Australia East Antarctica Research Articles

Rodinia palaeogeography: Laurentia as the geological ‘Key’

Abstract Laurentia, core of the North American continent, is surrounded by Neoproterozoic to Cambrian rifted margins. This led to early suggestions that it was located within a Neoproterozoic supercontinent, Rodinia. Recent models of Precambrian palaeogeographical development also point to a ‘Laurentia-centric’ Rodinian supercontinent. Before plate tectonics, the geometry of continental margins, comparison of cratonic interiors and sedimentary covers, and orogenic piercing points were employed to postulate the geography of Phanerozoic Pangaea. Marine studies have subsequently demonstrated that the results were remarkably accurate. Absent in situ Precambrian oceanic crust, the same lines of evidence are employed here to reconstruct Rodinia, together with others unavailable at that time. A strong case can be made for the former juxtaposition of the Pacific margins of Laurentia and East Antarctica–Australia approximately as proposed in the 1990s, even though the precise match remains elusive. The Atlantic margin is likely to have rifted from Baltica, Amazonia and other South American cratons along the Grenvillian orogenic suture in the early Paleozoic, although the suture itself makes accurate reconstruction difficult. A piercing point and ‘tectonic tracer’ can be used to position the Kalahari craton and Coats Land crustal block of Antarctica off the present southern margin of Laurentia and contemporaneous large igneous provinces point to Siberia being located off the Arctic margin. Hence Laurentia does appear to be the ‘Key’ to Rodinian palaeogeography even though the exact geometric fit to its surrounding cratons remains to be refined.

Early Neoproterozoic (870–820 Ma) amalgamation of the Tarim craton (northwestern China) and the final assembly of Rodinia

Abstract In the paleogeographic configuration of the Neoproterozoic supercontinent of Rodinia, the Tarim craton (northwestern China), traditionally seen as a single block, is placed either on the periphery near northern Australia or India or in a central position between Australia and Laurentia. To distinguish between these possibilities, we present here new primary paleomagnetic results from ca. 900 Ma volcanics in the Aksu region of the northwestern Tarim craton. The data reveal a ~28° latitudinal difference between the North Tarim and South Tarim blocks at ca. 900 Ma and constrain the age of amalgamation of the Tarim craton to between 870 and 820 Ma. Combining paleomagnetic poles from Tarim and major cratons of Rodinia with geological evidence, a two-stage orogenic model is proposed for the assembly of Rodinia. Late Mesoproterozoic orogenesis (1.3–1.0 Ga) led to the assembly of Australia–East Antarctica, Baltica, Umkondia, South Tarim, and Cathaysia with Laurentia, forming the core of Rodinia. Thereafter, the Jiangnan–Central Tarim Ocean separating North Tarim and Yangtze from South Tarim and Cathaysia was closed before ca. 820 Ma. This second Jiangnan–Central Tarim orogeny caused nearly coeval amalgamation of the peripheral Tarim and South China cratons by the welding of North Tarim and Yangtze to South Tarim and Cathaysia, respectively. The supercontinent of Rodinia was thus assembled by two orogenic phases separated by ~200 m.y.

Hull fouling marine invasive species pose a very low, but plausible, risk of introduction to East Antarctica in climate change scenarios

AbstractAimsTo identify potential hull fouling marine invasive species that could survive in East Antarctica presently and in the future.LocationAustralia's Antarctic continental stations: Davis, Mawson and Casey, East Antarctica; and subantarctic islands: Macquarie Island and Heard and McDonald Islands.MethodsOur study uses a novel machine‐learning algorithm to predict which currently known hull fouling MIS could survive in shallow benthic ecosystems adjacent to Australian Antarctic research stations and subantarctic islands, where ship traffic is present. We used gradient boosted machine learning (XGBoost) with four important environmental variables (sea surface temperature, salinity, nitrate and pH) to develop models of suitable environments for each potentially invasive species. We then used these models to determine if any of Australia's three Antarctic research stations and two subantarctic islands could be environmentally suitable for MIS now and under two future climate scenarios.ResultsMost of the species were predicted to be unable to survive at any location between now and the end of this century; however, four species were identified as potential current threats and five as threats under future climate change. Asterias amurensis was identified as a potential threat to all locations.Main conclusionsThis study suggests that the risks are very low, but plausible, that known hull fouling species could survive in the shallow benthic habitats near Australia's East Antarctica locations and suggest a precautionary approach is needed by way of surveillance and monitoring in this region, particularly if propagule pressure increases. While some species could survive as adults in the region, their ability to reach these locations and undergo successful reproduction is considered unlikely based on current knowledge.

