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Abstract: The Voorspoed Group II kimberlite pipe is atypical in terms of South African kimberlite pipes. Located in the central region of the Kaapvaal Craton (South Africa), the Voorspoed pipe is one of six pipes comprising the Kroonstad Kimberlite Cluster. Reconstruction of the palaeo-stratigraphy at the time of emplacement, of the Kroonstad kimberlites, indicates that significant post-emplacement erosion has occurred and the pipes are currently exposed at ~1600m depth from the original land surface. The volcaniclastic kimberlite (VK) infilling the pipe is distinctly different from typical tuffisitic kimberlite infilling other South African type kimberlite pipes. Three textural volcaniclastic kimberlite varieties are observed: massive volcaniclastic kimberlite (MVK), bedded volcaniclastic kimberlite (BVK) and fine-grained volcaniclastic kimberlite (fgVK) layers. The BVK and fgVK are volumetrically insignificant and the bulk of the pipe is infilled with MVK. The MVK can be further sub-divided into seven varieties. The two dominant varieties are described in detail, which include: main MVK (mMVK) and the juvenile-rich MVK (jrMVK). The MVKs are typically massive, clastic, poorly sorted and supported by an interclast material consisting of juvenile and xenocrystic crystals in a mud-rich matrix. Magmaclasts within the MVKs are spherical, crystalline with a typical coherent hypabyssal texture and different mineralogical varieties are typically juxtaposed. BVK units are composed of several normally graded beds of volcaniclastic material. fgVK layers are well sorted relative to the MVKs and all constituents are typically <2mm in size. The BVK and fgVK can be deposited only within an open vent in order to account for the sorting of the components. A distinct basalt and sandstone rich unit (bsBreccia), which is essentially devoid of kimberlite material, is also observed. Three volcaniclastic zones are identified based on consistent vertical variation in the internal stratigraphy of the infill: outer east/west zone with a sequence bsBreccia–BVK–mMVK/softMVK; a central zone with a sequence mMVK–BVK–jrMVK–mMVK and an outer north zone with a uniform mMVK sequence. The evidence suggests that the volcaniclastic infill has formed through complex processes involving re-working of extra-crater tephra back into the vent and coeval pyroclastic deposition. It is also likely that there is significant mixing of the resedimented and pyroclastic deposits. Distinction between deposits formed through re-working of material through repeated explosive eruptions within the vent and that formed through varying degrees of re-working extra-crater tephra from the surface (with possible coeval pyroclastic eruption) is probably impossible. For this reason we interpret the mMVK as being deposited by dominantly resedimentation of tephra whereas the jrMVK has been deposited dominantly by pyroclastic processes. The presence of BVK and fgVK deposited deep within the pipe through slumping of the crater margins at the surface suggests that a crater ~2000m in depth was periodically open. The identification of the complex, layered, variable internal structure of the volcaniclastic infill at the Voorspoed has significant implications for diamond ore evaluation in South Africa. Typical South Africa kimberlite pipes are infilled with tuffisitic kimberlite, which are characterised by their homogenous nature over large vertical intervals (>1000m). This is not the case at the Voorspoed pipe where MVK layers are variable in thickness (<10m up to 230m). [Copyright &y& Elsevier]

Abstract: The crestal portion of the upper-crustal Wallowa batholith, northeastern Oregon, provides an exceptional three-dimensional section through a flat batholith roof which rolls over into a steep wall at elevations of about 1600–2800m. The roof–batholith margin is interpreted as representing the ‛frozen-in’ process zone of granodiorite magma which was arrested during its ascent, thus providing a direct view into processes that operate during construction of large, shallow-level Cordilleran-type batholiths. The batholith host rock records two principal and presumably coeval emplacement processes: ductile flow largely accommodated by rheologically weak and thus severely deformed marbles in the steep wall, and voluminous stoping of rheologically stronger, bedded siliciclastic rocks along the flat roof. Structures preserved along the roof suggest that the stoping was a multi-stage process involving emplacement of up to hundred meters long sills along bedding planes and formation of short connecting dikes cutting across bedding to produce sill–dike networks along the batholith–roof contact. Portions of the sill–dike networks and enclosed large rectangular roof blocks were then stoped into and continued to be mechanically disintegrated in the magma chamber. This inferred mechanism departs from the commonly assumed mode of stoped block formation solely by thermal shattering. In our view, host rocks in the process zone are fractured by dike propagation. It follows that such process of roof disruption and subsequent block stoping could be extremely rapid. In combination with other processes (e.g., roof uplift, ductile flow in weak lithologies), such rapid stoping could contribute to emplacement of voluminous and mostly non-sheeted Cordilleran-type batholiths at upper crustal levels. [Copyright &y& Elsevier]

While panoramas and dioramas are widely seen as representational forms and were once celebrated for their realism, they had an ambivalent status as art forms and evoked passionately discordant reactions from critics and observers. The ambivalent responses to these forms have been understood in terms of elitist reactions to their mass appeal and to their deception. The implications of the sensorial disruption that temporary inhabitants of these structures experienced in their initial encounters with them has not been given much attention. The panorama and diorama strove beyond representational depiction and towards the production of a full-bodied experience. Hence, they should be considered not as novelty paintings, nor even as primarily visual media, as is typically the case, but rather as significant forms of intermedia that both relied upon and re-educated the sensorial capacities of their inhabiting human subjects. This article accordingly treats panoramic and dioramic forms as more architectural than artistic and argues for their recognition as intersensorial and transitory constructions that produced a normative reordering of intersensorial subjective space. [ABSTRACT FROM AUTHOR]

The texts and landscapes of my life work together in uncanny ways that are leading me to a divine beyond the closures of my skin and mind. My religious reading of Emily Brontë's Wuthering Heights particularly meshes with connected moments of experience in place that complicate and extend the possibilities of my divine. Here I leave Victoria, escorted by the grace of the East, to encounter Victorianist thinking that explores textual afterlives and ancestral haunting. This prepares me well to lose my singularity to the moors of Brontë's text. In a playful gothic gathering that follows, I begin to understand that textual emplacement and physical displacement create productive refractions between lingual, spacial and temporal prisms, creating boundless connections that perforate my containment with an echoing divine of faithful peace. [ABSTRACT FROM AUTHOR]

In this article I examine the impassioned yet ambivalent accounts of ‘resettlement’ recalled by the residents of a neighbourhood settled as part of a wider slum clearance drive during the state of Emergency, a period of autocratic rule declared in India between 1975 and 1977. In the context of a sometimes overbearing and at times violent postcolonial state, this article seeks to understand what people do with these accounts. Considering how narrators ‘emplot’ themselves in relation to their neighbourhood within these stories, I suggest these accounts can be understood as narratives of ‘emplacement’. By engaging with both the content of the stories narrated, but also their social and spatial dimensions, narration can be seen as a social act and a spatial practice, as residents seek to emplot, incorporate and exclude others in difficult social relations. By considering the narration of place as a spatial practice, the more subtle and contradictory processes of dwelling in the city are opened up for consideration, how people create spaces to live in and speak from in the maelstrom of city life. [ABSTRACT FROM PUBLISHER]

Spinoza identifies memory as central to all human endeavour. In this article, I explore the diverse kinds of remembering that informed the writing of my award-winning Gothic short story 'The Stinker' (2006). I utilize approaches from the fields of cultural studies and the emergent, transdisciplinary arena of memory studies to explore the myriad embodied and emplaced memories that influenced the story's production. I contend that the interrelationship of these varieties of remembering ought to be understood in a processual rather than dynamic fashion. The article is followed by the text of 'The Stinker'. [ABSTRACT FROM AUTHOR]

