Late Neoproterozoic–Cambrian magmatism in Dronning Maud Land (East Antarctica): U–Pb zircon geochronology, isotope geochemistry and implications for Gondwana assembly (original) (raw)
Related papers
Gondwana Research, 2017
Detrital zircons from the upper Cambrian-Devonian sandstones (Crashsite Group; n=485) and Carboniferous tillite (Whiteout Conglomerate; n=81) of the Ellsworth Mountains, Antarctica record a steady supply of Neoproterozoic ("Pan-African") orogeny (~550-600 Ma), Grenville (~1000 Ma) and Neoarchean (~3000-3500 Ma) zircons into the northern marginal basin of Gondwana. The overlying Permian Glossopteris-bearing Polarstar Formation shales (n=85) have the same zircon provenance as underlying units but also include a dominance of depositional-age (263 Ma) euhedral zircons which are interpreted to be of local, volcanic arc origin. Modeling of detrital zircon provenance suggests that source areas were present in Pan-African and Laurentian crust throughout the Paleozoic. We also report calcite twinning strain results (12 strain analyses; n=398 twins) for the Cambrian Minaret Fm. in the Heritage range which is predominantly a layer-parallel shortening strain in the direction (WSW-ENE) of Permian Gondwanide orogen thrust transport. There is a secondary, sub-vertical twinning strain overprint. The initiation of localized lower-middle Cambrian
Gondwana Research, 2016
Metasedimentary rocks in the Antarctic Peninsula and southwestern Patagonia record detrital zircon evidence for significant Permian magmatic events along the Palaeo-Pacific margin of south West Gondwana. However, it is unclear where and how this magmatism formed due to the lack of outcropping Permian igneous sources at similar latitudes. Combined U-Pb, O, and Lu-Hf isotope analyses of detrital zircon grains in Permo-Triassic metasedimentary rocks indicate that the Permian magmatism resulted from the interaction of crust-and mantle-derived sources in an active continental margin. Permian detrital zircons from the Trinity Peninsula Group in the Antarctic Peninsula range from crustal signatures in the northern part (δ 18 O of~8‰, initial ε Hf of~−6) to mantle-like values in the south (δ 18 O of~5‰, initial ε Hf of~+3). Zircons from the northern domain have isotopic features similar to those from the Patagonian Duque de York Complex. They also share a secondary Ordovician component of ca. 470 Ma. The Middle Jurassic Cape Wallace Beds in Low Island record a ca. 250 Ma igneous source, with stronger crustal signatures (δ 18 O and initial ε Hf values of 7.5 to 10.8‰ and − 3.2 to − 14.2, respectively). In contrast, zircons from the upper Jurassic Miers Bluff Formation on Livingston Island and Cretaceous sediments on James Ross Island have similar Permian U-Pb ages, O and Hf trends to their Trinity Peninsula Group counterparts, suggesting reworking after the late Jurassic. Our results provide evidence for a Permian subduction-related magmatic arc, partly located in Patagonia and extending to West Antarctica. The southerly decrease in δ 18 O coupled with increasing initial ε Hf indicate fewer sedimentary components in the magma source and is consistent with a glaciated cold and dry climate. These conditions are comparable with West Antarctica climate settings, located close to the South Pole during the Carboniferous and Permian.
Geological Society of America Bulletin, 2007
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 ε Hf values, suggesting derivation from juvenile crust, and late Neoproterozoic-Cambrian grains have ε Hf values greater than-5, consistent with remelting of similar juvenile late Mesoproterozoic crust during the Pan African-Ross orogenies. Provenance during rift-ing was from proximal sources from within west Gondwana, most likely, southernmost Africa and basement to the Ellsworth-Whitmore 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 Neoproterozoic-Cambrian grains have ε Hf values less than-5; this means that early Mesoproterozoic-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 ε 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.
Zircon U–Pb age constraints for a Cambrian age for metasedimentary rocks at O’Brien Peak, Antarctica
New Zealand Journal of Geology and Geophysics, 2016
Zircon U-Pb isotopic data provide new depositional age constraints for metasedimentary rocks in the O'Brien Peak area of the Queen Maud Mountains, Antarctica. Zircon grains from a sample of the metasedimentary succession display unabraded, euhedral-subhedral forms, oscillatory zoning and U/Th ratios ≤ 2.9, pointing to an igneous origin. A coherent group of 34 analyses yield a 520 ± 6.6 Ma (2σ) weighted mean age that is likely close to the depositional age, a result consistent with a c. 489 Ma crystallisation age for granites that discordantly cross-cut the sequence. The 520-489 Ma depositional age constraints overlap with depositional ages indicated by biostratigraphic and U-Pb zircon ages for interbedded sedimentary and volcanic rocks found elsewhere in the Ross orogen, supporting a growing body of evidence that sedimentary-volcanic successions in the Queen Maud Mountains, and elsewhere, previously thought to be Neoproterozoic and possibly exotic, are Cambrian and part of the autochthonous peri-Gondwana realm.
GSA Bulletin, 2021
The Lower Permian tillites of the Beacon Supergroup, cropping out in Victoria Land (Antarctica), record climatic history during one of the Earth's coldest periods: the Late Paleozoic Ice Age. Reconstruction of ice-extent and paleo-flow directions, as well as geochronological and petrographic data, are poorly constrained in this sector of Gondwana. Here, we provide the first detrital zircon U-Pb age analyses of both the Metschel Tillite in southern Victoria Land and some tillites correlatable with the Lanterman Formation in northern Victoria Land to identify the source regions of these glaciogenic deposits. Six-hundred detrital zircon grains from four diamictite samples were analyzed using laser ablation–inductively coupled plasma–mass spectrometry. Geochronological and petrographic compositional data of the Metschel Tillite indicate a widespread reworking of older Devonian Beacon Supergroup sedimentary strata, with minor contribution from Cambro-Ordovician granitoids and meta-se...
