scholarly journals Paleomagnetism of the Sette-Daban Meso-Neoproterozoic magmatic complex of the southeastern margin of the Siberian platform

2021 ◽  
Vol 66 (4) ◽  
Author(s):  
Aleksandr D. Savelev ◽  
◽  
Anna A. Pazukhina ◽  
Aleksandr M. Pasenko ◽  
◽  
...  
Keyword(s):  
Siberian Platform ◽  
Sedimentary Rocks ◽  
Yenisei Ridge ◽  
Geochemical Data ◽  
Magmatic Complex ◽  
Paleomagnetic Pole ◽  
Southeastern Margin ◽  
History Of ◽  
Age Limits ◽  
Characteristic Component

The interval of ~ 1000 - ~ 900 Ma is one of the key ones in the history of the evolution of the Siberian Platform. At this time, the formation of the neoproterozoic supercontinent Rodinia took place, which undoubtedly found its reflection in the geological annals of Siberia. A reflection of the kinematics of the Siberian platform is its apparent pole wander path (APWP), the development of which will help to clarify the geodynamic in which the platform was at the beginning of the Neoproterozoic. However, not many objects of this age are known within the Siberian Platform, suitable for performing paleomagnetic determinations. The consequence of this is a very limited number of existing reliable poles, obtained either from sedimentary rocks with very imprecise age limits, or from rocks of the Yenisei Ridge and Taimyr with an ambiguous structural position. This paper presents the results of paleomagnetic studies of the Proterozoic igneous rocks of the Sette-Daban complex of the southern Verkhoyansk region, the formation of which took place ~ 1000-970 Ma ago. Detailed thermal magnetic cleaning made it possible to reveal the high-temperature (HT) characteristic component in a significant part of the samples. It has maximum unblocking temperatures of about 580 ° C, lying in the region of the Curie point of magnetite. The average direction of the characteristic component for the sills sampled in the valley of the Yudoma, coincides with the direction obtained earlier on the same bodies. The calculated paleomagnetic pole for the intrusive bodies of the Sette-Daban magmatic complex (Plat = 5.8 °, Plong = 182.9 °, dp / dm = 9.0 ° / 14.4 °) confirms and refines the previously obtained pole for the rocks of this complex, and also indicates that Siberia in the range of ~ 970-1000 Ma was located in the northern hemisphere in tropical latitudes (~ 26 ° N). The analysis of the available geochronological and geochemical data, coupled with new paleomagnetic data, made it possible to clarify the age of the Sette-Daban magmatic event and limit it within ~ 970-1000 Ma.

scholarly journals PALEOMAGNETISM OF THE MIDDLE JURASSIC SEDIMENTARY ROCKS OF THE ELGON FORMATION OF THE ULBAN TERRANE

2021 ◽  
Vol 40 (3) ◽  
pp. 3-15
Author(s):  
A.Yu. Peskov ◽  
◽  
A.V. Kudymov ◽  
S.V. Zyabrev ◽  
A.S. Karetnikov ◽  
...  
Keyword(s):  
Middle Jurassic ◽  
Sedimentary Rocks ◽  
Magnetization Vector ◽  
Sikhote Alin ◽  
Paleomagnetic Pole ◽  
Inclination Shallowing ◽  
New Findings ◽  
Show Evidence ◽  
Formed Part ◽  
Characteristic Component

The paper presents new findings of paleomagnetic studies on Middle Jurassic sedimentary rocks of the Elgon Formation of the Ulban Terrane from coastal outcrops along the Ulban Bay (53.5°N, 137.7°E). Demagnetization yielded a pre-folding characteristic component of magnetization. No inclination shallowing effect for the characteristic magnetization vector was revealed in sandstone specimens of the Elgon Formation. The coordinates of the paleomagnetic pole and the paleolatitude at which the studied rocks deposited were calculated: Plat = -34.3 (34.3)°; Plong = 161.2 (341.2)°; dm = 2.7 dp = 5.3, paleolatitude = 0.1° (+2.7°/-2.6°) S. The acquired paleomagnetic data show evidence for the deposition of rocks of the Ulban Terrane in the Middle Jurassic at the boundary between the Asian paleocontinent and the Paleo-Pacific which later formed part of the Sikhote-Alin Orogenic Belt.

