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The convergence between the Indian plate and the southern margin of the Eurasian continent created an active continental margin from Late Jurassic until about 40 Ma ago, which then evolved to form the Himalaya and the Tibetan Plateau during the continental collision stage. Post-collisional magmatism in southern Tibet, north of the Yarlung Zangbo Suture Zone (YZSZ) has been active since 45 Ma and is related to normal faulting and extensional tectonism. To date no such magmatism was reported within the YZSZ itself. This paper reports on the discovery of Miocene shoshonites within the YZSZ. They are significant because the magma traveled, at least in part, through oceanic crust, thus limiting interaction with the continental crust to the mid-crustal level and which affected the post-collisional magmatic rocks occurring in the northern part of the subduction system. In addition, xenoliths and xenocrysts of crustal origin in these rocks constrain the nature of metamorphic rocks underlying the YZSZ at mid-crustal level. The geochemical signatures of the shoshonitic rocks, including Nd and Sr isotope systematics, indicate derivation from a garnet-bearing middle continental crustal source. Crustal imprint complicates modeling of the petrogenetic processes which occurred prior to mid-crustal ponding of the magma which took place between 11 and 17 Ma at depths of 40 to 50 km. The significant role of crustal contamination raises serious concerns about models proposed for similar magmatic activity elsewhere in the Himalaya and the Tibetan Plateau.

BackgroundIn Europe and Asia, long-term care funding is disability-based. This introduces a perverse effect by inappropriately adding value to functional decline among beneficiaries. To support the efforts in prevention and rehabilitation made by personnel in long-term care services, indicators have to be developed to promote functional improvement of beneficiaries. As people receiving those services are already experiencing a functional decline process, it is essential to know the natural magnitude of functional decline in order to assess deviation from this expected decline. The objective of the study was to estimate the natural decrease of autonomy in beneficiaries of home care services and nursing homes.MethodsTwo databases were used: for home-dwelling people, 1235 subjects over 75years old who participated in the PRISMA study; for institutions, 1330 residents over 65years old of a nursing home in Sherbrooke (QC, Canada). These subjects were assessed several times over many years with the Functional Autonomy Measurement System (SMAF). Growth analyses were used to estimate the annual decrease in the SMAF score according to age, gender and the initial autonomy status.ResultsAt home, only age was significantly associated with the slope of functional decline. The average annual decrease of subjects 75–84years old was 2.4 points on the SMAF score (out of 87); for those aged over 85, the annual loss was 3.8 points. In institutions, gender and the initial autonomy profile were associated with the annual decrease. For men, the annual decrease varied between 0.7 for the most disabled subjects to 5.2 for the most autonomous. For women, those values varied from 0.2 to 6.6, respectively.ConclusionA decrease in the SMAF score less than these expected values should be associated with a bonus to support personnel training, prevention activities, rehabilitation and activities aimed at supporting the autonomy of the beneficiaries. Such a strategy requires the implementation of a precise and reliable assessment instrument like the SMAF and also the availability of a longitudinal database where data for each beneficiary could be linked over time.RésuméPosition du problèmeLes systèmes de financement des soins à long terme en Europe et en Asie sont basés sur les incapacités des usagers. Cela introduit un effet pervers en valorisant de façon indue la perte d’autonomie des usagers. Afin de soutenir les efforts des intervenants et des services en matière de prévention et de réadaptation, des indicateurs permettant de valoriser l’amélioration fonctionnelle doivent être développés. Comme les usagers âgés sont déjà en processus de perte d’autonomie, il est nécessaire de connaître l’évolution naturelle de l’autonomie fonctionnelle pour apprécier la déviation par rapport à cette perte attendue. L’objectif de cette étude est de déterminer la perte annuelle d’autonomie chez des usagers vivant à domicile et en institution.MéthodeDeux bases de données ont été utilisées : pour le domicile, les 1235 sujets de plus de 75ans de l’étude PRISMA ; pour l’institution, les 1330 usagers de plus de 65ans d’un centre d’hébergement de Sherbrooke (Québec, Canada). Ces sujets ont été évalués à plusieurs reprises sur une période de plusieurs années au moyen du Système de mesure de l’autonomie fonctionnelle (SMAF). Des analyses de courbes d’évolution (growth analyses) ont permis de définir la perte annuelle selon l’âge, le sexe et le profil d’autonomie initial.RésultatsÀ domicile, seul l’âge intervient dans la pente de la perte d’autonomie. La perte annuelle des personnes de 75 à 84ans peut être estimée à 2,4 points du score SMAF (sur 87) alors que celle des 85ans et plus est de 3,8 points. En institution, tant le sexe que le profil initial d’autonomie ont une influence sur la perte annuelle. Pour les hommes, elle varie de 0,7 pour les sujets les moins autonomes à 5,2 pour les personnes les plus autonomes. Pour les femmes, ces valeurs varient de 0,2 à 6,6.ConclusionUne perte inférieure à ces différences de scores devrait être associée à un bonus pour soutenir la formation du personnel, les activités de prévention et de réadaptation ainsi que des activités de soutien à l’autonomie. Une telle stratégie nécessite l’implantation dans les services d’un outil sensible et reproductible comme le SMAF, de même que la disponibilité d’une base de données dans laquelle les évaluations successives des usagers peuvent être reliées entre elles.

Blocks of strongly foliated garnet- and clinopyroxene-bearing amphibolites have recently been discovered in the Saga ophiolitic melange, South Tibet. The Saga ophiolitic melange is a sheared serpentinite matrix melange that crops out along the Yarlung Zangbo Suture Zone (YZSZ), South Tibet. The YZSZ is the youngest and the southernmost of all sutures stretching across the Tibetan Plateau and contains the remnants of the Neo-Tethys ocean that once separated India from the Lhasa block. The garnet- and clinopyroxene-bearing amphibolite blocks are interpreted as parts of a dismembered sub-ophiolitic metamorphic sole. They are made mainly of hornblende, diopside and garnet and were strongly metasomatized during retrogression. Thermobarometry and 40 Ar/ 39 Ar dating on hornblende indicate that they were metamorphosed to peak conditions in excess of 12 kbar and 850 °C between 132 and 127 Ma. Major and trace element geochemistry suggest an N- to E-MORB-type protolith, although a back- or inter-arc basin setting cannot be ruled out. This data supports a model in which the back-arc YZSZ ophiolites (central segment) were trapped in a fore-arc setting by the inception of a subduction at the back-/inter-arc ridge. The cause of this important Early Cretaceous tectonic event might be the presence of an oceanic plateau or hot-spot tracks in the Neo-Tethys, the collision of the Lhasa and Qiangtang blocks in the North and/or the onset of northward movement of the Indian continent in the South. The proposed conceptual model provides an explanation for the absence (or rarity) of Late Cretaceous ophiolites along the YZSZ which are mostly of Late Jurassic to Early Cretaceous age.

