Graham Land Research Articles

Cretaceous magmatism in the Antarctic Peninsula and its tectonic implications

Periods of cessation, resumption and enhanced arc activity are recorded in the Cretaceous igneous rocks of the Antarctic Peninsula. We present new geochronological (laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) zircon U–Pb) analyses of 36 intrusive and volcanic Cretaceous rocks, along with LA-ICP-MS apatite U–Pb analyses (a medium-temperature thermochronometer) of 28 Triassic–Cretaceous igneous rocks of the Antarctic Peninsula. These are complemented by new zircon Hf isotope data along with whole-rock geochemistry and isotope (Nd, Sr and Pb) data. Our results indicate that the Cretaceous igneous rocks of the Antarctic Peninsula have geochemical signatures consistent with a continental arc setting and were formed during the interval c. 140–79 Ma, whereas the main peak of magmatism occurred during c. 118–110 Ma. Trends in ε Hf t (zircon) combined with elevated heat flow that remagnetized rocks and reset apatite U–Pb ages suggest that Cretaceous magmatism formed within a prevailing extensional setting that was punctuated by periods of compression. A noteworthy compressive period probably occurred during c. 147–128 Ma, triggered by the westward migration of South America during opening of the South Atlantic Ocean. Cretaceous arc rocks that crystallized during c. 140–100 Ma define a belt that extends from southeastern Palmer Land to the west coast of Graham Land. This geographical distribution could be explained by (1) a flat slab with east-dipping subduction of the Phoenix Plate, or (2) west-dipping subduction of the lithosphere of the Weddell Sea, or (3) an allochthonous origin for the rocks of Alexander Island. A better understanding of the geological history of the pre-Cretaceous rocks of Alexander Island and the inaccessible area of the southern Weddell Sea is required. Supplementary material: A description of the methods used in this study and the complete dataset are available at https://doi.org/10.6084/m9.figshare.c.6089274

Skua and plant dispersal: lessons from the Argentine Islands – Kyiv Peninsula region in the maritime Antarctic

Birds are one of the most likely dispersal vectors for plants in Antarctica. We studied the nesting behavior of south polar skua Catharacta maccormicki and brown skua Catharacta antarctica lonnbergi to assess their potential role in ornithochory in the Argentine Islands – Kyiv Peninsula region. Nest samples were collected during 2009–2020 years in the Argentine Islands – Kyiv Peninsula region including all islands and coasts of the Graham Land from the Lemaire Channel to the islands of Berthelot Islands from north to south and extending from west to east from the Roca Islands, Cruls Islands, Rasmussen Point to the coast. We found that skuas utilize different nest building materials, including bryophytes, vascular plants (hairgrass Deschampsia antarctica) and lichens. In south polar skua nests, mosses and lichens dominate in the nest material; in brown skuas Deschampsia antarctica and mosses dominate. Both bird species likely collect nest components from nearby vegetation formations (< 1 m distant). We conclude that C. maccormicki and C. antarctica lonnbergi are not selective in their choice of plant species, simply using the materials that dominate near the nest. Therefore, both species carry these materials from nearby sites, and only occasionally bring them from distant places. In conclusion, for both species we did not find any evidence to support their involvement in long‐distance ornithochory (stomatochory) in the region.

Oceanographic and climatic influences on Trooz Glacier, Antarctica during the Holocene

