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Статті в журналах з теми "Neoproterozoic quartzites"
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ŽÁČKOVÁ, ELIŠKA, JIŘÍ KONOPÁSEK, JAN KOŠLER, and PETR JEŘÁBEK. "Detrital zircon populations in quartzites of the Krkonoše–Jizera Massif: implications for pre-collisional history of the Saxothuringian Domain in the Bohemian Massif." Geological Magazine 149, no. 3 (September 13, 2011): 443–58. http://dx.doi.org/10.1017/s0016756811000744.
Повний текст джерелаАнотація:
AbstractAge spectra of detrital zircons from metamorphosed quartzites of the Krkonoše–Jizera Massif in the northeastern part of the Saxothuringian Domain were obtained by U–Pb laser ablation inductively coupled plasma mass spectrometry dating. The zircon ages cluster in the intervals of 450–530 Ma and 550–670 Ma, and show individual data between 1.6 and 3.1 Ga. Zircons in the analysed samples are predominantly of Cambrian–Ordovician and Neoproterozoic age, and the marked peak at c. 525–500 Ma suggests a late Cambrian maximum age for the sedimentary protolith. Detritus of the quartzites probably originated from the erosion of Cambrian–Ordovician granitoids and their Neoproterozoic (meta)sedimentary or magmatic country rocks. The lack of Neoproterozoic (meta)sedimentary rocks in the central and eastern part of the Krkonoše–Jizera Massif suggests that the country rocks to voluminous Cambrian–Ordovician magmatic bodies were largely eroded during the formation of early Palaeozoic rift basins along the southeast passive margin of the Saxothuringian Domain. The detrital zircon age spectra confirm the previous interpretation that the exposed basement, dominated by Neoproterozoic to Cambrian–Ordovician granitoids, was overthrust during Devonian–Carboniferous subduction–collision processes by nappes composed of metamorphosed equivalents of the uppermost Cambrian–Devonian passive margin sedimentary formations. Only a negligible number of Mesoproterozoic ages, typically from the Grenvillian event, supports the interpretation that the Saxothuringian Neoproterozoic basement has an affinity to the West African Craton of the northwestern margin of Gondwana.
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Sharafeldin, Hani E., and Alexander A. Vercheba. "Perspective of gold-bearing deposits in the ferruginous-siliceous formations of Egypt and Kursk Magnetic Anomaly." RUDN Journal of Engineering Researches 20, no. 2 (December 15, 2019): 174–83. http://dx.doi.org/10.22363/2312-8143-2019-20-2-174-183.
Повний текст джерелаАнотація:
Banded ferruginous-siliceous formations (FSF) are confined to the Precambrian basement of the Arabian-Nubian Shield within the central part of the Eastern Desert of Egypt. Gold mineralization is spatially associated with banded ferruginous quartzite, representing one of the most ancient manifestations of gold ore. The Precambrian rocks are combined into deposits complex of the Neoproterozoic Pan-African megacycle of the territory development. Banded iron-silicate rocks occur in sedimentary-volcanogenic rocks that were formed in the subduction trough zones, and are represented by metamorphosed ferruginous quartzites, jaspilites and schists. FSF show tectonic dislocations, shear cracks, and fracture cracks made by gold-quartz-sulphide mineralization. Promising for the identification of gold-bearing mineralization in the rocks of the FSF can be iron-silicate deposits with the occurrence of epigenetic hydrothermal activity as a result of activation of the submarine volcanism of the tholeiitic type.
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A Nwos Prisca-Gaelle, Bien, Mounchili Ibrahim, Apouamoun Yiagnigni Roland, Etoundi Jean, Ndongue Constantin, and Meying Arsene. "THE CONTRIBUTION OF REMOTE SENSING AND AEROMAGNETISM TO GOLD PROSPECTING: THE CASE OF THE MEIGANGA ZONE, CAMEROON." International Journal of Advanced Research 9, no. 5 (May 31, 2021): 775–93. http://dx.doi.org/10.21474/ijar01/12903.
Повний текст джерелаАнотація:
In order to optimize gold prospecting in the Meiganga zone located in the Adamaoua region of Cameroon, aeromagnetic and remote sensing prospecting was carried out in the eastern and southern parts. The remote sensing approach on a Landsat 8 OLI/TIRS image highlighted areas of maximum gold concentration. Thus, ferric ion bearing minerals are located in the North-West, silicate minerals bearing ferrous ions are in the Centre while clay minerals are in the North-East and East. The principal component analysis revealed important structural information. The PCA Spatial Map (PC1, PC2, PC3) showed the plutonic formations composed of anatexis and anatexis granites, vegetation cover (at the date of image acquisition: February 22, 2019), areas of permanent water circulation or accumulation, and metamorphic and sedimentary formations namely gneisses, quartzites, schists and superficial clay formations. A Landsat SRTM (Shuttle Radar Topography Mission) image was also used to enhance the lineaments through the Sobel filter to highlight the geomorphological (cliffs, valleys, ...) and topographic (river network, ridge and drainage segment) structures. The aeromagnetic approach was also important. The study of the modified magnetic field (CM) showed 4 ranges: very high, high, medium and low. The Total Magnetic Anomalies (TMI) of the area are subdivided into 2 ranges large positive anomalies (221.1-103.0 nT) located in the lower part of NE-SW orientation, small positive anomalies (103.0-(-)89.7 nT) located in the upper part of NE-SW orientation. The reduced total magnetic anomaly at the equator shows a fairly similar distribution to the total magnetic anomaly with the large positive anomalies in almost the entire lower part. Superimposed on the geological map, Neoproterozoic pre- to syn-tectonic granitoids (C) are superimposed on the large positive anomalies and Neoproterozoic conglomerates, quartzites, sedimentary shales and volcanosedimentary rocks (A) and Neoproterozoic syn-tectonic granitoids (B) are superimposed on the large and small positive anomalies. The grid of the reduced residual equatorial anomaly (ARRE) confirms that the local geology is strongly magnetic (gneiss and quartzite). The filters of the derivatives allowed to establish a map of magnetic lineaments of major orientation N045° and minor orientation N130°. The horizontal gadient superimposed on the local maxima showed the presence of deep structures oriented NE-SW. The analytical signal superimposed on the local maxima highlights the metamorphic basement consisting of rocks with strong magnetism. The application of Euler deconvolution localizes the depth of the sources of linear anomalies.
