scholarly journals The Subantarctic lithospheric mantle

2021 ◽  
pp. M56-2020-13
Author(s):  
Guillaume Delpech ◽  
James M. Scott ◽  
Michel Grégoire ◽  
Bertrand Moine ◽  
Dongxu Li ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Lithospheric Mantle ◽  
Sandwich Plate ◽  
Fracture Zones ◽  
Content Type ◽  
Kerguelen Islands ◽  
Peridotite Xenoliths ◽  
Os Isotopes ◽  
Supplementary Material ◽  
The Antarctic

AbstractWe present a summary of peridotite in the Subantarctic (46 to 60°S) surrounding the Antarctic Plate. Peridotite xenoliths occur on Kerguelen and Auckland islands. Kerguelen islands are underlain by a plume whereas the Auckland Islands are part of continental Zealandia, which is a Gondwana-rifted fragment. Small amounts of serpentinised peridotite has been dredged from fracture zones on the Southeast Indian, Southwest Indian, and Pacific Antarctic Ridge, and represents upwelled asthenosphere accreted to form lithosphere. Supra-subduction zone peridotite has been collected from two locations on the Sandwich Plate. Peridotites from most Subantarctic occurrences are moderately to highly depleted, and many show signs of subsequent metasomatic enrichment. Os isotopes indicate that the Subantarctic continental and oceanic lithospheric mantle contains ancient fragments that underwent depletion long before formation of the overlying crust.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5424956

Subduction-related subcontinental lithospheric mantle metasomatism and crustal thickening: origin for superchondritic Nb/Ta in mafic dykes

2020 ◽  
Vol 178 (1) ◽  
pp. jgs2020-120
Author(s):  
Xiang Cui ◽  
Wenbin Zhu ◽  
F. Jourdan
Keyword(s):  
Trace Element ◽  
South China ◽  
Lithospheric Mantle ◽  
Incompatible Trace Element ◽  
Mantle Metasomatism ◽  
Crustal Thickening ◽  
Subcontinental Lithospheric Mantle ◽  
Content Type ◽  
Mafic Dykes ◽  
Supplementary Material

Superchondritic Nb/Ta is rarely reported in terrestrial reservoirs and is usually attributed to carbonatite metasomatism or accessory rutile in the residue phase. Previously documented high Nb/Ta in rocks derived from subcontinental lithospheric mantle indicated a predominance of carbonatite metasomatism. This study evaluates Nb/Ta in conjunction with other trace elements of Neoproterozoic mafic dykes exposed in the eastern segment of the Jiangnan Orogen, where early subduction existed before the amalgamation of South China. These mafic dykes show mostly superchondritic Nb/Ta ratios from 19.6 to 24.5. Partial melting modelling suggested low-degree melting of rutile-bearing subcontinental lithospheric mantle for these mafic dykes. A literature review of Neoproterozoic mafic–intermediate rocks throughout the Jiangnan Orogen shows sporadically but coincidently superchondritic Nb/Ta near or beneath the Shuangxiwu arc, indicating rutile stability in the relict sub-arc mantle. Rutile in the lherzolite was formed sometime after Neoproterozoic subduction initiation in South China but contemporaneous with crustal thickening at c. 860 Ma. This study brings direct evidence to bear on the mechanism of rutile formation in the mantle wedge, as well as the link between crustal thickening and superchondritic Nb/Ta of mafic products derived from the metasomatized mantle.Supplementary material: Major and trace element compositions, photomicrographs of samples, and figures illustrating geochemistry, REE and incompatible trace element patterns and loss on ignition versus Nb/Ta and La/Yb are available at https://doi.org/10.6084/m9.figshare.c.5093535

scholarly journals Petrogenesis of Mediterranean lamproites and associated rocks: the role of overprinted metasomatic events in the postcollisional lithospheric upper mantle

2021 ◽  
pp. SP513-2021-36
Author(s):  
Martina Casalini ◽  
Riccardo Avanzinelli ◽  
Simone Tommasini ◽  
Claudio Natali ◽  
Gianluca Bianchini ◽  
...  
Keyword(s):  
Mantle Source ◽  
Lithospheric Mantle ◽  
Central Italy ◽  
Western Anatolia ◽  
Calc Alkaline ◽  
Content Type ◽  
High K ◽  
Supplementary Material ◽  
The Mediterranean ◽  
Lithospheric Mantle Source

