Acceder

Bibliografías temáticas / Amphibolis antarctica / Artículos de revistas

Siga este enlace para ver otros tipos de publicaciones sobre el tema: Amphibolis antarctica.

Artículos de revistas sobre el tema "Amphibolis antarctica"

Autor: Grafiati

Publicado: 23 de enero de 2024

Última modificación: 19 de diciembre de 2024

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros

Elija tipo de fuente:

Consulte los 50 mejores artículos de revistas para su investigación sobre el tema "Amphibolis antarctica".

Junto a cada fuente en la lista de referencias hay un botón "Agregar a la bibliografía". Pulsa este botón, y generaremos automáticamente la referencia bibliográfica para la obra elegida en el estilo de cita que necesites: APA, MLA, Harvard, Vancouver, Chicago, etc.

También puede descargar el texto completo de la publicación académica en formato pdf y leer en línea su resumen siempre que esté disponible en los metadatos.

Explore artículos de revistas sobre una amplia variedad de disciplinas y organice su bibliografía correctamente.

1

Verduin, Jennifer J., Anke Seidlitz, Mike van Keulen y Erik I. Paling. "Maximising establishment success of Amphibolis antarctica seedlings". Journal of Experimental Marine Biology and Ecology 449 (noviembre de 2013): 57–60. http://dx.doi.org/10.1016/j.jembe.2013.08.016.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

2

Waycott, Michelle, Diana I. Walker y Sidney H. James. "Genetic uniformity in Amphibolis antarctica, a dioecious seagrass". Heredity 76, n.º 6 (junio de 1996): 578–85. http://dx.doi.org/10.1038/hdy.1996.83.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

3

Rifai, Husen, Firman Zulpikar, Muhammad Safaat, Jeverson Renyaan, Laode Alifatri y Asep Rasyidin. "Responses of Seagrass Amphibolis antarctica Roots to Nutrient Additions Along a Salinity Gradient in Shark Bay, Western Australia". Omni-Akuatika 17, n.º 2 (1 de diciembre de 2021): 90. http://dx.doi.org/10.20884/1.oa.2021.17.2.913.

Texto completo

Resumen

Seagrass meadows in oligotrophic environments are particularly susceptible to nutrient enrichment, yet morphological and architectural seagrass root responses in these ecosystems are poorly understood. This study aimed to investigate the response of Amphibolis antarctica, one of dominant seagrass species in Shark Bay, roots to nutrient additions along a salinity gradient in the oligotrophic ecosystem of Shark Bay, Western Australia. A fully factorial nutrient additional experiment with four treatments (Control, N, P and N+P) was conducted at each of five sites along a salinity gradient (between ~38ppt in site 1 and ~50ppt in site 5) in Shark Bay across a three-year period (2012-2015). In the laboratory, the roots morphology and architecture A. antarctica were investigated using a software (WinRhizo). Then, a two-way analysis of variance (ANOVA) was performed to investigate if there was a significant change in the morphology and architecture of the roots after the nutrient inputs and along five sites with salinity gradient. There was no significant impact of nutrient addition on the root’s morphology and architecture of A. antarctica species. However, the effect of site factor with salinity gradient was significant to all morphological aspects (total root length, root surface area and root diameter) of A. antarctica roots. These findings highlight the more ecological function of A. antarctica roots being in anchoring of the plant into the seafloor rather than to absorb nutrient from the sediment.Keywords: Nutrient addition, Oligotrophic habitats, Amphibolis antarctica, Shark Bay

Los estilos APA, Harvard, Vancouver, ISO, etc.

4

Pedersen, Morten F., Eric I. Paling y Diana I. Walker. "Nitrogen uptake and allocation in the seagrass Amphibolis antarctica". Aquatic Botany 56, n.º 2 (marzo de 1997): 105–17. http://dx.doi.org/10.1016/s0304-3770(96)01100-x.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

5

van Keulen, Mike. "Multiple climate impacts on seagrass dynamics: Amphibolis antarctica patches at Ningaloo Reef, Western Australia". Pacific Conservation Biology 25, n.º 2 (2019): 211. http://dx.doi.org/10.1071/pc18050.

Texto completo

Resumen

The impacts of tropical cyclones combined with a marine heatwave are reported for a seagrass community at Ningaloo Reef, Western Australia. A community of 9.5ha of Amphibolis antarctica was lost following a combination of cyclone-induced burial and a marine heatwave. No new seedlings have been observed since the loss; recruitment of seedlings may be impeded by local ocean circulation.

Los estilos APA, Harvard, Vancouver, ISO, etc.

6

Verduin, JJ, DI Walker y J. Kuo. "In situ submarine pollination in the seagrass Amphibolis antarctica: research notes". Marine Ecology Progress Series 133 (1996): 307–9. http://dx.doi.org/10.3354/meps133307.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

7

Tanner, Jason E. "Restoration of the Seagrass Amphibolis antarctica—Temporal Variability and Long-Term Success". Estuaries and Coasts 38, n.º 2 (23 de mayo de 2014): 668–78. http://dx.doi.org/10.1007/s12237-014-9823-4.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

8

van Dijk, Kor-jent, Gina Digiantonio y Michelle Waycott. "New microsatellite markers for the seagrass Amphibolis antarctica reveal unprecedented genetic diversity". Aquatic Botany 148 (agosto de 2018): 25–28. http://dx.doi.org/10.1016/j.aquabot.2018.04.002.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

9

Bryars, Simon R. "Can regional nutrient status be used to predict plant biomass, canopy structure and epiphyte biomass in the temperate seagrass Amphibolis antarctica?" Marine and Freshwater Research 60, n.º 10 (2009): 1054. http://dx.doi.org/10.1071/mf08194.