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Barrote, Vitor Rodrigues, Carlos Alberto Rosiere, Vassily Khoury Rolim, João Orestes Schneider Santos, and Neal Jesse Mcnaughton. "The Proterozoic Guanhães banded iron formations, Southeastern border of the São Francisco Craton, Brazil: evidence of detrital contamination." Geologia USP. Série Científica 17, no. 2 (August 1, 2017): 303. http://dx.doi.org/10.11606/issn.2316-9095.v17-352.
Повний текст джерелаАнотація:
The Guanhães banded iron formation (BIF) bearing succession occurs as tectonic slices, juxtaposed to Archean TTG granite-gneissic basement rock, developed during the Neoproterozoic-Cambrian Brasiliano collage. The succession has a maximum depositional age of ~2.18 Ga, from detrital zircons in quartzite, and consists of quartzites, schists, BIFs, gneiss and amphibolite, all metamorphosed under amphibolite facies conditions. The Guanhães BIF shows HREE enrichment and consistent positive Eu anomaly (PAAS-normalized REE+Y). Two types of contamination were observed in the samples. The first is contamination by an exotic detrital component, which resulted in low Y/Ho (<30) and Pr/Yb (SN) ratios. Evidence of such contamination, combined with inferred stratigraphic stacking data, indicates that the Guanhães BIFs were deposited on a shallow marine environment. The second type of contamination resulted in higher Eu-anomalies, positive Ce-anomalies, and higher REE+Y concentrations, possibly due to the interaction between later magmatic fluids and the Guanhães BIF. A strong Cambrian event is recorded in zircon age data. The uncontaminated samples display REE+Y distribution similar to other Precambrian BIFs, particularly those from the Morro-Escuro Sequence and the Serra da Serpentina Group, without true Ce-anomalies and Y/Ho close to seawater values (45). Geochronological and geochemical data presented in this paper strongly suggest a correlation between the Guanhães supracrustal succession and the Serra da Serpentina and Serra de São José Groups.
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Dias, Tatiana Gonçalves, Fabrício de Andrade Caxito, Antônio Carlos Pedrosa-Soares, Ross Stevenson, Ivo Dussin, Luiz Carlos da Silva, Fernando Alkmim, and Márcio Pimentel. "Age, provenance and tectonic setting of the high-grade Jequitinhonha Complex, Araçuaí Orogen, eastern Brazil." Brazilian Journal of Geology 46, no. 2 (June 2016): 199–219. http://dx.doi.org/10.1590/2317-4889201620160012.
Повний текст джерелаАнотація:
ABSTRACT: The Jequitinhonha Complex of the northeastern Araçuaí orogen is an extensive sedimentary unit metamorphosed in the amphibolite-granulite facies transition around 580-545 Ma. The unit consists of Al-rich (kinzigitic) paragneisses with decametric intercalations of graphite gneisses and quartzites, and centimetric to metric lenses of calcsilicate rocks. A new detrital zircon U-Pb age spectrum is reported for a sample of quartzite, and whole-rock geochemical (major and trace elements, 9 samples) and Sm-Nd isotope data (10 samples) for Jequitinhonha Complex paragneiss. Together with published data these show that: (1) the geochemistry of paragneiss samples of the Jequitinhonha Complex are similar to those of passive margin sedimentary protoliths; (2) detrital zircon data yield U-Pb age populations between ca. 0.9 and 2.5 Ga; and (3) Sm-Nd TDM model ages range from 1.6 to 1.8 Ga and εNd(575 Ma) around -7.5. The data reveal a mixture of Cryogenian to Mesoproterozoic rift-related igneous rocks with the Palaeoproterozoic-Archaean basement rocks of the São Francisco-Congo palaeocontinent as the main source areas, and also support the correlation between the Jequitinhonha Complex and the passive margin units of the upper Macaúbas Group, constituting the precursor basin of the orogen. Our results, with the absence of ophiolites in the Jequitinhonha Complex, reinforce the interpretation that the São Francisco-Congo palaeocontinent was not divided to the north of the focused region, suggesting an ensialic termination of a gulf during the Neoproterozoic.