The calc-alkaline Miřetín Pluton (newly dated at 346 Ma ± 5 Ma; an U-Pb age obtained by laser-ablation ICP MS method on zircons) is a NNE-SSW elongated intrusive body emplaced into the upper- to mid- crustal rocks of the Polička Unit (eastern Teplá-Barrandian Zone; Bohemian Massif). Its composition reveals similarities to other calc-alkaline granitoids, which are mostly interpreted as products of magma mixing between the basic magmas derived from mantle wedge above a subduction zone with crustally-derived acid melts. The conditions of magma crystallization estimated at 653-681 °C and 0.29-0.43 GPa roughly correspond to peak metamorphic evolution of the host volcano-sedimentary rocks of the northwestern part of the Polička and Hlinsko units. The Miřetín Pluton was emplaced into a NNE-SSW oriented transpressional domain, well recognized on a regional scale along the eastern margin of the Teplá-Barrandian Zone. During, or shortly after the magma emplacement, the Miřetín Pluton was affected by pervasive submagmatic to high-T solid-state deformation, reflecting an additional strain increment of regional transpression in a narrow zone of thermal softening. Sharply superimposed low-T solid-state fabric preserved along the western part of the Pluton was connected with normal shearing between the Polička Unit at the bottom and the overlying Hlinsko Unit after 335 Ma. [ABSTRACT FROM AUTHOR]

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Abstract In this article, I argue that the commemoration of slavery should be seen as a process of emplacement. It refers to a specific politics of belonging in the Netherlands that is focused on autochthony and that carries strong notions of place. I discuss two strategies of emplacement that both engage in these politics of belonging. One is the search for roots in Africa, through which black Dutch negotiate their place in Netherlands as citizens. The other engages in the transformation of the Dutch memoryscape through formal commemorations and monuments. I understand both strategies as processes generating local subjects in Appadurai's sense, emphasizing that locality as a relationship of body and place is a fundamental ingredient in processes of political subjectification. [ABSTRACT FROM AUTHOR]

The elite safari lodges in Botswana's Okavango Delta provide an intriguing site through which to explore processes of identity construction, as people from vastly different backgrounds meet and explore ontological possibilities through and against each other. Drawing on a dinner table dispute between an African American tourist and his white Motswana guide, I explore contested notions of what constitutes African identities. The encounter shows that colonial histories and the racialization of space continue to be central to African identity politics, and I describe how white citizens' claims to belonging are challenged on these grounds. In response to such challenges, white Batswana assert a strongly nationalistic identity, distancing themselves from other southern African white populations and their colonial histories. They staunchly defend their claims to belonging through mobilising a partial view of Botswana's history and contemporary sociopolitical conditions, which has made possible a deep sense of emplacement within the social and natural environments of the Okavango. [ABSTRACT FROM PUBLISHER]

Spinoza identifies memory as central to all human endeavour. In this article, I explore the diverse kinds of remembering that informed the writing of my award-winning Gothic short story 'The Stinker' (2006). I utilize approaches from the fields of cultural studies and the emergent, transdisciplinary arena of memory studies to explore the myriad embodied and emplaced memories that influenced the story's production. I contend that the interrelationship of these varieties of remembering ought to be understood in a processual rather than dynamic fashion. The article is followed by the text of 'The Stinker'. [ABSTRACT FROM AUTHOR]

Abstract: Studies of Anisotropy of Magnetic Susceptibility (AMS) and U-Pb geochronology, in zircon fractions, were carried out in a magnetite type-granite, the Lavadores granite, which is an example of a late to post-orogenic Variscan granite in northern Portugal (NW Iberian Peninsula). The U-Pb zircon analyses yield an age of 298±11 Ma that is considered to be the emplacement age of this granite and thus suggesting a post-tectonic emplacement. This is also supported by the magmatic nature of the microstructures. Magnetic lineations are subvertical and magnetic foliations display a general WNW-ESE subvertical pattern consistent with a dextral kinematic. These AMS data suggest that the emplacement of the Lavadores granite was controlled by a major mechanical anisotropy formed by transtensional structures associated with the Porto-Tomar shear zone. [Copyright &y& Elsevier]

In this article I discuss how a shift from theories of embodiment to one of emplacement can inform how we understand the performing body in competitive and pedagogical contexts. I argue that recent theoretical advances concerning the senses, human perception and place offer new analytical possibilities for understanding skilled performances and events. In doing so I critically re-think my own analysis of the Spanish bullfight as an embodied performance to demonstrate the benefits of a shift from embodiment to emplacement as a theoretical and methodological approach; and propose that there are wider implications of such a theoretical shift for interpreting performances in other cultural and social contexts. [ABSTRACT FROM AUTHOR]

This paper introduces the contents of the special issue whose authors, in our view, together demonstrate the need for transdisciplinary study of body pedagogies focussed on embodiment, emplacement, enactment and subjectivity. We celebrate theoretical and methodological diversity in the social sciences while calling for border crossings between the disciplines and perspectives of the social and bio-physical sciences in the interest of better understanding how social and cultural reproduction occurs both within schools and beyond them. [ABSTRACT FROM AUTHOR]

The subject of auspiciousness and inauspiciousness in South Asian society has largely been analyzed as a temporal condition in which there is a harmonious or inharmonious conjunction of people and events in time. In this article, the construction of houses by high-caste people living in a hamlet in Nepal is used to argue for a reconceptualization of auspiciousness and inauspiciousness as practices of emplacement in space and time. The analysis demonstrates how the rituals associated with the various stages of construction ensure the new house's compatibility with its spatial milieu-the soil, the site, the cardinal directions, and the reigning deities, as well as the vital force of the earth. Together with the auspicious timing of each stage of construction and its associated ritual with the owner's horoscope, the result of the building process shows auspiciousness to be a harmonious conjunction of person, place, and time. [ABSTRACT FROM AUTHOR]

Abstract: The formation and growth of magma bodies are now recognised as involving the amalgamation of successive, discrete pulses such as sills. Sills would thus represent the building blocks of larger plutons (sensu lato). Mechanical and thermal considerations on the incremental development of these plutons raise the issue of the crustal levels at which magma can stall and accumulate as sills. Reviewing the mechanisms that could a priori explain sill formation, it is shown that principal physical controls include: rigidity contrast, where sills form at the interface between soft strata overlaid by comparatively stiffer strata; rheology anisotropy, where sills form within the weakest ductile zones; and rotation of deviatoric stress, where sills form when the minimum compressive stress becomes vertical. Comparatively, the concept of neutral buoyancy is unlikely to play a leading control in the emplacement of sills, although it could assist their formation. These different controls on sill formation, however, do not necessarily operate on the same length scale. The length scale associated with the presence of interfaces separating upper stiffer layers from lower softer ones determines the depth at which rigidity-controlled sills will form. On another hand, the emplacement depths for rheology-controlled sills are likely to be determined by the distribution of the weakest ductile zones. Whereas the emplacement depth of stress-controlled sills is determined by a balance between the horizontal maximum compressive stress, which favours sill formation, and the buoyancy of their feeder dykes, which drives magma vertically. Ultimately, the depth at which a sill forms depends on whether crustal anisotropy or stress rotation is the dominant control, i.e. which of these processes operates at the smallest length scale. Using dimensional analysis, it is shown that sill formation controlled by remote stress rotation would occur on length scales of hundreds of meters or greater. This therefore suggests that crustal heterogeneities and their associated anisotropy are likely to play a larger role than remote stress rotation in controlling sill emplacement, unless these heterogeneities are several hundred meters or more apart. This also reinforces the role of local stress barriers, owing to interactions between deviatoric stress and crustal heterogeneities, in the formation of sills. [Copyright &y& Elsevier]