Mid-Neoproterozoic mafic rocks in the western Jiangnan orogen, South China: Intracontinental rifting or subduction?

Widely distributed Meso- to Neoproterozoic igneous rocks record the evolution of the Jiangnan orogen. We present integrated geochemical and geochronological data for basalts from the Gaoqiao area, northwestern Hunan Province. U-Pb dating of zircons indicates that the formation of Gaoqiao basalts occurred in the Neoproterozoic, no earlier than 757 ± 16 Ma. Like the contemporaneous mafic rocks in neighboring areas, the Gaoqiao basalts show trace element characteristics suggesting derivation from a source similar to ocean-island basalts (OIBs), including strong enrichment in large-ion lithophile elements (LILEs), high-field strength elements (HFSEs) and TiO2, and high Ti/Y ratios. Placed in a regional tectonic context, however, the Gaoqiao suite is most consistent with an intracontinental rift model and offers no support to the idea of ongoing subduction in middle-late Mid-Neoproterozoic time in the western Jiangnan orogen. Despite the coincidence between the age of this rift and the separation of East Antarctica-Australia from Laurentia, we argue that the rift recorded in the South China Block (SCB) was an independent and probably unrelated event during the break-up of the Rodinia supercontinent.

1.6 Ga crustal thickening along the final Nuna suture

1.6 Ga crustal thickening along the final Nuna suture

The Neoproterozoic-early Paleozoic evolution of the Jiamusi Block, NE China and its East Gondwana connection: Geochemical and zircon U–Pb–Hf isotopic constraints from the Mashan Complex

The Jiamusi Block is located in the easternmost Central Asian Orogenic Belt (CAOB) and its tectonic affinity and evolution is highly controversial. Here we describe newly discovered Neoproterozoic orthogneisses and early Paleozoic granitoids of the Mashan Complex from the Jiamusi Block. SIMS U-Pb dating for zircons from three high-grade orthogneisses yields protolith and metamorphic ages ranging from 757 to 751Ma and from 530 to 476Ma, respectively. LA-ICP-MS U-Pb dates for zircons from four gneissic granitoids define two stages of early Paleozoic magmatism (i.e., 530–502Ma, and 490–476Ma). These new data, together with recent published ages, indicate that the basement rocks of the Jiamusi Block record an important Neoproterozoic-early Paleozoic magmatic (ca. 895–476Ma) and metamorphic (ca. 563–476) event, and we accordingly infer that the granulite facies metamorphism might have occurred before 541–476Ma, and around 567–561Ma. Geochemical and zircon Hf isotopic data suggest that the ca. 752Ma rift-related gneisses were derived from dominantly juvenile crustal rocks with both the heat and material involvement of a depleted asthenosphere mantle at relatively low pressures, which then underwent an ancient wall-rock assimilation, whereas the ca. 490–476Ma post-collisional granitoids originated from reworking of an ancient crustal source and subsequently experienced intensive crystal fractionation. The good correlation on the ca. 755–115Ma geological events between the Jiamusi and Khanka blocks suggests they formed a contiguous crustal unit. The existing data indicate that this combined block cannot be directly derived from the Siberia, North China, South China, and Tarim cratons. Instead, it might be either a rifted portion of the Sayang-Baikal orogen or derived from a peri-Gondwana position. We evaluate the model that the Jiamusi-Khanka Block may have originated as part of the Late Neoproterozoic-Cambrian Kuunga orogen trapped between South India and East Antarctica-Australia. Sometime after ca. 470Ma, it rifted away from East Gondwana and drifted northward to collide with the Songliao Block of NE China in the Early Jurassic.

Age, provenance and tectonic setting of Neoproterozoic to early Paleozoic sequences in southeastern South China Block: Constraints on its linkage to western Australia-East Antarctica

