Chapter 2.2a Palmer Land and Graham Land volcanic groups (Antarctic Peninsula): volcanology

2021 ◽  
pp. M55-2018-36 ◽  
Author(s):  
Teal R. Riley ◽  
Philip T. Leat
Keyword(s):  
Antarctic Peninsula ◽  
Volcanic Rocks ◽  
Flood Basalt ◽  
Large Igneous Province ◽  
West Antarctica ◽  
Silicic Volcanic ◽  
Pacific Margin ◽  
Southward Extension ◽  
Continental Magmatism ◽  
The Antarctic

AbstractThe break-up of Gondwana during the Early–Middle Jurassic was associated with flood basalt volcanism in southern Africa and Antarctica (Karoo–Ferrar provinces), and formed one of the most extensive episodes of continental magmatism of the Phanerozoic. Contemporaneous felsic magmatism along the proto-Pacific margin of Gondwana has been referred to as a silicic large igneous province, and is exposed extensively in Patagonian South America, the Antarctic Peninsula and elsewhere in West Antarctica. Jurassic-age silicic volcanism in Patagonia is defined as the Chon Aike province and forms one of the most voluminous silicic provinces globally. The Chon Aike province is predominantly pyroclastic in origin, and is characterized by crystal tuffs and ignimbrite units of rhyolite composition. Silicic volcanic rocks of the once contiguous Antarctic Peninsula form a southward extension of the Chon Aike province and are also dominated by silicic ignimbrite units, with a total thickness exceeding 1 km. The ignimbrites include high-grade rheomorphic ignimbrites, as well as unwelded, lithic-rich ignimbrites. Rhyolite lava flows, air-fall horizons, debris-flow deposits and epiclastic deposits are volumetrically minor, occurring as interbedded units within the ignimbrite succession.

scholarly journals A revised geochronology of Thurston Island, West Antarctica, and correlations along the proto-Pacific margin of Gondwana

2016 ◽  
Vol 29 (1) ◽  
pp. 47-60 ◽  
Author(s):  
T.R. Riley ◽  
M.J. Flowerdew ◽  
R.J. Pankhurst ◽  
P.T. Leat ◽  
I.L. Millar ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
West Antarctica ◽  
Granitoid Magmatism ◽  
Andean Cordillera ◽  
Crustal Block ◽  
Form Part ◽  
Gondwana Margin ◽  
Pacific Margin ◽  
Mesozoic Magmatism ◽  
The Antarctic

AbstractThe continental margin of Gondwana preserves a record of long-lived magmatism from the Andean Cordillera to Australia. The crustal blocks of West Antarctica form part of this margin, with Palaeozoic–Mesozoic magmatism particularly well preserved in the Antarctic Peninsula and Marie Byrd Land. Magmatic events on the intervening Thurston Island crustal block are poorly defined, which has hindered accurate correlations along the margin. Six samples are dated here using U-Pb geochronology and cover the geological history on Thurston Island. The basement gneisses from Morgan Inlet have a protolith age of 349±2 Ma and correlate closely with the Devonian–Carboniferous magmatism of Marie Byrd Land and New Zealand. Triassic (240–220 Ma) magmatism is identified at two sites on Thurston Island, with Hf isotopes indicating magma extraction from Mesoproterozoic-age lower crust. Several sites on Thurston Island preserve rhyolitic tuffs that have been dated at 182 Ma and are likely to correlate with the successions in the Antarctic Peninsula, particularly given the pre-break-up position of the Thurston Island crustal block. Silicic volcanism was widespread in Patagonia and the Antarctic Peninsula at ~ 183 Ma forming the extensive Chon Aike Province. The most extensive episode of magmatism along the active margin took place during the mid-Cretaceous. This Cordillera ‘flare-up’ event of the Gondwana margin is also developed on Thurston Island with granitoid magmatism dated in the interval 110–100 Ma.

