Partial Assimilation Research Articles

Tracking Agulhas Leakage in the South Atlantic Using Modern Planktic Foraminifera Nitrogen Isotopes

AbstractSeawater transported into the South Atlantic from the Indian Ocean via “Agulhas leakage” modulates global ocean circulation and has been linked to glacial‐interglacial climate cycles. However, constraining past Agulhas leakage has been a challenge. We sampled a transect of the Cape Basin in winter 2017 that intersected a mature Agulhas eddy and found that the 15N/14N ratio (δ15N) of mixed‐layer nitrate, zooplankton, and foraminifera (tissue and shells) was 2‰–3‰ lower in the eddy than in the background Atlantic even though the δ15N of the underlying thermocline nitrate was indistinguishable between the two settings. We suggest that the δ15N of foraminifera and other zooplankton in the eddy reflects the original Agulhas Current thermocline nitrate, which is ∼2‰ lower than that of the South Atlantic due to N2 fixation that occurs in the Indian Ocean. Foraminifera δ15N may have been lowered further during eddy migration by in situ N2 fixation and/or recycling of low‐δ15N ammonium. The absence of low‐δ15N Agulhas nitrate in the eddy thermocline can be explained by partial assimilation of the nitrate as it was mixed into the euphotic zone during and after eddy formation, raising its δ15N. The low δ15N of eddy foraminifera, apparent even after several months of eddy migration across the Cape Basin, suggests that fossil foraminifer‐bound δ15N from the region could record variations in past Agulhas leakage.

Tracing the Origin and Magmatic Evolution of the Rejuvenated Volcanism in Santa Clara Island, Juan Fernández Ridge, SE Pacific

Oceanic intraplate volcanoes sometimes experience late-stage eruptive activity known as rejuvenated volcanism, and contrasting interpretations for its petrogenesis depend on the compositional characteristics. In the Juan Fernández Ridge (JFR), a volcanic chain approximately 800 km in length emplaced on the Nazca Plate, some subaerial occurrences of rejuvenated volcanism have been recognized on the Robinson Crusoe and Santa Clara Islands, both part of the same deeply eroded shield volcano complex. This study aims to understand the origin and magmatic evolution of rejuvenated volcanism on Santa Clara Island, emplaced after ~2.15 Ma of quiescence above the shield sequence, mainly via the analysis of unpublished geochemical and isotopic data. Field reconnaissance identified two nearly coeval rejuvenated sequences on Santa Clara Island: Bahía W (BW) and Morro Spartan (MS), both formed by basanitic and picro-basaltic lava flows with brecciated levels and local intercalations of sedimentary and pyroclastic deposits. In comparison to the chemical signature of the preceding shield-building stage (comprised mainly of basalts and picrites), the two rejuvenated sequences exhibit a notable enrichment in incompatible elements, but the Sr, Nd, and Pb isotopes are very similar to the FOZO mantle endmember, with an apparent additional contribution of HIMU and EM1 components. The geochemistry of lavas revealed the involvement of various processes, including contamination by ultramafic xenoliths, high-pressure fractional crystallization of olivine and clinopyroxene, and potential partial assimilation of oceanic lithospheric components. While the oceanic lithosphere has been considered as a potential source, the isotopic data from Santa Clara lies outside of the mixing curve between depleted mantle (DM, here represented by the North Chile Rise and the East Pacific Rise) and the previous shield stage, suggesting that a lithospheric mantle is not the primary source for the rejuvenated stage volcanism. Therefore, we favor an origin of the rejuvenated volcanism from the mantle plume forming the JFR, supported by similarities in isotopic signatures with the shield stage and high values of 208Pb/204Pb (only comparable to San Félix—San Ambrosio in the vicinity of JFR), implying the presence of a regional source with radiogenic 208Pb/204Pb isotope ratios. In addition, isotopic variations are subparallel to the mixing line between HIMU and EM1 components, whose participation in different proportions might explain the observed trends. In conclusion, we propose that the source of the rejuvenated volcanism on Santa Clara Island is a heterogeneous mantle plume, the same one that fed the shield stage. The rejuvenated volcanism is derived from a secondary melting zone away from the main axis of the plume.