To evaluate the significance of recent widespread glacial recession in the Antarctic Peninsula, it is imperative to extend the limited instrumented record of glacier change with long sedimentary archives of the Holocene. Reconstructing glacial histories that capture the variability of environments in the Antarctic Peninsula will enable better constraint of ocean and climate forcings on regional glacial stability. Two sediment cores are analyzed from the 2007 RV/IB N.B. Palmer cruise to Collins Bay, the embayment immediately offshore Trooz Glacier on the Graham Land coast, and provide an archive to test controls on long-term stability of outlet glaciers in an open bay setting. Radiocarbon and Lead-210 (a short-lived radioisotope) age-depth models provide a timeline for Trooz Glacier behavior and associated oceanographic changes over the last 10,000 years.Magnetic susceptibility, grain size, diatom assemblage, total organic carbon, nitrogen, and stable isotopes of organic carbon are utilized as proxies for changing glacial and ocean conditions. Outer Collins Bay deglaciated by ∼10000 cal yr B.P. Diatom abundance and organic content signal productivity increase during further glacial recession from ∼8900 to 6100 cal yr B.P., which coincided with upwelling of relatively warm Circumpolar Deep Water into the bay. High productivity, characterized by Thalassiosira antarctica-dominated diatom assemblages with prominence of Fragilariopsis kerguelensis, indicate open marine conditions with incursion of offshore currents into the bay from ∼6100 to 760 cal yr B.P. A sharp decrease in organic content, diatom abundance, and grain size indicate more sea ice and ice-tongue/ice-canopy advance from ∼760 to 240 cal yr B.P., when the floating ice canopy in outer Collins Bay retreated to near its present-day position and productivity increased. During the period of the 1950's to 1990's, Trooz Glacier was one of only two Antarctic Peninsula glaciers that advanced slightly. Over the Holocene, oceanographic forcing dominated the long-term stability of Trooz Glacier due to its open aspect, and it is unknown how Trooz Glacier will respond to continued influence of Circumpolar Deep Water in the future. Understanding ocean forcings on glacial stability, together with other local controls like drainage basin configuration and bay geometry, should help contextualize the modern retreat and improve prediction of glacial response to prevalent Circumpolar Deep Water circulation in this dynamic region.

Gentoo Penguins (Pygoscelis papua) started using mosses as nesting material in the southernmost colony on the Antarctic Peninsula (Cape Tuxen, Graham Land)

Gentoo Penguins (Pygoscelis papua) started using mosses as nesting material in the southernmost colony on the Antarctic Peninsula (Cape Tuxen, Graham Land)

CO1 Metabarcoding of Marine Water Samples from the 2nd Turkish Antarctic Expedition (TAE2) Highlights the Deficiencies in the Reference Barcoding Databases for the Continent

Based on climate projections, the Antarctic Peninsula is one of the regions on the earth expected to be most drastically affected by climate change in the 2nd half of the 21st century. In order to establish baseline levels of marine biodiversity using the environmental DNA approach, we undertook metabarcoding based on the CO1 gene. Samples were collected using 0.22 mM pore-sized Sterivex filters during TAE2 undertaken in 2018, from one site at Deception Island (2 filters), one site at Nansen Island (2 filters), and three sites (one offshore) at Robert Island. A total of 20 taxa were identified (unique hits with BLAST percent identity ≥ 97%) belonging to three kingdoms (Chromista, Plantae, Animalia), nine phyla, 11 classes, 17 orders, 19 families, and 20 genera. Of these, 18 were identified to the species level, one to the genus level, and the other one to the family level. Genetically identified taxa included seven planktonic algae, nine seaweeds, a stalked jellyfish, a nematode, a planktonic copepod, and a demersal fish. In addition, 129 unique OTUs were detected (unique hits with BLAST percent identity < 97%) as unidentified. These results indicate the high levels of undocumented genetic diversity (without CO1 barcode sequences in GenBank) in the Antarctic Peninsula region and adjacent waters, and the need for more work to complete the reference barcode databases for the continent. A dendrogram resulting from cluster analysis (Bray-Curtis similarity measure, group-average linkage) based on the presence/absence data of 20 identified species revealed three well-defined sample (i.e. filter containing DNA fragments of multiple taxa) groups, which almost coincided with their geographical locations. First group included samples (filters) collected from the coast of Deception Island and the second one from the coast of Robert Island, both in the South Shetland Islands, off the northern tip of the Antarctic Peninsula. The third group included samples from Nansen Island coast (off the west coast of Graham Land, Antarctic Peninsula) together with the only sample collected offshore, off Robert Island. The significance of this clustering, thus the difference among sampling sites with regard to species composition, was confirmed by Analysis of Similarity (ANOSIM) results (Global R = 0.982, p = 0.001). The highest number of identified taxa (per filter) and unidentified OTUs (per filter) were observed offshore off Robert Island. Considering that all of the other sampling sites were by the coasts of islands, this observation indicates i) the offshore waters might contain more DNA-bearing material than coastal sites, and/or ii) a methodological issue where the high phytoplankton and suspended matter concentrations by the coasts created a bottleneck in terms of capturing actual species diversity at the coasts, due to clogging of filters by phytoplankton and fine suspended particles.

