Subordinate Populations Research Articles

Provenance of Detrital Rutiles from the Triassic–Jurassic Sandstones in Franz Josef Land (Barents Sea Region, Russian High Arctic): U-Pb Ages and Trace Element Geochemistry

Provenance study plays an important role in paleogeographic and tectonic reconstructions. Detrital zircons are commonly used to identify sediment provenance; however, a wide range of detrital zircon ages in clastic rock often represent a fingerprint of reworked older terrigenous successions rather than ages of magmatism and metamorphism in the provenance area. This study focuses on the provenance of detrital rutile grains in the Triassic–Jurassic sandstones from Franz Josef Land and shows the importance of multiproxy approaches for provenance studies. Trace element data demonstrate that most rutile grains were sourced from metapelitic rocks, with a subordinate population having a metamafic origin. The Zr-in-rutile thermometer and U-Pb geochronology suggest that detrital rutile grains were predominantly derived from rocks that underwent amphibolite facies metamorphism during the Paleozoic era, with a predominance of the Carboniferous–Permian ages. Therefore, we suggest that the provenance area for the studied sandstones on Franz Josef Land has a similar geological history to the Taimyr region and Severnaya Zemlya archipelago. We propose that this crustal domain extends across the Kara Sea and forms the basement to the north and east of FJL, representing a proximal provenance for the studied Mesozoic terrigenous rocks. This domain experienced both Middle–Late Ordovician and Carboniferous–Permian metamorphism. The comparison of U-Pb dating and the geochemistry of rutile, U-Th/He, and U-Pb dating of zircons showed that detrital rutiles are the powerful toll in provenance restoration and can give additional constrains when a provenance area locates within collisional-convergent settings.

Trans* Joy as Resistance

Abstract Theorist Lauren Berlant defines inconvenience as an affect, one exerted by dominant forces onto subordinate populations. In the same way subordinate populations exert inconvenient affects as well, creating a dynamic of dominant and subordinate inconvenience through which social power relationships may be understood. Following this structure, this article charts the dominant and subordinate affects exerted by capitalism and trans* bodies, respectively, and how capitalist oppression responds to and shapes trans* embodiment. Through an autotheoretical lens, this relationship is here examined in the 2020 film Possessor and the 2015 film Tangerine, highlighting the points of interaction between trans*ness and capitalism's state structures of domination and oppression. Ultimately, I point to trans* joy as an affect that presents a danger to capitalism's domination, providing space for trans* persons to thrive.

A coevolutionary constrained multi-objective algorithm with a learning constraint boundary

When solving constrained multi-objective optimization problems, the balance of convergence, diversity, and feasibility plays a pivotal role. To address this issue, this paper proposes a coevolutionary constrained multi-objective algorithm with learning constraint boundary (CCMOLCB). Firstly, the constrained multi-objective problems are transformed by adding an additional objective using the constraint violation degree. Then, the transformed problem is solved by an improved coevolutionary framework which employs two populations. The main population explores the objective space and repairs infeasible solutions to maintain the feasibility of population. Meanwhile, the feasibility and diversity of solutions are balanced by using a dynamic weight coefficient during the evolution, it changes as the number of iterations increases. The subordinate population selects solutions by taking into consideration the learning constraint boundary (LCB). This boundary guarantees convergence of solutions by constraining the search range of the main population, thereby enhancing the environmental selection pressure. The performance of CCMOLCB is compared with seven state-of-the-art constrained multi-objective evolutionary algorithms on five test suites. The experimental results illustrate that CCMOLCB exhibits competitive performance when dealing with this family of problems.

