Search

This paper reports the metamorphic texture of cordierite megacrysts and the metamorphic P–T path of a newly exposed section of gneiss in East Antarctica. We used mineral textures and pseudosection modeling to reconstruct the metamorphic P–T path of cordierite- and spinel–garnet-bearing gneisses from Botnnuten, an isolated nunatak located ~ 60 km from the southern edge of Lützow-Holm Bay in East Antarctica. The gneisses underwent low-P granulite-facies metamorphism at 5.0–6.1 kbar and 850 ± 20 °C followed by isobaric cooling. The isobaric cooling path implies long residence in the middle to shallow crustal level without rapid exhumation. This contrasts with the widely recognized clockwise P–T path of basement rocks of the Lützow-Holm Complex. The rocks at Botnnuten have long been considered part of the Lützow-Holm Complex based on their petrographical features and geothermobarometric data. However, the present results, combined with a reevaluation of available data, indicate the metamorphic history of the Botnnuten gneisses is more comparable to that of the Yamato Mountains, located southwest of the study area. [ABSTRACT FROM AUTHOR]

Constraining the role of microbes in the structural iron (Fe) reduction of iron-bearing minerals improves our understanding of sediments and ice sheets as a source of dissolved Fe (dFe) to the oceans. However, bio-mediated structural Fe-reduction has yet to be studied in cryospheric environments. Here, we show that the Fe reducing psychrophile bacterium Shewanella vesiculosa, isolated from sea ice in Antarctica, reduced structural Fe in nontronite (NAu-2) and maghemite (γ-Fe 2 O 3), common mineral phases in glacial ice, and marine sediments in Antarctica, during two freeze–thaw cycles (−10 °C to +15 °C), resulting in the release of dFe. The modification of turbostratically disordered nontronite (ferric iron dominant phase) to discrete ordered illite-like structure (ferrous iron dominant phase), and the aggregation of altered small maghemite particles with neoformation of vivianite (Fe 3 (PO 4) 2 ·nH 2 O) indicated the microbially induced reductive dissolution of nontronite and maghemite, respectively. The biotic Fe-reduction gradually decreased and ceased as the temperature approached freezing (−8 °C), however the rection reactivated in the thawing cycle (−7 to +15 °C). No discernable biotic Fe-reduction was measured for either mineral under freezing conditions, suggesting that temperature limits the activity of the microbes. Further, and regardless of temperatures during two freeze–thaw cycles, Fe-reduction was not observed in abiotic control. Overall, these results highlight the importance of microbially induced Fe reduction during seasonal freeze–thaw cycles of ice and sediments in continuous supplying bioavailable dFe to cryospheric environments and the often Fe-limited polar oceans. [ABSTRACT FROM AUTHOR]

Spinel- and orthopyroxene-bearing metapelitic granulites exposed in the Bunger Hills, East Antarctica, have been intensively studied in recent years because they are supposed to record evidence for UHT metamorphism. Detailed petrographic observations, as well as whole rock and mineral chemistry, together with SIMS trace element data on quartz, garnet, and orthopyroxene, are presented for these rocks. Mineral thermobarometry, including Al-in-orthopyroxene, ternary feldspar, Ti-in-quartz, and Fe-Ti oxide solvus, has been used to quantify the UHT conditions. Based on phase equilibrium modeling, a tight clockwise P-T path has been deduced, which involves near-isobaric heating at 6–7 kbar to ~950 °C followed by near-isobaric to slightly up-pressure cooling at 5–6 kbar to ~750 °C. It is concluded that the outlined metamorphic history is characteristic of an extensional crustal regime which is also evidenced by the correlation of prograde and retrograde metamorphism with the extensional and compressional phases of major ductile deformations recognized in the region. In order to constrain the tectonic setting of the granulites, this result is discussed in the context of current views on the Mesoproterozoic evolution of the Albany-Fraser Orogen, the westernmost part of which the Bunger Hills are considered to be. [ABSTRACT FROM AUTHOR]