Chapter 2.2b Palmer Land and Graham Land volcanic groups (Antarctic Peninsula): petrology

Abstract Large-volume rhyolitic volcanism along the proto-Pacific margin of Gondwana consists of three major episodes of magmatism or ‘flare-ups’. The initial episode (V1) overlaps with the Karoo–Ferrar large igneous provinces at c. 183 Ma. A second (V2) episode was erupted in the interval 171–167 Ma, and a third episode (V3) was emplaced in the interval 157–153 Ma. The magmatic events of the V1 and V2 episodes of the Antarctic Peninsula are reviewed here describing major and trace elements, and isotopic (Sr, Nd, O) data from rhyolitic volcanic rocks and more minor basaltic magmatism. An isotopically uniform intermediate magma developed as a result of anatexis of hydrous mafic lower crust, which can be linked to earlier, arc-related underplating. The subsequent lower-crust partial melts mixed with fractionated mafic underplate, followed by mid-crust storage and homogenization. Early Jurassic (V1) volcanic rocks of the southern Antarctic Peninsula are derived from the isotopically uniform magma, but they have mixed with melts of upper-crustal paragneiss in high-level magma chambers. The V2 rhyolites from the northern Antarctic Peninsula are the result of assimilation and fractional crystallization of the isotopically uniform magma. This process took place in upper-crust magma reservoirs involving crustal assimilants with an isotopic composition akin to that of the magma. A continental margin-arc setting was critical in allowing the development of an hydrous, fusible lower crust. Lower-crustal anatexis was in response to mafic underplating associated with the mantle plume thought to be responsible for the contemporaneous Karoo magmatic province and rifting associated with the initial break-up of Gondwana.

Current status of Belgica antarctica Jacobs, 1900 (Diptera: Chironomidae) distribution by the data of Ukrainian Antarctic Expeditions

Given the recent climate changes and their impact on the Antarctic Peninsula ecosystems, the emergence of invasive species, and increased tourism activity in this region, monitoring changes in the habitats of species native to the Antarctic Peninsula region is necessary. One such species is the Antarctic midge Belgica antarctica (Chironomidae). This insect is endemic to the Antarctic Peninsula and adjacent islands. Thorough studies of changes in the range of this species have not been performed in recent decades. In this study, we present the area of Belgica antarctica according to the collections of biological samples during 2007–2021 (XII, XIV, XVI, XXIV, and XXV Ukrainian Antarctic Expeditions). This Antarctic midge was recorded at 26 localities on the Antarctic Peninsula and 212 localities on 55 surrounding islands between 66°08′38.4′′ S, 65°43′37.1′′ W (Cape Evensen, Stresher Peninsula, opposite the Marie Island, west coast of Graham Land) and 62°11′44.7′′ S, 58°57′40.6′′ W (King George Island, South Shetland Islands) from south-west to north-east.

ІНТРУЗИВНО-МАГМАТИЧНІ УТВОРЕННЯ АРХІПЕЛАГУ ВІЛЬГЕЛЬМА ЗАХІДНОЇ АНТАРКТИКИ (ЧАСТИНА 1 – ІНТРУЗИВИ ГАБРОЇДІВ, ДІОРИТІВ ТА ГРАНІТОЇДІВ)