The purpose of this first synthesis is to summarize findings on the Yarlung Zangbo Suture Zone (YZSZ) ophiolites and discuss still remaining problems. The YZSZ studied for almost 30 years and is the youngest of the sutures recognized on Tibet Plateau. It is now acknowledged that the YZSZ is a complex assemblage of sedimentary, metamorphic and igneous rocks created during and shortly after the collision between India and Eurasia. The ages of the various lithologies span a time interval from the Jurassic to the Middle Miocene, with some Permian and Devonian exotic blocks from melange zone. The YZSZ is characterized by ophiolitic complexes and ophiolitic melange. The ophiolites are of two types: non dismembered and dismembered sections. The non disturbed sections, although tectonically reworked, are observed along the segment from Dazhuqu to Jiding in Xigaze area and Spontang ophiolite. The dismembered sequences are found in various locations such as Nidar, Kiogar, Jungbwa, Saga, Sangsang, Xigugabu, and Luobusa. The incomplete stratigraphic log could be connected to intraoceanic or orogenetic origins. The ophiolites are distributed into two groups of ages: the Luobusa, Zedang and Kiogar sequences being Jurassic-Lower Cretaceous whereas all other sequences are of Lower Cretaceous age. Compilation of geochronological data suggest that some ophiolite sequences might have evolved for over more than 70 My from their initial genesis to obduction which occurred around 70–90 My ago. Ophiolites differ in terms of petrological and geochemical aspects however, they were all generated in suprasubduction zone and more specifically in arc (few fore-arc) and back-arc settings. Synthesis of more than 700 geochemical analyses show variable mixing of components from N-MORB-type to IAT-CAB and to OIB end-members. The Jurassic ophiolites show the maximum of arc component while the Lower Cretaceous ones show little to strong mixing. In addition, most ophiolites were created in short lived (30 My) basins and generated close to the Eurasiatic continental margin. We propose that Ladakh–Tibet ophiolites were generated in a suprasubduction context similar to Mariana arc, interarc and back-arc or Tonga–Lau system. The variable arc signature of these ophiolites is directly related to their initial position within the suprasubduction system.

The Zhongba ophiolite is located in the western part of the Yarlung Zangbo Suture Zone (YZSZ) separating Eurasia to the north from the Indian plate to the south. This ophiolite comprises a well-preserved mantle sequence dominated by harzburgites with minor dunites. Highly depleted modal, mineral and bulk rock compositions of the harzburgites indicate that they are residues after moderate to high degrees of partial melting (13–24%) mainly in the spinel-stability field. These rocks display typical U-shaped chondrite-normalized Rare Earth Element (REE) patterns and fractionated chondrite-normalized Platinum Group Element (PGE) patterns. These characteristics, in combination with their hybrid mineral and whole-rock compositions intermediate between those of abyssal and forearc peridotites, indicate melt-rock interaction resulting in the selective enrichment of LREE and Pd. We propose a two-stage model to explain the generation of the Zhongba harzburgites: 1) original generation from a MORB-source upper mantle, and 2) subsequent trapping as part of a mantle wedge above a subduction zone. Comparable observations from the ophiolitic massifs along the whole YZSZ allow us to propose that a ca. 2500-km long complex subduction system was active between India and the Lhasa terrane, Burma, and the Karakoram microcontinent within the Neo-Tethys during the Early Cretaceous, similar to the modern active intra-oceanic subduction systems in the Western Pacific.

The Yarlung Zangbo Suture Zone (YZSZ), southern Tibet, is a discontinuous belt that is more than 2000 km long, composed of the remnants of Neo-Tethyan Mesozoic ocean. One of these relicts is the Xiugugabu ophiolitic massif which is a mantle thrust sheet of more than 260 km2 overlying the Cretaceous tectonic melange south of the YZSZ in SW Tibet. The massif is composed of harzburgites and clinopyroxene–harzburgites with porphyroclastic and porphyromylonitic textures. In the southern part of the massif, peridotites were intruded by amphibole-bearing microgabbro and microgabbronorite sills. A diabase unit which is overlaid by a sedimentary sequence crops out on the NE flank of the massif. Mineral chemistry in harzburgites and clinopyroxene–harzburgites indicates compositions similar to abyssal and forearc peridotites. Peridotites are slightly LREE depleted to enriched with [La/Yb]CN 0.06–2.8 and [La/Sm]CN 0.34–2.64. These ultramafic rocks are inferred to be the residues of 5–25% of partial melting of a depleted mantle that has been enriched by percolating metasomatic melts in a suprasubduction environment. Amphibole–microgabbro and amphibole–microgabbronorite sills are mostly composed of brown to green amphibole, calcic plagioclase, clinopyroxene, ilmenite and orthopyroxene in gabbronorite. Textures and compositions of the brown amphiboles indicate a near-solidus high temperature hydrothermal origin (> 800 °C). These intrusive rocks are tholeiitic and show N-MORB type REE patterns ([La/Yb]NC 0.35–0.90), a LILE (mainly Th) enrichment and noticeable Nb, Ta and Ti negative anomalies. They have a suprasubduction affinity and were formed in a back-arc basin setting. The diabase unit outcropping to the NE of the massif is not directly related to the ultramafic and mafic ophiolitic rocks. The diabase shows LREE enriched patterns ([La/Yb]NC 8–8.9) and slight Nb, Ta and Ti negative anomalies. The diabase has an intraplate affinity and could have been derived from a mantle source enriched by subduction-related fluids. The absence of continental crustal assimilation indicates that these rocks were probably emplaced in the Jurassic, in an oceanic environment after the Triassic disaggregation of the Indian plate. The data are consistent with the recent geodynamic model proposed for the central part of the suture for the closure of the Neo-Tethys and suggest that the geodynamic evolution of the western part of the basin was comparable to the central part.

article i nfo The Yarlung Zangbo Suture Zone (YZSZ) is believed to be composed of material largely derived from the destruction of the Neo-Tethys that occurred from early Mesozoic to early Cenozoic. We report here geochronological and petrological data obtained for newly discovered alkaline gabbro blocks embedded in a melange zone of the western YZSZ. Single zircon U-Pb analyses from one representative gabbro sample by SIMS (Secondary Ion Mass Spectrometry) yielded a combined crystallization age of about 363.7±1.7 Ma (1σ). In situ Hf isotopic analyses yielded eHf(t) values of +2.6 to +5.5, suggesting an enriched mantle source. All of the gabbro samples show typical Ocean Island Basalt (OIB) affinity with little or no continental crust contamination. They also display strong geochemical similarities with the Hawaii basalts and the Xigaze seamount basalts suggestive of their intra-oceanic setting. These observations, in combination with the Early Carboniferous layered gabbros reported at Luobusa, indicate that these rocks could represent remnants of the Paleo-Tethys. We propose that a branch ocean separating the Western Qiangtang terrane and the Lhasa terrane from the Gondwana continent might have been present during the Late Devonian and the Early Carboniferous, providing new constrains on the configuration of Paleo-Tethys in Tibetan Plateau during early Late Paleozoic.