U–Pb ages and tectonic significance of late Archean alkalic magmatism and nonmarine sedimentation: Timiskaming Group, southern Abitibi belt, Ontario

1991 ◽  
Vol 28 (4) ◽  
pp. 489-503 ◽  
Author(s):  
F. Corfu ◽  
S. L. Jackson ◽  
R. H. Sutcliffe
Keyword(s):  
Greenstone Belt ◽  
Early Stage ◽  
Sedimentary Rocks ◽  
Detrital Zircons ◽  
Geochemical Data ◽  
Lake Area ◽  
Quartz Porphyry ◽  
Bear Lake ◽  
Lake Formation ◽  
Dominant Period

The paper presents U–Pb ages for zircons of the calc-alkalic to alkalic igneous suite and associated alluvial–fluvial sedimentary rocks of the Timiskaming Group in the late Archean Abitibi greenstone belt, Superior Province. The Timiskaming Group rests unconformably on pre-2700 Ma komatiitic to calc-alkalic volcanic sequences and is the expression of the latest stages of magmatism and tectonism that shaped the greenstone belt. An age of 2685 ± 3 Ma for the Bidgood quartz porphyry, an age of about 2685–2682 Ma for a quartz–feldspar porphyry clast in a conglomerate, and ages ranging from 2686 to 2680 Ma for detrital zircons in sandstones appear to reflect an early stage in the development of the Timiskaming Group. The youngest detrital zircons in each of three sandstones at Timmins, Kirkland Lake, and south of Larder Lake define maximum ages of sedimentation at about 2679 Ma; the latter sandstone is cut by a porphyry dyke dated by titanite at [Formula: see text], identical to the 2677 ± 2 Ma age for a volcanic agglomerate of the Bear Lake Formation north of Larder Lake. Similar ages have previously been reported for syenitic to granitic plutons of the region. The dominant period of Timiskaming sedimentation and magmatism was thus 2680–2677 Ma. Xenocrystic zircons found in a porphyry and a lamprophyre dyke have ages of 2750–2720 Ma, which correspond to the ages of the oldest units in the belt, predating the volumetrically dominant ca. 2700 Ma greenstone sequences. The presence of these xenocrysts and the onlapping of the Timiskaming Group on all earlier lithotectonic units of the southern Abitibi belt support the concept that the 2700 Ma ensimatic sequences were thrust onto older assemblages during a phase of compression that culminated with the generation of tonalite and granodiorite at about 2695–2688 Ma. Published geochemical data for the Timiskaming igneous suite, notably the enrichments in large-ion lithophile elements and light rare-earth elements and the relative depletion of Nb, Ta, and Ti compare with the characteristics of suites at modern convergent settings such as the Eolian and the Banda arcs and are consistent with generation of the melts from deep metasomatized mantle in the final stages of, or after cessation of, subduction. Late- and post-Timiskaming compression caused north-directed thrusting and folding. Turbiditic sedimentary units of the Larder Lake area which locally structurally overly the alluvial–fluvial sequence and were earlier thought to be part of the Timiskaming Group, appear to be older "flyschoid" sequences, possibly correlative with sedimentary rocks deposited in the Porcupine syncline at Timmins between 2700 and 2690 Ma.

Provenance of Jurassic sedimentary rocks of south-central Quesnellia, British Columbia: implications for paleogeography

2004 ◽  
Vol 41 (1) ◽  
pp. 103-125 ◽  
Author(s):  
Nathan T Petersen ◽  
Paul L Smith ◽  
James K Mortensen ◽  
Robert A Creaser ◽  
Howard W Tipper
Keyword(s):  
Detrital Zircon ◽  
Middle Jurassic ◽  
Sedimentary Rocks ◽  
Source Area ◽  
Lower Jurassic ◽  
Early Jurassic ◽  
Late Triassic ◽  
Nd Isotopes ◽  
South Central ◽  
History Of

Jurassic sedimentary rocks of southern to central Quesnellia record the history of the Quesnellian magmatic arc and reflect increasing continental influence throughout the Jurassic history of the terrane. Standard petrographic point counts, geochemistry, Sm–Nd isotopes and detrital zircon geochronology, were employed to study provenance of rocks obtained from three areas of the terrane. Lower Jurassic sedimentary rocks, classified by inferred proximity to their source areas as proximal or proximal basin are derived from an arc source area. Sandstones of this age are immature. The rocks are geochemically and isotopically primitive. Detrital zircon populations, based on a limited number of analyses, have homogeneous Late Triassic or Early Jurassic ages, reflecting local derivation from Quesnellian arc sources. Middle Jurassic proximal and proximal basin sedimentary rocks show a trend toward more evolved mature sediments and evolved geochemical characteristics. The sandstones show a change to more mature grain components when compared with Lower Jurassic sedimentary rocks. There is a decrease in εNdT values of the sedimentary rocks and Proterozoic detrital zircon grains are present. This change is probably due to a combination of two factors: (1) pre-Middle Jurassic erosion of the Late Triassic – Early Jurassic arc of Quesnellia, making it a less dominant source, and (2) the increase in importance of the eastern parts of Quesnellia and the pericratonic terranes, such as Kootenay Terrane, both with characteristically more evolved isotopic values. Basin shale environments throughout the Jurassic show continental influence that is reflected in the evolved geochemistry and Sm–Nd isotopes of the sedimentary rocks. The data suggest southern Quesnellia received material from the North American continent throughout the Jurassic but that this continental influence was diluted by proximal arc sources in the rocks of proximal derivation. The presence of continent-derived material in the distal sedimentary rocks of this study suggests that southern Quesnellia is comparable to known pericratonic terranes.