Relevance of the Foramen of Vesalius for Preoperative Tumor Embolization in Skull Base Meningioma

ObjectiveTo investigate the role of the foramen of Vesalius (FV) in the pathogenesis of skull base meningioma by analyzing data from various multi-image modalities. MethodsFor this single-center retrospective study, 39 consecutive patients with skull base meningioma who underwent tumor resection between January 2020 and March 2023 were enrolled. The anatomical and pathological characteristics of the FV were evaluated using computed tomography (CT) and three-dimensional (3D)-digital subtraction angiography (DSA). The clinical significance of the FV in tumor hemodynamics and treatment, such as preoperative tumor embolization, was investigated using the 3D-DSA/CT fusion images. ResultsWe identified FV in 52% (17/27) of the finally included patients. In 10 (30%) patients, the FV was found bilaterally with no significant variation in appearance between the healthy and tumor-affected sides (p=0.786). The mean FV diameter was significantly larger on the tumor-affected side (p=0.010). No significant anatomical differences, like duplication and partial assimilation with the foramen ovale, were observed between the two sides. The FV was involved in venous skull base perfusion around the tumor in nine cases. In four cases where it was the pathway for tumor feeders, preoperative tumor embolization via the FV resulted in disappearance of the tumor stain. No complications associated with endovascular treatment were observed. ConclusionsThis study elucidated the anatomical asymmetry of the FV and its role in the hemodynamics of skull base meningioma. Our findings highlight the significance of performing anatomical and pathological evaluations of the FV in determining treatment strategies, including preoperative embolization, for skull base lesions.

Destabilizing segregation in friendship networks with farsighted agents

We consider a model of friendship network formation based on de Marti and Zenou (2017) where individuals belong to two different communities and costs of forming links depend on community memberships. Once there are myopic and farsighted individuals in both communities, many inefficient friendship networks such as segregation, partial integration or partial assimilation become destabilized. In the case of low intra-community costs, either (for high inter-community costs) the network where the smaller community ends up being assimilated into the dominant community or (for low inter-community costs) the network where both communities are fully integrated is both stable and strongly efficient. In the case of intermediate intra-community costs, star networks with a myopic individual in the center are both stable and strongly efficient.

McCarthyism and American Cold War Ideology in Irish-American Autobiographical Writing

This article explores the various ways in which the protagonist of Frank McCourt’s autobiographical account ’Tis, A Memoir confronts the McCarthyite proceedings and their unsettling consequences at times of utmost conservatism in America. It addresses his negotiation of an ultimately alienated ethnic identity, arguing that the protagonist’s fractured self not only reflects the slippery ground upon which McCarthyite practices are founded, but is also brought about by it. Beyond this analysis, however, the article is set to problematize the very status of McCourt’s autobiographical writing by assessing the memoir’s narrative codes in association with its content and purported readership. Specifically, the proposal evaluates the fictional strategies on which it is constructed, as well as the inconsistencies inherent in the narrative depiction of the character’s partial assimilation into an eventual Irish-American national identity. The proposal ultimately assays McCourt’s memoir as a product and reworking of the ideological tenets characteristic of McCarthyism and the early Cold War period.

A newly defined latest Carboniferous-Permian ridge subduction in the southern Altaids: Insights from adakitic, S-type, and I-type granitoids in the northern East Junggar (NW China)

