT FROM AUTHOR]

U-Pb detrital zircon geochronology from the upper Cambrian to Devonian part of the Ellsworth Mountains succession, Antarctica, yields dominant late Mesoproterozoic and late Neoproterozoic-Cambrian age populations that are consistent with a provenance from within Gondwana. Hf isotope compositions reveal a source predominantly within west Gondwana and identify a change in provenance up-stratigraphy that coincides with the change of sedimentation setting from active rift to passive margin, which has been independently determined by stratigraphic, structural, and geochemical arguments. For the Late Cambrian Frasier Ridge Formation, late Mesoproterozoic grains have positive Hf values, suggesting derivation from juvenile crust, and late Neoproterozoic-Cambrian grains have Hf values greater than -5, consistent with remelting of similar juvenile late Mesoproterozoic crust during the Pan African-Ross orogenies. Provenance during rifting was from proximal sources from within west Gondwana, most likely, southernmost Africa and basement to the Ellsworth-Whit-more Mountains block. At higher stratigraphic levels where deposition occurred along a passive margin, in the early Ordovician Mount Twiss Member and middle Devonian Mount Wyatt Earp Formation, late Neo-proterozoic-Cambrian grains have Hf values less than -5; this means that early Meso-proterozoic-Archean crust was remelted to generate these zircons. Provenance was from a more expansive source region within west Gondwana, and probably included the Kaapvaal and Congo cratons of south and west Africa. Isolated outcrops of sedimentary rock of uncertain age at Mount Woollard and the Whitmore Mountains have detrital zircon signatures similar to the Frasier Ridge Formation, suggesting correlation with these Late Cambrian deposits. Sedimentary rock from the Stewart Hills contains some late Mesoproterozoic grains with lower Hf values than the previously mentioned samples. This suggests that the Stewart Hills sample has a provenance from within east Gondwana and was possibly deposited on the East Antarctic craton prior to the Ross orogeny and is not part of the displaced Ellsworth-Whitmore Mountains crustal block. [ABSTRACT FROM AUTHOR]