The History of the Extortion Court at Rome, 123–70 b.c.

1938 ◽  
Vol 14 ◽  
pp. 98-114 ◽  
Author(s):  
J. P. V. D. Balsdon
Keyword(s):  
Roman History ◽  
Precise Statement ◽  
History Of ◽  
Age Limits ◽  
First Time ◽  
The Way

The available evidence concerning the history of the Extortion Court, the quaestio repetundarum, at Rome is tabulated opposite page 114. In view of the bulk of this evidence, it is at first sight surprising that this should be one of the most confused chapters of Roman history. Indeed, it is improbable that all Roman historians would agree upon any more precise statement of certainty than the following: that C. Gracchus, whether by a lex Sempronia iudiciaria, or by a lex Sempronia de repetundis, or by a lex Acilia de repetundis which may, or may not, be reproduced in the lex repetundarum, fragments of which are preserved at Naples and at Vienna (CIL i, 583), established equites (selected either from owners and past owners, within certain age limits, of the equus publicus, or from all those who possessed the equestrian census) either in place of, or in association with, senators as jurors in the quaestio de repetundis; that Q. Servilius Caepio, probably in his consulship in 106 B.C., proposed, and perhaps carried, a judiciary law in the interest of the Senate; that C. Servilius Glaucia either in m (Mommsen), 108 (Carcopino) 104 (Last) or 101 B.C. (Niccolini) carried a lex repetundarum and perhaps other judiciary laws in which he possibly either gave for the first time, or restored, to the equites complete possession of the juries and certainly effected two reforms in procedure, (a) by legalising the prosecution not only of recent magistrates and pro-magistrates, but also of their accomplices and (b) by introducing the form of ‘double action’ known as comperendinatio; that M. Livius Drusus, as tribune in 91 B.C., endeavoured unsuccessfully to establish, or to re-establish, as the case may be, mixed juries of senators and equites, and to make equestrian as well as senatorial jurors liable to prosecution for accepting bribes; that in 89 B.C. by a lex Plautia of the tribune M. Plautius Silvanus mixed juries were established, certainly for trials of maiestas, and perhaps for repetundae too. After this, the way is clearer, Sulla re-established senatorial juries, which survived until 70 B.C., when, by the lex Aurelia, jurors were selected from three panels—from senators, equites and tribuni aerarii.

scholarly journals Lake-level variability in Salar de Coipasa, Bolivia during the past ∼40,000 yr

2018 ◽  
Vol 91 (2) ◽  
pp. 881-891 ◽  
Author(s):  
J. Andrew Nunnery ◽  
Sherilyn C. Fritz ◽  
Paul A. Baker ◽  
Wout Salenbien
Keyword(s):  
Lake Level ◽  
Sediment Accumulation ◽  
Geochemical Data ◽  
South American ◽  
Climate History ◽  
Oxygen Isotope Stage ◽  
The Past ◽  
History Of ◽  
Diatom Stratigraphy ◽  
The Last Glacial

AbstractVarious paleoclimatic records have been used to reconstruct the hydrologic history of the Altiplano, relating this history to past variability of the South American summer monsoon. Prior studies of the southern Altiplano, the location of the world’s largest salt flat, the Salar de Uyuni, and its neighbor, the Salar de Coipasa, generally agree in their reconstructions of the climate history of the past ∼24 ka. Some studies, however, have highly divergent climatic records and interpretations of earlier periods. In this study, lake-level variation was reconstructed from a ∼14-m-long sediment core from the Salar de Coipasa. These sediments span the last ∼40 ka. Lacustrine sediment accumulation was apparently continuous in the basin from ∼40 to 6 ka, with dry or very shallow conditions afterward. The fossil diatom stratigraphy and geochemical data (δ13C, δ15N, %Ca, C/N) indicate fluctuations in lake level from shallow to moderately deep, with the deepest conditions correlative with the Heinrich-1 and Younger Dryas events. The stratigraphy shows a continuous lake of variable depth and salinity during the last glacial maximum and latter stages of Marine Oxygen Isotope Stage 3 and is consistent with environmental inferences and the original chronology of a drill core from Salar de Uyuni.