The Rauer Group in East Antarctica is a typical high- to ultrahigh-temperature (HT–UHT) granulite-facies terrane. As UHT metamorphism has been recognized only in Mg–Al-rich pelitic granulites from the Mather Paragneiss, the regional extent of UHT metamorphism remains uncertain, which has hindered our understanding of the genesis and tectonic setting of UHT metamorphism in the Rauer Group. In this study, representative samples of mafic granulite were selected from Archean crustal domains to constrain the peak metamorphic conditions and P–T path and to assess the regional extent of UHT metamorphism in the Rauer Group. Integrated results from mineral reaction histories, thermobarometry, and phase equilibria modeling indicate a multi-stage clockwise P–T evolution for mafic granulites involving pre-peak compression, heating to UHT peak conditions, post-peak near-isothermal decompression under UHT conditions, and subsequent decompressional cooling. The pre-peak prograde history is based mainly on the inclusion assemblage of clinopyroxene + plagioclase + amphibole + quartz + ilmenite ± orthopyroxene ± k-feldspar within porphyroblastic garnet and clinopyroxene and records the transformation from a quartz-present to quartz-absent system. The UHT peak conditions are well constrained at 930°C–1030°C and 10.6–12.8 kbar on the basis of the stability field of the observed peak assemblage of (orthopyroxene–quartz)-free garnet + clinopyroxene + plagioclase + amphibole + ilmenite + melt, as well as measured mineral compositions, including the high Ti content in amphibole (Ti = 0.38–0.42 p.f.u.), the anorthite content of coarse-grained plagioclase cores (XAn = 0.35–0.42), and the grossular content in garnet (XGrs = ~0.21) in P–T pseudosections. The peak T conditions are consistent with thermometric estimates in the range of 930°C–1030°C obtained from garnet–clinopyroxene, garnet–orthopyroxene, and Ti-in-amphibole thermometers, and are slightly lower than estimates (1020°C–1120°C) obtained from thermometers based on rare earth elements. The near-isothermal decompression under UHT conditions can be divided into two stages. The early stage is recorded by coronae of orthopyroxene + plagioclase around clinopyroxene and core–mantle/rim anorthite-increasing zoning in plagioclase. The late stage is identified from symplectites of orthopyroxene + plagioclase ± amphibole around porphyroblastic garnet, which were formed at the expense of garnet at 915°C–950°C and 7.6–8.2 kbar as inferred from the amphibole–plagioclase thermometer. The subsequent decompressional cooling to fluid-absent solidus conditions (~875°C and ~6.5 kbar) is indicated by the growth of biotite, which formed at the expense of symplectic minerals, reflecting back-reaction of melt with symplectite minerals. The peak UHT metamorphic conditions and clockwise P–T path of the studied mafic granulites from the Archean crustal domains are similar to those of Mg–Al-rich pelitic UHT granulites from the Mather Paragneiss. The UHT conditions recorded by the mafic granulites, combined with previously identified isolated UHT localities in the Rauer Group, imply that UHT metamorphism in the Rauer Group occurred over a much wider region than previously thought and probably extends over the whole Archean crustal domain. Our findings have general significance in understanding the regional extent of other UHT granulite-facies terranes worldwide. [ABSTRACT FROM AUTHOR]