The Saga and Sangsang ophiolites are located about 600 and 450 km west of Lhasa and represent a western extention of the central portion of the Yarlung Zangbo Suture Zone (YZSZ) ophiolite belt. The Saga massif comprises fresh mantle lherzolite and cpx-harzburgite, an ophiolite melange (± amphibolite), metamorphosed mafic crustal rocks (meta-gabbro, meta-basalts and amphibolites) and a sequence of uppermost crustal rocks (chert, basaltic lavas, diabase sills and dikes). The Sangsang ophiolite consists of an ophiolite melange (harzburgite) and upper mantle harzburgite with minor lavas and gabbro. Peridotites from both massifs show variable degrees of serpentinization. Their Mg# varies between 0.89 and 0.91. All peridotites show distinct flat REE (rare earth elements) patterns with La/YbN ratios close to 1, probably indicative of a refertilized mantle. The Olivine-Spinel equilibrium and the spinel chemistry for the Saga (Cr# ~ 0.10–0.22) and Sangsang (Cr# ~ 0.30–0.55) peridotites suggest that the Saga peridotites have a deeper mantle provenance (> 20 kbar) and have undergone lower degrees of partial melting (5–12%) than the Sangsang peridotites (

Strongly foliated amphibolite clasts are found embedded within the ophiolitic melange underlying the Xigaze Ophiolite near Bainang and Angren, Yarlung Zangbo Suture Zone, Southern Tibet. These high-grade amphibolites are interpreted as remnants of a dismembered subophiolitic metamorphic sole that would have formed during the inception of a subduction. They include garnet-clinopyroxene amphibolites, clinopyroxene amphibolites and common amphibolites. Petrographic descriptions, mineral chemistry and thermobarometry of these rocks can be found in a companion paper [Guilmette, C., Hebert, R., Dupuis, C., Wang, C.S., Li, Z.J., 2008. Metamorphic history and geodynamic significance of high-grade metabasites from the ophiolitic melange beneath the Yarlung Zangbo Ophiolites, Xigaze area, Tibet. Journal of Asian Earth Sciences, 32, 423–437.]. The geochemistry of the amphibolites confirms that their protoliths were igneous mafic rocks of basaltic to pyroxenitic composition that were likely part of an upper oceanic crust. Rare Earth Elements contents are suggestive of an N-MORB origin. However, enriched LILEs and depleted Nb–Ta–Ti when compared to N-MORBs rather suggest a suprasubduction zone influence. A large proportion of the overlying ophiolitic mafic rocks share the same geochemical characteristics, suggesting the protoliths of the amphibolites might have crystallized in the same environment as the Xigaze ophiolitic crust, likely in a back-arc basin. 40 Ar/ 39 Ar step-heating dating of hornblende concentrates from three samples yielded ages of 123.6 ± 2.9 Ma, 127.7 ± 2.2 Ma and 127.4 ± 2.3 Ma. These cooling ages are slightly younger or overlapping magmatic and sedimentary ages obtained from the overlying ophiolite. All these new data support a model in which the ophiolitic crust and the protolith of the amphibolites were formed along the same spreading center above a subduction zone. The demise of the early subduction circa 130 Ma forced the inception of a new subduction zone at the SSZ spreading axis, burying SSZ mafic rocks underneath a SSZ ophiolitic mantle.

This article aims to describe the validation studies of a social functioning scale developed recently to be possibly added to the SMAF. One hundred and one older adults presenting moderate to severe disabilities and living in two long-term care institutions (LTCI) participated in the validation studies. For the interrater reliability, 51 participants were assessed by two different nurses 24-72 h apart whereas for the test-retest reliability (n=50), they were evaluated twice by the same nurse within a 7-day interval. Convergent validity was verified (n=74) by comparing the new subscale with questionnaires of functional status (Older American Resources and Services, OARS), social participation (Assessment of Life Habits, Assessment of LIFE-H) and social support (Social Provisions Scale, SPS). The interrater reliability and test-retest study showed, respectively, good mean agreement percentages (84% and 85%) as well as good or excellent intraclass correlation coefficients (ICCs) (0.78; 95% confidence interval (CI): 0.64-0.87 and 0.96; CI: 0.93-0.98). The social-SMAF demonstrated significant correlations with the OARS (r=-0.42), LIFE-H (r=-0.31) and SPS (r=-0.49). These results suggest that the new subscale is a reliable and valid tool for assessing social functioning autonomy of the older adult.

The 473 + 5/− 3 Myr Asbestos ophiolite complex of the Quebec Appalachians was formed in a forearc basin and obducted on a margin of Laurentia ~ 460 Myr ago. The complex together with its sedimentary cover is well exposed at Burbank Hill (~ 130 km SW of Quebec City) where eight distinct lithologies have been identified: 1) pyroxenites and wehrlites with minor dunitic layers, (2) fractured gabbros, (3) breccia containing gabbro and diabase fragments, (4) polygenic conglomerates, (5) red mudstone/chert/sandstone succession, (6) tuffs with intercalated grey chert, (7) greenish grey mudstones and (8) slates and sandstones of the Saint-Daniel Melange. The gabbroic and mafic volcanic rocks show the characteristics of arc tholeiites (TiO2 ~ 0.8–0.85 wt.%) and boninites (TiO2 45; (La/Sm)N ~ 1.9–3.3). These rock-types also occur as mafic fragments in the polygenic conglomerate. The mafic fragments (crystals and rocks) within the conglomerate and the ophiolitic sandstones also show the same greenschist facies metamorphism as the mafic igneous rocks of the complex. The conglomerate was probably formed after the forearc crust was fragmented by pre-obduction normal faults. These fault scarps would have promoted the erosion of the oceanic crust, leading to the accumulation of diverse detritus in grabens. The sedimentary lithologies which overlie the conglomerate exhibit a gradual increase in continent-derived material ((La/Sm)N ~ 5 and La/Yb ~ 20) and a decrease in ophiolitic material moving upward in the stratigraphic sequence. The sedimentary rocks at the bottom of the sequence (group 3) are mostly composed of ophiolite material with only 20% of crustal material. They also have a high content of Cr and MgO with values of 350–480 ppm and 5.7–8%, respectively. The rocks of the uppermost part of the pile (group 1) which contain up to 80% crustal material have low abundances of Cr and MgO (30–100 ppm and 2.7–4.5 wt.%). Continental detritus on the top of the Asbestos ophiolite suggests the complex formed near the Laurentian continental margin and that the eroded continental material had access to the basin where the ophiolite was formed. This is consistent with the obduction of the Asbestos and Thetford–Mines ophiolites on the Laurentian margin shortly after their formation. The proximity of thick Laurentian continental crust near the trench could explain why the subduction zone blocked-up soon after the ophiolites formation.

Many comprehensive rating scales have been developed to assess disabilities. These assessments, which require significant amounts of time, are usually performed by trained professionals. A simple case-finding instrument is needed to quickly identify older persons with potential disabilities, who then should undergo comprehensive assessments. In a cross-sectional study of 594 community-dwelling older subjects, we developed a questionnaire from an initial list of 23 yes/no questions, and compared it with an existing one to determine their relative ability to identify older persons with moderate to severe disabilities. Initially designed to identify older people with any disability, the existing seven-question tool also provided to be a good marker of significant disabilities, with a cut-off score of three or more positive answers. The sensitivity and specificity of this cut-off are 78.3% and 74.7%, respectively. These validity indices support the use of this questionnaire in identifying older persons with potential moderate to severe disabilities with a view to referring them for more comprehensive assessment.

