Late Permian mafic rocks identified within the Doba basin of southern Chad and their relationship to the boundary of the Saharan Metacraton

2015 ◽  
Vol 152 (6) ◽  
pp. 1073-1084 ◽  
Author(s):  
J. GREGORY SHELLNUTT ◽  
TUNG-YI LEE ◽  
CHIH-CHENG YANG ◽  
SHIN-TAI HU ◽  
JONG-CHANG WU ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Central Africa ◽  
Late Permian ◽  
Southern Boundary ◽  
North Central ◽  
Nd Isotope ◽  
Mantle Sources ◽  
Basaltic Melt ◽  
Step Heating ◽  
Trace Elemental

AbstractThe Doba gabbro was collected from an exploration well through the Cretaceous Doba basin of southern Chad. The gabbro is composed mostly of plagioclase, clinopyroxene and Fe–Ti oxide minerals and displays cumulus mineral textures. Whole-rock40Ar–39Ar step-heating geochronology yielded a Late Permian plateau age of 257 ± 1 Ma. The major and trace elemental geochemistry shows that the gabbro is tholeiitic in composition and has trace element ratios (i.e. La/YbN> 7; Sm/YbPM> 3.4; Nb/Y > 1; Zr/Y > 5) indicative of a basaltic melt derived from a garnet-bearing mantle source. The moderately enriched Sr–Nd isotopes (i.e. ISr= 0.70495 to 0.70839; ɛNd(T)= −1.0 to −1.3) fall within the mantle array (i.e. OIB-like) and are similar to other Late Permian plutonic rocks of North-Central Africa (i.e. ISr= 0.7040 to 0.7070). The enriched isotopic composition of the Doba gabbro contrasts with the more depleted compositions of the spatially associated Neoproterozoic post-Pan-African within-plate granites. The contrasting Nd isotope composition between the older within-plate granites and the younger Doba gabbro indicates that different mantle sources produced the rocks and thus may mark the southern boundary of the Saharan Metacraton.

Petrogenesis and tectonic significance of the Late Permian–Middle Triassic calc-alkaline granites in the Balong region, eastern Kunlun Orogen, China

2012 ◽  
Vol 149 (5) ◽  
pp. 892-908 ◽  
Author(s):  
JIN-YANG ZHANG ◽  
CHANG-QIAN MA ◽  
FU-HAO XIONG ◽  
BIN LIU
Keyword(s):  
Middle Triassic ◽  
Isotope Composition ◽  
Quartz Diorite ◽  
Late Permian ◽  
Calc Alkaline ◽  
Nd Isotope ◽  
Crustal Rocks ◽  
Ocean Lithosphere ◽  
Granitoid Intrusions ◽  
Lower Crustal

AbstractNumerous calc-alkaline granitoid intrusions in the eastern Kunlun Orogen provide a valuable opportunity to constrain the evolution of the orogen. The age and genesis of these intrusions, however, remain poorly understood. The granitoid intrusions near the Balong region, eastern Kunlun Orogen, consist of granodiorite, diorite and syenogranite. The granodiorite contains crystallized segregations, abundant mafic microgranular enclaves (MMEs) and small quartz diorite stocks. In situ zircon U–Pb dating reveals that the granodiorites and quartz diorites were emplaced between 263 and 241 Ma, whereas the syenogranite was produced at c. 231 Ma. The granodiorite and quartz diorite have a calc-alkaline affinity and are metaluminous and Na-rich, with slightly enriched Sr–Nd isotope compositions. The granodiorite is characterized by fractionated REE patterns, whereas the quartz diorite displays a relatively flat REE pattern. The MMEs are consistent with the granodiorite in terms of incompatible elements and Sr–Nd isotope composition. Compared to the granodiorite and diorite, the syenogranite has higher SiO2, K, Rb, Th and Sr contents and a lower Rb/Sr ratio. The results presented here, when combined with regional geological data, indicate that the granodiorite and quartz diorite were derived from dehydration melting of mafic lower crustal rocks during the N-directed subduction of the Anyemaqen ocean lithosphere in Late Permian–Middle Triassic times, whereas the syenogranite was produced at a higher crustal level in a syn-collisional setting compared to the granodiorite.

Nd isotope composition of the Ediacaran and earliest Cambrian phosphorite nodules and Fe sulphide from the East European Platform

2020 ◽  
Vol 157 (12) ◽  
pp. 2081-2088
Author(s):  
Sergey B Felitsyn ◽  
Eugeny S. Bogomolov
Keyword(s):  
East European Platform ◽  
Isotope Composition ◽  
Water Reservoir ◽  
Secular Change ◽  
Early Cambrian ◽  
Iron Sulphide ◽  
Nd Isotope ◽  
East European ◽  
Moscow Syneclise ◽  
Nd Isotope Composition

