SHRIMP U–Pb zircon geochronology of the granitoids of the Imiter Inlier: Constraints on the Pan-African events in the Saghro massif, Anti-Atlas (Morocco)

Accepted Manuscript SHRIMP U–Pb zircon geochronology of the granitoids of the Imiter Inlier: Constraints on the Pan-African events in the Saghro massif, Anti-Atlas (Morocco)

Bouchra Baidada, Moha Ikenne, Pierre Barbey, Abderrahmane Soulaimani, Brian Cousens, Faouziya Haissen, Said Ilmen, Abdelkhalek Alansari PII:

S1464-343X(18)30315-7

DOI:

10.1016/j.jafrearsci.2018.10.008

Reference:

AES 3343

To appear in:

Journal of African Earth Sciences

Received Date:

30 January 2018

Accepted Date:

19 October 2018

Please cite this article as: Bouchra Baidada, Moha Ikenne, Pierre Barbey, Abderrahmane Soulaimani, Brian Cousens, Faouziya Haissen, Said Ilmen, Abdelkhalek Alansari, SHRIMP U–Pb zircon geochronology of the granitoids of the Imiter Inlier: Constraints on the Pan-African events in the Saghro massif, Anti-Atlas (Morocco), Journal of African Earth Sciences (2018), doi: 10.1016/j. jafrearsci.2018.10.008

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SHRIMP U–Pb zircon geochronology of the granitoids of the Imiter Inlier: Constraints

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on the Pan-African events in the Saghro massif, Anti-Atlas (Morocco)

3 4 5

Bouchra BAIDADA a *, Moha IKENNE b, Pierre BARBEY c, Abderrahmane SOULAIMANI a,

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Brian COUSENS d, Faouziya HAISSEN e, Said ILMEN f, Abdelkhalek ALANSARI a,

7 8 9

a

Department of Geology, Faculty of Sciences-Semlalia, Cadi Ayyad University, Prince

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Moulay Abdellah Boulevard, P.O. Box 2390, 40 000 Marrakech, Morocco

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b

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P.O. Box 28/S, 80 000 Agadir, Morocco

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c Université

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d

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1125 Colonel By Drive Ottawa, Ontario, K1S5B6, Canada

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e

LGCA, Département de Géologie, Université Hassan II de Casablanca, Morocco

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f

Managem Group, Twin Center, 20100Casablanca, Morocco

LAGAGE Laboratory, Department of Geology, Faculty of Sciences, Ibn Zohr University, de Lorraine, CNRS, CRPG, F-54000 Nancy, France

Ottawa-Carleton Geoscience Centre, Department of Earth Sciences Carleton University,

18 19 20 21 22 23 24 25 26 27 28 29 30 31

* Corresponding author : Department of Geology, Faculty of Sciences-Semlalia, Cadi Ayyad

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University, Prince Moulay Abdellah Boulevard, P.O. Box 2390, 40 000 Marrakech, Morocco,

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[email protected]

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Abstract

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This study presents new U–Pb zircon ages for three granitoid bodies in the Imiter inlier at the

3

eastern part of the Moroccan Anti-Atlas chain, which is located in the northwestern edge of

4

the West African Craton (WAC). Analyzes of zircon grains yield the following ages: 538 ± 6

5

and 575 ± 10 Ma for the Igoudrane massif, 567 ± 6 Ma for the nearby Bou Teglimt

6

granodiorite, and 582 ± 6 Ma for the Bou Fliou granite. These new data reveal that the

7

Igoudrane massif is younger than previously thought (677 Ma), and that all the granitoids in

8

the Imiter area are Ediacaran in age and are related to the Ouarzazate Group. Sm-Nd isotopic

9

data yield negative εNd(t) values (-4.5 to -0.2) and TDM model ages of 1.04 to 1.82 Ga. These

10

data indicate the presence of an inherited Paleoproterozoic to Archaean component in some

11

zircon grains and show that generation of the parent magmas involved a Neoproterozoic

12

juvenile contribution and recycling of an older crustal component.

13

These new data allow reinterpreting the geochemical and isotopic data of the granitoids, and

14

revisiting the structural significance to the Igoudrane massif, which was assumed until now to

15

be coeval with the major Pan-African event of the Central Anti-Atlas. They also bring

16

significant constraints to discuss the context and age of deposition of the Saghro Group,

17

which is still a matter of debate. All these data provide evidence of an emplacement of the

18

Imiter granitoids in a subduction complex, which affected all of the Anti-Atlas chain during the

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Late Proterozoic time.

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Keywords: Imiter; Anti-Atlas; Morocco; Granitoids; Zircon U–Pb geochronology; Ediacaran;

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Pan-African

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1. Introduction

3 4

At the northwestern border of the West African Craton, Precambrian rocks of the Anti-

5

Atlas chain record a polycyclic, Eburnean and Pan-African, evolution (Leblanc, 1975;

6

Hassenforder, 1987; Saquaque et al, 1989; Gasquet et al., 2004, 2008; Thomas et al., 2002,

7

2004; Ennih and Liégeois, 2008). During the last twenty years, numerous studies have

8

described the lithostratigraphy of the Precambrian rocks in the Anti-Atlas Mountains (Thomas

9

et al., 2004 ; Gasquet et al., 2005), and various geodynamic models (Ennih et Liégeois, 2001;

10

Gasquet et al., 2005; Benziane, 2007; Walsh et al., 2012) have been proposed for the Pan-

11

African orogeny. These geodynamic reconstructions suppose that the southwestern and the

12

northeastern domains of the Anti-Atlas, separated by ophiolitic complexes along the Anti-

13

Atlas Major fault, experienced a common geological history until the end of the Ediacaran.

14

The basement of the Anti-Atlas, unconformably overlain by Proterozoic rocks of the Anti-

15

Atlas, is sub-divided into two lithostratigraphic assemblages: the Anti-Atlas and Ouarzazate

16

Supergroups. The Lower Anti-Atlas Supergroup consists of Tonian quartzite and limestone

17

series of the Tachdamt–Bleïda platform, and of the Cryogenian ophiolitic complex of the

18

Bou-Azzer–Siroua inliers intruded by various Pan-African granitoids (Clauer, 1974; Leblanc,

19

1975; Saquaque et al., 1992; Bouougri et al., 1994; Mouttaqi, 1997). The Ediacaran

20

Ouarzazate Supergroup comprises the Saghro–Bou Salda and the Ouarzazate Groups. The

21

Saghro–Bou Salda Group and the equivalent Tiddiline and Anezi series correspond to the

22

latest deposits of the Pan-African mountain building. In the Imiter inlier, exposed in the

23

easternmost part of the Anti-Atlas chain (Fig. 1), the Saghro Group consists of a thick

24

volcano-sedimentary series (Thomas et al., 2004; Michard al., 2017) deformed by NNE-

25

trending, mostly upright folds with axial-planar slaty cleavage developed under low-grade

26

metamorphic conditions. In the Siroua and Saghro inliers, the older (620–610 Ma) rocks of

27

the Saghro Group (Liégeois et al., 2006; Abati et al., 2010, 2012) were folded at ca. 610–580

28

Ma at the onset of the WAC Cadomian orogenic events (Hefferan et al., 2014; Michard et al.,

29

2017). The deformed Saghro Group rocks were intruded by numerous plutonic bodies

30

previously considered to be Cryogenian (e.g., Igoudrane massif at 677 Ma; Schiavo et al.,

31

2007) to Ediacaran (e.g., Bou Teglimt, Taouzzakt; Mrini, 1993; De Wall et al., 2001;

32

Cheilletz et al., 2002; Massironi et al., 2007; Errami et al., 2009).

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The age and geodynamic significance of the Saghro Group is still a subject of debate

2

(Michard et al., 2017; and references therein). The supposed Paleoproterozoic age of the

3

Imiter orthogneiss in the Boumalne inlier (Hindermeyer, 1953; Choubert et al., 1974) is now

4

considered Middle Proterozoic (Dal Piaz et al., 2007). The Saghro Group, assumed to be

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Cryogenian ocean-basin filling series older than 610 Ma (Thomas et al., 2004), was folded and

6

metamorphosed to the lower greenschist facies during the Pan-African major event (ca. 680–

7

600 Ma; Leblanc and Lancelot 1980; Fekkak et al., 2000; Thomas et al., 2004). The

8

occurrence of assumed Cryogenian intrusions crosscutting the Boumalne and Imiter inlier

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metasediments has been considered as an argument against an age younger than 630 Ma for

10

the Saghro Group (Dal Piaz et al., 2007; Schiavo et al., 2007). However, recent

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geochronological determinations from detrital zircons gave younger ages (630-610 Ma) for

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this Group (Liégeois et al., 2006; Abati et al., 2010, 2012). As a consequence, the plutonic

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ages available in the Imiter inlier, especially those of intrusions supposed to be Cryogenian,

14

are inconsistent with the younger age of the Saghro Group. Moreover, we note that in the

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western Saghro massif, plutonic rocks previously considered to be Cryogenian yielded

16

Ediacaran ages (Walsh et al., 2012), such as the Bouskour granite (570 ± 5 Ma) and the

17

Wizergane granodiorite (576 ± 5 Ma). Hence, the presence of Cryogenian granitoids in the

18

Saghro Group is a question we address in this work.

