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Mesozoic and Cenozoic Thermal History of the Western Reguibat Shield West African Craton) This is a repository copy of Mesozoic and Cenozoic thermal history of the Western Reguibat Shield West African Craton). White Rose Research Online URL for this paper: http://eprints.whiterose.ac.uk/124296/ Version: Accepted Version Article: Gouiza, M orcid.org/0000-0001-5438-2698, Bertotti, G and Andriessen, PAM (2018) Mesozoic and Cenozoic thermal history of the Western Reguibat Shield West African Craton). Terra Nova, 30 (2). pp. 135-145. ISSN 0954-4879 https://doi.org/10.1111/ter.12318 © 2017 John Wiley & Sons Ltd. This is the peer reviewed version of the following article: Gouiza M, Bertotti G, Andriessen PAM. Mesozoic and Cenozoic thermal history of the Western Reguibat Shield (West African Craton). Terra Nova. 2018;30:135–145. https://doi.org/10.1111/ter.12318, which has been published in final form at https://doi.org/10.1111/ter.12318. 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[email protected] https://eprints.whiterose.ac.uk/ Page 1 of 42 1 Μεσοζοιχ ανδ Χενοζοιχ τηερmαλ ηιστορψ οφ τηε ωεστερν Ρεγυιβατ Σηιελδ (Wεστ Αφριχαν Χρατον) 2 Μοηαmεδ Γουιζα (χορρεσπονδινγ αυτηορ) 3 Υνιϖερσιτψ οφ Λεεδσ 4 Σχηοολ οφ Εαρτη ανδ Ενϖιρονmεντ 5 Λεεδσ ΛΣ1 9ϑΤ, ΥΚ 6 +44 7985 78 20 73 7 m.γουιζα≅λεεδσ.αχ.υκ 8 ΟΡΧΙD: 0000−0001−5438−2698 9 10 Γιοϖαννι Βερτοττι 11 ΤΥ Dελφτ 12 Φαχυλτψ οφ Χιϖιλ Ενγινεερινγ ανδ Γεοσχιενχεσ 13 Στεϖινωεγ 1, 2628 ΧΝ Dελφτ, Νετηερλανδσ 14 15 Παυλ Α. Μ. Ανδριεσσεν 16 ςΥ Υνιϖερσιτψ Αmστερδαm 17 Φαχυλτψ οφ Εαρτη Σχιενχεσ 18 Dε Βοελελααν 1085, 1081 Ης Αmστερδαm, Νετηερλανδσ 19 20 Σηορτ τιτλε: Τηερmαλ ηιστορψ οφ τηε Wεστερν Ρεγυιβατ Σηιελδ Page 2 of 42 21 Αβστραχτ 22 Υσινγ λοω−τεmπερατυρε τηερmοχηρονολογψ ον απατιτε ανδ ζιρχον χρψσταλσ, ωε σηοω τηατ τηε 23 Wεστερν Ρεγυιβατ Σηιελδ, λοχατεδ ιν τηε νορτηερν παρτ οφ τηε Wεστ Αφριχαν Χρατον, εξπεριενχεδ 24 mαϕορ χοολινγ ανδ ηεατινγ εϖεντσ βετωεεν ϑυρασσιχ ανδ πρεσεντ τιmεσ. Τηε οβταινεδ απατιτε 25 φισσιον τραχκ αγεσ ρανγε βετωεεν 49 ανδ 102 Μα ωιτη mεαν τραχκ λενγτησ ϖαρψινγ βετωεεν 11.6 26 ανδ 13.3 D ) 27 αγεσ οφ 159 ανδ 118 Μα. Απατιτε (Υ−Τη)/Ηε υνχορρεχτεδ σινγλε−γραιν αγεσ ρανγε βετωεεν 76 ανδ 28 95 Μα. Τηερmαλ ινϖερσε mοδελλινγ ινδιχατεσ τηατ τηε Ρεγυιβατ Σηιελδ εξηυmεδ δυρινγ τηε Εαρλψ 29 Χρεταχεουσ, Λατε Χρεταχεουσ, ΠαλαεοχενεΕοχενε, ανδ Θυατερναρψ. Τηεσε εξηυmατιον εϖεντσ 30 ωερε χοεϖαλ ωιτη ρεγιοναλ τεχτονιχ ανδ γεοδψναmιχ εϖεντσ, ανδ ωερε προβαβλψ δριϖεν βψ α 31 χοmβινεδ εφφεχτ οφ πλατε τεχτονιχσ ανδ mαντλε δψναmιχσ. Page 3 of 42 32 Ιντροδυχτιον 33 Α συβσταντιαλ νυmβερ οφ στυδιεσ εξαmινινγ τηε τηερmαλ εϖολυτιον οφ δοmαινσ χοντιγυουσ το τηε 34 Μοροχχαν Ατλαντιχ mαργιν ρεϖεαλ τηε εξιστενχε οφ mαϕορ τηερmαλ εϖεντσ τηατ οχχυρρεδ αφτερ τηε 35 ινιτιατιον οφ τηε Εαρλψ−Μιδδλε ϑυρασσιχ δριφτινγ ιν τηε Χεντραλ Ατλαντιχ (ε.γ. Γηορβαλ ετ αλ., 2008; 36 Γηορβαλ, 2009; Σεβτι ετ αλ., 2009; Σαδδιθι ετ αλ., 2009; Ρυιζ ετ αλ., 2011; Ουκασσου ετ αλ., 2013; 37 Σεηρτ, 2014; Λεπρτρε ετ αλ., 2014; 2015). Τηεσε τηερmαλ εϖεντσ, χονστραινεδ βψ λοω−τεmπερατυρε 38 τηερmοχηρονολογψ (ΛΤΤ) (ι.ε. φισσιον τραχκ ανδ Υ−Τη/Ηε αναλψσεσ ον απατιτε ανδ ζιρχον χρψσταλσ), 39 αρε σψστεmατιχαλλψ αττριβυτεδ το κm−σχαλε ϖερτιχαλ mοϖεmεντσ οφ τηε χοντινενταλ χρυστ (ι.ε. βυριαλ 40 ανδ εξηυmατιον). Τηε συπποσεδλψ εξηυmεδ δοmαινσ αρε χηαραχτεριζεδ βψ εξποσεδ ολδ πρε− 41 Μεσοζοιχ βασεmεντ, ανδ τηε αβσενχε οφ σεδιmενταρψ χοϖερ πρεϖεντσ φροm υνδερστανδινγ ανδ 42 θυαντιφψινγ τηε τεχτονιχ προχεσσεσ τηατ mιγητ ηαϖε δριϖεν συχη εϖολυτιον (Τειξελλ ετ αλ., 2009; 43 Γουιζα, 2011). 44 Τηε Ρεγυιβατ σηιελδ ισ α δοmαιν τηατ εξπεριενχεδ ατ λεαστ ονε mαϕορ χοολινγ εϖεντ δυρινγ 45 Μεσοζοιχ τιmεσ (Λεπρτρε ετ αλ., 2014; 2015). Ιτ ισ λοχατεδ ιν τηε νορτηερν παρτ οφ τηε Wεστ Αφριχαν 46 Χρατον ανδ εξτενδσ οϖερ 1400 κm φροm τηε Αλγεριαν Σαηαρα δοmαιν ιν τηε εαστ το τηε Μοροχχαν 47 Ατλαντιχ mαργιν ιν τηε ωεστ (Φιγ. 1). Ιτ ισ αν ΕΝΕ−WΣW βασεmεντ ρισε ωηερε Αρχηεαν ανδ 48 Παλαεοπροτεροζοιχ ροχκσ αρε εξποσεδ (Φιγ. 1) (ςιλλενευϖε ανδ Χορνε, 1994; Σχηοφιελδ ετ αλ., 2012). 49 Ιτ ισ συρρουνδεδ βψ τηε ςαρισχαν Μαυριτανιδεσ Βελτ ιν τηε ΣW (χα. 300 Μα; Λχορχη ετ αλ., 1983; 50 Πυρδψ, 1987), τηε χοασταλ Ατλαντιχ βασιν οφ Ταρφαψα ιν τηε ΝW, τηε Παλαεοζοιχ Τινδουφ Βασιν ιν τηε 51 Ν−ΝΕ, ανδ τηε Νεοπροτεροζοιχ−Παλαεοζοιχ Ηανκ ανδ Αδραρ Βασινσ ιν τηε σουτη (ςιλλενευϖε, 2005). 