External Belt Research Articles

A New Family of Sandwich-Type Polytungstophosphates Containing Two Types of Metals in the Central Belt: M′2M2(PW9O34)212−(M′ = Na or Li, M = Mn2+, Co2+, Ni2+, and Zn2+)

A new family of sandwich-type polytungstophosphates containing two different types of metals in the central belt, M'(2)M(2)(PW(9)O(34))(2)(12-) (M' = Na or Li, M = Mn(2+), Co(2+), Ni(2+), and Zn(2+)), have been synthesized and characterized by infrared spectroscopy, (31)P solution NMR spectroscopy, and elemental analysis. Compounds Na(2)Co(2)(PW(9)O(34))(2)(12-) (Na2Co2), Na(2)Ni(2)(PW(9)O(34))(2)(12-) (Na2Ni2), Li(2)Ni(2)(PW(9)O(34))(2)(12-) (Li2Ni2), Na(2)Mn(2)(PW(9)O(34))(2)(12-) (Na2Mn2), and Li(2)Zn(2)(PW(9)O(34))(2)(12-) (Li2Zn2) were characterized by X-ray crystallography. All these compounds have similar structures, in which two transition-metal ions and two alkali metal ions (sodium or lithium) are sandwiched between two [B-alpha-PW(9)O(34)](9-) units; the transition and alkali metals reside in the internal and external (solvent exposed) positions of the central belt, respectively. By adding LiCl to aqueous solutions of compounds Na2M2, lithium-sodium exchanges in the external belt positions are observed by (31)P solution NMR spectroscopy and X-ray crystallography. Magnetic measurements indicate ferromagnetic exchange interactions between the two Ni(2+) ions in Na2Ni2 at 10-300 K and the two Co(2+) ions in Na2Co2 at 6-30 K. In contrast, Na2Mn2 exhibits an antiferromagnetic interaction between the Mn(2+) ions at 2-50 K.

Folding kinematics expressed in fracture patterns: An example from the Anti-Atlas fold belt, Morocco

The Anti-Atlas fold belt, Morocco, formed during the same Variscan collisional event that produced the Valley-and-Ridge fold-thrust belt of the Appalachian mountains. Both are external belts of the Appalachian–Ouachita–Mauritanides chain and at the map scale have very similar topographic expressions. The Anti-Atlas, however, consists of map-scale folds that are buckle-related, detachment folds, whereas the Valley-and-Ridge folds developed in response to imbricate thrusting. For this reason, the Anti-Atlas is referred to as a fold belt rather than a fold-thrust belt. This paper examines Variscan folding processes in the Anti-Atlas Mountains. Folding in some layers occurred by sliding along a penetrative network of mesoscale fractures, i.e. cataclastic flow, during buckling. Layer-parallel shortening fractures were reactivated in the later stages of folding to accommodate limb rotation. Although ‘boutonnieres’, i.e. basement uplifts, punctuate the fold belt, the fracture patterns indicate that the uplifts failed to provide any ‘bending’ component. Folding is also interpreted to occur under low to moderate confining pressures because the fracture network includes conjugate shear fractures with very small (∼20°) dihedral angles.

Development of Color Fusing System using External Belt Heating Technology

Development of Color Fusing System using External Belt Heating Technology

Variations in the transient prograde geothermal gradient from chloritoid‐staurolite equilibria: a case study from the Barrovian and Buchan‐type domains in the Bohemian Massif