AbstractHigh-MgO lamproite and lamproite-like (i.e., lamprophyric) ultrapotassic rocks are recurrent in the Mediterranean and surrounding regions. They are associated in space and time with ultrapotassic shoshonites and high-K calc-alkaline rocks. This magmatism is linked with the geodynamic evolution of the westernmost sector of the Alpine-Himalaya collisional margin, which followed the closure of the Tethys ocean. Subduction-related lamproites, lamprophyres, shoshonites and high-K calc-alkaline suites were emplaced in the Mediterranean region in the form of shallow level intrusions (e.g., plugs, dykes, and laccoliths), and small volume lava flows, with very subordinate pyroclastic rocks, starting from the Oligocene, in the Western Alps (Northern Italy), through the Late Miocene in Corsica (Southern France) and in Murcia-Almeria (South-Eastern Spain), to the Plio-Pleistocene in Southern Tuscany and Northern Latium (Central Italy), in the Balkan peninsula (Serbia and Macedonia), and in the Western Anatolia (Turkey). The ultrapotassic rocks are mostly lamprophyric, but olivine latitic lavas with a clear lamproitic affinity are also found, as well as dacitic to trachytic differentiated products. Lamproite-like rocks range from slightly silica under-saturated to silica over-saturated composition, have relatively low Al2O3, CaO, and Na2O contents, resulting in plagioclase-free parageneses, and consist of abundant K-feldspar, phlogopite, diopsidic clinopyroxene and highly forsteritic olivine. Leucite is generally absent and it is rarely found only in the groudmasses of Spanish lamproites. Mediterranean lamproites and associated rocks share an extreme enrichment in many incompatible trace elements and depletion in High Field Strength Elements and high, and positively correlated Th/La and Sm/La ratios. They have radiogenic Sr and unradiogenic Nd isotope compositions, high 207Pb over 206Pb and high time integrated 232Th/238U. Their composition requires an originally depleted lithospheric mantle source metasomatised by at least two different agents: i) a high Th/La and Sm/La (i.e., SALATHO) component deriving from lawsonite-bearing, ancient crustal domains likely hosted in mélanges formed during the diachronous collision of the northward drifting continental slivers from Gondwana; ii) a K-rich component derived from a recent subduction and recycling of siliciclastic sediments. These metasomatic melts produced a lithospheric mantle source characterised by network of felsic and phlogopite-rich veins, respectively. Geothermal readjustment during post-collisional events induced progressive melting of the different types of veins and the surrounding peridotite generating the entire compositional spectrum of the observed magmas. In this complex scenario, orogenic Mediterranean lamproites represent rocks that characterise areas that were affected by multiple Wilson cycles, as observed in the the Alpine-Himalayan realm.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5414418

U-Pb isotopic ages and provenance of some far travelled exotic pebbles from glaciogenic sediments of the Polonez Cove Formation (Oligocene, King George Island)

2020 ◽  
pp. jgs2020-113
Author(s):  
Jerzy Nawrocki ◽  
Magdalena Pańczyk ◽  
Krystian Wójcik ◽  
Andrzej Tatur
Keyword(s):  
Source Area ◽  
Crystalline Rocks ◽  
Substantial Part ◽  
King George Island ◽  
Pb Isotope ◽  
Content Type ◽  
Isotope Data ◽  
Supplementary Material ◽  
Glaciogenic Sediments ◽  
The Antarctic

Zircon grains from nine erratic pebbles of granite, granodiorite/tonalite and quartzite from the Polonez Cove Formation (southern King George Island) were studied for their U-Pb isotope ages and provenance. The calculated concordia ages of the studied pebbles are 108.79 ± 0.89 Ma, 119.7 ± 2.2 Ma, 178.6 ± 2.8 Ma, 180.7 ± 1.9 Ma, 207.4 ± 3.1 Ma, 231.1 ± 1.9 Ma, 1087.5 ± 4 Ma and 1833 ± 4 Ma. The source area of individual pebbles was analyzed and defined. Pebbles of crystalline rocks were derived from the Antarctic Peninsula, as well as from the Antarctic mainland. The erratic made of quartzite was eroded from the southernmost part of the Ellsworth Mountains (Linder Pak Member of Howard Nunatak Formation). Our isotope data analytically supports the earlier thesis that the Oligocene ice-sheet covered a substantial part of Antarctica and its nucleus was located in its central part.Supplementary material: The U-Pb isotope data (Table S1) are available at https://doi.org/10.6084/m9.figshare.c.5233335

scholarly journals Marie Byrd Land lithospheric mantle: A review of the xenolith record

