Contribution to the study of carbonatite complex of the Richat Dome (Mauritania)

2021 ◽  
Author(s):  
Eboubekrine Sedigh Maham ◽  
Houssa Ouali ◽  
Michel jébrak ◽  
Muhammed Ouabid
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Central Zone ◽  
Peripheral Zone ◽  
Geological Mapping ◽  
Critical Metals ◽  
Carbonatite Complex ◽  
Rare Type ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

<p>The Richat Dome is a huge circular, slightly elliptical depression (~ 40 km in diameter) in the Proterozoic to Cambro-Ordovician sedimentary series of the NE part of the Mauritanian Taoudeni basin. This structure consists of a central zone that corresponds to a complex of dolomitic limestones and sedimentary rocks of Neoproterozoic age, cut by breccia silica and felsic volcanic rocks. A peripheral zone comprising Neoproterozoic to Late Ordovician sandstones and pelites into which carbonatite veins and two gabbroic annular dykes are injected.</p><p>Generally, the carbonatites represent a relatively rare type of igneous rock composed mainly of primary carbonate minerals (calcite and/or dolomite > 50 vol % of the rock) associated with phosphate minerals, silicates, and oxides. They contain the highest concentrations of rare earth elements (REE) of all igneous rocks. The carbonatites are also the main source of REE especially the light REE (La, Ce, Pr and Nd) as well as some critical metals such as Nb and Ta.</p><p>The aim of this study is to present a preliminary work on the carbonatite dykes of the Richat Dome: (1) detailed geological mapping of the various dykes, (2) petrographic, (3) mineralogical and (4) geochemical characterizations. The results obtained will be cross-referenced with other strategic deposits around the world</p>

The Duck Pond and Boundary Cu–Zn deposits, Newfoundland: new insights into the ages of host rocks and the timing of VHMS mineralization

2010 ◽  
Vol 47 (12) ◽  
pp. 1481-1506 ◽  
Author(s):  
Vicki McNicoll ◽  
Gerry Squires ◽  
Andrew Kerr ◽  
Paul Moore
Keyword(s):  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Isotopic Data ◽  
Sulphide Ores ◽  
Intrusive Rocks ◽  
Felsic Volcanic ◽  
Host Rocks ◽  
Felsic Volcanic Rocks

The Duck Pond Cu–Zn–Pb–Ag–Au deposit in Newfoundland is hosted by volcanic rocks of the Cambrian Tally Pond group in the Victoria Lake supergroup. In conjunction with the nearby Boundary deposit, it contains 4.1 million tonnes of ore at 3.3% Cu, 5.7% Zn, 0.9% Pb, 59 g/t Ag, and 0.9 g/t Au. The deposits are hosted by altered felsic flows, tuffs, and volcaniclastic sedimentary rocks, and the sulphide ores formed in part by pervasive replacement of unconsolidated host rocks. U–Pb geochronological studies confirm a long-suspected correlation between the Duck Pond and Boundary deposits, which appear to be structurally displaced portions of a much larger mineralizing system developed at 509 ± 3 Ma. Altered aphyric flows in the immediate footwall of the Duck Pond deposit contained no zircon for dating, but footwall stringer-style and disseminated mineralization affects rocks as old as 514 ± 3 Ma at greater depths below the ore sequence. Unaltered mafic to felsic volcanic rocks that occur structurally above the orebodies were dated at 514 ± 2 Ma, and hypabyssal intrusive rocks that cut these were dated at 512 ± 2 Ma. Some felsic samples contain inherited (xenocrystic) zircons with ages of ca. 563 Ma. In conjunction with Sm–Nd isotopic data, these results suggest that the Tally Pond group was developed upon older continental or thickened arc crust, rather than in the ensimatic (oceanic) setting suggested by previous studies.

Revised stratigraphy of the Long Reach area, southern New Brunswick: evidence for major, northwestward-directed Acadian thrusting

1981 ◽  
Vol 18 (3) ◽  
pp. 646-656 ◽  
Author(s):  
S. R. McCutcheon
Keyword(s):  
New Brunswick ◽  
Lower Cambrian ◽  
Volcanic Rocks ◽  
Sedimentary Rocks ◽  
Thrust Fault ◽  
Northern Boundary ◽  
Granitoid Rocks ◽  
Felsic Volcanic ◽  
Stratigraphic Succession ◽  
Felsic Volcanic Rocks

In the Long Reach area of southern New Brunswick, a new stratigraphic succession has been delineated; it consists of Precambrian (?) volcanic rocks, Cambrian sedimentary, volcanic and hypabyssal rocks, Silurian sedimentary rocks, and Devonian plus Precambrian (?) heterogeneous, granitoid rocks. The northern boundary of this succession is postulated to be a northwestward-directed thrust fault of Acadian age. Other Acadian thrust faults are interpreted in the area and major reverse movement of the same age occurred along the Belleisle Fault.Mafic and felsic volcanic rocks that were previously thought to be either Precambrian or Silurian are demonstrably part of the Lower Cambrian section. Some of the granitoid rocks intrude Silurian strata and therefore cannot be basement to the Cambrian succession. Other granitoid rocks appear to be older and may be Precambrian in age.