The Wilhelm Archipelago and the adjacent coast of Graham Land are typical areas of calc-alkaline magmatism associated with the protracted evolution of the Antarctic Peninsula igneous belt. The authors studied intrusive complexes of the Wilhelm Archipelago (WA) in order to characterize their geographical distribution, geological occurrence and age, mineralogical and petrographical features. Geological surveys revealed that gabbro, diorite, and granitoid intrusions are widespread on the WA. Due to the processes of tectonic uplift and exhumation, both apical and bottom parts of individual intrusive bodies can be exposed on the modern erosion level. Recent geological observations have shown that plutons of different ages intersect each other in a complex sequence. This made it possible to determine their relative geological age and reconstruct the general direction of the deep magmatic development from the Early Cretaceous to the Early Paleogene, inclusive. It has been proved that the oldest massifs of gabbroids are parts of much larger intrusive bodies. They were formed in the period between the Jurassic and the Early Cretaceous periods. Crystallization differentiation of basaltic magmas gave them various scale layering. In the bottom parts of gabroid intrusions there were conditions for the formation of Fe-Ti-V and Cu-Ni-EPG mineralization. Diorite and granitoid intrusions occupy much larger areas compared to gabbroids. The formation of diorite intrusions took place in the period between the Early Cretaceous and the Paleocene. Although the oldest gabbroids were formed much earlier than diorites, the phenomena of magmatic mingling in the latter indicate that magmas of basic and intermediate composition could also synchronously intrude in common magmatic chambers. Granitoid magmatism on the WA covers the Late Cretaceous and the Paleogene periods. Most granitoid intrusions formed in the Paleocene after the main phase of tectonic deformations. Cu-Mo mineralization may be associated with these intrusions.

Trace metal concentrations and body condition in adult Adélie penguins (Pygoscelis adeliae) from the western Antarctic Peninsula

Adélie penguins (Pygoscelis adeliae) are seabirds that live exclusively in Antarctica, one of the planet's last pristine areas. However, this remote region is experiencing a continuing expansion of human activities that may affect Antarctic fauna. Trace metals constitute a menace to seabirds because they can adversely affect their health. There is a lack of studies relating to metals' levels in feathers with morphological parameters of seabirds. Trace metal levels were measured in Adélie penguin feathers and their body condition through the relative condition factor (ReCF) in adult individuals from two South Shetland Islands locations and two from Graham Land. Consequently, we determined the levels of some metals in feathers to see any relationship with morphological parameters linked to the bird's health. Our results showed significant differences in metals among locations studied and a significant relationship between ReCF with Cu and Zn in one of the South Shetland Islands. Also, penguins exhibited a significantly lower weight. We found a positive correlation between non-essential with essential metals, indicating that Cu acts as a detoxifying agent for Cr, Cd, and Pb. In contrast, Se could be for V and Pb. Although the relationship between most metals with ReCF was not significant, some site-specific factors may be influencing it, whereas metals may be affecting the organisms at low biological levels. Molecular, biochemical, and genetic studies are required to elucidate this issue.

First record of Serratia marcescens from Adelie and Gentoo penguin faeces collected in the Wilhelm Archipelago, Graham Land, West Antarctica

First record of Serratia marcescens from Adelie and Gentoo penguin faeces collected in the Wilhelm Archipelago, Graham Land, West Antarctica

Helminths of antarctic rockcod Notothenia coriiceps (Perciformes, Nototheniidae) from the akademik Vernadsky station area (Argentine Islands, West Antarctica): new data on the parasite community

The aim of our study was to update the information on taxonomic diversity and structure of the parasite community of Antarctic rockcod, Notothenia coriiceps in the coastal water off the Argentine Islands (Wilhelm Archipelago, Graham Land, West Antarctica). The material for this study was collected in 2014–2015 at the Ukrainian Antarctic station “Akademik Vernadsky”. More than 8,500 specimens of parasites from 106 host specimens were collected and identified. All fishes were found to be infected with helminths; 25 helminth species were identified. Acanthocephalans were recorded in 93.4 % of hosts; eight species of acanthocephalans (Metacanthocephalus rennicki, M. johnstoni, M. campbelli, M. dalmori, Aspersentis megarhynchus, Corynosoma hammani, C. pseudohammani, and C. evae) were found. Nematodes were found in 96.2 % of fishes; larval stages of Pseudoterranova sp., Contraceacum sp., Anisakis sp. and adults Ascarophis nototheniae and Dichelyne fraseri were identified. Trematodes were found in 94.3 % of fishes; seven species (Macvicaria georgiana, Neolebouria antarctica, Lepidapedon garrardi, Genolinea bowersi, Elytrophalloides oatesi, Lecithaster macrocotyle, Derogenes johnstoni) were identified. Larval stages of cestodes (Diphyllobothrium sp. and tetraphyllidean metacestodes) and the monogenean species Pseudobenedenia nototheniae were found. Our studies revealed significant changes in the structure of the parasite community of N. coriiceps during the last decade.