Calcium carbonate hexahydrate (ikaite) is a rare mineral that forms as metastable species in the organic-carbon-rich sediments of the King George Basin, Bransfield Strait, Antarctica, as a consequence of early diagenetic decomposition of organic matter under cold water (−1.4 °C) and high pressure (200 bar) conditions. Large crystals grow in the sediment immediately below the diagenetic transition between microbial sulfate reduction and methanogenesis at ~320 cm below sea floor (bsf). This process is reflected in the dissolved sulfate, total carbon dioxide, and methane concentrations, as well as in the carbon, hydrogen, and oxygen isotope chemistries of the interstitial fluids and dissolved gases of the host sediment. The ikaite crystal faithfully records in its zonal structure the changing carbon isotope ratio of the total dissolved carbon dioxide pool as it gradually diminishes during methanogenesis (δ13Cikaite = −17.5 to −21.4‰). These changes in the crystal's host environment follow general Rayleigh carbon isotope fractionation. The oxygen isotopes of the ikaite carbonate (δ18Oikaite = 1.46 to 4.45‰) also show a strong zonal distribution, unrelated to temperature of formation, but perhaps controlled by the degree of recrystallization of ikaite to calcite. The crystal water of the ikaite is depleted 11‰ in 2H/1H (VSMOW) relative to the coexisting interstitial water, which is in excellent agreement with the isotope fractionation of other hydrated minerals. In addition to the in situ temperature and pressure, nucleation of the ikaite crystals in the Bransfield Basin sediments may be induced by the high alkalinity, high phosphate concentrations, and dissolved organic compounds. Intense microbial metabolism generates such compounds; of these, aspartic acid and glutamic acid may play an important role, as they do in biological and extracellular carbonate mineral precipitation. All indications are that low temperatures (such as of polar environments), high calcium carbonate supersaturation caused by interstitial methanogenesis, and a sufficiently large supply of dissolved phosphate and amino acids favor metastable ikaite formation. These conditions, modified by recrystallization, may be preserved in calcite glendonites, thinolites, and other calcitic pseudomorphs derived from ikaite and found throughout the ancient sedimentary record. [ABSTRACT FROM AUTHOR]

We measured the N concentrations and isotopic compositions of 44 samples of terrestrial potassic and micro- and meso-porous minerals and a small number of whole-rocks to determine the extent to which N is incorporated and stored during weathering and low-temperature hydrothermal alteration in Mars surface/near-surface environments. The selection of these minerals and other materials was partly guided by the study of altered volcanic glass from Antarctica and Iceland, in which the incorporation of N as NH4+ in phyllosilicates is indicated by correlated concentrations of N and the LILEs (i.e., K, Ba, Rb, Cs), with scatter likely related to the presence of exchanged, occluded/trapped, or encapsulated organic/inorganic N occurring within structural cavities (e.g., in zeolites). The phyllosilicates, zeolites, and sulfates analyzed in this study contain between 0 and 99,120 ppm N and have δ15Nair values of −34‰ to +65‰. Most of these minerals, and the few siliceous hydrothermal deposits that were analyzed, have δ15N consistent with the incorporation of biologically processed N during low-temperature hydrothermal or weathering processes. Secondary ion mass spectrometry on altered hyaloclastites demonstrates the residency of N in smectites and zeolites, and silica. We suggest that geological materials known on Earth to incorporate and store N and known to be abundant at, or near, the surface of Mars should be considered targets for upcoming Mars sample return with the intent to identify any signs of ancient or modern life. [ABSTRACT FROM AUTHOR]

The quartz-polymetallic veins from Caleta Argentina, Livingston Island, Antarctica consist of pyrite, chalcopyrite, galena, and sphalerite. Chalcopyrite is the most common ore mineral and with concentrations of Ag (average 240.51 ppm). Sphalerite contains Ag (average 50.82) and Au (average 0.31 ppm), and pyrite - Au from not detectable to 1.03 ppm (average 0.59 ppm) and Ag from not detectable to 54.33 ppm (average 32.52 ppm). Caleta Argentina, as one of the ore occurrences in Hurd Peninsula, has to be correlated with the other research area such as the Bulgarian Antarctic Base, the Bulgarian Beach, and Sally Rocks. [ABSTRACT FROM AUTHOR]

The quartz-polymetallic veins from Sally Rocks, Livingston Island, Antarctica are hosted in the Miers Bluff Formation, particularly in the sedimentary sequences of the Sally Rocks member, consisting of thin bedded alternation of mudstone and sandstone. The veins consist of chalcopyrite, sphalerite, galena, pyrite, and arsenopyrite. Chalcopyrite and sphalerite predominate, galena is second in distribution, and pyrite and arsenopyrite are in a subordinate amount. According to the geological setting, textures, and mineral assemblages, the ore mineralization in Sally Rocks can be determined as hydrothermal which corresponds to the genesis of the other ore occurrences in the Hurd Peninsula. [ABSTRACT FROM AUTHOR]