AbstractThermodynamic modelling of metamorphic rocks increases the possibilities of deciphering prograde paths that provide important insights into early orogenic evolution. It is shown that the chloritoid–staurolite transition is not only an indicator of temperature on prograde P–T paths, but also a useful indicator of pressure. The approach is applied to the Moravo‐Silesian eastern external belt of the Bohemian Massif, where metamorphic zones range from biotite to staurolite‐sillimanite. In the staurolite zone, inclusions of chloritoid occur in garnet cores, while staurolite is included at garnet rims and is widespread in the matrix. Chloritoid XFe = 0.91 indicates transition to staurolite at 5 kbar and 550 °C and consequently, an early transient prograde geothermal gradient of 29 °C km−1. The overall elevated thermal evolution is then reflected in the prograde transition of staurolite to sillimanite and in the achievement of peak temperature of 660 °C at a relatively low pressure of 6.5 kbar. To the south and to the west of the studied area, high‐grade metamorphic zones record a prograde path evolution from staurolite to kyanite and development of sillimanite on decompression. Transition of chloritoid to staurolite was reported in two places, with chloritoid XFe = 0.75–0.80, occurring at 8–10 kbar and 560–580 °C, and indicating a transient prograde geothermal gradient of 16–18 °C km−1. These data show variable barric evolutions along strike and across the Moravo‐Silesian domain. Elevated prograde geothermal gradient coincides with areas of Devonian sedimentation and volcanism, and syn‐ to late Carboniferous intrusions. Therefore, we interpret it as a result of heat inherited from Devonian rifting, further fuelled by syntectonic Carboniferous intrusions.

Upper Devonian carbonate platform correlations and sea level variations recorded in magnetic susceptibility

This paper concerns the analysis of four outcrops in the Frasnian (Upper Devonian) of Belgium. We compare the results of a precise sedimentological analysis with magnetic susceptibility (MS) data. This comparison allows us to improve stratigraphic correlations and to test the relationship between magnetic susceptibility and sea level changes. Considering the sedimentological study, different microfacies have been identified, from the external belt dominated by relatively argillaceous open marine facies with crinoids, to the biostromal and the lagoonal belt dominated by algae-rich muddy facies. Fourth- and third-order sequences have also been identified and are probably related to sea level variations. Magnetic susceptibility data provides us very good fourth-order correlations and the link between magnetic susceptibility and different sedimentological parameters is obvious. More precisely, MS appears to be related to fourth- and third-order sequences and to microfacies.

The Spatial Distribution of Quality of Life in the United States and Interstate Migration, 1965–1970 and 1985–1990

This study applies a relatively new method called ‘co-plot’ to examine the relationships between the 48 contiguous states of the United States and selected indicators of quality of life in 1970 and 1990, and how these characteristics coincide with five-year interstate migration rates. The findings show an overall process of polarization of quality of life throughout the country. Strong similarity was found between states of a given division or region. The states which composed New England, the Middle Atlantic and the Pacific divisions are located in the strong sector of the socio-economic space. The direction of migration is toward states of the more external belts of the country. In the second part, multiple regression analysis was applied revealing a strong effect of economic incentives on migration; over time; migration turns into a widespread phenomenon among different socio-economic groups, with income becoming less significant as a predictor of interstate migration.

The alien bivalve Anadara demiri (Arcidae): a new invader of the Adriatic Sea, Italy

This paper reports the observations recorded on the arcid clam, Anadara demiri, from its first reporting in the Adriatic Sea three years ago, when its presence only was noted, to the present day when its invasive potential is confirmed. Repeated recruitment events were observed and confirmed by the co-existence of two or more cohorts within the population. Anadara demiri appears to be a year-round spawner with two spawning peaks (late winter and summer). Together with the congeneric invader, Anadara inaequivalvis, it has colonized the external belt of the fine well-sorted sand biocoenosis where they may numerically dominate the benthic community. Anadara demiri appears to have gained full status as a component of the Adriatic Sea coastal benthic community despite its very recent first entry. Numerous features make it a strong competitor among which is the ability, retained into adult life, of attaching, by means of byssus threads to all kinds of hard substrata, particularly to other live molluscs such as the gastropod Aporrhais pespelecani and the bivalves Anadara inaequivalvis and Chamelea gallina. The presence of species actively interfering with A. demiri in various ways (the polychaetes, Polydora sp. and Sabellaria spinulosa, that bore into and foul the shell, respectively, and the predatory asteroid Astropecten irregularis) is discussed.