Gabbroides of Peterman island (West Antarctica). First information on geochemistry

Peterman Island is located in the archipelago of the Wilhelm Islands on the west coast of the Antarctic Peninsula (Graham Land). It is composed of gabbroids and granitoids of the Andean complex, which formed almost 100 million years later than the volcanic group of the Antarctic Peninsula. To clarify their genesis and geodynamic conditions of formation, gabbroids of the Andean complex are of particular interest, since the petrological models of their formation are well developed. Gabbroid intrusions comprise small bodies that are widespread along the Antarctic Peninsula. Among them stand out olivine gabbros, normal gabbros, norites and hornblende gabbros. Also are found small bodies of melanogabbro-pegmatites and intramagmatic dykes, that are associated with the manifestations of ore mineralization of magnetite, ilmenite and sulfides. For this reason, they are of interest for both the minerals search and for solving the question of their genesis. To this end, we performed geochemical studies of Peterman Island gabbroids. Gabbroids of Peterman Island are represented by amphibolized medium-grained gabbro with hypidiomorphic texture. Among them, xenoliths of thinly stratified gabbroids 3 × 8 m in size were found, which are characteristic of stratified intrusions, for example, Stillwater, Bushveld, etc. Gabbroids of Peterman Island have low content of silica and potassium and according to the petrochemical characteristics correspond to peridotite gabbro. They have low contents of Cr, Ni, V and high strength lithophilic Y and Nb elements. Gabbroids have been crystallized from basic magma, differentiated in the intermediate crustal magma chambers. Positive anomalies of Sr, Eu, and Ti in the multielement diagrams and positive anomalies of europium Eu/Eu* suggest the accumulation of plagioclase and apparently, ilmenite in the magmatic chamber. The primary magma source for gabbroids was probably the primitive mantle (PM). Gabbroids are contaminated with crustal matter. This contamination is probably due to their regressive metamorphism, caused by the introduction of later intrusions of Andean complex granitoid. Finely layered xenolithic gabbroids do not differ from other homogeneous gabbros of Peterman Island in terms of chemical composition.This xenolith most likely represents a part (fragment) of the wall of the magma chamber in which the differentiation of the initial main magma took place. According to the obtained geochemical data, a wide range of compositions of the Andean complex gabbroids formed as a result of crystallization differentiation of magma melted from rocks of the composition of the primitive mantle (PM) in crustal magma chambers, which also resulted in the accumulation of ore elements — V, Co, and Cu in the residual magmatic melts.

The Gondwanan margin in West Antarctica: Insights from Late Triassic magmatism of the Antarctic Peninsula

Triassic orthogneisses of the Antarctic Peninsula provide evidence for the Palaeozoic and Mesozoic geological evolution of southern Gondwana within Pangaea. These rocks are sporadically exposed in southeastern Graham Land and northwestern Palmer Land, although reliable geochronological, geochemical and isotopic data are sparse. We combine new geochronological (LA-ICP-MS zircon UPb), geochemical, and zircon (Hf, O) and whole rock isotopic (Nd, Sr and Pb) data to constrain the age and Triassic – Palaeozoic tectonic setting of these rocks. Zircon cores record Palaeozoic arc magmatism between 253 ± 2 and 528 ± 6 Ma, which was mainly located to the west of the Eastern Palmer Land Shear Zone (Central Domain; Vaughan and Storey, 2000). The arc is considered to be an extension of contemporaneous Palaeozoic arcs that have been identified along the Pacific margin of South America and the Thurston Island Block. Regions to the east of the Palmer Land Shear Zone (Eastern Domain, Vaughan and Storey, 2000) were located distal from the Terra Australis Margin, and possibly resided within Sunsas-aged belts within Pangaea. Triassic continental arc, calc-alkaline magmatism during 223–203 Ma modified the crust of the Antarctic Peninsula on both sides of the Eastern Palmer Land Shear Zone. Magmatic sources included igneous and sedimentary crustal material, which formed by crustal reworking during Sunsas- and Braziliano-aged orogenesis, and Palaeozoic arc magmatism. Arc magmatism accompanied sinistral extension which brought both domains into the arc and resulted in steady oceanward migration of the Triassic arc during the Middle – Late Triassic. We propose that sinistral displacement occurred along the Eastern Palmer Land Shear Zone, and this structure was active as early as the Triassic. Finally, we conclude that both the Eastern and Central Domains are autochthonous to Gondwana.