Provenance and geotectonic setting of the Paleoproterozoic Cerro Figurita formation (Río de la Plata Craton, Uruguay)

The Cerro Figurita Formation (CFFm) represents a clastic sedimentation approximately 3000 m thick which underwent low greenschist metamorphic conditions. The sedimentary sequence is dominated by polymictic conglomerates and sandstones deposited in an environment of alluvial fans that evolve to marine turbidites. The geochemistry of the CFFm reveals derivation from sources with a mix composition similar to unrecycled Upper Continental Crust; alteration increases towards the top of the sequence (CIA 45–92). The contribution of mafic (probably ophiolitic) source rocks is revealed by petrography and low values of Th/Sc (0.3–1.5), Zr/Sc (6–20), Th/U (3–6) and high values of Cr/V (1.1–12.2); slightly negative Eu/Eu* anomalies (0.7–0.9) would indicate the presence of plagioclase in the source rocks. TDM ages are between 2001 and 2269 Ma, and the ƒSm/Nd values along with the relationship between εNd(t) andTh/Sc ratio indicate a provenance from an andesitic arc component. Detrital zircon age patterns are dominated by 2160, 2163 and 2177 Ma peaks, with the youngest zircon showing an age of 2112 ± 21 Ma, confirming a provenance from the Florida central granitic gneiss belt (FB). It is noteworthy the presence of subordinate populations of detrital zircon grains with ages of 2772, 2935 and 3222 Ma, indicating the presence of an inherited felsic source of Archean age, not yet detected in the Piedra Alta Terrane (PAT), and probably located within the Nico Pérez Terrane. A multi-approach to provenance analyses integrating geochemistry, petrography, U–Pb zircon ages, and Nd isotopes indicate ongoing active tectonism during the Orosirian in the PAT, whereas a retroarc foreland basin geotectonic setting is suggested for the CFFm deposition.

The cost of sympatry: spatio-temporal patterns in leopard dietary and physiological responses to tiger competition gradient in Rajaji Tiger Reserve, Uttarakhand, India.

Apex predators have critical roles in maintaining the structure of ecosystem functioning by controlling intraguild subordinate populations. Such dominant-subordinate interactions involve agonistic interactions including direct or indirect impacts on the subordinates. As these indirect effects are often mediated through physiological processes, it is important to quantify such responses to better understand population parameters. We used a large carnivore intraguild system involving tiger (Panthera tigris) and leopard (Panthera pardus) to understand the dietary and physiological responses under a spatio-temporal gradient of tiger competition pressures in Rajaji Tiger Reserve (RTR) between 2015 and 2020. We conducted systematic faecal sampling in the winters of 2015 and 2020 from the park to assess diet and physiological measures. Analyses of leopard-confirmed faeces suggest a dietary-niche separation as a consequence of tiger competition. In 2020, we found an increased occurrence of large-bodied prey species without tiger competition in western-RTR. Physiological measures followed the dietary responses where leopards with large-sized prey in the diet showed higher fT3M and lower fGCM measures in western-RTR. In contrast, eastern-RTR leopards showed lower levels of fT3M and fGCM in 2020, possibly due to intense competition from tigers. Overall, these patterns strongly indicate a physiological cost of sympatry where competition with dominant tigers resulted in elevated nutritional stress. We recommend expansion of leopard monitoring and population estimation efforts to buffers, developing appropriate plans for human-leopard conflict mitigation and intensive efforts to understand leopard population dynamics patterns to ensure their persistence during the ongoing Anthropocene.

Provenance and Stratigraphy of the Upper Carboniferous—Lower Permian Strata of October Revolution Island (Severnaya Zemlya Archipelago): Implications for Geological History of the Russian High Arctic