Thick‐skinned tectonics in the external Apennines, Italy: New evidence from magnetic anomaly analysis

We discuss the tectonic implications of a new residual magnetic map of the Apennine belt/Adriatic‐Apulian foreland obtained by integrating ground and offshore data sets [Chiappini et al., 2000a]. Negative anomalies are documented over the Adriatic‐Apulian foreland areas, whereas the external Apennine belt is characterized by a ubiquitous low‐amplitude (<30 nT), long‐wavelength positive anomaly. In the central northern Apennines, three ∼100 km wide more intense (100–200 nT) round‐shaped anomalies are superimposed to the long‐wavelength feature. Finally, in the Tyrrhenian Sea and margins, high‐intensity, short‐wavelength positive‐negative couplets coincide with magmatic outcrops or bodies at shallow depth. The low‐amplitude anomaly pattern over Italy suggests that the magnetic basement beneath the Triassic evaporites is ubiquitously incorporated in the external belt compressive fronts, implying a thick‐skinned tectonic style for the external Apennines. The new residual magnetic map resolves the inconsistency between previous aeromagnetic data [AGIP SpA. Italia, 1981], which suggested a lack of basement involvement in the Apennine belt, and recent seismic data, which imaged deep reflectors penetrating the basement. Two magnetic models along NE‐SW transects in the northern and southern Apennines suggest consistent structural styles. In the northern Apennines, positive anomalies roughly coincide with the external compressive fronts, although there are local second‐order differences between the belt front and the edges of the anomaly. Here the magnetic data show that the basement rises southwestward along the thrust fronts from 6–7 km depth in the Adriatic foreland to 2–3 km depth in the axial belt, where some exploration wells have penetrated basement. Within the belt front, basement exhumation is inferred to occur along high‐angle, low‐displacement thrust faults inverting preexisting normal faults. In the southern Apennines, a remarkable positive magnetic anomaly is parallel with and tens of kilometers southwest of the belt front. Seismic data and oil wells show that the basement surface cannot be shallower in the belt than in the foreland. Therefore the observed magnetic anomaly is produced by strongly magnetic basement beneath the belt, likely an internal crustal wedge tectonically interposed between the Apulian carbonate sequences and basement.

Terrestrial Habitat Preferences of Adult Arroyo Southwestern Toads

Using an external belt attachment system, we attached 1.8-g radiotransmitters to arroyo southwestern toads (Bufo microscaphus californicus). We tracked 83 arroyo southwestern toads over an average period of 30.9 days (SD = 29.0) in 1998. Male calling activity began at the study site on 6 March and ended on 29 July. We observed arroyo toad activity in upland habitats throughout the study. We examined the habitat preferences of arroyo toads by comparing land cover within a minimum convex polygon estimate home range for each animal to the study site subarea where each toad occurred. We also compared substrate, vegetation, and vegetation structure use to availability within each minimum convex polygon area. We found significant between-sex differences in land use and vegetation-type preferences during the study, but not for substrate or vegetation-structure preferences. Female arroyo southwestern toads preferred terrace and channel habitats to campground, agricultural, or upland habitats.During the breeding season, male arroyo southwestern toad preference for channel habitats was significantly greater than for all other habitat types. Toads preferred sands for burrowing substrate, but no substrate type was preferred for surface activity. Differences in preference rank for vegetation type were weak. Male use of agricultural lands adjacent to breeding sites increased after the breeding season. Dense, tall vegetation structures were least preferred by arroyo southwestern toads for burrows. Arroyo southwestern toads may forage and disperse through many vegetation types that are common in riparian and upland habitats of southern California.