19 20

In this work, we present new zircon U–Pb radiometric age data, obtained by the Sensitive

21

High Resolution Mass Spectrometry (SHRIMP) method, for plutonic rocks that occur in the

22

Imiter inlier. These new ages directly constrain the timing of magmatism in the eastern Anti-

23

Atlas during the Ediacaran epoch.

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2. Geological setting

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The Anti-Atlas belt consists of two contrasting domains occurring on both sides of the Anti-

28

Atlas Major Fault (AAMF; Choubert, 1947) (Fig. 1).

29

(i) In the southwestern cratonic domain, several inliers expose a Paleoproterozoic basement,

30

which consists of siliciclastic sedimentary sequences, recrystallized under low-grade

31

metamorphic conditions during the Eburnean orogeny (Aït Malek et al., 1998; Thomas et al.,

32

2002; Gasquet et al., 2004; Soulaimani et al., 2014 Blein et al., 2014), and intruded by syn- to

33

late-kinematic granitoids that induced thermal metamorphic aureoles (Ikenne et al., 1997;

34

Mortaji et al, 2000). 4

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(ii) In the northeastern Pan-African mobile domain, the oldest rocks are Cryogenian to Lower

2

Ediacaran; they outcrop in several inliers surrounded by a thick volcaniclastic series

3

belonging to the Upper Ediacaran Ouarzazate Group.

4

Along the AAMF, from the Bou Azzer to the Siroua inliers, complex slices of Cryogenian

5

meta-ophiolites and oceanic arc units were stacked during various orogenic events of the Pan-

6

African cycle (760-600 Ma) (Saquaque et al., 1989; Samson et al., 2004; D’Lemos et al.,

7

2006; Gasquet et al., 2008; El Hadi et al., 2010; Hefferan et al., 2014; Blein et al., 2014).

8 9

The basements of the Anti-Atlas, unconformably overlain by Proterozoic rocks of the Anti-

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Atlas are sub-divided into two lithostratigraphic assemblages: the Anti-Atlas and Ouarzazate

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Supergroups. The magmatic rocks in the Ouarzazate Group consist of calc-alkaline

12

(Taouzzakt and Bou Teglimt) and high-K calc-alkaline (Oussilkane, Igoudrane, Arharrhitz,

13

Bou Gafer) plutonic to subvolcanic intrusions, which are partly intrusive in the widespread

14

Ouarzazate Group series. The Taouzzakt granodiorite has been dated at 572 ± 5 Ma and the

15

associated Takhatert Rhyolite at 550 ± 3 Ma (SIMS U-Pb zircon data) (Cheilletz et al., 2002).

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The Imiter epithermal Ag–Hg deposit, hosted in black shales and volcanic rocks of Middle

17

and Late Neoproterozoic age, is genetically related to the 550 Ma rhyolitic domes and dikes

18

(Levresse, 2001; Cheilletz et al., 2002; Levresse et al., 2004). This late-orogenic context

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evolved into a rift setting during the Late Ediacaran to Cambrian transition (Buggisch and

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Sieger, 1988; Piqué et al., 1999; Benssaou and Hamoumi, 2003; Soulaimani et al., 2014). In

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the Imiter area, deposition of the Ouarzazate group series was controlled by both ENE

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sinistral strike slip faults (El Boukhari et al., 2007; Malusà et al., 2007; Massironi and

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Moratti, 2007) and E-trending fault systems (Ouguir et al., 1996; Cheilletz et al., 2002;

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Levresse et al., 2004). These fractures served as hydrothermal conduits leading to the world-

25

class Imiter Ag-Hg deposits (Gaouzi et al., 2011).

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3. Petrography

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Four petrographic units belonging to three granitoid massifs of the Imiter Inlier were selected

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for SHRIMP dating (Fig. 2). Field data, mode of occurrences and petrography of these

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different granitoids are reported in Baidada et al. (2017). In this paper, we focus on the

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description of the analyzed samples:

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(1) Two samples were collected in the Igoudrane massif. Sample IGO-20 (quartz diorite;

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GPS: N 31, 365596; W 5, 669578) consists of sericitized plagioclase, small interstitial quartz 5

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grains, abundant biotite and green hornblende; epidote and chlorite are secondary phases.

2

Sample IGO-23 (granodiorite; GPS: N 31, 36083; W 5, 695086) collected in the western part

3

of the massif, consists of quartz, plagioclase, K-feldspar, amphibole, biotite and opaque;

4

zircon and apatite are the accessory phases (Fig. 3C and D).

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(2) One sample has been sampled in the Bou Teglimt intrusion. The sample BT-3 (GPS: N

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31,317406; W 5,721142) is a mesocratic porphyritic granodiorite comprised of large biotite

7

crystals (up to 3 cm in length) within a matrix of quartz, plagioclase, K-feldspar, biotite,

8

amphibole, and secondary chlorite, epidote and sericite (Fig. 3B).

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(3) One granite sample GB-1 (GPS: N 31, 315094; W 5, 731944) has been collected in the

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Bou Fliou intrusion. It consists of a leucocratic, medium- to coarse-grained rock composed of

12

quartz, alkali feldspar, plagioclase, biotite, zircon, apatite and opaque minerals (Fig. 3A).

13 14

4. SHRIMP U–Pb zircon data

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4.1. Analytical methods

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Zircon grains were separated by panning, first in water and then in ethanol. The concentrate

19

was purified by hand picking. About 20–35 zircons grains of each sample plus several grains

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of the TEMORA-1 standard (for isotope ratios; Black et al., 2003), one grain of the SL13

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zircon standard (for U concentration, Claoué-Long et al., 1995), plus a few grain of the REG

22

zircon (plenty of common lead, for calibrating the masses) were cast in a 3.5 cm diameter

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epoxy mount (megamount), polished and documented using optical (reflected and transmitted

24

light) and scanning electron microscopy (secondary electrons an cathodoluminescence). After

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extensive cleaning and drying, mounts were coated with ultra-pure gold (8–10 nm thick).

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Zircons were analyzed by the sensitive high-resolution ion microprobe (SHRIMP) at the

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IBERSIMS laboratory, Granada University (Spain). Each selected spot was rastered with the

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primary beam for 120 s prior to the analysis, and then analyzed 6 scans, following the isotope

29

peak sequence 196Zr2O, 204Pb, 204.1background, 206Pb, 207Pb, 208Pb, 238U, 248ThO, 254UO. Every

30

mass in every scan is measured sequentially 10 times with the following total counting times

31

per scan: 2 s for mass 196; 5 s for masses 238, 248, and 254; 15 s for masses 204, 206, and

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208; and 20 s for mass 207. The primary beam, composed of 16O16O+, is set to an intensity of

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about 5 nA, with a 120 μm Kohler aperture, which generates 17 × 20 micron elliptical spots

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on the target. The secondary beam exit slit is fixed at 80 μm, achieving a resolution of about 6

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5000 at 1% peak height. Further details on calibration and data reduction procedures are

2

found on the IBERSIMS Web site

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(http://www.ugr.es/~ibersims/ibersims/Zircon_U_Pb_analysis_files/SHRIMP_geocron_meth

4

od.pdf).

5 6

4.2. Analytical results

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Zircon grains separated from all granitoids correspond to small (50-200 μm), prismatic or

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acicular, euhedral crystals. Under the cathodoluminescence microscope, they show a regular,

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thin oscillatory zonation (Fig. 4), that may surround inherited cores. These features are

11

suggestive of a magmatic origin. Geochronological data are given in Tables 1, 2 and

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presented in Figs. 5, 6 and 7.

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Twenty-three analyses were obtained on twenty zircon grains (rims and cores) from the

15

sample GB-1 (Bou Fliou granite). The dated zircon grains have Th and U contents of 18–175

16

ppm and 44–935 ppm, respectively; Th/U ratios range between 0.19 and 0.51, indicative of a

17

magmatic origin. All analyses are concordant or nearly concordant, with the exception of one

18

discordant point, which may be attributed to partial loss of radiogenic Pb (Fig. 5a) and has not

19

been taken into account for age calculation. These data yield a 206Pb/238U weighted mean date

20

of 582 ± 6 Ma (MSWD = 0.9, n = 22), interpreted as the age of magma emplacement and

21

crystallization.