The Distribution of the Antarctic Limpet Nacella concinna (Nacellidae) on Underwater Landscapes of the Meek Channel, Argentine Islands, Graham Land

Objective(s). To clarify the patterns of Nacella concinna (Nacellidae) distribution in the water area of the Argentine Islands Archipelago (Meek Channel). Methods. Morphometric, statistical, cartographic methods as well as geoinformation technologies were used. Results. Analyzed the patterns of mollusc distribution on different transects, taking into account their morphometric characteristics — the length of the shell, the mollusс weight, the population density. It is determined that the distribution of Nacella concinna subpopulations does not have any visible strict regularity. At different transects with an insignificant exception the morphometric characteristics of the mollusсs are distributed both in classical and non-classical models. At the MK1 transect is shown the classical model of the distribution of morphometric characteristics, namely with an increase in the mollusс population density, the morphometric characteristics (shell length and weight of the mollusс) tend to decrease. At the MK2 transect is shown non-classical distribution model. The morphometric characteristics (shell length, mollusс weight) increase with an increase in the population density of the molluscs. At the MK3 transect is shown the classical distribution model, but a characteristic feature is an increase in the population density up to 5 m depth and a gradual decrease in the population density from 5 to 20 m. Geoinformation models of the Nacella concinna distribution by depth in the water area of the Ukrainian Antarctic Akademik Vernadsky station were constructed. Conclusions. Maps of the distribution of the Nacella concinna population were created for this region for the first time. The dimensional classes of the Nacella concinna subpopulation from selected water areas of the Argentine Islands were described.

A comparison of modelled ice thickness and volume across the entire Antarctic Peninsula region

ABSTRACTUnderstanding Antarctic Peninsula glacier evolution requires distributed ice thickness and subglacial topography. To date, 80% of the Antarctic Peninsula mainland ice volume has only been determined at low-resolution (1 km post spacing) and the distributed ice thickness of glaciers on surrounding islands has never been quantified. In this study we applied a perfect plasticity model, selected for its simplicity, low data requirements and minimal parameterisation, to estimate glacier thickness, subglacial topography and ice volume for the entire Antarctic Peninsula region. We compared the output of this simple model to that of a more sophisticated but spatially-restricted model and also to the spatially-coarse but more extensive Bedmap2 dataset. The simple model produced mean differences of 1.4 m (std. dev. 243 m) in comparison with the more sophisticated approach for the mountainous parts of the Peninsula. It produced similar volumes for tidewater glaciers but gave unrealistic ice thickness around grounding lines. Ice thickness across low gradient plateau surfaces are mis-represented by a perfect plasticity model and thus for the southern part of the Peninsula only regional ice volume can be approximated by our model. Overall, with consideration of ice situated below sea level, model results suggest that Trinity Peninsula, Graham Land, the part of Palmer Land north of 74°S and all glaciers on islands contain an ice mass of ∼200 300 Gt, with sea level equivalent of 553 mm (± 11.6 mm). Of this total 8% is from glaciers on islands, 70% of which is from Alexander Island.