Small depressions across the north-eastern part of October Revolution Island (Severnaya Zemlya archipelago, Kara terrane) are filled with continental terrigenous rocks, dated as Upper Carboniferous–Lower Permian in age based on palynological data. These rocks overlie Ordovician volcaniclastic rocks above a prominent angular unconformity. U-Pb dating of detrital zircons from the Late Carboniferous–Lower Permian rocks reveals that most grains are Ordovician in age, ranging between 475–455 Ma. A subordinate population of Silurian detrital zircons is also present, contributing up to 15% of the dated population, while Precambrian grains mainly yield Neo-Mesoproterozoic ages and do not form prominent peaks. The combined U-Pb and (U-Th)/He ages indicate that most zircon (U-Th)/He ages were reset and average at ca. 317 Ma, suggesting ~6–7 km of Late Carboniferous uplift within the provenance area. This provenance area, mainly comprising Ordovician magmatic and volcanic rocks, was located close to the study area based on the coarse-grained nature of Late Carboniferous–Lower Permian rocks of north-eastern October Revolution Island. Therefore, we propose that Late Paleozoic tectonism significantly affected both the southern margin of the Kara terrane, as previously supposed, and also its north-eastern part. We propose that the Late Paleozoic Uralian suture zone continued to the north-eastern October Revolution Island and was responsible for the significant tectonic uplift of the studied region. This suture zone is now hidden beneath the younger Arctic basins.

The Funeral Rite of the Spartan Kings

This article is a historical commentary on Herodotus’ account of the funerals of the Spartan kings. It is an attempt on the author’s part to explain why for centuries the royal funerary ritual continued unchanged despite its being too lavish for ascetic Sparta. The study focuses on the socio-economic composition of the funeral attendees. In the author’s opinion, the participation of representatives of the lower classes – the helots and perioikoi – in the ceremony facilitated the evolvement of elites from both categories of the Spartan subordinate population. The funeral ceremony performed an important ideological and propaganda function serving as a unifying factor for all the social classes and indoctrinating the masses with the belief in the eternal and immutable nature of the royal authority and, by extension, of the Spartan state.

A missing piece between Laurentia and the North China Craton in Rodinia: Evidence from metasedimentary rocks of the North Qinling Terrane in central China

The North Qinling Terrane was a microcontinent in the Late Neoproterozoic and then subducted northwards beneath the North China Craton for regional metamorphism in the Early Paleozoic. In order to constrain its location in supercontinent Rodinia, metasedimentary rocks were sampled from it for a combined study of whole-rock major and trace elements as well as zircon U-Pb ages and Lu-Hf isotopes. The metasedimentary rocks show greywacke compositions with A/CNK ratios of 0.99–1.28 and upper continental crust-like trace element patterns. They have metamorphic ages of ca. 510–490 Ma, recording continental collision for the regional metamorphism. The youngest detrital zircon U-Pb ages from three metasedimentary rocks are 1161 ± 54 Ma, 954 ± 15 Ma, 861 ± 10 Ma, respectively. In combination with ages of granitic intrusions of 960 to 890 Ma in the target region, their deposition ages are constrained to be 1110–960 Ma, ca. 960 Ma and ca. 860 Ma, respectively. The cumulative proportions of the difference between the detrital zircon crystallization ages and the deposition ages for the sediments of ca. 960 Ma and ca. 860 Ma suggest their deposition in a collisional setting. Detrital zircon age spectrum from the Qinling Group yields two major populations at 1000–900 Ma and 1700–1400 Ma and three subordinate populations at 900–800 Ma, 1300–1200 Ma and 1800–1700 Ma with rare Neoarchean grains. Neoproterozoic detrital zircons mainly have negative εHf(t) values, consistent with Neoproterozoic granitoids in the North Qinling Terrane. On the other hand, Mesoproterozoic detrital zircons mainly have positive εHf(t) values, similar to those in East Laurentia and East Greenland. This means that the major provenance of sediments in the Qinling Group was the North Qinling Terrane itself and East Laurentia, supporting the connection between the North Qinling Terrane and East Laurentia in Rodinia prior to its breakup. In combination with the coeval strata in the southern margin of the North China Craton, we propose that the North Qinling Terrane is a missing piece connecting the southern margin of the North China Craton with the northern part of East Laurentia in Rodinia in the early Neoproterozoic.

Ethnographies of Global Policing

The last two decades have seen an unprecedented proliferation of ethnographies of policing in many parts of the world. Implicit in the body of this new work is the continuation of an old and perhaps irresolvable debate on what policing is: the extralegal subjugation of subordinate populations or an agency whose authority is highly restricted by the norms of civilian populations. I argue that the best way to tackle this debate is to further develop the incipient practices of global ethnography, that is, to understand local practices via their global histories.