22 23

Thirty-two analyses were carried out on thirty zircon grains from the sample BT-3 (Bou

24

Teglimt granodiorite). One analysis of an inherited core, with U and Th contents of 97.3 and

25

0.3 ppm respectively, yielded a concordant age of 2960 Ma (Fig. 5b). The other 29

26

concordant analyses show Th and U contents of 18–200 ppm and 77–288 ppm, respectively,

27

with Th/U ratios of 0.14–0.86. These data yield a mean concordant date of 567 ± 6 Ma

28

(MSWD = 1.8, n = 29) (Fig. 5b), interpreted as the age of emplacement of the granodiorite.

29 30

A total of 53 spots were analyzed on 31 zircons from the Igoudrane granodiorite sample IGO-

31

23. Their Th and U contents are 277–1428 ppm and 20–1185 ppm, respectively; their Th/U

32

ratios range from 0.11 to 1.42. Most analyses are concordant (Fig. 6) and yield a date of 575 ±

33

10 Ma (MSWD = 2.4, n = 38) interpreted as the age of emplacement of the granodiorite. A

34

few older ages were obtained from inherited cores, one being concordant at 2450 Ma (Fig. 6). 7

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A total of 32 spots were analyzed on 25 zircons from the Igoudrane quartz diorite sample

3

IGO-20. The zircon grains have Th and U contents of 24–64 ppm and 48–417 ppm,

4

respectively; and Th/U ratios between 0.14 and 0.62. Apart from a few old ages obtained from

5

inherited cores (Fig. 7a), the other analyses show a bimodal distribution (Fig. 7b), the two

6

principal populations yielding 206Pb/238U dates of 538 ± 6 Ma (MSWD = 0.4, n = 13) and 587

7

± 6 Ma (MSWD = 0.7, n = 14). The significance of this bimodal age distribution will be

8

discussed below.

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5. Nd isotopic compositions

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Sm-Nd isotopic data from Baidada et al. (2017) have been reassessed based on the new zircon

13

U–Pb ages (Table 2). The εNd(t) values range from -3.85 to -4.47 for the Bou Fliou granite,

14

from -3.12 to -3.42 for the Bou Teglimt granodiorite, from -2.33 to -2.35 for the Igoudrane

15

granodiorite, and from -2.45 to -0.21 for the Igoudrane quartz-diorite. TDM model ages range

16

from 1.04 to 1.82 Ga. As formerly suggested (Baidada et al., 2017), these data indicate a

17

mixture of mantle and crust sources, with a decreasing proportion of crustal components from

18

the older rocks (Bou Fliou granite) to the younger ones (Igoudrane quartz diorite).

19 20

6. Discussion

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6.1. Ediacaran Magmatism

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According to the new zircon U–Pb ages obtained in this work, the emplacement ages of the

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Imiter granitoids are all younger than 600 Ma (i.e. Ediacaran), with a significantly younger

26

age for the Igoudrane Complex than previously reported (Schiavo et al., 2007). The two dates

27

obtained on the Igoudrane quartz-diorite are more difficult to interpret. A plausible

28

interpretation is that the younger date (538 ± 6 Ma) represents the age of magma emplacement

29

and crystallization, whereas the older date (587 ± 6 Ma) could represent a zircon fraction

30

inherited from the surroundings, and possibly from the Bou Fliou granite dated at 582 ± 6 Ma.

31

The age of 567 ± 6 Ma we obtained on the Bou Teglimt granodiorite is similar within

32

analytical error to the age of 576 ± 5 Ma obtained by De Wall et al. (2001).

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Our radiometric ages of the Imiter granitoids are similar to the age of the neighboring

2

Taouzzakt granodiorite (573 ± 4 Ma) located to the west of the Imiter inlier (Cheilletz et al.

3

(2002). Moreover, numerous plutonic bodies that have been dated in the Saghro massif

4

(zircon U–Pb, SHRIMP) give ages between 588 and 556 Ma (Walsh et al., 2012).

5

Comparable Ediacaran ages were obtained from several granite bodies and rhyolite dikes, as

6

the Bouskour granite (570 ± 5 Ma), the Wizergane granodiorite (576 ± 5 Ma), the voluminous

7

Isk-n-Alla granite (559 ± 5 Ma), the Tagmout gabbro (556 ± 5 Ma) (Fig.8), and the

8

Bouskour–Sidi Flah (563 ± 7 Ma) and Timijt (562 ± 5 Ma) rhyolitic dyke swarms. On the

9

whole, these data show the existence of an important Ediacaran magmatic episode belonging

10

to the Ouarzazate Group (Table. 4).

11 12

Sm-Nd isotopic data yield negative εNd(t) values (-4.5 to -0.2) and TDM model ages of 1.04 to

13

1.82 Ga. These data indicate the presence of an inherited Paleoproterozoic to Archaean

14

component in some zircon grains of the Bou Teglimt and Igoudrane granodiorites show that

15

generation of the parent magmas involved a Neoproterozoic juvenile contribution and

16

recycling of an older crustal component (El Bahat et al., 2013; Kouyaté et al., 2013; Youbi et

17

al., 2013; Ikenne et al., 2017). These results also confirm the existence of a cratonic basement

18

beneath the eastern Anti-Atlas, implying that the northern border of the West African Craton

19

must be placed further north, as suggested previously (Ennih and Liégeois, 2001; Gasquet et

20

al., 2008).

21 22

6.2. Geodynamic context

23

The tectonic context of the Ediacaran Ouarzazate Gp in the Anti-Atlas is still a matter of debate

24

(see discussion in Soulaimani et al., 2018), although it is well admitted that the Ouarzazate plutonic

25

and volcanic rocks belong to high-K calc-alkaline, to alkaline, and eventually to shoshonitic magmatic

26

series (Gasquet et al., 2005, 2008). Thus, based on discrimination diagrams applied to the

27

geochemistry of the volcanic and plutonic rocks, (Bajja, 1998; El Baghdadi et al., 2003; Walsh et al.,

28

2012) proposed that the Ouarzazate Gp. would be linked to an Andean-type arc. In contrast, most

29

authors defined the Ediacaran magmatism as post-collisional or post-orogenic (Gasquet et al., 2005,

30

2008; Pouclet et al., 2007; Thomas et al., 2002; Toummite et al., 2012; Belkacim et al., 2017). In other

31

words, the debate is whether Ediacaran magmatism is to be associated with a contemporary

32

subduction or to a previous Pan-African subduction processes.

33

In fact, post-collisional granitic rocks are difficult to categorize in a specific tectonic

34

setting (Pearce 1996, Liégeois et al., 1998). Liégeois et al. (1998) noted that high-K and

9

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shoshonitic calc-alkaline magmatism is a characteristic of post-collisional tectonic environments at

2

the end of orogenic events, with emplacement of A-type granitic rocks. Moreover, recent studies

3

(e.g. Hooper et al., 1995; Marquez et al., 1999; Morris et al., 2000) argue that the calc-

4

alkaline signature of magmas is not systematically linked to contemporary subduction but can

5

be inherited and generated in a non-subduction environment.

6

In this work, all the Imiter Ediacaran granitoids studied, according to the discrimination

7

diagram Zr+Nb+Ce+Y vs. FeO*/MgO (Whalen et al. 1987), occupy I/S type granites field with a

8

tendency to overlap the field of fractionated granites. This feature has already been shown by

9

Walsh et al. (2012) for most of the Ediacaran granitoid and felsic volcanic rocks of the

10

western part of Jbel Saghro inlier (see also Baidada et al., 2017; El Baghdadi et al. 2003;

11

Benziane, 2007). Besides, according to Errami et al., (2009) and Baidada et al. (2017), all the Imiter

12

Ediacaran granitoids show a geochemical signature representing arc-related magmas. In the Imiter

13

inlier, Ikenne et al. (2007) reported that mafic dykes also show volcanic arc geochemical

14

signatures even though they are considered to be associated with Early Cambrian rifting

15

(Benssaou and Hammoumi, 2001; Faik et al., 2001; Soulaimani et al., 2003). In the Sirwa

16

inlier (Central Anti-Atlas), the granitoids and the volcanic rocks of the Tifnoute valley show

17

geochemical arc signatures (Toummite, 2012b; Belkacim et al., 2017).

18

In the light of the above, our data are more in line with the occurrence of a

19

contemporaneous subduction process during the Late Ediacaran in the eastern Anti-Atlas (e.g.

