A unifying lithostratigraphy of late Cretaceous–early Tertiary fore-arc volcanic sequences on Alexander Island, Antarctica

1997 ◽  
Vol 9 (2) ◽  
pp. 209-220 ◽  
Author(s):  
Joe J. McCarron
Keyword(s):  
Antarctic Peninsula ◽  
Late Cretaceous ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Magmatic Arc ◽  
Ridge Subduction ◽  
Volcanic Group ◽  
Early Tertiary ◽  
Plutonic Rocks ◽  
The Antarctic

Late Cretaceous–early Tertiary subduction-related fore-arc volcanic rocks are exposed in a north–south linear belt along the length of Alexander Island. The age and tectonic setting of these rocks is well understood; they are not considered to represent “normal” arc magmas but were generated in the fore-arc as a result of ridge subduction. Due to their distinct composition and mode of formation, they are no longer considered to be genetically related to the Antarctic Peninsula magmatic arc. They are therefore removed from the Antarctic Peninsula Volcanic Group and placed in a newly defined Alexander Island Volcanic Group. The group is made up of the Monteverdi, Staccato, Walton, Colbert, Elgar and Finlandia formations, which vary widely in lithology, facies and age. The Colbert and Elgar formations are subdivided into nine and three members respectively. Type localities, representative lithologies and age of each of the formations are discussed. The Staccato and Colbert Magmatic complexes are defined to include volcanic and plutonic rocks that are considered to be coeval. The Rouen Intrusive complex combines the plutonic rocks from the Rouen Mountains and Rothschild Island on the basis of age and chemistry.

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.

Central volcanoes as sources for the Antarctic Peninsula Volcanic Group

1994 ◽  
Vol 6 (3) ◽  
pp. 365-374 ◽  
Author(s):  
Philip T. Leat ◽  
Jane H. Scarrow
Keyword(s):  
Antarctic Peninsula ◽  
Volcanic Rocks ◽  
Coarse Grained ◽  
North West ◽  
Magmatic Arc ◽  
Fine Grained ◽  
Volcanic Group ◽  
Land Sliding ◽  
High Level ◽  
The Antarctic

From at least the Early Jurassic to the Miocene, eastward subduction of oceanic crust took place beneath the Antarctic Peninsula. Magmatism associated with the subduction generated a N-S linear belt of volcanic rocks known as the Antarctic Peninsula Volcanic Group (APVG), and which erosion has now exposed at about the plutonic/volcanic interface. Large central volcanoes from the APVG are described here for the first time. The structures are situated in north-west Palmer Land within the main Mesozoic magmatic arc. One centre, Zonda Towers, is recognized by the presence of a 160 m thick silicic ignimbrite, containing accidental lava blocks up to 25 m in diameter. This megabreccia is interpreted as a caldera-fill deposit which formed by land sliding of steep caldera walls during ignimbrite eruption and deposition. A larger centre, Mount Edgell-Wright Spires, is dominated by coarse-grained debris flow deposits and silicic ignimbrites which, with minor lavas and fine-grained tuffs, form a volcanic succession some 1.5 km thick. Basic intermediate and silicic sills c. 50 m thick intrude the succession. A central gabbro-granite intrusion is interpreted to be a high-level magma chamber of the Mount Edgell volcano.

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 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.

Oceanic crust generation in an island arc tectonic setting, SE Anatolian orogenic belt (Turkey)

2004 ◽  
Vol 141 (5) ◽  
pp. 583-603 ◽  
Author(s):  
OSMAN PARLAK ◽  
VOLKER HÖCK ◽  
HÜSEYİN KOZLU ◽  
MICHEL DELALOYE
Keyword(s):  
Late Cretaceous ◽  
Subduction Zones ◽  
Wide Spectrum ◽  
Tectonic Setting ◽  
Volcanic Rocks ◽  
Orogenic Belt ◽  
Mature Stage ◽  
Magmatic Arc ◽  
The North ◽  
Suprasubduction Zone