The Orca Seamount is a submarine volcanic structure, located in a tectonic area of the Bransfield Strait, characterized by cortical extension and roll back-type subduction. Recent investigations have described the presence of hydrothermal activity and thermophilic microorganisms in this submarine volcano, raising questions regarding the role these microorganisms might play in the environment. The presence of hydrothermal activity interacting with cold Antarctic marine waters has probably exerted a great impact on the chemistry of the Orca Seamount area, providing different types of substrates capable to support complex microbial communities. In this work, we further study the Orca Seamount area with respect to the mineralogy present in this environment and the role microorganisms might play in the biogeochemical cycles. Here we show that the assemblage of minerals detected in the Orca Seamount area is like those commonly found in other hydrothermal environments, consistent with previous investigations reporting hydrothermal activity in this zone. Sulfur- and iron-bearing minerals in addition to inorganic soluble compounds are able to support chemosynthetic microbial communities inhabiting the Orca Seamount. The role of these microorganisms on the sulfur, iron, and carbon cycle is discussed and analyzed in the context of the mineralogy and conditions of the environment. [ABSTRACT FROM AUTHOR]

Our study of a banded charnockite complex of the Mühlig-Hofmannfjella in Dronning Maud Land, Antarctica, illustrates how the combination of high-temperature (re-)crystallization processes, melts, and volatile fluids leads to complex intrusive, metasomatic, and structural relationships. The igneous complex consists of gently dipping sets of charnockite interlayered with dolerite and leucogranite. The banded complex formed primarily by magmatic processes, but with superimposed modifications by metasomatism. The charnockite has a ferroan composition and contains both orthopyroxene (Fs80–84) and olivine (Fa94–96). Zircon U-Pb dates the emplacement of charnockite at 515 Ma, and inherited zircon cores and negative εNd values of −3 to −5 indicate that the age of the source of the magma was about 1100 Ma. Neodymium isotopes were not homogenized during the Cambrian magmatic event, which suggests that the generation and emplacement of the magma took place in separate batches during construction of the banded complex. By contrast, the Rb-Sr system in the charnockite was extensively homogenized, likely because of the superimposed late-magmatic fluid activity, which also produced the bands and networks of leucogranites. These events occurred during the late stages of the assembly of Gondwana, with postcollisional extension and mantle upwelling maintaining a high heat flow. [ABSTRACT FROM AUTHOR]

This study presents monazite and rutile U–Pb and hornblende and biotite 40Ar/39Ar geochronological data for high-grade rocks of the eastern Grenville-aged Rayner orogen at Mount Brown in order to analyse the extent and degree of Pan-African-aged reworking. Monazite from paragneiss yields U–Pb ages of 910 Ma for larger granular grains and 670–630 Ma for smaller globular beads around garnet porphyroblasts or hosted by symplectites. Rutile from leucogneiss yields U–Pb ages of 520–515 Ma. Hornblende and biotite from different rock types yield 40Ar/39Ar plateau ages of 744 and 520–505 Ma, respectively. Combining these results with published zircon U–Pb age data suggests that granulite facies metamorphism occurred at 910 Ma, with a local low-temperature fluid flow event at 670–630 Ma and thermal reworking at 520–505 Ma. The older age of 744 Ma may reflect cooling or partial resetting of the hornblende 40Ar/39Ar system, indicating that Pan-African-aged reworking did not exceed temperatures much higher than the hornblende Ar closure temperature. These data also suggest that the complete isotopic resetting of some minerals may occur without the growth of new mineral phases, providing an example of the style of reworking that is likely to occur in polymetamorphic terranes. [ABSTRACT FROM AUTHOR]

Human driven changes such as increases in oceanic CO2, global warming, petroleum hydrocarbons and heavy metals may negatively affect the ability of marine calcifiers to build their skeletons/shells, especially in polar regions. We examine spatio-temporal variability of skeletal Mg-calcite in shallow water Antarctic marine invertebrates using bryozoan and spirorbids as models in a recruitment experiment of settlement tiles in East Antarctica. Mineralogies were determined for 754 specimens belonging to six bryozoan species (four cheilostome and two cyclostome species) and two spirorbid species from around Casey Station. Intra- and interspecific variability in wt% MgCO3 in calcite among most species was the largest source of variation overall. Therefore, the skeletal Mg-calcite in these taxa seem to be mainly biologically controlled. However, significant spatial variability was also found in wt% MgCO3 in calcite, possibly reflecting local environment variation from sources such as freshwater input and contaminated sediments. Species with high-Mg calcite skeletons (e.g. Beania erecta) could be particularly sensitive to multiple stressors under predictions for near-future global ocean chemistry changes such as increasing temperature, ocean acidification and pollution. [ABSTRACT FROM AUTHOR]