Texto completo

Resumen

The seagrass Amphibolis antarctica is an important component of coastal soft-sediment ecosystems across southern Australia. Large-scale losses of A. antarctica at several locations have been linked to anthropogenic nutrient inputs. The present study comprised a field survey to test whether the spatial patterns of plant biomass, canopy structure and epiphyte biomass in A. antarctica could be predicted based on expectations related to nutrient status across two regions within Gulf St Vincent, South Australia. Specific predictions were that: (1) plant biomass, plant density, plant height, leaf cluster frequency and leaf frequency are all lower in the east (higher nutrient) region than in the west region; and (2) epiphyte biomass and epiphyte load are higher in the east than in the west. Regional nutrient status was a poor predictor of most of the parameters measured, with the opposite trends to those predicted often occurring. Plant biomass, canopy structure and epiphyte biomass appear to be a result of several site-specific factors that are not fully understood at this time. The results of the present study have significant implications for making generalised predictions and for monitoring A. antarctica on urbanised coasts, and will also be useful for informing ecological studies on plant–epiphyte and plant–animal interactions in A. antarctica ecosystems.

Los estilos APA, Harvard, Vancouver, ISO, etc.

10

Walker, D. I. y M. L. Cambridge. "An experimental assessment of the temperature responses of two sympatric seagrasses, Amphibolis antarctica and Amphibolis griffithii, in relation to their biogeography". Hydrobiologia 302, n.º 1 (marzo de 1995): 63–70. http://dx.doi.org/10.1007/bf00006399.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

11

Rivers, David O., Gary A. Kendrick y Diana I. Walker. "Microsites play an important role for seedling survival in the seagrass Amphibolis antarctica". Journal of Experimental Marine Biology and Ecology 401, n.º 1-2 (mayo de 2011): 29–35. http://dx.doi.org/10.1016/j.jembe.2011.03.005.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

12

Paling, E. I. y A. J. McComb. "Nitrogen and phosphorus uptake in seedlings of the seagrass Amphibolis antarctica in Western Australia". Hydrobiologia 294, n.º 1 (diciembre de 1994): 1–4. http://dx.doi.org/10.1007/bf00017618.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

13

Seddon, S. y AC Cheshire. "Photosynthetic response of Amphibolis antarctica and Posidonia australis to temperature and desiccation using chlorophyll fluorescence". Marine Ecology Progress Series 220 (2001): 119–30. http://dx.doi.org/10.3354/meps220119.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

14

Verduin, J. J. y J. O. Backhaus. "Dynamics of Plant–Flow Interactions for the Seagrass Amphibolis antarctica: Field Observations and Model Simulations". Estuarine, Coastal and Shelf Science 50, n.º 2 (febrero de 2000): 185–204. http://dx.doi.org/10.1006/ecss.1999.0567.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

15

Walker, D. I. y A. J. McComb. "Salinity response of the seagrass Amphibolis antarctica (Labill.) Sonder et Aschers.: an experimental validation of field results". Aquatic Botany 36, n.º 4 (abril de 1990): 359–66. http://dx.doi.org/10.1016/0304-3770(90)90052-m.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

16

Burnell, O. W., S. D. Connell, A. D. Irving, J. R. Watling y B. D. Russell. "Contemporary reliance on bicarbonate acquisition predicts increased growth of seagrass Amphibolis antarctica in a high-CO2 world". Conservation Physiology 2, n.º 1 (27 de noviembre de 2014): cou052. http://dx.doi.org/10.1093/conphys/cou052.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

17

Fraser, Matthew W., Gary A. Kendrick, Pauline F. Grierson, James W. Fourqurean, Mathew A. Vanderklift y Diana I. Walker. "Nutrient status of seagrasses cannot be inferred from system-scale distribution of phosphorus in Shark Bay, Western Australia". Marine and Freshwater Research 63, n.º 11 (2012): 1015. http://dx.doi.org/10.1071/mf12026.

Texto completo

Resumen

Differences in phosphorus (P) availability can influence the ecology and physiology of seagrass communities; and are usually inferred from changes in the relative P content in seagrass leaves. Shark Bay is a subtropical marine embayment, with decreasing P concentrations in the water column and sediments from north to south across the entire embayment. We examined the P and nitrogen (N) content of seagrass leaves and P content of sediments across the Faure Sill and Wooramel delta region of Shark Bay, to determine whether the leaf content of seagrasses in Shark Bay also decreased from north to south over smaller spatial scales. Nutrient content of Amphibolis antarctica and Halodule uninervis were highly variable and were not strongly correlated with sediment P concentrations. Mean N : P ratios of seagrasses (<33.5) were not indicative of P limitation, as has been previously assumed for Shark Bay. We conclude that availability of P for uptake by seagrasses across Shark Bay may be highly localised and cannot be predicted from system-scale gradients (>100 km) of sedimentary P distributions. We suggest that P availability to seagrasses is more likely a complex function of differing nutrient inputs, rates of delivery to the plants and cycling rates.

Los estilos APA, Harvard, Vancouver, ISO, etc.

18

Statton, John, Kingsley W. Dixon, Renae K. Hovey y Gary A. Kendrick. "A comparative assessment of approaches and outcomes for seagrass revegetation in Shark Bay and Florida Bay". Marine and Freshwater Research 63, n.º 11 (2012): 984. http://dx.doi.org/10.1071/mf12032.

Texto completo

Resumen

Here, we review the literature to evaluate seagrass revegetation projects focussed on Posidonia australis and Amphibolis antarctica, the main affected species in Shark Bay in the World Heritage Area in Western Australia, together with projects from Florida Bay, an analogous system with a long history of seagrass revegetation. We assessed the effectiveness of anchoring planting units, plant-unit density and size on planting-unit survival. We found no positive trends in our assessment, suggesting that there is no discrete technique, approach or technology that could be used with confidence to deliver cost-effective, scalable revegetation. Of concern was that revegetation success was evaluated over comparatively short time frames (1–3 years), driven by the strict time frames or deadlines of governing grant funding and commercial activities, leading to concerns that long-term revegetation outcomes may be difficult to assess with confidence. Several factors influenced revegetation outcomes which were grouped into three ‘filter’ categories; abiotic, biotic and socioeconomic. We recommend that future revegetation programs involving seagrass have greater emphasis on understanding how these filters act independently or collectively to drive successful revegetation as well as developing cost-effective, proven and scalable technology supported by longer-term monitoring to ensure revegetation programs do achieve the desired ecological outcomes.

Los estilos APA, Harvard, Vancouver, ISO, etc.

