scholarly journals Identification of Zones and Areal Extent of Weathered Crystalline Basement in the Archean-Lower Proterozoic Crust of the South Tatar Arch

Georesursy ◽  
2017 ◽  
Vol 19 (3) ◽  
pp. 264-271
Author(s):  
N.B. Amelchenko ◽  
◽  
R.Kh. Masagutov ◽  
R.V. Akhmetzyanov ◽  
K.S. Kurbangaleeva ◽  
...  
Keyword(s):  
Crystalline Basement ◽  
Areal Extent ◽  
The South ◽  
Lower Proterozoic

The petrochemistry of the Lower Proterozoic metamorphic rocks from the Dabieshan-Lianyungang area, the southeastern margin of the North China Platform

1991 ◽  
Vol 55 (379) ◽  
pp. 263-276 ◽  
Author(s):  
Sang Longkang
Keyword(s):  
Continental Margin ◽  
North China ◽  
Active Continental Margin ◽  
The South ◽  
North China Platform ◽  
The North ◽  
Lower Proterozoic ◽  
Southeastern Margin ◽  
Tectonic Settings ◽  
North China Plate

AbstractBased on geological studies, 141 rock analyses and 5 trace element analyses of metabasites, the present paper deals with the rock association, chemical features, protolith formation and the original tectonic settings upwards through the Lower Proterozoic metamorphic strata in the Dabieshan-Lianyungang area, in the south-east of the North China Platform. The results of the study indicate that the lower and middle parts of the metamorphic strata comprise terrigenous clastics, phosphoritic and aluminous sedimentary formations which formed under stable continental margin conditions. In the middle-upper part a calc-alkaline volcano-sedimentary formation under the active continental margin was developed. The Lower Proterozoic meta-strata of sedimentary-volcanosedimentary origin from bottom upwards suggest that the tectonic evolution of the south-eastern margin of the North China Platform is a process from stabilization to mobilization. This process suggests a northward subduction of the Yangtze Plate under the North China Plate during the later part of the early Proterozoic.

‘Plains-Type Folds’ in the Midcontinent Region (U.S.A.): Chronicling A Concept

1999 ◽  
Vol 18 (2) ◽  
pp. 264-294 ◽  
Author(s):  
D. Merriam
Keyword(s):  
Twentieth Century ◽  
Crystalline Basement ◽  
Areal Extent ◽  
Structural Pattern ◽  
Sediment Compaction ◽  
The World ◽  
Basement Fault ◽  
Midcontinent Usa

‘Plains-type folds’ are those folds formed in gently dipping sediments overlying a crystalline basement in cratonic areas of the world. They are the result of differential compaction of sediments over rigid basement fault blocks. Trends of the folds in the sedimentary section thus coincide with trends of basement features. Plains-type folds generally are (1) small in areal extent, (2) increase in closure downward, (3) without a corresponding depression, and (4) asymmetric and associated with faulting. The features were developed intermittently through time by differential compaction of the sediments over an inherent structural pattern of uplifted fault blocks in the basement. Plains-type folds were recognized early in the twentieth century in the Midcontinent (USA) as containing petroleum. They were the object of much speculation on their origin and development and were studied intensively in the 1920s and 1930s. Most of the studies were concentrated in Kansas and Oklahoma and revolved around the relation of the structures as mapped in the sediments to the configuration of the Precambrian crystalline basement, relation of structure and temperature, and the effect of sediment compaction over ‘buried hills.’

scholarly journals Chemical data on some rock-forming minerals from high-grade gneisses, amphibolites and anorthosites from the Fiskenæsset area

1971 ◽  
Vol 35 ◽  
pp. 22-23
Author(s):  
T Frisch
Keyword(s):  
Rock Type ◽  
Amphibolite Facies ◽  
Chemical Data ◽  
High Grade ◽  
Boundary Zone ◽  
Areal Extent ◽  
Common Occurrence ◽  
The South ◽  
The West ◽  
The North

The area mapped by the writer is situated to the west of Fiskenæsset and lies in the boundary zone between granulite and amphibolite facies rocks (see Kalsbeek, this report). In the north a creamy- to pink-weathering gneiss, commonly containing hypersthene and biotite is the chief rock type. In the south small-folded, pale-grey weathering biotite-hornblende gneisses are predominant. Amphibolite is of common occurrence in layers, pods and agmatite. The areal extent of the anorthosite-pyribolite complex as previously outlined by reconnaissance mapping (Ghisler & Windley, 1967) was confirmed in general but modified in detail. Additional occurrences of rocks belonging to the complex were found.

