The role of crustal and mantle sources in the genesis of granitoids of the Antarctic Peninsula and adjacent crustal blocks

Millar, Ian L.; Willan, Robert C. R.; Wareham, Christopher D.; Boyce, Adrian J.

doi:10.1144/0016-764900-139

Cited by 51 publications

(54 citation statements)

References 49 publications

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“…All the values, except for C142 (εNd i =5.18), lie within the range of previous analyses from granites and grandiorites from the Palmer Land ( Fig. 8) (Millar et al, 2001). Overall, the clasts scatter around an Rb-Sr reference isochron of c. 143 Ma, approximately in the middle of the 90-200 Ma age range of rocks from Alexander Island and Palmer Land (Table 3).…”

Section: Clast Geochemistry Isotopic Composition and Provenancesupporting

confidence: 83%

“…Their isotopic composition is compatible with Late Jurassic-Early Cretaceous plutonic rocks from NW Palmer Land (Fig. 8) (Wareham et al, 1997;Millar et al, 2001) and outcrops with similar petrology in northern Palmer Land (Smith, 1987).…”

Section: Volcanic Clastssupporting

confidence: 62%

“…8; (Fig. 8) (Millar et al, 2001). In contrast, Group 3 rhyolites Several factors indicate that Group 3 rhyolites are most likely eroded from the ML catchment: (i) the simultaneous input of Group 3 rhyolites and Group 1/7 clasts in Zone 5 of the ML core, (ii) their lack of striations, less well-rounded shape, the small proportion of Group 3 weathered rhyolites (10% vs 18%) relative to Group 2 rhyolites (Table 2), (iii) a possible shift from Group 2 to Group 3 rhyolites in the AB core (iv) an absence of Group 2 rhyolites in all but the basal 5 cm of the AB core.…”

Section: Volcanic Clastsmentioning

confidence: 99%

“…Groups 1/7, 2, 3) reflect the age and location of source volcanism. Late Jurassic-Early Cretaceous (141-127 Ma) granitoid rocks of the western Palmer Land Central Domain are derived from the mantle, or by melting of underplate, and have low initial Sr ratios and high εNd i values, while older rocks, which have assimilated continental crust, have higher initial Sr ratios and lower/negative εNd i values (Millar et al, 2001). Rb-Sr and Nd isotope data indicate that these clast types probably originated from volcanic rocks from in Palmer Land, most likely during a period of widespread and intensive Early Cretaceous arc-related volcanism at around 140 Ma.…”

Section: Primary Clastsmentioning

confidence: 99%

“…Rb-Sr and Nd isotope data indicate that these clast types probably originated from volcanic rocks from in Palmer Land, most likely during a period of widespread and intensive Early Cretaceous arc-related volcanism at around 140 Ma. (Millar et al, 2001). All non igneous clasts and sediments sand-silt fraction sediments from the ML core plot in either arc related or active continental margin fields (Bhatia, 1983;Roser and Korsch, 1986).…”

Section: Primary Clastsmentioning

confidence: 99%

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The Holocene history of George VI Ice Shelf, Antarctic Peninsula from clast-provenance analysis of epishelf lake sediments