19

Kendrick, Gary A., Diana I. Walker y Arthur J. McComb. "Changes in distribution of macro-algal epiphytes on stems of the seagrass Amphibolis antarctica along a salinity gradient in Shark Bay, Western Australia". Phycologia 27, n.º 2 (junio de 1988): 201–8. http://dx.doi.org/10.2216/i0031-8884-27-2-201.1.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

20

Walker, D. I. y A. J. McComb. "Seasonal variation in the production, biomass and nutrient status of Amphibolis antarctica (Labill.) Sonder ex Aschers. and Posidonia australis hook.f. in Shark Bay, Western Australia". Aquatic Botany 31, n.º 3-4 (agosto de 1988): 259–75. http://dx.doi.org/10.1016/0304-3770(88)90016-2.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

21

Shiraishi, Kazuyuki, Takanobu Oba, Morihisa Suzuki y Ken’ichi Ishikawa. "Subsilicic magnesian potassium-hastingsite from the Prince Olav Coast, East Antarctica". Mineralogical Magazine 58, n.º 393 (diciembre de 1994): 621–27. http://dx.doi.org/10.1180/minmag.1994.058.393.11.

Texto completo

Resumen

AbstractTwo subsilicic magnesian potassium-hastingsites (4.55 and 4.34 wt.% K2O) and one magnesian potassium-hastingsite occur in calc-silicate pods in well-layered gneisses from the transitional amphibolite- and granulite-facies terrain of a Cambrian metamorphic complex, East Antarctica. Subsilicic magnesian potassium-hastingsite is the most K-rich Ca-amphibole yet reported:

Los estilos APA, Harvard, Vancouver, ISO, etc.

22

Walker, D. I. "Correlations between salinity and growth of the seagrass Amphibolis antarctica (labill.) Sonder & Aschers., In Shark Bay, Western Australia, using a new method for measuring production rate". Aquatic Botany 23, n.º 1 (octubre de 1985): 13–26. http://dx.doi.org/10.1016/0304-3770(85)90017-8.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

23

Iurmanov, Anton A. "Phylogenetic phytogeography of selected groups of seagrasses (Monocotylendoneae - Alismatales) based on analysing of genes 5.8S rRNA and RuBisCo large subunit". GEOGRAPHY, ENVIRONMENT, SUSTAINABILITY 15, n.º 1 (28 de marzo de 2022): 61–69. http://dx.doi.org/10.24057/2071-9388-2021-111.

Texto completo

Resumen

Seagrasses are representatives of the families Cymodoceaceae, Posidoniaceae, Zosteraceae, Hydrocharitaceae (Monocotylendoneae - Alismatales), adapted to growing in seawaters and all their important life circle events are taking place under the water including pollination and distribution of diasporas. Seagrasses are widespread in the littoral areas of the World Ocean, except for Antarctica, and play an important ecosystem role. Due to the insufficiently studied history of dispersal and formation of modern seagrasses habitats, we carried out a phylogenetic analysis of representatives of the families Cymodoceaceae (Amphibolis, Halodule, Syringodium, Cymodocea, and Thalassodendron), Posidoniaceae (Posidonia), Zosteraceae (Zostera, and Phyllospadix), and Hydrocharitaceae (Enhalus, Halophila, and Thalassia). The cladograms constructed based on molecular data analysis of the 5.8S ribosomal RNA and ribulose–1,5–bisphosphate carboxylase/oxygenase large subunit genes are used as the basis for reconstructing the history of dispersal of the studied taxa. It is found that the main stages of dispersal of selected groups of seagrasses took place in the Late Cretaceous period. The main track of historical distribution is largely predetermined by the modern ranges of almost all genera of seagrasses, stretches from the southwestern waters of eastern Gondwana to the northwestern waters of the Eurasian part of Laurasia. The main route of movement of diasporas and seagrasses populations was the Tethys water area, which was modified in the Late Mesozoic and early Cenozoic. It was revealed that the main method of dispersal of seagrasses was long-distance dispersal, which is confirmed by both molecular genetic data and very fast (on a geological time scale) processes of penetration into new water areas, and analysis of the features of dissemination of modern representatives. An alternative vicar scenario was proposed only for the reconstruction of the formation of the Posidonia range.

Los estilos APA, Harvard, Vancouver, ISO, etc.

24

Suwa, Kanenori, Masaki Enami y Tatsuro Horiuchi. "Chlorine-rich potassium hastingsite from West Ongul Island, Lützow–Holm Bay, East Antarctica". Mineralogical Magazine 51, n.º 363 (diciembre de 1987): 709–14. http://dx.doi.org/10.1180/minmag.1987.051.363.11.

Texto completo

Resumen

AbstractChlorine-rich potassium hastingsite occurs in a calcareous pegmatite, a replacement zone and an amphibolite lens within hornblende gneiss on West Ongul Island, Lützow-Holm Bay, East Antarctica. The amphibolite lens and hornblende gneiss were metamorphosed to the kyanite-sillimanite grade of the granulite facies during Proterozoic metamorphism. Chemical analysis (3.27 wt.% Cl), unit cell parameters and optical properties of the Cl-rich potassium hastingsite are given. Cl-rich (> 3 wt.%) calcic amphiboles reported from various rock types are mostly more than 0.9 in (Na+ K) content, more than 0.4 in K/(Na + K) ratio, more than 0.75 in Fe2+/(Fe2++ Mg + Mn) ratio and more than 1.9 in AlIVcontent (total iron as FeO and O = 23). The unit cell volume of Cl-rich hastingsite is distinctly larger than that of Cl-poor hastingsite.

Los estilos APA, Harvard, Vancouver, ISO, etc.

25

Matsubara, S. y Y. Motoyosh. "Potassium pargasite from Einstödingen, Lützow-Holm Bay, East Antarctica". Mineralogical Magazine 49, n.º 354 (diciembre de 1985): 703–7. http://dx.doi.org/10.1180/minmag.1985.049.354.09.

Texto completo

Resumen

AbstractPotassium pargasite containing 3.19 wt. % K2O was found in a skarn from the islet of Einstödingen, Lützow-Holm Bay, East Antarctica, together with some high potassium pargasitic amphiboles. A positive correlation is shown between Fe2+/(Mg+Fe2+) and K/(K + Na(A)) ratios in pargasitic amphiboles suggesting that the increase of Fe2+ serve to stabilize high-K pargasites under the metamorphic conditions of the granulite facies.