Zircon U-Pb-Hf isotopes and whole-rock geochemical data are applied to investigate the age, provenance and tectonic setting of the late Neoproterozoic and overlying sequences from the Cathaysia Block of South China, in order to understand the tectonothermal evolution of this block and its linkage to supercontinents. New zircon U-Pb ages, in combination with previous fossil data, indicate the lower and upper Louziba Groups were deposited between 655 and 635Ma (Cryogenian) and 635 and 542Ma (Ediacaran), respectively. Low CIA (65–57) and high ICV (1.64–1.05) values for the Louziba sandstones are suggestive of immature sediments that experienced mild to weak chemical weathering in their source areas. In contrast, early Paleozoic sandstones have higher CIA (80–69) and lower ICV (0.95–0.84) values, indicative of mature sediments with intensive chemical weathering. Despite the different degrees of chemical weathering, all sedimentary samples show positive correlation between TiO2 and Al2O3, and negative correlation in plot of (La/Yb)n vs Zr but lack any correlation between (La/Yb)n and P2O5. These data demonstrate sorting of resistant minerals, such as rutile, monazite and zircon, did not affect the chemical signatures of sampled detritus. Consequently, geochemical features, in combination with detrital age spectra, indicate that the Louziba Group and overlying sequences record sedimentation in collisional and passive settings, with the detritus being derived dominantly from intermediate to felsic igneous rocks.Late Mesoproterozoic (ca.1300–1000Ma) detritus in the lower Louziba Group were probably derived primarily from the Windmill Islands-Bunger Hills (1300–1050Ma) and Albany-Fraser Belt-Musgrave (1300–1050Ma) regions in East Antarctica-western Australia. Increasing input of early Neoproterozoic (∼990–950Ma) detritus in the uppermost Louziba Group indicates a greater contribution from the Eastern Ghats (ca. 990–950Ma) in eastern India and North Prince Charles Mountains (ca. 990–950Ma) in East Antarctica. This source change was synchronous with the formation of the Kuunga (560–530Ma) and Pinjarra (560–520Ma) Orogens during assembly of Gondwana. The sediments of the Huanglian Formation of the uppermost Louziba Group likely recorded this event. Overlying Paleozoic sequences then were deposited on passive margin with detritus being derived dominantly from an early Neoproterozoic source, e.g., eastern India and East Antarctica.

Mesoproterozoic Tasmania: Witness to the East Antarctica–Laurentia connection within Nuna

Research Article| September 01, 2015 Mesoproterozoic Tasmania: Witness to the East Antarctica–Laurentia connection within Nuna Jacob A. Mulder; Jacob A. Mulder * 1ARC Centre of Excellence in Ore Deposits (CODES), School of Physical Sciences, University of Tasmania, Private Bag 79, TAS 7001, Australia *E-mail: Jacob.Mulder@utas.edu.au Search for other works by this author on: GSW Google Scholar Jacqueline A. Halpin; Jacqueline A. Halpin 1ARC Centre of Excellence in Ore Deposits (CODES), School of Physical Sciences, University of Tasmania, Private Bag 79, TAS 7001, Australia Search for other works by this author on: GSW Google Scholar Nathan R. Daczko Nathan R. Daczko 2ARC Centre of Excellence for Core to Crust Fluid Systems and GEMOC, Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia Search for other works by this author on: GSW Google Scholar Author and Article Information Jacob A. Mulder * 1ARC Centre of Excellence in Ore Deposits (CODES), School of Physical Sciences, University of Tasmania, Private Bag 79, TAS 7001, Australia Jacqueline A. Halpin 1ARC Centre of Excellence in Ore Deposits (CODES), School of Physical Sciences, University of Tasmania, Private Bag 79, TAS 7001, Australia Nathan R. Daczko 2ARC Centre of Excellence for Core to Crust Fluid Systems and GEMOC, Department of Earth and Planetary Sciences, Macquarie University, NSW 2109, Australia *E-mail: Jacob.Mulder@utas.edu.au Publisher: Geological Society of America Received: 04 Apr 2015 Revision Received: 15 Jun 2015 Accepted: 16 Jun 2015 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2015 Geological Society of America Geology (2015) 43 (9): 759–762. https://doi.org/10.1130/G36850.1 Article history Received: 04 Apr 2015 Revision Received: 15 Jun 2015 Accepted: 16 Jun 2015 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Jacob A. Mulder, Jacqueline A. Halpin, Nathan R. Daczko; Mesoproterozoic Tasmania: Witness to the East Antarctica–Laurentia connection within Nuna. Geology 2015;; 43 (9): 759–762. doi: https://doi.org/10.1130/G36850.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Most recent paleogeographic reconstructions of the supercontinent Nuna juxtapose the North Australian craton, Mawson continent (South Australia–East Antarctica), and Laurentia between 1.6 Ga and 1.3 Ga but differ in their relative positioning. The >10-km-thick siliciclastic Rocky Cape Group of Tasmania was deposited in an opening marine basin on the margin of East Antarctica during Nuna breakup. Based on a similar detrital zircon signature and depositional age, the Rocky Cape Group has been correlated with the upper Belt-Purcell Supergroup in Laurentia, thus representing a key tie point within Nuna. Here the detrital zircon age signature of Mesoproterozoic Rocky Cape Group quartzites is investigated by comparing new detrital zircon U-Pb-Hf isotopic data to an extensive compilation of zircon isotopic data from Australia, East Antarctica, and Laurentia. Our analysis demonstrates that the Rocky Cape Group is unlikely to have been sourced from any geological terrane exposed in present-day Australia. Instead, zircon U-Pb-Hf isotopic data from basement terranes in Laurentia and East Antarctica show striking similarities to the Rocky Cape Group detrital signature. Paleocurrent data indicate that the majority of sediment in the Rocky Cape Group was sourced from Laurentia, which was to the southeast (present-day coordinates) of Tasmania, supporting a SWEAT-like (southwest United States–East Antarctica) configuration for Nuna. We suggest that rifting left a thinned continental connection between East Antarctica and Laurentia onto which the lower-middle Rocky Cape Group was deposited between 1.45 and 1.30 Ga. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Mid–Late Neoproterozoic rift-related volcanic rocks in China: Geological records of rifting and break-up of Rodinia

