Multistage growth and reworking of the Palaeoproterozoic crust in the Bergslagen area, southern Sweden: evidence from U–Pb geochronology

2006 ◽  
Vol 143 (5) ◽  
pp. 679-697 ◽  
Author(s):  
ULF B. ANDERSSON ◽  
KARIN HÖGDAHL ◽  
HÅKAN SJÖSTRÖM ◽  
STEFAN BERGMAN
Keyword(s):  
Granulite Facies ◽  
Amphibolite Facies ◽  
Thermal Activity ◽  
The South ◽  
Magmatic Arc ◽  
Metasedimentary Rocks ◽  
The North ◽  
South Central ◽  
Augen Gneiss ◽  
A Minor

The Svecofennian Domain of the Fennoscandian Shield constitutes a considerable volume of Palaeoproterozoic crustal growth, 2.1–1.86 Ga ago, in between the Archaean craton in the NE and the 1.85–1.65 Ga Transscandinavian Igneous Belt (TIB) in the south and west. The Bergslagen area is a classical ore province located in the southwestern part of the Svecofennian Domain of south-central Sweden. Its northern part is dominated by volcanic and plutonic rocks of a magmatic arc with continental affinity, while the SE part is made up by a sedimentary basin. The Bergslagen area shows a metamorphic zonation from lower to middle amphibolite facies in the north to upper amphibolite facies and locally granulite facies in the south; a small greenschist area exists in the west. Identifying the age spectra of inherited components, magmatic crystallization, as well as metamorphic episodes, provide important constraints on the geodynamic evolution of this centrally located piece of the Shield.U–Pb zircon SIMS data presented in this paper complement the previous, regionally scattered TIMS data from this area. Magmatic zircons from two felsic metavolcanic rocks and two amphibolites (metagabbros) yield 1888±12, 1892±7 and 1887±5, 1895±5 Ma, respectively; i.e. within the 1.91–1.86 Ga range previously obtained for Early Svecofennian magmatism in Bergslagen. An augen gneiss from southern Bergslagen, assigned to the earliest TIB generation, yield an intrusive age of 1855±6 Ma. Metamorphic monazites from the same rock indicate that deformation and elevated thermal activity prevailed 1.83–1.82 Ga ago (TIMS). Metamorphic zircons in high-grade metasedimentary rocks from the south and west yield ages of 1793±5 and 1804±10 Ma, in accordance with ages for regional peak metamorphism and migmatite formation found elsewhere in the southern Svecofennian province of Sweden. More importantly, a few zircon crystals and overgrowths in rocks from the north indicate an early metamorphic episode at c. 1.87 Ga, indicating that Bergslagen has experienced two major metamorphic events. Detrital and inherited zircons span the range 2.78–1.90 Ga, with an apparent gap at 2.45–2.1 Ga, which further emphasize previous observations of a major juvenile (<2.1 Ga) and a minor Archaean provenance. This, and in particular the 1.94–1.91 Ga crystals present in the c. 1.89 Ga amphibolites, support the suggestion of a former Palaeoproterozoic pre-1.91 Ga crust in the Bergslagen area.

scholarly journals Research on the high-metamorphic complexes of the Agto area

1968 ◽  
Vol 15 ◽  
pp. 19-21
Author(s):  
E Bondesen
Keyword(s):  
Granulite Facies ◽  
Amphibolite Facies ◽  
The South ◽  
Field Mapping ◽  
Metamorphic History ◽  
The North ◽  
Field Season ◽  
Tectonic Development ◽  
New Research ◽  
Metamorphic Complexes

Mapping in the Agto area was continued in 1967, the second season of new research in this area; five teams were in the field mapping in nine individual areas. The main object of the mapping is to elucidate the relations between the Isortoq granulite facies complex in the south and the amphibolite facies gneisses of the Egedesminde complex in the north (Ramberg, 1949). AIready from the first field season (Bondesen, 1966, p. 20) it was clear that the problem essentially concerned areas with contrasted tectonic development and style besides metamorphic history and degree.

scholarly journals The Niflheim thrust: a tectonic contact between granulite and amphibolite facies gneisses, South-East Greenland

