Pb isotopic evidence for early Archaean crust in South Greenland

The results of an isotopic remote sensing study focussed on delineating the extent of Early Archean crust north and south of the Nuuk area and in south Greenland is presented. Contamination of the Late Archean Nuk gneisses and equivalents by unradiogenic Pb uniquely characteristic of Amitsoq gneiss was detected as far south as Sermilik about 70 km south of Nuuk and only as far north as the mouth of Godthabsfjord. This study was extended to the southern part of the Archean craton and the adjoining Early Proterozoic Ketilidian orogenic belt where the Pb isotopes suggest several episodes of reworking of older uranium depleted continental crust. The technique of using the Pb isotope character of younger felsic rocks, in this case Late Archean and Early Proterozoic gneisses and granites to sense the age and isotopic character of older components, is a particularly powerful tool for reconstructing the evolutionary growth and development of continental crust

Controlling and enabling practices to manage supply in online service triads

Purpose: The purpose of this paper is to understand which controlling and enabling practices are used, how the numerous supplying partners are managed and how positive network effects are generated in online service triads (multi-sided platform – supplying partners – consumers). Design/methodology/approach: A single representative in-depth case study was conducted to refine theory on managing service triads. The main data source consists of field notes collected by one author, who held a temporary position within the organization. Additional data were collected from observations, internal documents, informal talks and 20 interviews. Findings: The authors found controlling and enabling organizational practices in four main categories on two levels as follows: managing network composition (system level), managing order fulfillment and returns (operations level), category management (both levels) and capability enhancement (both levels). Research limitations/implications: The authors show that both controlling and enabling practices are present in online service triads. This enables platform owners and supplying partners to share responsibilities for creating positive network effects, i.e. to increase scale, which increases value, which again attracts more suppliers and consumers, which creates more value, etc. Practical implications: The authors present a range of and controlling and enabling practices that describe how multi-sided platforms can manage numerous supplying partners in an online context. Originality/value: This study is the first to show that contractual and relational governance is insufficient in service triads in online settings with numerous supplying partners. Further, the authors provide empirical evidence that supply networks continuously adapt over time

Annual incidence rates of hip symptoms and three hip OA outcomes from a U.S. population-based cohort study: the Johnston County Osteoarthritis Project

Estimate annual incidence rates (IRs) of hip symptoms and three osteoarthritis (OA) outcomes (radiographic, symptomatic, and severe radiographic) overall and by race, sociodemographic characteristics, and hip OA risk factors

Greenland from Archaean to Quaternary, Descriptive text to the 1995 Geological Map of Greenland 1:2 500 000, 2nd edition

The geological development of Greenland spans a period of nearly 4 Ga, from Eoarchaean to the Quaternary. Greenland is the largest island on Earth with a total area of 2 166 000 km2, but only c. 410 000 km2 are exposed bedrock, the remaining part being covered by a major ice sheet (the Inland Ice) reaching over 3 km in thickness. The adjacent offshore areas underlain by continental crust have an area of c. 825 000 km2. Greenland is dominated by crystalline rocks of the Precambrian shield, which formed during a succession of Archaean and Palaeoproterozoic orogenic events and stabilised as a part of the Laurentian shield about 1600 Ma ago. The shield area can be divided into three distinct types of basement provinces: (1) Archaean rocks (3200–2600 Ma old, with local older units up to >3800Ma) that were almost unaffected by Proterozoic or later orogenic activity; (2) Archaean terrains reworked during the Palaeoproterozoic around 1900–1750 Ma ago; and (3) terrains mainly composed of juvenile Palaeoproterozoic rocks (2000–1750 Ma in age).Subsequent geological developments mainly took place along the margins of the shield. During the Proterozoic and throughout the Phanerozoic major sedimentary basins formed, notably in North and North-East Greenland, in which sedimentary successions locally reaching 18 km in thickness were deposited. Palaeozoic orogenic activity affected parts of these successions in the Ellesmerian fold belt of North Greenland and the East Greenland Caledonides; the latter also incorporates reworked Precambrian crystalline basement complexes. Late Palaeozoic and Mesozoic sedimentary basins developed along the continent–ocean margins in North, East and West Greenland and are now preserved both onshore and offshore. Their development was closely related to continental break-up with formation of rift basins. Initial rifting in East Greenland in latest Devonian to earliest Carboniferous time and succeeding phases culminated with the opening of the North Atlantic Ocean in the late Paleocene. Sea-floor spreading was accompanied by extrusion of Palaeogene (early Tertiary) plateau basalts in both central West and central–southern East Greenland. During the Quaternary Greenland was almost completely covered by ice, and the present day Inland Ice is a relic from the Pleistocene ice ages. Vast amounts of glacially eroded detritus were deposited on the continental shelves around Greenland. Mineral exploitation in Greenland has so far encompassed cryolite, lead-zinc, gold, olivine and coal. Current prospecting activities in Greenland are concentrated on gold, base metals, platinum group elements, molybdenum, iron ore, diamonds and lead-zinc. Hydrocarbon potential is confined to the major Phanerozoic sedimentary basins, notably the large basins offshore North-East and West Greenland. While reserves of oil or gas have yet to be found, geophysical data com bined with discoveries of oil seeps onshore have revealed a considerable potential for offshore oil and gas