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Wang, Lu, Stephen T. Johnston, and Nengsong Chen. "New insights into the Precambrian tectonic evolution and continental affinity of the Qilian block: Evidence from geochronology and geochemistry of metasupracrustal rocks in the North Wulan terrane." GSA Bulletin 131, no. 9-10 (April 15, 2019): 1723–43. http://dx.doi.org/10.1130/b35059.1.
Повний текст джерелаАнотація:
Abstract The Qilian block, one of the Precambrian terranes in the Qinling-Qilian-Kunlun orogenic system, is a critical region for reconstruction of the overall architecture and tectonic evolution of NW China. This investigation of zircon U-Pb and Lu-Hf isotopes and whole-rock geochemistry of a metasupracrustal sequence in the North Wulan terrane provides new insights into the Qilian block. A Statherian–Calymmian unit (ca. 1.67–1.5 Ga), dominated by Al- and Si-rich gneisses, arkosites, quartzites, and amphibolites with minor calc-silicate rocks and marbles, is interpreted to have been deposited during continental rifting. Detrital zircons show two main age populations of 2685–2276 and 2098–1761 Ma with mostly negative εHf(t) values (–14.0 to +3.6). The sources are characterized by mixed felsic to intermediate igneous rocks as well as recycled components and are interpreted as being derived from the Tarim craton because of the age distribution of their detrital zircons. A Stenian–Tonian unit (ca. 1.1–0.9 Ga) consists mainly of felsic gneisses, quartzites, calc-silicate rocks, marbles, metavolcanic rocks, and amphibolites. The metasedimentary rocks yielded detrital zircon ages clustering at ca. 1.64, 1.43, 1.3–1.2, 1.1, and 0.94 Ga with predominantly positive εHf(t) values (–7.1 to +9.7). One metavolcanic rock has an age of ca. 1110 Ma and εHf(t) values of +6.5 to +9.1. The provenance is dominated by local syndepositional arc-related igneous rocks with older detritus possibly from Laurentia, again based on the age distribution of the detrital zircons. The Central Qilian and Hualong terranes show strong affinities with the North Wulan terrane and together constituted a single coherent Qilian block prior to their involvement in the Qilian–North Qaidam orogen. The Qilian block was probably once part of the Tarim craton and had a strong linkage to South Tarim, which drifted from North Tarim during the breakup of Columbia in the early Mesoproterozoic. We suggest that, from the late Mesoproterozoic to early Neoproterozoic, the South Tarim–Qilian formed an active continental margin located close to Laurentia during the assembly of Rodinia. The final collision occurred in the early Neoproterozoic with the formation of a significant continent that included the reunified Tarim-Qilian as well as Qaidam-Kunlun and Qinling terranes, Alxa block, Kyrgyz-Chinese Tianshan, and Yili block.
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Soulaimani, Abderrahmane, Mohamed Bouabdelli, and Alain Piqué. "The Upper Neoproterozoic-Lower Cambrian continental extension in the Anti-Atlas (Morocco)." Bulletin de la Société Géologique de France 174, no. 1 (January 1, 2003): 83–92. http://dx.doi.org/10.2113/174.1.83.
Повний текст джерелаАнотація:
Abstract Introduction. – In the Anti-Atlas, south of Morocco (fig. 1), the Precambrian terrains are usually divided into several “series” (fig. 2) : the Paleoproterozoic (PI) is an old crystalline basement, at least Eburnean ; the Neoproterozoic (PII) is constituted by metasedimentary rocks, quartzites and limestones, indicative of a shelf, in which volcano-sedimentary and volcanic flows are intercalated, laterally grading to an ophiolitic complex along the Sirwa-Bou Azzer axis. These PII rocks have been deformed in the course of the Panafrican orogeny ; above the underlying upper Proterozoic terrains and in major unconformity on the Panafrican structures, the Saghro group (PII3) and Ouarzazate group (PIII) series are volcanic and volcano-clastic sequences, often considered as late-Panafrican molasses. Above them, the Tata group (Adoudounian), constituted by marine carbonates and siltstones, represents the earliest Cambrian. Recent structural and sedimentological observations Recent observations have been realized through all the Anti-Atlas, of which the present note gives only examples that are the most significant and easily accessible. They show that the PII3 conglomerates were not everywhere deposited around Panafrican paleoreliefs ; they often contain large bodies of quartzites embedded within the conglomerates (fig. 3). Clearly, the PII3 is an olistostrome at the base of the PIII détrital and volcanic series, which were deposited at the base of active faults. The development of these reliefs took place several tens of millions of years after the end of the Panafrican paroxysm and therefore the PII3 and the PIII are post-Panafrican deposits, unrelated to the Panafrican orogeny. Study of synsedimentary structures (folds, faults, progressive unconformities : fig. 4 to 7) reveals the extensive character of this faulting event that extends even in basal Cambrian. Between the PII3 series and PIII an angular unconformity due to tilting can exist, but we did not find there plicative structures clearly related to the compressive late-Panafrican « B2 » phase sometimes described in the litterature. In the western Anti-Atlas, the extension is pure, with a NW-SE direction ; it is N-S in the central Anti-Atlas and it is transtensive according to N070°E faults, en échelon between sinistral N110°E trending faults in the central-eastern Anti-Atlas. In the detail, nevertheless, the synsedimentary structures suggest slidings from raised zones that correspond to the future inliers (fig. 7). Magmatic and metallogenic activity This extension accompanies various events : (1) a marine transgression, from west to east ; (2) the emplacement of extrusive magmas, first calco-alkaline then tholeiitic ; (3) an hydrothermal activity responsible for the concentration of Co, Au, Cu, etc. These concentrations were in the past attributed to various episodes, from the pre-Panafrican extension to the Hercynian compression. In fact, they result from the circulation of hydrothermal solutions that deposited, in the superficial levels of the crust, products extracted from the PIII magmas or the PII Proterozoic serpentines. The circulations took place in the old compressive structures (e.g. the Panafrican foliation) reopened during the extensive episode described above. Discussion and conclusion : the late Proterozoic-early Cambrian rifting The crustal extension that affected the Anti-Atlas started during the late Proterozoic, after the end of the main Panafrican deformation. Its tectonic significance is discussed with regard to the Panafrican orogeny : either a late Panafrican extension, bracketed between two compressive deformations and possibly related to a thinning of the orogenic crust, or a post-Panafrican extension, unrelated to compressive phases, described as a synrift event. In the Anti-Atlas, it developed through late Proterozoic and early Cambrian times. It aborted at the end of the early Cambrian. Evidences of a comparable extension are found in northern Morocco, western Europe and as far in the Middle East, i.e. all along the northern margin of the paleo-Gondwana.