A TRANSECT IN SOUTHERN TUSCANY, FROM THE BACCINELLO BASIN TO THE CETONA RIDGE

The Northern Apennines (NA) is a NE-verging thrust and fold belt (Fig. 1) produced by the Cenozoic collision between the Corso-Sardinian block and the Adria Plate (Boccaletti and Guazzone, 1972; 1974; Principi and Treves, 1984; Malinverno and Ryan, 1986, among others). The NA thrust-nappe pile consists of sequences deposited on the Adria Plate continental margin (Tuscan and Umbria-Marche Units) which were overthrust by the Ligurian Units during continental collision. The Ligurian Units, which consist of ophiolites and their sedimentary covers, represent the remnants of the Ligurian-Piedmont paleo-ocean (Abbate et al., 1970). The NA evolution, after the Oligocene continental collisional phase, has been referred to two different models. In the first one, the development of an external thrust belt shifting eastwards, coupled with an internal extensional area is envisaged. In this process both the crust and the lithosphere would be involved (Merla, 1951; Boccaletti and Guazzone, 1974; Elter et al., 1975; Carmignani et al., 1980; Boccaletti et al., 1990; Patacca et al., 1990). In front of the migrating chain a foredeep basin developed during Late Oligocene-Miocene, whose deposits were progressively annexed to the chain (Ricci Lucchi, 1986; Boccaletti et al., 1990). In the second model, the accretionary prism, thickened by crustal collision, would collapse to recover its equilibrium conditions (Carmignani and Kligfield, 1990). As a consequence of the gravitational collapse, the development of core complex structures and of extensional tectonics has taken place since Burdigalian-Langhian (Carmignani et al., 1994). In this model, the Northern Apennines thrust belt is explained as due to gravitational tectonics active since the Early Miocene (Decandia et al., 1993; Carmignani et al., 1995). Starting in late Tortonian, the internal area (hinterland) of NA was characterized by the development of continental and marine basins, mostly striking from NW-SE to N-S, and subparallel to the main thrust fronts of the chain. Their formation has been commonly referred to the extensional processes related to the opening of the Tyrrhenian Basin, either in a back-arc regime (Boccaletti and Guazzone, 1972; 1974; Malinverno and Ryan, 1986; Royden et al., 1987; Boccaletti et al., 1990; Patacca et al., 1990), or as due to late orogenic gravity collapse (Carmignani and Kligfield, 1990; Cameli et al., 1993; Carmignani et al., 1994; Keller et al., 1994). The eastward younging trend of the hinterland basins has been related to the eastward shifting of the extensional front, which followed the migration of the thrust front (Merla 1951; Elter et al., 1975). However, in the last two decades structural studies have shown that the deposits of the hinterland basins have been affected by widespread compressional deformations and by major angular unconformities (Boccaletti et al., 1995, and references therein) that allow to subdivide the entire succession into five Unconformity Bounded Stratigraphic Units (UBSUs, Salvador, 1987).) since the unconformities that limited each UBSU have been correlated on a regional scale, (Boccaletti et al., 1994; 1995). The deformations affecting the basin fill, their architecture, the presence of regional unconformities strongly suggest that they have mostly developed under a compressional tectonic regime, tied to reactivation of thrust faults affecting the pre-Neogene substrate (Boccaletti et al., 1995; 1997; Bonini and Moratti, 1995; Landi et al., 1995). The objective of this excursion, whose road log is reported in Fig. 2, is to illustrate the relationships between tectonics and sedimentation in the hinterland basins along a transect across Southern Tuscany including the Baccinello-Cinigiano, Velona and Siena-Radicofani Basins. In this area, basin development has been mainly related to the activity of two crustal thrusts: the Mid-Tuscany Metamorphic Ridge and the Cetona Mountain thrusts (Fig. 3).

