Strain partitioning in a collapsing hot orogeny

2020 ◽  
Author(s):  
Filipe Temporim ◽  
Ricardo Trindade ◽  
Eric Tohver ◽  
Marcos Egydio-Silva ◽  
Tiago Valim
Keyword(s):  
General Structure ◽  
Magnetic Fabric ◽  
Magma Ascent ◽  
Crustal Material ◽  
Strain Partitioning ◽  
The South ◽  
Slow Cooling ◽  
The North ◽  
Long Time ◽  
Host Rocks

<p>Large, hot orogens are characterized by an orogenic plateau supported by a zone of weak ductile flow. During the collision phase, the magnitude of the belt and the temperature increase as radioactive crustal material is accreted, buried and heated. After convergence ends, no material is added to the orogenic system and the orogen undergo gravitational (or extensional) collapse that results from the lateral flow of the hot orogenic infrastructure. In the Araçuaí-West Congo orogen (AWO), the high temperatures, slow cooling, and excessive amount of melt in the hinterland, in the northern part of the belt, imply that a high temperature was maintained for a long time. Geochronologic results suggest that this internal domain was hot for a long time, cooling at < 3°/Myr since 600 Ma until 500 Ma, and cooling through the Ar/Ar retention temperature for biotite occurred around 470 Ma. In the south the collapse of the orogen is marked by the widespread intrusion of bimodal, composite plutons at ~500 Ma. Here we use the magnetic fabric (i.e. low-field anisotropy of magnetic susceptibility) of intrusions in the north and south sectors to track the kinematics and rheological changes across the belt. In the northern part of the AWO we studied the Padre Paraíso Charnockite and the southern part of the AWO we studied the Conceição de Muqui and Santa Angélica plutons. The Padre Paraíso charnockite has a coherent magnetic fabric, with magnetic foliations trending N-S, following the general structure of the belt in that sector. In turn, Conceição de Muqui and Santa Angélica plutons show a concentric distribution of foliations and lineations, in starking contrast with the general NE-SW trend of the belt in the south. This contrasting structural pattern for coeaval plutons along the AWO belt reveal the strain partitioning at the scale of the orogenic belt during the cooling of the AWO. At 500 Ma the hot northern sector remains warm enough to allow a coherent deformation of intrusions and host rocks. At the same time, more material was being added to the margins of the hot orogen, which already cold, with the diapire-like plutons structure being dominantly controlled by the forces of magma ascent and emplacement.</p>

Mineralization of the South Pennine Orefield, UK—A Review

2016 ◽  
Vol 61 (1) ◽  
pp. 55-86 ◽  
Author(s):  
T.D. Ford ◽  
N.E. Worley
Keyword(s):  
Wall Rock ◽  
Hydraulic Gradient ◽  
Mississippi Valley ◽  
The South ◽  
The North ◽  
East Midlands ◽  
Ore Minerals ◽  
Placer Deposits ◽  
Fractured Limestone ◽  
Host Rocks

This review of the South Pennine Orefield (SPO) draws together the findings from many years of underground field observations and petrographical study. Mineralization is of the Mississippi Valley-type (MVT) and is concentrated within an area of some 200 km2, mainly along the eastern margins of a large inlier, the Derbyshire High, in Carboniferous platform carbonate host rocks. The inlier covers some 390 km2, forms an up-dip promontory of a larger structure, the East Midlands Shelf, and is surrounded by shales and sandstones of the Millstone Grit and Pennine Coal Measures groups. Mineralization probably began during the late Westphalian (Moscovian, Mid Pennsylvanian), when subsidence due to thermal sag resulted in the limestone being buried to depths of c. 4 km beneath younger strata. A palaeohydraulic reconstruction is presented from analysis of mineralized palaeokarst features, which are interpreted as representing hypogenic or deep-seated karst formed by the interstratal circulation of hydrothermal water in a mostly confined hydrodynamic setting. It is reasoned that Variscan inversion of N–S faults to the east of the SPO resulted in erosion of Namurian and Westphalian (Upper Mississippian–Middle Pennsylvanian) rocks and created a hydraulic gradient inclined towards the south-west. Acidic F-Ba-Pb-Zn enriched fluid evolved in the Namurian basinal rocks and migrated into fractured limestone. The resultant wall-rock dissolution along existing wrench faults led to the formation of a maze of stratiform mineral deposits (flats) and more irregular spongework-shaped structures (pipes). The presence of hydrocarbon accumulations in the limestones and evidence from fluid inclusions indicates that the mineralizing fluids were chloride/fluoride-rich and compositionally typical of oilfield brine. Isotope evidence demonstrates a sulphate evaporite source of sulphur, mainly from the Chadian (Visean, Middle Mississippian) Middleton Anhydrite Formation. By the late Cenozoic, karstification of exposed carbonate rocks began and the current pattern of epigenic karst drainage started to develop as the regional hydraulic gradient reversed, assuming its present eastward inclined attitude. The mineralized hypogenic karst was overprinted by later drainage systems as the hydraulic gradient changed, and placer deposits were formed from the erosion of existing mineralization. This was accompanied by circulation of meteoric water and resulted in the supergene weathering of the sulphide ore minerals. Eastward underflow of meteoric groundwater also exploited the same mineralization flow paths. There is evidence that pre-mineralization hypogenic karst was also significant in the formation of orebodies in the North Pennine Orefield and the Halkyn–Minera Orefield of NE Wales.