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Alexeiev, D. V., A. K. Khudoley, and S. A. DuFrane. "Paleoproterozoic and Neoproterozoic Quartzites of the Kyrgyz North Tianshan: Age Determination according to the Results of Detrital Zircon Dating." Doklady Earth Sciences 491, no. 2 (April 2020): 191–94. http://dx.doi.org/10.1134/s1028334x20040017.
Повний текст джерела
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El Aouli, El Hassan, Dominique Gasquet, and Moha Ikenne. "Le magmatisme basique de la boutonniere d'Igherm (Anti-Atlas occidental, Maroc); un jalon des distensions neoproterozoiques sur la bordure nord du craton ouest-africain." Bulletin de la Société Géologique de France 172, no. 3 (May 1, 2001): 309–17. http://dx.doi.org/10.2113/172.3.309.
Повний текст джерелаАнотація:
Abstract In the Igherm inlier (western Anti-Atlas, Morocco) doleritic dyke swarms with various directions and gabbroic intrusive bodies were emplaced during Neoproterozoic times, cutting across either Eburnean micaschists and granites or Panafrican limestones and quartzites. All these rocks were deformed by the main Panafrican schistosity and covered by molassic and volcanic Upper Neoproterozoic series. The primary mineralogical assemblages (plagioclase, augite, olivine...) of the mafic rocks are nearly completely replaced by secondary assemblages (albite, actinolite, chlorite, epidote, calcite, quartz, leucoxene, magnetite, hematite...). However, three main groups have been recognized by the means of relative chronology and petrography. The group 1 is earlier, as shown by the intrusive character of the dykes of the other two groups into its gabbroic bodies. Using incompatible trace elements and rare earth elements it appears that this magmatism is truly heterogeneous and that the three groups have different magmatic affinities. The group 1 corresponds to tholeiitic dolerites and gabbros characterized by intersertal and ophitic textures and by high contents in Fe 2 O 3 (12.16 to 16.64%), TiO 2 (1.46 to 2.5%), Zr (90 to 174 ppm), Nb (7 to 13 ppm), Y (21.68 to 38.74 ppm) and V (264 to 419 ppm). The REE contents are low (Sigma REE = 49 to 137 ppm) and the REE patterns are flat [1.99<(La/Yb) N <4.56] showing a relative slight enrichment in LREE and no anomaly in Eu (0.89>Eu/Eu (super *) <1.11). These features as the TiO 2 vs FeO (super *) /MgO and V vs Ti/1000 diagrams are characteristic of anorogenic intraplate magmas. The group 2 corresponds to calc-alkaline dolerites and gabbros showing fine-grained intersertal textures and high contents of Al 2 O 3 (14.10 to 20.64%) and low contents of Fe 2 O 3 (8.35 to 12.91%), TiO 2 (0.68 to 1.41%), Zr (66 to 106 ppm), Nb (5 to 7 ppm), Y (16.41 to 20.75 ppm) and V (144 to 264 ppm). The REE contents vary from 67 to 155 ppm and the REE patterns are fractionated (2.78<(La/Yb) N <6.62) with a strong enrichment in LREE. The slight positive Eu anomaly (0.91<Eu/Eu (super *) <1.37) is related to the wealth of plagioclases frequently observed in these rocks. The TiO 2 contents of these rocks and their low FeO (super *) /MgO ratios give them a calc-alkaline affinity similar to that of calc-alkaline orogenic basalts related to an oceanic subduction. The group 3 corresponds to alkaline dolerites characterized by fine-grained intersertal textures with high contents of TiO 2 (3.85 to 3.97%), P 2 O 5 (0.66 to 0.77%), Nb (33 to 39 ppm), Zr (262 to 287 ppm), Y (39.6 to 47.7 ppm) and REE (Sigma REE = 205 to 218 ppm). The REE patterns are fractionated (7.77<La/Yb) N <6.65) without no Eu anomaly (0.99<Eu/Eu (super *) <1.02). The Ti/V and Y/Nb ratios (65.26 to 74.95 and 1.19 to 1.22, respectively) are those of alkaline rocks found in intraplate environments. The detailed petrographical, geochemical and field studies of the Igherm inlier show that the mafic magmatism is more complex than previously described. The mafic tholeiitic and alkaline magmatism occurring in the Igherm inlier is also present in the other inliers of the Moroccan Anti-Atlas during Neoproterozoic times. On the other hand the calc-alkaline Neoproterozoic mafic magmatism is very rare elsewhere in the Anti-Atlas except in the Siroua Massif and locally in the Bas Draa and Tagragra d'Akka inliers (western Anti-Atlas). The geodynamical environment of this mafic magmatism is linked to a strong extensional tectonic regime occurring at the northern border of the West African craton during Neoproterozoic times. This regime is related to the oceanic opening described in Central Anti-Atlas and to the emplacement of the ophiolites of Bou Azzer and Siroua or occurs immediately after the oceanic opening. The chemical heterogeneities observed in the three defined groups can be related to heterogeneities of mantellic sources and/or various partial melting ratios of the sub-continental mantle. We can assume that this major fissural magmatic event, not precisely dated, is equivalent to that observed in the other Neoproterozoic provinces in Hoggar, Cameroon, north America and Brazil.