Large volume silicic volcanism along the proto-Pacific margin of Gondwana: lithological and stratigraphical investigations from the Antarctic Peninsula

1999 ◽  
Vol 136 (1) ◽  
pp. 1-16 ◽  
Author(s):  
TEAL R. RILEY ◽  
PHILIP T. LEAT
Keyword(s):  
Antarctic Peninsula ◽  
Middle Jurassic ◽  
East Coast ◽  
Volcanic Rocks ◽  
Lower Jurassic ◽  
Fossil Flora ◽  
Metasedimentary Rocks ◽  
Close Relationship ◽  
Pacific Margin ◽  
The Antarctic

Jurassic magmatism in western Gondwana produced the most voluminous episode of continental volcanism in the Phanerozoic era. During the Early to Middle Jurassic, some 2.5–3 million km3 of dominantly basalt, and to a lesser extent rhyolite, were erupted onto a supercontinent in the early stages of break-up. The major silicic portion of the Gondwana magmatic province is exposed in Patagonian South America. The volcanic rocks of Patagonia have been collectively termed the Chon-Aike Province and constitute one of the world's most voluminous silicic provinces. The volcanic rocks are predominantly pyroclastic, dominated by ignimbrite units of rhyolite composition. Volcanic rocks crop out sporadically across much of the once contiguous Antarctic Peninsula, and are considered to form an extension of the Chon-Aike Province. A continuation of the province to include the Antarctic Peninsula would extend its strike length along the active Pacific margin by c. 2000 km.Volcanic rocks exposed along the east coast of the Antarctic Peninsula, defined here as the Mapple Formation, are also dominated by rhyolitic ignimbrite flows, with individual units up to 80 m in thickness, and a total thickness of c. 1 km. The ignimbrites vary in degree of welding, from high-grade rheomorphic ignimbrites with parataxitic textures, to unwelded, lithic-rich ignimbrites. Rhyolite lava flows, air-fall horizons, debris flow deposits and epiclastic deposits are volumetrically minor, occurring as interbedded units within the ignimbrite succession.The lithology and stratigraphy of the Jurassic volcanic rocks of the Mapple Formation are presented, and comparisons are made to the Chon-Aike Province. A consistent stratigraphy of Permo-Triassic metasedimentary rocks, unconformably overlain by terrestrial mudstone–siltstone sequences, which are in turn conformably overlain by largely silicic, subaerial volcanic rocks, is present at several localities along the Antarctic Peninsula, and at localities in the Chon-Aike Province. Precise (zircon U–Pb) Middle Jurassic ages exist for two volcanic formations from the Antarctic Peninsula, and a Middle–Lower Jurassic age has been suggested for the underlying sedimentary formations based on fossil flora analysis. The Antarctic Peninsula chronostratigraphy, coupled with lithological similarities, indicate a close relationship to those sequences of the Chon-Aike province.

scholarly journals Zircon U-Pb dating of Mesozoic volcanic and tectonic events in north-west Palmer Land and south-west Graham Land, Antarctica

2009 ◽  
Vol 21 (6) ◽  
pp. 633-641 ◽  
Author(s):  
P.T. Leat ◽  
M.J. Flowerdew ◽  
T.R. Riley ◽  
M.J. Whitehouse ◽  
J.H. Scarrow ◽  
...  
Keyword(s):  
Antarctic Peninsula ◽  
Volcanic Rocks ◽  
Geochronological Data ◽  
Zircon Age ◽  
North West ◽  
Magmatic Arc ◽  
Tectonic Events ◽  
South West ◽  
Silicic Volcanic ◽  
The Antarctic

AbstractNew whole rock Rb-Sr and zircon U-Pb geochronological data and Sm-Nd isotopic data are presented from the central magmatic arc domain of the Antarctic Peninsula in the area of north-west Palmer Land and south-west Graham Land, Rb-Sr isochrons indicate an age of 169 ± 6 Ma for basement orthogneisses and 132 ± 9 to 71 ± 9 Ma for plutons. A U-Pb age of 183 ± 2.1 Ma, with no detectable inheritance, on zircons from an orthogneiss from Cape Berteaux provides the first reliable age for the orthogneisses, which are interpreted as metamorphosed silicic volcanic rocks, and Sm-Nd data indicate derivation in a mature volcanic arc. The age indicates they may be correlatives of the Jurassic ‘Chon Aike’ volcanism of the eastern Antarctic Peninsula. A U-Pb zircon age of 107 ± 1.7 Ma on a terrestrial volcanic sequence overlying an uncomformity strongly suggests a mid-Cretaceous age for the extensive volcanic cover of north-west Palmer Land that was previously thought to be Jurassic. The unconformity is interpreted to have been a result of compressional uplift related to the Palmer Land event. This is the first date for the event in the western part of the central magmatic arc terrane of the Antarctic Peninsula.