1989 ◽  
Vol 146 ◽  
pp. 66-69
Author(s):  
J.C Escher ◽  
R.P Hall
Keyword(s):  
Granulite Facies ◽  
Amphibolite Facies ◽  
Mobile Belt ◽  
Lower Grade ◽  
The South ◽  
North West ◽  
The North ◽  
High Crustal Level ◽  
Tectonic Contact ◽  
Main Component

The Niflheim thrust forms part of the northern boundary zone of the Proterozoic mobile belt of the Ammassalik region and defines the southernmost extent of granulite facies gneisses north-west of Sermilik. The thrust sharply separates grey amphibolite facies gneisses (footwall) from a thick and extensive unit of brown granulite facies gneisses, suggesting considerable lateral as well as vertical transport of the brown gneisses. Above the contact, the brown gneisses have only been weakly affected by deformation, whilst below the contact intensely folded and sheared grey gneisses indicate strong deformation of the upper part of the footwall sequence during thrusting. Asymmetry of folds below the contact and the E–W trending, gently north dipping thrust contact indicate a sinistral transpressional sense of movement with an up-to-the-south main component of transport. Three undeformed, discordant basic Proterozoic dykes in the grey gneisses of the footwall are truncated by the thrust and the thrust plane has been gently folded during a late stage of the regional Proterozoic deformation. Contrasts between high-grade mineralogy of Proterozoic dykes in the northern part of the Ammassalik region and lower grade, high crustal-level dykes of the grey gneiss terrain in the south are related to the regional thrusting from the north.

Climatology and Trends of Climate Extremes of Temperature and Precipitation in Belo Monte Hydropower Plant – Eastern Amazon, Brazil

2021 ◽  
Author(s):  
Wanderson Luiz-Silva ◽  
Pedro Regoto ◽  
Camila Ferreira de Vasconcellos ◽  
Felipe Bevilaqua Foldes Guimarães ◽  
Katia Cristina Garcia
Keyword(s):  
Climate Change ◽  
Climate Extremes ◽  
Annual Rainfall ◽  
The South ◽  
North Central ◽  
Adaptation Capacity ◽  
The North ◽  
South Central ◽  
Daily Data ◽  
Belo Monte

&lt;p&gt;This research aims to support studies related to the adaptation capacity of the Amazon region to climate change. The Belo Monte Hydroelectric Power Plant (HPP) is in the Xingu River basin, in eastern Amazonia. Deforestation coupled with changes in water bodies that occurred in the drainage area of Belo Monte HPP over the past few decades can significantly influence the hydroclimatic features and, consequently, ecosystems and energy generation in the region. In this context, we analyze the climatology and trends of climate extremes in this area. The climate information comes from daily data in grid points of 0.25&amp;#176; x 0.25&amp;#176; for the period 1980-2013, available in http://careyking.com/data-downloads/. A set of 17 climate extremes indices based on daily data of maximum temperature (TX), minimum temperature (TN), and precipitation (PRCP) was calculated through the RClimDex software, recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI). The Mann-Kendall and the Sen&amp;#8217;s Curvature tests are used to assess the statistical significance and the magnitude of the trends, respectively. The drainage area of the Belo Monte HPP is dominated by two climatic types: an equatorial climate in the north-central portion of the basin, with high temperatures and little variation throughout the year (22&amp;#176;C to 32&amp;#176;C), in addition to more frequent precipitation; and a tropical climate in the south-central sector, which experiences slightly more pronounced temperature variations throughout the year (20&amp;#176;C to 33&amp;#176;C) and presents a more defined wet and dry periods. The south-central portion of the basin exhibits the highest temperature extremes, with the highest TX and the lowest TN of the year occurring in this area, both due to the predominant days of clear skies in the austral winter, as to the advance of intense masses of polar air at this period. The diurnal temperature range is lower in the north-central sector when compared to that in the south-central region since the first has greater cloud cover and a higher frequency of precipitation. The largest annual rainfall volumes are concentrated at the north and west sides (more than 1,800 mm) and the precipitation extremes are heterogeneous across the basin. The maximum number of consecutive dry days increases from the north (10 to 20 days) to the south (90 to 100 days). The annual frequency of warm days and nights is increasing significantly in a large part of the basin with a magnitude ranging predominantly from +7 to +19 days/decade. The annual rainfall shows a predominant elevation sign of up to +200 mm/decade only in the northern part of the basin, while the remainder shows a reduction of up to -100 mm/decade. The duration of drought periods increases in the south-central sector of the basin, reaching up to +13 days/decade in some areas. The results of this study will be used in the future as an important input, together with exposure, sensibility, and local adaptation capacity, to design adaptation strategies that are more consistent with local reality and to the needs of local communities.&lt;/p&gt;