Blocks of highly foliated amphibolite are locally embedded within a serpentinite melange underlying the Yarlung Zangbo ophiolites in the Xigaze area of southern Tibet. The ophiolites are remnants of an Early Cretaceous back-arc basin within the Permo-Cretaceous Tethys Ocean, which are exposed along in the Yarlung Zangbo Suture Zone (YZSZ). These amphibolites are interpreted as fragments of a dismembered dynamothermal sole. Three types of amphibolite are present: (1) common amphibolite with assemblages of Hbl + Pl ± Ep ± Ap ± Ttn, (2) clinopyroxene-bearing amphibolite with Hbl ± Pl ± Cpx ± Ep ± Ttn ± Qtz ± Ap and (3) garnet–clinopyroxene-bearing amphibolite characterized by the assemblages Hbl + Cpx + Grt + Pl ± Rt and Grt + Hbl + Pl (corona assemblage). In all three types, plagioclase is pseudomorphed by late albite–prehnite. Retrograde cataclastic veins containing assemblages of Prh + Ab + Ep ± Chl are also present. P–T estimates indicate that the amphibolites reached peak metamorphic conditions of 13–15 kbar and 750–875 °C. Partial replacement of pyrope-rich (up to 35 mole%) garnet by Al-tschermakite (Al2O3 up to 21 wt%) reflects a high pressure (≈18 kbar, 600 °C) metamorphic event followed by rapid exhumation. Soon after exhumation, the amphibolites were intruded by very fine-grained diabase dykes that were then hydrothermally altered. The field relationships and metamorphic history of the amphibolites indicate formation during inception of subduction within a back-arc basin prior to obduction of the ophiolites onto the Indian passive margin.

Background The French health and services system to maintain at home is characterized by its fragmentation, whereas the need of the people for intervention is generally total. This fragmentation have consequences: delay in services delivery, inadequate transmission of information, redundant evaluation, service conditioned by the entrance point solicited rather than by the need of the person and inappropriate use of expensive resources by ignorance or difficulty of access to the less expensive resources. Presentation of the innovation The purpose of integration is to improve continuity of interventions for people in loss of autonomy. It consists in setting up a whole of organisational, managerial and clinical common tools. Organisational model “Projet et Recherches sur l’Integration des Services pour le Maintien de l’Autonomie” (Prisma) tested in Quebec showed a strong impact on the prevention of the loss of autonomy in term of public health on a population level. This model rests on six principal elements: partnership, single entry point, case-management, a multidimensional standardized tool for evaluation, an individualized services plan and a system for information transmission. Contextual analysis Thus, it was decided to try to implement in France this organisational model. The project is entitled Prisma France and is presented here. The analysis of the context of implementation of the innovation which represents integration in the field of health and services for frail older reveals obstacles (in particular because of diversity of professional concerned and a presentiment of complexity of the implementation of the model) and favourable conditions (in particular the great tension towards change in this field). Conclusion The current conditions in France appear mainly favourable to the implementation of integration. The establishment of Prisma model in France requires a partnership work of definition of a common language as well on the diagnoses as on the solutions. The strategic and operational dialogue is thus a key element of the construction of integration. This stage currently occurs in parallel in three areas contrasted in France. The results of associated qualitative research should make it possible to define the factors fostering or hindering the realization of integration according to each site (analyzes contrasted) and in all the sites (related to the particular context of care and French services as a whole).

Objective Seniors use a wide variety of health services delivered by numerous practitioners and organizations. Self-report is the most accessible and cost-effective method to collect information on their use. It is thus important to demonstrate the reliability of this approach. Study Design and Setting As part of a longitudinal study on the effect of an integrated service delivery system, participants (or their proxies) were instructed to use a calendar to record their use of health services. Every 2 months, an interviewer collected use since the last phone contact. A subsample was recontacted by the same or another interviewer to estimate test–retest and interinterviewer reliability, respectively. Data collections were compared using delta and weighted kappa as well as intraclass correlation coefficients. Results Almost perfect agreement was obtained for hospitalization, day surgery, visits to general practitioners and medical specialists, help for home maintenance, and use of voluntary services. Agreement was substantial for visits to the emergency room and home help for personal care. For visits to or by nurses and other health professionals, agreement can be qualified as moderate-to-substantial. Conclusion Assisted self-report of health-services use by older adults or their proxies through bimonthly phone calls is reliable.

The Mesozoic Yamdrock melange and the Triassic flysch lie immediately south of the Yarlung Zangbo Suture Zone (YZSZ) ophiolitic belt, in southern Tibet. The whole-rock chemical signature of sandstones (mostly greywackes), red shales and black shales of the Yamdrock melange and flysch units do not present significant variations between the different rock types and geological units, and is concordant with a continental passive margin source. Despite fairly important chemical weathering, the geochemical signature was not affected by significant sedimentary recycling nor significant heavy-mineral accumulation. REE patterns show an enrichment in LREE typical of shales and indicate that the Neo-Tethyan turbidites mostly derive from a felsic old upper continental crust source. Slight enrichments in Ti and Sc indicate a mafic contribution that could originate from mafic blocks of enriched intraplate geochemical affinity found in the sedimentary units. Sedimentary rocks from both units were thus derived from the old Indian continental crust, including granitic and intraplate mafic blocks, but were deposited in different tectonic settings in the Neo-Tethys ocean. The homogeneity of the YZSZ data, which cover the whole Neo-Tethyan basin, and correlation with Himalayan data support the formation of all Himalayan lithotectonic units along a continuous passive margin of Northern India.

The southern contact of the Yarlung-Zangbo Suture Zone ophiolitic belt is marked by a highly sheared serpentinite melange containing ultramafic blocks. These peridotites can be divided into three main groups. (1) Lherzolites and Cpx-harzburgites contain brownish spinel with Mg# of 0.7–0.75 and Cr# of 0.15–0.27. They resemble fertile abyssal peridotites with generally smooth LREE-depleted and fairly flat MREE–HREE profiles. (2) Transitional harzburgites contain reddish spinels with Mg# of 0.57–0.66 and Cr# of 0.35–0.46. They resemble depleted abyssal or supra-subduction zone peridotites in that MREE–HREE profiles have positive slopes indicative of high degrees of partial melting. LREE profiles vary from depleted to slightly enriched, consistent with some interacting melt. (3) Harzburgites and dunites contain dark reddish spinels with Mg# of 0.47–0.68 and Cr# of 0.40–0.63. They have U-shaped profiles characteristics of interaction between LREE-enriched melt and REE-depleted mantle residues. Fractional melting modelling indicates that Cpx-harburgites may be the residues from 5 to 15% melting, transitional harzburgites from 15 to 23% melting, and harzburgites and dunites from 22 to 29% melting. The South Sandwich arc-basin system is considered a modern analog of the initial geodynamic setting.

