Geochemical and Isotopic Evolution of Loihi Volcano, Hawaii

The Publishers wish to apologise for the incorrect representationof figure 10 which accompanied this paper. The correct figureis reproduced below.     

Volatiles in pillow rim glasses from Loihi and Kilauea volcanoes,Hawaii

Volatiles and major elements in submarine glasses from Loihi seamount and Kilauea volcano. Hawaii were analyzed by high temperature mass spectrometry and the electron microprobe. Loihi glasses are subdivided into three groups: tholeiitic, transitional and alkali basalts. The glasses are evolved: Mg numbers range from 48–58. The alkalic lavas are the most evolved.Total volatiles range from 0.73 to 1.40 wt.%. H₂O shows a positive linear correlation with K₂O content [H₂O = 0.83 (± .09) K₂O + 0.08 (± .06)]. Concentrations of H₂O are higher in the alkalic lavas, but Cl and F abundances are highly variable. Variations in ratios of incompatible elements (K₂O, P₂O₅, H₂O) indicate that each group was derived from a distinct source. CO₂ contents range from 0.05 to 0.19 wt.% but show no systematic correlation with rock type or Mg #. A well-defined decrease in glass CO₂ content with increasing vesicularity is shown by the alkalic lavas. CO₂ may have been outgassed from the tholeiitic and transitional magmas prior to eruption during storage in a shallow magma chamber. Reduced carbon species (CO and CH₄) were found in small amounts in most of the alkalic samples. Although the redox histories of Hawaiian lavas are poorly known, these new data indicate the presence of a reduced source for Loihi magmas.The Kilauea tholeiitic glasses are evolved (Mg # 48.3 to 55) and have higher H₂O contents (av. 0.54 wt.%) than Loihi tholeiites (av. 0.42 wt.%) at the same Mg # (~55). Cl is distinctly lower in Kilauea glasses (0.01 wt.%) compared to Loihi glasses (0.09 wt.%). The data indicate significant source differences for the two volcanoes, consistent with results of other geochemical studies.Loihi tholeiites have distinctly higher ³He/⁴He ratios than Kilauea tholeiites and are the highest measured in submarine basalts (KURZ et al., 1983). These high ratios have been used to invoke a primitive source for Loihi basalts. The high Cl content of these basalts, the highest we have ever measured in submarine basalts, may be a fingerprint of this primitive source, as previously noted for Icelandic basalts (Schillinget al. 1980).     

Energy release in solar flares

Team 2 of the Ottawa FLARES 22 Workshop dealt with observational and theoretical aspects of the characteristics and processes of energy release in flares. Main results summarized in this article stress the global character of the flaring phenomenon in active regions, the importance of discontinuities in magnetic connectivity, the role of field-aligned currents in free energy storage, and the fragmentation of energy release in time and space.Report of Team 2, Flares 22 Workshop, Ottawa, May 25–28, 1993.     

The use of GPR for characterizing underground weathered profiles in the sub-humid tropics

Ground penetrating radar (GPR) has been used as a tool to access information about ground subsurface features. Such information is very important for different types of studies, varying from those related to archeological research to those studying geological elements of bedrock. More recently, however, GPR has been increasingly applied to environmental studies, especially for soil research. This paper presents the results of an application of GPR for the study of weathered profiles. GPR was used to discover the degree of trustworthiness of the information on the ground subsurface through the interpretation of the results of the radar sections as well as the data collected from boreholes, which reached until 21 m. The results show a relatively high degree of details obtained by GPR, indicating the possibility of speeding up ground subsurface surveys related to geomorphological, geological, and pedological studies.     

Asteroseismology and interferometry

Asteroseismology provides us with a unique opportunity to improve our understanding of stellar structure and evolution. Recent developments, including the first systematic studies of solar-like pulsators, have boosted the impact of this field of research within astrophysics and have led to a significant increase in the size of the research community. In the present paper we start by reviewing the basic observational and theoretical properties of classical and solar-like pulsators and present results from some of the most recent and outstanding studies of these stars. We centre our review on those classes of pulsators for which interferometric studies are expected to provide a significant input. We discuss current limitations to asteroseismic studies, including difficulties in mode identification and in the accurate determination of global parameters of pulsating stars, and, after a brief review of those aspects of interferometry that are most relevant in this context, anticipate how interferometric observations may contribute to overcome these limitations. Moreover, we present results of recent pilot studies of pulsating stars involving both asteroseismic and interferometric constraints and look into the future, summarizing ongoing efforts concerning the development of future instruments and satellite missions which are expected to have an impact in this field of research.     

The solar flares of February 1986 and the ensuing intense geomagnetic storm

A very intense geomagnetic storm, the largest observed in 26 years, was observed in early February 1986 having just been preceded by a series of six solar flares during the period 3–7 February. The storm and its antecedent flares are currently a subject of great interest because of the unusually large magnitude of the various geomagnetic effects that obtained. The fact that the flares were moderate to large in soft X-ray intensity, but much smaller than the largest that the Sun is capable of producing, coupled with the fact that these events occurred near the minimum of the current solar activity cycle, adds to the uniqueness of the overall episode.This paper describes the special circumstances surrounding these events and offers an interpretation of the cause and effect relationships through a numerical simulation of the dynamical evolutionary processes that may have occurred in interplanetary space.     