A number of Late Cretaceous ophiolitic bodies are located between the metamorphic massifs of the southeast Anatolian orogenic system. One of them, the Göksun ophiolite (northern Kahramanmaraş), which crops out in a tectonic window bounded by the Malatya metamorphic units on both the north and south, is located in the EW-trending nappe zone of the southeast Anatolian orogenic belt between Göksun and Afşin (northern Kahramanmaraş). It consists of ultramafic–mafic cumulates, isotropic gabbro, a sheeted dyke complex, plagiogranite, volcanic rocks and associated volcanosedimentary units. The ophiolitic rocks and the tectonically overlying Malatya–Keban metamorphic units were intruded by syn-collisional granitoids (∼ 85 Ma). The volcanic units are characterized by a wide spectrum of rocks ranging in composition from basalt to rhyolite. The sheeted dykes consist of diabase and microdiorite, whereas the isotropic gabbros consist of gabbro, diorite and quartzdiorite. The magmatic rocks in the Göksun ophiolite are part of a co-magmatic differentiated series of subalkaline tholeiites. Selective enrichment of some LIL elements (Rb, Ba, K, Sr and Th) and depletion of the HFS elements (Nb, Ta, Ti, Zr) relative to N-MORB are the main features of the upper crustal rocks. The presence of negative anomalies for Ta, Nb, Ti, the ratios of selected trace elements (Nb/Th, Th/Yb, Ta/Yb) and normalized REE patterns all are indicative of a subduction-related environment. All the geochemical evidence both from the volcanic rocks and the deeper levels (sheeted dykes and isotropic gabbro) show that the Göksun ophiolite formed during the mature stage of a suprasubduction zone (SSZ) tectonic setting in the southern branch of the Neotethyan ocean between the Malatya–Keban platform to the north and the Arabian platform to the south during Late Cretaceous times. Geological, geochronological and petrological data on the Göksun ophiolite and the Baskil magmatic arc suggest that there were two subduction zones, the first one dipping beneath the Malatya–Keban platform, generating the Baskil magmatic arc and the second one further south within the ocean basin, generating the Göksun ophiolite in a suprasubduction zone environment.

scholarly journals Chrono- and lithostratigraphy of a Mesozoic–Tertiary fore- to intra-arc basin: Adelaide Island, Antarctic Peninsula

2011 ◽  
Vol 149 (5) ◽  
pp. 768-782 ◽  
Author(s):  
TEAL R. RILEY ◽  
MICHAEL J. FLOWERDEW ◽  
MARTIN J. WHITEHOUSE
Keyword(s):  
Antarctic Peninsula ◽  
Basaltic Andesite ◽  
West Coast ◽  
Volcanic Rocks ◽  
Volcanic Group ◽  
Volcaniclastic Rocks ◽  
Definition Of ◽  
The Antarctic ◽  
Adelaide Island

AbstractThe Mesozoic fore-arc of the Antarctic Peninsula is exposed along its west coast. On Adelaide Island, a 2–3 km succession of turbiditic coarse sandstones and volcanic rocks is exposed. Four U–Pb (zircon) ages are presented here that, in combination with a new stratigraphy, have permitted a robust chrono- and lithostratigraphy to be constructed, which in turn has allowed tentative correlations to be made with the Fossil Bluff Group of Alexander Island, where the ‘type’ fore-arc sequences are described. The lithostratigraphy of Adelaide Island includes the definition of five volcanic/sedimentary formations. The oldest formation is the Buchia Buttress Formation (149.5 ± 1.6 Ma) and is correlated with the Himalia Ridge Formation of Alexander Island. The sandstone–conglomerate dominated succession of the Milestone Bluff Formation (113.9 ± 1.2 Ma) is tentatively correlated with the Pluto Glacier Formation of Alexander Island. Three dominantly volcanic formations are recognized on Adelaide Island, akin to the volcanic rocks of the Alexander Island Volcanic Group; the Mount Liotard Formation is formed of 2 km of basaltic andesite lavas, whilst the Bond Nunatak Formation is also dominated by basaltic andesite lavas, but interbedded with volcaniclastic rocks. The Reptile Ridge Formation has been dated at 67.6 ± 0.7 Ma and is characterized by hydrothermally altered rhyolitic crystal-lithic tuffs. Tentative correlations between Adelaide Island and Alexander Island preclude the two areas forming part of distinct terranes as has been suggested previously, and a proximal source for volcaniclastic sediments also indicates an exotic terrane origin is unlikely.