THE MONTGENEVRE OPHIOLITE MANTLE SECTION. FROM GENESIS TO LATER PROCESSES: PETROLOGICAL AND STRUCTURAL CONSTRAINTS

The Alpine Piedmont Ligurian ophiolites are considered to be remnants of the Jurassic Tethyan ocean. Numerous similarities with northern Apennines ophiolites have been emphasized, particularly with the external belt. The most typical features of these ophiolites are: (1) a lherzolitic mantle section, (2) a reduced cumulate high level-type gabbroic portion, without well defined layering, (3) a lack of a sheeted- dyke complexes; (4) a reduced and discontinuous MORB crustal section. An upwelling of lherzolitic mantle with a low degree of partial melting, in a slow-spreading ridge environment, is generally proposed for the genesis of such a succession. The minor proportion of gabbros together with their high-level type characteristics are considered to be the result of crystallization in small magma chambers dispersed within the lherzolitic upper mantle. Except for minor exceptions, primary contacts between upper mantle and gabbro sections are not observed. This is due to modifications during oceanic and alpine tectonism. The Montgenevre ophiolite complex (MOC) is well known for having largely escaped Alpine metamorphic overprinting. Comprising several tectono-lithological units, it presents a complete pseudo-stratigraphy. Thus it is a favourable context for the study of primary features and oceanic transformations. Peridotitic rock-types are intensely serpentinized (> 90% most often, locally up to 70% only). Mantle peridotites are mainly lherzolites, but minor associated wehrlitic, harzburgitic, and dunitic zones are associated. Plagioclase-bearing peridotites are common. Serpentinites crop out either: (1) in the basal complex of the MOC, which is characterized by ophiolitic masses, and detritus, incorporated within the supra-ophiolite sedimentary cover and the schistes lustres, or, (2) mainly, in the upper tectonic unit, or klippe, essentially composed of the ophiolitic succession. The serpentinized peridotites are dominantly exposed at the eastern part of the upper unit. At the western part, with dominant submarine volcanites, serpentinites, often crushed, are localized only at the contact zone with the basal complex or along the contacts between lithological units, particularly between gabbro and serpentinized peridotite, testifying for a tectonic relationship. Several primary characteristics are still recognizable within the serpentinites: (1) type of original peridotite, (2) impregnation or not of basaltic liquid, (3) mantle tectonite or ultrabasic cumulate textures, (4) reworked serpentinites sometimes capped by a supra-ophiolite sedimentary cover. Moreover, as classically observed, pyroxenitic and troctolitc- gabbroic levels, gabbro and dolerite more or less rodingitic dykes, and albitite are associated within the mantle section. Petrological and structural considerations are obtained from the study of such relationships. The macroscopic and microscopic structures observed within the Montgenevre ophiolite upper mantle ultrabasic rocks, in a context apparently close to the petrological Moho, are mostly of tectonite type with high temperature plastic deformation of olivine and orthopyroxene, typical of asthenospheric conditions. Sometimes mylonitization developed in the oceanic environment, certainly during transverse or longitudinal fracturing of the lithosphere. The latter observation is typical of slow spreading ridge environments as observed for instance in the MAR Vema fracture zone. Magmatic liquid percolation locally modified the peridotitic rocks (e.g., impregnated lherzolites) and can, in some cases, when very close to the Moho, produce troctolitic lithologies belonging to the lowermost part of the cumulate section. Such rocks are sometimes difficult to differentiate from mantle peridotitic types exhibiting major melt impregnation, or even more or less diffuse melt “pockets”, and also caracterized by cumulate textures. There is no difference in primary mineralogical composition or in textural features, but the troctolitic rocks in the mantle suffered from rodingitic recrystallizations, whereas they are saussuritized in the lowermost crustal section. Another discriminant way is structural, based on lattice study of olivine crystals which should be undeformed (or very slighly plastically deformed) with low concentration of intracrystalline defects when related to the lowermost cumulate crustal section. For comparable mantle related ultrabasic cumulates, olivine is indeed strongly plastically deformed (with high intracrystalline defects concentration). Other presented petrological considerations are mainly based on geochemical data (major, trace and rare earth elements, and lead isotopes analyses).