Secret Cures of Slaves: People, Plants, and Medicine in the Eighteenth-Century Atlantic World

Secret Cures of Slaves: People, Plants, and Medicine in the Eighteenth-Century Atlantic World

Olivine phenocryst origins and mantle magma sources for monogenetic basalt volcanoes in northern New Zealand from textural, geochemical and δ18O isotope data

Olivine phenocrysts in basalts erupted in the Kaikohe-Bay of Islands volcanic field (KBIVF), a cluster of Quaternary monogenetic edifices in northern New Zealand, provide an opportunity to investigate magma source and assembly. The phenocryst population has both cognate and non-cognate origins with respect to the carrier magma. Common large subhedral-euhedral phenocrysts with compositions of Fo80–86 are autocrysts, having nucleated in a melt equivalent of the host whole-rock (~Mg#56–63). A subordinate population of large subhedral-euhedral phenocrysts that are Mg-rich (>Fo86) nucleated in a melt more mafic (>Mg#65). These are antecrystic and are likely to have a deep cumulate origin, perhaps the product of fractionation of a primitive parental magma. Smaller anhedral phenocrysts have compositions (~Fo70–75) that would have crystallised in a more evolved melt (~Mg#42–48). These are xenocrysts from stalled and fractionated crystal mush zones or intrusions in the mid and upper crust. Other small phenocrysts (Fo66–79) are euhedral and reversely zoned with mafic mantle zones (Fo80–85). They also nucleated in a more evolved crustal magma, but subsequently experienced magma-mixing with a more mafic magma. The olivine assemblage requires a vertically extensive magma system through the crust and upper mantle involving deep cognate crystallisation, and recycling of non-cognate crystals from deep and shallow intrusive bodies. This in accord with varied origins for the accompanying plagioclase and clinopyroxene populations in the rocks demonstrated in previous studies. This study presents the first δ18O analyses of olivines from monogenetic volcanoes in New Zealand. SIMS analysis of cognate and cumulate olivine phenocrysts in KBIVF basalts, and those from other volcanoes in northern New Zealand basaltic fields, show that they are non-zoned (δ18O ± 0.4‰). The inter-crystal range at most volcanoes is narrow (0.5‰), although the olivine population at a few volcanoes are more varied (range up to 1.25‰), requiring more than one source. The isotopic data for the more northern fields KBIVF (δ18O mean = 5.60‰; range = 5.12–6.20‰) and Whangarei volcanic field (δ18O mean = 5.50‰; range = 4.98–6.12‰) include values higher than that of olivine from MORB-HIMU sources, and overlap those associated with EMI/EMII sources or subduction zone magmas. Whole-rock trace element and Pb-isotope data from these fields have been interpreted as the result of subduction-induced contamination of the mantle wedge, a relic signal from now extinct Miocene-Pliocene arc volcanism. The magma compositions are also consistent with source depths above the garnet facies zone. This could explain the higher olivine δ18O values. In contrast, olivines from more southern fields do not display this O-isotope signature, consistent with postulated greater source depths.

COMUNICAÇÃO POPULAR E COMUNIDADES QUILOMBOLAS

Through a bibliographical study, the work in question discusses the concepts of community, popular communication and quilombola communities in Brazil. The aim of this article is to discuss the role of popular and community communication in communities formed by quilombola remnants. From these discussions, it was possible to point out the character focused on the emancipation of the subordinate population when developing their own forms of communication, which in turn enables their differentiation with other communication formats.