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.

The geology of Cape Dubouzet, northern Antarctic Peninsula: continental basement to the Trinity Peninsula Group?

1996 ◽  
Vol 8 (4) ◽  
pp. 407-414 ◽  
Author(s):  
Francisco Hervé ◽  
Jorge Lobato ◽  
Ignacio Ugalde ◽  
Robert J. Pankhurst
Keyword(s):  
Antarctic Peninsula ◽  
Late Jurassic ◽  
Volcanic Rocks ◽  
Metamorphic Rocks ◽  
Low Grade ◽  
Metamorphic Complex ◽  
Calc Alkaline ◽  
Magmatic Arc ◽  
The Antarctic ◽  
The Trinity

Cape Dubouzet is mainly composed of a volcanic-subvolcanic complex of extrusive rhyolitic breccias, a banded rhyolite and a semi-annular body of dacite porphyry rich in xenoliths of metamorphic rocks. Major and REE geochemistry indicate that the volcanic rocks are calc-alkaline and that they are genetically related by fractional crystallization of a plagioclase-bearing assemblage from a common magma. Rb-Sr data suggest that the rhyolitic complex is of Middle-to-Late Jurassic age, and that it is intruded by Late Cretaceous stocks of banded diorite and gabbro. All these rocks are partially covered by moraines whose clasts are of local provenance. Xenoliths in the dacite porphyry suggest that the northern tip of the Antarctic Peninsula is underlain by a metamorphic complex composed of amphibolites, meta-tonalites and pelitic gneiss containing garnet, sillimanite, cordierite, hercynite, and andalucite. Such rocks are not known in the Scotia metamorphic complex, nor in the Trinity Peninsula Group and its low grade metamorphic derivatives, which also occur as rare xenoliths in the dacite. Previous dating of xenoliths collected from the moraines suggested a late Carboniferous age for this amphibolite-grade metamorphism. Both the Jurassic-Cenozoic magmatic arc of the Antarctic Peninsula and the accretionary complex rocks of the Trinity Peninsula Group were thus developed, at least in part, over pre-existing continental crust.

A complete arc-trench system recognized in Gondwana sequences of the Antarctic Peninsula region

1981 ◽  
Vol 118 (2) ◽  
pp. 139-159 ◽  
Author(s):  
J. L. Smellie
Keyword(s):  
South Africa ◽  
Antarctic Peninsula ◽  
Volcanic Rocks ◽  
Foreland Basin ◽  
Early Jurassic ◽  
Radiometric Dating ◽  
Late Triassic ◽  
Magmatic Arc ◽  
Complete Arc ◽  
The Antarctic