Geochronology of the Belt Series, Montana

1968 ◽  
Vol 5 (3) ◽  
pp. 737-747 ◽  
Author(s):  
J. D. Obradovich ◽  
Z. E. Peterman
Keyword(s):  
Average Rate ◽  
Sedimentary Rocks ◽  
Time Interval ◽  
Depositional History ◽  
Middle Cambrian ◽  
Basement Rocks ◽  
Field Evidence ◽  
Minimum Age ◽  
History Of ◽  
Central Montana

This paper presents new radiometric data that permit some qualified statements to be made on the depositional history of the Belt sedimentary rocks. The period of deposition of sedimentary rocks of the Precambrian Belt Series has been placed within a broad time interval, for they rest on metamorphosed basement rock dated at ~ 1800 m.y. and are overlain by the Middle Cambrian Flathead Quartzite (circa 530 m.y.). Prior geochronometric data gathered during the last decade indicate most of the Belt Series to be older than ~ 1100 m.y.K–Ar and Rb–Sr techniques have been applied recently to a variety of samples selected from the whole gamut of the Belt Series. Glauconite from various formations in the sequence McNamara Formation down to the uppermost beds of the Empire Formation in the Sun River area has been dated at 1080 ± 27 m.y. by the K–Ar method and at 1095 ± 22 m.y. by the Rb–Sr mineral isochron method. A Rb–Sr whole-rock isochron based on argillaceous sedimentary rocks from this 5000-ft section gives an age of 1100 ± 53 m.y. The concordance of the preceding results and the K–Ar ages (1075 to 1110 m.y.) on Purcell sills and lava imply that this age represents the time of sedimentation of these units.A Rb–Sr isochron based on whole-rock samples stratigraphically far below the Umpire Formation— the Greyson Shale, Newland Limestone, Chamberlain Shale, and Neihart Quartzite in the Big Belt and Little Beit Mountains—yields an age of 1325 ± 15 m.y. This result is interpreted as indicating a substantial unconformity beneath the Belt Series, at least in central Montana; it also suggests a major hiatus, unsuspected from field evidence, between the uppermost part of the Empire Formation and the Greyson Shale.The results for the youngest of Belt rocks—the Pilcher Quartzite and the Garnet Range Formation, which are exposed in the Alberton region—are equivocal in that there is widespread dispersion. A large component of detrital muscovite in some of the samples could readily account for the magnitude and sense of this dispersion. A maximum age of ~930 m.y. based on an isochron of minimum slope through the various points may be inferred for this sequence. A K–Ar age of 760 m.y. obtained on biotite from a sill in the Garnet Range Formation provides a minimum age for these younger Belt rocks.Three distinct periods of sedimentation for Belt rocks sampled are suggested at ≥ 1300, 1100, and ≤ 900 m.y., with two substantial hiatuses of 200 m.y. or more. In addition the data for the sequence in the Big and Little Belt Mountains suggest that sedimentation may not have commenced for a period of possibly 400 m.y. after the metamorphism that affected basement rocks, while the data for the Garnet Range and Pilcher sequence suggest that sedimentation ceased some 200 to 400 m.y. prior to the deposition of the Middle Cambrian Flathead Quartzite.To suggest that the Belt sediments were deposited continuously over a period of 400 m.y. or more would imply an unusually low average rate of deposition of ≤ 0.1 ft/1000 yr, and this for the thickest part of the Belt Series. As a realistic expression of the depositional history of the Belt Series, both viewpoints are open to question, but the viewpoint that the Belt basin has been characterized by discontinuous sedimentation would be more in keeping with the principle of uniformity.

Thermal history of the Siberian platform: Apatite Fission-Track data from the Permian-Triassic magmatic complexes

2021 ◽  
Author(s):  
Tatyana Bagdasaryan ◽  
Roman Veselovskiy ◽  
Viktor Zaitsev ◽  
Anton Latyshev
Keyword(s):  
Siberian Platform ◽  
Thermal History ◽  
Fission Track ◽  
Sedimentary Cover ◽  
Geothermal Gradient ◽  
State University ◽  
Apatite Fission Track ◽  
History Of ◽  
Cover Up ◽  
Moscow State University