Early Cambrian and Mid–Late Neoproterozoic volcanic rocks in China are widespread on several Precambrian continental blocks, which had aggregated to form part of the Rodinia supercontinent by ca. 900 Ma. On the basis of petrogeochemical data, the basic lavas can be classified into two major magma types: HT (Ti/Y > 500) and LT (Ti/Y < 500) that can be further divided into HT1 (Nb/La > 0.85) and HT2 (Nb/La ≤ 0.85), and LT1 (Nb/La > 0.85) and LT2 (Nb/La ≤ 0.85) subtypes, respectively. The geochemical variation of the HT2 and LT2 lavas can be accounted for by lithospheric contamination of asthenosphere- (or plume-) derived magmas, whereas the parental magmas of the HT1 and LT1 lavas did not undergo, during their ascent, pronounced lithospheric contamination. These volcanics exhibit at least three characteristics: (1) most have a compositional bimodality; (2) they were formed in an intracontinental rift setting; and (3) they are genetically linked with mantle plumes or a mantle surperplume. This rift-related volcanism at end of the Mid–Neoproterozoic and Early Cambrian coincided temporally with the separation between Australia–East Antarctica, South China and Laurentia and between Australia and Tarim, respectively. The Mid–Late Neoproterozoic volcanism in China is the geologic record of the rifting and break-up of the supercontinent Rodinia.

Zircon U-Pb Chronology of the Nyingtri Group, Southern Lhasa Terrane, Tibetan Plateau: Implications for Grenvillian and Pan-African Provenance and Mesozoic-Cenozoic Metamorphism

The Nyingtri Group of the Lhasa terrane in southern Tibet consists dominantly of metasedimentary rocks and orthogneiss. These rocks have a similar mineral paragenesis of plagioclase + K-feldspar + biotite + quartz ± sillimanite ± garnet ± staurolite ± muscovite ± amphibole, indicating amphibolite-facies metamorphic conditions. Inherited detrital zircons from the metasedimentary rocks show magmatic features and yield widely variable 206Pb/238U ages ranging from 3300 to 50 Ma. The data define two prominent age populations, 1200–1000 and 600–500 Ma, indicating that the source of the Nyingtri Group preserves the records of both Grenville and Pan-African magmatic-thermal events. Inherited magmatic zircon cores from the orthogneiss yield a crystallization age of 496 Ma, limiting the depositional age of the metasedimentary sequence to Cambrian or older. Overgrowth rims on the detrital zircons from one metasedimentary rock yield a metamorphic age of 32 Ma. On the basis of these results, together with the regional comparison, we infer that the Nyingtri Group was formed during or before the Cambrian, with a potential provenance from the Pinjarra Orogen of Western Australia–East Antarctica. This rock group, together with the Tethyan Himalayan Sedimentary Sequence, represents an early Paleozoic sedimentary cover of the northern margin of the Gondwana supercontinent that was intruded by Cambrian granites during the circum-Gondwana Andean-type orogeny. Along with published data, this study demonstrates that the Nyingtri Group was metamorphosed during Mesozoic and Cenozoic, as against the previous notion of a Precambrian metamorphic basement for the Lhasa terrane.