2021 ◽  
pp. M56-2020-17
Author(s):  
Monica R. Handler ◽  
Richard J. Wysoczanski ◽  
John A. Gamble
Keyword(s):  
Lithospheric Mantle ◽  
Rift System ◽  
Type I ◽  
Content Type ◽  
Partial Melt ◽  
West Antarctic ◽  
Supplementary Material ◽  
Geochemical Analyses ◽  
West Antarctic Rift System ◽  
West Antarctic Rift

AbstractThe Marie Byrd Land (MBL) lithospheric mantle xenolith record comprises over 100 samples from a range of localities spanning both major crustal terranes that comprise MBL: Ross and Amundsen provinces. Coarse granular to porphyroclastic in texture, the xenoliths are predominantly Type I spinel-bearing lherzolites to harburgites, but include rare dunite and pyroxenite examples. Garnet is absent and no hydrous phases, such as amphibole or mica, have been reported to date, although traces of apatite may be present. Characterisation of the lithospheric mantle composition and its evolution however, is hampered by patchy and uneven geochemical analyses across the xenolith suite. Nonetheless, a picture emerges of a heterogeneous lithosphere beneath both Ross and Amundsen Provinces. Previously published and new data reported here are consistent with samples ranging from variably cryptically metasomatised residua from variable (10 - 25%) degrees of partial melt extraction to refertilised compositions. Limited isotopic data point to a complex history, providing evidence for both ancient Proterozoic lithospheric mantle and preservation of Ordovician events. The Sr-Nd-Pb composition of the sampled lithospheric mantle overlaps the common low-µ isotopic endmember identified in Cenozoic magmatism from MBL and the wider West Antarctic Rift System.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5309814

Microscale effects of melt infiltration into the lithospheric mantle: Peridotite xenoliths from Xilong, South China

Lithos ◽  
2015 ◽  
Vol 232 ◽  
pp. 111-123 ◽  
Author(s):  
Jianggu Lu ◽  
Jianping Zheng ◽  
William L. Griffin ◽  
Suzanne Y. O'Reilly ◽  
Norman J. Pearson
Keyword(s):  
South China ◽  
Lithospheric Mantle ◽  
Mantle Peridotite ◽  
Peridotite Xenoliths ◽  
Melt Infiltration

scholarly journals Metagenomic Analysis of Stress Genes in Microbial Mat Communities from Antarctica and the High Arctic

2011 ◽  
Vol 78 (2) ◽  
pp. 549-559 ◽  
Author(s):  
Thibault Varin ◽  
Connie Lovejoy ◽  
Anne D. Jungblut ◽  
Warwick F. Vincent ◽  
Jacques Corbeil
Keyword(s):  
High Arctic ◽  
Environmental Stresses ◽  
The Arctic ◽  
Functional Responses ◽  
Protein Coding ◽  
Content Type ◽  
Stress Genes ◽  
Cyanobacterial Genes ◽  
Shock Proteins ◽  
The Antarctic

ABSTRACTPolar and alpine microbial communities experience a variety of environmental stresses, including perennial cold and freezing; however, knowledge of genomic responses to such conditions is still rudimentary. We analyzed the metagenomes of cyanobacterial mats from Arctic and Antarctic ice shelves, using high-throughput pyrosequencing to test the hypotheses that consortia from these extreme polar habitats were similar in terms of major phyla and subphyla and consequently in their potential responses to environmental stresses. Statistical comparisons of the protein-coding genes showed similarities between the mats from the two poles, with the majority of genes derived fromProteobacteriaandCyanobacteria; however, the relative proportions differed, with cyanobacterial genes more prevalent in the Antarctic mat metagenome. Other differences included a higher representation ofActinobacteriaandAlphaproteobacteriain the Arctic metagenomes, which may reflect the greater access to diasporas from both adjacent ice-free lands and the open ocean. Genes coding for functional responses to environmental stress (exopolysaccharides, cold shock proteins, and membrane modifications) were found in all of the metagenomes. However, in keeping with the greater exposure of the Arctic to long-range pollutants, sequences assigned to copper homeostasis genes were statistically (30%) more abundant in the Arctic samples. In contrast, more reads matching the sigma B genes were identified in the Antarctic mat, likely reflecting the more severe osmotic stress during freeze-up of the Antarctic ponds. This study underscores the presence of diverse mechanisms of adaptation to cold and other stresses in polar mats, consistent with the proportional representation of major bacterial groups.