scholarly journals Geopolitical consequences of the transfer of the Metropolitan Department from Kiev to Vladimir over Klyazma (13th c.)

2005 ◽  
pp. 95-104
Author(s):  
Ruslana M. Sheretyuk
Keyword(s):  
Political Power ◽  
The South ◽  
Permanent Residence ◽  
The North ◽  
Long Time ◽  
Difficult Position

The relocation of two Metropolitan Metropolitan Kirill II (1250-1281) and Maxim (1285-1305) to the North, to Vladimir above Klyazma, put the Galicia-Volyn state and the Ukrainian Church in a difficult position. While Kiev remained the actual Metropolitan Chair, the latter could stay in the northern Russian cities for a long time, without causing much anxiety or dissatisfaction in the South. However, with the relocation of Metropolitan Maxim to permanent residence in the capital of the North-Russian Grand Duke (1299), the rulers of the southwestern region of Russia realized that in this way they were losing significant spiritual and political power, which henceforth gave the North the advantage of the All-Russian genius.

Strain partitioning around an indenter during oroclinal bending: kinematics of the Circum-Moesian fault system of the Carpatho-Balkanides

2021 ◽  
Author(s):  
Nemanja Krstekanic ◽  
Liviu Matenco ◽  
Uros Stojadinovic ◽  
Ernst Willingshofer ◽  
Marinko Toljić ◽  
...  
Keyword(s):  
Large Scale ◽  
Strike Slip ◽  
Fault System ◽  
Normal Faults ◽  
Strain Partitioning ◽  
The South ◽  
The Carpathians ◽  
The North ◽  
Moesian Platform ◽  
Parallel Extension

<p>The Carpatho-Balkanides of south-eastern Europe is a double 180° curved orogenic system. It is comprised of a foreland-convex orocline, situated in the north and east and a backarc-convex orocline situated in the south and west. The southern orocline of the Carpatho-Balkanides orogen formed during the Cretaceous closure of the Alpine Tethys Ocean and collision of the Dacia mega-unit with the Moesian Platform. Following the main orogen-building processes, the Carpathians subduction and Miocene slab retreat in the West and East Carpathians have driven the formation of the backarc-convex oroclinal bending in the south and west. The orocline formed during clockwise rotation of the Dacia mega-unit and coeval docking against the Moesian indenter. This oroclinal bending was associated with a Paleocene-Eocene orogen-parallel extension that exhumed the Danubian nappes of the South Carpathians and with a large late Oligocene – middle Miocene Circum-Moesian fault system that affected the orogenic system surrounding the Moesian Platform along its southern, western and northern margins. This fault system is composed of various segments that have different and contrasting types of kinematics, which often formed coevally, indicating a large degree of strain partitioning during oroclinal bending. It includes the curved Cerna and Timok faults that cumulate up to 100 km of dextral offset, the lower offset Sokobanja-Zvonce and Rtanj-Pirot dextral strike-slip faults, associated with orogen parallel extension that controls numerous intra-montane basins and thrusting of the western Balkans units over the Moesian Platform. We have performed a field structural study in order to understand the mechanisms of deformation transfer and strain partitioning around the Moesian indenter during oroclinal bending by focusing on kinematics and geometry of large-scale faults within the Circum-Moesian fault system.</p><p>Our structural analysis shows that the major strike-slip faults are composed of multi-strand geometries associated with significant strain partitioning within tens to hundreds of metres wide deformation zones. Kinematics of the Circum-Moesian fault system changes from transtensional in the north, where the formation of numerous basins is controlled by the Cerna or Timok faults, to strike-slip and transpression in the south, where transcurrent offsets are gradually transferred to thrusting in the Balkanides. The characteristic feature of the whole system is splaying of major faults to facilitate movements around the Moesian indenter. Splaying towards the east connects the Circum-Moesian fault system with deformation observed in the Getic Depression in front of the South Carpathians, while in the south-west the Sokobanja-Zvonce and Rtanj-Pirot faults splay off the Timok Fault. These two faults are connected by coeval E-W oriented normal faults that control several intra-montane basins and accommodate orogen-parallel extension. We infer that all these deformations are driven by the roll-back of the Carpathians slab that exerts a northward pull on the upper Dacia plate in the Serbian Carpathians. However, the variability in deformation styles is controlled by geometry of the Moesian indenter and the distance to Moesia, as the rotation and northward displacements increase gradually to the north and west.</p>