20

Walsh et al., 2012, Hefferan et al., 2014, and Soulaimani and Hefferan, 2017). This

21

geodynamical context involves the plunging of oceanic lithosphere southward beneath the

22

Avalonian-Cadomian arc and the crust of the West African Craton. Two stages are

23

considered, which correspond to the two late stages of Walsh et al. (2012):

24

(1) Formation of a continental volcanic arc (615- 560 Ma): During the ultimate stages

25

of the Pan-African tectonism, the Eastern Anti-Atlas is considered as a continental volcanic

26

arc marked by the development of Ediacaran plutonic and volcanic magmatism, of calc-

27

alkaline nature (Thomas et al., 2002; Gasquet et al., 2005; 2008; Benziane, 2007, Walsh et al.,

28

2012; Blein et al., 2014a and b). Volcanic arc signatures characterize the Saghro massif in

29

general and of the Imiter inlier in particular (Taouzzakt granodiorite, Bou Teglimt

30

granodiorite, Bou Fliou granite and the volcanic series of the Late Neoproterozoic) (Cheilletz

31

et al., 2002, Errami et al., 2009, Walsh et al., 2012; et al., 2017). This period has long been

32

considered post-collisional with respect to the arc – continent collision of the major Pan-

33

African events (760-650 Ma). However, both our data and those of El Baghdadi et al. (2003)

34

and Benziane (2007) favor a model involving southward subduction of oceanic crust beneath 10

ACCEPTED MANUSCRIPT 1

the crust of theWAC, in a setting comparable to an Andean-type active margin (Thompson et

2

al., 1984; Wilson, 1989). In this context, a transpressivesubduction related tectonic event

3

culminatedin the Saghro inlier, with the development of fracture cleavage associated with

4

weak folding and block faulting,referredto as the PA3 by Walsh et al. (2012).

5 6

(2) Evolution from NE–SW transpression to NW–SE transtension (560-540 Ma): According

7

to Walsh et al., (2012) and references therein, the post-tectonic deposits of the upper part of

8

the Ouarzazate Supergroup began at about 560 Ma. The evolution from NE–SW transpression

9

to NW–SE transtension may be related to oblique convergence and eventual departure of the

10

Cadomian crustal fragment to the paleo-west (Walsh et al., 2012). The ages obtained from the

11

Igoudrane massif (quartz dioriteat 538 Ma) and its high-K calc-alkaline affinity are consistent

12

with the hypothesis of Walsh et al. (2012).These authors further suggest that the highly

13

potassic shoshonitic calc-alkaline plutonism and volcanism mark the final stage of the Pan-

14

African Orogeny (PA3) in a post-collisional context related to either modification of the

15

margin of the West African Craton or formation of a continental volcanic arc above a short-

16

lived south-dipping subduction zone. The first metallogenic manifestations appear at the end

17

of this episode in association with the emplacement of the granitoids (Levresse, 2001;

18

Gasquet et al., 2005).

19 20

7. Conclusion

21 22

In this study, we provide new in situ zircon U–Pb ages of the three granitoids of the Imiter

23

inlier: 538 ± 6 and 575 ± 10 Ma for the Igoudrane massif, 567 ± 6 Ma for the Bou Teglimt

24

granodiorite, and 582 ± 6 Ma for the Bou Fliou granite. These data lead us to conclude that:

25

- The Igoudrane Complex, younger than previously reported;

26

- All the granitoids of the Imiter area were emplaced during the Ediacaran, probably in

27

relation to a subduction context;

28

- The presence of inherited zircons of Neoarchean to Paleoproterozoic ages (2500–1900 Ma)

29

confirms the existence of an Eburnean cratonic basement beneath the eastern Anti-Atlas.

30

- the Ediacaran magmatic rocks of the Imiter inlier demonstrate a subduction generated

31

volcanic arc geochemical signature, indicating Pan African orogenic activity continued to the

32

Ediacaran-Cambrian boundary.

33

11

ACCEPTED MANUSCRIPT 1

Acknowledgements. This work was funded by the project “The geological heritage of

2

Saharan provinces and adjacent regions (Bas Drâa and Ifni)” supported by the Academy

3

Hassan II for Science and Technology. It is part of the PhD thesis of Bouchra Baidada.

4

Fernando Bea and Pilar Montero are thanked for their helpful and constructive comments on

5

the geochronological results. The authors also acknowledge the support of the “département

6

de géologie” (FST-Errachidia) and the “département de géologie” (FSSM-Marrakech). This

7

manuscript greatly benefited from comments of Kevin Hefferan and an ‘‘anonymous’’

8

reviewer as reviewers and J.P. Liégeois as associate editor which have greatly contributed to

9

the improvement of this paper.

10 11

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21

ACCEPTED MANUSCRIPT Figure captions Fig. 1. Geological map of the Anti-Atlas belt in the West African Craton (WAC) showing the location of the studied area (modified from Gasquet et al., 2008). Fig. 2. (A) Geological map of the studied area; (B) Enlarged map of the Bou Fliou granite area (modified from Ouguir et al., 1994; Tuduri, 2005). Fig. 3. Field photographs of granitoid samples selected for geochronology: (A) Bou Fliou granite composed of quartz, plagioclase and biotite; (B) Bou Teglimt granodiorite composed of large biotite crystals within a matrix of quartz, plagioclase, biotite and amphibole; (C) Igoudrane granodiorite composed of quartz, plagioclase, K-feldspar, amphibole and biotite; and (D) Igoudrane quartz diorite composed of plagioclase, quartz, abundant biotite and green hornblende Fig. 4. Cathodoluminescence (CL) images of selected analyzed zircon grains. Analytical spots indicated by red circles, with corresponding 206Pb/238U ages.

Fig. 5. SHRIMP U–Pb Concordia diagrams and weighted ages for samples GB-1 and BT-3. Common lead uncorrected. All red and grey spots localized far from the cluster are excluded from age calculation. Fig.6. SHRIMP U–Pb Concordia diagrams and weighted ages for samples IGO-23. Common lead uncorrected.

206Pb/238U

Concordia age calculated for data with discordance < 5 %. All red spots

localized far from the cluster are excluded from age calculation. Fig.7. (a) SHRIMP U–Pb Concordia diagrams and weighted ages for samples IGO-20. Common lead uncorrected. 206Pb/238U Concordia age calculated for data with discordance < 5 %. (b) Density plot for concordant 206Pb/238U ages; interval = 10 Ma. All red spots localized far from the cluster are excluded from age calculation.

Fig. 8. Simplified geologic map of a nine-quadrangle area in the central part of the Jebel Saghro inlier and in the northern part of the Bou Azzer–El Graara inlier, showing available U–Pb zircon ages

22

ACCEPTED MANUSCRIPT (Geology of the three unmapped sheets is simplified from the 1:1,000,000 Geologic Map of Morocco (Maroc Service Géologique, 1985; Walsh et al, 2012).

Table captions Table.1 Zircon U/Pb isotope composition of Bou Fliou granite (GB-1) and Bou Teglimt granodiorite (BT-3) Errors are at one sigma level (1σ) Table.2 Zircon U/Pb isotope composition of Igoudrane granodiorite (IGO-23) and Igoudrane quartz diorite (IGO-20). Errors are at one sigma level (1σ) Table. 3 Sm–Nd isotopic data for the studied granitoids samples of the Imiter inlier with Nd(t) and TDM recalculated according to the new U–Pb ages obtained in this study. Table. 4 The ages (U / Pb on zircons) of the different granitoids and volcanic rocks in the Saghro massif.