AbstractAn enhanced concentration of phosphorus has been found at the stratigraphic level of the disappearance of Ediacaran taxa in two areas, the Cis-Dniester region and the Moscow syneclise, on the East European Platform (EEP). The isotope composition of neodymium was determined in Fe sulphide and phosphorite in the same beds. Measured εNd(t) values in diagenetic phosphate nodules are similar to those in iron sulphide from the same layer. During the Ediacaran − Early Cambrian, accumulation of radiogenic Nd in the epeiric basins on the EEP increased progressively from −17.9 and −19.4 in pyrite from the sequence bottom to −7.9 and −8.5 in the Early Cambrian pyrite of the central part of the EEP. The Ediacaran phosphate nodules show εNd(t) ranging from −12.9 to −15.0, while that in the Early Cambrian nodules is typically c. −9.0. These data indicate the secular change in Nd isotope composition of the water reservoir on the EEP from Ediacaran to Cambrian.

scholarly journals Ore and Geochemical Specialization and Substance Sources of the Ural and Timan Carbonatite Complexes (Russia): Insights from Trace Element, Rb–Sr, and Sm–Nd Isotope Data

Minerals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 711
Author(s):  
Irina Nedosekova ◽  
Nikolay Vladykin ◽  
Oksana Udoratina ◽  
Boris Belyatsky
Keyword(s):  
Trace Element ◽  
Mantle Source ◽  
Crustal Evolution ◽  
Trace Element Data ◽  
The Urals ◽  
Nd Isotope ◽  
Enriched Mantle ◽  
Depleted Mantle ◽  
Mantle Sources ◽  
Geochemical Specialization

The Ilmeno–Vishnevogorsk (IVC), Buldym, and Chetlassky carbonatite complexes are localized in the folded regions of the Urals and Timan. These complexes differ in geochemical signatures and ore specialization: Nb-deposits of pyrochlore carbonatites are associated with the IVC, while Nb–REE-deposits with the Buldym complex and REE-deposits of bastnäsite carbonatites with the Chetlassky complex. A comparative study of these carbonatite complexes has been conducted in order to establish the reasons for their ore specialization and their sources. The IVC is characterized by low 87Sr/86Sri (0.70336–0.70399) and εNd (+2 to +6), suggesting a single moderately depleted mantle source for rocks and pyrochlore mineralization. The Buldym complex has a higher 87Sr/86Sri (0.70440–0.70513) with negative εNd (−0.2 to −3), which corresponds to enriched mantle source EMI-type. The REE carbonatites of the Chetlassky сomplex show low 87Sr/86Sri (0.70336–0.70369) and a high εNd (+5–+6), which is close to the DM mantle source with ~5% marine sedimentary component. Based on Sr–Nd isotope signatures, major, and trace element data, we assume that the different ore specialization of Urals and Timan carbonatites may be caused not only by crustal evolution of alkaline-carbonatite magmas, but also by the heterogeneity of their mantle sources associated with different degrees of enrichment in recycled components.

Nd isotope composition of seep carbonates: Towards a new approach for constraining subseafloor fluid circulation at hydrocarbon seeps

2019 ◽  
Vol 503 ◽  
pp. 40-51 ◽  
Author(s):  
Michal Jakubowicz ◽  
Jolanta Dopieralska ◽  
Andrzej Kaim ◽  
Petr Skupien ◽  
Steffen Kiel ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Fluid Circulation ◽  
Nd Isotope ◽  
New Approach ◽  
Hydrocarbon Seeps ◽  
Nd Isotope Composition

scholarly journals Identification of processes that control the stable isotope composition of rainwater in the humid tropical West-Central Africa

2020 ◽  
Vol 584 ◽  
pp. 124650 ◽  
Author(s):  
B. Nlend ◽  
H. Celle-Jeanton ◽  
C. Risi ◽  
B. Pohl ◽  
F. Huneau ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Isotope Composition ◽  
Central Africa ◽  
Stable Isotope Composition ◽  
West Central

Megalosia, a new strophalosiid (Brachiopoda) genus from the Late Permian Nisal Member, Manang District, Nepal

1988 ◽  
Vol 62 (1) ◽  
pp. 41-45 ◽  
Author(s):  
J. B. Waterhouse
Keyword(s):  
Late Permian ◽  
North Central ◽  
Central Nepal ◽  
South Tibet

A new strophalosiid,Megalosia chuluensisn. gen. and sp., from the Nisal Member, Senja Formation, in the Manang district north of Mt. Annapurna, north-central Nepal, is of early Dorashamian or Changhsingian (Late Permian) age.Wyndhamia circularisChang, from slightly older faunas of south Tibet, might be congeneric.

The 2405 Ma and 2310 Ma Mafic Dyke Swarms in the Karelian Craton: Age, Chemical and Sr-Nd Isotope Composition, and Tectonic Setting

2016 ◽  
Vol 90 (s1) ◽  
pp. 123-123
Author(s):  
A.V. Stepanova ◽  
E.B. Salnikova ◽  
A.V. Samsonov ◽  
Yu.O. Larionova ◽  
S.V. Egorova ◽  
...  
Keyword(s):  
Isotope Composition ◽  
Tectonic Setting ◽  
Mafic Dyke ◽  
Karelian Craton ◽  
Nd Isotope ◽  
Dyke Swarms ◽  
Nd Isotope Composition
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