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JASTRZĘBSKI, MIROSŁAW, ANDRZEJ ŻELAŹNIEWICZ, IZABELLA NOWAK, MENTOR MURTEZI, and ALEXANDER N. LARIONOV. "Protolith age and provenance of metasedimentary rocks in Variscan allochthon units: U–Pb SHRIMP zircon data from the Orlica–Śnieżnik Dome, West Sudetes." Geological Magazine 147, no. 3 (November 2, 2009): 416–33. http://dx.doi.org/10.1017/s0016756809990501.
Повний текст джерелаАнотація:
AbstractNew U–Pb sensitive high-mass resolution ion microprobe (SHRIMP) data from detrital zircons within the Orlica–Śnieżnik Dome provide new insights into the stratigraphic and palaeogeographic position of assumed relict Precambrian basement preserved in the Variscan collisional orogen of the West Sudetes, SW Poland. Hitherto, the Młynowiec Formation and the Stronie Formation within the Orlica–Śnieżnik Dome were assumed to represent two metavolcano-sedimentary successions of Proterozoic and early Palaeozoic age, respectively. However, when previous U–Pb data and mapping data from the Orlica–Śnieżnik Dome are combined with the new detrital zircon isotopic ages both from paragneisses within the Młynowiec Formation and from light-coloured quartzites and mica schists within the Stronie Formation, the result strongly suggests that the protoliths of these two formations actually form a continuous succession. This continuous succession is herein designated the Młynowiec–Stronie Group. The rocks of this group were deposited during middle Cambrian–early Ordovician times (c.520–470 Ma), presumably at the northern edge of West Gondwana after the 10–20 Ma period of tectonic quiescence that followed the terminal stage of the Cadomian collisions. Monotonous Młynowiec metagreywackes form the lower part of the succession, and the lithologically diverse schistose Stronie Formation forms its upper part. The change from greywacke (Młynowiec) to volcano-sedimentary (Stronie) facies coincided with the onset of rather short-lived volcanic activity which climaxed around 505–495 Ma and which supplied the volcanogenic components to the Stronie Formation. No ‘Cadomian unconformity’ has been observed in the region. Xenocrystic zircons from the Młynowiec–Stronie Group retain records of Archaean (3.0–2.3 Ga), Palaeoproterozoic (2.1–1.8 Ga) and Neoproterozoic to early Cambrian (660–530 Ma) zircon-forming events. These zircon ages, together with the lack of 1.7–1.2 Ga zircon ages, suggest that the source areas for the metasedimentary rocks may have been the West Africa craton, which therefore differs from the Amazonian affinity of the adjacent Brunovistulia Terrane. Nevertheless, two zircons,c.1.0 and 1.1 Ga old, respectively, indicate that the Młynowiec–Stronie Group sedimentary basin must have still been within the delivery reach of detritus ultimately derived from the Grenvillian-age belt(s). The detrital components of the supracrustal formations of the Orlica–Śnieżnik Dome were mainly derived from Neoproterozoic zircon-bearing crystalline rocks that were accreted to, and included in, the Cadomian basement in several intrusive pulses that culminated at 660–640 Ma, 620 Ma and 570–530 Ma.
Дисертації з теми "Neoproterozoic quartzites"
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Al-Kiyumi, M. "Constraining the age and provenance of the basal quartzites of the Centralian Superbasin." Thesis, 2018. http://hdl.handle.net/2440/130321.
Повний текст джерелаАнотація:
This item is only available electronically.The Heavitree Formation of the Amadeus Basin, central Australia, is thought to correlate with a number of similar formations in the Officer, Ngalia, Georgina and Murraba Basins that formed the Centralian Superbasin. The Jasper Gorge Formation of the Victoria Basin and Jamison Sandstone of the Beetaloo Sub-basin are also thought to be corollaries. These formations are all constrained to being younger than ca. 1.0 Ga by U-Pb detrital zircon studies. However, in all cases, this is suspected to considerably pre-date the timing of deposition. Here, we present new U-Pb and Hf data from seven samples of the Amadeus Basin Heavitree Formation to a) better constrain the age of the Heavitree Formation, b) investigate the spatial variation in provenance of the Heavitree Formation, and, c) compare it with other ‘Supersequence 1’ quartzites from the wider Centralian Superbasin.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2018
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Haddow, D. J. "Structural and geochronological constraints on the origin and evolution of rocks in the Ormiston Pound region of the Western MacDonnell Ranges, Northern Territory." Thesis, 2009. http://hdl.handle.net/2440/128940.
