CRUSTS OF WEATHERING AS BASIC SUPPLIERS OF TERRIGENOUS MATERIAL DURING FORMATION OF ANCIENT DIAMONDIFEROUS PLACERS

2018 ◽  
pp. 24-32
Author(s):  
N. N. Zinchuk
Keyword(s):  
Mineral Composition ◽  
Siberian Platform ◽  
Carbonate Rocks ◽  
Material Removal ◽  
Late Triassic ◽  
Terrigenous Material ◽  
Source Areas ◽  
Local Sources ◽  
Sedimentation Basins ◽  
Thick Layers

On the example of Mesozoic deposits of one of the main diamondiferous regions of the Siberian platform, basic suppliers of terrigenous material into the ancient diamondiferous placers under formation and their occurrences have been characterized. Special attention has been paid to characteristics of local sources of allothigenous material removal to sedimentation basins of the said period, the main of which were Middle-Late Triassic crusts of weathering on terrigenous-carbonate rocks, formations of trappean origin (dolerites, tuffs, tufogene thick layers) and kimberlites. Comparatively short transfer of weathering products and their accumulation mainly in freshwater continental basins determined weak hydrothermal effect of environment on allothigenous minerals. The received specific features of the mineral composition of various rocks' crusts of weathering have been recommended for application during paleogeographical reconstructions in diamondiferous regions, to determine source areas of terrigenous material, in particular. The stated recommendations have been implemented when assessing material from local sources of drift (including diamondiferous material as well) to continental (Irelyakh and Ukugut suites) and coastal (Pliensbachian and Toarcian stages) deposits of MaloBOtuobinsky region, where primary and placer diamond deposits are successfully mined.

scholarly journals LITHOLOGIC-MINERALOGICAL FEATURES OF ANCIENT DIAMONDIFEROUS THICKNESSES IN THE REGIONS OF KIMBERLITE MAGMATISM DEVELOPMENT

2021 ◽  
Author(s):  
N.N. Zinchuk ◽  
◽  
M.N. Zinchuk ◽  
Keyword(s):  
Siberian Platform ◽  
Carbonate Rocks ◽  
Upper Triassic ◽  
Structural Formation ◽  
Thick Layers

Complex research of ancient crusts of weathering on terrigenous-carbonate rocks, dolerites, tufogene formations and kimberlites, as well as products of their rewashing in Mesozoic sedimentary thick layers of main diamondiferous regions of the Siberian platform allowed restoring specific features of their structural-formation generation Results of investigations allowed carrying out zoning of the territory on the area of the following distinction of Middle-Upper Triassic crusts of weathering and products of their redeposition: a) unfavorable (lower parts of paleo-depressions); b) favorable (upper parts of paleo-depressions); c) highly favorable (slopes of these structures). The identified typomorphic features of various minerals in various types of crusts of weathering may be successfully used when trying to determine their (including diamondiferous material) impact on various levels of Mesozoic sedimentary thick layers of the region.

PECULIARITIES OF DISTRIBUTION AND COMPOSITION OF BETAFITE FROM DIFFERENT FORMATIONS OF THE ALDAN SHIELD (SAKHA-YAKUTIA)

2019 ◽  
pp. 8-15
Author(s):  
V. Guliy ◽  
I. Poberezhska ◽  
N. Bilyk
Keyword(s):  
Chemical Composition ◽  
Mineral Composition ◽  
Oxygen Isotopes ◽  
Carbonate Rocks ◽  
Aldan Shield ◽  
Mineralogical Composition ◽  
Significant Feature ◽  
Carbon And Oxygen Isotopes ◽  
Primary Composition ◽  
Geological Formations

Character of Nb and Ta distribution in the different geological formations of the Aldan Shield are given in this article. To get idea about betafite from different endogenic etalon formations the authors analyzed its well known locations in the pegmatites, skarns, carbonatites, metasomatites and late veins segregations. Geological setting and mineralogical composition of the apatite-bearing rocks from the Aldan Shield are described, and the most significant in scale metamorphosed carbonate and silicate varieties among them have been distinguished. Apatite mineralization in magnesium skarns and metasomatites is developed locally. Titanite and betafite are the main concentrators of Nb and Ta and apatite is typical accompanying mineral in the studied rocks. Betafite was detected in the pegmatite bodies from magnesium skarns and metasomatites of the Shield with irregular distribution within rocks rich and poor in apatite, but was not found in the most developed apatite-carbonate rocks which are regarded as ores of the Seligdar type, so it cannot be mineralogical indicator for this type of ores. Late carbonate generations are significantly enriched in light carbon and oxygen isotopes in contrast to positive δ13Ñ values in apatitecarbonate bodies of the Seligdar deposit and its family and the highest δ18Î values. We used these indicators to distinguish origin of the rocks with various carbonate generations, which have different amounts of betafite. Appearance of betafite is determined by primary composition of the initial rocks. Chemical composition of betafites from the skarns and metasomatites is similar, but with local variations. The most significant feature of the mineral composition is very low Ta content. Titanite is characterized by variable amounts of Nb and Ta in scale of sectors as well as within separate grains.

