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Two pairs of high-field-strength elements (NbTa and ZrHf) display contrasting behaviour during the evolution of a peraluminous granitic pluton that is composed of leucomonzogranites and subordinate greisen-hosted topaz-bearing leucogranites. Zr and Hf progressively decrease with differentiation and their ratio remains the same, close to the chondritic value (∼ 36). The crystallization of zircon which contains the bulk of these two elements in the rocks, does not modify the Zr/Hf ratio. With increasing differentiation, Nb and Ta show an increase accompanied by a distinct decrease of the Nb/Ta ratio from 14 in leucomonzogranites to 2 in leucogranites and greisens. Tantalum correlates positively with Rb, Li and F and is strongly enriched in the evolved rocks, implying that an addition of internally derived mineralizing fluids and fluid fractionation played a key role in the variation of the Nb/Ta ratio in rocks with K/Rb ratios < 150. The values of the Nb/Ta ratio in the continental crust are typically lower than those of mantle and chondrites (∼ 17.5) suggesting that fluid fractionation might have been an important process during the evolution of the continental crust.

Evaluates 11 models of high-performance cross-country boots. Salomon Nordic System (SNS) Profil; New Nordic Norm (NNN) boot/binding system; SNS Profil sport system; Jalas 610; Salomon SR 511; Alfa Voss; Rossignol LTS; More.

Discusses the newest Nordic skis, boots and bindings as part of the `Skiing Magazine' Buyer's Guide '91. Rossignol Carbon SDC waxless ski; Fischer RCS Skating Graphite ski; Salomon SR Profil Automatic binding; Rottefella NNN bootbinding system; Poles.

Gives field-test results on several brands of cross-country skating ski boots and bindings. Interface between sole and binding; How the boots were tested; Salomon 911 Equipe Skate; Hartjes XC 2000; Tyrolia TXC 509 RF; More. INSET: What we did.;What we wish we had done (problems during testing)..

Discusses spring heli-skiing in Quebec's Chic-Choc mountains on the Gaspe Peninsula. Heli-Ski Chic-Chocs, operating out of St.-Octave-de-l'Avenir, Que.; Ouellet Bowl; Mount Logan; Mount Albert; Travel information. INSET: How high is tree line?, by J. Chase..

Gives an overview of Nordic skiing equipment for 1990. Boots and bindings for racing and backcountry skiing; Many types of skis; Poles.

Gives advice to Alpine skiers who want to begin cross-country skiing. How to choose skis; Technique, including double poling and skating; Parallel turns.

Presents the newest Nordic skis for 1989 as part of the 1989 Buyer's Guide. Brand names; Prices; Types of skis; Light touring; Stride/skate crossover; Waxless touring skis; Telemark/backcountry; Boots; Poles.

The Proterozoic Flin Flon Domain of the Trans-Hudson Orogen (Churchill Province of the Canadian Shield) which contains a significant amount of volcanic rocks dated at 1,886 Ma and hosts two major mining districts, is similar to Archean greenstone belts. The volcanic rocks include island arc tholeiitic (IAT) and volumetrically less important MORB-like suites. The IAT suite ranges from basalt to rhyolite and represents a differentiation sequence with a predominance of mafic types. Compared to typical Archean greenstone belts, the IAT are more depleted in incompatible trace elements and resemble modern island arc tholeiitic sequences. The arc volcanism progressively evolved to more advanced stages characterized by the presence of calc-alkaline island arc volcanics. The basalt group which resembles E-type MORB was derived from a garnet peridotite source whereas the other MORB-like basalts were generated at a shallower depth (in the spinel stability field). The association of IAT with MORB-like tholeiites suggests that the volcanism occurred in a back-arc setting and the compositional variations of the MORB-like basalts can be attributed to melting of a rising mantle diapir during back-arc spreading.