The Eastern Ghats Belt … A polycyclic granulite terrain

The Eastern Ghats Belt is a polycyclic granulite terrain along the east coast of India whose western boundary is marked by a shear zone along which the granulites are thrusted over the cratonic units of the Indian shield, and its northern margin is marked by the presence of a number of fault-bounded blocks. Recent work has convincingly brought out that there are domains within the belt having different evolutionary histories. The segment south of the Godavari Rift went through a high grade thermo-tectonic event at ∼1.6-1.7 Ga. North of the Godavari Rift in a narrow zone along the western boundary the last high-grade metamorphic event is of late Archaean age. A series of alkaline plutons along the western boundary zone testifies to a rifting episode at ∼1.3-1.5 Ga. In the major part of the EGB the metamorphism is broadly of Grenvillian age, with two major thermo-tectonic pulses at ∼1.1-1.2 Ga and ∼0.95-1.0 Ga. But high grade conditions persisted for a long period and younger thermal events of ∼0.65 Ga to ∼0.80 Ga are locally recorded. There are differences in the tectonometamorphic histories of different domains, but the tectonic significance of these differences remains uncertain. Pan-African (0.50-0.55) thermal overprints are common and become conspicuous along the western boundary zone. The thrusting of the Eastern Ghats granulites in a hot state over the cratons to the west is of Pan-African age. In the Rodinia assembly (∼0.9 Ga) the Eastern Ghats and the Rayner-Napier Complexes of Antarctica were contiguous, but the pre-Rodinia configuration of these terrains remains unclear. At ∼0.8 Ga during the Rodinia break up Greater India rifted apart from East Antarctica, and only later it docked with Australia-East Antarctica at 530-550 Ma. The continuation of the East Antarctic Pan-African orogenic belts into the Eastern Ghats is yet to be ascertained.

Neoproterozoic India within East Gondwana: Constraints from recent geochronologic data from Himalaya

Recent geochronologic data of detrital zircons and neodymium isotopic signatures of the Himalaya, Arabian–Nubian Shield, and Western Australia–East Antarctica (the Pinjarra Orogen/Circum-East Antarctic Orogen) are assessed to estimate the location of Neoproterozoic basement of the Himalaya. The protolith of the Higher Himalayan Gneisses is considered to have been derived from the Pinjarra Orogen/Circum-East Antarctic Orogen of Western Australia–East Antarctica, and not from the Indian Craton to the south. This conclusion strongly suggests the juxtaposition of the Indian Craton, which forms the basement of the Himalaya, with the Circum-East Antarctic Orogen during the Neoproterozoic when the protolith of the Higher Himalayan Gneisses deposited.

Some key issues in reconstructions of Proterozoic supercontinents

Supercontinents containing most of the earth's continental crust are considered to have existed at least twice in Proterozoic time. The younger one, Rodinia, formed at ∼1.0 Ga by accretion and collision of fragments produced by breakup of the older supercontinent, Columbia, which was assembled by global-scale 2.0–1.8 Ga collisional events. Little consensus has been reached regarding configurations of these supercontinents because of some unresolved issues concerning continental fits. One of these issues concerns how Siberia was related to Laurentia. Previous reconstructions that consider the Aldan Shield of Siberia as a continuation of the Wyoming Province of Laurentia have been largely abandoned in favor of models connecting Siberia to northern Laurentia, but it remains controversial which part of Siberia is contiguous with northern Laurentia. Also at issue is the western Laurentia–Australia–East Antarctica connection. Most Rodinia reconstructions place Australia, together with East Antarctica, adjacent to either western Canada (the SWEAT hypothesis) or the western United States (the AUSWUS hypothesis). However, recent studies combining paleomagnetic and isotopic age data have called into question the validity of SWEAT, AUSWUS and other variants. Another issue is the position of North China in Rodinia/Columbia. Limited paleomagnetic data seem to be consistent with the Paleo-Mesoproterozoic North China–Siberia/Baltica connection, whereas geological data support the recently proposed Archean to Mesoproterozoic North China–India connection. Controversial issues have also been raised about the timing and history of the amalgamation and fragmentation of South America and West Africa. Both geological and paleomagnetic data suggest that South America (São Francisco and Amazonia Cratons) and West Africa (Congo and West African Cratons) coalesced into a single landmass along the 2.1–2.0 Ga Transamazonian/Eburnean orogens. However, whether they were divorced and then re-married to form part of Gondwana, or remained largely coherent from their amalgamation at 2.1–2.0 Ga until their incorporation into Gondwana is unclear. Also little known is the position of Amazonia–West Africa in the proposed supercontinents, with some workers believing that they existed as a separate landmass, whereas others place Amazonia–West Africa adjacent to Baltica. In summary, although geological and paleomagnetic data are supportive of the existence of Proterozoic supercontinents Rodinia and Columbia, they are insufficient to determine their exact geometries.