scholarly journals LITHOLOGICAL AND FACIAL FEATURES, COMPOSITION, AND SEDIMENTATION CONDITIONS OF TERRIGENOUS-CARBONATE ROCKS OF THE MOTY GROUP (SHAMAN CLIFF, IRKUTSK REGION)

2021 ◽  
Vol 12 (3) ◽  
pp. 628-644
Author(s):  
Z. L. Motova ◽  
A. V. Plyusnin ◽  
E. V. Nikulin
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Siberian Platform ◽  
Carbonate Rocks ◽  
Facial Features ◽  
Upper Vendian ◽  
Terrigenous Rocks ◽  
Irkutsk Region ◽  
The Cross ◽  
Sedimentation Conditions

We have studied terrigenous-carbonate rocks in the area near the Sayan mountains in the Irkutsk Region (Russia), specifically at the Shaman Cliff, being the stratotype area of rocks that belong to the Moty group. The cliff’s lower part is composed of sandstones, which fragments gradually decrease in size upward the cross-section. The middle and upper parts are composed of sandy dolomites and dolomites, respectively. In terms of material characteristics, the terrigenous rocks correspond to arkoses. According to the genetic typification, the arkoses are composed of destructed primary igneous rocks. The terrigenous-carbonate rocks contain a carbonate component that gradually increases in the upper part of the cross-section. In the Shaman Cliff cross-section, we distinguish 32 lithological units and eight lithologicalgenetic types of deposits. Paleogeodynamic conditions are reconstructed for the formation of the sedimentation basin. Our study of the Shaman formation reveals specific features of the lithological facies, which suggest that these rocks accumulated in a coastal environment affected by tides. In the study area, clastic materials were mainly removed from an orogen that formed due to the Vendian accretion-collision events in the southern folded frame of the Siberian platform. Dolomites composing the upper part of the cliff are attributed to the Irkutsk formation of the Moty group. Their lithological features give evidence of shallow-marine conditions of their formation, without any supply of clastic material, which contributed to mass dispersal of the Cambrian biota described in [Marusin et al., 2021]. It is our first initiative to draw a boundary between the Shaman and Irkutsk formations of the Moty Group along the base of the carbonate eluvial breccia unit that marks the stratigraphic break. In the cross-section, this boundary represents the border between the Upper Vendian and Lower Cambrian.Our conclusions are generally consistent with the ideas of most researchers about the Late Vendian evolution of the southern margin of the Siberian platform. The results of our study can be used in further investigation of this area and provide a basis for correlating the studied strata with the same-age reference cross-sections of other regions in Siberia.

scholarly journals Typomorphic features of diamonds from ancient sedimentary thick layers of platforms’ central parts

2020 ◽  
pp. 13-19
Author(s):  
M. M. Zinchuk
Keyword(s):  
Siberian Platform ◽  
Upper Mantle ◽  
Primary Sources ◽  
Complex Investigation ◽  
Upper Paleozoic ◽  
Deep Faults ◽  
Middle Paleozoic ◽  
Actual Material ◽  
Practical Conclusion ◽  
Thick Layers

Basing on generalization of large actual material on complex investigation of diamond its characteristic in Upper Paleozoic and Mesozoic sedimentary thick layers of the Siberian platform is provided. Special attention is paid to the Central-Siberian sub-province, where it is convincingly shown that the area of development of individual diamond macro-associations is limited by a specific diamondiferous region, within which complexes of different in age terrigenous and coastal Upper Paleozoic and Mesozoic sediments are developed. Identified in some diamondiferous regions proximity of typomorphic features of diamonds in sedimentary thick layers of these ages testifies about formation of these collectors due to washout of more ancient productive layers or Middle Paleozoic primary sources. Polygeny of mineralogical associations of diamonds from different in age placers within some diamondiferous regions was noted, which may be successfully used when forecasting and prospecting primary sources of the mineral. Diamond and its tipomorphic features are one of the main criteria for forecasting and searching for root sources Materials on heterogeneity of the Viljujsko-Marhinska zone of deep faults with respect to productive kimberlite magmatism, which is associated with areals of the hard consolidated basement of the Archean age (Botuobinskij and Tjungskij cratons) obtained in the framework of medium scale forecast and search studies of typomophic features of diamonds have an important practical conclusion. The results of a study of the typomorphic features of diamonds from the most well-studied kimberlite bodies indicatle heterogeneities in the structure of the upper mantle even within the Central Siberian diamondiferous subprovince, especially with respect to the distributionof focirly rare coloured crystals (II, III and IV varieties) presumably of ecbgite genesis, associated with deep diamandiferous xenoliths of various composition. These varieties of diamonds are rare and accessory in kimberlite bodies, however their findings in rashes even in a single amount, can serve as a basis for localizing the territory of the search for indigenous sources. The analysis of typomorphic features of diamonds indicates the high prospectivity of placer oceurrences of the Central Siberian diamondiferous pronnce for the discovety of new highly productive kimberlite pipes.