Environmental stressors impact marine larval growth rates, quality and sizes. Larvae of the Antarctic bivalve, Laternula elliptica, were raised to the D-larvae stage under temperature and pH conditions representing ambient and end of century projections (-1.6°C to +0.4°C and pH 7.98 to 7.65). Previous observations using light microscopy suggested pH had no influence on larval abnormalities in this species. Detailed analysis of the shell using SEM showed that reduced pH is in fact a major stressor during development for this species, producing D-larvae with abnormal shapes, deformed shell edges and irregular hinges, cracked shell surfaces and even uncalcified larvae. Additionally, reduced pH increased pitting and cracking on shell surfaces. Thus, apparently normal larvae may be compromised at the ultrastructural level and these larvae would be in poor condition at settlement, reducing juvenile recruitment and overall survival. Elevated temperatures increased prodissoconch II sizes. However, the overall impacts on larval shell quality and integrity with concurrent ocean acidification would likely overshadow any beneficial results from warmer temperatures, limiting populations of this prevalent Antarctic species. [ABSTRACT FROM AUTHOR]

Abstract: The age and composition of the 14×106 km2 of Antarctica''s surface obscured by ice is unknown except for some dated detrital minerals and erratics. In remedy, we present four new analyses (U–Pb age, TDM, εHf, and rock type) of detrital zircons from Neogene turbidites as proxies of Antarctic bedrock, and review published proxies: detrital hornblendes analysed for Ar–Ar age and bulk Sm–Nd isotopes; Pb isotope compositions of detrital K-feldspars; erratics and dropstones that reflect age and composition; and recycled microfossils that reflect age and facies. This work deals with the 240°E–0°–015°E sector, and complements Veevers and Saeed''s (2011) analysis of the 70°E–240°E sector. Each sample is located in its ice-drainage basin for backtracking to the potential provenance. Gaps in age between sample and upslope exposure are specifically attributable to the provenance. The major provenance of detritus west of the Antarctic Peninsula (AP) is West Antarctica, and of detritus east of the AP East Antarctica. We confirm that the Central Antarctic provenance about a core of the Gamburtsev Subglacial Mountains (GSM) and the Vostok Subglacial Highlands (VSH) contains a basement that includes igneous (mafic granitoids) and metamorphic rocks with peak U–Pb ages of 0.65–0.50, 1.20–0.9, 2.1–1.9, 2.8–2.6, and 3.35–3.30Ga, TC, εHf, and rock type) of detrital zircons from Neogene turbidites as proxies of Antarctic bedrock, and review published proxies: detrital hornblendes analysed for Ar–Ar age and bulk Sm–Nd isotopes; Pb isotope compositions of detrital K-feldspars; erratics and dropstones that reflect age and composition; and recycled microfossils that reflect age and facies. This work deals with the 240°E–0°–015°E sector, and complements Veevers and Saeed''s (2011) analysis of the 70°E–240°E sector. Each sample is located in its ice-drainage basin for backtracking to the potential provenance. Gaps in age between sample and upslope exposure are specifically attributable to the provenance. The major provenance of detritus west of the Antarctic Peninsula (AP) is West Antarctica, and of detritus east of the AP East Antarctica. We confirm that the Central Antarctic provenance about a core of the Gamburtsev Subglacial Mountains (GSM) and the Vostok Subglacial Highlands (VSH) contains a basement that includes igneous (mafic granitoids) and metamorphic rocks with peak U–Pb ages of 0.65–0.50, 1.20–0.9, 2.1–1.9, 2.8–2.6, and 3.35–3.30Ga, TDM ages of 1.55Ga, and of zircons of 1200–900Ma age with positive εHf lies beneath the ice in East Antarctica south and southeast of Dronning Maud Land within the Antarctic part of the East African–Antarctic Orogen. Zircons with the additional ages of 1.7–1.4Ga, 2.1–1.9Ga, and 3.35–3.00Ga have a potential provenance in the GSM. [Copyright &y& Elsevier]C of 3.6–1.3Ga, and mainly negative εHf. The potential provenance of zircons of 650–500Ma age with TDM C ages of 1.55Ga, and of zircons of 1200–900Ma age with positive εHf lies beneath the ice in East Antarctica south and southeast of Dronning Maud Land within the Antarctic part of the East African–Antarctic Orogen. Zircons with the additional ages of 1.7–1.4Ga, 2.1–1.9Ga, and 3.35–3.00Ga have a potential provenance in the GSM. [Copyright &y& Elsevier]