Precambrian Research, 2006
The Maud Belt in Dronning Maud Land (western East Antarctic Craton) preserves a high-grade polyphase tectono-thermal history with two orogenic episodes of Mesoproterozoic (1.2-1.0 Ga) and Neoproterozoic (0.6-0.5 Ga) age. New SHRIMP U-Pb zircon data from southern Gjelsvikfjella in the northeastern part of the belt make it possible to differentiate between a series of magmatic and metamorphic events. The oldest event recorded is the formation of an extensive 1140-1130 Ma volcanic arc. This was followed by 1104 ± 8 Ma granitoids that might represent, together with so far undated mafic dykes, part of a decompression melting-related bimodal suite that reflects the sub-continental Umkondo igneous event. The first high-grade metamorphism is constrained at 1070 Ma. The metamorphic age data are similar to those obtained from other parts of the Maud Belt, but also from the Namaqua-Natal Belt in South Africa, but the preceding arc formation was diachronous in the two belts. This indicates that the two belts did not form a continuous volcanic arc unit as suggested in previous models, but became connected only at the end of the Mesoproterozoic.
Geoscience Frontiers, 2014
We report new petrological data and geochronological measurements of granulites from Vesleknausen in the highest-grade section of the Lützow-Holm Complex, part of the Gondwana-assembling collisional orogen in East Antarctica. The locality is dominated by felsic to intermediate orthogneiss (charnockite and minor biotite gneiss), mafic orthogneiss, and hornblende-pyroxene granulite, with deformed and undeformed dykes of metagranite and felsic pegmatite. Pseudosection analysis of charnockite in the system NCKFMASHTO, supported by geothermometry of mafic orthogneiss, was used to infer peak metamorphic temperatures of 750e850 C, approximately 150 C lower than those estimated for metasedimentary gneisses from Rundvågshetta, 6 km to the northeast. SHRIMP U-Pb analysis of zircons from feldspar-pyroxene gneiss, which corresponds to a partially molten patch around mafic orthogneiss, yielded a Concordia upper intercept ages of 2507.9 AE 7.4 Ma, corresponding to the time of formation of the magmatic protolith to the orthogneiss. Partial melting during peak metamorphism probably took place between 591 and 548 Ma, as recorded in rims overgrew around magmatic zircon. Our results suggest that Rundvågshetta-Vesleknausen-Strandnibba region in southwestern Lützow-Holm Bay, where orthogneisses are dominant, consists of a single crustal block, possibly formed by ca. 2.5 Ga arc magmatism. The Neoarchean magmatic terrane was tectonically mingled with other fragments (such as metasedimentary units in northern Lützow-Holm Bay) by subduction/collision events during the assembly of Gondwana supercontinent, and subsequently underwent w850 C granulite-facies metamorphosed during Neoproterozoic to Cambrian final collisional event.
Journal of Petrology, 2016
The H.U. Sverdrupfjella is part of the high-grade Maud Belt in Dronning Maud Land (East Antarctica), which was located in a central position of the Gondwana supercontinent. Here we study high-pressure granulites from the eastern H.U. Sverdrupfjella and present a detailed reconstruction of the P–T–t history based on a combination of Zr-in-rutile and Ti-in-zircon thermometry, zircon U–Pb dating, monazite chemical dating, garnet diffusion modelling and petrological modelling. Peak metamorphic conditions of 930Cand1Aˊ45GPapersistedforlessthan6Myrandwereattainedat57067Ma,embeddedinawell−documentedclockwiseloading,heating,anddecom−pressionpath.Therockshadalreadybeenrapidlyexhumedtoacrustaldepthof930 C and 1Á45 GPa persisted for less than 6 Myr and were attained at 570 6 7 Ma, embedded in a well-documented clockwise loading, heating, and decom-pression path. The rocks had already been rapidly exhumed to a crustal depth of 930Cand1Aˊ45GPapersistedforlessthan6Myrandwereattainedat57067Ma,embeddedinawell−documentedclockwiseloading,heating,anddecom−pressionpath.Therockshadalreadybeenrapidlyexhumedtoacrustaldepthof30 km at 556 6 7 Ma. In addition to the very short-lived ultrahigh-temperature peak, zircon preserves evidence for protracted granulite-facies conditions with temperatures above 800 C from as early as c. 590 Ma, persisting for c. 40 Myr. Constraints on prograde metamorphism are recorded in zircon and in rutile inclusions in garnet. Zr-in-rutile thermometry using rutile included in different generations of garnet is used to reconstruct the prograde P–T path, documenting burial followed by heating to ultrahigh temperatures at peak pressures. Complementary Ti zonation in prograde cores of zircon grains documents and dates heating and peak temperatures, whereas younger zircon rims show lower Ti-in-zircon temperatures and date the retrograde stages of metamorphism. Our results provide the first evidence for Neoproterozoic high-pressure granulite-facies metamorphism and ultrahigh-temperature conditions for this region. The clockwise loading–heating path and the peak P–T conditions strongly indicate that the rocks preserved in Dronning Maud Land were part of the lower plate during a continent–continent collision event related to Gondwana assembly at c. 570 Ma. The metamorphic evolution determined in this study and the correlation with similar P–T evolutions documented in adjacent terranes favour the continuation of the c. 580–560 Ma Mozambique Belt into Dronning Maud Land. Furthermore, the striking contemporaneity of the metamorphism in the different parts of central Gondwana suggests that the Coats Land Block was part of greater India prior to this collision.