Abstract: To extend knowledge of relationships between people and domestic settings in the context of medication use, we conducted fieldwork in twenty households in New Zealand. These households contained a range of ‘medicative’ forms, including prescription drugs, traditional remedies, dietary supplements and enhanced foods. The location and use of these substances within domestic dwellings speaks to processes of emplacement and identity in the creation of spaces for care. Our analysis contributes to current understandings of the ways in which objects from ‘outside’ the home come to be woven into relationships, identities and meanings ‘inside’ the home. We demonstrate that, as well as being pharmacological objects, medications are complex, socially embedded objects with histories and memories that are ingrained within contemporary relationships of care and home-making practices. [ABSTRACT FROM AUTHOR]

This article addresses the intersection of sexual orientation and religion and belief through a focus on a specific religious community — the worldwide Anglican Communion. It does so by unpacking a particular event within this Communion debate: the decennial Lambeth Conference, at Canterbury, UK. Events have received little attention within sociology, yet case studies of particular events potentially represent an effective way of empirically researching the complexity of the ways that intersections of categories, such as sexual orientation and religion and belief, are experienced in everyday life. By focusing on the strategies of pro-LGBT (lesbian, gay, bisexual and transgender) groups at Lambeth, this article demonstrates how, in the material space of an ‘event’, abstract discourses and positionings in diffuse social networks become transformed into tangible emplaced social relations where power is outworked. [ABSTRACT FROM PUBLISHER]

Geological observations in the Horoman area, south-central Hokkaido, show that the Horoman peridotite complex of the Hidaka metamorphic belt is a tectonic slice about 1200 m thick. The peridotite slab is intercalated into a gently east-dipping structure. The underlying unit is a Cretaceous–Paleogene accretionary complex. Riedel shear planes in the sedimentary layers of the accretionary complex near the structural bottom of the peridotite slab indicate top-to-the-west (thrust) displacement. The overlying unit is composed of felsic–pelitic gneisses and mafic–felsic intrusive rocks (the Hidaka metamorphic rocks). The boundary surface between the peridotite complex and metamorphic rocks forms a domal structure. Microstructures of sheared metamorphic rocks near the structural top of the peridotite slab indicate top-to-the-east (normal) displacement. The results combined with previous studies suggest that the Horoman peridotite complex was emplaced onto the Asian margin (Northeast Japan) during the collision between the Asian margin and the Hidaka crustal block. [ABSTRACT FROM AUTHOR]

Abstract: The initial development of long lava flows is investigated using simple theory and field evidence. Order-of-magnitude estimates of the evolving thickness and the extending length of lava are obtained by scaling arguments based on the simplification that the bulk structure can be modelled initially as a Newtonian fluid. A scaling analysis suggests that the rate of advance of the leading front evolves primarily due to temporal variations in the effusion rate and minimally due to topography. The apparent viscosity of the bulk flow increases with time at subsequent stages when effects due to cooling become important. Theoretical results are applied to the study of long lava flows that descended on Etna, Kilauea and Lonquimay volcanoes. We determine that lava flows at Kilauea extended initially like a Newtonian fluid with constant viscosity, implying that thermal effects did not significantly influence the dynamic properties of the bulk flow. In contrast, effects due to cooling played a major role throughout the advance of lava flows at Etna and Lonquimay. We show that the increasing length and volume of an active emplacement field can be monitored to estimate its evolving viscosity, which in turn allows the further advance of the lava to be predicted. [ABSTRACT FROM AUTHOR]

We report here emplacement of small scale inflated pahoehoe lava flows in the Mandla lobe of the Eastern Deccan Volcanic province (EDVP). These lava flows are thick and display entire range of characters similar to that occurring in the Western Deccan Volcanic Province (WDVP). Size of the lobe in these lava flows is very small and they are less in number compared to those occurring in the WDVP. Moreover, simple lava flows that occur in the younger sequences of the basalts around Mandla area, form extensive sheets and look like a lava field. Physical characteristics of Mandla lavas are suggestive of lower effusive rates, linked with the low magnitude of eruption, possibly related to its long distance migration from a common source, located in the western Deccan province. [ABSTRACT FROM AUTHOR]

Abstract: The Yubileinaya kimberlite pipe, with a surface area of 59 ha, is one of the largest pipes in the Yakutian kimberlite province. The Devonian pipe was emplaced under structural control into Lower Paleozoic karstic limestone. The pipe complex consists of several smaller precursor pipes which are cut by the large, round Main pipe. While the precursor pipes show many features typical for root zones, Main pipe is younger, cuts into the precursor pipes and exposes well-bedded volcaniclastic sediments. The maximum estimated erosion since emplacement is 250 m. Open pit mapping of a 180 m thick kimberlite sequence documents the waning phases of the volcanic activity in the kimberlite pipe and the onset of its crater infill by resedimentation. Three volcanic lithofacies types can be differentiated. The deepest and oldest facies type is a massive volcaniclastic rock (“AKB”) only accessible in drill core. It is equivalent to Tuffisitic Kimberlite in South African pipes and thought to be related to the main volcanic phase which was characterized by violent explosions. The overlying lithofacies type comprises primary and resedimented volcaniclastic sediments as well as rock avalanche deposits sourced from the exposed maar crater collar. It represents the onset of sedimentation onto the crater floor during the waning phase of volcanic eruptions, where primary pyroclastic deposition was contemporaneous with resedimentation from the tephra wall and the widening maar crater. Ongoing volcanic activity is also testified by the presence of a vertical feeder conduit marking the area of the last volcanic eruption clouds piercing through the diatreme. This feeder conduit is overlain by the third and youngest lithofacies type which consists mainly of resedimented volcaniclastic material and lake beds. During the sedimentation of this facies, primary volcanic activity was only minor and finally absent and resedimentation processes dominated the crater infill. The Yubileinaya pipe complex exposes root zones, contact breccias as well as diatreme and crater infill sediments. It has all features typical of large South African-style pipes and much can be learned from Yubileinaya about the emplacement sequence and behaviour of these pipes. Emplacement of the pipe occurred over an extended time span with intermittent phases of volcanic quiescence and consolidation. The AKB reveals little direct evidence of what sort of emplacement process was dominant during the main period of volcanic activity. There is neither textural evidence that violent degassing of a juvenile gas phase has caused pipe excavation, nor that external water was present during the main phase of volcanic eruptions. However, there is clear evidence in rock textures that meteoric surface water was present during crater infill. Base surge deposits forming part of the bedded crater infill sequence indicate that water was present in the eruption clouds and, hence, the root zone of the pipe. There is no reason to assume that groundwater did not also have access to the ascending magma during the main phase of volcanic activity that excavated the pipe and formed the AKB. [Copyright &y& Elsevier]

Abstract: The Middle Cambrian (~540 Ma) Gahcho Kué Kimberlite Field is situated about 275 km ENE of Yellowknife, NWT, Canada. The kimberlites were emplaced into 2.6 Ga Archean granitic rocks of the Yellowknife Supergroup. Four larger kimberlite bodies (5034, Tesla, Tuzo, and Hearne) as well as a number of smaller pipes and associated sheets occur in the field. In plan view, the Tuzo pipe has a circular outline at the surface, and it widens towards deeper levels. The pipe infill consists of several types of coherent and fragmental kimberlite facies. Coherent or apparent coherent (possibly welded) kimberlite facies dominate at depth, but also occur at shallow levels, as dikes intruded late in the eruptive sequence or individual coherent kimberlite clasts. The central and shallower portions of the pipe consist of several fragmental kimberlite varieties that are texturally classified as Tuffisitic Kimberlites. The definition, geometry and extent of the geological units are complex and zones controlled by vertical elements are most significant. The fluidal outlines of some of the coherent kimberlite clasts suggest that at least some are the product of disruption of magma that was in a semi-plastic state or even of welded material. Ragged clasts at low levels are inferred to form part of a complex peperite-like system that intrudes the base of the root zone. A variable, often high abundance of local wall-rock xenoliths between and within the kimberlite phases is observed, varying in size from sub-millimeter to several tens of meters. Wall-rock fragments are common at all locations within the pipe but are especially frequent in a domain with a belt-like geometry between 120 and 200 m depth in the pipe. Steeply outward-dipping bedded deposits made up of wall-rock fragments occur in deep levels of the pipe and are especially common under the downward-widening roof segments. The gradational contact relationships of these deposits with the surrounding kimberlite-bearing rocks as well as their location suggest that they formed more-or-less in situ. Different breccia facies inside the pipe suggest an origin by slumping, grain flows, rock fall or pyroclastic deposition. The shape and facies architecture of the Tuzo pipe suggests that the studied section of the pipe lies at a root zone–diatreme transitional structural level. Composite coherent kimberlite clasts imply that recycling processes were active over time, while reworked wall-rock rich deposits and ductily-deformed clasts of welded kimberlite point to the presence of temporary cavities in the root zone. The emplacement of the Tuzo pipe did not occur in a single, violent explosion, but involved repetitive volcanic explosions alternating with periods of relative quiescence. The observed features are typical of phreatomagmatic processes, which may include phases of less-explosive magmatic activity. [Copyright &y& Elsevier]