- A metamorphosed lithic clast was discovered in the CM chondrite Grove Mountains 021536, which was collected in the Antarctica by the Chinese Antarctic Research Exploration team. The lithic clast is composed mainly of Fe-rich olivine (Fo62) with minor diopside (Fs9.7-11.1Wo48.3-51.6), plagioclase (An43-46.5), nepheline, merrillite, Al-rich chromite (21.8 wt% Al2O3; 4.43 wt% TiO2), and pentlandite. Δ17O values of olivine in the lithic clast vary from −3.9‰ to −0.8‰. Mineral compositions and oxygen isotopic compositions of olivine suggest that the lithic clast has an exotic source different from the CM chondrite parent body. The clast could be derived from strong thermal metamorphism of pre-existing chondrule that has experienced low-temperature anhydrous alteration. The lithic clast is similar in mineral assemblage and chemistry to a few clasts observed in oxidized CV3 chondrites (Mokoia and Yamato-86009) and might have been derived from the interior of the primitive CV asteroid. The apparent lack of hydration in the lithic clast indicates that the clast accreted into the CM chondrite after hydration of the CM components. [ABSTRACT FROM AUTHOR]

Meteoric water that interacted with minerals during retrogressive metamorphism and hydrothermalism in the late-stage of mountain building processes contains hydrogen and oxygen isotopes that are potential proxies for palaeoelevation reconstruction in Antarctica. The effects of temperature on meteoric isotopic signatures, meteoric crustal infiltration processes, and the mechanisms of capture and preservation of meteoric δD and δ18O values in rock-forming minerals are discussed. Special emphasis is given to Antarctica's geographical high-latitude position and climatic fluctuations over time and to the high-mountain ranges of continental Antarctica, which were tectonically active regions in the past. In this context, a new compilation of recent Antarctic snow and ice δD and δ18O data is presented, by which we demonstrate that net elevations versus isotopic depletions are positively correlated for continental Antarctica — a prime requisite when estimating palaeoelevations. [ABSTRACT FROM AUTHOR]

Discusses the role of iron-rich diagenetic minerals as biomarkers of microbial activity in granitic rocks of Antarctica. Comparison of aluminum, silicon and iron composition of diagenetic mineral deposits associated with live bacteria and hyphae; Exploration of bio-induced mineral transformation process by high resolution transmission electron microscopy.

Presents a study which examined the stability of fluorine-rich phlogopite in ultra-high-temperature metapelitic granulites from the Napier Complex, East Antarctica. Petrography and mineralogy; Chemistry and textual characteristics of individual minerals; Interpretation of the textual and composional data.