Tectonic setting and geochemistry of Miocene alkalic basalts from the Jones Mountains, West Antarctica

1994 ◽  
Vol 6 (1) ◽  
pp. 85-92 ◽  
Author(s):  
M. J. Hole ◽  
B. C. Storey ◽  
W. E. LeMasurier
Keyword(s):  
Antarctic Peninsula ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
West Antarctica ◽  
Geochemical Composition ◽  
Crustal Block ◽  
Volcaniclastic Rocks ◽  
Geochemical Analyses ◽  
The Antarctic ◽  
Alkalic Basalts

Within the Jones Mountains, which form part of the Thurston Island crustal block, up to 700 m of Miocene (c. 10 Ma) pillow basalt and palagonitized volcaniclastic rocks unconformably overlie Jurassic granitic basement and Cretaceous volcanic rocks and dykes. New geochemical analyses demonstrate the alkalic nature of the basalts, which range in composition from alkali basalt to basanite. Unradiogenic Sr-isotope ratios (0.7031–0.7034), coupled with low LILE/HFSE ratios (e.g. Th/Ta c. 1.4, Rb/Nb 0.3–0.9) indicate a predominantly asthenospheric source for the basalts. The Jones Mountains basalts are geochemically similar to the alkalic basalts of Marie Byrd Land, but have consistently lower K/Ba and higher Ba/Nb ratios than Late Cenozoic alkalic basalts along the Antarctic Peninsula. These regional variations in geochemical composition apparently reflect differences in tectonic setting and are not the result of lithospheric interaction or partial melting/crystallization effects. The generation of alkalic magmas along the Antarctic Peninsula was causally related to the formation of slab windows following ridge crest-trench collision and the cessation of subduction, whereas the Jones Mountains alkalic basalts may represent the expression of the northward propagation of the head of the Marie Byrd Land plume.

Middle Jurassic rhyolite volcanism of eastern Graham Land, Antarctic Peninsula: age correlations and stratigraphic relationships

2010 ◽  
Vol 147 (4) ◽  
pp. 581-595 ◽  
Author(s):  
TEAL R. RILEY ◽  
MICHAEL J. FLOWERDEW ◽  
MORAG A. HUNTER ◽  
MARTIN J. WHITEHOUSE
Keyword(s):  
Antarctic Peninsula ◽  
East Coast ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Silicic Volcanism ◽  
Volcanic Group ◽  
Silicic Volcanic ◽  
Eruption Age ◽  
Rhyolite Volcanism ◽  
The Antarctic

AbstractSilicic volcanism atc.168 Ma has been identified previously on the Antarctic Peninsula, and the Mapple Formation, which includes those volcanic rocks, has been defined and documented from one area of the east coast of Graham Land. Based on age and geochemical criteria, correlations have been made to the extensive Chon Aike Province of South America, which has been demonstrated to be one of the largest silicic volcanic provinces in the world. Rhyolitic and intermediate composition volcanic successions from six separate localities on the east coast of the Antarctic Peninsula are described here and are confirmed as correlatives of the Mapple Formation, based on newly acquired geochronology and field observations. They are dominantly rhyolitic crystal tuffs and/or ignimbrites with ages in the interval 162–168 Ma, overlapping with the age of the Mapple Formation (167–171 Ma) at the type locality. Andesitic agglomerates are also described, which are included in the same event and demonstrate the occurrence of rare intermediate volcanism, which is also seen in the Chon Aike Province. A new group, the Graham Land Volcanic Group, is defined here, and criteria are established which allow the separation of some volcanic successions out of the previously defined Antarctic Peninsula Volcanic Group, which takes no account of tectonic setting, eruption age or geochemistry.

scholarly journals Mass balance of the Antarctic ice sheet 1992–2016: reconciling results from GRACE gravimetry with ICESat, ERS1/2 and Envisat altimetry

2021 ◽  
pp. 1-27
Author(s):  
H. Jay Zwally ◽  
John W. Robbins ◽  
Scott B. Luthcke ◽  
Bryant D. Loomis ◽  
Frédérique Rémy
Keyword(s):  
Mass Balance ◽  
Antarctic Peninsula ◽  
East Antarctica ◽  
Mantle Material ◽  
West Antarctica ◽  
Mantle Viscosity ◽  
Grounding Line ◽  
The Antarctic ◽  
Total Gain