Palaeoproterozoic and Archaean gneiss complexes in northern Greenland: Palaeoproterozoic terrane assembly in the High Arctic

The Precambrian shield of northern Greenland has been investigated by SHRIMP U-Pb zircon dating of 14 orthogneisses and granitoids plus 5 metasediments, integrated with mapping by the Geological Survey of Denmark and Greenland and whole-rock Nd isotopic studies. The Inglefield Mobile Belt is a tract of Palaeoproterozoic sedimentation, plutonism, polyphase deformation and high-grade metamorphism that underlies Inglefield Land and northern Prudhoe Land. In the southern part of the belt at 78 degrees 30\u27N, the E-W-trending Sunrise Pynt Straight Belt is a high-grade, but structurally late, shear zone with contrasts in the geology on either side. South of the Sunrise Pynt Straight Belt, ca. 1980 Ma diorites and tonalites were emplaced into older orthogneisses and metasediments. Detrital zircons from two metaquartzites (deposited on Archaean basement?) yielded complex age spectra from ca. 3250 Ma to 2350 Ma, with 2600-2450 Ma grains dominant. In associated mica schist, low Th/U, 1923 +/- 8 Ma zircons date high-grade metamorphism. The most southern orthogneiss investigated (77 degrees 45\u27N) is Neoarchaean (ca. 2600 Ma), in agreement with previously published isotopic data. North of the Sunrise Pynt Straight Belt to 79 degrees 10\u27N an amphibolite-granulite-facies complex with extensive pelitic to psammitic paragneisses are the oldest rocks recognised. Two psammitic paragneisses yielded unrounded zircons with a unimodal detrital age population centred on 2000-1980 Ma. Their source could be ca. 1980Ma orthogneisses from south of the Sunrise Pynt Straight Belt, or from basement inliers in the North-East Greenland Caledonian fold belt. The metasediments were intruded by tonalites and diorites with dates of 1949 +/- 13 Ma and 1943 +/- 11 Ma, and then by granitoids (free of zircon inherited from older rocks) with ages of 1924 +/- 29 Ma to 1915 +/- 19 Ma. The metasediments show development of low Th/U zircon overgrowths at ca. 1920 Ma, coeval with the granitoids. Finally, other granites, some locally transformed into gneisses, have ages of 1783 +/- 22 Ma to 1741 +/- 15 Ma. Inherited zircons in the latter are up to 2650 Ma old. A granite dyke with a zircon age of 1783 Ma has an T(DM) age of 2981 Ma and a strongly negative epsilon(Nd) at 1.78 Ga, indicating derivation by melting or reworking of Archaean crust. Thus, by 1800 Ma this juvenile Palaeoproterozoic, terrane had probably over-ridden crust with Archaean components. North of Inglefield Land, Precambrian crystalline rocks are obscured until Victoria Fjord (81 degrees 30\u27N). One reconnaissance orthogneiss sample from there contains ca. 3400 Ma oscillatory-zoned zircons, which probably date the rock, rather than being a xenocrystic component in a younger rock. Thus, from north to south there is an assemblage of Archaean, Palaeoproterozoic and Archaean to early Palaeoproterozoic gneiss terranes. The Inglefield Mobile Belt is dominated by juvenile Palaeoproterozoic arc crust trapped between two unrelated blocks of Archaean crust of contrasting age. The collision, and probably thrusting of a Palaeoproterozoic arc over a southern Archaean foreland, occurred at ca. 1920Ma-dated by metamorphic zircon. The new isotopic results consolidate the regional mapping of Archaean and Palaeoproterozoic complexes across northern Baffin Bay that show continuity from Canada into Greenland, without displacement across the Nares Strait. (C) 2007 Elsevier B.V. All rights reserved

A chapter from the syntax of Istrian Čakavian: the usage of verb forms

U radu se analizira glagolski sustav u “sjeverozapadnočakavskim govorima” Istre. Obrađuju se inovacije u odnosu na praslavenski glagolski sustav i ističu razlike u funkcioniranju i uporabi glagolskoga sustava u istarskim čakavskim govorima i standardnome hrvatskom jeziku.The article deals with the usage of verb forms in the so-called North West Čakavian dialects of Istria (the term ‘North West Čakavian’ referring to those dialects with examples of neocircumflex: a long falling vowel in adjectives and e-presents belonging to Stang’s accentuation type (a), e.g. Žminj stari, plačen, cf. Vermeer 1982: 290-293 and 316-320). Of the five areas in Istria where such dialects are spoken, examples for this article are taken from the author’s field work data gathered in three of them: the areas around Žminj, Pazin and Labin. The dialects from these areas are closely related, and have very similar verbal systems. An inventory of verb forms for the dialect of Orbanići in the Žminj area is given, followed by a short overview of the usage of the present in main sentences, and the usage of analytic verb forms, for all three areas. Some of the most striking features of the verbal system of these dialects, also some of the features wherein Istrian čakavian distinctly differs from literary Croatian, are the usage of the negated perfective present expressing a negative potential, and the existence of a considerable number of constructions which can express a habitual action, e.g. the perfective present, the perfective perfect, the conditional II, and especially a separate habitual Aktionsart as a productive category in the infinitive, the present and the active participle, e.g. se igrieva ‘(she) is in the habit of playing’ vs. se igra ‘(she) plays, (she) is playing’