Grenville-age magmatism at the South Tasman Rise (Australia): A new piercing point for the reconstruction of Rodinia

Research Article| October 01, 2005 Grenville-age magmatism at the South Tasman Rise (Australia): A new piercing point for the reconstruction of Rodinia A.M. Fioretti; A.M. Fioretti 1Consiglio Nazionale delle Ricerche (CNR), Istituto di Geoscienze e Georisorse, Corso Garibaldi 37, I-35137 Padova, Italy, and Visiting Fellows at Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia Search for other works by this author on: GSW Google Scholar L.P. Black; L.P. Black 2Minerals Division, Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia, and Visiting Fellows at Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia Search for other works by this author on: GSW Google Scholar J. Foden; J. Foden 3Department of Geology and Geophysics, University of Adelaide, Adelaide, SA 5005, Australia Search for other works by this author on: GSW Google Scholar D. Visonà D. Visonà 4Dipartimento di Mineralogia e Petrologia, Università di Padova, Corso Garibaldi 37, I-35137 Padova, Italy Search for other works by this author on: GSW Google Scholar Author and Article Information A.M. Fioretti 1Consiglio Nazionale delle Ricerche (CNR), Istituto di Geoscienze e Georisorse, Corso Garibaldi 37, I-35137 Padova, Italy, and Visiting Fellows at Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia L.P. Black 2Minerals Division, Geoscience Australia, GPO Box 378, Canberra, ACT 2601, Australia, and Visiting Fellows at Research School of Earth Sciences, Australian National University, Canberra, ACT 0200, Australia J. Foden 3Department of Geology and Geophysics, University of Adelaide, Adelaide, SA 5005, Australia D. Visonà 4Dipartimento di Mineralogia e Petrologia, Università di Padova, Corso Garibaldi 37, I-35137 Padova, Italy Publisher: Geological Society of America Received: 02 Mar 2005 Revision Received: 03 May 2005 Accepted: 03 May 2005 First Online: 03 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 Geological Society of America Geology (2005) 33 (10): 769–772. https://doi.org/10.1130/G21671.1 Article history Received: 02 Mar 2005 Revision Received: 03 May 2005 Accepted: 03 May 2005 First Online: 03 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation A.M. Fioretti, L.P. Black, J. Foden, D. Visonà; Grenville-age magmatism at the South Tasman Rise (Australia): A new piercing point for the reconstruction of Rodinia. Geology 2005;; 33 (10): 769–772. doi: https://doi.org/10.1130/G21671.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A U-Pb zircon sensitive high-resolution ion microprobe age of 1119.4 ± 8.5 Ma, obtained from a quartz syenite dredged from the South Tasman Rise (Australia), provides the first direct evidence of the presence of Grenville-age magmatic rocks along the central part of the hypothesized Australia–East Antarctica conjugate margin of Laurentia. The distinctive mineralogy and geochemistry of the rock and its Sm-Nd and Pb isotopic signatures 1) indicate that it represents a juvenile Grenville-age addition to the crust, 2) support a correlation with the Grenville magmatic province of the western United States, and 3) set a unique pivotal point for a precise reconstruction of Rodinia. The resulting scenario implies the presence of a new magmatic province crossing the East Antarctic craton, the extension of Proterozoic belts of southwest Laurentia to East Antarctica, and appears consistent with the Australia–western United States (AUSWUS) model. This tectonic setting envisages a near-local source for the ubiquitous Grenville-age detrital zircon population in marginal Neoproterozoic to early Paleozoic Gondwanan sequences and suggests a possible direct source for the widespread Grenville-age inherited zircon component observed in most Paleozoic granites in northern Victoria Land (Antarctica) and east Tasmania (Australia). You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Age, Correlation, and Provenance of the Neoproterozoic Skelton Group, Antarctica: Grenville Age Detritus on the Margin of East Antarctica