The Yarlung Zangbo Suture Zone (YZSZ), Southern Tibet, is marked by a continuous but tectonically disturbed ophiolitic belt. Three main melange-type units lie immediately south of it:the Early Cretaceous ophiolitic melange, the Mesozoic Yamdrock melange and the Triassic flysch.The petrography, mineral chemistry and whole-rock chemistry of mafic rocks from these three geological units are reported in order to assess their tectonic settings. mafic rocks from the ophiolitic melange are mainly gabbros and composed of primary plagioclase, clinopyroxene and locally brown amphibole. Except for a few coarse-grained gabbros that have plagioclase compositions ranging from An 80 to An 50 , most plagioclase grains are albite pseudomorphs. Clinopyroxenes are augite to diopside. Reddish brown tschermakite to magnesiohornblende are probably of magmatic origin. Ilmenite and titanite are common. REE patterns are LREE-depleted with average (La/Yb) N of 0.5. Slight negative Nb–Ta and Ti anomalies suggest that these rocks formed in a back-arc basin. They show geochemical characteristics similar to mafic rocks of the Lau Basin. This study confirms that mafic rocks from the ophiolitic melange are derived from tectonic disruption of the YZSZ ophiolites. mafic rocks from the Yamdrock melange are mostly porphyritic and amygdaloidal basalts. Their primary composition consists of prismatic plagioclase, augite and ilmenite. A few samples also contain small euhedral crystals of brown magnesiohornblende, probably of magmatic origin. These rocks have been affected by low but pervasive hydrothermal metamorphism. REE patterns are LREE-enriched with average (La/Yb) N of 5.3.These rocks are of intraplate affinity, and are similar to volcanic rocks of the Indian Reunion hotspot. mafic rocks from the flysch are mostly gabbros. They are clinopyroxene-rich. Interstitial quartz is common. Ilmenite and titanite are abundant and relatively well preserved. REE patterns are the most LREE-enriched of any analyzed samples from the sedimentary units, with average (La/Yb) N of 6.9, while multi-element patterns show slight negative Nb–Ta and Ti anomalies. These last patterns are similar to patterns in volcanic rocks from the western Deccan Traps of India, whose geochemical behavior reflects mixing between an enriched mantle end-member of Reunion island-type and Indian continental lithospheric material. Hence, these rocks are interpreted to have been derived from an enriched intraplate mantle source, with additional crustal assimilation resulting from disaggregation of the Indian Plate during the opening of the Neo-Tethys ocean. AFC processes have been modelled and strongly suggest a felsic component analogous to Cambro-Ordovician granites as the major contaminant.

The Early Cretaceous Yarlung Zangbo Suture Zone (YZSZ) ophiolites form a nearly continuous E–W-trending belt in southern Tibet. They are remnants of the Neo-Tethys ocean-floor, marking the suture between the Indian and Eurasian plates. Seven ophiolitic massifs in the Xigaze area (from west to east: Lhase, Jiding, Beimarang, Qunrang, Bainang, Dazhuqu and Jinlu), the focus of this study, consist of crustal (volcanic and subvolcanic rocks and cumulates) and mantle (peridotites) units. Crustal samples (basalts and diabases) are subdivided into two groups. The rocks of the first group are LREE-depleted, with [La/Yb]CN=0.6±0.1 and with slight negative Ta–Nb anomalies. They have back-arc basin affinity and occur in the western portion of the study area (Jiding, Beimarang, Qunrang, Bainang massifs and part of the Dazhuqu massif). The second group includes rocks that are LREE-enriched, with [La/Yb]CN=4.6±1.4, and display distinct negative Ta–Nb anomalies. These rocks have an intraoceanic arc affinity and occur in the eastern segment of the study area (the Jinlu massif and part of the Dazhuqu massif). Rocks from the mantle parts of the massifs are mainly harzburgites and can also be subdivided into two groups. Harzburgites of the first group occur in the western part (the Lhase massif and part of the Qunrang massif); they are LREE-depleted with [La/Sm]CN=0.3±0.2, and their spinel composition shows a limited compositional range. The rocks represent the residue after 7–12% melting of a N-MORB-like mantle source. The mantle rocks of the second group occur in the eastern segment of the area (part of the Qunrang massif and in the Bainang and Dazuhuqu massifs). They are LREE-enriched, with [La/Sm]CN=2.8±0.8, and their spinels have a highly variable composition (Cr# varies from 0.13 to 0.82 and Mg# from 0.75 to 0.27). These rocks are inferred to be residue after 30–40% melting of a depleted mantle source but were metasomatically modified by a Ti-poor fluid or magma.

Corriveau H, Hebert R, Raiche M, Prince F. Evaluation of postural stability in the elderly with stroke. Arch Phys Med Rehabil 2004;85:1095–101. Objective To compare clinical and biomechanical measures of balance in elderly stroke patients with those of healthy elderly people. Design Two-group comparison design. Setting Laboratory environment. Participants Fifteen poststroke patients and 15 healthy age-matched older adults (N=30). Interventions Not applicable. Main outcome measures The biomechanical variable COP-COM, which represents the distance between the center of pressure (COP) and the center of mass (COM) in terms of root mean square. The mean of 4 trials of the COP-COM variable for each test condition was used for statistical analysis. Furthermore, the different systems (sensory, motor, central processor) related to postural stability were evaluated. Results Statistical significance of the COP-COM variable was larger in the stroke group than in healthy subjects, in both the anteroposterior (AP) and mediolateral (ML) directions. Furthermore, statistically, stroke subjects showed amplitudes of the COP-COM variable that were significantly larger in the eyes-closed condition. The significant negative correlation demonstrated between COP-COM amplitude and the balance scales (Berg, Tinetti) indicated that the patients with larger COP-COM amplitudes had lower clinical balance score. Furthermore, correlation coefficient scores between COP-COM variables in both AP and ML directions and motor performance using Fugl-Meyer Assessment (ρ=−.53, ρ=−.51, respectively) and reaction time (ρ=−.53, ρ=−.44, respectively) were significant. Vibration (ρ=.41) and touch-pressure (ρ=.42) perception thresholds correlated significantly only in the AP direction. Conclusions Evaluating postural stability with COP-COM variable provided an accurate measure of postural stability in poststroke elderly people. Furthermore, postural stability in quiet stance, as measured by COP-COM amplitude, was related to functional measures of balance as well as physiologic factors relating to balance, such as visual conditions, lower-extremity peripheral sensibility, motor recovery, and simple reaction time.