Surface faulting along the Superstition Hills fault zone and nearby faults associated with the earthquakes of 24 November 1987

1989 ◽  
Vol 79 (2) ◽  
pp. 252-281
Author(s):  
R. V. Sharp ◽  
K. E. Budding ◽  
J. Boatwright ◽  
M. J. Ader ◽  
M. G. Bonilla ◽  
...  
Keyword(s):  
Fault Zone ◽  
Lateral Displacement ◽  
Vertical Displacement ◽  
Repeated Measurements ◽  
The South ◽  
Surface Rupture ◽  
Imperial Valley ◽  
The North ◽  
South Central ◽  
The Right

Abstract The M 6.2 Elmore Desert Ranch earthquake of 24 November 1987 was associated spatially and probably temporally with left-lateral surface rupture on many northeast-trending faults in and near the Superstition Hills in western Imperial Valley. Three curving discontinuous principal zones of rupture among these breaks extended northeastward from near the Superstition Hills fault zone as far as 9 km; the maximum observed surface slip, 12.5 cm, was on the northern of the three, the Elmore Ranch fault, at a point near the epicenter. Twelve hours after the Elmore Ranch earthquake, the M 6.6 Superstition Hills earthquake occurred near the northwest end of the right-lateral Superstition Hills fault zone. Surface rupture associated with the second event occurred along three strands of the zone, here named North and South strands of the Superstition Hills fault and the Wienert fault, for 27 km southeastward from the epicenter. In contrast to the left-lateral faulting, which remained unchanged throughout the period of investigation, the right-lateral movement on the Superstition hills fault zone continued to increase with time, a behavior that was similar to other recent historical surface ruptures on northwest-trending faults in the Imperial Valley region. We measured displacements over 339 days at as many as 296 sites along the Superstition Hills fault zone, and repeated measurements at 49 sites provided sufficient data to fit with a simple power law. Data for each of the 49 sites were used to compute longitudinal displacement profiles for 1 day and to estimate the final displacement that measured slips will approach asymptotically several years after the earthquakes. The maximum right-lateral slip at 1 day was about 50 cm near the south-central part of the North strand of Superstition Hills fault, and the predicted maximum final displacement is probably about 112 cm at Imler Road near the center of the South strand of the Superstition Hills fault. The overall distributions of right-lateral displacement at 1 day and the estimated final slip are nearly symmetrical about the midpoint of the surface rupture. The average estimated final right-lateral slip for the Superstition Hills fault zone is about 54 cm. The average left-lateral slip for the conjugate faults trending northeastward is about 23 cm. The southernmost ruptured member of the Superstition Hills fault zone, newly named the Wienert fault, extends the known length of the zone by about 4 km. The southern half of this fault, south of New River, expressed only vertical displacement on a sinuous trace. The maximum vertical slip by the end of the observation period there was about 25 cm, but its growth had not ceased. Photolineaments southeast of the end of new surface rupture suggest continuation of the Superstition Hills fault zone in farmland toward Mexico.

scholarly journals Convergence of the Pamir and the South Tian Shan in the late Cenozoic: Insights from provenance analysis in the Wuheshalu section at the convergence area

Lithosphere ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 507-523 ◽  
Author(s):  
Xinwei Chen ◽  
Hanlin Chen ◽  
Edward R. Sobel ◽  
Xiubin Lin ◽  
Xiaogan Cheng ◽  
...  
Keyword(s):  
Source Area ◽  
Limited Area ◽  
Late Cenozoic ◽  
Provenance Analysis ◽  
The South ◽  
Active Deformation ◽  
The North ◽  
Large Populations ◽  
A Minor ◽  
Tian Shan