Reviews of the Mesoproterozoic to Neoproterozoic sedimentary sequences and new constraints on the tectono-sedimentary evolution of the southern margin of the North China Craton

The North China Craton (NCC) is thought to experience multi-stage extensional events after the breakup of the Columbia (Nuna) Supercontinent, and even during the assembly of the Rodinia Supercontinent. In recent years, volcanic and detrital zircon U-Pb dating ages provided new insights into the Mesoproterozoic to Neoproterozoic tectonic framework in the NCC. As the Mesoproterozoic Xiong’er Group in the southern NCC is regarded as the oldest volcanic-sedimentary succession after the final amalgamation of the NCC, we reviewed the sedimentary environments and provenances of Mesoproterozoic to Neoproterozoic sedimentary sequences above the strata in order to understand tectono-sedimentary evolution of the southern NCC during this period. The early Mesoproterozoic sedimentary rocks were deposited in alluvial-fan to fluvial and (fan-) delta-coastal environments suggesting an initial stage of basin development. Fine-grained clastic sedimentary rocks interlayered with carbonate deposition formed on the southern NCC later, and implied a broad subsidence before ca. 1611 Ma. After that, depositional breaks caused by regional tectonic uplifts led to different sedimentary sequences and lateral migration of the depocenter from the north to the south (to the current co-ordinates). The unconformably overlying sedimentary rocks in the north of the southern NCC were deposited in restricted marine basins during late Mesoproterozoic to Neoproterozoic as a whole. However, the enlargement of shallow-marine shelf led to the thick accumulation of carbonates in the southernmost NCC characterized by a deepening-upward trend from the late Mesoproterozoic sequence. The Neoproterozoic sedimentary sequence is typified by sharp increasing terrigenous supplies and frequent changes in environment, and could be deposited in a tectonically active basin in consideration of its close association with volcanism. Detrital zircon grains from the oldest clastic sequence (i.e., the Bingmagou Formation) overlying the Xiong’er volcanic-sedimentary rocks and from the earliest Paleozoic sedimentary rocks (i.e., the Xinji Formation) are used to track changes of provenances. Detrital zircon grains from the Bingmagou Formation display two dominant age peaks at ca. 1850 and 2500 Ma and three secondary peaks at ca. 2100, 2350 and 2700 Ma. In contrast, detrital zircon grains from the Xinji Formation have three major age peaks at ca. 1850, 2200 and 2500 Ma and three subordinate populations of 950, 1100 and 1450 Ma. In combination with the uplifts during the Mesoproterozoic to Neoproterozoic, Neoproterozoic magmatism, and a large amount of detrital zircon derived from Rodinia-related orogenesis in the southern NCC, it is very likely that the major changes of basin configuration could be related to significant tectonic readjustment along with the evolution of the Rodinia Supercontinent.

Re-situer la précarité en temps de crise

Ce texte, traduit pour ce dossier, inscrit la précarité au cœur d’une réflexion sur la faillite de l’autonomie présumée du sujet néolibéral. À travers l’expérience de la crise économique de l’Espagne après 2008, l’auteure décrit l’ébranlement de l’idéologie des classes moyennes, fondées sur un mirage de liberté, sur une autonomie fictive vis-à-vis des structures sociales. Elle défend le développement d’interdépendances et de codépendances, modes de vie bien connus des populations subalternes, et montre que le déclassement violent produit par la crise de 2008 aura peut-être eu l’intérêt d’affaiblir un mythe qui voit l’indépendance comme la norme et la dépendance comme l’exception. L’auteure défend ainsi une compréhension de la précarité en termes de reproduction sociale plutôt que de proposition dans les seuls rapports de production à laquelle l’ont en partie cantonnée certaines approches.