Los estilos APA, Harvard, Vancouver, ISO, etc.

26

Tedesco, M., C. M. Foreman, J. Anton, N. Steiner y T. Schwartzman. "Comparative analysis of morphological, mineralogical and spectral properties of cryoconite in Jakobshavn Isbræ, Greenland, and Canada Glacier, Antarctica". Annals of Glaciology 54, n.º 63 (2013): 147–57. http://dx.doi.org/10.3189/2013aog63a417.

Texto completo

Resumen

AbstractWe report the results of a comparative analysis focusing on grain size, mineralogical composition and spectral reflectance values (400-2500 nm) of cryoconite samples collected from Jakobshavn Isbræ, West Greenland, and Canada Glacier, McMurdo Dry Valleys, Antarctica. The samples from the Greenland site were composed of small particles clumped into larger rounded agglomerates, while those from the site in Antarctica contained fragments of different sizes and shapes. Mineralogical analysis indicates that the samples from Jakobshavn Isbræ contained a higher percentage of quartz and albite, whereas those from Canada Glacier contained a higher percentage of amphibole, augite and biotite. Spectral measurements confirmed the primary role of organic material in reducing the reflectance over the measured spectrum. The reflectance of the samples from the Antarctic site remained low after the removal of organic matter because of the higher concentration of minerals with low reflectance. The reflectance of dried cryoconite samples in the visible region was relatively low (e.g. between ∼0.1 and ∼0.4) favouring increased absorbed solar radiation. Despite high reflectance values in the shortwave infrared region, the effect of the presence of cryoconite is negligible at infrared wavelengths where ice reflectance is low.

Los estilos APA, Harvard, Vancouver, ISO, etc.

27

Mikhalsky, E. V., A. A. Laiba, B. V. Beliatsky y K. Stüwe. "Geology, age and origin of the Mount Willing area (Prince Charles Mountains, East Antarctica)". Antarctic Science 11, n.º 3 (septiembre de 1999): 338–52. http://dx.doi.org/10.1017/s0954102099000437.

Texto completo

Resumen

Mount Willing in the Prince Charles Mountains (East Antarctica) is part of the Fisher Volcano–plutonic complex which formed as part of the global-scale Grenvillian mobile belt system. Mount Willing is composed of four rock complexes: 1) a metamorphic sequence, 2) gabbro intrusions, 3) deformed felsic intrusives, and 4) abundant post-metamorphic dykes and veins. Three rock types constitute the metamorphic sequence: amphibole–biotite felsic plagiogneiss, mafic to intermediate biotite–amphibole schist, and biotite paragneiss. The bulk composition of the mafic schists classifies them as tholeiitic basalts, and rarely as basaltic andesites or andesites. Index mg ranges widely from 47 to 71. Concentrations of TiO2, P2O5, and high-field strength elements are high in some rocks. These rocks are thought to have been derived from enriched (subcontinental) mantle sources. Sm–Nd and U–Pb isotopic data indicate a series of Mesoproterozoic thermal events between 1100 and 1300 Ma. In particular, these events occurred at 1289 ± 10 Ma (volcanic activity), at 1177 ± 16 Ma (tonalite intrusion), at 1112.7 ± 2.4 and at 1009 ± 54 Ma (amphibolite facies metamorphic events). Rb–Sr systematics also indicates a thermal overprint at 636 ± 13 Ma. Mafic schists show low initial 877Sr/86Sr ratios between 0.7024 and 0.7030. Felsic rocks show higher Sri values between 0.7037 and 0.7061. Basaltic andesite metavolcanic and plutonic rocks form a calc-alkaline evolutionary trend, and probably originated from subduction-modified mantle sources in a convergent plate margin environment. An oceanic basin may have existed in central Prince Charles Mountains about 1300 Ma ago and was closed as a result of continental collision around 1000 to 800 Ma.

Los estilos APA, Harvard, Vancouver, ISO, etc.

28

Ricci, C. A., F. Talarico, R. Palmeri, G. Di Vincenzo y P. C. Pertusati. "Eclogite at the Antarctic palaeo-Pacific active margin of Gondwana (Lanterman Range, northern Victoria Land, Antarctica)". Antarctic Science 8, n.º 3 (septiembre de 1996): 277–80. http://dx.doi.org/10.1017/s0954102096000399.

Texto completo

Resumen

Well-preserved eclogites were found for the first time in Antarctica, at the Lanterman Range, northern Victoria Land. They are part of a mafic–ultramafic belt that lies between the Wilson Terrane, representing part of the palaeo-Pacific margin of Gondwana, and the Bowers Terrane, a Cambro-Ordovician volcanic are and related sediments, accreted to the margin during the Ross Orogeny. The eclogites formed at temperatures in the range 750–850°C and pressures above 15 kbar and subsequently experienced a decompressional path to low pressure amphibolite facies conditions. The formation and exhumation of eclogites and the attainment of the metamorphic peak in adjacent rock units is consistent with a plate convergent setting model at the palaeo-Pacific margin of Gondwana.

Los estilos APA, Harvard, Vancouver, ISO, etc.

29

Delor, C. P. y N. M. S. Rock. "Alkaline-ultramafic lamprophyre dykes from the Vestfold Hills, Princess Elizabeth Land (East Antarctica): primitive magmas of deep mantle origin". Antarctic Science 3, n.º 4 (diciembre de 1991): 419–32. http://dx.doi.org/10.1017/s0954102091000512.