Contemporaneous extension and compression in the Northern Apennines from earthquake fault-plane solutions

SUMMARY The Northern Apenninic arc belongs to the deformation zones surrounding the Adriatic plate, which behaves as a rigid block. It is a NE-verging fold-and-thrust belt, which developed since the Miocene with the migration of an extensional-compressional pair. Previous seismological data are roughly in agreement with this deformation picture, although the outer compressional front was not clearly defined by the few available solutions. In this work we confirm the existence of two adjacent zones of contemporaneous extension and compression in the Northern Apennines, defining the extent of these two zones and their interim1 deformation better than was previously done. This is accomplished through the analysis of 125 new focal mechanisms of earthquakes (2.6 < Md < 4.8) recorded by the national network of the lstituto Nazionale di Geofisica in the period 1988-1995. The two deformation zones are clearly separated and lie very close to each other with a partial overlapping in the Emilian-Tuscan Apennines. Strikeslip events are scattered in most of the study area. Thrust-faulting earthquakes are located in the internal part of the most recently active thrust front (middle-upper Pleistocene). There is a general trend of the compressional P-axes of thrust-fault and strike-slip solutions to be perpendicular to the Apenninic direction in the external zone, while the tensional axes of the normal-fault and strike-slip solutions in the belt do not show a uniform orientation. However, clearly evident is the -ENE direction of extension in the peri-Tyrrhenian region, consistent with the direction of Shmln in the Quaternary volcanoes of this region inferred from borehole breakouts and microearthquake fault-plane solutions. We determined the orientation of the stress tensor in the two main deformation zones by inversion of the 125 fault-plane solutions determined in this study. We found that the external belt is characterized by NE-SW compression (ol horizontal, oriented N45E), while a normal-faulting regime with o3 - E-W oriented is characteristic of the Umbria-Tuscany (back-arc) region.

Are Coronae Restricted to Venus?: Corona-Like Tectonovolcanic Structures on Earth

Coronae may not be tectonovolcanic features ‘unique to Venus’ because both the processes that lead to corona formation, and their final tectonovolcanic output (formation of domes, plateaus, extensional rings, etc.), are also found on Earth. Large-scale corona formation processes on Earth may be restricted (because of plate motion) but not absent. The same applies to resurfacing processes. We here suggest that at least, the early stages of corona formation can be recognized in intraplate tectonic settings on Earth. The African plate displays many Cenozoic examples of plume-related domal uplifts and volcanism (e.g., Hoggar, Tibesti, Darfur, Ethiopia). Furthermore, the east African rift system (EARS) around lake Victoria displays many striking features that resemble those of the Venus coronae associated with extensional belts. Among these are the following: (1) an overall elliptical shape; (2) the existence of a mantle plume (Kenya plume) centered beneath lake Victoria; (3) a central plateau (east African plateau); (4) an external extensional belt (the EARS east and west branches); (5) doming processes (Kenya dome); and last but not least (6) volcanism.

Dynamics and seismotectonics of the West-Alpine arc

In this paper we present a comparative review of structural, seismic and focal mechanism data from the West-Alpine arc. In the Western Alps, seismic activity is concentrated along an external belt, corresponding to the Penninic front, and an internal belt, corresponding to the Austro-Alpine front and its southern extension. These seismic belts are connected in the NE by a seismic lineament, corresponding to the Simplon and Centovalli Line and in the south by the E-W-trending seismic Stura “couloir”, located between the Argentera and Dora Maira massifs. The SimplondashCentovalli-Tonale system and the Stura “couloir” are dextral and sinistral strike-slip systems respectively; this implies a westward translation of the West-Alpine arc and the Po Plain. Based on these observations, a seismotectonic model is proposed in which the frontal Penninic thrust and the basal surface of the accretionary wedge corresponding to the Penninic sole thrust are reactivated. Activity along the frontal thrust increases the arcuate shape of the Western Alps and disengages them from the Central and the Ligurian Alps along the tear faults of the SimplondashCentovalli-Tonale system and the Stura “couloir” respectively. In the wider framework of northern Italy, the sector of the eastern Alps north of the Gailtal Line, is moving in an orogendashparallel direction towards the east. Areas with lateral escape in opposite directions, towards the west for the Po Plain and towards the east for the Eastern Alps, north of the Gailtal Line, are separated by the South Alpine Atesine indenter. A model postulating a double lateral escape and a central indenter matches most of the features of the models of “poinçonnement”. The seismic features of northern Italy agree with the seismicity of the stable sector of northern Europe up to the North Sea. This area is fragmented into blocks bounded by seismic bands, some of which probably reactivate pre-existing structures. The overall stress field of Cratonic Europe is dominated by ndashNW-directed trajectories of maximum horizontal compression. The seismicity of the European Alpine foreland is interpreted as the response of a stable block to the same stress field of northern Italy, which is induced by the ondashgoing NW-SE Africa-Europe convergence. We suggest that the westward translation of the West-Alpine arc continues at present and is the driving mechanism of the observed seismicity.

