The origin of Late Ediacaran post-collisional granites near the Chad Lineament, Saharan Metacraton, South-Central Chad

Shellnutt, J. Gregory; Yeh, Meng Wan; Lee, Tung Yi; Iizuka, Yoshiyuki; Pham, Ngoc Ha T.; Yang, Ching‐Chieh

doi:10.1016/j.lithos.2018.02.020

Cited by 29 publications

(24 citation statements)

References 81 publications

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“…Although lowermost Cambrian magmatic rocks have not been recognized yet in the CAfOB, with the exception of detrital alluvial zircons (Shellnutt et al, 2019), Late Ediacaran felsic and basic intrusions characterized by high-K calc-alkaline to shoshonitic affinity down to 545 Ma (Figs. 1, 10 and 11) are commonly found in Cameroon (Bouyo et al, 2015;Djouka et al, 2007;Kwekam et al, 2013;Tchouankoué et al, 2016), Chad (Isseini et al, 2012;Shellnutt et al, 2017Shellnutt et al, , 2018Shellnutt et al, , 2019 and Sudan (Kuster et al, 2008;Shang et al, 2010). They are interpreted as magmas emplaced during the post-collisional stage of the Pan-African orogeny (see Shellnutt et al, 2019).…”

Section: Age Of Igneous Events In Southern Ouaddaï and The Significanmentioning

confidence: 99%

“…11) during the post collisional period of the Pan-African orogeny (Figs 10 and 11) or the suprasubduction mantle previously enriched during the Cryogenian subduction(s). Late orogenic, post collisional magmatism is also well expressed in the CAfOB, from to 545 Ma Kwekwam et al, 2013;Isseini et al, 2012;Shellnutt et al, 2017Shellnutt et al, , 2018Shellnutt et al, , 2019Saha Fouotsa et al, 2019;Figs. 1, 10 and 11) (Figs.…”

Section: The Place Of Ouaddaï In the Pan-african Belts Of Western Gonmentioning

confidence: 99%

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Neoproterozoic magmatic evolution of the southern Ouaddaï Massif (Chad)

Djerossem¹,

Berger²,

Vanderhaeghe³

et al. 2020

BSGF - Earth Sci. Bull.

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This paper presents new petrological, geochemical, isotopic (Nd) and geochronological data on magmatic rocks from the southern Ouaddaï massif, located at the southern margin of the Saharan metacraton. This area is made of low-grade metasediments intruded by large felsic batholiths. The oldest but not dated magmatic activity is represented by amphibolites intercalated within silicilastic metasediments. They are metagabbros characterized by high Mg#, flat, LREE-depleted patterns, and superchondritic εNd, suggesting derivation of the parental basaltic magma from a depleted, probably asthenospheric mantle source. Subsequently, sediments of southern Ouaddaï were intruded by large composite peraluminous meta-granites. U-Pb zircon dating yield ages of 635 ± 3 Ma and 613 ± 8 Ma on a peraluminous biotite-leucogranite and a muscovite-leucogranite, respectively. These plutonic rocks contain recycled Archean and Paleoproterozoic zircon cores and are interpreted as the result of partial melting of metasediments. The last magmatic event is marked by the emplacement of granodiorite, biotite-granite and pyroxene-monzonite defining a metaluminous, high-K calc-alkaline to shoshonitic suite with a trace-element signature similar to calc-alkaline post-collisional series. A biotite-granite of this suite contains zircon grains that yield an age of 540 ± 5 Ma with inherited cores crystallized around 1050 Ma. These intermediate to felsic rocks are interpreted to derive from the differentiation of basic to intermediate magmas generated in an enriched mantle that has been affected by partial melting at the end of the Pan-African orogeny. The Mesoproterozoic zircon cores might reflect the presence of a previously unrecognized Mesoproterozoic basement near southern Ouaddaï. These new data show that the southern Ouaddaï is dominated by Ediacarian to lowermost Cambrian magmatic suites intrusive in a siliciclastic metasedimentary sequence. Amphibolites probably record Rodinia breakup or the development of a back-arc basin before 635 Ma. Early Ediacarian (635-613 Ma) deformed anatectic leucogranites correlate to contemporaneous migmatites and leucogranites in Cameroon and Sudan emplaced during the main Pan-African tectonic-metamorphic event leading to pervasive melting in the deep crust. The end of the Pan-African orogeny is marked, as in the whole Central Africa Orogenic belt, by a high-K magmatic event corresponding to the post-collisional Pan-African stage.

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Section: Age Of Igneous Events In Southern Ouaddaï and The Significanmentioning

confidence: 99%

Section: The Place Of Ouaddaï In the Pan-african Belts Of Western Gonmentioning

confidence: 99%

Neoproterozoic magmatic evolution of the southern Ouaddaï Massif (Chad)

Djerossem¹,

Berger²,

Vanderhaeghe³

et al. 2020

BSGF - Earth Sci. Bull.