Abstract: The Neoproterozoic Ougda magmatic complex occurs within platformal carbonate rocks in the western part of the Pan-African fold belt of the Tuareg shield (NW Africa). It is composed of - 800 Ma old, relatively high P-T (i.e., Grt + Cpx-bearing: P > 5 kbar; T≈900'Q, tholeiitic mafic/ultramafic cumulates and related rocks intruded by intermediate to mafic calcalkali plutons (e.g., Cpx+Hbl-bearing gabbro) and dikes. Apparent contrasts in structural level of crystallization indicate that the calc-alkali rocks are significantly younger than the tholeiites, which temporally correlate with a period of regional extension in this part of Africa. Intrusion of the calc-alkali rocks may have occurred during the formation of an arc after the tholeiitic rocks had been (diapirically?) emplaced within the shelf carbonates, and prior to (> 630 Ma) the Pan-African orogeny. Data reported herein indicate that the Ougda complex records the inception and demise of a Neoproterozoic ocean basin. Similar crustal sections have been described from collisional (e.g., Aleutian islands) and extensional (e.g., Ivre-Verbano zone) settings, indicating that processes operating in both environments can generate nearly indistinguishable igneous suites; the prevalence of shallow-level calc-alkali rocks in both settings may mask the presence of more mafic, tholeiitic rocks at depth.

AbstractThe spinel peridotite inclusions in basalts from Sardinia are upper-mantle residues affected by metasomatism which led to an enrichment particularly of U and light REE. The metasomatism took place prior to the recrystallization which produced the primary mineral assemblage of the inclusions. The compositional variations imply that the xenoliths are residual after at least two melting events.

AbstractUltramafic xenoliths enclosed in Plio-Quaternary alkali basalts from Tallante near Cartagne (southern Spain) are composed mainly of spinel lherzolites which are probably upper mantle residues. In many xenoliths, the spinel lherzolite is cut by pyroxenite or gabbroic anorthosite veinlets generally 0.2–3 cm thick. The clinopyroxenite veinlets were formed by high-pressure crystal-liquid segregation from alkali basalt magmas formed earlier than the host basalts, whereas mantle metasomatism played a role in the genesis of gabbroic anorthosites. Close to the contact with the veinlets, the spinel lherzolites are enriched in Ca, Fe, and some incompatible elements including light REEdue to the migration of a fluid from the veinlets into the surrounding lherzolites. The host alkali basalts were derived from a heterogeneous, incompatible element-enriched upper-mantle source probably similar in composition and nature to the composite xenoliths, but were formed in a garnet stability field.

Gabbroic bodies in the Bralorne-Gold Bridge area of southwestern British Columbia are associated with the oceanic Bridge River complex of the western Canadian Cordillera, one of the “suspect” terranes accreted to North America in the Jurassic. The gabbros are locally cut by tonalites and are structurally interleaved with ultramafic rocks, phyllites, graphitic cherts, and carbonate lenses that comprise the lower part of the Bridge River complex. Their late Carboniferous crystallization age overlaps the depositional age of affiliated supracrustal rocks (Mississippian-Jurassic), some of which have been metamorphosed to blueschist facies. Compositionally, the gabbros resemble mafic plutonic rocks of ophiolitic complexes and gabbroic rocks of the nearby Shulaps Range. They display some affinity to oceanic island arc tholeiitic suites. The Bralorne and Shulaps gabbros include cumulates and appear to have been derived from a single, light REE-depleted, peridotitic source by melting and subsequent fractional crystallization/accumulation of various combinations of plagioclase, pyroxenes, and olivine. The tonalites are compositionally distinct from typical ophiolitic plagiogranites, but might be related to the associated gabbros. The gabbroic bodies occur within tectonic slivers derived from the oceanic crust that floored a deep ocean basin that existed during the late Paleozoic and early Mesozoic. The Bridge River complex comprises fragments of oceanic crust that were tectonically incorporated into an east-verging accretionary prism during a middle/late Triassic to Jurassic collisional event.