The Inner Tradition of Fuchai

2021 ◽  
pp. 105-146
Author(s):  
Jianjun He
Keyword(s):  
The State ◽  
The South ◽  
The North ◽  
Sima Qian ◽  
Long Time

This chapter talks about Fuchai, who was the last king of Wu. According to Sima Qian, Fuchai was a complicated and tragic figure who avenged his father's death, defeated Wu's long time rival Yue, extended Wu's influence to the north, and led Wu to become a political hegemon among the states. It focuses on the fall of the king of Wu by highlighting Fuchai's obstinance, his trust of dishonest words, his executions of loyal ministers, and the eventual decline of his state. It also omits the early successful years of King Fuchai and begins with the eleventh year of his rule, the year he ignored the most dangerous enemy Yue in the south and extended his power north by attacking the state of Qi. The chapter concludes with Fuchai's reluctant suicide that was preceded by expressions of remorse for killing Wu Zixu and Gongsun Sheng.

Crustal material recycling induced by subduction erosion and subduction-channel exhumation: A case study of central Tibet (western China) based on P-T-t paths of the eclogite-bearing Baqing metamorphic complex

2020 ◽  
Author(s):  
Xin Jin ◽  
Yu-Xiu Zhang ◽  
Donna L. Whitney ◽  
Kai-Jun Zhang ◽  
Natalie H. Raia ◽  
...  
Keyword(s):  
Mantle Wedge ◽  
Crustal Material ◽  
Metamorphic Complex ◽  
The South ◽  
Subduction Channel ◽  
Crustal Recycling ◽  
The North ◽  
Subduction Erosion ◽  
Proterozoic Basement ◽  
Central Tibet