Texto completo

Resumen

Alkaline dykes tentatively dated at ∼1.3 Ga cut the Vestfold Hills in a consistent N–S to N15°E direction. They form a spectrum between more abundant ultramafic lamprophyres (UML) corresponding broadly to H2O–CO2-rich nephelinites, and alkaline lamprophyres (AL), representing H2O–CO2-rich basanites. Olivine (Fo46–93, averaging Fo75) is abundant only in the UML, but both types carry primary diopsidic clinopyroxene with complex zoning; amphibole (pargasite, hastingsite, kaersutite with up to 8.6% TiO2); titanian phlogopite (up to 10% TiO2); feldspars (orthoclase, anorthoclase, albite and andesine), nepheline (K-poor and Si-rich), ilmenite (up to 1% MgO and MnO), chrome titanomagnetite, and carbonate (magnesian calcite, ferroan dolomite, breunnerite). Lamprophyric peculiarities include the local coexistence of three feldspars, extremely Ti-rich amphiboles and micas, and the presence of globular structures and possibly primary carbonates. Some dykes carry small but abundant lherzolite xenoliths, others carry chromian diopside (1% Cr2O3) and En58–76 orthopyroxene xenocrysts. The dykes represent primitive, mantle-derived magmas which have undergone varying but generally low degrees of polybaric fractionation, together perhaps with mixing of more primitive and fractionated batches, during their ascent through the crust.

Los estilos APA, Harvard, Vancouver, ISO, etc.

30

Hervé, Francisco, Jorge Lobato, Ignacio Ugalde y Robert J. Pankhurst. "The geology of Cape Dubouzet, northern Antarctic Peninsula: continental basement to the Trinity Peninsula Group?" Antarctic Science 8, n.º 4 (diciembre de 1996): 407–14. http://dx.doi.org/10.1017/s0954102096000582.

Texto completo

Resumen

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.

Los estilos APA, Harvard, Vancouver, ISO, etc.

31

Passchier, C. W., R. F. Bekendam, J. D. Hoek, P. G. H. M. Dirks y H. de Boorder. "Proterozoic geological evolution of the northern Vestfold Hills, Antarctica". Geological Magazine 128, n.º 4 (julio de 1991): 307–18. http://dx.doi.org/10.1017/s0016756800017581.

Texto completo

Resumen

AbstractThe presence of polyphase shear zones transected by several suites of dolerite dykes in Archaean basement of the Vestfold Hills, East Antarctica, allows a detailed reconstruction of the local structural evolution. Archaean and early Proterozoic deformation at granulite facies conditions was followed by two phases of dolerite intrusion and mylonite generation in strike-slip zones at amphibolite facies conditions. A subsequent middle Proterozoic phase of brittle normal faulting led to the development of pseudotachylite, predating intrusion of the major swarm of dolerite dykes around 1250 Ma. During the later stages and following this event, pseudotachylite veins were reactivated as ductile, mylonitic thrusts under prograde conditions, culminating in amphibolite facies metamorphism around 1000–1100 Ma. This is possibly part of a large-scale tectonic event during which the Vestfold block was overthrust from the south. In a final phase of strike-slip deformation, several pulses of pseudotachylite-generating brittle faulting alternated with ductile reactivation of pseudotachylite.

Los estilos APA, Harvard, Vancouver, ISO, etc.

32

Ravikant, V. y Amitava Kundu. "Reaction Textures of Retrograde Pressure-Temperature-Deformation Paths from Granulites of Schirmacher Hills, East Antarctica". Journal Geological Society of India 51, n.º 3 (1 de marzo de 1998): 305–14. http://dx.doi.org/10.17491/jgsi/1998/510304.

Texto completo

Resumen

Abstract A retrograde path inferred for the Schirmacher Hills granulites involves near ITD path following post-peak granulite facies metamorphism (M1/D1), preserved only in enclaves, followed by near IBC path, M3, post dating M2/D2 granulites facies metamorphism and deformation. Final uplift and cooling of the terrain occurred in the upper amphibolite facies metamorphic conditions, M4, syntectonic with respect to D3 deformation and emplacement of large volume of syntectonic granitoids. Fluids released during cooling and crystallization of these granitoids probably caused the large scale retrogression of granulite facies rocks to amphibolite facies gneisses.

Los estilos APA, Harvard, Vancouver, ISO, etc.

33

Velev, Stefan, Anna Lazarova, Fatih Karaoglan, Oleg Vassilev y Mahmut Oğuz Selbesoğlu. "Early Jurassic and Late Cretaceous magmatism on Horseshoe Island, Antarctic Peninsula: New U-Pb and microstructural data". Geologica Balcanica 52, n.º 3 (24 de agosto de 2023): 29–32. http://dx.doi.org/10.52321/geolbalc.52.3.29.

Texto completo

Resumen

Early Jurassic U-Pb age is obtained for both foliated and undeformed granites on Horseshoe Island, Antarctic Peninsula. Some microstructures in the foliated granites/orthogneisses indicate high-temperature greenschist or low- to medium-temperature amphibolite facies deformation conditions. Additionally, a Late Cretaceous age is yielded for a gabbro intruding the deformed granitoids.

Los estilos APA, Harvard, Vancouver, ISO, etc.

34

Borsi, L., R. Petrini, F. Talarico y R. Palmeri. "Geochemistry and Sr-Nd isotopes of amphibolite dykes of northern Victoria Land, Antarctica". Lithos 35, n.º 3-4 (junio de 1995): 245–59. http://dx.doi.org/10.1016/0024-4937(95)99070-d.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

35

Sengupta, Sudipta. "History of Successive Deformations in Relation to Metamorphism-Migmatitic Events in the Schirmacher Hills, Queen Maud Land, East Antarctica". Journal Geological Society of India 32, n.º 4 (1 de octubre de 1988): 295–319. http://dx.doi.org/10.17491/jgsi/1988/320403.

Texto completo

Resumen

Abstract The basement complex in the Schirmacher Hills of East Antarctica records the impress of multiple episodes of metamorphism, migmatization and deformation. In the earliest event there was a regional metamorphism under granulite facies conditions and synkinematic migmatization leading to the development of charnockitic rocks. An amphibolite facies metamorphism was superimposed on them. This late event was closely associated with widespread granitization leading to the development of the majority of the quartzofeldspathic gneisses. In the earliest deformation, a migmatitic banding and a crude foliation formed in the charnockitic rocks. This was followed by a period of strong deformation during which two broadly coaxial sets of isoclinal folds (F2A and F2B) formed. The folding movement was also associated with widespread ductile shearing. The periods of amphibolite facies metamorphism, extensive granitization, F2 folding and the major phase of ductile shearing were overlapping. Localized pegmatite bodies were also emplaced during the later and much weaker folding movements of F3 and F4 and along some discordant ductile shear zones cutting across the axial surfaces of F2 folds.