Abstract GRACE and ICESat Antarctic mass-balance differences are resolved utilizing their dependencies on corrections for changes in mass and volume of the same underlying mantle material forced by ice-loading changes. Modeled gravimetry corrections are 5.22 times altimetry corrections over East Antarctica (EA) and 4.51 times over West Antarctica (WA), with inferred mantle densities 4.75 and 4.11 g cm−3. Derived sensitivities (Sg, Sa) to bedrock motion enable calculation of motion (δB0) needed to equalize GRACE and ICESat mass changes during 2003–08. For EA, δB0 is −2.2 mm a−1 subsidence with mass matching at 150 Gt a−1, inland WA is −3.5 mm a−1 at 66 Gt a−1, and coastal WA is only −0.35 mm a−1 at −95 Gt a−1. WA subsidence is attributed to low mantle viscosity with faster responses to post-LGM deglaciation and to ice growth during Holocene grounding-line readvance. EA subsidence is attributed to Holocene dynamic thickening. With Antarctic Peninsula loss of −26 Gt a−1, the Antarctic total gain is 95 ± 25 Gt a−1 during 2003–08, compared to 144 ± 61 Gt a−1 from ERS1/2 during 1992–2001. Beginning in 2009, large increases in coastal WA dynamic losses overcame long-term EA and inland WA gains bringing Antarctica close to balance at −12 ± 64 Gt a−1 by 2012–16.

scholarly journals An Assessment of ERA5 Reanalysis for Antarctic Near-Surface Air Temperature

Atmosphere ◽  
2021 ◽  
Vol 12 (2) ◽  
pp. 217
Author(s):  
Jiangping Zhu ◽  
Aihong Xie ◽  
Xiang Qin ◽  
Yetang Wang ◽  
Bing Xu ◽  
...  
Keyword(s):  
Linear Relationship ◽  
Antarctic Peninsula ◽  
Austral Summer ◽  
Correlation Coefficients ◽  
East Antarctica ◽  
West Antarctica ◽  
Austral Spring ◽  
Reanalysis Dataset ◽  
Near Surface ◽  
The Antarctic

The European Center for Medium-Range Weather Forecasts (ECMWF) released its latest reanalysis dataset named ERA5 in 2017. To assess the performance of ERA5 in Antarctica, we compare the near-surface temperature data from ERA5 and ERA-Interim with the measured data from 41 weather stations. ERA5 has a strong linear relationship with monthly observations, and the statistical significant correlation coefficients (p < 0.05) are higher than 0.95 at all stations selected. The performance of ERA5 shows regional differences, and the correlations are high in West Antarctica and low in East Antarctica. Compared with ERA5, ERA-Interim has a slightly higher linear relationship with observations in the Antarctic Peninsula. ERA5 agrees well with the temperature observations in austral spring, with significant correlation coefficients higher than 0.90 and bias lower than 0.70 °C. The temperature trend from ERA5 is consistent with that from observations, in which a cooling trend dominates East Antarctica and West Antarctica, while a warming trend exists in the Antarctic Peninsula except during austral summer. Generally, ERA5 can effectively represent the temperature changes in Antarctica and its three subregions. Although ERA5 has bias, ERA5 can play an important role as a powerful tool to explore the climate change in Antarctica with sparse in situ observations.

Chapter 3.1b Antarctic Peninsula and South Shetland Islands: petrology

2021 ◽  
pp. M55-2018-68 ◽  
Author(s):  
Philip T. Leat ◽  
Teal R. Riley
Keyword(s):  
Antarctic Peninsula ◽  
Continental Margin ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Contact Metamorphism ◽  
South Shetland Islands ◽  
Calc Alkaline ◽  
The Pacific ◽  
High K ◽  
The Antarctic