Lafond D, Corriveau H, Hebert R, Prince F. Intrasession reliability of center of pressure measures of postural steadiness in healthy elderly people. Arch Phys Med Rehabil 2004;85:896–901. Objectives To estimate the immediate test-retest reliability of a single measure of several center of pressure (COP) variables, to report the number of trials to be averaged to obtain a reliable measurement of postural steadiness, and to determine the minimal metrically detectable change (MMDC). Design Cross-sectional study. Setting University biomechanics laboratory. Participants Seven community-living, healthy elderly people over the age of 60 years (range, 62–73y). Interventions Not applicable. Main outcome measures The COP was estimated from 2 force platforms and the following measures were calculated: (1) root mean square (RMS), (2) COP range, (3) COP mean velocity, (4) mean power frequency (MPF), (5) median power frequency (MedPF), and (6) sway area. Intraclass correlation coefficients (ICCs) were determined by using 9 successive quiet standing trials. Results The ICCs obtained for 1 measure of 120 seconds were .58 and .58 for the RMS, .83 and .94 for the COP mean velocity, .52 and .62 for the COP range, .44 and .30 for the MPF, and .34 and .47 for the MedPF in anteroposterior (AP) and mediolateral (ML) directions, respectively. The ICC of the COP sway area obtained for 1 measure was .41. Only 2 trials had to be averaged to obtain an ICC over .90 for the COP mean velocity associated with an MMDC of ±1.2mm/s (AP) and ±0.6mm/s (ML). Conclusions Mean velocity was the most reliable COP measure and using 2 repetitions allowed for reliable measurement of postural steadiness. For the other COP variables, 3 trials of 120 seconds were needed to obtain an ICC over .80.

The objectives of the study were to compare the association and responsiveness of the functional autonomy measurement system (SMAF) and functional independence measure (FIM) as outcome measures addressing functional independence in stroke patients involved in an intensive rehabilitation program and to compare their relationships with a social participation measure after rehabilitation period. One hundred and thirty-two people who had a stroke were evaluated with the SMAF and FIM during the rehabilitation period (T1: admission; T2: discharge; n=132) and twice after discharge (T3=2 weeks; n=118; T4=6 months later; n=102). At T3 and T4, a participation measure, the assessment of life habits (LIFE-H), was added. The main findings are: (1) the total scores on the SMAF and FIM are strongly correlated together (r=0.93 to 0.95; p

In case-control studies using prevalent cases, an apparent association may be spurious if the risk factor affects survival. In his description of this potential bias, Neyman disregarded competing risks. We use a compartment model to illustrate Neyman's bias and show that it can explain the apparent association only if the risk factor influences mortality from the disease being studied. Any effect of the risk factor on mortality from other causes is not relevant. The apparent protective effect of smoking in relation to Alzheimer disease is used as an example, but the result holds for any irreversible noncommunicable disease and for any dichotomous risk factor.

The Beimarang massif is one of many ophiolitic remnants which crop out discontinuously along the Yarlung Zangbo suture zone in southern Tibet. The southern contact of these remnants is marked by a highly sheared serpentinite melange made up of blocks of serpentinites, diabases, gabbros and composite blocks of serpentinites and mafic injections. The Beimarang melange has been investigated in order to bring additional constraints on the origin, metamorphic evolution and obduction processes of the Yarlung Zangbo ophiolite. Petrography and geochemical data suggest that the ultramafic components are similar to moderately depleted upper mantle peridotites. They may represent the already cooled and serpentinized Tethyan upper mantle which was trapped in a mantle wedge at the onset of a north-dipping Early Cretaceous intra-oceanic subduction zone located south of the Gangdese arc. These peridotites were then intruded by back-arc-like mafic magmas whose moderately depleted mantle source was affected by a subduction component. Ultramafic and mafic secondary mineral assemblages suggest that early low-(P/T) metamorphic intra-oceanic conditions reached the amphibolite facies (>550 °C) before being retrograded down to the pumpellyite–prehnite facies (

The Yarlung‐Zangbo Suture Zone, a major geological structure in Tibet, is well known as the locus of tectonic emplacement of the Tethyan ophiolites. Current models propose that most of the East Tethyan oceanic lithosphere was subducted within a single subduction zone, active during the Middle or Late Cretaceous, which was completed during the Paleogene collision between India and Asia. The Early Cretaceous sedimentary Giabulin Formation in southern Tibet, includes conglomeratic members that contain ultramafic and mafic plutonic pebbles, as well as radiolarian chert clasts, that record the erosion of oceanic lithosphere involved in a subduction event which occurred earlier than previously believed. Geochemical analyses, mineral chemistry, stratigraphic chronology, and sedimentary analysis, including source provenance, suggest that the pebbly conglomerate was formed through erosion of an unknown ophiolitic source that was geochemically distinguishable from the Xigaze ophiolites within the Yarlung‐Zangbo Suture Zone, southern Tibet. We infer the existence of an older ophiolitic source, termed the Yarlung‐Zangbo paleo-ophiolite, that was dismembered and eroded during an earlier subduction stage not taken into account in current models. q 2000 Elsevier Science Ltd. All rights reserved.

Although the identification and characterization of limb load asymmetries during quiet standing has not received much research attention, they may greatly extend our understanding of the upright stance stability control. It seems that the limb load asymmetry factor may serve as a veridical measure of postural stability and thus it can be used for early diagnostic of the age-related decline in balance control. The effects of ageing and of vision on limb load asymmetry (LLA) during quiet stance were studied in 43 healthy subjects (22 elderly, mean age 72.3+/-4.0 yr, and 21 young, mean age 23.9+/-4.8 yr). Postural sway and body weight distribution were recorded while the subject was standing on two adjacent force platforms during two 120 s trials: one trial was performed with the eyes open (EO), while the other trial was with the eyes closed (EC). The results indicate that LLA was greater in the old adults when compared with the young control subjects. The LLA values were correlated with the postural sway magnitudes especially in the anteroposterior direction. Eyes closure which destabilized posture resulted in a significant increase of body weight distribution asymmetry in the elderly but not in the young persons. The limb load difference between EO and EC conditions showed a significantly greater effect of vision on LLA in the elderly compared to the young subjects. The observed differences in the LLA may be attributed to the decline of postural stability control in the elderly. Ageing results in the progressive decline of postural control and usually the nervous system requires more time to complete a balance recovery action. To compensate for such a deficiency, different compensatory strategies are developed. One of them, as evidenced in our study, is preparatory limb unload strategy (a stance asymmetry strategy) which could significantly shorten reaction time in balance recovery.

Upper-mantle tectonites forming the basal part of the North Arm Mountain (NAM) massif ophiolitic sequence are dominantly refractory harzburgites, grading upward to Iherzolites near the contact with the overlying crust, and downward to coarse-grained lherzolite close to the metamorphic sole. The tectonites are cut by numerous pyroxenitic dykes ranging from orthopyroxenite, to websterite, to clinopyroxenite, and containing variable amounts of olivine, spinel and disseminated FeNi-sulphides. Microprobe traverses were executed from the core to the rim of several pyroxenite dykes, through the wallrock peridotites and into distal host peridotites. Wallrock peridotites recorded complex mineral modal and chemical variations suggesting that major dissolution-precipitation reactions occurred between minerals of the wallrock peridotites and intrusive melts, involving CrAl and MgFe solid solution exchanges between olivines, pyroxenes, spinels and migrating melts, and selective dissolution of clinopyroxene from wallrock peridotites into migrating melts. There is a general trend of modal clinopyroxene increase and FeAl enrichment among minerals of the pyroxenites along the mantle section, from deeper orthopyroxenites toward websterites and clinopyroxenites located near the crust-mantle interface. This suggests that clinopyroxene-bearing intrusions crystallized from the most evolved members of magmas related to the pyroxenites. Fractionation and interaction processes could both have led NAM migrating melts to Al2O3 and FeO enrichment, and CaO enrichment leading towards saturation in clinopyroxene. Magma compositions that would be in equilibrium with intro-mantle intrusive pyroxenites show similarities in composition and evolutionary trends with western Pacific boninites and high-Mg# andesites. If this interpretation is correct then the NAM ophiolitic massif would bear an intraoceanic fore-arc component. We suggest that modern boninites may partly have inherited their unusual magma chemistry by similar interactions and continuous re-equilibration with upper-mantle rocks during their ascent through the mantle wedge above a subduction zone.