scholarly journals ABOUT ANCIENT SOURCES OF DIAMONDS PLACERS

2018 ◽  
pp. 44-54
Author(s):  
N. N. ZINCHUK
Keyword(s):  
Siberian Platform ◽  
Primary Sources ◽  
Complex Investigation ◽  
North East ◽  
The North ◽  
Upper Paleozoic ◽  
Middle Paleozoic ◽  
History Of ◽  
Recent Sediments ◽  
Thick Layers

Basing on generalization of large actual material on complex investigation of diamond, its characteristic in Upper Paleozoic and  Mesozoic sedimentary thick layers of the Siberian platform has been  provided. It has allowed receiving new data on composition features  and distribution of diamond in recent sediments of main  diamondiferous regions of Lena-Anabar, Central-Siberian and  Tungusskaya sub-provinces. On the north-east of Siberian platform,  the region of Kyutyungdinsky graben and nearby territories,  perspective for the discovery of rich kimberlite bodies with specific  dia- monds, are of the most interest. Special attention has been paid to the Central-Siberian sub-province, where it has been convincingly  shown that the area of development of individual diamond macro- associations is limited by a specific diamondiferous region, within  which complexes of different in age terrigenous and coastal Upper  Paleozoic and Mesozoic sediments are developed. The complex of  features of diamonds from placers of the described platform testifies  by morphology, coloration, hard inclusions, internal structure,  photoluminescence and admixture composition about plurality of  primary sources and availability of still undiscovered kimberlite  bodies within many diamondiferous regions. Application of  typomorphic features of crystals for restoration of exogenous history of diamonds on the path from primary sources to the sites of modern allocation in placers, as well as for paleogeographical reconstructions of distribution of ancient productive thick layers and clarification of  diamondiferous material drift direction, has a significant importance.  Proximity of typomorphic features of diamonds in sedimentary thick  layers of these ages, identified in some diamondiferous regions,  testifies about formation of these collectors due to washout of more  ancient productive layers or Middle Paleozoic primary sources.  Polygeny of mineralogical associations of diamonds from different in age placers within some diamondiferous regions has been noted,  which may be successfully used when forecasting and prospecting primary sources of the mineral.

scholarly journals Mexico: Basement framework and pre-Cretaceous stratigraphy

2020 ◽  
Author(s):  
Uwe C. Martens ◽  
Roberto S. Molina Garza
Keyword(s):  
Gulf Of Mexico ◽  
Detrital Zircon ◽  
Source Area ◽  
White Mica ◽  
Late Triassic ◽  
Source Areas ◽  
Local Character ◽  
South Central ◽  
Specific Source ◽  
Maya Mountains

ABSTRACT Provenance determinations of sediment deposited in circum–Gulf of Mexico basins rely on understanding the geologic elements present in the basement provinces located from northeast Mexico to Honduras. Relevant geologic features of these provinces are herein summarized in text and pictorial form, and they include the Huizachal-Peregrina uplift, western Gulf of Mexico, Huayacocotla, Zapoteco, Mixteca, Xolapa, Juchatengo, Cuicateco, Mixtequita, south-central Chiapas, southeast Chiapas, western Guatemala, central Guatemala, Maya Mountains, and the Chortis block. We recognized basement elements of local character that serve as fingerprints for specific source areas. However, many elements are ubiquitous, such as 1.4–0.9 Ga, high-grade metamorphic rocks that occur both as broad exposures and as inliers in otherwise reworked crust. Xenocrystic and detrital zircon of Mesoproterozoic age is very common and hence not diagnostic of provenance. Neoproterozoic rocks are very scarce in Mexican basement provinces. However, Ediacaran–Cambrian detrital zircon grains are found in Mexican Paleozoic strata; these were possibly derived from distant sources in Gondwana and Pangea. Ordovician–Silurian magmatism is present in approximately half the provinces; magmatic detrital zircon of such age is somewhat informative in terms of provenance. More useful populations are detrital zircon grains with Ordovician–Silurian metamorphic overgrowth, which seem to be mainly sourced from the Mixteca region or the southern Chiapas Massif. Devonian basement has only been discovered in the Maya Mountains of Belize, and detrital zir-on of such age seems to be characteristic of that source. A similar case can be made about Carboniferous zircon and the Acatlán Complex, Middle Pennsylvanian zircon and Juchatengo plutons, and Late Triassic zircon and the basement exposed in central Guatemala. In all these cases, the age and geographic extent of the zircon source are restricted and serve as a distinct fingerprint. Plutons of Permian–Early Triassic age are widespread, and detrital zircon grains from them are rather nonspecific indicators of source area. Future dating of detrital white mica using 40Ar-39Ar could help in recognizing Carboniferous–Triassic schist from more restricted schist occurrences such as west Cuicateco (Early Cretaceous) and central Guatemala (Late Cretaceous).