Abstract In response to collision and convergence between India and Asia during the Cenozoic, convergence took place between the Pamir and South Tian Shan. Here we present new detrital zircon U-Pb ages coupled with conglomerate clast counting and sedimentary data from the late Cenozoic Wuheshalu section in the convergence zone, to shed light on the convergence process of the Pamir and South Tian Shan. Large Triassic zircon U-Pb age populations in all seven samples suggest that Triassic igneous rocks from the North Pamir were the major source area for the late Cenozoic Wuheshalu section. In the Miocene, large populations of the North Pamir component supports rapid exhumation in the North Pamir and suggest that topography already existed there since the early Miocene. Exhumation of the South Tian Shan was relatively less important in the Miocene and its detritus could only reach a limited area in the foreland area. Gradually increasing sediment loading and convergence of the Pamir and South Tian Shan caused rapid subsidence in the convergence area. Since ca. 6–5.3 Ma, the combination of a major North Pamir component and a minor South Tian Shan component at the Wuheshalu section is consistent with active deformation of the South Tian Shan and the North Pamir. During deposition of the upper Atushi Formation, a larger proportion of North Pamir–derived sediments was deposited in the Wuheshalu section, maybe because faulting and northward propagation of the North Pamir caused northward displacement of the depocenter to north of the Wuheshalu section.

scholarly journals Performance of Landscape Roses Grown with Minimal Input in the North-central, Central, and South-central United States

2017 ◽  
Vol 27 (5) ◽  
pp. 718-730 ◽  
Author(s):  
David C. Zlesak ◽  
Randy Nelson ◽  
Derald Harp ◽  
Barbara Villarreal ◽  
Nick Howell ◽  
...  
Keyword(s):  
United States ◽  
National Level ◽  
The United States ◽  
The South ◽  
Flower Number ◽  
North Central ◽  
The North ◽  
South Central ◽  
Central United States ◽  
Plant Hardiness

Landscape roses (Rosa sp.) are popular flowering shrubs. Consumers are less willing or able to maintain landscape beds than in years past and require plants that are not only attractive, but well-adapted to regional climatic conditions, soil types, and disease and pest pressures. Marketing and distribution of rose cultivars occurs on a national level; therefore, it is difficult for U.S. consumers in the U.S. Department of Agriculture (USDA) Plant Hardiness Zones 3 to 5 to identify well-adapted, cold-hardy cultivars. Identifying suitable cultivars that have strong genetic resistance to pests and disease and that will tolerate temperature extremes without winter protection in the USDA Plant Hardiness Zones 3 to 5 is of tremendous value to consumers and retailers in northern states. Twenty landscape rose cultivars, primarily developed in north-central North America, were evaluated at five locations in the United States (three in the north-central United States, one in the central United States, and one in the south-central United States) using the low-input, multiyear Earth-Kind® methodology. Six roses had ≥75% plant survival at the end of the study and were in the top 50% of performers for overall mean horticultural rating at each of the three north-central U.S. sites: ‘Lena’, ‘Frontenac’, ‘Ole’, ‘Polar Joy’, ‘Sunrise Sunset’, and ‘Sven’. Five of these six roses met the same criteria at the central United States (exception ‘Lena’) and the south-central United States (exception ‘Polar Joy’) sites. Cultivar, rating time, and their interaction were highly significant, and block effects were not significant for horticultural rating for all single-site analyses of variance. Significant positive correlations were found between sites for flower number, flower diameter, and overall horticultural rating. Significant negative correlations were found between flower number and diameter within each site and also between black spot (Diplocarpon rosae) lesion size from a previous study and overall horticultural rating for three of the five sites. Cane survival ratings were not significantly correlated with overall horticultural rating, suggesting some cultivars can experience severe winter cane dieback, yet recover and perform well. Data from this study benefit multiple stakeholders, including nurseries, landscapers, and consumers, with evidence-based regional cultivar recommendations and breeders desiring to identify regionally adapted parents.

