Geochemical studies of snow over mineral accumulations under conditions of their overlap by sedimentary rocks of the platform cover

The volcanogenic formations of the middle part of the Pronchishchev ridge are considered. Based on new data from the lithological, petrographic, geochemical studies of igneous and volcanogenic sedimentary rocks and stratigraphic studies of the Upper Permian-Lower Triassic terrigenous strata that enclose them, a model of their spatial relationship is proposed. It is shown that the dolerite body and the adjacent tuff breccia in the field of development of Upper Permian rocks as well as tuffite gravelites in the field of Lower Triassic rocks are a single complex of formations of different parts of the diatreme. The time of implantation of the diatreme is defined as the beginning of the Late Olenek. The wide development of vent facies dolerites in the diatreme may indicate the repeated activation of the supply channel.

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Aborted Proterozoic rifting in eastern Newfoundland

Canadian Journal of Earth Sciences ◽

10.1139/e78-010 ◽

1978 ◽

Vol 15 (1) ◽

pp. 117-131 ◽

Cited By ~ 37

Author(s):

D. F. Strong ◽

S. J. O'Brien ◽

S. W. Taylor ◽

P. G. Strong ◽

D. H. Wilton

Keyword(s):

Source Region ◽

Sedimentary Rocks ◽

Ocean Basin ◽

Geological Mapping ◽

Southwestern Part ◽

Bimodal Volcanism ◽

Intrusive Rocks ◽

Group A ◽

Geochemical Studies ◽

Alkalic Basalts

Recent geological mapping and geochemical studies of the late Proterozoic rocks of the Burin Peninsula in the southwestern part of the Avalon Zone of Newfoundland show the following sequence: (1) The basal Rock Harbour Group, a sedimentary assemblage ranging from conglomerates to turbidites, was derived from a subaerial volcanic–plutonic source region. (2) The overlying Burin Group, a belt of mafic volcanic and intrusive rocks that have alkalic affinities at the base but are dominated by oceanic tholeiite. (3) The Marystown Group, a bimodal sequence of alkalic basalts and rhyolites deposited in a subaerial environment unconformably above the Burin Group, and apparently conformably overlain by Infracambrian to Cambrian sedimentary rocks. Stromatolites occur within resedimented limestone breccias and conglomerates at the top of the Rock Harbour Group and throughout the Burin Group.These assemblages are interpreted to indicate that after a period of continental type bimodal volcanism, the Avalon terrain was rifted in Burin Group times to form some kind of small ocean basin, which was abruptly closed with a reversion to continental type bimodal volcanism of the Marystown Group.

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Age and sources of the Lower Mesozoic metasedimentary rocks of the Un'ja-Bom terrane in the Mongol-Okhotsk fold belt: results of the U–Th–Pb geohronological (LA–ICP–MS) AND Sm–Nd isotope studies

Доклады Академии наук ◽

10.31857/s0869-56524844455-459 ◽

2019 ◽

Vol 484 (4) ◽

pp. 455-459

Author(s):

V. A. Zaika ◽

A. A. Sorokin ◽

V. P. Kovach ◽

A. P. Sorokin ◽

A. B. Kotov

Keyword(s):

Sedimentary Rocks ◽

Detrital Zircons ◽

Fold Belt ◽

Relative Probability ◽

Nd Isotope ◽

Metasedimentary Rocks ◽

Icp Ms ◽

Isotope Studies ◽

Geochemical Studies ◽

Age Estimates

The results of the U—Th—Pb geochronological studies indicate that in the Un’ja-Bom terrane the youngest peaks on the relative probability curves of ages are 207 and 212 Ma for zircons from the metasiltstone of the Kurnal formation and from the metasiltstone of the Amkan formation. Similar age estimates for the youngest peaks were obtained for the detrital zircons from the metasedimentary rocks of the Tukuringra terrain of the eastern part of the Mongol-Okhotsk belt, which indicates that the Lower Mesozoic flyschoid complexes in the structure of this belt are developed much wider than is currently believed. The results obtained in our U—Th—Pb geochronological and Sm—Nd isotope geochemical studies suggest’s that the sedimentary rocks material was carried to the sedimentation basin mainly from the continental massifs of the Amur superterrane.

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Direct Observation of Crystalline Ordering In Naturally Graphitized Carbon Produced by Low Grade Metamorphism

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100078377 ◽

1977 ◽

Vol 35 ◽

pp. 162-163

Author(s):

Thomas R. McKee ◽

Peter R. Buseck

Keyword(s):

Crystallite Size ◽

Sedimentary Rocks ◽

Carbonaceous Material ◽

Low Grade ◽

X Ray ◽

Graphitized Carbon ◽

Transmission Electron ◽

Heat Treated ◽

Commercial Carbon ◽

Metamorphic Zone

Sediments commonly contain organic material which appears as refractory carbonaceous material in metamorphosed sedimentary rocks. Grew and others have shown that relative carbon content, crystallite size, X-ray crystallinity and development of well-ordered graphite crystal structure of the carbonaceous material increases with increasing metamorphic grade. The graphitization process is irreversible and appears to be continous from the amorphous to the completely graphitized stage. The most dramatic chemical and crystallographic changes take place within the chlorite metamorphic zone.The detailed X-ray investigation of crystallite size and crystalline ordering is complex and can best be investigated by other means such as high resolution transmission electron microscopy (HRTEM). The natural graphitization series is similar to that for heat-treated commercial carbon blacks, which have been successfully studied by HRTEM (Ban and others).

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Stabilizing pyritic material

The Paleontological Society Special Publications ◽

10.1017/s2475262200005207 ◽

1989 ◽

Vol 4 ◽

pp. 244-248 ◽

Cited By ~ 2

Author(s):

Donald L. Wolberg

Keyword(s):

Significant Contribution ◽

Organic Materials ◽

Sedimentary Rocks ◽

Iron Sulfides ◽

Decomposition Products ◽

Iron Minerals ◽

Pyrite Formation ◽

Organic Sediments ◽

Freshwater Environments

The minerals pyrite and marcasite (broadly termed pyritic minerals) are iron sulfides that are common if not ubiquitous in sedimentary rocks, especially in association with organic materials (Berner, 1970). In most marine sedimentary associations, pyrite and marcasite are associated with organic sediments rich in dissolved sulfate and iron minerals. Because of the rapid consumption of sulfate in freshwater environments, however, pyrite formation is more restricted in nonmarine sediments (Berner, 1983). The origin of the sulfur in nonmarine environments must lie within pre-existing rocks or volcanic detritus; a relatively small, but significant contribution may derive from plant and animal decomposition products.

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