Abstract: The A154N kimberlite pipe is part of the Diavik kimberlite cluster in the Northwest Territories, Canada. The pipe is filled by deposits that record a sequence of eruptive and intrusive events for which we have established relative times and modes of emplacement. As such, this sequence of kimberlite deposits provides a unique opportunity to explore the connections between magma properties, pipe or conduit geometry and eruption style. Deposits within the A154N pipe represent four discrete volcanic events including: (1) an array of pre-cursor dykes of coherent kimberlite that intrude the adjoining country rock (CK1); (2) pyroclastic deposits recording the explosive eruption of A154N (PK1); (3) late dykes of coherent kimberlite intruding the main infill of the pipe (CK2); and (4) a sequence of water-laid pyroclastic deposits that sourced from another kimberlite volcano (PK2). We use observations on polished slabs and thin sections to characterize the magma that erupted to produce each deposit. Image analysis techniques are used to quantify olivine content (abundance and size distributions) and abundances of vesicles within deposits and within individual juvenile pyroclasts. Our analysis shows that during the eruption cycle (CK1 to PK1 to CK2), olivine content increased and volatile content decreased. Lastly, we estimate physical properties for the magmas that produced each deposit. The magma properties are combined with 3-D models for the geometry of the conduit at the time of eruption to constrain the mass flux and duration of each eruptive event. Steady-state assumptions for velocity and magma flux yield total eruption durations of minutes to hours. The diversity of textures and compositions recorded in pyroclastic kimberlite (PK1) and dykes of coherent kimberlite (CK1 and CK2) are a possible manifestation of separated three-phase flow involving kimberlite melt and crystals, and an ever-increasing proportion of exsolved CO2–H2O fluid. Specifically, we suggest that the early dykes (CK1), pyroclastic kimberlite (PK1), and late-stage dykes (CK2) are representative of three separate regimes of kimberlite magma created by the ascent of a vigorously degassing magma. We envisage this being composed of: (a) the gas-charged front of the magma created by decoupling the more buoyant gas phase from the silicate melt; (b) a transient, gas-rich body of magma in which later-stage exsolved fluids/gases are essentially coupled to the melt; and (c) a fluid-depleted tail of magma which remains buoyant within the lithosphere but ascends more slowly than the fluid and exsolving gas phases. [Copyright &y& Elsevier]

Abstract: The Renard 2 kimberlite is located in the Otish Mountains region of Quebec, Canada and is one of the largest pipes in the Renard cluster. The cluster consists of nine kimberlite bodies and was discovered in 2001 by Ashton Mining of Canada Inc. and its joint venture partner SOQUEM Inc. Renard 2 was emplaced into Archean meta-greywacke derived migmatite, gneiss and granite of the Opinaca Subprovince of the eastern Superior Province at approximately 640.5±2.8Ma. An undetermined amount of erosion has occurred since emplacement with the present surface expression of the pipe estimated to be 0.75ha. This kimberlite is interpreted as a steep-sided diatreme with minor irregularities in the external shape. The dominant infill is a massive volcaniclastic kimberlite (MVK) that is classified as tuffisitic kimberlite breccia (TKB) and is characterized by a high proportion of granitoid country rock xenoliths. A second dominant infill is a texturally complex, less diluted coherent kimberlite (CK) characterized locally by a transitional textures between CK and TKB. Surrounding the diatreme is a significant zone of variable width comprised of extensively brecciated country rock (+/−kimberlite) and referred to as marginal breccia. In addition to the two main rock types infilling the pipe, a number of hypabyssal kimberlite (HK) dykes and irregular shaped intrusions occur throughout the body, along the pipe contacts, within the marginal breccia and in the surrounding country rock. Geological features displayed by Renard 2 are similar to those described from Class 1 kimberlites of the Kimberley area of South Africa, the Gahcho Kué cluster of Canada and the Pimenta Bueno kimberlite field of Brazil. The economic evaluation of Renard 2 is in progress and to date has included extensive diamond and reverse circulation drilling as well as the collection of an underground bulk sample. Results from material sampled from Renard 2, including a 2449tonne bulk sample, suggest Renard 2 has an estimated diamond content of 83cpht (carats per hundred tonnes). A three dimension geology model of the pipe has been developed following the investigation of drill cores, subsurface mapping and petrography combined with diamond studies and geophysics. The model produced is being used to guide and direct the evaluation of the kimberlite and unravel the emplacement history of the pipe. [Copyright &y& Elsevier]

Abstract: The economic potential of kimberlite bodies is defined by the volume and diamond content of all their internal units which are summarised in three dimensional geological models. Canadian geological models reveal distinct types of kimberlite bodies characterised by fundamentally different emplacement processes and products. Data for representative samples of Canadian kimberlites are used to show that qualitative and quantitative macroscopic petrography (olivines and xenoliths) are powerful and practical techniques in assessing the economic implications of emplacement within individual phases of kimberlite. Kimberlite bodies result from the near-surface emplacement of multiple discrete batches of mantle-derived magmas, each carrying different diamond populations and, in some instances, subsequent resedimentation processes. Magmas containing ~25 modal % of olivine macrocrysts, the average maximum load of solids that can be carried to surface by a kimberlite magma, have the greatest potential to be significantly diamondiferous. Modifications to the abundance and size distribution of the olivine macrocrysts in each batch of magma commonly occur during emplacement. The modifications to the olivine macrocrysts, which vary with different emplacement processes and products, are mirrored in the macrodiamond content. Dilution by xenoliths is important in predicting diamond contents but it is also reflected in reduced olivine contents. Thus, olivine macrocrysts can act as a proxy for macrodiamonds. The abundance and size distribution data for olivine can improve the prediction of diamond grade and distribution within, and between, kimberlite units. Summary geological models and macroscopic petrography, together, improve the evaluation of newly discovered bodies resulting in enhanced resource estimates and increased degrees of confidence. [Copyright &y& Elsevier]

