A geochemical drainage survey of the Fleet granitic complex and its environs

A regional geochemical drainage reconnaissance programme was undertaken over 900 km2 of south-west Scotland centred on the Fleet granitic complex. Rocks of Ordovician and Silurian age outcrop over the area, into which have been intruded the Fleet and Loch Doon plutons. Multi-element analysis of stream sediments and heavy mineral concentrates shows a number of patterns of trace element distribution related to different lithologies and to mineralisation. Broad scale patterns exhibited by some elements denote compositional variations within the Lower Palaeozoic sediments and within the Fleet and Loch Doon plutons. On thebasis of the drainage data the sedimentary rocks have been divided into eight distinct geochemical units each characterised by different element distribution patterns. The Fleet and Loch Doon plutons have been sub-divided on the same basis. Follow-up investigations of drainage anomalies led to the discovery of both structure-controlled and disseminated base metal mineralisation in the Penkiln drainage basin within the salthernaureole of the Loch Doon granite. The distribution of Cu, F’b and Zn to the south and south-west of the Fleet granite suggests a zonation of vein minerahsation, with Cu prominent adjacent to the granite contact and F’b and Zn having a wider dispersion away from the granite. Other anomalies delineate a mineralised lineament that follows the regional strike of the Lower Palaeozoic sediments, southeast of the Fleet granite

A reconnaissance geochemical drainage survey of the Criffel-Dalbeattie granodiorite complex and its environs

Regional geochemical reconnaissance by stream sediments and panned concentrates was undertaken over an area of 850 km 2 of south-west Scotland. Rocks of Ordovician to Permian age are exposed within the area but the major part is occupied by the Criffel-Dalbeattie granodiorite complex. Multi-element analysis of the samples collected demonstrates patterns of trace element distribution related to the geology and Broad-scale patterns in the distribution of some elements reflect compositional anumber of mineralisation. variations in both the Lower Palaeozoic turbidite sequence and the Criffel- Dalbeattie granodiorite complex, both of which may be sub-divided into specific units on the basis of the geochemical data. The follow-up of copper anomalies in drainage samples from the Black Stockarton Moor area led to the discovery of porphyry-style copper mineralisation within an arcuate belt at least 5 km by 1 km within the Black Stockarton Moor subvolcanic complex and of related disseminated copper mineralisation at Screel Burn. The area to the west of the Criffel-Dalbeattie plutonic complex is also characterised by relatively high boron levels in stream sediments reflecting the widespread occurrence of tourmaline both in association with and peripheral to the copper mineralisation. Vein mineralisation, usually containing baryte in addition to base.metals, is also identifiable from the drainage survey at the eastern margin of the Criffel-Dalbeattie granodiorite; in association with the Lower Carboniferous rocks along the Solway coast; and within the Lower Palaeozoic turbidites in the west of the area

Physics of Solar Prominences: II - Magnetic Structure and Dynamics

Observations and models of solar prominences are reviewed. We focus on non-eruptive prominences, and describe recent progress in four areas of prominence research: (1) magnetic structure deduced from observations and models, (2) the dynamics of prominence plasmas (formation and flows), (3) Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and large-scale patterns of the filament channels in which prominences are located. Finally, several outstanding issues in prominence research are discussed, along with observations and models required to resolve them.Comment: 75 pages, 31 pictures, review pape

Fractal Reconnection in Solar and Stellar Environments

Recent space based observations of the Sun revealed that magnetic reconnection is ubiquitous in the solar atmosphere, ranging from small scale reconnection (observed as nanoflares) to large scale one (observed as long duration flares or giant arcades). Often the magnetic reconnection events are associated with mass ejections or jets, which seem to be closely related to multiple plasmoid ejections from fractal current sheet. The bursty radio and hard X-ray emissions from flares also suggest the fractal reconnection and associated particle acceleration. We shall discuss recent observations and theories related to the plasmoid-induced-reconnection and the fractal reconnection in solar flares, and their implication to reconnection physics and particle acceleration. Recent findings of many superflares on solar type stars that has extended the applicability of the fractal reconnection model of solar flares to much a wider parameter space suitable for stellar flares are also discussed.Comment: Invited chapter to appear in "Magnetic Reconnection: Concepts and Applications", Springer-Verlag, W. D. Gonzalez and E. N. Parker, eds. (2016), 33 pages, 18 figure