Los estilos APA, Harvard, Vancouver, ISO, etc.

36

WENDT, ANKE S., ALAN P. M. VAUGHAN y ALEXANDER TATE. "Metamorphic rocks in the Antarctic Peninsula region". Geological Magazine 145, n.º 5 (23 de junio de 2008): 655–76. http://dx.doi.org/10.1017/s0016756808005050.

Texto completo

Resumen

AbstractThe distribution of metamorphic rocks in the Antarctic Peninsula region, new quantitative peak pressure–temperature data along the Antarctic Peninsula, and a literature review on the current knowledge of metamorphic conditions in the Antarctic Peninsula region have been compiled into a single metamorphic map. The pressure–temperature data for the Antarctic Peninsula indicate (1) burial of supracrustal rocks to low to mid-crustal depth along the eastern and western side of the Antarctic Peninsula and on some islands adjacent to the western side of the peninsula; (2) uplift of lower- to mid-crustal metamorphic rocks along major shear and fault zones; and (3) a reversed succession of metamorphic grades for the western domain of the Antarctic Peninsula region compared to the eastern domain along the Eastern Palmer Land Shear Zone (EPLSZ) of the Antarctic Peninsula. The metamorphic data are consistent with oblique convergence between Alexander Island (the Western Domain), Palmer Land (Central Domain) and the Gondwana margin (the Eastern Domain), supporting a model of (1) exhumation and shearing of the higher pressure rocks from central western (up to 9.4 kbar) and from northeast (7 kbar to 9 kbar) Palmer Land, (2) the exhumation and shearing of low to medium pressure rocks in western Palmer Land and along the Eastern Palmer Land Shear Zone, and (3) shallow burial and subsequent exhumation of sediments of the Gondwana margin along the Eastern Palmer Land Shear Zone. Based on the high-amphibolite grade rocks exposed in central western Palmer Land, our data also support earlier suggestions that the Eastern Palmer Land Shear Zone is the surface expression of a northwest- to west-dipping, deep-level, high-temperature crustal shear zone extending below the western part of the Central Domain of the Antarctic Peninsula.

Los estilos APA, Harvard, Vancouver, ISO, etc.

37

Coltorti, Massimo, Luigi Beccaluva, Costanza Bonadiman, Barbara Faccini, Theodoros Ntaflos y Franca Siena. "Amphibole genesis via metasomatic reaction with clinopyroxene in mantle xenoliths from Victoria Land, Antarctica". Lithos 75, n.º 1-2 (julio de 2004): 115–39. http://dx.doi.org/10.1016/j.lithos.2003.12.021.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

38

Grapes, R. H., R. J. Wysoczanski y P. W. O. Hoskin. "Rhönite paragenesis in pyroxenite xenoliths, Mount Sidley volcano, Marie Byrd Land, West Antarctica". Mineralogical Magazine 67, n.º 4 (agosto de 2003): 639–51. http://dx.doi.org/10.1180/0026461036740123.

Texto completo

Resumen

AbstractRhönite occurs in lower crustal pyroxenite xenoliths erupted in phonolite from the Mount Sidley composite volcano, Marie Byrd Land, Antarctica, as a localized breakdown product, with plagioclase, clinopyroxene, ± olivine ± Ti-magnetite + melt, of kaersutite, and as microphenocrysts (with olivine, plagioclase, clinopyroxene) in pockets of basanitic melt. Rhö nite after kaersutite has a more NaSi-rich/ CaAl-poor composition, lower Ti, and formed at higher oxidation (∼NNO) conditions than rhönite occurring as microphenocrysts in basanite. Comparison with experimentally determined rhönite stability in understaturated alkali basalt and as a reaction product after Ti-amphibole indicates that the Mount Sidley rhönite (and associated minerals) formed between 1090 and 1190°C at <0.5 kbar, presumably during temporary residence of the xenoliths in a shallow magma chamber below the volcanic edifice.

Los estilos APA, Harvard, Vancouver, ISO, etc.

39

Elvevold, Synnøve, Joachim Jacobs, Leif-Erik Rydland Pedersen, Øyvind Sunde, Ane K. Engvik y Per Inge Myhre. "Symplectite and kelyphite formation during decompression of mafic granulite from Gjelsvikfjella, central Dronning Maud Land, Antarctica". European Journal of Mineralogy 35, n.º 6 (14 de noviembre de 2023): 969–85. http://dx.doi.org/10.5194/ejm-35-969-2023.

Texto completo

Resumen

Abstract. Central Dronning Maud Land (cDML) is part of the late Mesoproterozoic Maud Belt in East Antarctica, which was metamorphosed and deformed during the Ediacaran–Cambrian Gondwana assembly. Here we study high-pressure (HP) mafic rocks in Gjelsvikfjella, cDML, which occur as lenses and pods transposed in highly strained, upper amphibolite-facies gneisses. We present a P–T–t history for the HP rocks based on mineral assemblages, reaction textures and new U–Pb zircon data. Relics that indicate an early HP granulite-facies stage have been identified in anhydrous garnet–clinopyroxene rocks. The peak-pressure assemblage was plagioclase-free and contained garnet, titanite, clinopyroxene and quartz. The HP assemblage has been extensively overprinted by lower-pressure phases and exhibits a variety of symplectite and corona textures that record the post-peak-pressure evolution of the rocks. Decompression and heating in the granulite-facies field resulted in the replacement of titanite by ilmenite–clinopyroxene symplectite, formation of clinopyroxene–plagioclase intergrowths and resorption of garnet by plagioclase–clinopyroxene kelyphite. Formation of late orthopyroxene in symplectites and kelyphites demonstrates that the P–T evolution entered the medium-pressure granulite-facies field. The peak metamorphic stage was followed by retrograde cooling into the amphibolite facies. In situ laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) U–Pb dating of zircons indicate Mesoproterozoic protolith ages (1150–1000 Ma) and Ediacaran–Cambrian metamorphic reworking at ca. 568 and ca. 514 Ma. The HP granulites were formed and exhumed during a clockwise P–T evolution related to continental collision during Gondwana amalgamation, followed by post-collisional extension and orogenic collapse.