The Mammoth Peak sheeted intrusive complex formed in the interior of a ~7–10 km deep magma chamber, specifically in the Half Dome granodiorite of the Tuolumne batholith, central Sierra Nevada, CA (USA). The sheets consist of fractionated melts with accumulated hornblende, biotite, magnetite, titanite, apatite, and zircon. The accumulation, especially of titanite, had a profound effect on minor and trace elements (Nb, Ta, Ti, REE, U, Th, P, Zr, Hf, etc.), increasing their contents up to five to six times. Our thermal–mechanical modeling using the finite element method shows that cooling-generated tensile stresses resulted in the inward propagation of two perpendicular sets of dilational cracks in the host granodiorite. We interpret the sheeted complex to have formed by a crack-seal mechanism in a high strength, crystal-rich mush, whereby outward younging pulses of fractionated magma were injected into these syn-magmatic cracks at the margin of an active magma chamber. Thermal–mechanical instabilities developed after the assembly of the sheeted complex, which was then overprinted by late ~NW–SE magmatic foliation. This case example provides a cautionary note regarding the interpretation that sheeted zones in large granitoid plutons imply a diking mechanism of growth because the sheeted/dike complexes in plutons (1) may display inverse growth directions from the growth of the overall intrusive sequence; (2) need not record initial chamber construction and instead may reflect late pulsing of magma within an already constructed magma chamber; (3) have an overprinting magmatic fabric indicating the continued presence of melt after construction of sheeted complexes and thus a prolonged thermal history as compared to dikes; and (4) because the scale of the observed sheeted complexes may be small (<1%) in comparison to large homogenous parts of plutons, in which there is no evidence for sheeting or diking. Thus, where extensive dike complexes in plutons are absent, such as in much of the Tuolumne batholith, the application of an incremental diking model to explain chamber construction is at best speculative. [ABSTRACT FROM AUTHOR]

Abstract: Multidisciplinary studies integrating, U–Pb geochronology, whole-rock geochemical data, isotope geochemistry, anisotropy of magnetic susceptibility (AMS) studies and gravimetry were carried out on the Vila Pouca de Aguiar and the Águas Frias-Chaves porphyritic biotite granite plutons. Both plutons occur independently in a distance of about 20 km. The Vila Pouca de Aguiar and Águas Frias-Chaves plutons are examples of late to post-orogenic felsic Variscan granites in northern Portugal (NW Iberian Peninsula). The U–Pb zircon analyses yield a consistent age of 299±3 Ma which is considered to be the emplacement age of the two plutons. These granites are weakly peraluminous, show high HREE and Y (and low P) contents which are consistent with them being I-type. This is also supported by their weakly evolved isotopic compositions, 87Sr/86Sri =0.7044–0.7077 and εNd=−2.0 to −2.6, as well as by the whole rock oxygen isotope (δ 18O VSMOW) ranging from +9.7‰ to +11.0‰. The emplacement of granite magma took place after the third Variscan deformation phase (D3) in an extensional tectonic regime, large scale uplift and crustal thinning. The integration of different data suggests that both plutons have the same feeding zone aligned within the Penacova-Régua-Verin fault (PRVF) and that both have the same structure which is related to late Variscan phases. The thicker shape for the Águas Frias-Chaves pluton comparing to that of the Vila Pouca de Aguiar pluton is compatible with different depths of PRVF sectors. The available data led us to propose a model of partial melting of a meta-igneous lower crustal source rather than an open-system of mantle–crust interaction. The interaction between the continental crust and invading mafic magmas could have been limited to mere heat transfer and, perhaps, local intermingling. [Copyright &y& Elsevier]

Serpentinites along the boundaries of the Hastings Block, southern New England Orogen, eastern Australia, contain S, C and C' structures that provide information on the kinematic history of faults bounding the block. The serpentinite bodies at Yarras on the western boundary of the Hastings Block within the Ralfes Creek, Taylors Creek and Old Highway-Yarras Mountain Trail Faults display dominantly sinistral strike-slip or oblique-slip movement. Serpentinite bodies between these faults record dextral strike-slip and oblique-slip movement histories as well as sinistral strike-slip or oblique-slip and rare normal, dip-slip movement. The Mt George Serpentinite consists of a northeast-oriented section folded and displaced by movement on a west-northwest section of the Peel-Manning Fault System. Serpentinite structures suggest the west-northwest section initially underwent dextral strike-slip, which reoriented the northeast-oriented section, and subsequently sinistral strike-slip movement. Preliminary studies of serpentinites elsewhere around the periphery of the Hastings Block indicate localised effects due to readjustment of the block during its interaction with the Nambucca Block on its northern margin. The structures observed in the serpentinites are thought to have occurred during and after the Hunter-Bowen Orogeny and prior to stitching of the accretionary-subduction and forearc by the 228 Ma Werrikimbe Caldera. [ABSTRACT FROM AUTHOR]

Abstract: The Late Devonian subduction followed by the Early Carboniferous continental collision of the Saxothuringian and overriding upper-crustal Teplá–Barrandian units led to the growth of a large magmatic arc (the ∼354–337 Ma Central Bohemian Plutonic Complex) in the central part of the Bohemian Massif. Far-field tectonic forces resulting from the collision produced ∼WNW–ESE to ∼NW–SE regional shortening across the forearc upper crust above the subduction zone; the shortening was accommodated by predominantly top-to-the-ESE tectonic transport along the southeastern flank of the Teplá–Barrandian unit. Approaching the magmatic arc margin, the regional structural pattern changes and exhibits significant across- and along-strike variations interpreted as a result of strain partitioning, where the Saxothuringian/Teplá–Barrandian convergence interacted in different ways with the intruding magma pulses. Around the voluminous, northeasterly ∼354 Ma Sázava pluton the principal shortening was at high angle to the forearc-facing intrusive contact and the host rocks were significantly thermally softened. The regional top-to-the-ESE tectonic transport converted here into arc-parallel ductile flow within the structural aureole around and above the pluton. In contrast, a narrow to nonexistent ductile strain aureole is preserved in the host rocks around discordant sheet-like plutons (the southwesterly pre-354 (?) Ma Marginal granite and the Milín granodiorite of unknown radiometric age). Our AMS study of the Marginal granite and Milín granodiorite, and mapping of mesoscopic magmatic foliations and lineations in another neighboring sheet-like pluton (the ∼346 Ma Kozárovice granodiorite), reveals sigmoidal map-scale fabric patterns consistent with dextral transpression. We thus suggest that the thin sheet-like plutons were oriented obliquely to the principal shortening and were rheologically weaker than the host rocks prior to final crystallization, producing dextral transpression recorded by the internal fabrics of these plutons. Our study shows that the far-field plate kinematics during pluton emplacement is not the only factor that controls strain partitioning in continental magmatic arcs. The two contrasting styles of pluton emplacement documented here indicate that the pluton shape, orientation of intrusive contacts with respect to the background plate convergence vector, and heat budget of intrusions (magma volume, composition, and proportion of hot mantle component) may also govern strain partitioning. [Copyright &y& Elsevier]

The Plechý pluton, southwestern Bohemian Massif, represents a late-Variscan, complexly zoned intrusive center emplaced near the crustal-scale Pfahl shear zone; the pluton thus provides an opportunity to examine the interplay among successive emplacement of large magma batches, magmatic fabric acquisition, and the late-Variscan stress field associated with strike-slip shearing. The magmatic history of the pluton started with the emplacement of the porphyritic Plechý and Haidmühler granites. Based on gravity and structural data, we interpret that the Plechý and Haidmühler granites were emplaced as a deeply rooted, ∼NE–SW elongated body; its gross shape and internal fabric (steep ∼NE–SW magmatic foliation) may have been controlled by the late-Variscan stress field. The steep magmatic foliation changes into flat-lying foliation (particularly recorded by AMS) presumably as a result of divergent flow. Magnetic lineations correspond to a sub-horizontal ∼NE–SW finite stretch associated with the divergent flow. Subsequently, the Třístoličník granite, characterized by steep margin-parallel magmatic foliation, was emplaced as a crescent-shaped body in the central part of the pluton. The otherwise inward-younging intrusive sequence was completed by the emplacement of the outermost and the most evolved garnet-bearing granite (the Marginal granite) along the southeastern margin of the pluton. [ABSTRACT FROM AUTHOR]

