Late Paleozoic Formation Research Articles

Scandium prospects in the Yakutian Diamond Province

Prerequisites and signs of scandium deposits in the ancient weathering crusts and in the oxidation zones in the Upper Paleozoic strata in West Yakutia are defined and substantiated. The prerequisites include: the presence of scandium sources—basic rocks, kimberlites and carbonatites; the spread of the ancient formation and ground oxidation which conditions migration of scandium; the presence of weathering crusts of the Carboniferous and Mesozoic ages, with alkaline and adsorptive barriers which concentrate scandium; good prospecting at depths up to 100 m. These prerequisites govern the relevance of the research as there is a possibility of scandium recovery from ore by in-situ leaching. Ancient oxidation in the strata and in the fractures in the gray-colored Сarboniferous–Permian formations and in the underlying weathering crusts is detected in the Ulakhan-Kurung-Yuryakh area of the Malaya Botuoba region in the Yakutian Diamond Province. Ancient epigenetic processes are confirmed by zonal limonitization and clarification of primary gray-colored rocks, and by redistribution of uranium, vanadium and gallium with the increased background contents of V and Sc. The X-ray fluorescence analyses performed in the Malaya Botuoba, Middle Markha and Ygyatta diamond-bearing regions revealed areal concentrations and promising scandium ore occurrences in the ancient weathering crusts and in the Late Paleozoic formations. In the weathering crust, in Suldyukar kimberlites, scandium concentrations exceed 100 ppm and feature high (up to 0,n%) contents of V, Co, Ni, La and Ce. The outstanding concentrations of scandium are found in the Triassic–Jurassic Dyakhtar clayey rocks representing a derivative weathering crust in the Nakyn diamondiferous field.

Role of the Taratash indenter in the Ural mountains building

The article presents the new data concerning the bounding zones of the Archean - Early Proterozoic Taratash block. It breaks the longitude structure of the Urals, squeezing all structural zones at a latitude of the town Miass. There were studied the meso- and microstructures of the boundary zones, anisotropy of magnetic susceptibility of faulted rocks and distribution of seismic waves velocities in to blastomylonites. We suggest that kinematic history of the Taratash block consists of two phases: 1) Middle Riphean exhumation of Taratash rocks in tension environ- ment; 2) Late Paleozoic formation of Indenter due regional shortening setting.

Early Paleozoic oceanic inliers and reconstruction of accretionary tectonics in the Middle Gobi region, Mongolia: Evidence from SHRIMP zircon U-Pb dating and geochemistry

The ophiolites that occur as inliers among the Late Paleozoic formations in the Middle Gobi area are crucial for understanding the tectonic evolution of South Mongolia. In this paper, we conducted detailed studies on the Namdain hundy ophiolite to provide some constraints on the Early Paleozoic evolution of the Middle Gobi region in Mongolia. The ophiolite mainly consists of ultramafic rocks (carbonatation), plagiogranite, metagabbro, basalt and chert. The metagabbro and plagiogranite from Namdain hundy ophiolite yielded SHRIMP zircon U-Pb ages of 528±7Ma and 519±5Ma, respectively. Though most of the volcanic rocks of this ophiolite show supra-subduction zone (SSZ) affinity, samples with OIB and N-MORB geochemical features were also identified, indicating genesis in a forearc setting. The granodiorite intruding into the Namdain hundy ophiolite yielded a SHRIMP zircon U-Pb age of 491±3Ma, which constrained the upper age limit of ophiolite emplacement. This granodiorite shows adakitic geochemical affinity, attesting to the existence of Cambrian paleo - subduction in South Mongolia. Based on the available data so far, we suggest the Middle Gobi area comprises of the Manlay accretion complex, the island arc and the Biluutiin ovoo back-arc basin. The spatial configuration of these three tectonic belts suggests that the polarity of the paleo-ocean subduction was from south to north in the Early Paleozoic, forming a trench-arc-basin system south of the Central Mongolia microcontinent.

Late Paleozoic final closure of the Paleo-Asian Ocean in the eastern part of the Xing-Meng Orogenic Belt: Constrains from Carboniferous–Permian (meta-) sedimentary strata and (meta-) igneous rocks

Zircon U–Pb dating and whole-rock geochemical data for Carboniferous–Permian (meta-) sedimentary sequences, igneous rocks, and Precambrian amphibolite in the eastern Xing-Meng Orogenic Belt (XMOB) were used to constrain the final stage evolution and the position of closure of the Paleo-Asian Ocean (PAO). Detrital zircons from Late Paleozoic strata range in age from Archean to Late Paleozoic, with major age groups at ~1.0–0.7Ga and ~0.5–0.25Ga in the northern part and at ~2.7–2.5Ga, ~2.1–1.8Ga, and ~0.5–0.25Ga in the southern part of the XMOB. Striking changes in zircon age distribution patterns indicate inputs to these strata were separated by the Paleo-Asian Ocean (PAO) in the Late Paleozoic. The PAO closed along the Solonker–Linxi suture. The Late Paleozoic formation ages (~346Ma, ~303Ma, and ~269Ma) of the igneous rocks with arc-like geochemical features south to the PAO, together with previously published data on the regional igneous rocks and ophiolites, indicate double-side subduction of the PAO in the Late Paleozoic.