Our objectives were (1) to analyze the refusal bias associated with postal questionnaires and face-to-face interviews and (2) to compare responses elicited from a postal questionnaire with those provided by a face-to-face interview in subjects over 75 years of age. Our methods included a postal questionnaire sent to a representative sample of community-dwelling elderly individuals (n = 842). All subjects were also invited to participate in an in-home interview conducted by a trained nurse. One hundred and six subjects (12.6%) were nonrespondents to the postal questionnaire. These nonrespondents were more cognitively impaired, more disabled, and showed a higher 1-year mortality rate (13.2 versus 5.2%) than respondents. Late respondents who needed a reminder letter were similar to nonrespondents. One hundred and eighty-seven subjects (22.2%) refused to participate in the home interview. These nonparticipants were similar to the participants on age, sex, 1-year mortality rate, and responses given to all but two postal questions. Comparison of postal questionnaire responses and face-to-face responses revealed that agreement was substantial to moderate for factual information (kappa = 0.41 to 0.80) but poor for clinical information (depression, cognitive impairment, disability). A short index including age, sex, and six questions on disability was useful in identifying disabled subjects by a postal questionnaire. Our conclusion is that nonresponse bias is evidenced when postal questionnaires are utilized in the very elderly population and caution should be used when interpreting health data obtained by this technique. Refusal bias from face-to-face interviewing is less important in this population.

Objectives: Objectives of this study were to develop normative data for the Test d'Evaluation des Membres Superieurs de Personnes Agees (TEMPA) and determine its relation to upper extremity sensorimotor parameters such as fine and gross dexterity, coordination, strength, endurance, range of motion, and several types of sensibility. Design: Cross-sectional study. Setting: Community-dwelling subjects. Participants: Three hundred sixty healthy subjects randomly recruited by age and sex strata (60 to 69, 70 to 79, and 80 or older). Main Outcome Measures: Length of execution of the tasks in the TEMPA. Results: Normative data are reported by gender and age group. The time taken to execute the tasks increased significantly with age. The women were faster on the tasks requiring a higher degree of fine dexterity, whereas the task requiring a lesser degree of fine dexterity and sensibility and more grip strength was accomplished faster by the men. Subjects who were more active and described themselves as being in excellent or good health performed better. Conclusion: The norms will help clinicians differentiate better between normal and pathological aging in upper extremity performance.

Manual dexterity is a skill frequently evaluated in rehabilitation to estimate hand function. Several tests have been developed for this purpose, including the Box and Block Test (BBT) that measures gross manual dexterity. The goal of the present study was to verify the test-retest reliability and construct validity of the BBT with subjects aged 60 and over with upper limb impairment. The second objective of this research was to develop normative data based on a random sample of healthy elderly community-living individuals. The results show that the test-retest reliability is high (intraclass correlations coefficients of 0.89 to 0.97) and the validity of the test is shown by significant correlations between the BBT, an upper limb performance measurement and a functional independence measurement. The norms will help rehabilitation clinicians to differentiate better between real difficulties and those that may be attributed to normal aging.

The 130 km long Garrett transform fault, which offsets two ultrafast (14.5 cm/yr) EPR spreading segments, is the site of volcanic and tectonic activity. Evidence for recent volcanic events was observed during several dives on oblique ridges (3100–3500 m high) trending 040° (Alpha, Beta and Gamma), and on small constructional mounds located in the central transform basin and eastern valley at a depth of 3500–5000 m. The constructional features show a fissured terrain, suggesting a component of lithospheric opening. The strike-slip motion of the transform is inferred at several locations between the two EPR-transform intersection zones, from the presence of abundant sediment-free talus with crushed rock debris, fresh scarps, and well-developed striations on outcrops of serpentinized peridotites and metamorphosed volcanic breccia. The width of the active tectonic zone varies between 200 and 3000 m in the explored area near the eastern and western EPR-transform intersection zones, along the E-W trending Median Ridge walls in the eastern and western transform troughs of the central basin and at several sites on the south-facing wall of the transform domain first escarpment. The presence of recent volcanic activity implies that the Garrett transform behaves as a leaky transform fault. The most common volcanics, consisting of plagioclase and olivine phyric lava erupted in the transform, are compositionally more depleted [ K/Ti< 0.08 ] and less evolved (Mg#60–70) than the basalts encountered on the southern EPR segments [Mg#40–66, and K/Ti= 0.05–0.25 ]. This suggests that different magmatic conditions are operating in the transform domain. The transform strike-slip motion is responsible for the emplacement of a sliver of serpentinized peridotite located in an area about 2 km wide and 10 km long along the Median Ridge at the contact with outcrops of metamorphosed basaltic breccia. The ultramafics consist of residual harzburgites, often impregnated with irregular lenses and dykes of basaltic liquids (plagioclase-wehrlite and gabbro), and are found associated with troctolites, dunite and gabbros. The emplacement of the ultramafics and their gabbroic inclusions has resulted in the presence of metamorphosed tectonic breccia forming part of the Median Ridge in the central transform basin.

The microstructural study of a set of serpentinized ultramafic samples dredged in the Garrett transform fault, shows that these rocks have been deformed plastically at temperatures probably in excess of 1000°C, and under moderate deviatoric stresses (below 1 kbar). Such temperature and stress conditions probably prevail in the asthenosphere, or in the deepest and hottest part of the lithosphere below the ridge. The deformed paragenesis of the studied samples belong to two groups: harzburgites with petrological characteristics typical of residual mantle; and plagioclase-dunites. A melt circulated in these two groups of deformed ultramafic rocks at the end of their deep-seated plastic deformation. This melt crystallized plagioclase, clinopyroxene, and also possibly orthopyroxene in one sample, in dykelets, and in interstices between the minerals of the deformed host rock. The deformation and magmatic impregnation history of the studied ultramafic samples recall the results of on-land studies of the crust-mantle transition zone of ophiolitic massifs. This suggests that our set of samples may represent fragments of the East Pacific Rise crust-mantle transition zone. The deformed ultramafic paragenesis of these samples was chemically modified by interactions with the impregnating melt: the deformed spinel was enriched in TiO2 and Cr2O3, the deformed clinopyroxene and orthopyroxene of the harzburgitic samples were also enriched in TiO2, and the orthopyroxene was significantly depleted in Al2O3. The high mobility of titanium during the impregnation process suggests that the Ti content of a melt, often used as an indicator of its degree of evolution, or of the degree of partial melting undergone by its source rock, may also be modified by melt/rock interactions during the circulation of the magma through the crust and upper mantle.