ABSTRACT Late Palaeozoic evolution of the Chinese Altai-East Junggar orogenic collage is vital for a better understanding of the accretionary evolution in the southern Altaids. This paper reports new geochronological, geochemical, and isotopic data for the magmatic rocks collected from the northern part of the Dulate arc. The ~304.6 Ma tonalite samples present typical adakitic features of high Sr (396–714 ppm), low Y (1.42–2.60 ppm), Yb (0.11–0.24 ppm), and high Sr/Y (177.25–440.23) ratios. Combining high Mg# (55.35–57.21) and depleted isotopic composition (εHf(t): +9.89 to +13.37 and εNd(t): +5.36 to +6.06), we suggest that they were derived from the partial melting of a subducted oceanic slab. The ~299.4 Ma monzogranite samples have high A/CNK values (1.08 to 1.25), CIPW normative corundum contents (1.28–3.25 wt.%), and positive εHf(t) (+5.14 to +8.63) and εNd(t) (+1.08) values, which are similar to S-type granite that may be generated by the melting of greywackes. The monzogranite (~286.9 Ma) and rhyolitic porphyry (~283.9 Ma) are high-K calc-alkaline and similar to the highly fractionated I-type granites with depleted isotopic features (εHf(t): +11.68 to +14.99 and +0.75 to +7.18, εNd(t): +5.91 and +6.18). The monzogranite and rhyolitic porphyry could have been derived from a depleted mantle source, but the rhyolitic porphyry probably suffered partial assimilation of the overlying crust materials. Combining regional rock associations of mafic-ultramafic complexes, adakitic rocks, high-Mg diorites, and A-type granites with close spatial-temporal relationship, we conclude that a mid-oceanic ridge of the Ob-Zaisan Ocean subducted southward beneath the Dulate arc during the latest Carboniferous to Permian. With the opening of the slab window, the upwelling asthenosphere provided high heat flux and triggered various magmatism in the upper plate. We propose that ridge subduction is one of the most effective mechanisms of continental growth in the southern Altaids.

Isotopic differences and paleoenvironmental significance of nitrogen contained in bulk sedimentary rocks, decarbonated aliquots and kerogen extracts

The stable nitrogen isotopic composition (δ15N) of sedimentary rocks is an important tool for reconstructing the paleo-oceanic nitrogen cycle and has been widely used in palaeoenvironmental studies of the Precambrian and Phanerozoic. Currently, the commonly used parameters are the isotopic compositions of decarbonated samples (δ15NDCN) and kerogen extracts (δ15Nkerogen). However, some studies have shown that there are differences between these two proxies. In addition, differences were found between δ15NDCN and the nitrogen isotopic compositions of untreated samples (δ15Nbulk). In order to explain these phenomena, we selected sedimentary rock samples from different time periods in the Phanerozoic and analyzed nitrogen isotopes after all three treatments (bulk rock, decarbonated rock, and kerogen extracts). We find that (1) δ15Nbulk is greater than δ15NDCN in most samples by 0.6‰ on average, indicating that acid-soluble organic N with higher δ15N values was lost preferentially during decarbonization; (2) δ15NDCN is greater than δ15Nkerogen mainly in anoxic environments, which may be linked to ammonium accumulation in pore fluids or in the water column during deposition and/or diagenesis. For example, the anaerobic ammonia oxidation process and partial assimilation preferentially consume 14NH4+ and enrich 15NH4+ in seawater. Therefore, NH4+ fixed by clay minerals may have a higher δ15N than organic nitrogen; (3) δ15Nkerogen greater than δ15NDCN was observed in a subset of samples and may reflect either preferential release of 14NH4+ from organic matter or biological production of isotopically light NH4+, followed by adsorption to clay minerals. In this case, the δ15N of residual organic nitrogen would be relatively high compared to the released NH4+. However, this scenario is only retained in samples that have not undergone significant post-depositional alteration, which tends to lower δ15Nkerogen and increase δ15NDCN. Differences between the three nitrogen parameters are in many cases small and would not alter overall paleoenvironmental interpretations; however, in some cases, they can be significant and carry additional information about diagenetic conditions that may be unlocked with additional studies on wider range of deposition environments.

Listeners experienced with backness harmony compensate for coarticulation in F2

A natural consequence of articulation is the partial assimilation of neighboring vowels in vowel-to-vowel coarticulation (e.g., relative fronting of /ɑ/ in [ɑiCi]). Previous research suggests that listeners are sensitive to coarticulatory variation and perceptually compensate for coarticulation, although the degree of compensation is impacted by how extensive coarticulation is in a language (e.g., English and Shona: Beddor et al., 2002). This study partially replicates Beddor et al. with Turkish listeners (N = 20), who presumably have limited experience with coarticulation in F2 due to pervasive backness harmony in Turkish, on their perception of the Turkish front-back vowel pair /ɛ ɑ/. Participants completed a 4IAX discrimination task with coarticulated /ɛ ɑ/ vowels spliced into appropriate and inappropriate coarticulatory contexts, and vowel identification tasks on an /ɛ-ɑ/ continuum in [bɑb] and [bib] contexts as well as in “no context.” Results suggest that Turkish listeners compensate for coarticulation, supporting the idea that compensation for coarticulation is automatic: Appropriate coarticulation impaired vowel discrimination, and there were boundary shifts in vowel identification across all contexts with significantly different front vowel response proportions (back>no context>front). Moreover, vowels presented with no adjacent coarticulation trigger were perceived more categorically, suggesting that coarticulatory contexts induce more continuous vowel perception.