SummaryPrior to Late Triassic–Early Jurassic times, the geological history of the Antarctic Peninsula region was dominated almost entirely by Gondwana sequences that together comprised a major arc-trench system. Subduction complex, trench-slope-break and fore-arc basin sedimentation can all be recognized, and deposition was at least partly on early Palaeozoic or older continental crust. The only evidence for a contemporaneous magmatic arc situated in the Antarctic Peninsula at this time consists of patchy occurrences of metavolcanic rocks, possibly representing the frontal edge of the arc, and the major outcrop area of these rocks is believed to lie under the broad shallow continental shelf E of the Antarctic Peninsula. This is contrary to most current hypotheses in which a marginal basin, presumably floored by oceanic crust, is thought to crop out close to the E coast of the Antarctic Peninsula. However, the complete absence of substantial outcrops of pre-Jurassic volcanic rocks anywhere in eastern Antarctica and South Africa, which are the closest and most likely places in which these should exist, supports the new proposal. Moreover, the identification of back-arc elements of the arc-trench system (foreland fold-thrust belt and retro-arc foreland basin) in eastern Antarctica and South Africa greatly strengthens the likelihood of the arc cropping out in the area suggested.Towards the end of the Triassic and during the Early Jurassic Periods, an intense diastrophic event, or culmination of events, of orogenic magnitude occurred (Gondwanian orogeny), causing substantial redistribution of the pre-existing elements of the arc-trench system. In particular, all the fore-arc sequences were strongly deformed, some possibly for the first time (e.g. in the fore-arc basin), and became firmly accreted to the continental margin. Moreover, the magmatic foci migrated trenchwards to intrude the deformed rocks in the Antarctic Peninsula. Because many of the plutons were emplaced synkinematically, they often closely resemble ‘basement’ gneisses. The distinction between these rocks remains a serious problem in the Antarctic Peninsula and it can be solved only partially by radiometric dating.

The age and stratigraphy of fore-arc magmatism on Alexander Island, Antarctica

1997 ◽  
Vol 134 (4) ◽  
pp. 507-522 ◽  
Author(s):  
JOE J. MCCARRON ◽  
IAN L. MILLAR
Keyword(s):  
Antarctic Peninsula ◽  
Volcanic Rocks ◽  
Arc Magmatism ◽  
Final Phase ◽  
Pyroclastic Deposits ◽  
Magmatic Arc ◽  
Magmatic Rocks ◽  
Zircon Fission Track ◽  
Cretaceous Magmatism ◽  
The Antarctic

Fore-arc magmatic sequences associated with high Mg number andesite lavas unconformably overlie LeMay Group accretionary complex in Alexander Island. High-resolution 40Ar/39Ar, U–Pb zircon, fission track and K–Ar ages demonstrate that subduction-related fore-arc magmatism migrated northwards along the length of Alexander Island between c. 80 Ma and c. 46 Ma. The magmatic rocks represent a third of the western margin of the Antarctic Peninsula magmatic arc and are critical to the understanding of the final phase of subduction along the southern Antarctic Peninsula margin. The onset of late Cretaceous magmatism is recorded by poorly exposed volcanic rocks on Monteverdi Peninsula (79.7±2.5 Ma). In central and northern Alexander Island, the magmatic rocks can be distinguished by the proportion, range and types of lithofacies present, and by the periods of magmatism represented. The volcanic rocks of the Colbert Mountains range in age from c. 69–62 Ma and are dominated by large volume dacitic and rhyolitic crystal-rich ignimbrites interpreted as caldera-fill deposits. Elgar Uplands sequences range in age from c. 55–50 Ma, and contain approximately equal proportions of pyroclastic deposits and less evolved (basaltic-andesite and andesite) lavas including high Mg number andesite lavas near the base of three sequences. The volcanic rocks of Finlandia Foothills probably represent the youngest calc-alkaline units on Alexander Island (48±2 Ma). The sequence is lithologically similar to the Elgar Uplands and also contains high Mg number andesite lavas, but it is dominated by polymict conglomerates, with minor lavas, which were deposited in a graben associated with regional extension. Plutonic rocks exposed in the Rouen Mountains, adjacent to the Elgar Uplands, yielded a U–Pb age of 56±3 Ma which is in discordance with a previously published Rb–Sr age (46±3 Ma), probably due to hydrothermal perturbation of the Rb–Sr system. Northwards migration of magmatism was caused by the progressive collision and subduction of three ridge segments prior to the previously reported ridge crest–trench collisions that occurred c. 20–30 Ma later and following which subduction ceased.

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