scholarly journals Radar-observed spatial and temporal rainfall variability near the Tapajós-Amazon confluence

2014 ◽  
Vol 29 (spe) ◽  
pp. 23-30 ◽  
Author(s):  
Julia Clarinda Paiva Cohen ◽  
David Roy Fitzjarrald ◽  
Flávio Augusto Farias D'Oliveira ◽  
Ivan Saraiva ◽  
Illelson Rafael da Silva Barbosa ◽  
...  
Keyword(s):  
Rainfall Variability ◽  
Radar Reflectivity ◽  
Amazon River ◽  
Land Breeze ◽  
Areal Extent ◽  
Convective Conditions ◽  
The South ◽  
Satellite Rainfall ◽  
Rainfall Estimates

Standard Amazonian rainfall climatologies rely on stations preferentially located near river margins. River breeze circulations that tend to suppress afternoon rainfall near the river and enhance it inland are not typically considered when reporting results. Previous studies found surprising nocturnal rainfall maxima near the rivers in some locations. We examine spatial and temporal rainfall variability in the Santarém region of the Tapajós-Amazon confluence, seeking to describe the importance of breeze effects on afternoon precipitation and defining the areal extent of nocturnal rainfall maxima.We used three years of mean S band radar reflectivity from Santarém airport with a Z-R relationship appropriate for tropical convective conditions. These data were complemented by TRMM satellite rainfall estimates. Nocturnal rainfall was enhanced along the Amazon River, consistent with the hypothesis that these are associated with the passage of instability lines, perhaps enhanced by local channeling and by land breeze convergence. In the daytime, two rainfall bands appear in mean results, along the east bank of the Tapajós River and to the south of the Amazon River, respectively.

scholarly journals Chemical composition and age of monazite-(Ce) in granitoids of the crystalline basement from the South Yamal

2020 ◽  
pp. 28-34
Author(s):  
Vera Vitalievna KHILLER ◽  
Keyword(s):  
Chemical Composition ◽  
Weighted Average ◽  
Crystalline Basement ◽  
Beam Diameter ◽  
Work Study ◽  
The South ◽  
Electron Probe Microanalyzer ◽  
Chemical Dating ◽  
Electron Beam Diameter

The relevance of the work is due to the need to improve the method of chemical dating as applied to high-thorium accessory minerals, which are difficult to date by isotope research methods. Purpose of the work: study of the chemical composition of accessory monazite from granitoids of the crystalline basement of the South Yamal and determination of its age. Research methodology: quantitative analysis of the chemical composition of monazite was carried out using X-ray spectral electron probe microanalyzer CAMECA SX 100 (electron beam diameter from 1 μm, BSE, SE, Cat modes, determination of elements from beryllium to uranium). The spectra were obtained with the help of inclined wave spectrometers, the intensity was measured using analytical lines: Th Ma, U Mb, Pb Ma, Y La, Si Ka, Ca Ka, P Ka, Ce La, La La, Pr Lb, Nd La, Sm Lb, Dy La, Gd Lb. The age calculation was carried out according to the well-known methods of foreign authors in addition to some developments of the author. Results. The chemical composition of monazite makes it possible to classify it as a cerium variety, the content of radiogenic components varies greatly (in wt.%): ThO2 – 5.37–16.31, UO2 – 0.40–0.81, PbO – 0.08–0,19. There are significant concentrations of SiO2 (up to 3.5 wt.%), Y2 O3 (up to 1.8 wt.%) and CaO (up to 1.2 wt.%). It turns out that monazite implements hattonite (Th4+(U4+)+Si4+ → REE3++P5+) and cheralite (Th4+(U4+)+Ca2+(Sr2+,Ba2+,Pb2+) → 2REE3+) isomorphism types. The decent content of lead and high crystallinity of the substance makes it possible to use this mineral as a geochronometer mineral. Conclusions. New data on the chemical composition of monazite have been obtained, and the late Permian age of granitoids has been determined by microprobe dating. The values of the point U–Th–Pb ages of monazite together give a weighted average age of 256 ± 10 Ma (MSWD = 0.15) and an isochron of 254 ± 19 Ma (MSWD = 0.28), which almost ideally coincides with the results of isotopic U–Pb zircon dating from the same rock, 254 ± 3 Ma.

scholarly journals The Los Llantenes Formation in the Precordillera of Jagüe (La Rioja Province) and the recognition of a rifting stage in the early evolution of the late Paleozoic basins in western Argentina.