A Phonological Study of Mosuli Dialect Assimilation

Assimilation is a phonological process which refers to the change of one sound by another sound under the influence of a third sound. The main reason behind this change is the speaker's tendency to economize the muscular effort or make ease of articulation or both. This study aims at finding out the assimilation patterns in Mosuli dialect( ) and divide these patterns in this dialect( ) according to the following factors:
 
 Degree of influence.
 
 2. The direction of influence (i.e., voicing, place of articulation, manner of articulation and Tafxim). The results show that Mosuli dialect tends to ease of articulation than that of economize the muscular effort, also they show that the Mosuli dialect uses only regressive assimilation depending on the factor of direction of influence, also the study shows the use of complete and partial assimilation depending on the degree of influence.

Discursive practices of the performative theory of solidarity discourse

This exploratory study examined the discursive practices of solidarity discourse, contributing to the performative theory of solidarity discourse. Five discursive practices were identified. It was noted that plurality and assimilation practice, complete assimilation, and partial assimilation were the most frequently employed practices. Assimilation is accomplished using three strategies: inclusive first plural pronouns, collective nouns, and spatialization. The second discursive practice was appraisal. There are three strategies that are utilized by speakers: to appraise and praise the ‘self’ or one's support, to appraise or bash and attack the ‘other,’ and to appraise and praise the ‘us/we.’ The third practice is representation and positioning, which is realized by intertwined representations of the ‘us,’ the common enemy/challenge representation, and self-positioning/representation. Endorsement is the fourth discursive practice to achieve solidarity through which the speaker endorses policies or ideologies to show solidarity. Finally, storytelling is a practice employed to build solidarity, manage knowledge, achieve performative acts, and shape the future through past events. The current paper contributed to our understanding of solidarity and expanded our perspective on discourse in general, and solidarity discourse in particular. In addition, the application of this study can bridge the gap between the ‘self’ and the ‘other’ by addressing the ‘us/we.’

Linguocognitive and sociocultural aspects of bilingualism

The concepts and data accumulated to date on bilingualism are summarized and generalized in the article. Bilingualism is the presence of two or more languages in a person’s actual life and operating them whenever necessary, regardless of the level of proficiency and medium of language acquisition (natural or artificial). In the cognitive- psycholinguistic perspective, the study of a foreign/second language is primarily about the goals of language training: with a distinct lag from a first language (top-down training) to gain conceptual knowledge of one’s own and foreign cultures and read cognitively complex works in two languages VS together with a first language from early childhood (bottom-up training) to gain the skills of authentic usage of both languages and be fluent in everyday communication. In in the socio-cultural perspective, in multinational states bilingualism is an objective necessity, provided that it is endoglossic. This is an alternative to the full or partial assimilation of linguistic minorities to the language and culture of the majority. The ideal is not linguocultural assimilation, but mutual integration, the formation of a single nation. As for an external foreign language learnt for international communication, it should be mastered less zealously and generally perceived as a mere substitute for an “international auxiliary language” - a simple code, universal and flexible, to convey a person’s individual and national meanings. Acculturation in the spirit of a foreign culture is excluded, it is optimal to focus on the heritage of the internal, national and indigenous, cultures and literatures and learn them in both national/ethnic languages and a foreign language.