Los estilos APA, Harvard, Vancouver, ISO, etc.

40

Mikhalsky, E. V., J. W. Sheraton, A. A. Laiba y B. V. Beliatsky. "Geochemistry and origin of Mesoproterozoic metavolcanic rocks from Fisher Massif, Prince Charles Mountains, East Antarctica". Antarctic Science 8, n.º 1 (marzo de 1996): 85–104. http://dx.doi.org/10.1017/s0954102096000120.

Texto completo

Resumen

Fisher Massif consists of Mesoproterozoic (c. 1300 Ma) lower amphibolite-facies metavolcanic rocks and associated metasediments, intruded by a variety of subvolcanic and plutonic bodies (gabbro to granite). It differs in both composition and metamorphic grade from the rest of the northern Prince Charles Mountains, which were metamorphosed to granulite facies about 1000 m.y. ago. The metavolcanic rocks consist mainly of basalt, but basaltic andesite, andesite, and more felsic rocks (dacite, rhyodacite, and rhyolite) are also common. Most of the basaltic rocks have compositions similar to low-K island arc tholeiites, but some are relatively Nb-rich and more akin to P-MORB. Intermediate to felsic medium to high-K volcanic rocks, which appear to postdate the basaltic succession, have calc-alkaline affinities and probably include a significant crustal component. On the present data, an active continental margin with associated island arc was the most likely tectonic setting for generation of the Fisher Massif volcanic rocks.

Los estilos APA, Harvard, Vancouver, ISO, etc.

41

Palmeri, R., S. Sandroni, G. Godard y C. A. Ricci. "Boninite-derived amphibolites from the Lanterman-Mariner suture (northern Victoria Land, Antarctica): New geochemical and petrological data". Lithos 140-141 (mayo de 2012): 200–223. http://dx.doi.org/10.1016/j.lithos.2012.02.001.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

42

Zeh, Armin, Axel Gerdes, Thomas M. Will y Hartwig E. Frimmel. "Hafnium isotope homogenization during metamorphic zircon growth in amphibolite-facies rocks: Examples from the Shackleton Range (Antarctica)". Geochimica et Cosmochimica Acta 74, n.º 16 (agosto de 2010): 4740–58. http://dx.doi.org/10.1016/j.gca.2010.05.016.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

43

Cox, Simon C. "Inter-related plutonism and deformation in South Victoria Land, Antarctica". Geological Magazine 130, n.º 1 (enero de 1993): 1–14. http://dx.doi.org/10.1017/s0016756800023682.

Texto completo

Resumen

AbstractThe Lower Palaeozoic Bonney Pluton is a regionally extensive coarse-grained, variably megacrystic, monzodioritic to granitic body that crops out over 1000 km2 in South Victoria Land. It intruded upper amphibolite facies Koettlitz Group metasediments and interlayered orthogneisses. Magmatic fabrics are developed in the centre of the pluton by flow alignment of K-feldspars before the majority of phases had crystallized, whereas solid-state fabrics developed in the pluton margins by ductile–plastic deformation. Structures developed in the host-rocks vary around this elongate northwest–southeast-trending pluton. Upright, tight northwest–southeast-trending macroscopic folds are developed at the sides of the pluton, with axis-parallel stretching lineations and boudinage indicating strong northwest–southeast extension. Broad warps of tight macroscopic folds, and mesoscopic refolded folds, sheath folds and complicated interference patterns characterize areas at the ends of the pluton. Emplacement of the pluton involved radial expansion in a regional northeast–southwest compression, and growth predominantly in the northwest–southeast direction. Superposition of the radial expansion and regional compression resulted in an inhomogeneous strain field at a regional scale, with coaxial strain at the sides of the pluton and non-coaxial strain at the ends. Upright folds developed at the pluton's sides, and became tighter with continued coaxial deformation. Non-coaxial structures developed at the ends of the pluton and were pushed aside by the growing pluton into areas of coaxial deformation, resulting in complex folding, re-folding and sheath folds. Metamorphism of the host-rocks and migmatite development was more intense at the sides of the pluton than near the ends, possibly due to different P-T-t paths of host-rocks around syntectonic plutons.

Los estilos APA, Harvard, Vancouver, ISO, etc.

44

GAMBLE, J. A. y P. R. KYLE. "The Origins of Glass and Amphibole in Spined--Wehrlite Xenoliths from Foster Crater, McMurdo Volcanic Group, Antarctica". Journal of Petrology 28, n.º 5 (1 de octubre de 1987): 755–79. http://dx.doi.org/10.1093/petrology/28.5.755.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

45

Gentili, Silvia, Cristian Biagioni, Paola Comodi, Marco Pasero, Catherine McCammon y Costanza Bonadiman. "Ferri-kaersutite, NaCa2(Mg3TiFe3+)(Si6Al2)O22O2, a new oxo-amphibole from Harrow Peaks, Northern Victoria Land, Antarctica". American Mineralogist 101, n.º 2 (febrero de 2016): 461–68. http://dx.doi.org/10.2138/am-2016-5204.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

46

Carson, Christopher J., Jay J. Ague, Marty Grove, Christopher D. Coath y T. Mark Harrison. "U–Pb isotopic behaviour of zircon during upper-amphibolite facies fluid infiltration in the Napier Complex, east Antarctica". Earth and Planetary Science Letters 199, n.º 3-4 (junio de 2002): 287–310. http://dx.doi.org/10.1016/s0012-821x(02)00565-4.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

47

Orlando, Andrea, Sandro Conticelli, Pietro Armienti y Daniele Borrini. "Experimental study on a basanite from the McMurdo Volcanic Group, Antarctica: inference on its mantle source". Antarctic Science 12, n.º 1 (marzo de 2000): 105–16. http://dx.doi.org/10.1017/s0954102000000134.