23

ACCEPTED MANUSCRIPT Highlights: - We provide new zircon ages for the granitoids of the Imiter inlier (Saghro, Eastern AntiAtlas), - The crystallization age of the Igoudrane massif (575 ± 10 Ma) is younger than previously thought, - The granitoids in the Imiter inlier are Ediacaran to Lower Cambrian in age (538– 582 Ma), - An Archean to Paleoproterozoic basement is present under the Eastern Anti-Atlas,

Table.1 Zircon U/Pb isotope composition of Bou Fliou granite (GB-1) and Bou Teglimt granodiorite (BT-3) Errors are at one sigma level (1σ) Samples

U (ppm)

Th (ppm)

Th/U

Pb207/Pb206

±err

Pb207/U235

±err

Pb206/U238

±err

Pb207/Pb206

±err

Pb207/U235

±err

Pb206/U238

±err

Discord %

Age (Ma)

Isotope ratios

Bou Fliou granite GB-1. 1.1

172.3

86

0.51

0.0559

0.00056

0.76435

0.01497

0.09917

0.00163

448.5

22

576.5

8.6

609.5

9.6

-2.0

GB-1. 10.1

144.2

35.8

0.25

0.05965

0.00171

0.79256

0.02638

0.09636

0.0016

591.1

60.8

592.6

15

593

9.4

-2.6

GB-1. 11.1

68.9

20.3

0.3

0.05164

0.0016

0.65285

0.03261

0.0917

0.00357

269.3

69.8

510.2

20.2

565.6

21.2

-2.0

GB-1. 12.1

141.7

65.6

0.48

0.05828

0.00074

0.75011

0.01301

0.09334

0.00105

540.3

27.6

568.3

7.6

575.3

6.2

-2.4

GB-1. 13.1

99.5

42.6

0.44

0.05896

0.00296

0.74797

0.04

0.09201

0.00165

565.7

105.8

567

23.5

567.4

9.7

0.0

GB-1. 14.1

59.4

19.7

0.34

0.0571

0.0033

0.74262

0.04683

0.09433

0.00235

495.3

122.6

563.9

27.6

581.1

13.9

-5.6

GB-1. 15.1

59.8

18.8

0.32

0.06108

0.00261

0.79835

0.04338

0.0948

0.00316

642.1

89.4

595.9

24.8

583.8

18.6

1.8

GB-1. 16.1

81.8

34.5

0.43

0.05645

0.00186

0.71229

0.0304

0.09152

0.00245

469.9

71.4

546.1

18.2

564.5

14.5

-1.0

GB-1. 17.1

98.7

39.7

0.41

0.05908

0.00185

0.76931

0.02562

0.09444

0.00104

570.1

66.6

579.4

14.8

581.7

6.1

-0.6

GB-1. 18.1

79.8

34.8

0.45

0.05901

0.00113

0.76259

0.02009

0.09372

0.00166

567.5

41.2

575.5

11.6

577.5

9.8

-2.0

GB-1. 19.1

674.6

131.6

0.2

0.05776

0.00033

0.72892

0.01376

0.09153

0.00161

520.7

12.4

555.9

8.1

564.6

9.5

-1.4

GB-1. 19.2

44.4

15.6

0.36

0.05731

0.00247

0.73525

0.04191

0.09304

0.00345

503.5

92.2

559.6

24.8

573.5

20.4

0.2

GB-1. 2.1

935

175.8

0.19

0.06113

0.00039

0.60948

0.05583

0.07231

0.0066

643.9

13.6

483.2

35.8

450.1

39.9

2.8

GB-1. 2.2

60

20.5

0.35

0.05584

0.00366

0.73618

0.05516

0.09561

0.00345

446.1

139.6

560.2

32.8

588.6

20.3

-2.6

GB-1. 20.1

115.9

29

0.26

0.05478

0.00066

0.69384

0.02

0.09186

0.00238

403.5

26.6

535.1

12.1

566.5

14.1

-2.6

GB-1. 3.1

90.5

36.5

0.41

0.05719

0.00289

0.73739

0.04675

0.09351

0.00355

499.1

107.6

560.9

27.7

576.2

20.9

-1.6-

GB-1. 4.1

67.8

26.2

0.4

0.06074

0.00275

0.78376

0.05266

0.09359

0.00464

629.9

94.6

587.6

30.4

576.7

27.3

5.2

GB-1. 5.1

67.2

25.5

0.39

0.06049

0.0038

0.80997

0.05385

0.09711

0.00211

621.3

129.8

602.4

30.6

597.4

12.3

-1.4

GB-1. 6.1

61.3

19.8

0.33

0.05797

0.00167

0.75869

0.03641

0.09491

0.00363

528.9

61.6

573.3

21.3

584.5

21.4

-1.0

GB-1. 7.1

152.8

34.4

0.23

0.06035

0.00164

0.822

0.02556

0.09878

0.00146

616.1

57.6

609.2

14.4

607.3

8.6

-2.4

GB-1. 7.2

137.1

35.3

0.26

0.0564

0.00105

0.71327

0.02473

0.09172

0.00266

468.1

40.8

546.7

14.8

565.7

15.7

-2.4

GB-1. 8.1

69

30.2

0.45

0.05669

0.00231

0.71061

0.04322

0.09091

0.0041

479.5

87.6

545.1

26

560.9

24.2

-1.0

GB-1. 9.1

52.2

19

0.37

0.0535

0.00233

0.71206

0.03641

0.09653

0.00257

349.9

95.6

546

21.9

594.1

15.2

-2.8

Bou Teglimt granodiorite BT-3-1.1

170.7

77.3

0.46

0.05854

0.00059

0.7201

0.01598

0.08921

0.00173

550.3

21.8

550.7

9.5

550.8

10.2

2.0

BT-3-10.1

243.4

33.3

0.14

0.05961

0.0009

0.81239

0.02865

0.09884

0.00313

589.5

32.6

603.8

16.2

607.6

18.4

0.0

BT-3-11.1

130.3

30.3

0.24

0.05627

0.00069

0.6833

0.02642

0.08807

0.00322

463.1

26.8

528.8

16.1

544.1

19.1

-4.0

BT-3-12.1

152

32.3

0.22

0.06529

0.00193

0.83311

0.0326

0.09254

0.00234

783.9

61

615.3

18.2

570.5

13.8

-0.4

BT-3-13.1

88.2

27.1

0.32

0.06042

0.00198

0.74494

0.03551

0.08942

0.00308

618.7

69

565.3

20.9

552.1

18.2

1.4

BT-3-14.1

122.2

32.9

0.28

0.05526

0.00087

0.72756

0.02007

0.09549

0.00213

422.7

34.8

555.1

11.8

588

12.6

-5.0

BT-3-15.1

151.8

54.6

0.37

0.06031

0.0008

0.73984

0.02242

0.08897

0.0024

614.7

28.4

562.3

13.2

549.5

14.3

0.8

BT-3-16.1

86.9

23.3

0.28

0.05757

0.00094

0.75007

0.01673

0.09449

0.0014

513.5

35.4

568.3

9.8

582.1

8.3

-1.8

BT-3-16.2

239.5

200.8

0.86

0.06017

0.00066

0.80294

0.02811

0.09678

0.0032

609.7

23.6

598.5

16

595.5

18.8

4.0

BT-3-17.1

148.3

63.6

0.44

0.05874

0.00079

0.76913

0.02098

0.09496

0.00223

557.5

29.2

579.3

12.1

584.8

13.1

-1.2

BT-3-18.1

77

18.1

0.24

0.05852

0.0012

0.76099

0.01846

0.09431

0.00118

549.5

44

574.6

10.7

580.9

6.9

-2.2

BT-3-19.1

237.5

72.5

0.31

0.05873

0.00063

0.75071

0.01824

0.09271

0.00199

557.1

23.2

568.6

10.6

571.5

11.7

-0.4

BT-3-2.1

97.3

27.5

0.29

0.21926

0.00471

17.60998

0.67751

0.58249

0.01847

2975.3

34.2

2968.7

37.7

2958.9

75.7

0.6

BT-3-20.1

143.2

39.1

0.28

0.05951

0.00034

0.74828

0.01284

0.0912

0.00144

585.7

12.4

567.2

7.5

562.6

8.4

0.4

BT-3-21.1

80.8

32

0.41

0.05885

0.00116

0.76007

0.01907

0.09367

0.00141

561.7

42.4

574.1

11.1

577.2

8.3

-2.6

BT-3-22.1

80.3

20.8

0.27

0.06169

0.00168

0.76722

0.03505

0.0902

0.00329

663.3

57.6

578.2

20.4

556.7

19.5

3.4

BT-3-23.1

210.2

95.4

0.47

0.06046

0.00091

0.77928

0.02887

0.09349

0.00314

619.9

32.2

585.1

16.6

576.1

18.5

-0.8

BT-3-24.1

117.8

27.2

0.24

0.06019

0.00131

0.75952