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“…Little is known about the Guéra massif which is primarily composed of granitoids (with minor gabbroic bodies) and metamorphic rocks (Isseini et al, 2013;Kusnir and Moutaye, 1997). A recent U-Pb dating survey of the igneous rocks revealed emplacement ages ranging between 595 and 545 Ma (Shellnutt et al, 2020(Shellnutt et al, , 2019(Shellnutt et al, , 2018(Shellnutt et al, , 2017 while a Neoproterozoic age is inferred for the metamorphic lithologies.…”

Section: Geological Settingmentioning

confidence: 99%

“…11a). A-type volcanic-plutonic associations with emplacement ages ranging between 568 ± 6 and 545 ± 6 Ma have been described in the Guéra massif and two granitic inliers located 100 km to the NW (Pham et al, 2017;Shellnutt et al, 2018Shellnutt et al, , 2017. In the WCD-MK, the A2-type Zabili granite pluton was emplaced at 567 ± 10 Ma (Isseini et al, 2012) even though recent geochronological investigations performed on a hydrothermally altered facies (albitite) suggest it might be older (Vanderhaeghe et al, in press).…”

Section: Regional Correlations and Tectonic Settingmentioning

confidence: 99%

Crystalline inliers near Lake Iro (SE Chad): Post-collisional Ediacaran A2-type granitic magmatism at the southern margin of the Saharan Metacraton

Couzinié

Ménot

Doumnang

et al. 2020

Journal of African Earth Sciences

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The structure and evolution of the continental crust in the southern part of the Saharan Metacraton (central Africa) is poorly known due to extensive laterite and sediment cover as well as geographic isolation. We report on a series of five crystalline inliers newly discovered near Lake Iro (south-eastern Chad) that offered the opportunity to amphibole assemblage from a porphyritic granite melt and (ii) both granite types yield zircon U-Pb emplacement ages consistent within a 575.3 ± 5.6 to 581.3 ± 3.8 Ma time frame. The Lake Iro granites thus represent the oldest of a series of post-collisional igneous associations exposed in southern Chad and nearby countries which, collectively, show that the amalgamation of the constituent blocks of the southern Saharan Metacraton is older than 580 Ma.

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“…Isotope model ages and U-Pb geochronology of basement rocks vary from ∼3100 to 500 Ma suggesting there is an Archean ancestry within the Saharan Metacraton (Abdelsalam et al, 2002). Nevertheless, the principal magmatic phases of the Saharan Metacraton occurred from ∼750 to 550 Ma (Abdelsalam et al, 2002;Suayah et al, 2006;Shellnutt et al, 2017Shellnutt et al, , 2018.…”

Section: Introductionmentioning

confidence: 99%

An Assessment of the Magmatic Conditions of Late Neoproterozoic Collisional and Post-collisional Granites From the Guéra Massif, South-Central Chad

Pham

Shellnutt²,

Yeh

et al. 2020

Front. Earth Sci.

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The Guéra Massif, in South-Central Chad hosts granitic rocks that were emplaced during distinct intervals (595-590; ∼570; ∼560 Ma) of the Late Ediacaran Central African Orogenic Belt. To the northwest of the Guéra Massif, younger post-collisional granites (554-545 Ma) are found near Lake Fitri. The older (≥590 Ma) rocks have geochemical characteristics of collisional granites whereas the younger (≤570 Ma) rocks are similar to post-collisional granites. Biotite and amphibole were analyzed to constrain the magmatic conditions of the granites. The biotite from the collisional granites tends to have higher Al and Ti and lower Fe# (Fe# average ≈ 0.67) than the post-collisional granites (Fe# average ≈ 0.88). The average crystallization temperatures range from 696 ± 37 to 612 ± 8 • C, with the average pressure of crystallization from 0.25 ± 0.09 to 0.13 ± 0.02 GPa, and redox conditions between the nickel-nickel oxide (NNO) and quartz-fayalite-magnetite (QFM) buffers. The biotite crystallization temperatures of the post-collisional rocks are generally lower than the collisional rocks (570 Ma = 630 ± 26 to 619 ± 30 • C, 560 Ma = 626 ± 20 to 607 ± 4 • C, 550 Ma = 639 ± 18 to 612 ± 13 • C), but the crystallization pressures are similar (0.27 ± 0.05 to 0.14 ± 0.04 GPa). The redox conditions transition from the QFM buffer to the wüstite-magnetite (WM) buffer. In contrast, the biotite from the Lake Fitri post-collisional granites crystallized at higher pressure (0.39 ± 0.08 to 0.35 ± 0.03 GPa) but similar redox conditions. The amphiboles in the younger (∼590 Ma) collisional granites and the post-collisional granites yielded crystallization pressure estimates that are generally higher (∼0.6 to 0.1 GPa) than the biotite estimates but there is overlap. The difference in pressure may be due to the timing of crystallization and/or crystal redistribution. Overall, there appears to be a secular change from high to low temperature and pressure whereas the redox conditions appear to be spatially related. The biotite crystallization pressure of the Lake Fitri granites suggests they were likely emplaced into a different domain/terrane of the Saharan Metacraton than the Guéra Massif.

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The origin of Late Ediacaran post-collisional granites near the Chad Lineament, Saharan Metacraton, South-Central Chad

Cited by 29 publications

References 81 publications

Neoproterozoic magmatic evolution of the southern Ouaddaï Massif (Chad)

Neoproterozoic magmatic evolution of the southern Ouaddaï Massif (Chad)

Crystalline inliers near Lake Iro (SE Chad): Post-collisional Ediacaran A2-type granitic magmatism at the southern margin of the Saharan Metacraton

An Assessment of the Magmatic Conditions of Late Neoproterozoic Collisional and Post-collisional Granites From the Guéra Massif, South-Central Chad

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