Peculiarities of the Borrowed Electric Vehicle Terms Adaptation in Modern French Language

The object of the study is the borrowed terms in the modern French scientific and technical literature on electric vehicles. The subject of the study is the etymological, functional, morphological, phonetic and semantic characteristics of terms and their influence on the process of their francization. The purpose of the study is to determine the features of the assimilation process and the types of assimilation of the electric vehicle terms borrowed into the French language. Evaluation of the process may be important for understanding the formation of new French terms systems. Special attention is paid to the characteristics of the terms of the electric vehicles, the factors influencing the development of the terms system, the methods of assimilation. The study concludes that the process of assimilation of borrowed terms of electric vehicle in the French language proceeds under the influence of linguistic and extralinguistic factors. The classifications of borrowed vocabulary are compared to group borrowings according to the degree of assimilation. The borrowed terms with partial assimilation in French change their phonetic and graphic forms, participate in word formation with prefixes and suffixes, may lose their original meaning, and acquire a specific one. Fully assimilated terms are indistinguishable from the native vocabulary, whereas for non-assimilated borrowings, comments or synonyms are required. The study of the assimilation process can be continued by a more detailed study of certain types of assimilation (graphic, phonetic, semantic, etc.) of borrowed terms in the new terms systems in French using the created classifications.

A potential linkage between excess silicate-bound nitrogen and N2-rich natural gas in sedimentary reservoirs

Molecular nitrogen (N2) released from sedimentary rocks during metamorphism is an important component of the biogeochemical nitrogen cycles. However, the importance and variability of this metamorphic N2 flux from rock nitrogen to Earth's surface environment remains largely unexplored. Here we present a comprehensive bulk rock C-N and N2 concentration dataset from the lower Cambrian shale across the Yangtze Block. The results reveal a spatial trend of excess silicate-bound nitrogen in the lower Cambrian shale throughout the Yangtze Block, which is interpreted as partial assimilation of ammonium (NH4+) with high concentrations of NH4+ accumulating in the euxinic water column and in sediment pore waters at shelf and slope environments during sedimentation. The remarkable spatial coupling between silicate-bound nitrogen in bulk rock shale and N2 concentration in modern shale reservoirs indicates that the high proportion of silicate-bound nitrogen may act as an important control on the formation of N2-rich gas in shale reservoirs during metamorphism. These N2-rich reservoir rocks may have affected the surface environment through tectonic movement over Earth's history. Our results therefore identify a novel linkage in the nitrogen cycle and provide evidence for the importance of metamorphism on the return of rock nitrogen back to the surface environment. We further reveal that the metamorphic N2 gas flux from the geosphere to the atmosphere is dependent on environmental conditions during sediment deposition.

ASSIMILATION OF BORROWINGS IN THE LANGUAGE-RECIPIENT

In the Russian language of the XVIIth and XVIIIth centuries, the significant part of foreign words were German lexical borrowings. According to the degree of development of the language loanwords recipient traditionally distinguish two main groups of words - assimilated and unassimilated. One of the main bits of foreign words, allocated according to the degree of assimilation, are actually borrowing assimilated words about the skill that scientists have no disagreements. The only problem in this sense is to hold the line between borrowing and internationalism. Internationalism represented, first of all, in the terminological lexicon. By the terms-internationalism: a) socio-political lexicon: congress, constitution, minister, meeting, party, politics, revolution, republic, resolution, senate, etc.; b) scientific terminology: biology, geography, geodesy, geology, zoology, history, linguistics, mathematics, physics, etc.; c) the technical name: unit, antenna, apparatus, harvester, monoplane, tank, tractor; d) art criticism lexicon: aria, ballet, drama, genre, novella, opera, poetry, tenor, etc. When classifying loanwords must be considered the formal features (assimilation of words in the borrowing language) and functionality (use of words in the borrowing language). According to the degree of adaptation of lexical units in the system of the Russian language-recipient, both full and partial assimilation of the German-language vocabulary is possible. Partially assimilated vocabulary can be divided into the following groups: 1) German vocabulary assimilated at the graphic and grammatical levels; 2) German- language vocabulary assimilated at the grammatical level; 3) German-language vocabulary assimilated at the word-formation level; 4) German-language blotches with preceding and following Russian equivalents. The research is based on actual data obtained by different linguists, and on the results of the author's own observations.