Are carbonates from the India-Asia collision remagnetized ? 

2021 ◽  
Author(s):  
Pierrick Roperch ◽  
Guillaume Dupont-Nivet
Keyword(s):  
Carbonate Rocks ◽  
Optical Microscope ◽  
Late Triassic ◽  
The Tibetan Plateau ◽  
Iron Hydroxides ◽  
Knowing That ◽  
Reflected Light ◽  
Scanning Electron Microscope Data ◽  
Electron Microscope Data ◽  
Tethyan Himalaya

<p>Widespread carbonate rocks from the Tibetan plateau have been extensively used to constrain terrane paleolatitudes involved in the India-Asia collision. However, their reliability in preserving a primary magnetization has been recently put into question.<span>  </span>A transformation of pyrite to magnetite has been recently proposed as a cause for late re-magnetizations in Paleocene Tethyan Himalaya carbonates (1) and late Triassic carbonates from the Qiantang (2), thus discarding such Characteristic Remanent Magnetizations (ChRM) for tectonic purposes. We have re-examined the paleomagnetic data obtained on late Triassic carbonate rocks from the Qiantang. Our SEM observations indicate pristine pyrite in non-weathered carbonate rocks. Optical microscope observations in reflected light demonstrate that pyrite, when it is weathered, is transformed to iron hydroxides minerals but not to magnetite. This is at odds with previously proposed pyrite to magnetite transformation hypothesis mainly based on interpretations of Scanning Electron Microscope data (SEM/EDS). We thus interpret the ChRM more likely related to an early diagenetic magnetization of Late Triassic age. Knowing that the arguments put forward for a remagnetization of Triassic carbonates are the same as those proposed for the remagnetization of Paleocene carbonates, the ChRM in some Paleocene carbonates could also be of early diagenetic origin. However, there is also a growing number of studies where remagnetization is obvious in the Tethyan Himalaya and undetected remagnetizations (3) are likely the cause of the large differences in the estimation of the size of Greater India. These examples show the urgent need to publish the complete demagnetization dataset in an open database like MAGIC or the FAIR data initiative from (4) in order to reassess previous interpretations if we want to solve problems like the size of Greater India and hypothesis like the Greater India basin.</p><p>(1) doi:10.1002/2016JB013662 ; (2) doi:10.1016/j.epsl.2019.06.035 ; (3) doi:10.1016/j.epsl.2020.116330; (4) doi:10.1029/2019GC008838.</p><p> </p>

Late Triassic high-potassium trachitic volcanism of the northeast of the Siberian platform: Evidence in the sedimentary record

2014 ◽  
Vol 459 (1) ◽  
pp. 1344-1347 ◽  
Author(s):  
E. F. Letnikova ◽  
A. E. Izokh ◽  
E. I. Nikolenko ◽  
N. P. Pokhilenko ◽  
V. O. Shelestov ◽  
...  
Keyword(s):  
Siberian Platform ◽  
Late Triassic ◽  
Sedimentary Record ◽  
High Potassium

Pb–Pb Age of Carbonate Rocks of the Kamo Group, Baikit Anteclise of the Siberian Platform

2021 ◽  
Vol 500 (1) ◽  
pp. 715-719
Author(s):  
I. M. Gorokhov ◽  
A. B. Kuznetsov ◽  
I. M. Vasilieva ◽  
A. Yu. Kramchaninov ◽  
N. G. Rizvanova ◽  
...  
Keyword(s):  
Siberian Platform ◽  
Carbonate Rocks
Sign in / Sign up

Export Citation Format

Share Document