Open-system magmatic behaviour beneath monogenetic volcanoes revealed by the geochemistry, texture and thermobarometry of clinopyroxene, Kaikohe-Bay of Islands volcanic field (New Zealand)

The ascent and temporary crustal storage of magmas beneath basaltic monogenetic volcanoes in continental settings is poorly understood, but is important in the study of their petrogenesis, and for monitoring future volcanic unrest. The Kaikohe-Bay of Islands volcanic field in northern New Zealand comprises Quaternary-aged monogenetic basalt volcanoes in an intraplate setting. Clinopyroxene phenocrysts in the basalts provide an opportunity to investigate the ascent history of the magmas that may not be evident from studies at the scale of whole-rock samples. The phenocrysts are texturally and compositionally diverse, and demonstrate the dominance of open system processes such as magma mixing and crystal entrainment in the crust. Many phenocrysts have an Mg (Mg# ~80–83) and Cr rich rim overgrowth which is in equilibrium with the host rock, but a resorbed, core (Mg# ~70) that crystallised from a more evolved magma. These crystals record mafic recharge, presumably the trigger to eruption. Other crystals are characterised by a high-Mg (Mg# ~82–84) and Cr core surrounded by a disequilibrium, low-Mg (Mg# 70–75) rim. The rims are reversely zoned and demonstrate late-stage equilibrium with the host rock. These crystals either nucleated in the host magma or were entrained from earlier basaltic intrusions of similar composition. The rim zones record re-melting of intrusions, or interaction with more differentiated magmas, followed by mafic recharge. Subordinate crystal types include oscillatory zoned crystals (Mg# >80) that nucleated in the ascending magma, and diffusely, patchy-zoned crystals that are variously antecrystic or xenocrystic in origin. Cognate gabbro inclusions contain clinopyroxene in equilibrium with the host basalt, suggesting they originated from side-wall crystallisation. Crystal-melt equilibria indicate that the cognate clinopyroxene formed at 430 ± 170 MPa (2σ) (=16 ± 6 km depth), and a subordinate population formed at 730 ± 160 MPa (=28 ± 6 km depth). These depths coincide with major seismic velocity contrasts at a zone of partial melt (10–19 km) and the Moho (~28 km). Thus, buoyancy or rheology contrasts in the crust temporarily slowed magma ascent and promoted periods of crystallisation and the assimilation of antecrystic and xenocrystic components. Similar magmatic processes occurred at the neighbouring and contemporaneous Whangarei volcanic field. Both of these fields have been active for millions of years, and longevity could explain the formation of differentiated crustal instrusives. In systems where magmas temporarily stall, there is a greater likelihood of detecting pre-eruption geophysical phenomena that could act as signals to pending eruptions.

Precambrian tectonic affinity of theNorthQinlingMicrocontinent: Constraints from the discovery ofMesoproterozoic magmatic zircons in theQinlingGroup

This paper presents new results on zircon U–Pb dating of a two‐mica schist from the Qinling Group in the core of the North Qinling Orogenic Belt (NQB), Central China, with the aim of constraining the formation time of the Qinling Group, and the tectonic affinity of the North Qinling Microcontinent. Zircon U–Pb dating indicates that the protolith of the metasedimentary rock in the Qinling Group was deposited later than ~1502 Ma. The Qinling Group in the NQB represents a long‐lived unit, and its formation age can be constrained to the period between the Paleoproterozoic and early Neoproterozoic. The zircon age populations of the studied sample can be divided into two major populations of 1559–1642 and 1470–1548 Ma, and one subordinate population of 1717–1794 Ma, indicating their provenances were mainly attributed to the NQB and subordinately from the North China Craton (NCC) and the Yangtze Craton (YZC). And the distribution of the early Neoproterozoic magmatic events and the Nd–Pb whole‐rock isotopes, zircon Hf isotopes, and trace element compositions of the Precambrian basement rocks in the NQB is significantly different from those in the NCC and YZC, indicating that the NQB cannot be a southern sector of the NCC, or a northern sector of the YZC, and was an independent microcontinent from the Paleoproterozoic to the early Neoproterozoic.