北上山地宮守‐大迫地域における遠野接触変成帯の低度泥質変成岩類

The Miyamori-Ohazama district, central Kitakami Mountains, is occupied by the late Paleozoic formations composed chiefly of black shales and fossiliferous limestones. These Paleozoic rocks have been intruded by the Cretaceous Tono granodiorite pluton and undergone contact metamorphism.Three progressive metamorphic zones are recognized on the basis of mineral parageneses in metapelites. Zone I, most of which have been regarded as unmetamorphosed, is characterized by the assemblages of various phyllosilicates alined parallel to slaty cleavages. Zone II is characterized by the appearance of andalusite accompanied by muscovite, biotite, cordierite, garnet and occasionally gedrite. In zone III, sillimanite appears together with K-feldspar, biotite and cordierite. Microscopic observation and X-ray powder diffraction study revealed that metapelites in low-temperature part of zone I consist of the assemblage of paragonite, pyrophyllite, albite and calcite with invariable association of chlorite, muscovite, quartz and carbonaceous matter, suggesting metamorphic grade lower than the greenschist facies. In high-temperature part of zone I, however, porphyroblastic chloritoid, formed by the reaction with pyrophyllite and Fe-rich chlorite, appears in metapelites of lateritic chemical composition (Al2O3 23wt%, FeO/(FeO+MgO)>0.79). The degree of graphitization of carbonaceous matter in the metapelites progressively increases from zone I to zone III, showing a continuous thermal structure around the Tono granodiorite pluton. Judging from the graphitization-profile, all the assemblages mentioned above are considered to have been equilibrated under the thermal structure controlled by the Tono granodioritic intrusion.

Geology and Petroleum Possibilities in and Around Gulf of St. Lawrence

The Gulf of St. Lawrence is the largest embayment on the Atlantic Coast of North America between Florida and the Labrador Sea. Surface geology, geophysical data, and subsurface well control define four structural units and extend them from the land areas across the gulf. Beds having possibilities for oil and gas production are present in early Paleozoic formations overlying Precambrian basement in the Anticosti basin and western Newfoundland fault belt; in middle Paleozoic beds overlying Taconic basement in the Gaspe fold belt; and in late Paleozoic formations overlying Acadian basement in the Maritimes basin. The southward continuation of this Acadian basement is exposed on various uplands in Nova Scotia, and also underlies the Sydney, Fundy, and other basins, and extend beneath the great Mesozoic and Tertiary sedimentary wedge of the Scotian basin of the continental shelf. Production has not been obtained from wells drilled in the Anticosti basin--a relatively stable monocline. Many gas and oil shows have been found throughout Ordovician rocks; Silurian rocks may be productive in deeper parts of the basin. The Gaspe fold belt is thrust over the south edge of the Anticosti basin and is overlapped by the north edge of the Maritimes basin. Many seeps and shows of oil, but only insignificant recovery, have come from structurally complex Devonian beds in the likely part of the fold belt. In places, the Silurian beds may be productive, too. The allochthonous or klippe sequence of the western Newfoundland fault belt has been complexly thrust over the autochthonous sequence at the eastern margin of the Anticosti basin. Porosity and shows have been found in Ordovician formations in both structural sequences; very minor oil production has been obtained from shallow wells. The Maritimes basin, a large complex intermontane basin of Middle Devonian to Permian sedimentary rocks, has one small oil and gas field producing from Mississippian sandstones. The presence, at the southeast, of a thick sedimentary section, sizeable structures, porous sandstones and carbonate rocks, many shows and seeps, oil shales, and albertite encourage exploration, especially in the Mississippian Horton and Windsor Groups and the Pennsylvanian coarse-fluvial facies. Although estimated values for oil and gas in place in these four structural units may be quite large, the Paleozoic age of the sedimentary section, the low-grade metamorphism in some parts of the area, the generally poor porosity at depth, and the large area under water where operations are very expensive all reduce the commercial potential.