Geophysical investigations reveal that many granitoid plutons possess a tabular shape: either laccolithic, lopolithic or phacolithic. In this study, the results of a centrifuge experiment are used to understand the formation mechanisms of these features. The model was build of a sequence of 14 differently coloured plasticine layers. Two buoyant layers - with a volume of c. 40 cm³ each - were incorporated into the model stratigraphy at different depths to investigate, whether the rise and emplacement of buoyant material at different levels results in different intrusion structures. After centrifuging for 30 mm at 700 G, both the buoyant layers had formed two lenticular sills (phacoliths) with aspect ratios (length/thickness) of 6 and 3.4 for the upper and lower phacoliths, respectively, directly above both pre-existing perturbations in the buoyant layers. During their movement, the buoyant phacoliths had pushed their roof plasticine upward. Simultaneously, their floor plasticine had subsided (bottom sinking). Subsidence of the floor material had choked the inflow of further buoyant material into the feeder channel of the developing sills and inhibited their further lateral growth. The observed forced downward movement of the plasticine floor of the forming PDMS (polydimethylsiloxane) phacoliths resembles the so-called "floor depression" of host rock material around an emplacing tabular pluton. Floor depression is supposed to be a very important vertical material transfer process, which provides space for the construction of lopo- and phacoliths. The subsidence of host material made space for the developing buoyant phacoliths, but also restricted their growth to a certain time slot before the influx of new buoyant material into the feeder dyke of the tabular intrusive body was shut off. Similarly, in nature, the growth of a tabular pluton might be limited not only by the rate of magma ascent and its physical properties, but also by the emplacement processes of the evolving pluton. [ABSTRACT FROM AUTHOR]

Abstract: Lava flows with preserved bases and brecciated upper crusts constitute a morphological type that differs in character from typical pahoehoe and a''a: such flows have been reported from many provinces around the world. Previous studies had referred to these flows informally as ‘pahoehoe flows with rubbly tops’, ‘broken-top pahoehoe’ and ‘rubbly pahoehoe’. Recent studies have formally applied the latter term to describe parts of the well-studied Laki flow in Iceland as well as flows from the Columbia River Basalt province. Rubbly pahoehoe flows are abundant in the upper stratigraphic formations of the Deccan Volcanic Province (DVP), and are more commonly known as simple flows. This study presents detailed observations of such flows from various parts of the DVP and discusses their implications for understanding flow emplacement. These flows, which appear to be single units at the outcrop-scale, are generally much thicker and significantly more extensive than individual pahoehoe lobes that dominate the lower formations of the Deccan stratigraphy. They are characterised by preserved, gently undulating tachylitic bases but variably disrupted crustal zones that grade into flow-top breccias. The breccias are constituted of highly vesicular and oxidised fragments of varying sizes that appear to have been derived from previously formed pahoehoe crusts. Previous work has indicated that the morphology of these flows might be related to initial inflation, accompanied by rapid volatile exsolution and an increase in effusion rate and/or viscosity with time. This agrees reasonably well with the qualitative and quantitative models of emplacement developed for the Laki flow. The abundance of such flows in the upper formations of the Deccan stratigraphy clearly hints at a significant shift in the nature of the Deccan eruptions; this could be indicative of higher eruption rates during this period. This, in turn, raises the possibility of hazardous impact on the climate during the eruption of these flows, which is also discussed in the paper. [Copyright &y& Elsevier]

Abstract: Chimborazo is a Late Pleistocene to Holocene stratovolcano located at the southwest end of the main Ecuadorian volcanic arc. It experienced a large sector collapse and debris avalanche (DA) of the initial edifice (CH-I). This left a 4 km wide scar, removing 8.0±0.5 km3 of the edifice. The debris avalanche deposit (DAD) is abundantly exposed throughout the Riobamba Basin to the Río Chambo, more than 35 km southeast of the volcano. The DAD averages a thickness of 40 m, covers about 280 km2, and has a volume of >11 km3. Two main DAD facies are recognized: block and mixed facies. The block facies is derived predominantly from edifice lava and forms >80 vol.% of the DAD, with a probable volume increase of 15–25 vol.%. The mixed facies was essentially created by mixing brecciated edifice rock with substratum and is found mainly in distal and marginal areas. The DAD has clear surface ridges and hummocks, and internal structures such as jigsaw cracks, injections, and shear-zone features are widespread. Structures such as stretched blocks along the base contact indicate high basal shear. Substratum incorporation is directly observed at the base and is inferred from the presence of substratum-derived material in the DAD body. Based on the facies and structural interpretation, we propose an emplacement model of a lava-rich avalanche strongly cataclased before and/or during failure initiation. The flow mobilises and incorporates significant substrata (10–14 vol.%) while developing a fine lubricating basal layer. The substrata-dominated mixed facies is transported to the DAD interior and top in dykes invading previously-formed fractures. [Copyright &y& Elsevier]

Abstract: Conical sandstone intrusions with a geometry comparable with that of many igneous sills have been identified using 3D seismic data from large areas of the North Sea and Faeroe–Shetland Basins. These intrusions are of reservoir scale, ranging from 100 to 2000m or so in diameter, 50–300m in height, and 1–80m in thickness (aperture). They are concentrated in specific stratigraphic intervals in the Cenozoic fills of both basins. Two geometrical end members are recognised and defined here: ‘apical cones’ and ‘flat-based bowls’. The former consist of inward dipping conical inclined sheets meeting at a prominent apex and the latter of similarly dipping discordant margins climbing from the edges of a concordant sheet. Both end members are associated with domal folds that are interpreted as resulting from the hydraulic elevation of the overburden during intrusion, and which are analogous to similar structures associated with bowl-shaped igneous sills. Measurements of aperture (ω) versus distance exhibit systematic relationships with the structural relief of these folds, offering a potentially predictive method for estimation of sandstone intrusion aperture and reservoir volume prior to drilling. A growth model for these end-member geometries is presented, drawing on existing theory for igneous sill emplacement. Aperture versus distance plots (ω –X) are used to illustrate two contrasting models for aperture inflation during propagation, but these require much further data before any specific growth model can be adopted. [Copyright &y& Elsevier]

Abstract: The Pimenta Bueno kimberlite field of Rondônia State, Brazil is located near the edge of the Amazon Craton and contains more than thirty bodies. A late to mid-Triassic emplacement age has been obtained for two kimberlites. The Pimenta Bueno kimberlite field includes pipes of up to 15 ha and a few apparently flat-lying hypabyssal kimberlite sills. In the three pipes and one sill examined, three textural end member types of kimberlite are recognized: hypabyssal kimberlite (HK), tuffisitic kimberlite (TK), and resedimented volcaniclastic kimberlite (RVK). There are gradations in textures between the three types. The overall gradation with depth is VKB, VK, TK, TKt, HKt to HK (where “t” denotes transitional varieties), and the textural gradations are apparent at all scales, megascopically to microscopically. Importantly, these gradations appear to occur within single phases of kimberlite. TK and the associated transitional varieties observed in the Pimenta Bueno field have striking similarities to those of many kimberlites of southern Africa and Canada. The Pimenta Bueno kimberlite field thus represents a newly recognized example of southern-African-style kimberlite pipes occurring on a third continent. The TK-bearing pipes of Pimenta Bueno, southern Africa, and Canada are markedly different from those found in the Canadian Prairies and Lac de Gras, Northwest Territories, which indicates that pipes containing TK and related textures are repeated in space and time but only form in certain circumstances. There is an apparent correlation between kimberlite texture and pipe size. In the larger pipes (>5 ha), the TK is overlain by VKB. In the small pipes (<3 ha) there is a textural gradation with depth from TK to HK and VKB is not present. One TKt–HKt transition appears to be ~60 m thick. The nature of the TK–TKt–HKt–HK textural transition suggests that TK developed by the textural modification of magmatic kimberlite within the pipe. The textures may reflect increased degrees of magma disruption associated with volatile exsolution. [Copyright &y& Elsevier]