GEOLOGICAL POSITION AND AGE OF TUXEN-RASMUSSEN LAYERED GABBROID INTRUSION (WEST ANTARCTICA)

The latest geological research carried out during seasonal work in 2017 revealed that metamorphosed layered gabbroids, which partially outcrop along the Antarctic Peninsula Coast on Cape Tuxen and Rasmussen Island, compose sheet-like intrusive body of total dimensions more than 3 km2. Significant part of the Tuxen-Rasmussen Gabbroid Intrusion (TRGI) is submerged under Waddington Bay. Main objectives of the study were the identification of geological position of the TRGI and the clarification of its geological age. In addition to the field methods of the geological research the samples collected during this and the previous years were studied using optical and electron microscopy techniques in order to identify petrographic and mineralogical features of the gabbroids. Results of the studies confirmed previous observation that TRGI was embedded in Upper Jurassic Volcanic Group (UJVG) of Antarctic Peninsula and it was responsible for contact metamorphism of the UJVG and suffered contamination by volcanic material. Gabbroids and volcanic rocks were later intruded by granites of Late Cretaceous age, which belong to the Andean Intrusive Suite (AIS) of Graham Land. Authors define geological age of TRGI as Early Cretaceous. Previous U-Pb isotope datings of the gabbroids are believed to be “rejuvenated”. It was discovered that TRGI strikes in northeastern direction and dips steep in northwestern direction. It is assumed that intrusive body continues underwater and can outcrop at the northern shore of the Waddington Bay and at Barros Rocks direction to the southwest. Petrographical researches showed that gabbroids underwent metamorphic alteration in conditions of epidote-amphibolite facies. They bear, nevertheless, relict structural-textural features and mineral associations of mafic igneous rocks. Authors drew a conclusion that geological position and petrographical peculiarities of TRGI correspond to hypabyssal level of crystallization. Primary igneous origin is proved for the microrhythmic layering of the gabbroids. Relict mineral associations allow to identify the rocks as olivine gabbro-norites. Potential Fe-Ti-V ore specialization is emphasized according to the revealed patterns of crystal fractionation and accumulation of ilmenite and magnetite.

REGIONAL GEOLOGICAL MAPPING IN THE GRAHAM LAND OF ANTARCTIC PENINSULA USING LANDSAT-8 REMOTE SENSING DATA

Abstract. Geological investigations in Antarctica confront many difficulties due to its remoteness and extreme environmental conditions. In this study, the applications of Landsat-8 data were investigated to extract geological information for lithological and alteration mineral mapping in poorly exposed lithologies in inaccessible domains such in Antarctica. The north-eastern Graham Land, Antarctic Peninsula (AP) was selected in this study to conduct a satellite-based remote sensing mapping technique. Continuum Removal (CR) spectral mapping tool and Independent Components Analysis (ICA) were applied to Landsat-8 spectral bands to map poorly exposed lithologies at regional scale. Pixels composed of distinctive absorption features of alteration mineral assemblages associated with poorly exposed lithological units were detected by applying CR mapping tool to VNIR and SWIR bands of Landsat-8.Pixels related to Si-O bond emission minima features were identified using CR mapping tool to TIR bands in poorly mapped andunmapped zones in north-eastern Graham Land at regional scale. Anomaly pixels in the ICA image maps related to spectral featuresof Al-O-H, Fe, Mg-O-H and CO3 groups and well-constrained lithological attributions from felsic to mafic rocks were detectedusing VNIR, SWIR and TIR datasets of Landsat-8. The approach used in this study performed very well for lithological andalteration mineral mapping with little available geological data or without prior information of the study region.

Lithological and alteration mineral mapping in poorly exposed lithologies using Landsat-8 and ASTER satellite data: North-eastern Graham Land, Antarctic Peninsula