Texto completo

Resumen

Experiments to reconstruct the liquidus curve and establish the phase relationships of a basanite (Mg# = 72) from the McMurdo Volcanic Group, (thought to represent a nearly primary magma) used 1.0– 3.0 GPa and 1175–1550°C. The results suggest that this basanite could be generated by partial melting either of a spinel Iherzolite (at P = 1.5–2.0 GPa and T = 1390–1490°C) or of a garnet pyroxenite (at P > 3.0 GPa and T > 1550°C) source. Several lines of petrological and geochemical evidence support the latter hypothesis. Moreover, experimental results indicate the presence of mica in the source if it is assumed that the magma lost some water during its ascent to the surface. This is supported by the presence of mica and amphibole-bearing mantle xenoliths hosted in the most primitive volcanic rocks of the McMurdo Volcanic Group. These results and observations suggest that the source of magmas underwent metasomatism prior to partial melting.

Los estilos APA, Harvard, Vancouver, ISO, etc.

48

Panter, K. S., T. I. Wilch, J. L. Smellie, P. R. Kyle y W. C. McIntosh. "Chapter 5.4b Marie Byrd Land and Ellsworth Land: petrology". Geological Society, London, Memoirs 55, n.º 1 (2021): 577–614. http://dx.doi.org/10.1144/m55-2019-50.

Texto completo

Resumen

AbstractIn Marie Byrd Land and Ellsworth Land 19 large polygenetic volcanoes and numerous smaller centres are exposed above the West Antarctic Ice Sheet along the northern flank of the West Antarctic Rift System. The Cenozoic (36.7 Ma to active) volcanism of the Marie Byrd Land Volcanic Group (MBLVG) encompasses the full spectrum of alkaline series compositions ranging from basalt to intermediate (e.g. mugearite, benmoreite) to phonolite, peralkaline trachyte, rhyolite and rare pantellerite. Differentiation from basalt is described by progressive fractional crystallization; however, to produce silica-oversaturated compositions two mechanisms are proposed: (1) polybaric fractionation with early-stage removal of amphibole at high pressures; and (2) assimilation–fractional crystallization to explain elevated87Sr/86Sriratios. Most basalts are silica-undersaturated and enriched in incompatible trace elements (e.g. La/YbN>10), indicating small degrees of partial melting of a garnet-bearing mantle. Mildly silica-undersaturated and rare silica-saturated basalts, including tholeiites, are less enriched (La/YbN<10), a result of higher degrees of melting. Trace elements and isotopes (Sr, Nd, Pb) reveal a regional gradient explained by mixing between two mantle components, subduction-modified lithosphere and HIMU-like plume (206Pb/204Pb >20) materials. Geophysical studies indicate a deep thermal anomaly beneath central Marie Byrd Land, suggesting a plume influence on volcanism and tectonism.

Los estilos APA, Harvard, Vancouver, ISO, etc.

49

Leat, P. T., T. R. Riley, B. C. Storey, S. P. Kelley y I. L. Millar. "Middle Jurassic ultramafic lamprophyre dyke within the Ferrar magmatic province, Pensacola Mountains, Antarctica". Mineralogical Magazine 64, n.º 1 (febrero de 2000): 95–111. http://dx.doi.org/10.1180/002646100549021.

Texto completo

Resumen

AbstractAn ultramafic lamprophyre dyke is described from the otherwise tholeiitic Ferrar magmatic province of Antarctica. We report an Ar-Ar age of 183 ± 2.2 Ma for the dyke, indistinguishable from those of the Ferrar tholeiites. However, the dyke has mineralogical and major and trace element compositions, and radiogenic isotopes ratios, very different from the Ferrar tholeiites. The sample consists of olivine and rare clinopyroxene phenocrysts with perovskite and spinel microphenocrysts in a groundmass of amphibole, nepheline and biotite. Carbonatitic globules contain calcite, dolomite, Fe-rich carbonate, nepheline, biotite, orthoclase, pyrite, clinopyroxene, apatite and silicate glass, and were formed by liquid immiscibility. The rock is mildly potassic and classifies as an ouachitite. It is strongly enriched in both moderately and highly incompatible trace elements and is the first high-Ti rock to be described from the Ferrar magmatic province. The rock has similar initial 143Nd/144Nd to OIB, notably Bouvet, Crozet and Réunion, but significantly higher initial 87Sr/86Sr. The lamprophyre magma is interpreted as having been generated by low-degree partial fusion of metasomatized lithospheric mantle as a result of heat conducted from an underlying Jurassic mantle plume. The same mantle plume was probably also responsible for generating one of the world’s largest layered gabbro bodies, the Dufek-Forrestal intrusions.

Los estilos APA, Harvard, Vancouver, ISO, etc.

50

Leat, Philip T., Bryan C. Storey y Robert J. Pankhurst. "Geochemistry of Palaeozoic–Mesozoic Pacific rim orogenic magmatism, Thurston Island area, West Antarctica". Antarctic Science 5, n.º 3 (septiembre de 1993): 281–96. http://dx.doi.org/10.1017/s0954102093000380.

Texto completo

Resumen

Thurston Island, and the adjacent Eights Coast and Jones Mountains, record Pacific margin magmatism from Carboniferous to Late Cretaceous times. The igneous rocks form a uniformly calc-alkaline, high-alumina, dominantly metaluminous suite; some relatively fractionated granitoids are mildly peraluminous. The magmas were hydrous, a result of subduction. Gabbros have compositions outside the range of mafic volcanic and hypabyssal rocks, as a result of cumulate processes. Trace element compositions of the mafic magmas range from a low La/Yb, Th/Ta end-member close to E-MORB in composition, perhaps contaminated by crust, to a high La/Yb, Th/Ta end-member, close to shoshonite, with strong magmatic arc trace element character. This variation may be a result of mixing of tholeiitic and shoshonitic end-members. Most silicic rocks could have been generated batch-wise from mafic magmas by fractional crystallization of a phenocryst assemblage dominated by plagioclase, pyroxene ± amphibole, as seen in the cumulates. Cessation of magmatism at about 90 Ma approximately coincided with collison of a spreading centre between the Phoenix and Pacific oceanic plates with the continent margin subduction zone. The rifting of New Zealand from West Antarctica and associated extension probably was responsible for emplacement of a coast-parallel Cretaceous dyke swarm.

Los estilos APA, Harvard, Vancouver, ISO, etc.

Ofrecemos descuentos en todos los planes premium para autores cuyas obras están incluidas en selecciones literarias temáticas. ¡Contáctenos para obtener un código promocional único!