Proton Enhancements and Their Relation to the X-Ray Flares During the Three Last Solar Cycles

Energetic proton measurements obtained from the GOES and IMP-8 satellites as well as from ground-based neutron monitors are compared with the GOES soft X-ray measurements of the associated solar flares for the period 1975–2003. The present study investigates a broad range of phenomenology relating proton events to flares (with some references to related interplanetary disturbances), including correlations of occurrence, intensities, durations and timing of both the particle event and the flare as well as the role of the heliographic location of the designated active region. 1144 proton events of > 10 MeV energy were selected from this 28-year period. Owing primarily to the low particle flux threshold employed more than half of this number was found to be reliably connected with an X-ray flare. The statistical analysis indicates that the probability and magnitude of the near-Earth proton enhancement depends critically on the flare's importance and its heliolongitude. In this study all flares of X-ray importance > X5 and located in the most propitious heliolongitude range, 15^∘W to 75^∘W, were succeeded by a detectable proton enhancement. It was also found that the heliolongitude frequently determines the character of the proton event time profile. In addition to intensity, duration and timing, proton events were found to be related to the other flare properties such as lower temperatures and longer loop lengths.     

Triassic metasedimentary successions across the boundary between the southern Apennines and the Calabrian Arc (northern Calabria,Italy)

The boundary area between the Apenninic fold‐and‐thrust belt and the crystalline Calabrian Arc, located around Sangineto in northern Calabria, has been investigated. New geological mapping in the Sant'Agata area has been performed on the Triassic successions traditionally attributed to the metasedimentary San Donato Unit. This, coupled with a reappraisal of the stratigraphy and tectonics of coeval successions present more to the south in the Cetraro Unit, results in a new reconstruction of the Triassic evolution of all the metasedimentary successions found in the region. Four informal stratigraphic units have been distinguished in the S. Agata area. The lowest one (Unit A) consists of well‐bedded metalimestones and bioturbated marly limestones that correlate with Ladinian–Carnian carbonates in nearby areas. A second unit (Unit B), never recognized before, contains a complex alternation of dolomites, phyllites and some meta‐arenites containing several beds of Cavernoso facies, attributed to the Carnian. They grade upward to platform and platform‐margin dolomites of Norian–Rhaetian age (Unit C) that in turn are replaced upward and laterally by a fourth unit (Unit D) consisting of well‐bedded, dark dolomites and metalimestones with marly interlayers locally found as resedimented large blocks in slope conglomerates. Unit D correlates with Rhaetian–Liassic beds in nearby areas. Several pieces of evidence of post‐metamorphic contractional tectonics, with 140°N and 30°N trends, are found together with evidence of SW‐directed extension. The siliciclastic Carnian beds of Unit B are correlated with the phyllites of Cetraro, formerly believed to be Middle Triassic; moreover, it is suggested that in the Cetraro area Unit C is almost totally replaced by Unit D. This demonstrates that the former distinction between the two tectonic units in the whole area has to be discarded. We have made a general palaeoenvironmental reconstruction which progresses laterally, during Ladinian–Carnian times, from (i) a coastal, mixed siliciclastic–carbonate–evaporitic area at Cetraro to (ii) a transitional carbonate shelf where siliciclastic input was only episodic, and finally to (iii) a bioconstructed margin which was later replaced by a steepened margin created by tectonic instability. Starting from the Norian, subsidence shifted toward the former coastal area where an intraplatform, restricted basin developed. The proposed stratigraphy corresponds closely to the Alpujarride units of the Betic Cordillera, Spain. Moreover, it is shown that strong affinities also exist, in terms of the structural framework, with the metamorphic units of Tuscany and Liguria. Copyright © 2005 John Wiley & Sons, Ltd.     

The metahyaloclastitic matrix of a unique metavolcanic block reveals subduction in the Somozas Mélange (Cabo Ortegal Complex,NW Iberia): tectonic implications for the assembly of Pangea

The allochthonous Cabo Ortegal Complex (NW Iberian Massif) contains a ~500 m thick serpentinite‐matrix mélange located in the lowest structural position, the Somozas Mélange. The mélange occurs at the leading edge of a thick nappe pile constituted by a variety of terranes transported to the East (present‐day coordinates; NW Iberian allochthonous complexes), with continental and oceanic affinities, and represents a Variscan suture. Among other types of metaigneous (calcalkaline suite dated at 527–499 Ma) and metasedimentary blocks, it contains close‐packed pillow‐lavas and broken pillow‐breccias with a metahyaloclastitic matrix formed by muscovite–paragonite–margarite–garnet–chlorite–kyanite–hematite–epidote–quartz–rutile. Pseudosection modelling in the MnCNTKFMASHO system indicates metamorphic peak conditions of ~17.5–18 kbar and ~550 °C followed by near‐isothermal decompression. This P–T evolution indicates subduction/accretion of an arc‐derived section of peri‐Gondwanan transitional crust. Subduction below the Variscan orogenic wedge evolved to continental collision with important dextral component. Closure of the remaining oceanic peri‐Gondwanan domain and associated release of fluid led to hydration of the overlying mantle wedge and the formation of a low‐viscosity subduction channel, where return flow formed the mélange. The submarine metavolcanic rocks were deformed and detached from the subducting transitional crust and eventually incorporated into the subduction channel, where they experienced fast exhumation. Due to the cryptic nature of the high‐P metamorphism preserved in its tectonic blocks, the significance of the Somozas Mélange had remained elusive, but it is made clear here for the first time as an important tectonic boundary within the Variscan Orogen formed during the late stages of the continental convergence leading to the assembly of Pangea.