Age and Correlation of the Kobau Group, Mount Kobau, British Columbia

The Kobau Group, found in south-central British Columbia, consists of highly deformed, low-grade metamorphic rocks derived from a succession of sedimentary and basic volcanic rocks of pre-Cretaceous, likely post-Devonian age. Deformation began in Carboniferous times and recurred with decreasing intensity up to the Tertiary Period. Possible correlative successions are found surrounding Mount Kobau. These include possibly late Paleozoic formations west and northwest of Mount Kobau, the Carboniferous to Permian Anarchist Group found south of the 49th parallel and east of the Okanagan Valley, the pre-Upper Triassic, possibly Mississippian Chapperon Group west of Vernon, and parts of the Shuswap Metamorphic Complex east of the Okanagan Valley. Prior to deposition of the Kobau Group, part of the Shuswap Complex was subjected to deformation, presumably in mid-Paleozoic time.

Geology and Petroleum Possibilities in and Around Gulf of St. Lawrence: ABSTRACT

The Gulf of St. Lawrence is the largest embayment on the Atlantic Coast of North America between Florida and the Labrador Sea. In this region, surface geology provides the main control for defining four structural units which can be extended into or across the Gulf using published geophysical data and available well control. Prospective beds are found in early, middle, and late Paleozoic formations which in turn overlie Precambrian, Taconic, and Acadian basement. Acadian basement rocks underlying the Maritimes basin, Sydney basin, Fundy basin, etc., are exposed in parts of Nova Scotia, and continue south beneath the great Mesozoic and Tertiary sedimentary wedge of the Scotian basin. Production has not been obtained in the Anticosti basin, but most Ordovician formations have yielded gas and oil shows. The thick, gently dipping, early Paleozoic section is fairly prospective. Many seeps and shows, but insignificant oil recoveries, come from Devonian formations in the Gaspe fold belt; the Silurian also may be prospective in this structurally complex area. The Cambro-Ordovician section in both the klippe and autochthonous sequences in the western Newfoundland fault belt is prospective; seeps, shows, and very minor oil production have come from Ordovician porous zones. In the Maritimes basin, the presence of one small oil and gas field, many shows and seeps, oil shale and albertite, pronounced structures, and a thick sedimentary section have maintained interest and act vity in this large intermontane basin of Late Devonian to Permian sedimentary rocks. Carboniferous End_Page 2149------------------------------ sandstones and carbonate rocks provide the best prospects. Although estimated values for oil and gas in place in these four structural units may be quite large, the Paleozoic age of the sedimentary section, the low grade metamorphism in some parts of the area, the generally poor porosity at depth, and the large area under water where operations are very expensive all reduce considerably the commercial potential. End_of_Article - Last_Page 2150------------

Late Paleozoic formations of central Oregon

Fifteen miles southeast of Paulina, central Oregon, unaltered Carboniferous and Permian rocks yield much information regarding late Paleozoic history of this region. Three formations are described as follows: (1) the Coffee Creek (Lower Carboniferous) marine limestones and sandstones bearing Gigantella, Striatifera , and Dibunophyllum ; (2) the Spotted Ridge (Pennsylvanian) disconformably above the Coffee Creek, consisting of cherts, sandstones, heavy conglomerates, and mudstones, in part land-laid, yielding a well-preserved flora provisionally assigned to Pottsville; (3) Coyote Butte (Permian) limestones and sandstones with a large fusulinid, coral, and brachiopod fauna, resting unconformably on both the Spotted Ridge and Coffee Creek. The faunas indicate a closer relationship with northern California, Alaska, and the Old World than with other known areas in North America. Asiatic affinity of the Coyote Butte Permian fauna is particularly strong. The Paleozoic beds were folded after deposition of the Coyote Butte Permian and before accumulation of the Triassic conglomerates and sands. The Triassic and older strata suffered further compression later. Strikes of folds within the steeply dipping Paleozoics locally depart widely from trends in superjacent Triassic beds. Abundant coarse sandstone in all formations and heavy conglomerates in the Spotted Ridge Pennsylvanian bespeak high near-by terrain during much of late Paleozoic and conform to structural evidences of diastrophism.

Review of the Late Paleozoic Formations and Faunas, with Special Reference to the Ice-Age of Middle Permian Time

Introduction For more than fifty years geologists have been describing unmistakable late Paleozoic glacial deposits, and during the past thirty years this knowledge has become generally acceptable, but unfortunately there is as yet no agreement as to whether this ice-age took place in late Upper Carboniferous time or wholly in the Permian. Among the textbooks we find the leading French writers placing the time of this glaciation in the late Upper Carboniferous, whereas those of Germany always refer the ice-age to the Permian, some without doubt, like Frech (1901), who says it is “unmistakably of early Permian time,” and others, like Kayser (1923) and Schaffer (1924), who consider it as of probable Permian age. Most of the American textbooks are for a Permian reference. Scott (1907) says: “The earliest Permian in the southern hemisphere was a time of vast glaciation,” and Schuchert (1924) placed the ice-age well up in the . . .