Повний текст джерелаАнотація:
This item is only available electronically.The Arunta Inlier preserves a complex structural history, subject to a series of igneous, metamorphic and deformational events from the Paleoproterozoic to the mid-Paleozoic. U-Pb detrital zircon ages from Paleoproterozoic and Neoproterozoic sediments at Ormiston Gorge coincide with the timing of various tectonic phases in the Arunta Inlier. First order interpretations suggest that the Northern Arunta Inlier was the source of the oldest zircons recorded at ~1820 Ma, coinciding with the timing of the Stafford Event. The Strangways Orogeny at ~1770 Ma and 1730 Ma is the earliest deformation preserved in the Central Arunta Inlier and is probably the source of zircons accumulated in these sediments. Zircons post-dating the Strangways Orogeny are likely sourced from the Southern Arunta Inlier, coinciding with the Argilke Tectonic Event at ~1680 Ma, the Chewings Orogeny at ~1600 Ma, the Anmatjira Uplift Phase at 1500-1400 Ma and the emplacement of the Teapot Granite Complex at ~1140 Ma. The Neoproterozoic Heavitree Range Quartzite sediments represent initial deposition in the Amadeus Basin, which forms the remnant of a once much larger intracratonic basin in central Australia known as the Centralian Superbasin. The Arunta Inlier was exhumed from beneath the Centralian Superbasin during the Devonian-Carboniferous Alice Springs Orogeny, forming a series of subbasins including the Amadeus, Ngalia and Georgina Basins. North-south crustal compression during this Orogeny reactivated a series of steep north-dipping Mesoproterozoic fault structures including the Redbank shear zone and the Ormiston thrust zone. The northern Amadeus Basin is characterised by coupled basement and cover deformation, producing a series of basement-rooted south-propagating thrusts, which penetrate the basal Heavitree Range Quartzite. Structural cross-sections constructed across the Ormiston region propose a series of splay thrusts within the Ormiston thrust zone, with the basement and Heavitree Quartzite heavily deformed. The conformably overlying Bittersprings Formation comprises salts and evaporates, interpreted as a detachment layer. 40Ar/39Ar muscovite dating of mylonitic shear zones at Ormiston Gorge have constrained ‘peak deformation’ conditions in the region to a minimum age of 350 ± 3 Ma. Mineral assemblages formed in the surrounding areas reflect greenschist to lower amphibolite facies metamorphism, with temperatures reaching at least 350°C.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, YEAR
Частини книг з теми "Neoproterozoic quartzites"
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Kuiper, Yvette D., Daniel P. Murray, Sonia Ellison, and James L. Crowley. "U-Pb detrital zircon analysis of sedimentary rocks of the southeastern New England Avalon terrane in the U.S. Appalachians: Evidence for a separate crustal block." In New Developments in the Appalachian-Caledonian- Variscan Orogen. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2554(05).
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ABSTRACT The Avalon terrane of southeastern New England is a composite terrane in which various crustal blocks may have different origins and/or tectonic histories. The northern part (west and north of Boston, Massachusetts) correlates well with Avalonian terranes in Newfoundland, Nova Scotia, and New Brunswick, Canada, based on rock types and ages, U-Pb detrital zircon signatures of metasedimentary rocks, and Sm-Nd isotope geochemistry data. In the south, fewer data exist, in part because of poorer rock exposure, and the origins and histories of the rocks are less well constrained. We conducted U-Pb laser ablation–inductively coupled plasma–mass spectrometry analysis on zircon from seven metasedimentary rock samples from multiple previously interpreted subterranes in order to constrain their origins. Two samples of Neoproterozoic Plainfield Formation quartzite from the previously interpreted Hope Valley subterrane in the southwestern part of the southeastern New England Avalon terrane and two from the Neoproterozoic Blackstone Group quartzite from the adjacent Esmond-Dedham subterrane to the east have Tonian youngest detrital zircon age populations. One sample of Cambrian North Attleboro Formation quartzite of the Esmond-Dedham subterrane yielded an Ediacaran youngest detrital zircon age population. Detrital zircon populations of all five samples include abundant Mesoproterozoic zircon and smaller Paleoproterozoic and Archean populations, and are similar to those of the northern part of the southeastern New England Avalon terrane and the Avalonian terranes in Canada. These are interpreted as having a Baltican/Amazonian affinity based primarily on published U-Pb and Lu-Hf detrital zircon data. Based on U-Pb detrital zircon data, there is no significant difference between the Hope Valley and Esmond-Dedham subterranes. Detrital zircon of two samples of the Price Neck and Newport Neck formations of the Neoproterozoic Newport Group in southern Rhode Island is characterized by large ca. 647–643 and ca. 745–733 Ma age populations and minor zircon up to ca. 3.1 Ga. This signature is most consistent with a northwest African affinity. The Newport Group may thus represent a subterrane, terrane, or other crustal block with a different origin and history than the southeastern New England Avalon terrane to the northwest. The boundary of this Newport Block may be restricted to the boundaries of the Newport Group, or it may extend as far north as Weymouth, Massachusetts, as far northwest as (but not including) the North Attleboro Formation quartzite and associated rocks in North Attleboro, Massachusetts, and as far west as Warwick, Rhode Island, where eastern exposures of the Blackstone Group quartzite exist. The Newport Block may have amalgamated with the Amazonian/Baltican part of the Avalon terrane prior to mid-Paleozoic amalgamation with Laurentia, or it may have arrived as a separate terrane after accretion of the Avalon terrane. Alternatively, it may have arrived during the formation of Pangea and been stranded after the breakup of Pangea, as has been proposed previously for rocks of the Georges Bank in offshore Massachusetts. If the latter is correct, then the boundary between the Newport Block and the southeastern New England Avalon terrane is the Pangean suture zone.