Subduction and exhumation processes, interacting with each other, play a key role in crustal recycling. Downgoing oceanic lithosphere constitutes the dominant input at subduction margins, but subduction erosion, the removal of crustal material from the overriding plate, may add additional ingredients and complexity to the subduction factory. Different exhumation models have been proposed to explain how subducted materials are exhumed and therefore contribute to crustal recycling, e.g., exhumation up the subduction channel versus diapiric rise through the mantle wedge that overlies the subducted plate. The recently discovered Baqing eclogite-bearing high-pressure metamorphic complex, central Tibet, China, provides an excellent opportunity to decode the exhumation process, the origin of subduction-related magmatism, and the crustal structure of the North Qiangtang block, in addition to elucidating processes of crustal recycling. Pressure-temperature-time (P-T-t) paths and zircon U-Pb ages and trace-element compositions for Baqing high-pressure rocks were used to evaluate exhumation processes and to determine the geochemical and tectonic affinity of the Baqing metamorphic complex. The Baqing metamorphic complex is mainly composed of eclogite, gneiss, and schist. It is located between two geologically distinct terranes—the South Qiangtang block, which has early Paleozoic basement, and the North Qiangtang block, which has Proterozoic basement. In the schist, zircon cores with steep heavy rare earth element (HREE) slopes and oscillatory zoning yielded inherited ages that are similar to detrital zircon ages for the South Qiangtang block schist; in contrast, zircon rims with flat HREE slopes yielded metamorphic ages of 224 Ma that are similar to the metamorphic ages obtained for the Baqing eclogite. In contrast, zircons from the gneiss yielded an upper-intercept age of 1033 ± 32 Ma (interpreted as the crystallization age) and a lower-intercept metamorphic age of 198 ± 4 Ma. Field relations indicate that gneiss and eclogite/amphibolite were exhumed together, so the ∼20 m.y. gap between the gneiss and the metabasite metamorphism may indicate a long exhumation duration. In the region, Proterozoic ages of ca. 1000 Ma are known only from the North Qiangtang block; we thus propose that the Baqing gneiss originated from North Qiangtang block Proterozoic basement, which, along with North Qiangtang block Triassic arc magmatic rocks and the discrepancies between ancient and current arc-trench distances, results in estimates of ∼20−170 km of Triassic subduction erosion. Results of P-T analyses show that most eclogite, amphibolite, and schist shared a similar clockwise P-T path, different from that of the gneiss, which records a higher geothermal gradient. The clockwise P-T trajectory, long exhumation duration, lack of significant heating during exhumation, and the South Qiangtang block affinity of the schist (host rock of the Baqing eclogite) are consistent with subduction-channel exhumation rather than diapiric rise through the mantle wedge. Geochemical similarities between the North Qiangtang block Triassic subduction-related rocks and the Baqing gneiss may signal the involvement of unexhumed Baqing metamorphic complex in the recycling of the Qiangtang crust.

scholarly journals SALITRE: O PRODUTO QUÍMICO ESTRATÉGICO NO PASSADO DO BRASIL

Química Nova ◽  
2020 ◽  
Author(s):  
Luciano Faria ◽  
Carlos Filgueiras
Keyword(s):  
Minas Gerais ◽  
Historical Documents ◽  
Mining Activities ◽  
The South ◽  
Chemical Product ◽  
The Past ◽  
The North ◽  
Long Time

SALTPETER: THE STRATEGIC CHEMICAL PRODUCT IN THE PAST OF BRAZIL. Saltpeter demanded for a long-time strategic attention in view of its importance in the form of gunpowder by the governments of many nations. The sources of this mineral in Brazil were almost always associated to the soil in caves, which was extracted because of a limited amount of that precious salt. The first references pointed out that saltpeter was first discovered in the São Francisco basin in regions of the south of the Captaincy of Bahia and in the north of Minas Gerais. Some historical documents show that the Serra do Baldim was the object of intensive mining activities of saltpeter from its caves and the product became the focus of conflicts and left scars on the walls of some limestone caverns.

A Cemetery of the Ronaldsway Culture at Ballateare, Jurby, Isle of Man

1947 ◽  
Vol 13 ◽  
pp. 161-169 ◽  
Author(s):  
G. Bersu
Keyword(s):  
Sea Level ◽  
Clayey Soil ◽  
Sandy Soils ◽  
Agricultural Activities ◽  
The South ◽  
The West ◽  
Isle Of Man ◽  
The North ◽  
Long Time ◽  
Slight Rise

The excavation of a Viking mound in the north of the Isle of Man during October and November, 1946, led to the discovery of older remains beneath and around the mound. The site was in the yard of the disused farmstead of Ballateare (formerly called Killane) in the parish of Jurby.It lies on a slight rise some 50 feet above sea level half a mile distant from the sea, which is now eroding this region of the west coast at an estimated rate of one yard per year. To the south the ground slopes down to the Killane river which runs a quarter of a mile away in a broad marshy valley. To the north and east the ground is flat, and from the site there is a wide view over the sea, the distant mountains to the south, and the plain to the north. In this district the light sandy soils alternating with more clayey soil are good for agriculture. The sub-soil in the farmyard is a fine yellow diluvial sand with some bands of coarser gravel. The ground around the mound had been much disturbed by agricultural activities, and for a long time the yard had been used for storing potatoes in clamps: only superstition had preserved the mound undisturbed.

scholarly journals BILYI KAMIN: SITE STRUCTURE OF THE BIGGEST TRYPILLIA CULTURE SETTLEMENT OF THE SOUTHERN BUH-DNISTER INTERFLUVE