Hodgson

Bentley

et al. 2008

Palaeogeography, Palaeoclimatology, Palaeoecology

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The Antarctic Peninsula has experienced a dramatic increase in temperature and the loss of c. 14,000 km 2 of ice-shelf area in recent years. During this time George VI Ice Shelf (GVIIS) has remained relatively intact, but is now reaching its theoretical limit of viability. Epishelf lakes, formed when ice shelves dam the mouths of marine embayments, accumulate sediments that can be used to constrain past ice-shelf behaviour. They are stratified water bodies with an upper layer of fresh melt-water overlying a marine layer of water. Multi-proxy analysis of a sediment core from Moutonnée Lake, an epishelf lake dammed by GVIIS on the east coast of Alexander Island, has recently shown that it retreated to at least the Ablation Point area in the early Holocene, c. 9600-7500 yr BP, demonstrating its vulnerability to periods of atmospheric and oceanic warmth. This study tests this interpretation of ice-shelf collapse through detailed analyses of granulometric, geochemical and Sr and Nd isotope provenance data for >8 mm clasts from the same cores. Clast data from Moutonnée Lake were compared with geological reference data from two further lakes on Alexander Island (Ablation Lake and Citadel Bastion Lake) and an extensive archive of rocks and isotope geochemical provenance data from the Antarctic Peninsula region. Underpinning this provenance analysis is the contrast between the plutonic/igneous outcrops in Palmer Land on the western side and the predominantly sedimentary strata of Alexander Island on the eastern side of George VI Sound, and the different patterns in their deposition that would be expected at Moutonnée Lake during periods of ice shelf presence and absence. Results show that changes in clast distribution and provenance reflect the early Holocene retreat and reformation of George VI Ice Shelf at Moutonnée Lake. The period of ice shelf retreat was marked by the onset of marine conditions in the basin followed by a rapidly deposited zone of clasts whose provenance, distribution, varied lithology and larger than average clast size are indicative of a period of lake-ice disintegration and ice-rafted debris deposition between c. 9600-8450 yr BP. Igneous clasts in the ice-rafted debris have a close affinity with the plutonic provinces of western Palmer Land suggesting transport to the site by icebergs or recycling through Alexander Island strata/moraines. When epishelf lake conditions returned after c. 7500 yr BP, the clasts were smaller, the number of lithologies more limited and the assemblage dominated by olive-green vitric tuff and pale-green rhyolitic clasts that isotope data link to Early Cretaceous volcanic activity in Palmer Land. Their dominance in the upper part of the core most likely relates to increased erosion of Palmer Land ash/tuffs from volcanic outcrops on the floor of Moutonnée Valley and implies a downturn in climate after c. 7500 yr BP and the reformation of George VI Ice Shelf.

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Section: Clast Geochemistry Isotopic Composition and Provenancesupporting

confidence: 83%

Section: Volcanic Clastssupporting

confidence: 62%

Section: Volcanic Clastsmentioning

confidence: 99%

Section: Primary Clastsmentioning

confidence: 99%

Section: Primary Clastsmentioning

confidence: 99%

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The Holocene history of George VI Ice Shelf, Antarctic Peninsula from clast-provenance analysis of epishelf lake sediments

Hodgson

Bentley

et al. 2008

Palaeogeography, Palaeoclimatology, Palaeoecology

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Origins of Antarctic Soils

Storey

2014

Antarctic Terrestrial Microbiology

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The source of granitic gneisses and migmatites in the Antarctic Peninsula: a combined U–Pb SHRIMP and laser ablation Hf isotope study of complex zircons

Flowerdew

Millar

Vaughan

et al. 2006

Contrib Mineral Petrol

Self Cite

162

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Zircons gneisses and migmatites collected from the Antarctic Peninsula have different core-rim hafnium isotope ratio relationships depending on whether evidence for zircon dissolution is present or absent. Two samples contain inherited zircon that is partially dissolved. In these samples, the 176 Hf/ 177 Hf rations of the inherited zircon and new magmatic zircon rims are, on average, indistinguishable and consistent with in situ melting. In such cases the hafnium isotopic composition of the melt was probably strongly influenced by the dissolved zircon component at the source. Variation in 176 Hf/ 177 Hf within the magmatic zircon rims from grain to grain suggests that Hf isotopes were only partially homogenized during melt migration; alternatively, zircon growth may have taken place within small volumes of partial melt. Other samples do not preserve textural evidence for zircon dissolution during melt generation; in these samples the 176 Hf/ 177 Hf values of the inherited zircon and new magmatic zircon rims are different. The zircon rims apparently suggest a source of less evolved hafnium than that contained within the inherited zircon. Whether this relates to a separate juvenile source or, alternatively, is derived from minerals other than zircon at the source, cannot be resolved. Inherited zircon, irrespective of age, has been strongly influenced by the reworking of a juvenile Late Mesoproterozoic source, suggesting that such crust underlies the Antarctic Peninsula. Our results therefore suggest that Hf isotope analyses provide great potential for future studies investigating the source and processes involved in the generation of crustal melts.

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The role of crustal and mantle sources in the genesis of granitoids of the Antarctic Peninsula and adjacent crustal blocks

Abstract: Magmatic rocks from the Antarctic Peninsula show marked variations in isotope composition, which reflect changes in the geodynamic evolution of the peninsula through time.

Cited by 51 publications

References 49 publications

The Holocene history of George VI Ice Shelf, Antarctic Peninsula from clast-provenance analysis of epishelf lake sediments

The Holocene history of George VI Ice Shelf, Antarctic Peninsula from clast-provenance analysis of epishelf lake sediments

Origins of Antarctic Soils

The source of granitic gneisses and migmatites in the Antarctic Peninsula: a combined U–Pb SHRIMP and laser ablation Hf isotope study of complex zircons

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