Abstract Generally, P–T pseudosections for reduced compositional systems, such as K2O–FeO–MgO–Al2O3–SiO2–H2O, Na2O–K2O–FeO–MgO–Al2O3–SiO2–H2O and MnO–K2O–FeO–MgO–Al2O3–SiO2–H2O, are well suited for inferring detailed P–T paths, comparing mineral assemblages observed in natural rocks with those calculated. Examples are provided by P–T paths inferred for four metapelitic samples from a 1 m2 wide outcrop of the Herbert Mountains in the Shackleton Range, Antarctica. The method works well if the bulk composition used is reconstituted from average mineral modes and mineral compositions (AMC) or when X-ray fluorescence (XRF) data are corrected for Al2O3 and FeO. A plagioclase correction is suitable for Al2O3. Correction for FeO is dependent on additional microscopic observations, e.g. the kind and amount of opaque minerals. In some cases, all iron can be treated as FeOtot, whereas in others a magnetite or hematite correction yields much better results. Comparison between calculated and observed mineral modes and mineral compositions shows that the AMC bulk composition is best suited to the interpretation of rock textures using P–T pseudosections, whereas corrected XRF data yield good results only when the investigated sample has few opaque minerals. The results indicate that metapelitic rocks from the Herbert Mountains of the Northern Shackleton Range underwent a prograde P–T evolution from about 600 °C/5.5 kbar to 660 °C/7 kbar, followed by nearly adiabatic cooling to about 600 °C at 4.5 kbar. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the unique sapphirine, orthopyroxene and quartz granulite from Mount Riiser-Larsen in the Tula Mountains of Enderby Land, East Antarctica. Occurrence and geological setting; Sample description and textural features; Mineral chemistry and zoning features; Discussion and conclusion.

Presents a study of clay-mineral assemblages from East Antarctica. Impact of the changes in the clay associations; Recording of the high-latitude climatic episode; Evidence of a progression in the clay assemblages during the latest Paleocene.

Presents a study on the mineral analysis of various fluorine and chlorine-bearing minerals from the high-grade metamorphic terrain of Dronning Maud Land, Antarctica. What are fluorine and chlorine; Incorporation of these fluids into many small rocks; Calculation of water and halogen acid fugacities from biotite-olivine quartz equilibria.

A group of ultramafic xenoliths hosted in Cenozoic hypabyssal rocks from Harrow Peaks (northern Victoria Land, Antarctica) show textural and geochemical features far removed from anything previously observed in mantle xenoliths of this region and elsewhere in Antarctica. They consist of spinel-bearing lherzolites and harzburgites, characterised by a predominant equigranular texture with orthopyroxene modal contents remarkably higher in lherzolites (18–26 volume%) with respect to the harzburgite (13 vol%), one orthopyroxenite, and three composite xenoliths. The latter are formed by an olivine-dominant assemblage (olivine > 70%) crosscut by large monomineralic (amphibole or clinopyroxene) or bimineralic (amphibole + clinopyroxene) veins. No significant correlation was observed between the lithology and the Fo content (90.21–82.81) of olivine, suggesting that these rocks could be derived from a cumulus process. The presence of the orthopyroxenite suggests that the inferred melt/s from which they stemmed was close (or even above) to silica saturation. Based on major and trace-element mineral/melt and mineral/mineral equilibrium modelling, these rocks were formed by progressive extraction of olivine from a high magnesium (Mg = 72)—high temperature (~ 1300 °C) melt following a very short fractionation line. Thermobarometric results indicate the stationing of Harrow Peaks cumulates in the P field of 1.3 ± 0.2 (dunites)—0.5 ± 0.2 (orthopyroxenite) GPa. These values well match the crust/mantle boundary (Moho) of the region. The combined geochemical and petrological data suggest that Harrow Peaks melts could be related to the initial stage of the Jurassic Ferrar magmatism, whose deep cumulates were subsequently affected by the Cenozoic alkaline metasomatism, widely detected in the northern Victoria Land lithosphere and responsible for the formation of the late amphibole/amphibole + clinopyroxene veins. [ABSTRACT FROM AUTHOR]

The article reports that paper warns the ability of Australia to preserve massive Antarctic sovereignty claim is under threat, according to the policy paper by Lowy Institute. It says that the paper issued on August 8, 2011 questioned the ability of Australia to preserve its claim to 42% of the continent. Moreover, the paper notes that limited Antarctic activity of Australia is based on environmental and science issues and does not reflect energy concerns or national security.

Presents information on chemical compositions of spherules extracted from a sample of till from the Meteorite Moraine at the Lewis Cliff ice tongue in Antarctica. Reasons for indicating the extraterrestrial origin of spherules; Mineral standards used in the calibration of electron microscope with x-ray analyzer; Concentrations of chemicals used in the analysis of spherules; Results of the study.