2011 ◽  
Vol 38 (2) ◽  
pp. 245 ◽  
Author(s):  
Ricardo A. Astini ◽  
Federico Martina ◽  
Federico M. Davila
Keyword(s):  
Coarse Grained ◽  
Areal Extent ◽  
The South ◽  
Great Thickness ◽  
Basement Rocks ◽  
Upper Paleozoic ◽  
Basal Section ◽  
History Of ◽  
Low Efficiency ◽  
La Rioja

In the northern part of the Argentine Precordillera, northwestern La Rioja, the Upper Paleozoic is over 4,000 m thick. Very coarse conglomerates from the basal section have not been described nor adequately interpreted. This work analyses this unit in the context of a stratigraphic revision of the upper Paleozoic of the region, and interprets the conglomerate as a rift deposit. The thick (>1,000 m) and coarse purple conglomeratic succession, herein named ‘Los Llantenes Formation’, non-conformably rests on the basement rocks of the region and underlies deposits of the first glacial record associated with the Gondwanan glaciation. While its great thickness and restricted areal extent indicate localized subsidence, the crude stratification, poor sorting and abundance of >1-m boulders indicate an origin related to high-gradient, low-efficiency alluvial fans. Their composition and coarse-grained size indicate local provenance, abrupt relief and incipiently developed drainage systems and a highly compartmentalized and abrupt paleogeography. A complex glacial history generated deep ‘U’-shaped paleovalleys in the Los Llantenes Formation, developing paleovalleys that accommodated basal lodgment tills and glacial diamictites with sedimentologic features comparable to the Cerro Tres Condores Formation (Visean in age) exposed to the south. The age of the conglomerates of Los Llantenes Formation, clearly preglacial, can be stratigraphically bracketed between the Middle Devonian substrate cropping out to the south in the sierra de Las Minitas and the Middle Mississippian, age of the Cerro Tres Condores Formation. Consequently, Los Llantenes Formation may partly correlate with the Agua de Lucho Formation (Tournaisian-Vissean) that in the area of Rio del Penon, immediately to the south, underlies the glacigenic Cerro Tres Condores Formation. Mapping relationships with limited areal extent, together with the great thickness of Los Llantenes Formation and the local provenance, allow interpreting accommodation in extensional or pull-apart depocenters, conclusions that are relevant in order to reconstruct the history of the basin.

scholarly journals Replenishment of oil deposits from the position of a new concept of oil and gas formation

Georesursy ◽  
2019 ◽  
Vol 21 (4) ◽  
pp. 40-48 ◽  
Author(s):  
Renat Kh. Muslimov ◽  
Irina N. Plotnikova
Keyword(s):  
Oil And Gas ◽  
Deep Structure ◽  
Sedimentary Cover ◽  
Crystalline Basement ◽  
The South ◽  
Gas Saturation ◽  
Oil Reserves ◽  
Long Term Study ◽  
The Earth ◽  
Deep Wells

The article is devoted to the problem of replenishing of oil reserves and considers it (the problem) in the aspect of deep degassing of the Earth. Based on an analysis of the results of a long-term study of the Precambrian crystalline basement in the territory of Tatarstan and adjacent areas, a number of new criteria are formulated that allow us to identify the processes of deep degassing of the Earth within the studied region. The article provides a brief overview of current views on the problem of replenishing oil reserves, considers options for possible sources and the mechanism of replenishment of hydrocarbons in the developed deposits. The arguments in favor of the modern process of deep degassing within the South Tatar arch and adjacent territories are examined, which are unequivocally confirmed by: the dynamics of the hydrochemical parameters of the deep waters of the crystalline basement obtained in the monitoring mode at five deep wells; uneven heat flux and its anomalies, recorded according to many years of research under the guidance of N.N. Khristoforova. The degassing processes are also confirmed by the dynamics of gas saturation of decompressed zones of the crystalline basement recorded in well 20009-Novoelkhovskaya, the dynamics of gas saturation of oil of the sedimentary cover and the composition of the gas dissolved in it, identified by oil studies in piezometric wells located in different areas of the Romashkinskoye field; the seismicity of the territory of Tatarstan, as well as its neotectonic activity. As criteria proving the existence of a process of replenishing the reserves of the developed oil fields of the South Tatar Arch, the features of the deep structure of the earth’s crust according to seismic data, as well as the results of geochemical studies of oils are considered.