0.02045

0.09152

0.0014

610.3

46.6

573.7

11.8

564.5

8.3

-1.2

BT-3-25.1

183.2

87.2

0.49

0.05955

0.00068

0.77386

0.0334

0.09425

0.00391

587.3

24.6

582

19.3

580.6

23.1

1.4

BT-3-26.1

145.7

32.2

0.23

0.05781

0.00106

0.76118

0.02795

0.09549

0.00302

522.7

39.6

574.7

16.3

587.9

17.7

-0.8

BT-3-27.1

127.7

30.9

0.25

0.05898

0.00112

0.66874

0.03368

0.08223

0.00382

566.3

41

519.9

20.7

509.4

22.8

1.6

BT-3-28.1

178.8

38.6

0.22

0.06101

0.00156

0.6503

0.02726

0.0773

0.00256

639.7

53.8

508.7

17

480

15.3

0.8

BT-3-29.1

174.8

64.9

0.38

0.05838

0.00068

0.70243

0.0157

0.08726

0.00163

544.1

25.4

540.2

9.4

539.3

9.7

0..2

BT-3-3.1

210.8

69.6

0.34

0.05922

0.00087

0.74512

0.01582

0.09126

0.00135

575.1

31.8

565.4

9.3

563

8

-0.8

BT-3-30.1

204.9

111

0.56

0.0587

0.00097

0.74437

0.044

0.09196

0.00521

556.1

35.6

565

26

567.1

30.8

3.4

BT-3-4.1

152.3

40.7

0.27

0.05775

0.00129

0.70429

0.02504

0.08845

0.00243

520.3

48.2

541.3

15

546.4

14.5

-2.4

BT-3-5.1

138.4

29.7

0.22

0.05659

0.0014

0.69671

0.02709

0.08929

0.00266

475.7

53.8

536.8

16.3

551.3

15.7

-0.2

BT-3-6.1

138.5

48.1

0.36

0.05967

0.00033

0.76463

0.01431

0.09294

0.00163

591.7

12

576.7

8.3

572.9

9.6

0.6

BT-3-7.1

97.6

24

0.25

0.0585

0.00142

0.71712

0.02587

0.08891

0.00235

548.3

52.4

549

15.4

549.1

13.9

-2.0

BT-3-7.2

288

89.1

0.32

0.05955

0.00073

0.76598

0.01386

0.09328

0.00119

587.5

26.4

577.5

8

574.9

7

-1.0

BT-3-8.1

156.6

52.6

0.34

0.06017

0.00096

0.77281

0.02212

0.09315

0.00219

609.7

34.2

581.4

12.8

574.1

12.9

-0.6

BT-3-9.1

192.2

140.5

0.75

0.05942

0.00108

0.74853

0.02187

0.09137

0.00207

582.5

38.8

567.4

12.8

563.6

12.2

2.0

Table.2 Zircon U/Pb isotope composition of Igoudrane granodiorite (IGO-23) and Igoudrane quartz diorite (IGO-20). Errors are at one sigma level (1σ) Samples

U (ppm)

Th (ppm)

Th/U

Pb207/Pb206

±err

Pb207/U235

±err

Pb206/U238

±err

Pb207/Pb206

±err

Isotope ratios

Pb207/U235

±err

Pb206/U238

±err

Discord %

535.5

11.4

-1.0

Age (Ma)

Igoudrane granodiorite IGO-23-1.1

438.58118 164.14767 0.38394916

0,05578

0,00030 0.66613221 0.01541411 0.08661743 0.00192362

518.40002

9.5

IGO-23-1.2

61.384216

44.63689

0.7459783

0,05889

0,00151 0.74975675 0.02255734 0.09233017 0.00141039 563.29999 54.799999 568.09998

13.2

IGO-23-10.1

743.93945

92.78743

0.12795007

0,05828

0,00024 0.74049878 0.01163907 0.09214831

IGO23-10.2

146.54666 34.973789 0.24482498

0,05894

0,00076 0.77657783 0.01363224 0.09555227 0.00108307 565.09998 27.799999

IGO-23-11.1

213.83253 56.382095 0.27049324

0,05994

0,00068 0.76942307 0.01313749 0.09310445 0.00113744 601.29999

24.4

579.40002

IGO-23-12.1

713.08752

84.22541

0.12116838

0,05816

0,00024 0.74724346 0.01481245 0.09318797 0.00177581 535.70001

9,0

566.59998 8.6000004 574.40002

IGO-23-12.2

186.1721

164.48837 0.90637845

0,05709

0,00065 0.73637253 0.01196285 0.09355276 0.00103008 494.89999

25,0

560.29999

IGO-23-13.1

354.62491 51.290489 0.14837357

0,05752

0,00040 0.73776329 0.01376555

15.2

IGO-23-13.2

192.46228 85.739136 0.45700657

0,06820

0,00069

IGO-23-14.1

274.95801 33.455971 0.12482347

IGO-23-14.2

540.29999

12,0

9,0

562.70001 6.8000002 568.20001 583.5

8,0

7.8000002 588.29999 6.4000001 7.5

573.90002 6.6999998

-0.6 -1.0 0.0 -0.4 -2.0

6.0999999

1.4

561.09998 8.1000004 573.40002 9.3000002

-0.8

20.799999 903.79999 9.1000004 915.90002 9.1999998

-2.0

511.5

0.02183629 0.15265895 0.00164315

874.5

0,05674

0,00060 0.74741036 0.01144193 0.09553415 0.00099176

481.5

115.05006 99.564705 0.88778448

0,05665

0,00123 0.76787519 0.02058854 0.09830825 0.00150996 477.89999 47.200001

IGO-23-15.1

561.82568 102.70641 0.18753611

0,05596

0,00037 0.55297583 0.00530379 0.07167085 0.00042495 450.70001

IGO-23-15.2

79.172462 52.092705

0.6749813

0,05592

0,00190 0.80514711 0.03077014 0.10442863

IGO-23-16.1

332.7851

53.670036 0.16544627

0,05767

0,00038 0.73541307 0.00814184 0.09248653 0.00074733 517.29999

0.0017802

569.29999 8.3000002

10.5

0.00157703

1.4354397

0.0930234

0.0013575

443.5

23.4

14.6

576.5

566.70001 6.5999999 588.20001 5.9000001 578.5

11.9

604.5

446.89999 3.4000001 446.20001

449.10001 73.800003 599.70001 14.4

7,0

17.4

640.29999

-2.8

8.8999996

-1.8

2.5

1.8

10.4

2.8

559.70001 4.6999998 570.20001 4.4000001

-1.2

IGO-23-16.2

22.005051 20.595795 0.96016341

0,06160

0,00373

0.26425752 0.13335131 0.03004435 660.29999

124.6

769,0

134.3

807,0

173.2

10.6

IGO-23-16.3

269.2674

66.940651 0.25503227

0,05700

0,00049 0.72901881 0.02054104 0.09276767 0.00246628 491.29999

19,0

556,0

12.2

571.90002

14.6

-2.2

IGO-23-16B.1 442.00131 55.243412 0.12821709

0,05732

0,00028 0.72302377 0.02466766 0.09148949 0.00307179 503.70001

10.8

552.5

14.7

564.29999

18.1

-1.0

1.1325855

IGO-23-17.1

532.11694 62.747177 0.12096955

0,05696

0,00034 0.74173349 0.01757127 0.09443794 0.00213863 490.10001

13.2

563.40002

10.3

581.70001

12.6

-1.8

IGO-23-17.2

156.93701 35.168888 0.22989112

0,05696

0,00077 0.73714417 0.01945311 0.09386609 0.00210514 489.89999

29.4

560.70001

11.4

578.40002

12.5

-0.8

IGO-23-18.1

201.97925 60.606087 0.30782115

0,05680

0,00067 0.73344481 0.02380336 0.09365346 0.00281088 483.70001

26,0

558.59998

14.1

577.09998

16.6

-1.2

IGO-23-19.1

114.94692 83.225082 0.74275547

0,06617

0,00053

0.05787544 0.12411213 0.00624871 811.70001 16.799999 768.79999

27.9

754.20001 35.900002

IGO-23-2.1

212.09399 42.986332 0.20791747

0,05580

0,00090 0.70307457 0.01711508 0.09138134 0.00163605

10.2

563.70001 9.6999998

1.1322867

444.5

35.400002 540.59998

-2.8 0.2

1.4194522

0,05749

0,00172 0.73310274 0.03361148 0.09249239 0.00320169 510.29999 64.199997 558.40002