Antarctica remains a remote and logistically difficult region to conduct geological field mapping and mineral exploration. Remote sensing satellite imagery has high potential to provide a solution to overcome the difficulties and limitations associated with geological field mapping and mineral exploration in inaccessible regions. In this study, the applications of Landsat-8 and the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data were investigated to extract geological information for lithological and alteration mineral mapping in poorly exposed lithologies located in inaccessible regions. The north-eastern Graham Land, Antarctic Peninsula (AP) was selected in this study to conduct a satellite-based remote sensing mapping approach. A two-stage methodology was adopted to distinguish pixel and sub-pixel targets in the satellite images. In the first stage, Continuum Removal (CR) spectral mapping tool and Independent Components Analysis (ICA) technique were applied to Landsat-8 and ASTER spectral bands to map the pixels related to poorly exposed lithological units. The second step was established based on the application of target detection algorithms to shortwave infrared bands of ASTER for detecting spectral features attributed to alteration mineral assemblages at the sub-pixel level. Pixels composed of distinctive absorption features of alteration mineral assemblages and Si-O bond emission minima features were detected by applying CR mapping tool to reflective and thermal bands of Landsat-8 and ASTER. Anomaly pixels related to spectral features of Al-O–H, Fe, Mg-O–H and CO3 groups as well as lithological attributions from felsic to mafic rocks were detected by the implementation of ICA technique to reflective and thermal bands of Landsat-8 and ASTER. ICA method provided image maps of alteration mineral assemblages and lithological units (mafic to felsic trend) for poorly mapped and/or unmapped regions. Fractional abundance of alteration minerals such as muscovite, kaolinite, illite, montmorillonite, epidote, chlorite and biotite were detected in poorly exposed lithologies using target detection algorithms. Several prospecting areas for Cu, Mo, Au and Ag mineralization related to propyllitically and argillically altered units of Andean Intrusive Suite (AIS) were identified in the southern sector of the study region. The results of this investigation demonstrated the applicability of Landsat-8 and ASTER spectral data for lithological and alteration mineral mapping in poorly exposed lithologies located in inaccessible regions, particularly using the image processing algorithms that are capable of detecting anomaly pixels and sub-pixel targets in the remotely sensed images, where no prior information is available. In conclusion, a simple and robust satellite-based remote sensing approach for mapping poorly exposed lithologies in inaccessible regions was established, which is comprehensively applicable for lithological and alteration mineral mapping in the Antarctic environments and hydrothermal ore minerals prospecting in other inaccessible regions around the world.

Mapping alteration mineral zones and lithological units in Antarctic regions using spectral bands of ASTER remote sensing data

Geological mapping is one of the primary tasks of remote sensing. Remote sensing applications are especially useful when extreme environmental conditions inhibit direct survey such as in Antarctica. In this investigation, a satellite-based remote sensing approach was used for mapping alteration mineral zones and lithological units using Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data in the Oscar II coast area, north-eastern Graham Land, Antarctic Peninsula. Specialized band ratios and band combinations were developed using visible and near infrared, shortwave infrared (SWIR) and thermal infrared spectral bands of ASTER for detecting alteration mineral assemblages and lithological units in Antarctic environments. Constrained Energy Minimization, Orthogonal Subspace Projection and Adaptive Coherence Estimator algorithms were tested to ASTER SWIR bands for detecting sub-pixels’ abundance of spectral features related to muscovite, kaolinite, illite, montmorillonite, epidote, chlorite and biotite. Results indicate valuable applicability of ASTER data for Antarctic geological mapping.

Application of ASTER SWIR bands in mapping anomaly pixels for Antarctic geological mapping

Independent component analysis (ICA) was applied to shortwave infrared (SWIR) bands of ASTER satellite data for detailed mapping of alteration mineral zones in the context of polar environments, where little prior information is available. The Oscar II coast area north-eastern Graham Land, Antarctic Peninsula (AP) was selected to conduct a remote sensing satellite-based mapping approach to detect alteration mineral assemblages. Anomaly pixels in the ICA image maps related to spectral features of Al-O-H, Fe, Mg-O-H and CO3 groups were detected using SWIR datasets of ASTER. ICA method provided image maps of alteration mineral assemblages and discriminate lithological units with little available geological data for poorly mapped regions and/or without prior geological information for unmapped regions in northern and southern sectors of Oscar II coast area, Graham Land. The results of this investigation demonstrated the applicability of ASTER spectral data for lithological and alteration mineral mapping in poorly exposed lithologies and inaccessible regions, particularly using the image processing algorithm that are capable to detect anomaly pixels targets in the remotely sensed images, where no prior information is available.