Detrital zircon U‐Pb ages constrain the age and provenance of the Skelton Group in southern Victoria Land, one of several Proterozoic‐Cambrian metasedimentary units that form basement to the Ross Orogen in East Antarctica. The age of the youngest detrital zircons combined with previous dating of crosscutting intrusive rocks indicates deposition of the northern and southern parts of the Skelton Group between ca. 1050–535 and ca. 950–551 Ma, respectively. Many zircons in the northern part of the Skelton Group crystallized after partial melting during upper amphibolite facies metamorphism at ca. 505–480 Ma, although older ca. 550‐Ma metamorphic zircon rims indicate an earlier episode of high‐grade metamorphism. Detrital zircon ages from the Skelton Group are dominated by ca. 1300–950‐Ma ages similar to those in the Beardmore Group in East Antarctica and the Adelaidean succession of South Australia, suggesting that these rocks are generally correlative. Zircons that crystallized at ca. 1050 Ma form the major age population of the northern Skelton Group, while a broader range of Neoproterozoic zircons form significant components in other sediments deposited on the margin of East Antarctica–Australia at this time, indicating a close proximity to exposed Grenville age crust. Inferred basement rocks of Grenville age beneath the Ross Orogen in East Antarctica (represented by a potential $$1049\pm 11$$‐Ma orthogneiss), Paleozoic cover in eastern Australia, and ice in Marie Byrd Land in West Antarctica are potential sources for the Grenville age component in these Neoproterozoic sedimentary rocks.

Concordant paleolatitudes for Neoproterozoic ophiolitic rocks of the Trinity Complex, Klamath Mountains, California

[1] New paleomagnetic results from the eastern Klamath Mountains of northern California show that Neoproterozoic rocks of the Trinity ophiolitic complex and overlying Middle Devonian volcanic rocks are latitudinally concordant with cratonal North America. Combining paleomagnetic data with regional geologic and faunal evidence suggests that the Trinity Complex and related terranes of the eastern Klamath plate were linked in some fashion to the North American craton throughout that time, but that distance between them may have varied considerably. A possible model that is consistent with our paleomagnetic results and the geologic evidence is that the Trinity Complex formed and migrated parallel to paleolatitude in the basin between Laurasia and Australia–East Antarctica as the Rodinian supercontinent began to break up. It then continued to move parallel to paleolatitude at least through Middle Devonian time. Although the eastern Klamath plate served as a nucleus against which more western components of the Klamath Mountains province amalgamated, the Klamath superterrane was not accreted to North America until Early Cretaceous time. INDEX TERMS: 1525 Geomagnetism and Paleomagnetism: Paleomagnetism applied to tectonics (regional, global); 5475 Planetology: Solid Surface Planets: Tectonics (8149); 8157 Tectonophysics: Evolution of the Earth: Plate motions—past (3040); 9350 Information Related to Geographic Region: North America; 9619 Information Related to Geologic Time: Precambrian

Sapphirine-Kornerupine Granulites from the Precambrian of Southern Madagascar: Implications for the Evolution of the Deep Crust in East Gondwana

Dalziel, I.W.D. (1991) Pacific margins of Laurentia and East AntarcticaAustralia as a conjugate rift pair: evidence and implications for an Eocambrian supercontinent. Geology, v. 19, pp. 598-601. Gose, W.A., Helper, M.A., Conelly, J.N., Hutson, EE. and Dalziel, I.W.D. (1987) Palaeomagnetic data and U-Pb isotopic age determinations from Coats Land, Antarctica: implications for late Proterozic plate reconstructions. J. Geophys. Res., v. 102, pp. 7887-7902. Groenewald, PB., Moyes,A.B., Grantham, G.H. andKrynaw, J.R. (1995) East Antarctic crustal evolution: geological constraints and modelling in western Dronning Maud Land, Antarctica. Precamb. Res., v. 75,

Rodinia refined or obscured: palaeomagnetism of the Malani igneous suite (NW India)

New palaeomagnetic data from the Neoproterozoic felsic volcanic rocks of the Malani igneous suite (MIS) in NW India, combined with data from an earlier study, yield a palaeomagnetic pole with latitude=74.5°N, longitude=71.2°E (dp/dm=7.4/9.7°). A statistically positive fold test and remanences carried by typical high-temperature oxidation (deuteric) minerals support a primary magnetic signature. U/Pb ages from MIS (771–751 Ma) overlap with those for granitoids and dolerite dykes from the Seychelles microcontinent (mainly 748–755 Ma), and palaeomagnetic data for both entities can be matched with a tight reconstruction fit (Seychelles→India: Euler latitude=25.8°N, longitude=330°E, rotation angle=28°). In this Neoproterozoic time interval, MIS and the Seychelles must have been located at intermediate northerly latitudes along the western margin of Rodinia, with magmatism that probably originated in a continental arc. The most reliable, dated palaeomagnetic data (±756 Ma) from MIS, Seychelles and Australia require a crucial reappraisal of the timing and plate dynamics of Rodinia break-up and Gondwana assemblage. These new data necessitate an entirely different fit of East Gondwana elements than previously proposed, and also call to question the validity of the Southwest US–East Antarctic and Australia–Southwest US models. The palaeomagnetic data mandate that Greater India was located west of Australia rather than forming a conjugate margin with East Antarctica in the Mid-Neoptroterozoic. Break-up of Rodinia along western Laurentia may therefore have taken place along two major Neoproterozoic rifts; one leading to separation of Laurentia and Australia–East Antarctica, and the second between Australia and India.