New zircon U–Pb and Hf–Nd isotopic constraints on the timing of magmatism, sedimentation and metamorphism in the northern Prince Charles Mountains, East Antarctica

The northern Prince Charles Mountains (PCM) in East Antarctica represent the largest continuously exposed section of the Rayner Complex and may provide important insights into the tectonic evolution of the Rayner orogen. We present new U–Pb and Hf isotopic data for zircons from felsic orthogneisses, mafic granulites, paragneisses and charnockites and additional Nd isotopic data for the former two rock types from the Beaver Lake area in the northern PCM. Zircons from the felsic orthogneisses document protolith ages of ca. 1170–1070Ma, with Hf and Nd model ages of 1.99–1.74Ga, suggesting the generation of the felsic magmas by partial melting of crustal rocks that were extracted from the mantle during the Paleoproterozoic. Detrital zircons from one paragneiss sample yield a major age population at ca. 1480–1140Ma and three subordinate populations at ca. 2130–1850, 1780–1620 and 1010–860Ma, whereas those from another paragneiss sample produce a major age population at ca. 1180–830Ma and a subordinate age population at ca. 1370–1230Ma. Discounting the effects of zircon recrystallization during post-depositional metamorphism, we infer that the sedimentary precursors to the aforementioned paragneiss samples were deposited after ca. 1200 and 1020Ma, respectively, in intra- or back-arc basins of the Rayner continental arc. Charnockites were either emplaced at ca. 980Ma or episodically at ca. 1050 and ca. 950Ma, with Hf model ages of 1.97–1.90Ga. They were derived from partial melting of a Paleoproterozoic source region similar to the surrounding felsic orthogneisses at deeper levels. Zircon overgrowth domains from all of the studied rock types indicate that high-grade metamorphism took place at ca. 945–915Ma. Only one paragneiss sample from the Else Platform preserves evidence of Cambrian metamorphic reworking. Based on published data from the Rayner Complex and the Eastern Ghats Belt of India, we speculate that long-lived convergent processes between the Indian craton and East Antarctica lasted from ca. 1500 to 900Ma. Therefore, the Rayner Complex may represent the exposed orogenic root of a large Meso-Neoproterozoic accretionary orogen.

Neoliberal Discourses: Toward a Deeper Understanding of a Global Latino Education

This article explores the dynamic discursive interactions between two keenly related concepts, globalization and neoliberalism. Though largely synonymous in the social imaginary, in fact, these ideas are different and analytically distinct. They need unpacking. The notion that both globalization and neoliberalism are empirically verified social realities must be advanced. What’s more as they affect the global-local social relation, varying manifestations such as gentrification, the global emergence of schools of choice (charter schools), and the economic and geographic dislocations of subordinate populations become evident. Relying on empirical studies and everyday lived cultural experience in the rebuilding of the city of New Orleans post-Hurricane Katrina, I finally examine the implications for a Global Latino education and pedagogy.

Petrography and depositional environments of the sandstones in areas around Abuul, in Ushongo, southern Benue trough, Nigeria

The study focuses on the petrography and depositional setting of the sandstones in areas around Abuul, Ushongo; lower Benue Trough. The integration of outcrop, textural and petrographic studies aided the inference of the depositional framework of the sandstones in the area. Indurated sandstone samples were cut into thin sections for petrographic analysis while a total of 100 pebbles from OAM/1/Abuul were subjected to morphometric analysis. The thin section studies involved the determination of the texture and mineral/framework element compositions of the sandstones through point counting of about 100 constituent grains. The geologic mapping indicates that the sandstones are deposited proximal to the Basement Complex rocks. Thin section results show that the sandstones are coarse-grained and poorly sorted lithic arkoses, predominantly comprising of angular framework elements, with low textural and chemical maturity, possibly deposited in a fluvial setting. The result from pebble morphometry analysis also confirmed that the sands are fluvial. The bivariate plots of the pebble studies indicate a dominating population of fluvial-influenced pebbles in association with a subordinate population of beach influenced pebbles. However, minor grain compression is evident through the observed sediment compaction, stretched grains and presence of quartz overgrowths in some of the sandstones. This study has shown that the sandstones in the area are deposited by fluvial dominated processes, with the interaction of beach processes, though to a lesser degree.Keywords: textural analysis, sandstone petrography, depositional setting