<p>The largest continental igneous province, the Siberian Traps, was formed within the Siberian platform at the Paleozoic-Mesozoic boundary, ca. 252 million years ago. Despite the continuous and extensive investigation of the duration and rate of trap magmatism on the Siberian platform, these questions are still debated. Moreover, the post-Paleozoic thermal history of the Siberian platform is almost unknown. This study aims to reconstruct the thermal history of the Siberian platform during the last 250 Myr using the low-temperature thermochronometry. We have studied intrusive complexes from different parts of the Siberian platform, such as the Kotuy dike, the Odikhincha, Magan and Essey ultrabasic alkaline massifs, the Norilsk-1 and Kontayskaya intrusions, and the Padunsky sill. We use apatite fission-track (AFT) thermochronology to assess the time since the rocks were cooled below 110℃. Obtained AFT ages (207-173 Ma) are much younger than available U-Pb and Ar/Ar ages of the traps. This pattern might be interpreted as a long cooling of the studied rocks after their emplacement ca. 250 Ma, but this looks quite unlikely because contradicts to the geological observations. Most likely, the rocks were buried under a thick volcanic-sedimentary cover and then exhumed and cooled below 110℃ ca. 207-173 Ma. Considering the increased geothermal gradient up to 50℃/km at that times, we can estimate the thickness of the removed overlying volcanic-sedimentary cover up to 207-173 Ma as about 2-3 km.</p><p>The research was carried out with the support of RFBR (grants 20-35-90066, 18-35-20058, 18-05-00590 and 18-05-70094) and the Program of development of Lomonosov Moscow State University.</p>

Estimation Update and Feedback Procedures

2008 ◽  
Author(s):  
P.J. Lee
Keyword(s):  
Water Saturation ◽  
Geophysical Data ◽  
Source Rocks ◽  
Geochemical Data ◽  
Burial History ◽  
Data Types ◽  
Petroleum Resource ◽  
History Of ◽  
Seismic Sections ◽  
Well Data

A basin or subsurface study, which is the first step in petroleum resource evaluation, requires the following types of data: • Reservoir data—pool area, net pay, porosity, water saturation, oil or gas formation volume factor, in-place volume, recoverable oil volume or marketable gas volume, temperature, pressure, density, recovery factors, gas composition, discovery date, and other parameters (refer to Lee et al., 1999, Section 3.1.2). • Well data—surface and bottom well locations; spud and completion dates; well elevation; history of status; formation drill and true depths; lithology; drill stem tests; core, gas, and fluid analyses; and mechanical logs. • Geochemical data—types of source rocks, burial history, and maturation history. • Geophysical data—prospect maps and seismic sections. Well data are essential when we construct structural contour, isopach, lithofacies, porosity, and other types of maps. Geophysical data assist us when we compile number-of-prospect distributions and they provide information for risk analysis.

Chapter 10: Olympiada Gold Deposit, Yenisei Ridge, Russia

2020 ◽  
pp. 203-226
Author(s):  
A. M. Sazonov ◽  
K. V. Lobanov ◽  
E. A. Zvyagina ◽  
S. I. Leontiev ◽  
S. A. Silyanov ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Gold Mineralization ◽  
Sedimentary Rocks ◽  
Gold Deposits ◽  
Yenisei Ridge ◽  
Structural Factors ◽  
Tectonic Zone ◽  
Central Siberia ◽  
Western Margin ◽  
Clastic Sedimentary

Abstract The Olympiada deposit, containing >1,560 metric tons (t; 50 Moz) of gold at an average grade of 4 to 4.6 g/t Au, occurs in central Siberia, Russia. Over 30 years, the deposit produced more than 580 t of gold, including 200 t from oxidized ore grading 11.1 g/t. The deposit forms a 2-km-long, steeply dipping system, which is traced downdip for 1.7 km. It occurs in the Neoproterozoic orogen of the Yenisei Ridge at the western margin of the Siberian craton. This and other gold deposits in the district are controlled by the large, long-lived Tatarka-Ishimbino tectonic zone, marking a suture between terranes chiefly consisting of deformed Meso- to Neoproterozoic carbonate-clastic sedimentary rocks. The combination of lithologic and structural factors was critical for localization of gold mineralization associated with calcic and siliceous alteration accompanied by early arsenic and late antimony sulfides. As a result, very fine (10 μm) and high fineness (910–997) gold associates with diverse sulfides, especially arsenopyrite, and commonly contains mercury, similar to some characteristics of Carlin-type deposits. Geochronologic studies suggest that mineralization was formed during several stages between 817 and 660 Ma. The isotopic composition of Os and He, along with presence of anomalous Ni, Co, and Pt, points to a mantle mafic source, whereas isotopic composition of Pb and S suggest a contaminated crustal source, i.e., originating from a mix of mantle and crustal fluids.

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