U–Pb zircon ages of granites from the southern margin of the Yangtze Block: timing of Neoproterozoic Jinning: Orogeny in SE China and implications for Rodinia Assembly

Neoproterozoic Jinningian Bendong granodiorite and Sanfang and Yuanbaoshan Granites occurred in northern Guangxi, southern margin of the Yangtze Block, SE China and were generally considered to be of orogenic origin, that is the collision between the Yangtze and Huanan Blocks during the Jinning Orogeny. These granites were intruded into the Mesoproterozoic Sibao metamorphic basement, and covered unconformably by the Neoproterozoic Danzhou metasediments. They are dominantly peraluminous (ASI=1.18–1.29) and have low initial εNd values of −4.8 to −7.6 indicating derivation from a supracrustal source. With strong enrichment in Rb, K and Th and relatively low Zr, Hf and higher rare earth elements, they are similar to post-collision granites. Zircon U–Pb ages of 819±9, 826±10 and 824±4 Ma were obtained for the Bendong granodiorite and the Sanfang and Yuanbaoshan Granites, respectively, by both SHRIMP and conventional dating methods. The age result precludes the existence of any late Mesoproterozoic (Grenville-age) granitic magmatism in the southern margin of Yangtze Block. Together with previous age determinations of ophiolites along the southern margin of the Yangtze Block, the Jinning Orogeny is referred to the Neoproterozoic orogeny which took place between 1.0 and 0.80 Ga, and likely ended at 0.82 Ga. The granite formation age of ∼0.82 Ga also supports the basal boundary age of 0.80 Ga for the post-orogenic Sinian System, which is probably stratigraphically correlated with the Adeladean System in South Australia. As the link between Australia–East Antarctica and Laurentia in the configuration of the supercontinent Rodinia, the collision between the Yangtze and Huanan Blocks during the Neoproterozoic Jinning Orogeny probably marks the termination of the Rodinia assembly.

South China in Rodinia: Part of the missing link between Australia–East Antarctica and Laurentia?

Research Article| May 01, 1995 South China in Rodinia: Part of the missing link between Australia–East Antarctica and Laurentia? Zheng-Xiang Li; Zheng-Xiang Li 1Department of Geology and Geophysics, University of Western Australia, Nedlands, Western Australia 6907, Australia Search for other works by this author on: GSW Google Scholar Linghua Zhang; Linghua Zhang 1Department of Geology and Geophysics, University of Western Australia, Nedlands, Western Australia 6907, Australia Search for other works by this author on: GSW Google Scholar Christopher McA. Powell Christopher McA. Powell 1Department of Geology and Geophysics, University of Western Australia, Nedlands, Western Australia 6907, Australia Search for other works by this author on: GSW Google Scholar Geology (1995) 23 (5): 407–410. https://doi.org/10.1130/0091-7613(1995)023<0407:SCIRPO>2.3.CO;2 Article history first online: 02 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share MailTo Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Zheng-Xiang Li, Linghua Zhang, Christopher McA. Powell; South China in Rodinia: Part of the missing link between Australia–East Antarctica and Laurentia?. Geology 1995;; 23 (5): 407–410. doi: https://doi.org/10.1130/0091-7613(1995)023<0407:SCIRPO>2.3.CO;2 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Stratigraphic correlations and tectonic analysis suggest that the Yangtze block of South China could have been a continental fragment caught between the Australian craton and Laurentia during the late mesoproterozoic assembly of the supercontinent Rodinia. The Cathaysia block of southeast China may have been part of a 1.9–1.4 Ga continental strip adjoining western Laurentia before it became attached to the Yangtze block around 1 Ga. This configuration provides a western source region for the clastic wedges in the Belt Supergroup of western North America which contain detrital grains of 1.8–1.6 Ga and 1.22–1.07 Ga. The breakup of Rodinia around 0.7 Ga separated South China (Yangtze plus Cathaysia blocks) from the other continents. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.