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Welch, J. L., B. Z. Foreman, D. Malone, and J. Craddock. "Provenance of early Paleogene strata in the Bighorn Basin (Wyoming, USA): Implications for Laramide tectonism and basin-scale stratigraphic patterns." In Tectonic Evolution of the Sevier-Laramide Hinterland, Thrust Belt, and Foreland, and Postorogenic Slab Rollback (180–20 Ma). Geological Society of America, 2022. http://dx.doi.org/10.1130/2022.2555(09).
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ABSTRACT The Bighorn Basin (Wyoming, USA) contains some of the most extensively exposed and studied nonmarine early Paleogene strata in the world. Over a century of research has produced a highly resolved record of early Paleogene terrestrial climatic and biotic change as well as extensive documentation of spatiotemporal variability in basin-scale stratigraphy. The basin also offers the opportunity to integrate these data with the uplift and erosional history of the adjacent Laramide ranges. Herein, we provide a comprehensive provenance analysis of the early Paleogene Fort Union and Willwood Formations in the Bighorn Basin from paleocurrent measurements (n > 550 measurements), sandstone compositions (n = 76 thin sections), and U-Pb detrital zircon geochronology (n = 2631 new and compiled age determinations) obtained from fluvial sand bodies distributed widely across the basin. Broadly, we observed data consistent with (1) erosion of Mesozoic strata from the Bighorn and Owl Creek Mountains and transport into the eastern and southern basin; (2) erosion of Paleozoic sedimentary cover and crystalline basement from the Beartooth Mountains eastward into the northern Bighorn Basin; (3) conglomeratic fluxes of sediment from the Teton Range or Sevier fold-and-thrust belt to the southwestern Bighorn Basin; and (4) potential sediment provision to the basin via the Absaroka Basin that was ultimately derived from more distal sources in the Tobacco Root Mountains and Madison Range. Similar to previous studies, we found evidence for a system of transverse rivers contributing water and sediment to an axial river system that drained north into southern Montana during both the Paleocene and Eocene. Within our paleodrainage and provenance reconstruction, the basin-scale patterns in stratigraphy within the Fort Union and Willwood Formations appear to have been largely driven by catchment size and the lithologies eroded from the associated highlands. Mudrock-dominated strata in the eastern and southeastern Bighorn Basin were caused by comparably smaller catchment areas and the finer-grained siliciclastic strata eroded from nearby ranges. The conglomeratic and sand-dominated strata of the southwestern area of the Bighorn Basin were caused by large, braided fluvial systems with catchments that extended into the Sevier thrust belt, where more resistant source lithologies, including Neoproterozoic quartzites, were eroded. The northernmost early Paleogene strata represent the coalescence of these fluvial systems as well as rivers and catchments that extended into southwestern Montana that contained more resistant, crystalline lithologies. These factors generated the thick, laterally extensive fluvial sand bodies common in that area of the basin. When combined with provenance patterns in adjacent Laramide basins, our data indicate asymmetric unroofing histories on either side of the Bighorn and Owl Creek Mountains. The Powder River Basin to the east of the Bighorn Mountains displays a clear Precambrian crystalline provenance, and the Wind River Basin to the south of the Owl Creek Mountains displays provenance similarities to Lower Paleozoic strata, in contrast to provenance in the Bighorn Basin, which indicates less substantial unroofing. We infer that the differing unroofing histories are due to the dominant vergence direction of the underlying basement reverse faults. Overall, this provenance pattern persisted until ca. 50 Ma, when more proximal igneous and volcaniclastic units associated with the Absaroka and Challis volcanics became major sediment sources and the Idaho River system became the dominant transport system in the area.
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White, Chris E., Sandra M. Barr, James L. Crowley, Deanne van Rooyen, and Trevor G. MacHattie. "U-Pb zircon ages and Sm-Nd isotopic data from the Cobequid Highlands, Nova Scotia, Canada: New contributions to understanding the Neoproterozoic geologic history of Avalonia." In New Developments in the Appalachian-Caledonian- Variscan Orogen. Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2554(07).