Abstract: The Cretaceous Fort à la Corne (FALC) kimberlite field was active over a time span of ~20 Ma with contemporaneous terrestrial (Mannville Group) to marine (Lower Colorado Group) background sedimentation. Steep-sided pipes, craters and positive landform volcanoes such as scoria or tuff cones are thought to have formed during that period. The 147 Kimberlite is located in the SE section of the field''s main cluster and is part of the large (~377.5 ha) Orion North volcanic complex. Based on logging of 25 drill cores, the morphology of the country rock/kimberlite interface suggests excavation of a complex crater field down to the upper portion of the Mannville Group sedimentary deposits. At least two types of volcaniclastic deposits are identified: a main kimberlite unit that is typically characterized by crustal xenolith-poor (1–2%), normal graded beds possibly deposited as turbidites in a subaqueous environment, originating from the nearby 148 tephra cone and infilling the adjacent 147 crater, and a second unit, located on the NE margin of the 147 Kimberlite, that represents a thick (~60 m) sequence of large (up to 22 m) sedimentary country rock blocks located at least 60 m above their original stratigraphic position. We suggest the following time sequence of events: Crater excavation as a consequence of a shallow magma fragmentation level within the uppermost country rock sequences, together with several closely spaced eruptive centres initially formed the complex, intercalated crater field. Subsequently, ongoing eruptions with a fragmentation level above the country rock produced the lithic fragment poor main infill of the 148 Kimberlite. Resedimentation from the outer flanks of the 148 tephra cone resulted in the deposition of turbidites in the 147 area. A consolidation phase solidified the lowermost portion of the main infill in 147. A subsequent explosion(s) occurred within the Mannville Group in the 147 area, ejecting large blocks of sedimentary country rocks and fracturing the overlying volcaniclastic main infill. Finally, blocks of the main infill tilted and possibly slumped into the subsidence structure developed above the emptied explosion chamber of 147. The different volcanic deposits reflect a change in eruption style and fragmentation level from highly explosive to spatter activity with little fragmentation potential. Cap rocks to build up the volatile overpressure necessary to blast the craters were not present at the time of emplacement. No diatremes were observed in the study area. Assuming that the magma properties remained constant over time, the change in eruption style has to be attributed to external factors, such as water access to the rising magma. The volcanic behaviour of the kimberlite magma appears to be comparable to that of other magmatic systems, both in eruptive style and production rate. No evidence was found for a high, possibly Plinian production rate or dispersion. [Copyright &y& Elsevier]

Abstract: Class 1 kimberlites are distinct from Class 2 and Class 3, in that they are characterized by three zones, namely; root, diatreme and crater. Class 2 and 3 kimberlites do not form diatreme zones filled with diatreme-facies rocks. Consequently these kimberlites probably form by different processes. Within the root zones of Class 1 kimberlites, subvolcanic contact breccias occur at particular horizons within the immediate wall rocks. These could be formed by hydraulic fracturing caused by crystallization-induced exsolution of juvenile volatiles within the cooling hypabyssal kimberlite. This exsolution may subsequently also lead to the formation of transitional-facies kimberlites in the uppermost parts of extended columns or plugs of hypabyssal kimberlite. From such settings, break through to surface and explosive eruption is thought to occur and pipes having characteristic diatremes slope angles of 82° and 500–700 m deep craters are formed. Through these processes these kimberlites undergo fundamental textural changes to produce a variety of rocks from hypabyssal-, through transitional-, to diatreme- and crater-facies kimberlites. [Copyright &y& Elsevier]

Abstract: The rock type “Tuffisitic Kimberlite” (TK) occurs in the deeper diatremes of some Southern African, Canadian and Siberian kimberlite pipes and has been considered a unique rock type related to a particular emplacement process. The key features of this rock type are its fragmental nature, its massive, well-mixed appearance and a specific matrix mineralogy characterized by the presence of serpentine and microlitic clinopyroxene and the absence or scarcity of carbonate. Historically, all these features were thought to be related to a highly specific intrusive–extrusive magmatic emplacement process. In this process, the expansion of magmatic volatiles drives the fluidization of a pre-existing, shallow-crustal, vertical magma reservoir (the “embryonic pipe”) and its consequent evolution into the final diatreme after breakthrough to the surface. The specific matrix mineralization is explained by the dissociation of carbonate into CO2 and CaO. While the expanding CO2 drives the fluidization process, CaO reacts with SiO2 released from xenolith and olivine alteration to form microlitic clinopyroxene. With the phreatomagmatic process chain we offer an alternative model that can readily explain this specific rock type. Ongoing explosions in a downward penetrating root zone excavate a pipe consisting of a rather regular, cone-shaped diatreme underlain by the irregular root zone. At this stage the pipe in its majority is infilled by warm to hot pyroclastic tephra. During thermohydraulic explosions in the root zone the expansion of water vapor homogenizes the overlying diatreme tephra and mixes it with the adjacent country-rock lithologies. This result in the massive, well-mixed volcaniclastic rock type typical for TKBs. Post-emplacement hydrothermal alteration and mineralization under epi- to mesothermal conditions are considered responsible for the observed specific matrix mineralogy. Carbonate is frequently present in coherent root zone rocks but is rare or absent due to its dissolution in hot hydrothermal fluids ascending from the lower diatreme, which in turn precipitate their dissolved carbonate higher up in the cooler, bedded upper diatreme region. Clinopyroxene also grows under epi- to mesothermal conditions. For the crystallization of serpentine a X(H2O):X(CO2) ratio of 20:1 is required, which suggests both a high availability of groundwater and a low abundance of CO2 after and likely during emplacement. Isotope studies (H, C, O, Sr) of matrix minerals suggest participation of groundwater in the formation of these minerals. [Copyright &y& Elsevier]

Abstract: In Canada more than 770 kimberlites have erupted in diverse tectonic settings over a period of 1000 Ma and over an area at least 5000 km across. The kimberlites represent at least 30 comagmatic fields. One pipe type dominates each of the different kimberlite fields. Even with the discovery of a significant number of new kimberlite fields, this review of recent data substantiates the previous proposal that there are at least three distinct classes of kimberlite pipes which show a correlation with the nature of the country rocks into which they were emplaced. New data show that a variation on the Prairies pipe type occurs when kimberlites were emplaced into competent Paleozoic sediments resulting in steeper-sided pipes infilled with similar pyroclastic kimberlite. New data for each pipe type are summarised and the contrasting characteristics of the three pipe types are considered to reflect fundamentally different styles of eruption and deposition. Apparently uniform, near-surface, olivine- and volatile-rich kimberlite magmas were modified differently during the contrasting emplacement processes resulting in distinct textural rock types, pyroclastic kimberlite (PK), tuffisitic kimberlite (TK) and associated hypabyssal kimberlite (HK) or resedimented kimberlite (RVK) dominating each type of pipe. The substantiated correlation of pipe type with country rock geology could indicate variable constraints on volatile exsolution which affected the nature of the magmatic eruptions in different settings. [Copyright &y& Elsevier]

This essay enquires how certain performative mechanisms deployed in the practice-as-research project Homing Place might be conceived as homing devices, mechanisms that create relational and dialogic interspaces of orientation, dwelling, and emplacement and methods of bodily attunement to places. How might they be a homing place or homing places - describing both a place of inhabitation that exists in and through movement and a method of action, a way of finding, making and inhabiting that place? In Homing Place, a set of contextually based and participant-led experiments involved inhabitants of Plymouth, UK, who are asylum seekers and refugees, in spatial, relational and dialogic art processes of wayfinding, mapping and walking. This essay considers the underlying conceptual concerns of this project - how do those performative mechanisms employed create place or are place-making, and how is emplacement performed? Key conceptual tools for this discussion are Tim Ingold's conceptions of wayfaring and inhabitant knowledge and Edward Casey's conceptions of dwelling and inhabitation. [ABSTRACT FROM AUTHOR]