Neoproterozoic arc magmatism in the southern Madurai Block, India: Subduction, relamination, continental outbuilding, and the growth of Gondwana

The Madurai Block in southern India is a composite collage of at least three sub-blocks, with Neoarchean–Paleoproterozoic segments in the north and central domains, and a Neoproterozoic segment in the south. Here we investigate a suite of rocks with magmatic protoliths that constitute the basement in the southern margin of the Madurai Block including alkali granites, charnockites, enderbites and gabbros. The alkali granites are dominantly composed of perthitic K-feldspar, minor plagioclase and quartz, with hornblende as the main mafic mineral suggesting a calc-alkaline nature. The enderbites and charnockites have a broadly similar mineralogical constitution except for the variation in the modal content of plagioclase, K-feldspar and quartz, as well as the additional presence of clinopyroxene in some of the enderbites. The high modal content of hornblende in the gabbros suggests crystallization from hydrous basaltic melts. The geochemical features of this suite are identical to those of arc magmatic rocks, with distinct Nb, Ta, and Ti depletion suggesting magmatism in a subduction-related environment. We envisage that the underplating of basaltic magmas within a convergent margin setting provided the heat input for lower crustal melting generating the charnockitic suite of rocks. The intrusion of the underplated mafic melts as gabbroic dykes and sills into the crystallizing felsic magmas resulted in magma mixing and mingling generating the widespread enclaves of gabbroic rocks. The alkali granites were derived from the differentiation of lower crustal melts. Zircon U–Pb data from the alkali granites yield weighted mean 206Pb/238U ages of 786±10 to 772±11Ma for the oldest and the most dominant group of magmatic grains, with a 662±20Ma subordinate group. The oldest group of magmatic zircons in the charnockite samples shows ages of 938±27Ma, 896±12Ma, and 786±9Ma, suggesting multiple magmatic pulses during early and mid-Neoproterozoic. A subordinate population of magmatic zircons with ages of 661±9Ma and 632±7Ma is also present. In the enderbites, the magmatic zircon population yields weighted mean ages of 926±22Ma, 923±36Ma, 889±13Ma, 803±10Ma, 787±23Ma, 786±10Ma, 748±27Ma, 742±11Ma, 717±8Ma and 692±10Ma suggesting continuous and multiple pulses of magmas emplaced throughout early to mid-Neoproterozoic. Magmatic zircons from the gabbros show weighted mean 206Pb/238U ages of 903±13Ma, 777±10Ma, 729±10Ma and 639±27Ma. Metamorphic zircons from all the rock types show latest Neoproterozoic-Cambrian ages in the range of 567±19Ma to 510±8Ma suggesting prolonged heating. Zircon Lu–Hf data show that the alkali granite-charnockite-enderbite suite has depleted mantle ages (TDM) in the range of 1164–2172Ma and crustal residence ages (TDMC) of 1227–3023Ma. These spots show both negative εHf(t) and positive εHf(t) values (−22.1 to 10.6), suggesting magma derivation from mixed juvenile mid- to late-Mesoproterozoic components and reworked Mesoarchean to mid-Mesoproterozoic components. Zircon grains from the gabbroic rocks show depleted mantle ages and (TDM) in the range of 1112–2046Ma, crustal residence ages (TDMC) of 1306–2816Ma, and both negative and positive εHf(t) values (−17.8 to 7.9), suggesting that the magmas were dominantly derived from juvenile mid-Mesoproterozoic to Neoproterozoic components as well as reworked Mesoarchean to mid-Mesoproterozoic sources.Our data clearly reveal multiple arc magmatism along the southern Madurai Block during distinct pulses throughout early to late Neoproterozoic, suggesting an active convergent margin along this zone at this time. Crustal thickening occurred through relamination by mafic magmas associated with slab melting. Continental outbuilding and southward growth of the Madurai Block were associated with the lateral accretion of the vast sedimentary belt of Trivandrum Block, culminating in collisional metamorphism during latest Neoproterozoic–Cambrian associated with Gondwana assembly.