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ABSTRACT Forty-three new U-Pb zircon ages from metasedimentary and igneous rock units throughout the Cobequid Highlands of northern mainland Nova Scotia, Canada, provide new insights into the Neoproterozoic evolution of this long-enigmatic part of Avalonia in the northern Appalachian orogen. Contrasts in ages and rock types resulted in the identification of fault-bounded Neoproterozoic assemblages of units forming the Bass River, Jeffers, and Mount Ephraim blocks. In the Bass River block, quartzite, metawacke, and minor calc-silicate rocks and marble (Gamble Brook Formation) with a maximum depositional age of 945 ± 12 Ma are associated with subaqueous mafic volcanic rocks, siltstone, and ironstone (Folly River Formation) and intruded by 615–600 Ma calc-alkalic subduction-related dioritic to granitic rocks of the Bass River plutonic suite. The contrasting Jeffers block forms most of the Cobequid Highlands and consists mainly of intermediate to felsic volcanic, epiclastic, and minor plutonic rocks. The western and eastern areas of that block yielded ages mainly ca. 607–592 Ma for both volcanic and plutonic rocks, whereas the central area has ages of ca. 630–625 Ma from both volcanic and plutonic rocks and inheritance in overlying Devonian conglomerate. The Mount Ephraim block forms the eastern part of the highlands and includes possible ca. 800 Ma quartzofeldspathic, semipelitic and pelitic gneiss and schist of the Mount Thom Formation, ca. 752 Ma volcanic arc rocks of the Dalhousie Mountain Formation and related 752–730 Ma gabbroic/dioritic to granitic plutons of the Mount Ephraim plutonic suite and Six Mile Brook pluton, as well as ca. 631 Ma granitoid rocks of the Gunshot Brook pluton. The pre–750 Ma high-grade regional metamorphism and deformation and 752–730 Ma subduction-related magmatism recorded in the Mount Ephraim block were previously unrecognized in Avalonia. Evidence from zircon inheritance and Sm-Nd isotopic data in igneous units suggests linkages among these now-separate areas, and comparison with other parts of Avalonia in the northern Appalachian orogen suggests similarity to southeastern New England.
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Miller, Elizabeth L., Mark E. Raftrey, and Jens-Erik Lund Snee. "Downhill from Austin and Ely to Las Vegas: U-Pb detrital zircon suites from the Eocene–Oligocene Titus Canyon Formation and associated strata, Death Valley, California." In Tectonic Evolution of the Sevier-Laramide Hinterland, Thrust Belt, and Foreland, and Postorogenic Slab Rollback (180–20 Ma). Geological Society of America, 2022. http://dx.doi.org/10.1130/2021.2555(14).
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ABSTRACT In a reconnaissance investigation aimed at interrogating the changing topography and paleogeography of the western United States prior to Basin and Range faulting, a preliminary study made use of U-Pb ages of detrital zircon suites from 16 samples from the Eocene–Oligocene Titus Canyon Formation, its overlying units, and correlatives near Death Valley. The Titus Canyon Formation unconformably overlies Neoproterozoic to Devonian strata in the Funeral and Grapevine Mountains of California and Nevada. Samples were collected from (1) the type area in Titus Canyon, (2) the headwaters of Monarch Canyon, and (3) unnamed Cenozoic strata exposed in a klippe of the Boundary Canyon fault in the central Funeral Mountains. Red beds and conglomerates at the base of the Titus Canyon Formation at locations 1 and 2, which contain previously reported 38–37 Ma fossils, yielded mostly Sierran batholith–age detrital zircons (defined by Triassic, Jurassic, and Cretaceous peaks). Overlying channelized fluvial sandstones, conglomerates, and minor lacustrine shale, marl, and limestone record an abrupt change in source region around 38–36 Ma or slightly later, from more local, Sierran arc–derived sediment to extraregional sources to the north. Clasts of red radiolarian-bearing chert, dark radiolarian chert, and quartzite indicate sources in the region of the Golconda and Roberts Mountains allochthons of northern Nevada. Sandstones intercalated with conglomerate contain increasing proportions of Cenozoic zircon sourced from south-migrating, caldera-forming eruptions at the latitude of Austin and Ely in Nevada with maximum depositional ages (MDAs) ranging from 36 to 24 Ma at the top of the Titus Canyon Formation. Carbonate clasts and ash-rich horizons become more prevalent in the overlying conglomeratic Panuga Formation (which contains a previously dated 15.7 Ma ash-flow tuff). The base of the higher, ash-dominated Wahguyhe Formation yielded a MDA of 14.4 Ma. The central Funeral Mountains section exposes a different sequence of units that, based on new data, are correlative to the Titus Canyon, Panuga, and Wahguyhe Formations at locations 1 and 2. An ash-flow tuff above its (unexposed) base provided a MDA of 34 Ma, and the youngest sample yielded a MDA of 12.7 Ma. The striking differences between age-correlative sections, together with map-based evidence for channelization, indicate that the Titus Canyon Formation and overlying units likely represent fluvial channel, floodplain, and lacustrine deposits as sediments mostly bypassed the region, moving south toward the Paleogene shoreline in the Mojave Desert. The profound changes in source regions and sedimentary facies documented in the Titus Canyon Formation took place during ignimbrite flareup magmatism and a proposed eastward shift of the continental divide from the axis of the Cretaceous arc to a new divide in central Nevada in response to thermal uplift and addition of magma to the crust. This uplift initiated south-flowing fluvial systems that supplied sediments to the Titus Canyon Formation and higher units.