The Quérigut Complex (Pyrenees, France) revisited by the AMS technique : a syntectonic pluton of the Variscan dextral transpression

2004 ◽  
Vol 175 (2) ◽  
pp. 157-174 ◽  
Author(s):  
Jean-Baptiste Auréjac ◽  
Gérard Gleizes ◽  
Hervé Diot ◽  
Jean-Luc Bouchez
Keyword(s):  
Magnetic Susceptibility ◽  
Progressive Increase ◽  
The South ◽  
Magnetic Susceptibility Anisotropy ◽  
Metasedimentary Rocks ◽  
The North ◽  
Deformation Regime ◽  
Shear Sense ◽  
Dextral Shear ◽  
Magnetic Lineations

Abstract The Variscan Querigut Pluton (eastern Axial Zone, Pyrenees), recently dated at 307 ± 2 Ma, is a classical example for the structural study of granitoids. We present a new structural analysis of this pluton using the powerful technique of magnetic susceptibility anisotropy (AMS). A model of pluton emplacement is proposed on the basis of complementary microstructural analyses allowing the determination of the temperatures of fabric acquisition in the magmatic units, and of the shear sense criteria in the surrounding country rocks. This pluton is constituted by two main units that have intruded metasedimentary rocks where regional metamorphic conditions decrease from southwest to northeast. A well-foliated southern granodioritic unit, rich in Devonian marble xenoliths, is bounded to the south by Cambro-Ordovician metapelites. A weakly foliated northern monzogranitic unit, bounded to the north by Devonian marbles, comprises two sub-types : an outer biotite-monzogranite and an inner biotite-muscovite leucomonzogranite. Abundant basic stocks of variable sizes and lithologies outcrop in the granodioritic unit and in the southern part of the monzogranitic unit. Mean magnetic susceptibility and magnetic foliation maps show a very good agreement with the previous compiled petrographic and structural maps, strengthening the validity of the AMS technique. The northern monzogranitic units display two unevenly distributed structural patterns : (a) a NE-SW-trending pattern of weakly to steeply dipping foliations, dominant in the outer biotite monzogranite, is associated to subhorizontal NE-SW lineations ; and (b) a NW-SE-trending pattern of steeply dipping foliations, dominant in the inner biotite-muscovite monzogranite, is concentrated in NW-SE elongated corridors, associated to subhorizontal NW-SE lineations. In the southern granodioritic unit, foliation patterns follow roughly both the main regional foliation pattern and the pluton boundary, with foliation dips increasing to the south. Subhorizontal NW-SE trending magnetic lineations in the inner parts of this unit, are progressively verticalized toward the southern pluton boundary. A progressive increase in total magnetic anisotropy is observed toward the border of the pluton, correlated with both an increase in solid-state deformation and a decrease of the final temperature of fabric acquisition. These features result from a pluri-kilometric shear zone localized in the western half of the granodioritic unit, decreasing in thickness in its eastern half and along N060oE trending contacts with the country rocks. In the northern monzogranitic unit, one can roughly correlate the magmatic microstructures to the NE-SW trending fabric, and the superimposed subsolidus microstructures to the NW-SE-trending corridors, where rather low-temperature (&lt; 300 oC) fluid-assisted cataclastic microstructures may also appear. The country-rocks, half kilometer away from the pluton border, display the D2 regional Variscan pattern, with subvertical and N110oE-striking foliations and subhorizontal and E-W-trending stretching lineations associated to a dextral shear. Closer to the pluton, the country-rocks are subjected to the pluton influence, particularly along the southern border where a strong flattening is associated to subvertical lineations related to local thrusting of the pluton onto its country rocks. An emplacement model is proposed through the injection of three principal magma batches (granodiorite, biotite-monzogranite and biotite-muscovite monzogranite) that successively and progressively built up the pluton while the whole region was subjected to a dextral and compressive deformation regime, in agreement with AMS results obtained from several other plutons of the Pyrenees.