ASSIMILATION OF BORROWINGS IN THE LANGUAGE-RECIPIENT

In the Russian language of the XVIIth and XVIIIth centuries, the significant part of foreign words were German lexical borrowings. According to the degree of development of the language loanwords recipient traditionally distinguish two main groups of words - assimilated and unassimilated. One of the main bits of foreign words, allocated according to the degree of assimilation, are actually borrowing assimilated words about the skill that scientists have no disagreements. The only problem in this sense is to hold the line between borrowing and internationalism. Internationalism represented, first of all, in the terminological lexicon. By the terms-internationalism: a) socio-political lexicon: congress, constitution, minister, meeting, party, politics, revolution, republic, resolution, senate, etc.; b) scientific terminology: biology, geography, geodesy, geology, zoology, history, linguistics, mathematics, physics, etc.; c) the technical name: unit, antenna, apparatus, harvester, monoplane, tank, tractor; d) art criticism lexicon: aria, ballet, drama, genre, novella, opera, poetry, tenor, etc. When classifying loanwords must be considered the formal features (assimilation of words in the borrowing language) and functionality (use of words in the borrowing language). According to the degree of adaptation of lexical units in the system of the Russian language-recipient, both full and partial assimilation of the German-language vocabulary is possible. Partially assimilated vocabulary can be divided into the following groups: 1) German vocabulary assimilated at the graphic and grammatical levels; 2) German- language vocabulary assimilated at the grammatical level; 3) German-language vocabulary assimilated at the word-formation level; 4) German-language blotches with preceding and following Russian equivalents. The research is based on actual data obtained by different linguists, and on the results of the author's own observations.

NEW TYPES OF BASIC ROCKS IN THE KORSUN-NOVOMYRHOROD ANORTHOSITE-RAPAKIVI GRANITE PLUTON AS AN INDICATOR OF ITS PETROGENESIS

Two species types of basic rocks contrasting in chemical and mineral composition were investigated within the Korsun-Novomyrhorod anorthosite-rapakivigranite pluton (KNP) of the Proterozoic age. In comparison to more typical basic rocks of KNP, the investigated rocks are presented by the extremely Fe-rich fayalite gabbroids and the most MgO enriched biotite gabbronorite. The first of them occupy a deeper level of the Horodishche massif in the central part of KNP. According to a high-Fe association of minerals and reduced or low An content in plagioclase they may represent the crystallization of a highly evolved basic melt (after anorthosite and gabbronorites separation), which were crystallized under abyssal conditions and low oxygen fugacity. Preliminary geochemical data indicate that trace elements concentration and negligible negative Eu-anomalies (0.72-0.95) are similar to most distributed basic rocks but unlike the last it is slightly differed by decreasing La/Yb and enriched in Sc (up to 118 ppm). Thus, we suppose those rocks might be crystallized as a result of mixing highly differentiated (iron and alkali enriched) melt with the early generation of anorthitic plagioclase, with subsequent dissolution of the last. Enrichment in iron of the mafic minerals and increasing of alkalinity of plagioclase in the basic rocks is consistent with the appearance of ferrodioritic melts as a product of prolonged crystalline differentiation of the initial melt. In contrast to fayalitic gabbroids, the pyroxene-biotite gabbronorites from the border zone in according to increased Mg# of the mafic minerals and rocks are obviously the least differentiated varieties of the anorthosite-gabbronorite series. The regularities in chemical composition in such type of rocks are consistent with the liquid line of dissent for basic rocks in KNP, which implies their crystallization at an earlier stage of magma ascending. By composition, such melt can be formed at an intermediate stage from slightly differentiated melt. This is indicated by enrichment in Sr (453-881 ppm) and Ba (910-930 ppm), Eu/Eu* (0.85-1.10), increased content MgO (up to 8 wt. %), Cr and V (59-193 and 169-350 ppm respectively). At the same time these rocks are enriched in Zr and Hf (378-478 and 10.3-12.02 ppm respectively), highly enriched in Rb (169-192 ppm), with moderate Nb and Ta content (14.6-18.1 and 0.91-2.84 ppm respectively) that point out to interaction and partial assimilation by crust material. Summarizing geological data of the deep drill-holes, it is possible to reveal a general direction of the mafic minerals evolution in the basic rocks and the evidences of cryptic layering. The last are quite clearly manifested both in the large gabbro-anorthosite massifs and individual intrusive bodies. We suppose that the evolution trend of mafic mineral composition are consistent with the tholeiitic trend differentiation of the primary melt with gradual increasing of iron content (under low oxygen fugacity) during differentiation and ascending in the upper crust. According to this interpretation of the inner structure of gabbro-anorthositic massifs, on the modern erosional level of KNP are often exposed the fragments of the upper (or lateral) layered series (Fe-enriched), less often the drill-holes reach up to the heads of the lower layered series.