The Science of Sungrazers, Sunskirters, and Other Near-Sun Comets

This review addresses our current understanding of comets that venture close to the Sun, and are hence exposed to much more extreme conditions than comets that are typically studied from Earth. The extreme solar heating and plasma environments that these objects encounter change many aspects of their behaviour, thus yielding valuable information on both the comets themselves that complements other data we have on primitive solar system bodies, as well as on the near-solar environment which they traverse. We propose clear definitions for these comets: We use the term near-Sun comets to encompass all objects that pass sunward of the perihelion distance of planet Mercury (0.307 AU). Sunskirters are defined as objects that pass within 33 solar radii of the Sun’s centre, equal to half of Mercury’s perihelion distance, and the commonly-used phrase sungrazers to be objects that reach perihelion within 3.45 solar radii, i.e. the fluid Roche limit. Finally, comets with orbits that intersect the solar photosphere are termed sundivers. We summarize past studies of these objects, as well as the instruments and facilities used to study them, including space-based platforms that have led to a recent revolution in the quantity and quality of relevant observations. Relevant comet populations are described, including the Kreutz, Marsden, Kracht, and Meyer groups, near-Sun asteroids, and a brief discussion of their origins. The importance of light curves and the clues they provide on cometary composition are emphasized, together with what information has been gleaned about nucleus parameters, including the sizes and masses of objects and their families, and their tensile strengths. The physical processes occurring at these objects are considered in some detail, including the disruption of nuclei, sublimation, and ionisation, and we consider the mass, momentum, and energy loss of comets in the corona and those that venture to lower altitudes. The different components of comae and tails are described, including dust, neutral and ionised gases, their chemical reactions, and their contributions to the near-Sun environment. Comet-solar wind interactions are discussed, including the use of comets as probes of solar wind and coronal conditions in their vicinities. We address the relevance of work on comets near the Sun to similar objects orbiting other stars, and conclude with a discussion of future directions for the field and the planned ground- and space-based facilities that will allow us to address those science topics

Fenites associated with carbonatite complexes : a review

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.Carbonatites and alkaline-silicate rocks are the most important sources of rare earth elements (REE) and niobium (Nb), both of which are metals imperative to technological advancement and associated with high risks of supply interruption. Cooling and crystallizing carbonatitic and alkaline melts expel multiple pulses of alkali-rich aqueous fluids which metasomatize the surrounding country rocks, forming fenites during a process called fenitization. These alkalis and volatiles are original constituents of the magma that are not recorded in the carbonatite rock, and therefore fenites should not be dismissed during the description of a carbonatite system. This paper reviews the existing literature, focusing on 17 worldwide carbonatite complexes whose attributes are used to discuss the main features and processes of fenitization. Although many attempts have been made in the literature to categorize and name fenites, it is recommended that the IUGS metamorphic nomenclature be used to describe predominant mineralogy and textures. Complexing anions greatly enhance the solubility of REE and Nb in these fenitizing fluids, mobilizing them into the surrounding country rock, and precipitating REE- and Nb-enriched micro-mineral assemblages. As such, fenites have significant potential to be used as an exploration tool to find mineralized intrusions in a similar way alteration patterns are used in other ore systems, such as porphyry copper deposits. Strong trends have been identified between the presence of more complex veining textures, mineralogy and brecciation in fenites with intermediate stage Nb-enriched and later stage REE enriched magmas. However, compiling this evidence has also highlighted large gaps in the literature relating to fenitization. These need to be addressed before fenite can be used as a comprehensive and effective exploration tool.This research has received funding from the European Union’s Horizon 2020 research and innovation programme under grant No 689909

Petrogenesis and geochemical halos of the amphibolite facies, Lower Proterozoic, Kerry Road volcanogenic massive sulfide deposit, Loch Maree Group, Gairloch, NW Scotland

The Palaeoproterozoic Kerry Road deposit is one of the oldest examples of volcanogenic massive sulfide (VMS) mineralization. This small VMS deposit (~500,000 tons grading at 1.2% Cu, 3.5% Zn) is hosted in amphibolite facies mafic-siliciclastic units of the c. 2.0 Ga Loch Maree Group, Scotland. Sulfide mineralization consists of pyrite and pyrrhotite with subordinate chalcopyrite and sphalerite, occurring in disseminated, vein and semi-massive to massive textures. The deposit was highly deformed and metamorphosed during the c. 1.8–1.7 Ga Laxfordian Orogeny. Textural relationships of deformed sulfide minerals, related to early Laxfordian deformation (D1/D2), indicate initial high pressure-low temperature (100 MPa, 150 °C) conditions before reaching peak amphibolite facies metamorphism, as evident from pyrrhotite crossing the brittle/ductile transition prior to chalcopyrite. Late Laxfordian deformation (D3/D4) is marked by local retrograde greenschist facies at low pressure and temperature (<1.2 MPa, <200 °C), recorded by late red sphalerite remobilization. δ34S values from all sulfide minerals have a homogeneous mean of 0.8 ± 0.7‰ (n = 21), consistent with interaction of hydrothermal fluids in the host oceanic basalt-island arc setting envisaged for deposition of the Loch Maree Group. Microprobe analyses of amphiboles record evidence of the original alteration halo associated with the Kerry Road deposit, with a systematic Mg- and Si- enrichment from ferrotschermakite (~150 m) to Mg-hornblende (~90 m) to actinolite (0 m) on approach to the VMS deposit. Furthermore, whole rock geochemistry records a progressive enrichment in Si, Cu, Co, and S, and depletion in Al, Ti, V, Cr, Y and Zr with proximity to the VMS system. These elemental trends, together with amphibole geochemistry, are potentially useful exploration vectors to VMS mineralization in the Loch Maree Group, and in similar highly deformed and metamorphosed terranes elsewhere