The role of lifting belts in manual lifting

The objectives of this research were to demonstrate the effects of belts on load lifting capabilities of individuals using the psychophysical method, subjective surveys, and the measurement of external pressure on the abdomen. Two types of belts were used in this study: (a) the Air belt, a registered trade mark and product of Pneumedic Corporation, which represented the type of support belt characterized by an inflatable bladder; and (b) the CompVest belt, a product and registered trade mark of the Comp Equipment Corporation, which represented a mechanical, elastic type of support. Twelve male college students were required to lift tote boxes containing steel shot from the floor to metacarpal III height (knuckle height) at a rate of three lifts per minute for a period of 45 min. Each subject performed three sets of lifts, i.e. once with no belt (control) and once with each of the two belts. The maximum acceptable weight of lift was recorded. Changes in the external abdominal belt pressures during the lifting were recorded using the Texas Interface Pressure Evaluator. A subjective survey consisting of eight questions was administered to each subject after each belt was tested to determine the subject's feelings. In addition to the above survey, a post-test question was given asking the subjects to rank the three treatments in order of preference. Statistical tests showed that the belts did increase the perceived maximum acceptable weight of lift with respect to the control (no belt); however, there was no significant difference between the two belts. Also, the external abdominal pressures generated by the two belts were essentially the same. Results of the subjective surveys tended to favor the CompVest belt over the Air belt.

Collision tectonics in the Cenozoic orogenic zone bordering China, India and Burma

The southeast region of the Qinghai-Tibetan plateau is the region where the Indian subcontinent collided with Eurasia to form arcuate mountain chains along what is now the border area of China, India and Burma. On the basis of Cenozoic deformation, metamorphism and magmatic activity, we can divide this orogenic zone into three tectonic sections: the External, Medial and Internal arcuate belts. These in turn are divided into seventeen major nappes, delineated in a SW to NE cross-section through the orogenic zone. The External belt, composed of the western nappes, contains traces of late Mesozoic and Cenozoic sutures which have undergone significant disruption due to Cenozoic orogenesis; and its Paleozoic strata show affinities to the Gondwanaland facies. The Medial belt, including most notably the nappes of the Jinsha River region, contains the remains of an ancient ocean, very probably the Paleo-Tethys, which separated the Gondwana and Yangzi paleolandmasses in late Paleozoic — early Triassic time. The Internal belt, composed of the eastern nappes, consists mainly of flysch from China's largest Triassic sedimentary basin; and its Paleozoic strata belong to the Yangzi plate.

Thermo-tectonic evolution of a metamorphic internal zone documented by axial projections and petrological P-T paths, Wopmay orogen, northwest Canada

Axial projections of the transversely folded 1.9 Ga Wopmay orogen document stratigraphic and structural relations in a metamorphic internal zone having more than 30 km of structural relief. The greater part of the metamorphic belt is separated from underlying autochthonous Archean basement and thin Early Proterozoic cover by a sole thrust coextensive with that beneath the external thrust-fold belt Site-specific metamorphic pressure-temperature ( P-T ) paths are derived from core-to-rim microprobe analyses of large zoned poikiloblastic garnets that contain abundant inclusions of biotite, plagioclase, quartz, and, in some cases, aluminosilicate. For garnet-absent units, qualitative P-T paths are deduced from overprinting mineral assemblages. The structural and metamorphic data combined with the results of geochronological and contiguous-external-belt studies show that regional metamorphism in the internal zone is the result of three overlapping, thermally additive, thermotectonic regimes: (1) onset of metamorphism during crustal thinning, (2) plutonic heat advection during crustal shortening, and (3) thermal relaxation, concurrent with uplift, as a consequence of crustal thickening.