Serial interaction of primitive magmas with felsic and mafic crust recorded by gabbroic dikes from the Antarctic extension of the Karoo large igneous province

Two subvertical gabbroic dikes with widths of ~ 350 m (East-Muren) and ≥ 500 m (West-Muren) crosscut continental flood basalts in the Antarctic extension of the ~ 180 Ma Karoo large igneous province (LIP) in Vestfjella, western Dronning Maud Land. The dikes exhibit unusual geochemical profiles; most significantly, initial (at 180 Ma) εNd values increase from the dike interiors towards the hornfelsed wallrock basalts (from − 15.3 to − 7.8 in East-Muren and more gradually from − 9.0 to − 5.5 in West-Muren). In this study, we utilize models of partial melting and energy-constrained assimilation‒fractional crystallization in deciphering the magmatic evolution of the dikes and their contact aureoles. The modeling indicates that both gabbroic dikes acquired the distinctly negative εNd values recorded by their central parts by varying degrees of assimilation of Archean crust at depth. This first phase of deep contamination was followed by a second event at or close to the emplacement level and is related to the interaction of the magmas with the wallrock basalts. These basalts belong to a distinct Karoo LIP magma type having initial εNd from − 2.1 to + 2.5, which provides a stark contrast to the εNd composition of the dike parental magmas (− 15.3 for East-Muren, − 9.0 for West-Muren) previously contaminated by Archean crust. For East-Muren, the distal hornfelses represent partially melted wallrock basalts and the proximal contact zones represent hybrids of such residues with differentiated melts from the intrusion; the magmas that were contaminated by the partial melts of the wallrock basalts were likely transported away from the currently exposed parts of the conduit before the magma–wallrock contact was sealed and further assimilation prevented. In contrast, for West-Muren, the assimilation of the wallrock basalt partial melts is recorded by the gradually increasing εNd of the presently exposed gabbroic rocks towards the roof contact with the basalts. Our study shows that primitive LIP magmas release enough sensible and latent heat to partially melt and potentially assimilate wallrocks in multiple stages. This type of multi-stage assimilation is difficult to detect in general, especially if the associated wallrocks show broad compositional similarity with the intruding magmas. Notably, trace element and isotopic heterogeneity in LIP magmas can be homogenized by such processes (basaltic cannibalism). If similar processes work at larger scales, they may affect the geochemical evolution of the crust and influence the generation of, for example, massif-type anorthosites and “ghost plagioclase” geochemical signature.

An Autosegmental Account of Melodic Processes in Jordanian Rural Arabic

This study aims at providing an autosegmental account of feature spread in assimilatory situations in Jordanian rural Arabic. I hypothesise that in any assimilatory situation in Jordanian rural Arabic the undergoer assimilates a whole or a portion of the matrix of the trigger. I also hypothesise that assimilation in Jordanian rural Arabic is motivated by violation of the obligatory contour principle on a specific tier or by spread of a feature from a trigger to a compatible undergoer. Data of the study were analysed in the framework of autosegmental phonology with focus on the notion of dominance in assimilation. Findings of the study have revealed that an undergoer assimilates a whole of the matrix of a trigger in the assimilation of /t/ of the detransitivizing prefix /Ɂɪt-/, coronal sonorant assimilation, and inter-dentalization of dentals. However, partial assimilation occurs in the processes of nasal place assimilation, anticipatory labialization, and palatalization of plosives. Findings have revealed that assimilation occurs when the obligatory contour principle is violated on the place tier. Violation is then resolved by deletion of the place node in the leftmost matrix and by right-to-left spread of a feature from rightmost matrix to leftmost matrix. It has been also revealed that spread of a primary or a non-primary feature from a trigger to an undergoer can motivate assimilation to occur in some assimilatory situations in Jordanian rural Arabic.

