Search results for "Crust"

The formation of large quartz veins by rapid ascent of fluids in mobile hydrofractures

2001

Abstract This paper aims to resolve two main problems related to the formation of quartz veins: (1) the predominance of quartz veins at shallow crustal levels and not deeper in the crust, close to the source of metamorphic fluids where the temperature sensitivity of quartz solubility is much higher than at lower, upper-crustal temperatures and (2) the formation of very large 100–1000 m scale quartz veins that would require huge amounts of fluid flow in current models of vein formation. It is proposed here that these problems are resolved by the recognition of very fast (m/s) mobile hydrofracture ascent of batches of fluid. Mobile hydrofractures are fluid-filled fractures that propagate at t…

Eastern Pontides and Black Sea: gravity inversion, crustal structure, isostasy and geodynamics

2002

Abstract Lacking detailed seismic data on the crustal structure of Anatolia and the transition to the Black Sea, it is attempted to invert gravity for crust-mantle structure with constraints from the limited a priori information available, as average continental and oceanic crust, local topography, an isostatic model, published marine seismic data and a tentative “fix point” from recent seismological receiver functions near the Black Sea coast. An initial 2D-model for a north–south profile along about 40°E longitude is constructed and adjusted to fit the Bouguer anomaly taken from a published Turkish map and results from satellite radar altimetry. Isostasy, seismic data and gravity inversio…

An active oblique-contractional belt at the transition between the Southern Apennines and Calabrian Arc: The Amendolara Ridge, Ionian Sea, Italy

2014

High-resolution, single-channel seismic and multibeam bathymetry data collected at the Amendolara Ridge, a key submarine area marking the junction between the Apennine collision belt and the Calabrian subduction forearc, reveal active deformation in a supposedly stable crustal sector. New data, integrated with existing multichannel seismic profiles calibrated with oil-exploratory wells, show that middle to late Pleistocene sediments are deformed in growth folds above blind oblique-reverse faults that bound a regional pop-up. Data analysis indicates that ~10 to 20 km long banks that top the ~80 km long, NW-SE trending ridge are structural culminations above en echelon fault segments. Numeric…

Partial Melting and Counterclockwise P T Path of Subducted Oceanic Crust (Sierra del Convento Melange, Cuba)

2007

Continental collision and the dynamic and thermal evolution of the Variscan orogenic crustal root — numerical models

2001

Abstract Orogeny is modelled numerically by treating continental collision within full convection solutions, in order to better understand some aspects of the Variscan structures and processes. Three different approaches are taken: (1) collision where one ‘continental plate’ is ‘pushed’ against another across a zone of weakness; (2) gravitational instability of a lithospheric mantle root leading to delamination, slab break-off and crustal root reduction; (3) melting in the lower part of a crustal orogenic root. The first approach demonstrates that thick (but in the models: cool) roots can accumulate, in which upper crustal rocks are carried to great depth and mantle material may be carried …

Seasonal studies of the biology ofAchtheres percarumin perch,Perca fluviatilis, from four Finnish lakes over a 3-year period

1993

Achtheres percarum infection on the gills of perch Perca fluviatilis was studied from four lakes in central Finland in monthly or bimonthly samples of fish during a 3-year period. The highest prevalence and intensity of infection (30%, 0.7 copepods/fish) were found in the oligotrophic, unpolluted Lake Peurunka and the lowest (6%, 0.1 copepods/fish) in the eutrophic and polluted Lake Vatia. According to hierarchical loglinear models the prevalence of A. percarum infection was related to the lake, but not to the year. However, when logit models were constructed such that two ‘seasons’ (‘cold’ and ‘warm’ periods) were included, it was apparent that the year also influenced the prevalence of A.…

Histological and electron microscopical observations on the effects of lead on gills and midgut gland ofProcambarus clarkii

1991

Adult intermolt specimen of Procambarus clarkii (Crustacea, Decapoda) have been treated for 96 hours in aquaria with 100mg/l of lead. The gills and midgut gland were processed and studied in the electron microscope. The gill filament shows important changes in the ultrastructure of the epithelial cells and the cuticle. The hepatopancreatic cells studied (i.e. the vacuolated and dark cells) do not show noticeable structural changes but accumulate lead (electrondense precipitates) mainly in lysosomes.

Determination of lead in treated crayfish Procambarus clarkii: accumulation in different tissues.

1988

The continual loading of trace metals into our environment represents a water pollution problem due to their toxic effects on aquatic biota. In addition, metal ions can be incorporated into food chains and concentrated by aquatic organisms to a level that affects their physiological state. There are several investigations on the toxic effects and bioaccumulation of lead in fishes, molluscs, and crustaceans. Lake Albufera (Valencia, Spain) and the surrounding rice-field waters are subjected to large loads of sewage and toxic industrial residues (including heavy metals) from many urban wastewaters in the area. In 1978, the American red crayfish Procambarus clarkii (Girard) appeared in Lake Al…

REDUCTION IN THE LEVEL OF INFECTION OF THE BIVALVE ANODONTA PISCINALIS BY THE COPEPOD PARAERGASILUS RYLOVI USING HIGH TEMPERATURE AND LOW OXYGEN

2003

The aim of this study was to develop a method to kill or expel the gill-dwelling crustacean parasite Paraergasilus rylovi from a common freshwater clam, Anodonta piscinalis. Naturally infected clams were exposed to different water-quality treatments and monitoring in the laboratory. In a high-temperature treatment (26 C vs. control 18 C), the mean abundance of the parasite decreased to near zero in 7 days. Because only 2 clams of 72 died in this treatment during the 14-day experiment, the survival of the host was not seriously at risk at the high temperature. 'Low oxygen, no water change' (18 C) was the second most effective treatment, followed by a 'low-oxygen, water-flow' (18 C) treatment…

Increased Parasite Abundance Associated with Reproductive Maturity of the Clam Anodonta piscinalis

1999

Several studies on vertebrates have demonstrated that reproductive activities may increase the parasite load, but this has not been shown in invertebrate hosts. We studied abundance of a potentially harmful gill parasite, the ergasilid copepod Paraergasilus rylovi, from the freshwater bivalve host Anodonta piscinalis in relation to reproductive maturity of the host in the field. Prevalence of this previously unstudied parasite varied from 90 to 100%, and the mean parasite abundance from 16.3 to 28.8 among 3 study populations. Abundance of P. rylovi increased with host size. In the maturating age groups (3-5 yr) the length-adjusted mean parasite abundance among mature, reproducing female cla…