52 Wηερεασ τηε φολδ βελτσ συρρουνδινγ τηε Wεστ Αφριχαν Χρατον (Φιγ. 1) ωερε φολδεδ ανδ 53 mεταmορπηοσεδ δυρινγ τηε Παν−Αφριχαν ανδ/ορ ςαρισχαν ορογενιεσ (ε.γ. Βλαχκ ετ αλ., 1979; 54 Γυιραυδ ετ αλ., 1987; Πυρδψ, 1987; Ηοεπφφνερ ετ αλ., 2005; Γασθυετ ετ αλ., 2008; Σουλαιmανι ανδ 55 Βυρκηαρδ, 2008), τηε χρατονιχ βασεmεντ εξποσεδ ιν τηε Ρεγυιβατ ανδ Μαν−Λεο σηιελδσ (Φιγ. 1) ισ Page 4 of 42 56 χονσιδερεδ το ηαϖε βεεν τεχτονιχαλλψ σταβλε σινχε 1700 Μα (ε.γ. ςιλλενευϖε ανδ Χορνε, 1994). 57 Ηοωεϖερ, ρεχεντλψ πυβλισηεδ απατιτε φισσιον τραχκ ανδ (Υ−Τη)/Ηε αναλψσεσ ον σαmπλεσ φροm τηε 58 χεντραλ ανδ ωεστερν Ρεγυιβατ προποσεδ τηατ mαϕορ ποστ−Τριασσιχ χοολινγ/εξηυmατιον εϖεντσ 59 αφφεχτεδ τηε σηιελδ (Λεπρτρε ετ αλ., 2015; 2017). 60 Ιν τηισ χοντριβυτιον, ωε πρεσεντ νεω ΛΤΤ δατα φροm 18 σαmπλεσ χολλεχτεδ φροm τηε ωεστερν 61 Ρεγυιβατ σηιελδ, ινχλυδινγ 17 απατιτε φισσιον τραχκ (ΑΦΤ), τωο ζιρχον φισσιον τραχκ (ΖΦΤ) ανδ σεϖεν 62 σινγλε−γραιν απατιτε (Υ−Τη)/Ηε (ΑΗε) αναλψσεσ. Wε χοmπαρε ουρ ρεσυλτσ το πρεϖιουσλψ πυβλισηεδ 63 δατα (Λεπρτρε ετ αλ., 2014; 2015) ανδ χηαλλενγε τηε mοδελ οφ α σταβλε χρατον βψ προποσινγ α 64 mοδιφιεδ mοδελ φορ τηε τεχτονιχ ανδ τηερmαλ εϖολυτιον οφ τηε σηιελδ. 65 Μετηοδσ ανδ αναλψτιχαλ ρεσυλτσ 66 Ινϖεστιγατιον οφ τηε τηερmαλ ηιστορψ οφ τηε ωεστερν Ρεγυιβατ βασεmεντ ροχκσ βψ ΑΦΤ, ΖΦΤ ανδ ΑΗε 67 αναλψσεσ αλλοωσ το χονστραιν τηε τιmε ωηεν τηε σαmπλεσ πασσεδ τηρουγη τηε τεmπερατυρε ωινδοω 68 χηαραχτεριστιχ οφ εαχη mετηοδ: 350220 °Χ φορ ΖΦΤ (Ψαmαδα ετ αλ., 2007), 11060 °Χ φορ ΑΦΤ 69 (Γρεεν ετ αλ., 1989), ανδ 7545 °Χ (Φαρλεψ, 2000). Φισσιον τραχκ δενσιτιεσ, ηοριζονταλ χονφινεδ τραχκ 70 λενγτησ ανδ Dπαρ (διαmετερ οφ ετχηεδ σποντανεουσ φισσιον τραχκσ, υσεδ ασ α προξψ φορ τηε χηεmιχαλ 71 χοmποσιτιον οφ απατιτε) ωερε mεασυρεδ ιν τηε απατιτε γραινσ ωιτη ιντερναλ συρφαχεσ παραλλελ το τηε 72 χ−αξισ (Dονελιχκ ετ αλ., 1999). 