Magma layering of gabbroids of Antarctic Peninsula batholith

Артеменко, Г.В.; Bakhmutov, V.; Samborska, I.A.; Bakhmutova, Larysa; Shpyra, V. V.

doi:10.33275/1727-7485.12.2013.242

Cited by 4 publications

(1 citation statement)

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“…(Gourdon, 1908. Близькість до УАС та відносно легка досяжність дали змогу доволі детально вивчити умови їх залягання, геологічний вік, мінералого-петрографічні та геохімічні особливості, описані у публікаціях (Mytrokhyn et al, 2017;Artemenko et al, 2013;Bakhmutov et al, 2013;Tangeman et al, 1996та Curtis, 1966. Важкодоступність більшості інших габроїдних тіл до останнього часу перешкоджала їх належному вивченню.…”

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Petrology of Gabbroids of Girard Bay (Kyiv Peninsula, Graham Coast of the West Antarctica)

Mytrokhyn,

Chertova,

Bakhmutov

2024

Mìneral. ž.

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Several new gabbroid intrusions were discovered in the process of geological surveying in the area of the Ukrainian research station in the West Antarctica. One of them is located in the hard-to-reach Girard Bay on the western coast of the Kyiv Peninsula. The authors investigated the mode of occurrence, petrography and mineral chemistry of Girard Bay gabbroids in order to clarify their geological position and petrogenetic conditions of their formation. It was found that the newly discovered gabbroids make up a stock-like intrusive body with a horizontal dimension of more than 3 km. Gabbroids unconformably intrude the Kyiv Peninsula volcanic formation. The apical part of this gabbroid intrusion is exposed fragmentarily on the southern coast of Girard Bay. The petrographic diversity of the studied gabbroids depends on the heterogeneous manifestation of local low-temperature hydrothermal transformations (amphibolization, prenitization and silicification). In addition, the presence of hidden magmatic layering, which is characteristic of other gabbroid intrusions of the region, is assumed. The main petrographic representatives are gabbronorites and amphibolized gabbros, among which mesocratic and leucocratic varieties have been identified. The gabbronorites exposed on the southern coast of Girard Bay represent one of the lowest degrees of the post-magmatic transformation. Mineralogical and petrographic features point to hypabyssal depths of their formation. The chemistry of pyroxenes and plagioclases indicates the most high-temperature conditions of crystallization in comparison with other representatives of gabbroids both on the Kyiv Peninsula and on the neighboring Wilhelm Archipelago. The geological age of Girard Bay gabbroids is preliminarily defined as post-Jurassic and requires further clarification using the isotopic geochronology methods. Given the possible post-magmatic re-equilibration of primary mineral paragenesis, zircon is recommended as a chronometer mineral.

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Petrology of Gabbroids of Girard Bay (Kyiv Peninsula, Graham Coast of the West Antarctica)

Mytrokhyn,

Chertova,

Bakhmutov

2024

Mìneral. ž.

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Magnetic field map of the Wilhelm Archipelago shelf zone, West Antarctica

Bakhmutov,

Yegorova,

Bakarzhiyeva

et al. 2023

Acta Geophys.

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The Antarctic Digital Magnetic Anomaly Project is an international research effort to construct a magnetic map of the continent based on ground, satellite, marine, and aeromagnetic surveys. This paper reports the magnetic mapping of the shelf zone in the SE part of the Wilhelm Archipelago, West Antarctica, based on magnetic surveys conducted with Zodiac boats. A spectacular feature of this area is the strong magnetic anomaly of the Antarctic Peninsula (AP) batholith, which was the product of subduction-related Mesozoic–Cenozoic arc magmatism on the former margin of Western Gondwana. We constructed and analyzed a detailed magnetic map of magnetic field anomalies using field observations of rock exposures on the islands and magnetic properties of rocks from laboratory data. The oldest volcanic rocks of Jurassic to Lower Cretaceous age relate to N-NE trending bands of negative magnetic field. The largest feature in the study area is an Upper Cretaceous/Paleogene granodiorite complex that produces a positive magnetic anomaly. Many smaller anomalies are also present over gabbroid bodies of Cretaceous age. Two-dimensional magnetic modeling shows that heterogeneities in the upper crust may have magnetic susceptibilities in the range of 0.005–0.13 SI. Magnetic field anomalies also delineate an orthogonal system of tectonic faults, including the main NE fault along the Penola Strait (sub-parallel to the AP coastline) and four intersecting faults. These fault systems may be associated with different stages of continental margin evolution along the Antarctic Peninsula.

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The Petrology of Gabbroids of the Anagram Islands (Wilhelm Archipelago, West Antarctica)

Mytrokhyn¹,

Бахмутов²,

Aleksieienko³

et al. 2020

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The Anagram Islands are located near the Graham Coast of West Antarctica not far from the Ukrainian Antarctic Station "Akademik Vernadsky". Gabbroids that are probably Cretaceous in age predominate in the geological structure of the Anagram Islands. New data on the mode of occurrence of the Anagram gabbroids and their layering were obtained during the seasonal field works of the Ukrainian Antarctic Expeditions in 2017, 2019-2020 years. Samples of the gabbroids were examined by optical microscopy, electron microscopy and microprobe analysis as well as by measuring of anisotropy of magnetic susceptibility of rocks. The goal of the research was to clarify the geological position and petrographic features of the Anagram gabbroids, to determine the typomorphic features of rock-forming minerals, and to clarify the origin of the layering in gabbroids. It was determined that the bottom part of a large layered gabbroid intrusion is fragmentarily exposed on the Anagram Islands. The continuation of the intrusion is expected in the northeastern and southeastern directions. It was established that primary magmatic textures and mineral composition are preserved in the gabbroids despite the development of metamorphic amphibolization. The gabbroids show typical cumulative textures of magmatic origin. The main cumulative phases are plagioclase (An70-95), clinopyroxene (Wo41-49En34-47), orthopyroxene (Wo2-4En49-71), olivine (Fo67-69), Ti-magnetite and ilmenite. It is proved that the fine rhythmic-gradational layering in the gabbroids was formed by gravitational precipitation of the cumulative minerals on the bottom of the magma chamber and their further sorting by specific gravity due to convection currents. Cryptic layering is firstly discovered in the Anagram gabbroids and is explained by the processes of crystallization differentiation. The latter caused the accumulation of the most calcium plagioclases and the most magnesian mafic minerals in the layered gabbroids forming the bottom part of the intrusion. The present subvertical position of layering is explained by tectonic deformation that resulted in the tilting of the investigated section of the Anagram gabbroid intrusion. This confirmed by the studying of magnetic texture of the gabbroids (by the anisotropy of magnetic susceptibility data).

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Magma layering of gabbroids of Antarctic Peninsula batholith

Cited by 4 publications

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Petrology of Gabbroids of Girard Bay (Kyiv Peninsula, Graham Coast of the West Antarctica)

Petrology of Gabbroids of Girard Bay (Kyiv Peninsula, Graham Coast of the West Antarctica)

Magnetic field map of the Wilhelm Archipelago shelf zone, West Antarctica

The Petrology of Gabbroids of the Anagram Islands (Wilhelm Archipelago, West Antarctica)

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