The Aguablanca stock is a Variscan mafic pluton located in the Ossa-Morena zone, southern Iberian Massif, hosting an unusual Ni-Cu-PGE mineralization associated with magmatic breccia pipes which intruded its northern part. The emplacement of the Aguablanca stock and the mineralized breccia pipes are related to the activity of the Cherneca ductile shear zone, a Variscan sinistral shear zone that favoured magma ascent through the upper crust. A detailed gravity study has been carried out in order to investigate the 3D geometry of the Aguablanca intrusion and to get insights about the emplacement mechanism and tectonic controls of the mineralization. The three-dimensional gravity modelling shows that the stock has an inverted drop geometry with a feeder zone in contact with the Cherneca ductile shear zone. The inferred orientation of the feeder zone suggests that the emplacement probably took place along an open tensional crack formed within the strain field of the adjacent Cherneca ductile shear zone. The modelling of the breccia pipes hosting the Ni-Cu-PGE ore shows that they are included inside the feeder zone, thus their emplacement is probably controlled by successive opening events of this tensional crack. [ABSTRACT FROM AUTHOR]

Portnov B. A. and Schwartz M. On the relativity of urban location, Regional Studies. The effect of location attributes (e.g., topography, proximity to networks, etc.) depends on how much they stand out in their regional or national contexts. In a region or country where a given advantage or disadvantage are commonplace, they are likely to have lesser effects than where they are uncommon. Thus, cold and rainy places may repel would-be residents in countries or regions offering sunnier alternatives, but might not deter them if such alternatives are absent. Location advantage is thus a relative notion: it might matter regionally and nationally more than internationally... [ABSTRACT FROM AUTHOR]

Abstract: Ophiolites are key features for unravelling the geologic history of orogenic belts, especially in China, which was formed by amalgamation of numerous tectonic blocks from Precambrian time to the present. Although much has been learned about ophiolites over the last 30 years, questions remain as to their definition, composition, classification, origin and tectonic significance. Most ophiolites, particularly those in China are incomplete bodies composed of serpentinized peridotite, minor cumulate rocks and sparse pillow lavas. Sheeted dikes are rare in most ophiolites and the structural relationships between the different lithologies are commonly unclear. Such bodies should be considered ‘possible’ ophiolites unless the lithologies can be clearly linked structurally or compositionally. The former classifications of ophiolites into Cordilleran- or Tethyan-types and Harzburgite- or Lherzolite-types have been superseded by a more process-oriented classification proposed by Dilek (2003) that relates them to different magmatic and tectonic processes. This classification makes it easier to reconstruct paleoenvironments and processes in the geologic record. Although ophiolites were originally interpreted as fragments of normal ocean lithosphere, most such bodies have been shown to contain clear suprasubduction zone geochemical fingerprints. Some ophiolites consist entirely of suprasubduction zone components whereas others are compound bodies formed originally at mid-ocean spreading centers and then modified by later suprasubduction zone melts. Percolation of suprasubduction zone melts through the overlying mantle wedge can produce dunite pods and dikes, commonly associated with podiform chromitites, and may be responsible for the formation of transitional zone dunites. Ophiolite emplacement is thought to require subduction of lower density material beneath the body, a process that is easy to explain in subduction zone environments. Emplacement can occur either during subduction rollback or by final closure of the ocean basin in which the ophiolite formed. Much new work on Chinese ophiolites is currently underway and new interpretations of these bodies are being developed. This Special Issue presents the results of recent studies of ophiolites from most of the major orogenic belts in China. [Copyright &y& Elsevier]

Abstract: The recent experimental work by Kavanagh et al. [Kavanagh, J.L., Menand, T. and Sparks, R.S.J. (2006). An experimental investigation of sill formation and propagation in layered elastic media. Earth Planet. Sci. Lett. 245, 799–813.] shows that lithological discontinuities and rigidity contrasts can control the formation and dynamics of sills at interfaces separating upper, rigid strata from lower, weaker strata. The present paper extends this work and focuses on its implications in terms of the length- and time-scales associated with the development of laccoliths and other igneous complexes. Sill formation controlled by rigidity contrasts is shown to provide a growth mechanism for laccoliths. The formation of a sill provides favourable rigidity anisotropy for the emplacement of subsequent sills so that laccoliths grow by over-accretion, under-accretion or even mid-accretion of successive sills. In accord with field data, this model predicts that laccoliths grow mainly by vertical expansion, representing the cumulative thickness of their internal sills, while maintaining a comparatively constant lateral extend. The model also predicts that the time-scale over which laccoliths form is essentially determined by the cumulative time between successive sill intrusions. Also, sill dynamics are controlled by viscous dissipation of the fluid along their length, which have consequences for the size and shape of sills. Viscously-controlled dynamics would enable sills to propagate further and thus to grow thicker than dykes of similar magmas. These dynamics would also enable sills to propagate faster and thus to induce non-elastic deformations in surrounding rocks that could deviate them from the interface they originally follow. This would allow them to feed new sills along other interfaces and could assist in the formation of the step structures and saucer-shapes that are commonly observed in sill complexes. [Copyright &y& Elsevier]

The Mount Whitney Intrusive Suite is a nested intrusion composed of three granitic plutons that were emplaced along the eastern margin of the Sierra Nevada batholith between 88 and 83 Ma. Geologic relations indicate the suite was formed by magmas that spread laterally at a depth of ~10 km after initially rising along fractures developed at an extensional stepover between the proto--Kern Canyon fault and the Sierra Crest shear zone. Cenozoic uplift and erosion have exposed the interior of the suite, making it possible to study textural and compositional variations within the body that yield insights into the complementary roles of source variability and crystal fractionation in producing zoned intrusions. Although isotopic data indicate that contributions to the Mount Whitney Intrusive Suite from preexisting crustal rocks increased over time, major differences in the compositional and textural zoning of its members also reflect gradual warming of the upper crust. The oldest pluton is isotopically and compositionally diverse, and consists of distinct phases that apparently underwent limited mixing and fractionation following their emplacement into cool host rocks. Conversely, the younger members are more isotopically uniform, and the youngest displays regular pluton-scale variations in composition and texture consistent with individual inputs having mixed, fractionated, and undergone textural coarsening as it cooled slowly within the older members or wall rocks warmed by them. A thermal model of the suite indicates that the intervals during which successive magma inputs were likely to hybridize and undergo subsequent in situ differentiation increased as the intrusion grew. For recharge at an interval intermediate between those required for 50% crystallization in different parts of the suite, model results suggest that the outer part would have developed as a composite body in which individual phases underwent limited differentiation, whereas the inner part would have developed as a more homogeneous body capable of large-scale differentiation. These predictions match trends among the suite's members and suggest that warming of the upper crust may account for much of its textural and compositional diversity. Local differentiation also occurred in the upper parts of the younger members, where rhyolitic melts were segregated as a result of solidification front instability. [ABSTRACT FROM AUTHOR]

This article is about the changing meaning of home among people engaged in the Guatemalan guerrilla movement. It shows that during the war, the revolutionary committed struggled for home more in terms of communal spheres of insurgent societal transformation than in terms of the defense or reconstruction of family or house. Though the counterinsurgency state was bent on their annihilation, it was only with the implementation of liberal peace that their commitment was ultimately destroyed. Most of them then opted for 'return' to their pre-war settlements and they gave up the political project of preserving their progressive civil organization. 'Home' under liberal peace in post-revolutionary Central America is continuously held together mainly by the migration of youth in search of opportunities elsewhere as hope for improved living conditions has become a question no longer of transforming but of leaving society in order to save oneself and/or one's household. The notion of liberal emplacement is brought forward in this article to conceptualize the destruction of political movement through the creation of an individualized necessity of spatial movement. [ABSTRACT FROM AUTHOR]