Contribution to the understanding of the Pinheiro Machado Complex (Dom Feliciano Belt, Brazil): A study of textures, mineral chemistry, and crystallization conditions

This article presents textures, mineral chemistry, and geothermobarometric data for the southeastern Pinheiro Machado Complex rocks (PMC), eastern domain of the Dom Feliciano Belt, Rio Grande do Sul, Brazil. The PMC is composed by comagmatic intrusions of quartz diorite, tonalite, and granodiorite with medium‐ to fine‐grained equigranular and medium‐grained inequigranular textures with subordinate alkali‐feldspar macrocrystals. Partial melting features are observed in the comagmatic as melt pools and melt films. Amphibolite xenoliths also occur, presenting sharp‐angled to rounded contacts with the intrusions and evidences of partial assimilation, marked by mafic schlierens. Electron probe microanalyzer punctual analyses were used to classify amphibole, plagioclase, biotite, epidote, and titanite, as well as for the calculations of the crystallization P–T conditions. Amphiboles consist of pargasite for the comagmatic intrusions, and Mg‐hornblende for the amphibolite. Plagioclase ranges from oligoclase to andesine (An15‐40) in both units. Biotite corresponds to annite, with Fe/(Fe + Mg) > 0.3. The epidote has mostly magmatic characteristics in the comagmatic intrusions, with pistacite content 25–30%. Titanite has two distinct textures, titanite I is well formed, subhedral to euhedral, with up to 3 mm; while titanite II is anhedral with size >1 mm and rounded shapes, being both chemically homogeneous. The estimated P–T conditions for the amphibolite crystallization, using plagioclase‐hornblende geothermometer are 650–850°C and 3.62–4.95 kbar, whereas the conditions from the comagmatic intrusions are 714–871°C and 4.44–6.10 kbar. In the mineral phases there is a prevalence in the recrystallization field between subgrain rotation (SGR) and grain boundary migration (GBM) in submagmatic flow. These new data indicate that possibly at the end of PMC crystallization, late magmatic fluids caused re‐equilibrium of mineral phases, mainly in biotite and feldspars. Finally, we suggest that the PMC is the result of continuous and repeated comagmatic intrusions in a continental magmatic arc setting at a depth of 20–30 km in an amphibolitic continental crust.

Magma Reservoir Formation and Evolution at a Slow-Spreading Center (Atlantis Bank, Southwest Indian Ridge)

Several ODP-IODP expeditions drilled oceanic core complexes (OCCs) interpreted as exhumed portions of lower crust close to the ridge axis, and provide the community with invaluable sampling opportunity for further constraining magmatic processes involved in the formation of the slow-spreading lower oceanic crust. ODP Hole 735B presents the most primitive lithologies sampled at Atlantis Bank OCC (Southwest Indian Ridge) in a ~250 m thick section that was previously interpreted as a single crustal intrusion. We combined detailed structural and petrographic constraints with whole rock and in situ mineral analyses of this section in order to precisely determine the processes of emplacement, crystallization and melt migration within the lower crust. The lower half of the unit is comprised of alternating olivine gabbros and troctolites showing intrusive contacts, magmatic fabrics and crystal-plastic fabrics. Such structures and primitive lithologies are lacking in the upper half, rather uniform, gabbroic sequence. Whole rock compositions highlight the cumulative character of both lower and upper units and a great compositional variability in the lower sequence, whereas the upper sequence is homogeneous and differentiates up-section. In situ analyses of mineral phases document magma emplacement processes and provide evidence for ubiquitous reactive porous flow during differentiation. We show that the whole section, and related geochemical unit, constitutes a single magmatic reservoir, in which the lower unit is formed by stacked primitive sills formed by repeated recharge by primitive melts and melt-present deformation. Recharge led to partial assimilation of the crystallizing primitive cumulates, and hybridization with their interstitial melts. Hybrid melts were progressively collected in the overlying mushy part of the reservoir (upper unit), whereas the sills' residual hybrid melts differentiated by reactive porous flow processes under a predominantly crystallization regime. Similarly, hybrid melts’ evolution in the upper unit was governed by upward reactive porous flow, and progressive differentiation and accumulation of evolved melts at the top of the reservoir. Our results provide the community with the first integrated model for magma reservoir formation in the lower slow-spreading oceanic crust that can potentially be applied to other magmatic lower crust sections.