scholarly journals THE ISLAND ARC FERROCORDIERITE-ALMANDINE PLAGIORHYOLITES OF THE MOUNT KASTEL, MOUNTAIN CRIMEA

2017 ◽  
pp. 15-21 ◽  
Author(s):  
E. M. Spiridonov
Keyword(s):  
Continental Crust ◽  
Late Jurassic ◽  
Crystalline Basement ◽  
Island Arc ◽  
Metamorphic Rocks ◽  
Moderate Pressure ◽  
The South ◽  
Tectonic Zone ◽  
First Time

Plagio rhyolites of the Pre-Late Jurassic dyke contain restitegamet (cribrate inter grow ths of almandinespessartine and quartz) and ferrocordierite. The garnets of such habit and composition and with such kind of zonality - the content of Mg increases and the content of Mn decreases from the center to the edges - are typical for ferriferous metapelites of amphibotite facies. Composition of the rocks, during palingenesis of which the melt of plagiorhyolites of the Mount Kastel formed, probably corresponded to the cordierite-almandine plagiogneisses. An assessment of the parameters of these metamorphic rocks forming according garnet and cordierite compositions is »550° С and 4 kbar, so they are metamorphic rocks of the amphibotite facies of moderate pressure. There is an assumption, that Mountain Crime a tectonic zone was possibly formed on the ancient crystalline basement, on the mature continental crust, possible continuation of the structures of Russian Plattorm to the south. Ferro cordierite - sekaninaite has been described in Crimea for the first time. A part of garnet and cordiertte was replaced by highly ferriferous chlorite (daphnite) and pumpellyite-(Fe), a part of biotite, titanomagnetite and ilmenite - by chlorite, epidote, pumpellyite-(Fe) and mineral with intermediate compotition between titantte and vuagnatite. The reby, plagio rhyoltes were subj ected by metamorphism of prehnite-pumpellyite facies.

scholarly journals Mineral types of gold deposits and regularities of their distribution in south-eastern part of the East Sayan

2019 ◽  
Vol 61 (2) ◽  
pp. 23-38
Author(s):  
B. B. Damdinov
Keyword(s):  
Gold Deposits ◽  
Crystalline Basement ◽  
The South ◽  
Genetic Characteristics ◽  
Gold Telluride ◽  
South Eastern ◽  
Leading Role ◽  
Mineral Associations ◽  
Metallogenic Zone ◽  
Gold Bearing

Based on the mineral composition, gold deposits of the south-eastern part of the East Sayan were typed. The most informative classification criterion for typing is the composition of the gold producing ore mineral associations which are specific to each of the selected types. Whereas using other criteria different structural, composition or genetic characteristics of deposits will necessarily overlap. Eight mineral types of deposits, characterizing the main gold-bearing ore mineral associations were identified: gold-polysulfide, gold-quartz, gold-telluride, gold-tetradymite, gold-stibnite, gold-bismuth-sulfosalt, gold-pyrrhotite and gold-fahlore types. Regional metallogenic divisions such as structural metallogenic zones, differ somewhat in the characteristics of mineralization. Thus, within the Bokson-Garganskaya metallogenic zone, gold-quartz, gold-polysulfide and gold-pyrrhotite types dominate, although gold-telluride and gold-bismuth-sulfosalt types are common in the western part of this zone. In the Ilchir zone, gold-fahlore type deposits are developed. Khamsarinskaya zone is characterized by gold-tetradimite and gold-antimonite deposits existence. It has been established that the mineral types of deposits formation depend on the enclosing rock complexes composition. Thus, gold-quartz, gold-polysulfide and gold-pyrrhotite types are formed in association with the ophiolites and rocks of the Archean crystalline basement. At the deposits associated with granitoid massifs, minerals of metalloids, such as bismuth-bearing sulfosalts, stibnite, tetradimite and tellurides, take a leading role in ores. In the carbonate strata, a gold-fahlore type is formed. The proposed classification allows typing all known gold deposits in the south-eastern part of the East Sayan and can be applied to adjacent regions.

Sign in / Sign up

Export Citation Format

Share Document