Geochemistry and Isotope Composition of Paleoproterozoic Granites and Felsic Volcanics of the Elash Graben: Evidence of the Heterogeneity of the Early Precambrian Crust

2021 ◽  
Vol 62 (10) ◽  
pp. 1175-1187
Author(s):  
A.D. Nozhkin ◽  
O.M. Turkina ◽  
K.A. Savko
Keyword(s):  
Isotope Composition ◽  
Volcanic Rocks ◽  
Rare Metal ◽  
Temporal Association ◽  
Metal Deposit ◽  
Wide Range ◽  
Rare Metal Deposit ◽  
Geochronological Study ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

Abstract —The paper presents results of a petrogeochemical and isotope–geochronological study of the granite–leucogranite association of the Pavlov massif and felsic volcanics from the Elash graben (Biryusa block, southwest of the Siberian craton). A characteristic feature of the granite–leucogranites is their spatial and temporal association with vein aplites and pegmatites of the East Sayan rare-metal province. The U–Pb age of zircon from granites of the Pavlov massif (1852 ± 5 Ma) is close to the age of the pegmatites of the Vishnyakovskoe rare-metal deposit (1838 ± 3 Ma). The predominant biotite porphyritic granites and leucogranites of the Pavlov massif show variable alkali ratios (K2O/Na2O = 1.1–2.3) and ferroan (Fe*) index and a peraluminous composition; they are comparable with S-granites. The studied rhyolites of the Tagul River (SiO2 = 71–76%) show a low ferroan index, a high K2O/Na2O ratio (1.6–4.0), low (La/Yb)n values (4.3–10.5), and a clear Eu minimum (Eu/Eu* = 0.3–0.5); they are similar to highly fractionated I-granites. All coeval late Paleoproterozoic (1.88–1.85 Ga) granites and felsic volcanics of the Elash graben have distinct differences in composition, especially in the ferroan index and HREE contents, owing to variations in the source composition and melting conditions during their formation at postcollisions extension. The wide range of the isotope parameters of granites and felsic volcanic rocks (εNd from +2.0 to –3.7) and zircons (εHf from +3.0 to +0.8, granites of the Toporok massif) indicates the heterogeneity of the crustal basement of the Elash graben, which formed both in the Archean and in the Paleoproterozoic.

Post-collisional ca. 800 Ma A-type felsic volcanic rocks in the eastern Jiangnan orogen, South China

2020 ◽  
Vol 203 ◽  
pp. 104567
Author(s):  
Ji-Biao Zhang ◽  
Yan-Xue Liu ◽  
Xiao-Zhong Ding ◽  
Heng Zhang ◽  
Chuan-Heng Zhang
Keyword(s):  
South China ◽  
Volcanic Rocks ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks

scholarly journals Permian felsic volcanic rocks in the Pannonian Basin (Hungary): new petrographic, geochemical, and geochronological results

2019 ◽  
Vol 109 (1) ◽  
pp. 101-125 ◽  
Author(s):  
Máté Szemerédi ◽  
Réka Lukács ◽  
Andrea Varga ◽  
István Dunkl ◽  
Sándor Józsa ◽  
...  
Keyword(s):  
Pannonian Basin ◽  
Volcanic Rocks ◽  
Western Carpathians ◽  
Geochemical Data ◽  
Significant Similarity ◽  
Magmatic Rocks ◽  
Close Relationship ◽  
Felsic Volcanic ◽  
Felsic Volcanic Rocks ◽  
Extensional Setting

AbstractTwo distinct Permian volcanic epochs were revealed in the Pannonian Basin (eastern Central Europe) by U–Pb zircon geochronology: an older one (~ 281 Ma, Cisuralian) in the ALCAPA Mega-unit (Central Transdanubia, Hungary) and a younger volcanic episode (~ 267–260 Ma, Guadalupian) in the Tisza Mega-unit (Southern Transdanubia and the eastern Pannonian Basin, Hungary). The former is represented by dacitic subvolcanic rocks (dykes) and lavas, while the latter is dominantly by crystal-rich rhyolitic–rhyodacitic/dacitic ignimbrites and subordinate rhyodacitic/dacitic lavas. Whole-rock (major and trace element) geochemical data and zircon U–Pb ages suggest close relationship between the samples of Central Transdanubia and volcanic rocks of the Northern Veporic Unit (Western Carpathians, Slovakia), both being part of the ALCAPA Mega-unit. Such correlation was also revealed between the Permian felsic volcanic rocks of the Apuseni Mts (Romania) and the observed samples of Southern Transdanubia and the eastern Pannonian Basin that are parts of the Tisza Mega-unit. The older volcanic rocks (~ 281–265 Ma) could be linked to post-orogenic tectonic movements, however, the youngest samples (~ 260 Ma, eastern Pannonian Basin, Tisza Mega-unit) could be formed in the extensional setting succeeding the post-collisional environment. On the whole, the observed Permian magmatic rocks show significant similarity with those of the Western Carpathians.

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