Considerations on the seismotectonics of the Northern Apennines

The Northern Apennines have been subdivided into homogeneous zones, on the basis of recent structural evolution and crustal structure, in which the earthquake distribution can find a coherent framework. These zones, whose physiography is in strict connection with their structure, are: the Internal Peri-Tyrrhenian Belt; the External or Main Belt; the Buried Belt; and the Pede-Alpine Homocline. Earthquake activity has a tendency to cluster along well-defined bands, particularly in the easternmost border of the Peri-Tyrrhenian Belt, as well as along the zone between the External Belt and the Buried Belt, i.e. along the Padanian margin of the Northern Apennines. A minimum of seismic activity seems to be correlated with some zones of the External Belt, as well as with the Late Tertiary and Quaternary magmatic province of Tyrrhenian Southern Tuscany. The fault-plane solutions are coherent with the structural picture. A tentative seismotectonic model of the Northern Apennines is discussed.

Geothermal activity in Italy: Present status and future prospects

In the Italian Peninsula the Apennines separata a relatively cold Po-Adriatic-Ionian “foredeep” external belt from a warmer Tyrrhenian “back-arc” internal tensional belt. The latter is characterized by high geothermal heat flow together with conspicuous recent or present-day volcanic phenomena. In this area, extending from Tuscany to Campania, lie the known steam- and water-dominated fields (Fig. 1). Other “warm” areas are located on some Tyrrhenian islands. Within the “cold” external belt, interesting locations for low enthalpy utilizations can be found in the Po river valley, particularly in the eastern part near Ferrara and Abano. Since 1977 ENEL (National Electric Energy Agency) and AGIP (State Oil Company) have been jointly conducting geothermal activities in Italy, with the exception of the Tuscan geothermal area where ENEL operates on an exclusive basis. At present the areas surveyed cover about 8250 km 2. As of December 1983 the geothermal installed capacity was 456.2 MW (net capacity 340 MW) and low-temperature geothermal resources equivalent to 100,000 OET ‡ ‡ Oil equivalent tons. /yr were being used. The National Energy Plant (PEN), issued on 4 December 1981, forecast for the year 1990 a geothermal power increment of 200 MW e, above the 449.1 MW e, already installed. The target in the low enthalpy non-electric sector is to save 300,000 OET/yr by 1990. This paper describes the activities carried out from March 1975 to December 1983 and the main projects in progress.

The three metamorphic belts of the Hellenides: a review and a kinematic interpretation

Summary New results obtained in the three metamorphic belts of the Hellenides suggest that each belt has a different structure, geotectonic setting and evolution. The external metamorphic belt of Peloponnesus-Crete has probably resulted from nappe movement in the vicinity of an evolving island arc system. The blueschists occurring within this external belt are allochthonous and have been transported with other nappes over the external carbonate platform of the Pre-Apulian-Plattenkalk-Ionian-Tripolitza-Almyropotamos Units. This implies that there was only one true blueschist domain, initiated in the Cycladic area during ?Early Eocene. The kinematic interpretation is based on the distinction of a- and b-structures and on the nature of the shear zones between the different domains, especially that between the metamorphic Hellenides below and the non-metamorphic Hellenides above. The existence of the probably Lower Palaeozoic meta-sedimentary sequence of Kastoria in the northern Pelagonian zone indicates that the overlying, ophiolite-bearing Almopias unit has been derived from within the Hercynian domain. The Kastoria sedimentary sequence, the ophiolites of Vertiskos and the carbonate platform of Pangeon are considered to be most likely elements of a probable Hercynian orogeny.