This paper presents the first detailed mineralogical record of ophiolitic plutonic rocks in the Thetford Mines-Asbestos area, Quebec. The plutonic rocks form the lower 5.5-km section of the 8-km-thick Thetford Mines Ophiolite. The ophiolitic cumulate sequence is in tectonic contact with underlying thick, plastically deformed, harzburgitic peridotite now largely serpentinized. The mineralogy of this peridotite is a typical example of a very depleted ultramafic rock since the minerals are poor in hygromagmaphile elements and enriched in the high-partition-coefficient elements (Ni, Cr) and Mg. The cumulates form a rock suite varying from the bottom to the top of the sequence as follows: dunite, chromitite, wehrlite, clinopyroxenite, hornblende gabbro. Olivine from the very base of the sequence is highly magnesian (Fo91–94) and Ni-rich (NiO: 0.30-0.41 wt.%). Chromite grains are characterized by high Cr# (0.60-0.87) and varying Mg# (0.30-0.62) related to host-rock composition and higher Fe3+# than harzburgite spinels. The TiO2 content is usually very low ( Calculations using mineral chemistry data suggest that the primitive liquid which was in equilibrium with early fractionated minerals, was highly magnesian, Ni- and Cr-rich and conversely TiO2-and alkali-poor. This composition is comparable to that of the boninitic lavas of the lower volcanic group overlying the gabbroic rocks. By taking into account subsolidus re-equilibration it is possible to recalculate an average primitive magma composition. The genesis of this liquid results from a 20–30% partial melting of a source depleted in hygromagmaphile elements. It is concluded that both magmatic processes and source composition are responsible for the genesis of low-TiO2 magnesian liquids and that these conditions may not be restricted to a single geodynamic environment. Paleogeographic reconstructions of Appalachian terranes in Cambrian-Ordovician times, the occurrence of boninitic lavas and low-Ti cumulate sequence constrain the formation of the Thetford Mines ophiolite in a marginal basin or the frontal arc region of an island-arc system. It is stressed that geodynamic significance of such liquids must be considered in relation to a geological context in order to ascertain their real implication.

The Early to Middle Ordovician Quebec Appalachian ophiolites contain three geochemically distinct groups of extrusive and intrusive rocks. The predominant group consists of Ni- and Cr-rich olivine-clinopyroxene phyric lavas and dikes grading in composition from basalt and andesite to rhyodacite. These rocks are geochemically similar to arc-related boinites. They are closely associated, at the base of the extrusive sequence, with aphyric lavas and dikes which have geochemical affinities with volcanic arc basalts. The third group is restricted to a single locality, Mount Orford, at the southwestern end of the ophiolite belt. It consists of alkaline diabases occurring in interdigitation with arc basaltic diabases to form a 1000-m-thick sheeted sill complex. The Thetford Mines ophiolite is interpreted to be typical of ocean crust created by fore-arc rifting in a subduction zone environment. The Mount Orford ophiolite, with its alkaline rocks, is considered to be remnant of the back-arc section of the same island-arc system.

The paper presents the mineralogy of upper-mantle tectonites and associated lower-crustal ultramafic and mafic cumulates from the Jurassic Northern Apennine ophiolites (NAO) in a comparison assay with equivalent rocks from the major oceanic basins (MOB: East Pacific Rise and Atlantic fracture zones, Legs 37 and 45). Among the mantle rocks both tectonite lherzolites and harzburgites have been so far widely found in MOB whereas lherzolites largely prevail in NAO. The Mg# [ Mg # = Mg ( Mg + Fe 2+ ) ] range in mafic minerals in NAO tectonites is restricted to high values (Ol: 88–90; Opx: 90–92; Cpx: 91–93). Cr-spinels show large variation of the Cr# [ Cr ( Cr + Al ) ] ratio found in spinels from lherzolites and very rare Cpx-bearing harzburgites (Cr# 10 and 15, respectively). The varied compositions largely reflect the relative greater degree of partial melting that affected MOB tectonites compared to NAO tectonites. From a restored stratigraphic log of the NAO cumulates the order of appearance of the cumulus phases both in NAO and MOB cumulates is: Ol + Chr, Pl, Cpx, Opx, Fe/1bTi-oxides, Ap. The sequence gave rise to the following main lithotypes: dunites, troctolites, minor wehrlites, Ol-gabbros, gabbronorites, ferrogabbros and ferrodiorites. The olivine from early ultramafic cumulates has high Fo content (Fo90 for NAO, Fo91 for MOB) with a NiO content ranging from 0.21 to 0.31 wt.%. Cr-diopside generally shows higher TiO2 than found in tectonite peridotites. The coexisting spinel is typically a Ti-chromite with high Cr# (43–60). The most Mg-rich olivine coexisting with An-rich plagioclase in the most primitive cumulates are Fo88 and An72 and were in equilibrium with a basaltic melt. These facts coupled with the lack of intense plastic deformation in the early cumulates allow us to exclude a high-pressure fractionation system. Formation of very little volume percent of amphibole indicates a very low H2O activity in the magma. Starting from the early fractionating cumulus phases a recalculated primary magma composition is proposed. From these calculations it is concluded that NAO cumulates derived from a tholeiitic basalt liquid similar to primitive MOB liquid except for a higher Na2O content. In particular present-day analogues are found among high Na2O mid-ocean ridge basalts from the Mid-Cayman Rise and Southwest Indian Ridge. The composition of calculated primary magmas indicated for NAO: (1) a much lower degree of melting than average MOB, also sustained by evident differences in residual peridotites; (2) a crustal thickness of ∼ 2–3 km, also supported by the reconstructed maximum thickness of crustal sequences of 2 km; (3) a spreading axis with an average water depth of ∼ 5 km. By analogy with the Mid-Cayman Rise and Southwest Indian Ridge, half spreading rates of

Serpentinized peridotites, metagabbros and fresh basaltic rocks were dredged from the Garret Transform Fault near 13°S on the East Pacific Rise. Two dredge hauls taken on the northern wall (from about 3100–3600 m) consisted of aphyric and picritic basalts; while peridotites, gabbros and moderately phyric basalts were recovered in a single dredge located near the deepest part (4616–4820 m) of the transform valley. Well preserved igneous textures and mineralogical assemblages enable us to differentiate between tectonites (including harzburgites and clinopyroxene-bearing harzburgites) and cumulates (consisting of plagioclase-dunite, troctolites, olivine-gabbros and ilmenite-gabbros). The harzburgites are likely to represent deep-seated peridotites left after extraction of basaltic melt during upper mantle partial melting of a lherzolite. The ultramafic cumulates underwent some deformation and show textural and mineralogical evidences which suggest formation at a minimum depth corresponding to the very lower crust. It is also inferred that the composition of the coexisting liquid along with early cumulus crystals has a ratio Mg/(Mg + Fe2+) of 0.7, high CaO/Na2O ratios and a low Ni content (about 150 ppm) when compared to similar rock types from Atlantic fracture zones. Subsequent uplift during rifting of the oceanic lithosphere enhanced plastic deformation, subsolidus recrystallization and retrogressive metamorphism of the gabbros and the ultramafics.