A new North American chorus frog species (Amphibia: Hylidae: Pseudacris) from the south-central United States

Zootaxa ◽  
2008 ◽  
Vol 1675 (1) ◽  
pp. 1 ◽  
Author(s):  
EMILY MORIARTY LEMMON ◽  
ALAN R. LEMMON ◽  
JOSEPH T. COLLINS ◽  
DAVID C. CANNATELLA
Keyword(s):  
United States ◽  
New Species ◽  
North American ◽  
Advertisement Call ◽  
The South ◽  
The North ◽  
South Central ◽  
Central United States ◽  
Chorus Frog ◽  
Genetic Characters

We describe a new species of chorus frog of the North American treefrog genus Pseudacris from the south-central United States. This new species is morphologically similar to the parapatric species P. feriarum and has thus previously been considered synonymous with this species. The new species is geographically distinct from P. feriarum and from its sister species, P. nigrita. We diagnose the new species based on advertisement call, morphological, and genetic characters.

scholarly journals Structural studies in the pre-Cambrian of western Greenland. Part III. Southern Sukkertoppen District

1962 ◽  
Vol 31 ◽  
pp. 1-46
Author(s):  
A Berthelsen
Keyword(s):  
Structural Evolution ◽  
Granulite Facies ◽  
Field Work ◽  
Amphibolite Facies ◽  
Alternative Theory ◽  
Low Grade ◽  
The North ◽  
Kinematic Evolution ◽  
Facies Metamorphism ◽  
Wrench Fault

This paper summarises several summers field work within the southern Sukkertoppen district. Since detailed mapping has only been carried out within smaller areas within the region, the remainder being covered by reconnaissance mapping along the coasts, the results should be considered as preliminary. The southern Sukkertoppen district can be divided into three tectonic units, the Nordland, the Finnefjeld, and the Alángua complexes, which, most probably, were formed during the Ketilidian cycle (E. Wegmann, 1938). The metamorphic complexes are traversed by postorogenic dykes and faults (Berthelsen and Bridgwater, 1960). The dykes and faults were seemingly formed before the Nagssugtôqidian revolution which affected the country further to the north (Ramberg, 1948). The northern Nordland complex is shown to have passed through a metamorphic and structural evolution very similar to that which recently has been described from a small area within the complex (see table 2). An original granulite facies rock assemblage has been exposed to two successive imprints of retrograde metamorphism: first an amphibolite facies metamorphism; next a postorogenic epidote-amphibolite to greenschist facies metamorphism in connection with the formation of the younger faults. Evidence is brought forward that the tectonic phases established from Tovqussap nunâ may also be traced within the remaining parts of the Nordland complex. In one case (see fig. 3) an analysis of the basement structures reveals that the post-orogenic faulting is of the wrench fault type. The Finnefjeld complex which is built up of homogeneous hornblende-biotite-bearing quartz-dioritic gneisses is believed to have been originally composed of granulite facies rocks. Subsequent strong penetrative movements accompanied by low grade amphibolite facies metamorphism were responsible for the formation of the present Finnefjeld gneisses. This idea is strongly supported by the facts that relic patches of hypersthene gneiss and transgressive, but deformed, more or less uralitised diorite bodies occur within the Finnefjeld gneiss. The Alangua complex comprises abundant pelitic and semipelitic schists, amphibolites, ultrabasics and skarn rocks in addition to gneisses which are considered to be of metasomatic origin. The ultrabasic rocks have been described by H. Sørensen (1952,1953, 1954, and 1955). The rocks of this complex can also be shown to have passed through two periods of metamorphism (see also H. Sørensen, 1952); an original medium to high grade amphibolite facies metamorphism was succeeded by a later low grade amphibolite facies metamorphism accompanied by granitisation, pegmatisation etc., indicating the presence of a volatile-rich dispersed phase. Although not studied in detail, the structures of the Alángua complex are sufficiently well-known to establish the kinematic evolution of this complex. The first amphibolite facies metamorphism seems to correspond to the Smalledal-Pâkitsoq phases of the Nordland complex, while the subsequent period of low grade amphibolite metamorphism can be matched with the posthumous phase. During this latter, the northern part of the Nordland complex, which locally was thrust over the Alángua rocks (thereby causing their refolding) was converted into the present Finnefjeld gneisses. This interpretation explains the present differences between the three com· plexes as being due to Stockwerk tectonics, fig. 16. An alternative theory which holds that the Alángua rocks are younger than those of the southern complexes does not seem to concur with the field relation known so far. No mineral deposits of economic interest were found during the survey, but traces of sulfides (see tables 1 and 3), magnetite, molybdenite, corundum, monazite, zircon, talc and soapstone have been met with at various localities.

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