Volcano-sedimentary processes at Las Derrumbadas rhyolitic twin domes, Serdán-Oriental basin, Eastern Trans-Mexican Volcanic Belt

2021 ◽  
pp. SP520-2021-144
Author(s):  
Marie-Noëlle Guilbaud ◽  
Corentin Chédeville ◽  
Ángel Nahir Molina-Guadarrama ◽  
Julio Cesar Pineda-Serrano ◽  
Claus Siebe
Keyword(s):  
Volcanic Belt ◽  
Debris Avalanche ◽  
Density Currents ◽  
Content Type ◽  
Mexican Volcanic Belt ◽  
Wide Range ◽  
Eruptive Episode ◽  
Basin Floor ◽  
Supplementary Material ◽  
Trans Mexican Volcanic Belt

AbstractThe eruption of the ∼10 km3 rhyolitic Las Derrumbadas twin domes about 2000 yrs ago has generated a wide range of volcano-sedimentary deposits in the Serdán-Oriental lacustrine basin, Trans-Mexican Volcanic Belt. Some of these deposits have been quarried, creating excellent exposures. In this paper we describe the domes and related products and interpret their mode of formation, reconstructing the main phases of the eruption as well as syn-and-post eruptive erosional processes. After an initial phreatomagmatic phase that built a tuff ring, the domes grew as an upheaved plug lifting a thick sedimentary pile from the basin floor. During uplift, the domes collapsed repeatedly to form a first-generation of hetero-lithologic hummocky debris avalanche deposits. Subsequent dome growth produced a thick talus and pyroclastic density currents. Later, the hydrothermally-altered over-steepened dome peaks fell to generate 2nd generation, mono-lithologic avalanches. Subsequently, small domes grew in the collapse scars. From the end of the main eruptive episode onwards, heavy rains remobilized parts of the dome carapaces and talus, depositing lahar aprons. Las Derrumbadas domes are still an important source of sediments in the basin, and ongoing mass-wasting processes are associated with hazards that should be assessed, given their potential impact on nearby populations.Supplementary material at https://doi.org/10.6084/m9.figshare.c.5752296

Jurassic–Cretaceous arc magmatism along the Shyok–Bangong Suture from NW Himalaya: Formation of the peri-Gondwana basement to the Ladakh Arc

2021 ◽  
pp. jgs2021-035
Author(s):  
Wanchese M. Saktura ◽  
Solomon Buckman ◽  
Allen P. Nutman ◽  
Renjie Zhou
Keyword(s):  
Late Cretaceous ◽  
Nw Himalaya ◽  
Content Type ◽  
Magmatic Arc ◽  
Basement Rocks ◽  
Ladakh Himalaya ◽  
Accreted Terranes ◽  
Volcaniclastic Rocks ◽  
Supplementary Material ◽  
Depositional Age

The Jurassic–Cretaceous Tsoltak Formation from the eastern borderlands of Ladakh Himalaya consists of conglomerates, sandstones and shales, and is intruded by norite sills. It is the oldest sequence of continent-derived sedimentary rocks within the Shyok Suture. It also represents a rare outcrop of the basement rocks to the voluminous Late Cretaceous–Eocene Ladakh Batholith. The Shyok Formation is a younger sequence of volcaniclastic rocks that overlie the Tsoltak Formation and record the Late Cretaceous closure of the Mesotethys Ocean. The petrogenesis of these formations, ophiolite-related harzburgites and norite sill is investigated through petrography, whole-rock geochemistry and U–Pb zircon geochronology. The youngest detrital zircon grains from the Tsoltak Formation indicate Early Cretaceous maximum depositional age and distinctly Gondwanan, Lhasa microcontinent-related provenance with no Eurasian input. The Shyok Formation has Late Cretaceous maximum depositional age and displays a distinct change in provenance to igneous detritus characteristic of the Jurassic–Cretaceous magmatic arc along the southern margin of Eurasia. This is interpreted as a sign of collision of the Lhasa microcontinent and the Shyok ophiolite with Eurasia along the once continuous Shyok–Bangong Suture. The accreted terranes became the new southernmost margin of Eurasia and the basement to the Trans-Himalayan Batholith associated with the India-Eurasia convergence.Supplementary material:https://doi.org/10.6084/m9.figshare.c.5633162

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