73 Τωο βατχηεσ οφ σαmπλεσ ωερε χολλεχτεδ φροm τηε εξποσεδ mαγmατιχ ροχκσ ιντρυδινγ τηε Αρχηεαν 74 βασεmεντ οφ τηε ωεστερν Ρεγυιβατ Σηιελδ (Φιγ. 2). Τηε φιρστ σετ οφ σαmπλεσ (ΑW) ωασ χολλεχτεδ αλονγ 75 α ΝW−ΣΕ τρανσεχτ, φροm τηε σψενιτε, δολεριτε, ανδ γρανιτοιδ ιντρυσιονσ ουτχροππινγ νεαρ Αωσαρδ 76 (Φιγ. 2). Τηε σεχονδ σετ οφ σαmπλεσ (ΜΣ) ωασ χολλεχτεδ αλονγ α ΝΝΕ−ΣΣW τρανσεχτ βετωεεν Αωσαρδ 77 ανδ Τιχηλα (Φιγ. 2) ωιτηιν τηε Πρεχαmβριαν γρανιτε ιντρυσιονσ. Απαρτ φροm τηε σψενιτε ιντρυσιονσ οφ 78 Αωσαρδ ωηιχη αρε δατεδ το βε χα. 2.46 Γα (Βεα ετ αλ., 2013), τηε οτηερ σαmπλεδ ιντρυσιονσ αρε νοτ Page 5 of 42 79 ψετ δατεδ βυτ αρε ασσυmεδ το βε Λατε Αρχηεαν το Εαρλψ Παλαεοπροτεροζοιχ (χα. 2.9−1.8 Γα; ε.γ. 80 Σχηοφιελδ ετ αλ., 2012; ϑεσσελλ ετ αλ., 2015). 81 Αγε δατα φροm τηισ στυδψ αρε πρεσεντεδ ιν Ταβλεσ 1 ανδ 2. ΑΦΤ αγεσ ρανγε βετωεεν 74 ανδ 102 Μα 82 φορ τηε ΑW σαmπλεσ, ανδ βετωεεν 49 ανδ 87 Μα φορ τηε ΜΣ σαmπλεσ (Ταβλε 1). Μεαν τραχκ λενγτησ 83 (ΜΤΛ) mεασυρεδ ιν απατιτε γραινσ ϖαρψ βετωεεν 11.8 ανδ 13.3 ιν τηε ΑW σαmπλεσ, ανδ βετωεεν 84 τηε ΜΣ σαmπλεσ (Ταβλε 1). Τηε mεασυρεδ Dπαρ ϖαλυεσ ρανγε φροm 1.69 το 3.08 85 ιν ΑW σαmπλεσ, ανδ φροm 1.72 το MS T 1). ΖΦΤ αναλψσισ ωασ περφορmεδ 86 ον σαmπλεσ ΜΣ−09 ανδ ΜΣ−12 ανδ ψιελδεδ αγεσ οφ 159 ανδ 118 Μα, ρεσπεχτιϖελψ (Ταβλε 1). 87 ΑΗε αναλψσισ, περφορmεδ ον τηε σαmπλεσ ΑW−03, ΑW−05, ανδ ΑW−06, ψιελδεδ υνχορρεχτεδ σινγλε− 88 γραιν αγεσ ρανγινγ βετωεεν 76 ανδ 95 Μα (Ταβλε 2). Τηε −εϕεχτιον χορρεχτεδ σινγλε−γραιν αγεσ 89 (Φαρλεψ ετ αλ., 1996) ϖαρψ βετωεεν 95 ανδ 119 Μα, ωιτη σινγλε γραιν αγεσ οφ τηε σαmε σαmπλε 90 οϖερλαππινγ ωιτηιν 1 υνχερταιντψ (Ταβλε 2). 91 Wε νοτε τηατ τηε ΑΗε υνχορρεχτεδ αγεσ αρε ειτηερ ψουνγερ τηαν τηε ΑΦΤ αγεσ οφ τηε σαmε σαmπλε 92 , ωηιλε τηε ΑΗε χορρεχτεδ αγεσ αρε σψστεmατιχαλλψ ολδερ τηαν τηε 93 ΑΦΤ αγεσ οφ τηε σαmε σαmπλε. Ραδιατιον δαmαγε ιν (ολδ) απατιτε χρψσταλσ χαν χαυσε νον−τηερmαλ 94 αννεαλινγ οφ φισσιονσ τραχκσ (ε.γ. Σδερλυνδ ετ αλ., 2005; Ηενδρικσ ανδ Ρεδφιελδ, 2005) ανδ χαν 95 ινχρεασε Ηε ρετεντιϖιτψ (ε.γ. Γρεεν ανδ Dυδδψ, 2006; Σηυστερ ετ αλ., 2006; Φλοωερσ, 2009), ωηιχη 96 mαψ ρεσυλτ ιν αν ινϖερτεδ ρελατιονσηιπ βετωεεν ΑΗε ανδ ΑΦΤ αγεσ (ι.ε. ΑΗε αγεσ ολδερ τηαν ΑΦΤ 97 αγεσ). Τηισ ισ υσυαλλψ ασσοχιατεδ ωιτη α ποσιτιϖε χορρελατιον βετωεεν εφφεχτιϖε υρανιυm 98 χονχεντρατιον (εΥ) ανδ ΑΗε αγεσ (Φιτζγεραλδ ετ αλ., 2006; Βροων ετ αλ., 2013), ωηιχη ισ νοτ τηε χασε 99 φορ τηε Ρεγυιβατ σαmπλεσ (Ταβλε 2).
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