AbstractThe Antarctic Peninsula contains a record of continental-margin volcanism extending from Jurassic to Recent times. Subduction of the Pacific oceanic lithosphere beneath the continental margin developed after Late Jurassic volcanism in Alexander Island that was related to extension of the continental margin. Mesozoic ocean-floor basalts emplaced within the Alexander Island accretionary complex have compositions derived from Pacific mantle. The Antarctic Peninsula volcanic arc was active from about Early Cretaceous times until the Early Miocene. It was affected by hydrothermal alteration, and by regional and contact metamorphism generally of zeolite to prehnite–pumpellyite facies. Distinct geochemical groups recognized within the volcanic rocks suggest varied magma generation processes related to changes in subduction dynamics. The four groups are: calc-alkaline, high-Mg andesitic, adakitic and high-Zr, the last two being described in this arc for the first time. The dominant calc-alkaline group ranges from primitive mafic magmas to rhyolite, and from low- to high-K in composition, and was generated from a mantle wedge with variable depletion. The high-Mg and adakitic rocks indicate periods of melting of the subducting slab and variable equilibration of the melts with mantle. The high-Zr group is interpreted as peralkaline and may have been related to extension of the arc.

Ultramafic mantle xenoliths in the Late Cenozoic Volcanic rocks of the Antarctic Peninsula and Jones Mountains, West Antarctica

2021 ◽  
pp. M56-2019-44
Author(s):  
Philip T. Leat ◽  
Aidan J. Ross ◽  
Sally A. Gibson
Keyword(s):  
Antarctic Peninsula ◽  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Volcanic Rocks ◽  
Oceanic Lithosphere ◽  
Incompatible Trace Element ◽  
Mantle Xenoliths ◽  
South Shetland Islands ◽  
West Antarctica ◽  
Gondwana Margin

AbstractAbundant mantle-derived ultramafic xenoliths occur in Cenozoic (7.7-1.5 Ma) mafic alkaline volcanic rocks along the former active margin of West Antarctica, that extends from the northern Antarctic Peninsula to Jones Mountains. The xenoliths are restricted to post-subduction volcanic rocks that were emplaced in fore-arc or back-arc positions relative to the Mesozoic-Cenozoic Antarctic Peninsula volcanic arc. The xenoliths are spinel-bearing, include harzburgites, lherzolites, wehrlites and pyroxenites, and provide the only direct evidence of the composition of the lithospheric mantle underlying most of the margin. The harzburgites may be residues of melt extraction from the upper mantle (in a mid-ocean ridge type setting), that accreted to form oceanic lithosphere, which was then subsequently tectonically emplaced along the active Gondwana margin. An exposed highly-depleted dunite-serpentinite upper mantle complex on Gibbs Island, South Shetland Islands, supports this interpretation. In contrast, pyroxenites, wehrlites and lherzolites reflect percolation of mafic alkaline melts through the lithospheric mantle. Volatile and incompatible trace element compositions imply that these interacting melts were related to the post-subduction magmatism which hosts the xenoliths. The scattered distribution of such magmatism and the history of accretion suggest that the dominant composition of sub-Antarctic Peninsula lithospheric mantle is likely to be harzburgitic.

Chapter 4.1b Antarctic Peninsula: petrology

2021 ◽  
pp. M55-2018-40
Author(s):  
Malcolm J. Hole
Keyword(s):  
Antarctic Peninsula ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Passive Margin ◽  
Ridge Crest ◽  
Ridge Subduction ◽  
Simple Geometry ◽  
Key Issues ◽  
The Antarctic ◽  
Slab Window

AbstractScattered occurrences of Miocene–Recent volcanic rocks of the alkaline intraplate association represent one of the last expressions of magmatism along the Antarctic Peninsula. The volcanic rocks were erupted after the cessation of subduction which stopped following a series of northward-younging ridge crest–trench collisions. Volcanism has been linked to the development of a growing slab window beneath the extinct convergent margin. Geochemically, lavas range from olivine tholeiite through to basanite and tephrite. Previous studies have emphasized the slab-window tectonic setting as key to allowing melting of peridotite in the asthenospheric void caused by the passage of the slab beneath the locus of volcanism. This hypothesis is revisited in the light of more recent petrological research, and an origin from melting of subducted slab-hosted pyroxenite is considered here to be a more viable alternative for their petrogenesis. Because of the simple geometry of ridge subduction, and the well-established chronology of ridge crest–trench collisions, the Antarctic Peninsula remains a key region for understanding the transition from active to passive margin resulting from cessation of subduction. However, there are still some key issues relating to their tectonomagmatic association, and, principally, the poor geochronological control on the volcanic rocks requires urgent attention.

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