19.9

570.29999

19,0

-10.4

24.492119 0.16867359

0,05710

0,00127 0.73825687 0.02639603 0.09376314 0.00260831

495.5

48.200001 561.40002

15.5

577.79999

15.4

-1.2

IGO-23-22.1

243.25687 38.791721 0.16359232

0,05708

0,00049 0.76130891 0.01296354

494.5

18.799999 574.79999

7.5

595.29999 8.1000004

IGO-23-23.1

194.54201 53.660828 0.28296515

0,05686

0,00044 0.74076849 0.01976934 0.09448718 0.00239048 486.10001

17,0

562.90002

IGO-23-24.1

302.38834 46.352077

0,05987

0,00068 0.74204803 0.01483509 0.08989664 0.00144794 598.70001

24.4

563.59998 8.6999998 554.90002

IGO-23-20.1

111.82587 154.72986

IGO-23-21.1

148.9595

0.1572509

0.096741

0.0013762

11.6

582,0

-1.2

14.1

-3.4

8.5

0.6

25.700001

2132.3

37.799999

13.4

0.01946597 0.08403516 0.00216123 554.90002 26.200001 526.70001

11.9

520.20001

12.9

1.0

0.01110439 0.09036879 0.00124664 550.09998

556.20001

6.5

557.70001 7.4000001

5.2

0.00323333 565.70001 9.3999996 572.90002

15.5

574.70001

0.0

534.79999

13.4

542.20001 7.1999998

3.2

46,0

512.40002

13.4

496.70001

1.6

11.4

584.29999

14.6

580.40002 17.799999

0.4

0.00077686 561.70001

10.8

554.5

4.5

552.79999 4.5999999

7.6

0,05937

0,00032 0.71367407 0.01251415 0.08717671 0.00141915 580.90002

11.6

546.90002 7.4000001 538.79999 8.3999996

2.2

326.35043 36.502468 0.11474322

0,05653

0,00068 0.73263717 0.01907982 0.09399747 0.00214537 473.29999 26.200001 558.09998

11.2

579.09998

12.6

-2.6

IGO-23-3.2

150.88242 27.863773

0.1894481

0,05788

0,00087 0.75754428 0.01472371 0.09491663 0.00111075

8.5

584.5

6.5

-1.2

IGO-23-30.1

233.78363 36.588741 0.16055444

0,05993

0,00053 0.73241043 0.01384807 0.08863208 0.00144682 601.09998

19,0

558,0

8.5

2.8

IGO-23-31.1

256.36404 34.436874 0.13780202

0,06031

0,00063 0.79274553 0.02755812 0.09533226 0.00314262 614.70001

22.4

592.70001

18.5

1.2

IGO-23-31.2

179.64691 52.766373 0.30131897

0,05844

0,00094 0.67632288

IGO-23-4.1

334.37735

0.15612653

0,05858

0,00034 0.73141873 0.01345269 0.09054934 0.00154844 551.70001

IGO-23-4.2

726.89648 1185.0453

1.672443

0,05878

0,00035 0.77490669

IGO-23-5.1

457.63095

0.12924382

IGO-23-5.2

IGO-23-24.2

118.09701 80.231323

0.6969378

0,18925

0,00332

10.229697

0.2802701

IGO-23-25.1

171.23013

26.17053

0.15679106

0,05867

0,00071

0.6798293

IGO-23-25.2

601.13422 434.80072

0.7420066

0,05854

0,00031

0.7294482

IGO-23-26.1

795.54852 81.602211 0.10522629

0,05896

0,00026 0.75802875 0.02663245

0.0932451

IGO-23-26.2

80.109795 56.674072 0.72575122

0,05730

0,00164 0.69327813

0.022211

0.08775114 0.00121147 503.10001

62,0

IGO-23-27.1

372.44766 196.33777 0.54078865

0,05943

0,00128 0.65634787

0.0216579

0.08010487 0.00198659 582.70001

IGO-23-28.1

252.23225 31.592953 0.12849274

0,05989

0,00032 0.77801013 0.02551981 0.09421834 0.00303127

IGO-23-28.2

290.70584 230.08493

0,05885

0,00029 0.72656637 0.00773135

IGO-23-29.1

286.10629 40.667103 0.14581586

IGO-23-3.1

0.811939

0.39203766 0.00813506

0.0895348

2735.7

599.5

525.5

28.4

11.6

2455.8

32.599998 572.59998

8.1999998 547.40002 15.7

587,0

19.1

11.8

9.3999996 519.59998 7.9000001

-0.8

12.4

557.40002 7.9000001 558.79999 9.1999998

1.8

0.09561297 0.00128865 558.90002

12.8

582.59998 6.8000002 588.59998

1.6

0,05876

0,00049 0.79238921 0.01104108 0.09780976 0.00103817 558.09998

18,0

201.49777 143.15477 0.72882718

0,05927

0,00062 0.79476821 0.01724551 0.09724826 0.00181706 577.09998

22.6

IGO-23-6.1

248.02892 30.918865 0.12788223

0,05840

0,00052 0.78381824 0.01881361 0.09733959 0.00214427 544.90002 19.200001 587.70001

10.8

IGO-23-6.2

651.01715 353.66663 0.55730206

0,07216

0,00018

14.8

50.88908

57.6549

82.76696

1.6221459

0.015484

0.0117302

0.08394099 0.00133338 546.09998 34.799999

524.5

592.5

6.1999998 601.59998 6.0999999

0.2

598.79999

12.6

-1.4

973.70001

20.9

0.2

11.7

-1.4

615.79999

12.9

-0.6

566.79999 8.3999996 576.79999

10,0

1.2

IGO-23-7.1

704.59015

0.1205062

0,05922

0,00026 0.73789853

IGO-23-7.2

171.86244 101.32413 0.60481274

0,05884

0,00079 0.81323791 0.02115076 0.10023995 0.00219967 561.09998 29.200001 604.29999

IGO-23-8.1

464.9101

60.791386 0.13414116

0,05792

0,00032 0.74748951 0.01438135 0.09359907

IGO-23-8.2

56.658859

44.14259

0.79924321

0,16056

0,00078

IGO2-3-9.1

468.26407

68.00145

0.14897601

0,05811

0,00054 0.70877069

0.0139174

IGO-23-9.2

225.68384 44.147213 0.20067433

0,07632

0,00189

0.04060299 0.11819661 0.00248659

1103.5

48.599998 820.59998

18.5

720.20001

0,05555

0,00125 0.63883686 0.04157383 0.08340729 0.00508574

434.5

49.200001 501.60001

26.1

516.40002 30.299999

10.272705

1.2438271

0.09037286 0.00197652 575.09998 9.8000002 561.20001 9.8000002 557.70001

0.0016936

0.15903938 0.46403602 0.00661464 0.0884542

526.70001 2461.5

12,0

8.1999998 2459.6001

0.00149595 534.09998 20.200001

-1.4

10.7

593.90002 9.8000002 598.29999

0.03810829 0.16304538 0.00376282 990.29999 5.1999998 978.79999 0.0166854

7.5

544,0

11.9

2457.3999 29.200001

-5.0

8.3000002 546.40002 8.8999996

-1.4

14.4

14.4

-0.2

Igoudrane quartz diorite IGO20-1.1

181.90628 24.024824 0.13548821

0.4

IGO-20-1.2

114.57558 52.269859 0.46800256

0,11543

0,00054

0.15819998 0.34273013 0.00972925

1886.7

8.3999996

1893.5

25.200001

1899.8

46.900002

-0.8

IGO-20-10.1

155.95726 36.159321 0.23785026

0,05588

0,00085 0.72396803 0.01471357 0.09396604 0.00122336

447.5

33.400002

553,0

8.6999998

579,0

7.3000002

-0.6

IGO-20-11.1

417.41281 56.209682 0.13814473

0,05898

0,00054 0.74878168 0.01710151 0.09207559 0.00189445 566.29999

20,0

567.5

10,0

567.79999

11.2

-1.6

5.4548249

10,0

2.2

594.5

16.799999 602.09998

19.6

-0.8

551,0

36.799999 568.79999 45.799999

238.10974 59.069324 0.25449181

0,05834

0,00049 0.71689051

IGO-20-12.1

174.80499 34.292252

0.2012478

0,05897

0,00084 0.79593372 0.02944955 0.09789395 0.00332138 565.90002 30.799999

IGO-20-13.1

365.34204 60.357292 0.16948023

0,05665

0,00074 0.72048962 0.06111331 0.09223744 0.00772242 478.10001

28.6

IGO-20-13.2

66.176048 28.708536 0.44504014

0,05847

0,00087 0.78775412

32,0

IGO-20-14.1

125.05512 25.546968 0.20956892

0,05645

0,00123 0.74848491 0.02495598 0.09616737 0.00240836 470.10001 47.400002 567.29999

IGO-20-15.1

155.9782

0.27492869

0,05913

0,00054 0.76599789 0.01064008 0.09395651 0.00092373 571.90002

IGO-20-16.1

140.36986 25.849321 0.18891406

0,06133

0,00109 0.75238121 0.01856079 0.08896887 0.00148809 650.90002 37.799999 569.59998

IGO-20-17.1

332.17001 57.147148 0.17649122

0,05816

0,00034 0.76752877 0.02976689 0.09570966 0.00365328 535.90002

0.4375222

0,16237

0,00366

IGO-20-18.1

217.58681 33.502083 0.15795313

0,05997

0,00066 0.72114152 0.01391204 0.08720873 0.00134341 602.70001

IGO-20-19.1

206.76587 34.106659 0.16921906

0,06084

0,00069 0.71321011 0.01946058 0.08501865 0.00208622 633.70001 24.200001 546.70001