The Alpine peridotite massif of Lanzo (Italy) contains three generations of basic dikes (gabbros and basalts). The older gabbros are plagioclase-rich mantle segregates while the younger gabbro dikes are cumulates very similar in chemical composition to recent oceanic gabbros and gabbros from ophiolitic complexes. They both were derived from the N-type mid-ocean ridge basalt (MORB) magmas which were progressively more depleted in incompatible elements and were probably generated during a dynamic melting of a rising mantle diapir. The basaltic dikes are the N-type MORB and closely resemble the Alpine-Apennine ophiolitic basalts. They were derived from a different upper mantle source than the parental magmas of the gabbros. The source of the basalts was less depleted in light REE. The presence of basic magmas with N-type MORB affinities in the Lanzo massif is consistent with the close genetic relationship between the Alpine peridotite body and the ophiolites of the Liguro-Piemontese basin.

The structure of sanguinarine free base was examined. The base is either bis[6-(5,6-dihydrosanguinarinyl)] ether (3) or bis[6-(5,6-dihydrosanguinarinyl)]amine (4) depending on whether Na2CO3 or NH3, respectively, is used as an alkalizing agent. Oxysanguinarine (5) was identified as a side product formed by disproportionation of the pseudobase intermediate 2a.

The northeast part of the Czech Republic (Moravia) and the adjoining part of Poland host a 100-km-long and 15- to 25-km-wide belt containing numerous isolated bodies (mainly sills) of lamprophyre of Lower Cretaceous age. The lamprophyres range from mafic (melanocratic) to evolved, feldspar-rich (mesocratic) variants. Mineralogically, they are characterized by compositionally zoned kaersutite phenocrysts, biotite and high Al–Ti salitic to diopsidic clinopyroxene. The lamprophyres are typically alkaline as shown by high contents of P2O5, TiO2, alkalies and incompatible trace elements such as light REE, Zr, Nb, Y, Ba and Sr, and by high Ti/V (>50) and chondrite-normalized (La/Yb)n (8–25) ratios. They resemble alkali basalts, basanites and nephelinites. Major element composition and trace element patterns and Nd–Sr isotopic values (εNd ca. +5.5 to +6.6 and εSr ca. –9.5 to –24.0) indicate that the lamprophyric magma was derived from a mantle source that was compositionally similar to the source of ocean island basalts with HIMU affinities and some continental extension-related alkali basaltic suites. The lamprophyres do not show any subduction imprint. They were generated in the garnet stability field by a variable degree of melting. Evolved lamprophyres were formed by clinopyroxene-dominated fractional crystallization of mafic lamprophyric magma. The lamprophyres are interpreted to have been emplaced along conduits formed during the formation of a basin/graben structure in the Early Cretaceous. [ABSTRACT FROM AUTHOR]

Gabbroic bodies in the Bralorne-Gold Bridge area of southwestern British Columbia are associated with the oceanic Bridge River complex of the western Canadian Cordillera, one of the 'suspect' terranes accreted to North America in the Jurassic. The gabbros are locally cut by tonalites and are structurally interleaved with ultramafic rocks, phyllites, graphitic cherts, and carbonate lenses that comprise the lower part of the Bridge River complex. Their late Carboniferous crystallization age overlaps the depositional age of affiliated supracrustal rocks (Mississippian-Jurassic), some of which have been metamorphosed to blueschist facies. Compositionally, the gabbros resemble mafic plutonic rocks of ophiolitic complexes and gabbroic rocks of the nearby Shulaps Range. They display some affinity to oceanic island arc tholeiitic suites. The Bralorne and Shulaps gabbros include cumulates and appear to have been derived from a single, light REE-depleted, peridotitic source by melting and subsequent fractional crystallization/accumulation of various combinations of plagioclase, pyroxenes, and olivine. The tonalites are compositionally distinct from typical ophiolitic plagiogranites, but might be related to the associated gabbros. The gabbroic bodies occur within tectonic slivers derived from the oceanic crust that floored a deep ocean basin that existed during the late Paleozoic and early Mesozoic. The Bridge River complex comprises fragments of oceanic crust that were tectonically incorporated into an east-verging accretionary prism during a middle/late Triassic to Jurassic collisional event. [ABSTRACT FROM AUTHOR]