2019 ◽  
Vol 33 (4) ◽  
pp. 362-372
Author(s):  
V. S. Rud ◽  
R. Hofmann ◽  
V. A. Kosakivskyi ◽  
O. V. Zaitseva ◽  
J. Muller
Keyword(s):  
Research Effort ◽  
The South ◽  
Regional Variability ◽  
Total Size ◽  
North West ◽  
The North ◽  
Staggered Arrangement ◽  
Long Time ◽  
Survey System ◽  
North Part

So far research effort regarding Cucuteni—Trypillia mega-sites was to a large extent focussed on the region in the east of the Southern Buh. In contrast, the Southern Buh-Dnister interfluve stands for long time in the shadow of its eastern neighbour. To improve this situation and to gain a better understanding of the macro-regional variability within the Cucuteni—Trypillia cultural complex, in spring 2018 the exploration of the large CTCC site Bilyi Kamin was started by an international team of researchers from Kiel University (Germany) and Institute of Archaeology of the National Academy of Science of Ukraine (Kyiv, Ukraine) which is the largest settlement in this region. Magnetometry in total size of 40.6 ha have been performed using the MAGNETO® MX V3 Survey System of the company SENSYS Sensorik & Systemtechnologie GmbH Bad Saarow (Germany). During our survey large areas in the south, north and near the centre of the site were measured. Based on these data the total extension of the site can be estimated to approximately 97 ha. Different categories of magnetic anomalies can be identified in Bilyi Kamin: 297 rectangular anomalies, which are the ruins of intensively burnt clay houses; 141 rectangular anomalies of houses, burnt with less intensity or eroded; four rectangular anomalies of unique buildings, so-called «megastructures»; 351 anomaly of different-shape objects, most of which can be interpreted as pits; 12 stretched objects, presumably road to the south of the site; linear anomaly of the ditch or natural gully to the north-west from north part of outer circle. The site is built in two circles of houses. The ring corridor between the circles is free from buildings. Some buildings are located outside the circles as well. They are grouped as short lines radial and parallel in respect to the circles. The space inside the circles is built partially. In the north and north-west parts of the site the buildings are grouped mostly in long radial lines. In the south part of the site the number of buildings inside the circles is smaller. This might indicate a heterogeneous character of the population or changes in the development plan. The anomalies of pits from Bilyi Kamin are usually located near the buildings, at side or ending walls. Some groups of pits are not connected to the buildings. It is also possible that some of anomalies of pits, having largest nT values can represent other kind of objects — as for example pottery kilns. In Bilyi Kamin three elongated mega-structures with lengths between 36 and 64 m and widths between 8 and 11.5 m are placed on the 420 Ч (>150) m measuring square (so-called «plaza»). The partly staggered arrangement of these constructions might suggest that they were not built simultaneously but represent a sequence of successively used buildings. Within the concentric ring corridor directly beside of the central plaza, additionally a fourth mega-structure is visible. For the planning of the settlement layout, the placement of a rectangular square on top of the promontory with three large buildings played potentially an important role. These mega-structures and the associated plaza most likely formed the architectural arena of central integrative institutions for decision-making, integrative ritual action, and surplus-consumption at the level of the entire settlement.

Long-term Cyclic Variations of Prominences, Green and Red Coronae over Solar Cycles

2000 ◽  
Vol 179 ◽  
pp. 201-204
Author(s):  
Vojtech Rušin ◽  
Milan Minarovjech ◽  
Milan Rybanský
Keyword(s):  
Emission Lines ◽  
High Latitudes ◽  
Green Line ◽  
Solar Cycles ◽  
The South ◽  
Coronal Emission ◽  
Local Maxima ◽  
The North ◽  
Cyclic Variations

AbstractLong-term cyclic variations in the distribution of prominences and intensities of green (530.3 nm) and red (637.4 nm) coronal emission lines over solar cycles 18–23 are presented. Polar prominence branches will reach the poles at different epochs in cycle 23: the north branch at the beginning in 2002 and the south branch a year later (2003), respectively. The local maxima of intensities in the green line show both poleward- and equatorward-migrating branches. The poleward branches will reach the poles around cycle maxima like prominences, while the equatorward branches show a duration of 18 years and will end in cycle minima (2007). The red corona shows mostly equatorward branches. The possibility that these branches begin to develop at high latitudes in the preceding cycles cannot be excluded.

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