IGO-20-19.2

48.571823 13.735045 0.29009128

0,05881

0,00272 0.67175704 0.04749278 0.08283684 0.00442142 560.29999 97.599998 521.79999 29.299999

IGO-20-2.1

263.9953

45.423119 0.17651016

0,05685

0,00063 0.76382411 0.01836903 0.09744087 0.00204674 485.89999

IGO-20-2.2

74.509369 44.833847 0.61728269

0,06630

0,00085

IGO-20-20.1

224.16647 40.271427 0.18429574

0,05939

IGO-20-21.1

219.08081 64.519241 0.30211613

IGO-20-22.1

IGO-20-17.2

106.958

41.8018

45.616756

8.8264723

0.015123

550.29999

IGO-20-11.2

0.0165024

0.08911894 0.00169478 542.70001 18.200001 548.79999

0.09771071 0.00140402

0.25301436 0.39424703 0.00684517

547.5

2480.5

19.6

12.6 37.599998 23.6

601,0

8.3000002

-1.4

591.90002

14.2

-1.4

6.1999998 578.90002

5.5

-0.2

589.90002 9.3999996

577.5

14.6

10.8

549.40002 8.8000002

26.5

551.29999 8.1999998 11.6

0.2

21.5

-1.4

2142.5

31.700001

8.0

539,0

8,0

1.2

526,0

12.4

2.8

513,0

26.299999

-7.4

12,0

-2.6

578.29999 17.200001 589.20001 2320.2

-1.2

576.20001

10.6

599.40002

1.3182641

0.04967311 0.14421232 0.00508221 815.70001 26.799999 853.79999

22,0

868.40002 28.700001

-0.2

0,00078

0.7218442

0.01541068 0.08814923 0.00145462

581.5

28,0

551.79999 9.1999998 544.59998 8.6000004

-1.4

0,05904

0,00041

0.6970343

0.01810811 0.08562727 0.00211924

568.5

15.2

158.63551 31.766792 0.20542908

0,05836

0,00057 0.69333363 0.01668742 0.08616956

IGO-20-3.1

264.46539 44.248825 0.17164132

0,05735

0,00036 0.76387548

0.0198068

0.09659599 0.00240672 505.10001

IGO-20-3.2

174.78325 71.104713 0.41733766

0,25715

0,00057

19.374191

1.0360144

0.54642117 0.02912797

IGO-20-4.1

147.7119

23.457777 0.16291472

0,05755

0,00058 0.69194043

0.0244568

0.08720139 0.00293954 512.70001 21.799999

IGO-20-5.1

230.89627 41.468838 0.18424423

0,05884

0,00061 0.70552659 0.03385613 0.08696268 0.00406269 561.29999

IGO-20-5.2

155.70769 45.787544 0.30166593

0,05746

0,00055

IGO-20-6.1

302.39218 43.286514 0.14684901

0,05791

0,00038 0.79237562 0.01818475 0.09923155

IGO-20-6.2

129.90086 27.476669 0.21699065

0,05769

IGO-20-7.1

251.30295 33.626446 0.13726896

IGO-20-8.1

0.6772722

0.0018706

24.4

9,0

10.9

529.59998

12.6

1.2

10.1

532.79999

11.1

-0.4

576.20001

11.4

594.40002

14.1

-1.2

3.5999999 3060.6001

53,0

2810.3

122.6

8.2

534,0

14.8

539,0

17.5

1.4

542.09998

20.4

537.5

24.1

0.4

537,0

543.09998 21.200001 534.79999

3229.3

13.6

22.4

0.03637406 0.08549236 0.00450801 509.10001 20.799999 525.09998 22.200001 528.79999 26.799999 0.0021527

609.90002

0,00057 0.75874364 0.01197765 0.09538953 0.00111922 517.90002 21.799999 573.29999

7,0

587.29999 6.5999999

-1.2

0,05778

0,00038 0.70091879 0.02129875 0.08797763

12.8

543.59998

1.4

210.49734 37.106083 0.18083706

0,05859

0,00065 0.75750995 0.01556037 0.09377072 0.00158107 551.90002 24.200001 572.59998 9.1000004 577.79999 9.3000002

-0.2

IGO-20-8.2

62.56673

37.587868 0.61630148

0,11179

0,00138

5.1047506

0.19052833 0.33117938 0.01160301

IGO-20-9.1

324.40631 47.592266 0.15049985

0,05851

0,00058

0.7519291

0.01647477 0.09321276 0.00178733 548.70001

521.5

1828.7

14.4

14.4

22.200001 21.6

592.5

539.29999

12.6

-3.4

10.3

0.0025897

526.5

0.4

15.4

32.200001

1844.1

56.400002

-0.4

569.29999 9.6000004

574.5

10.5

-0.4

1836.9

Table. 3 Sm–Nd isotopic data for the studied granitoids samples of the Imiter inlier with Nd(t)and TDM recalculated according to the new U–Pb ages obtained in this study. Sample

Age (Ma)

Nd

Sm

43Nd/144Nd

(ppm)

(ppm)

(measured)

2

147Sm/144Nd

143Nd/144Nd

(t)

Nd(t)

TDM

Bou Teglimt Granodiorite BT-1

567

18.35

4.2

0.512261

0.000006

0.1386

0.511737

-3.15

1792

BT-2

567

18.09

3.83

0.512223

0.000012

0.128

0.5117397

-3.12

1641

BT-3

567

17.98

3.83

0.512211

0.00002

0.129

0.5117245

-3.42

1680

BT-4

567

14.59

3.3

0.512241

0.000008

0.1367

0.5117256

-3.39

1788

Bou Fliou granite GB-1

582

16.25

3.15

0.51213

0.000014

0.1171

0.5117153

-3.85

1590

GB-2

582

16.6

3.21

0.512121

0.000009

0.1169

0.5117

-4.15

1557

GB-3

582

14.57

2.94

0.512136

0.000012

0.1221

0.5116966

-4.24

1677

GB-4

582

19.77

3.61

0.51208

0.000024

0.1105

0.5116822

-4.47

1573

Igoudrane quartz-diorite IGO-12

538

23

4.72

0.512231

0.000012

0.1242

0.5116798

-2.35

1606

IGO-14

538

19.37

4.21

0.51227

0.00001

0.1314

0.511695

-4.02

1824

IGO-16A

538

24.65

5.52

0.512207

0.000008

0.1354

0.5116065

-2.35

1484

IGO-20

538

21.17

4.21

0.512237

0.000012

0.1204

0.5117032

-2.33

1478

Igoudrane granodiorite IGO-22

575

18.68

3.65

0.512221

0.000009

0.1183

0.5116957

-1.95

1540

IGO-23

575

17.2

3.63

0.51227

0.000012

0.1275

0.5117094

-1.91

1606

IGO-24

575

15.19

3.35

0.512299

0.000016

0.1334

0.5117074

-2.45

1617

IGO-26

575

12.96

2.79

0.51226

0.000012

0.1302

0.5116819

-0.21

1037

ACCEPTED MANUSCRIPT Table. 4 The ages (U / Pb on zircons) of the different granitoids and volcanic rocks in the Saghro massif

Bouskour granite Iknioun granodiorite

Saghro Massif

Igoudrane massif

Taouzzakt granodiorite Wizergane granodiorite Bou Fliou granite Bou Teglimt granodiorite Isk'n Alla granite Zouzmitane granite Tagmout Monzogabbros Arharrhitz Pluton Oussilkane Pluton Bouskour Rhyolite Timijt rhyolite Takhatert Rhyolite Jebel n'Habab (Andesite)

Quartz diorite Granodiorite

Age (U/Pb; zircon) 572 570 565 563 538

±

References

5 5 5 6.3

Benziane et al., 2007 Walsh et al., 2012 De Wall et al. 2001 Tuduri et al., 2018 6 This study

575 555 573 576

10 7 4 5

This study De Wall et al., 2001 Cheilletz et al., 2002 Benziane et al., 2007

582 576 567 555 562 559 588 563 571 596 564 562 558 550 570

6 7 6 4 5 5 6 5 22 20 7 5 4 3 7

This study De Wall et al. 2001 This study De Wall et al., 2001 Benziane et al., 2007 Walsh et al., 2012 Benziane et al. 2007 Benziane et al., 2007 Schiavo et al., 2007 Schiavo et al,. 2007 Walsh et al., 2012 Walsh et al., 2012 Benziane et al., 2007 Cheilletz et al., 2002 Hawkins et al., 2001